U.S. patent application number 09/728499 was filed with the patent office on 2003-03-13 for method of pasteurizing, monitoring pu-uptake, controlling pu-up-take and apparatus for pasteurizing.
Invention is credited to Dalum, Kim Christian, Nielsen, Jorgen Tage.
Application Number | 20030049356 09/728499 |
Document ID | / |
Family ID | 26064569 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030049356 |
Kind Code |
A1 |
Nielsen, Jorgen Tage ; et
al. |
March 13, 2003 |
Method of pasteurizing, monitoring PU-uptake, controlling
PU-up-take and apparatus for pasteurizing
Abstract
A continuous flow pasteurization apparatus for a liquid product
includes a pasteurization area divided into plural pasteurization
zones, each with a connection for heating and/or cooling the
product, so that if production stops, it is possible to hold the
temperature below the pasteurizing temperature. Upon restarting,
the product is reheated to a temperature close to the pasteurizing
temperature. The apparatus provides for the control and monitoring
of pasteurization units (PU's).
Inventors: |
Nielsen, Jorgen Tage;
(Hellebaek, DK) ; Dalum, Kim Christian; (Horsholm,
DK) |
Correspondence
Address: |
KLEIN & SZEKERES, LLP
Suite 700
4199 Campus Drive
Irvine
CA
92612
US
|
Family ID: |
26064569 |
Appl. No.: |
09/728499 |
Filed: |
November 30, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09728499 |
Nov 30, 2000 |
|
|
|
PCT/DK99/00290 |
Jun 1, 1999 |
|
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Current U.S.
Class: |
426/522 ;
426/231; 426/580; 99/452 |
Current CPC
Class: |
A23L 3/003 20130101;
A23L 3/22 20130101; A23L 3/18 20130101; A23L 3/20 20130101; A23C
3/033 20130101 |
Class at
Publication: |
426/522 ;
426/580; 426/231; 99/452 |
International
Class: |
A23C 003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 1998 |
DK |
PA 1998 00746 |
Dec 9, 1999 |
DK |
PA 1999 01766 |
Claims
What is claimed is:
1. A method of pasteurizing a flow of a liquid product consisting
of beer, milk, milk products, fruit juice, fruit juice products or
similar consumable liquids, the amount of such liquid product to be
pasteurized being at least around 1,000 1/hr, the method comprising
the steps of: providing one or more heat exchangers for exchanging
heat between the flow of liquid product and heating and/or cooling
means, respectively; and maintaining the flow of liquid product
inside said one or more heat exchangers during a period of time and
at temperatures sufficient for the uptake of Pasteurizing Units
(PU's), the majority of a desired predetermined amount of PU's
being taken up by the flow of liquid product during said period of
time.
2. The method according to claim 1, wherein said majority is
selected from the group of values consisting of at least 51%, at
least 55%, at least 60%, at least 65%, at least 70%, at least 75%,
at least 80%, at least 85%, at least 90% and at least 95% of said
desired amount of PU's.
3. A method of pasteurizing a flow of a liquid product consisting
of beer, milk, milk products, fruit juice, fruit juice products or
similar consumable liquids, the amount of such liquid product to be
pasteurized being at least around 1,000 1/hr, the method comprising
the steps of: providing a pasteurizing heat exchanger for
exchanging heat between the liquid product and a flow of fluid,
preferably water, so as to heat or cool the liquid product during
the passage thereof through the pasteurizing heat exchanger;
introducing the flow of liquid product at a product inlet
temperature into an inlet of the pasteurizing heat exchanger;
introducing the flow of fluid at a fluid inlet temperature into the
pasteurizing heat exchanger; discharging the flow of liquid product
from an outlet of the pasteurizing heat exchanger at a product
outlet temperature; and controlling the rate of flow of the flow of
liquid product and/or said product inlet temperature and/or the
rate of flow of the flow of fluid and/or said fluid inlet
temperature and/or said product outlet temperature such that the
flow of liquid product takes up the majority of the Pasteurizing
Units (PU's) required for obtaining a desired degree of
pasteurization during the passage of said flow of liquid product
through the pasteurizing heat exchanger.
4. The method according to claim 3, wherein said majority is
selected from the group of values consisting of at least 51%, at
least 55%, at least 60%, at least 65%, at least 70%, at least 75%,
at least 80%, at least 85%, at least 90% and at least 95% of said
desired amount of PU's
5. The method according to claim 3 and further comprising the steps
of: providing one or more additional pasteurizing heat exchangers
comprising the features of the pasteurizing heat exchanger
according to claim 3, all the pasteurizing heat exchangers being
arranged in series such that the flow of liquid product is
conducted from the outlet of one pasteurizing heat exchanger to the
inlet of the succeeding pasteurizing heat exchanger; and
controlling the rate of flow of the flow of liquid product through
the series of pasteurizing heat exchangers and/or said product
inlet temperature of at least the first of the heat exchangers in
said series and/or the rate of flow of the flow of fluid through at
least one and preferably all the heat exchangers in said series
and/or said fluid inlet temperature of the flow of fluid introduced
into at least one and preferably all the heat exchangers in said
series and/or said product outlet temperature of at least the last
of the heat exchangers in said series such that the entire flow of
liquid product takes up a majority of the PU's required for
obtaining a desired degree of pasteurization during the passage of
said liquid product through said series of pasteurizing heat
exchangers.
6. The method according to claim 5, wherein said majority is
selected from the group of values consisting of at least 51%, at
least 55%, at least 60%, at least 65%, at least 70%, at least 75%,
at least 80%, at least 85%, at least 90% and at least 95% of said
desired amount of PU's.
7. The method according to claim 5, wherein the length of the path
of the flow of liquid product from the outlet of one of the
pasteurizing heat exchangers in said series to the inlet of the
succeeding pasteurizing heat exchanger in said series is
substantially as short as possible so as to minimize the volume of
liquid product that is not in heat exchange relationship with a
flow of fluid.
8. The method according to claim 3, further comprising the steps
of: providing one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing into the pasteurizing heat exchanger and the
pasteurized liquid product flowing from the pasteurizing heat
exchanger so as to cool the pasteurized liquid product, pre-heat
the unpasteurized liquid product to product inlet temperature and
recuperate heat energy from the pasteurized liquid product; and
determining the number of PU's taken up by the liquid product when
flowing through the one or more regenerative heat exchangers in
both directions and when flowing along paths of flow leading to and
from the pasteurizing heat exchanger from and to, respectively, the
one or more regenerative heat exchangers such that the amount of
additional PU's to be taken up by the liquid product in the
pasteurizing heat exchanger can be determined.
9. The method according to claims 3, comprising the further step
of: providing one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing into the pasteurizing heat exchanger and the
pasteurized liquid product flowing from the pasteurizing heat
exchanger so as to cool the pasteurized liquid product, pre-heat
the unpasteurized liquid product to said first temperature and
recuperate the heat energy from the pasteurized liquid product;
wherein the length of said paths of flow to and from the
pasteurizing heat exchanger from and to, respectively, the one or
more regenerative heat exchangers are substantially as short as
possible so as to minimize the volume of liquid product that is not
in heat exchange relationship with a flow of said fluid.
10. A method of monitoring the uptake of Pasteurizing Units (PU's)
of a flow of liquid product consisting of beer, milk, milk
products, fruit juice, fruit juice products or similar consumable
liquids, the amount of such liquid product to be pasteurized being
at least around 1,000 1/hr, in a pasteurizing apparatus comprising
means for exchanging heat between one or more flows of a fluid,
preferably water, and the flow of liquid product, said method
comprising the steps of: measuring consecutive values of the
temperature and of the rate of flow of the fluid and the liquid
product at first points along the paths of flow thereof through the
apparatus; and establishing a mathematical model of the apparatus
and, based on said measured consecutive values and the parameters
for the heat transfer between the flows of fluid and the flow of
liquid product at a number of second points along said paths of
flow, calculating the number of PU's taken up by a portion of
liquid at any or all of said second points.
11. The method according to claim 10, wherein the number of second
points is sufficiently large for obtaining a desired accuracy of
the monitoring of said uptake of PU's.
12. The method according to claim 11, wherein the number of second
points is selected from the group of values consisting of at least
5, at least 25, at least 50, at least 100, at least 150, at least
200, at least 300, at least 400, at least 500, at least 600, at
least 700, at least 800, at least 900, and at least 1,000, the
maximum number of said second points being determined by the
calculating capacity of a computing means utilized for calculating
said number of PU's.
13. A method of controlling the uptake of Pasteurizing Units (PU's)
of a flow of liquid product consisting of beer, milk, milk
products, fruit juice, fruit juice products or similar consummable
liquids, the amount of such liquid product to be pasteurized being
at least around 1,000 1/hr, in a pasteurizing apparatus comprising
means for exchanging heat between one or more flows of a fluid,
preferably water, and the flow of liquid product, said method
comprising the steps of: measuring consecutive values of the
temperature and of the rate of flow of the fluid and the liquid
product at first points along the paths of flow thereof throughout
the apparatus; establishing a mathematical model of the apparatus
and, based on said measured consecutive values and the parameters
for the heat transfer between the flows of fluid and the flow of
liquid product at a number of second points along said paths of
flow, calculating the number of PU's taken up by a portion of
liquid at any of said second points; and altering the temperature
and/or rate of flow of one or more of the flows of fluid and/or the
rate of flow of the flow of the liquid product such that any
unacceptable difference between the calculated uptake of PU's and a
desired uptake of PU's for one or more portions of liquid product
at corresponding one or more second points is eliminated before
said one or more portions exit the apparatus.
14. A method of monitoring the operation of a pasteurizing
apparatus for pasteurizing a flow of liquid product consisting of
beer, milk, milk products, fruit juice, fruit juice products or
similar consumable liquids, the amount of such liquid product to be
pasteurized being at least around 1,000 1/hr, said apparatus
comprising: one or more heat exchangers for heating and/or cooling
the flow of liquid product; sources of flows of heating and/or
cooling fluid for heating and/or cooling the flow of liquid product
by means of heat exchange between the flows of fluid and the flow
of liquid product; a source of the flow of liquid product to be
pasteurized; receiving means for receiving the pasteurized flow of
liquid product; conduits for flow communication between said
elements of the apparatus; temperature sensing means for sensing
the temperature of the liquid product and of said fluid at first
points along the flow paths of the liquid product and the fluid,
respectively; and flow rate sensing means for sensing the flow rate
of the flows of fluid and of the flow of liquid product; computing
means connected to said temperature sensing means and said flow
rate sensing means for receiving measured values of temperatures
and flow rates, respectively; wherein the method comprises the
steps of: measuring consecutive values of the temperature and of
the rate of flow of the fluid and the liquid product at said first
points; establishing a mathematical model of the apparatus; and
based on said measured consecutive values and the parameters for
the heat transfer between the flows of fluid and the flow of liquid
product at a number of second points along said paths of flow,
calculating the number of PU's taken up by a portion of liquid at
any or all of said second points.
15. The method according to claim 14, wherein the number of second
points is sufficiently large for obtaining a desired accuracy of
the monitoring of said uptake of PU's.
16. The method according to claim 14, wherein the number of second
points is selected from the group of values consisting of at least
5, at least 25, at least 50, at least 100, at least 150, at least
200, at least 300, at least 400, at least 500, at least 600, at
least 700, at least 800, at least 900, and at least 1,000, the
maximum number of said second points being determined by the
calculating capacity of a computing means utilized for calculating
said number of PU's.
17. The method according to claim 14, wherein said second points
consist of sections, cells or finite elements into which at least
part and preferably substantially the entire lengths of the paths
of flow of the flows of fluid and the flow of liquid product have
been subdivided, each such finite element comprising a certain
volume of fluid and/or liquid product and being allocated certain
parameters for the heat transfer to and from the liquid product
and/or to and from the fluid in said each finite element.
18. A method of controlling the operation of a pasteurizing
apparatus for pasteurizing a flow of liquid product consisting of
beer, milk, milk products, fruit juice, fruit juice products or
similar consumable liquids, the amount of such liquid product to be
pasteurized being at least around 1,000 1/hr, said apparatus
comprising: one or more heat exchangers for heating and/or cooling
the flow of liquid product; sources of flows of heating and/or
cooling fluid for heating and/or cooling the flow of liquid product
by means of heat exchange between the flows of fluid and the flow
of liquid product; a source of the flow of liquid product to be
pasteurized; receiving means for receiving the pasteurized flow of
liquid product; conduits for flow communication between said
elements of the apparatus; temperature sensing means for sensing
the temperature of the liquid product and of said fluid at first
points along the flow paths of the liquid product and the fluid,
respectively; temperature control means for controlling the
temperature of the flows of fluid; flow rate sensing means for
sensing the flow rate of the flows of fluid and of the flow of
liquid product; flow rate control means for controlling the flow
rate of the flows of fluid and of the flow of liquid product; and
computing means connected to said temperature sensing means and
said flow rate sensing means for receiving measured values of
temperatures and flow rates, respectively, to said flow control
means for sending signals thereto for controlling said rates of
flow and to said temperature control means for sending signals
thereto for controlling said temperature of the flows of fluid;
wherein the method comprises the steps of: measuring consecutive
values of the temperature and of the rate of flow of the fluid and
the liquid product at said first points; establishing a
mathematical model of the apparatus; based on said measured
consecutive values and the parameters for the heat transfer between
the flows of fluid and the flow of liquid product at a number of
second points along said paths of flow, calculating the number of
PU's taken up by a portion of liquid at any or all of said second
points; and by means of said signals sent by the computing means
regulating the temperature and/or the rate of flow of one or more
of the flows of fluid and/or the rate of flow of the flow of the
liquid product such that any unacceptable difference between the
calculated uptake of PU's and a desired uptake of PU's for one or
more portions of liquid product at corresponding one or more second
points is eliminated before said one or more portions exit the
apparatus.
19. The method according to claim 18, wherein the number of second
points is sufficiently large for obtaining a desired accuracy of
the controlling of said uptake of PU's.
20. The method according to claim 18, wherein the number of second
points is selected from the group of values consisting at least 5,
at least 25, at least 50, at least 100, at least 150, at least 200,
at least 300, at least 400, at least 500, at least 600, at least
700, at least 800, at least 900, and at least 1,000, the maximum
number of said second points being determined by the calculating
capacity of a computing means utilized for calculating said number
of PU's.
21. The method according to claim 18, wherein said second points
consist of sections, cells or finite elements into which at least
part and preferably substantially the entire lengths of the paths
of flow of the flows of fluid and the flow of liquid product have
been subdivided, each such finite element comprising a certain
volume of fluid and/or liquid product and being allocated certain
parameters for the heat transfer to and from the liquid product
and/or to and from the fluid in said each finite element.
22. A method of controlling the uptake of Pasteurizing Units (PU's)
of a flow of liquid product consisting of beer, milk, milk
products, fruit juice, fruit juice products or similar consumable
liquids, the amount of such liquid product to be pasteurized being
at least around 1,000 1/hr, in a pasteurizing apparatus comprising
means for exchanging heat between one or more flows of a fluid,
preferably water, and the flow of liquid product, said method
comprising the steps of: measuring consecutive values of the
temperature and of the rate of flow of the fluid and the liquid
product at first points along the paths of flow thereof throughout
the apparatus; establishing a mathematical model of the apparatus;
based on said measured consecutive values and the parameters for
the heat transfer between the flows of fluid and the flow of liquid
product at a number of second points along said paths of flow,
calculating the number of PU's taken up by a portion of liquid
product at any of said second points; establishing an ideal
PU-uptake value for each of said second points for the uptake of
PU's by the liquid product along the path of flow thereof through
the apparatus for a given rate of flow of the flow of liquid
product, for given rates of flow of the flows of fluid and for
given temperatures of the flows of fluid; and altering the
temperature and/or rate of flow of one or more of the flows of
fluid and/or the rate of flow of the flow of the liquid product
such that all portions of liquid product at the corresponding one
or more second points have a PU-uptake at least equal to said ideal
PU-uptake value at the corresponding second point.
23. A method of controlling the uptake of Pasteurizing Units (PU's)
of a flow of liquid product consisting of beer, milk, milk
products, fruit juice, fruit juice products or similar consumable
liquids, the amount of such liquid product to be pasteurized being
at least around 1,000 1/hr, in a pasteurizing apparatus, wherein
the apparatus comprises: one or more heat exchangers for heating
and/or cooling the flow of liquid product; sources of flows of
heating and/or cooling fluid for heating and/or cooling the flow of
liquid product by means of heat exchange between the flows of fluid
and the flow of liquid product; a source of the flow of liquid
product to be pasteurized; receiving means for receiving the
pasteurized flow of liquid product; conduits for flow communication
between said elements of the apparatus; temperature sensing means
for sensing the temperature of the liquid product and of said fluid
at first points along the flow paths of the liquid product and the
fluid, respectively; temperature control means for controlling the
temperature of the flows of fluid; flow rate sensing means for
sensing the flow rate of the flows of fluid and of the flow of
liquid product; flow rate control means for controlling the flow
rate of the flows of fluid and of the flow of liquid product; and
computing means connected to said temperature sensing means and
said flow rate sensing means for receiving measured values of
temperatures and flow rates, respectively, to said flow control
means for sending signals thereto for controlling said rates of
flow and to said temperature control means for sending signals
thereto for controlling said temperature of the flows of fluid;
wherein the method comprises the steps of: measuring consecutive
values of the temperature and of the rate of flow of the fluid and
the liquid product at said first points; establishing a
mathematical model of the apparatus; based on said measured
consecutive values and the parameters for the heat transfer between
the flows of fluid and the flow of liquid product at a number of
second points along said paths of flow, calculating the number of
PU's taken up by a portion of liquid at any or all of said second
points; establishing an ideal PU-uptake value for each of said
second points for the uptake of PU's by the liquid product along
the path of flow thereof through the apparatus for a given rate of
flow of the flow of liquid product, for given rates of flow of the
flows of fluid and for given temperatures of the flows of fluid;
and by means of said signals sent by the computing means regulating
the temperature and/or the rate of flow of one or more of the flows
of fluid and/or the rate of flow of the flow of the liquid product
such that all portions of liquid product at the corresponding one
or more second points have a PU-uptake at least equal to said ideal
PU-uptake value at the corresponding second point.
24. The method according to claim 23, wherein the number of second
points is sufficiently large for obtaining a desired accuracy of
the controlling of said uptake of PU's.
25. The method according to claim 23, wherein the number of second
points is selected from the group of values consisting of at least
5, at least 25, at least 50, at least 100, at least 150, at least
200, at least 300, at least 400, at least 500, at least 600, at
least 700, at least 800, at least 900, at least 1,000, the maximum
number of said second points being determined by the calculating
capacity of a computing means utilized for calculating said number
of PU's.
26. The method according to claim 23, wherein said second points
consist of sections, cells or finite elements into which at least
part and preferably substantially the entire lengths of the paths
of flow of the flows of fluid and the flow of liquid product have
been subdivided, each such finite element comprising a certain
volume of fluid and/or liquid product and being allocated certain
parameters for the heat transfer to and from the liquid product
and/or to and from the fluid in said each finite element.
27. An apparatus for pasteurizing a flow of a liquid product
consisting of beer, milk, milk products, fruit juice, fruit juice
products or similar consumable liquids, the amount of such liquid
product to be pasteurized being at least around 1,000 1/hr, the
apparatus comprising: a pasteurizing heat exchanger for exchanging
heat between the flow of liquid product and a flow of fluid,
preferably water, so as to heat or cool the liquid product during
the passage thereof through the pasteurizing heat exchanger; first
conduit means for introducing the flow of liquid product at a
product inlet temperature into an inlet of the pasteurizing heat
exchanger; second conduit means for introducing the flow of fluid
at a fluid inlet temperature into the pasteurizing heat exchanger;
third conduit means for discharging the flow of liquid product from
an outlet of the pasteurizing heat exchanger at a product outlet
temperature; and control means for controlling the rate of flow of
the flow of liquid product and/or said product inlet temperature
and/or the rate of flow of the flow of fluid and/or said fluid
inlet temperature and/or said product outlet temperature such that
the flow of liquid product takes up the majority of the
Pasteurizing Units (PU's) required for obtaining a desired degree
of pasteurization during the passage of said flow of liquid product
through the pasteurizing heat exchanger.
28. The apparatus according to claim 27, wherein said majority is
selected from the group of values consisting of at least 51%, at
least 55%, at least 60%, at least 65%, at least 70%, at least 75%,
at least 80%, at least 85%, at least 90% and at least 95% of said
desired amount of PU's.
29. The apparatus according to claim 27 and further comprising: one
or more additional pasteurizing heat exchangers comprising the
features of the pasteurizing heat exchanger according to claim 27,
all the heat exchangers being arranged in series and having
intermediate conduits for conducting the flow of liquid product
from the outlet of one pasteurizing heat exchanger to the inlet of
the succeeding pasteurizing heat exchanger; and control means for
controlling the rate of flow of the flow of liquid product through
the series of pasteurizing heat exchangers and/or said product
inlet temperature of at least the first of the heat exchangers in
said series and/or the rate of flow of the flow of fluid through at
least one and preferably all the heat exchangers in said series
and/or said fluid inlet temperature of the flow of fluid introduced
into at least one and preferably all the heat exchangers in said
series and/or said product outlet temperature of at least the last
of the heat exchangers in said series such that the entire flow of
liquid product takes up a majority of the Pasteurizing Units, PU's,
required for obtaining a desired degree of pasteurization during
the passage of said liquid product through said series of
pasteurizing heat exchangers.
30. The apparatus according to claim 29, wherein said majority is
selected from the group of values consisting of at least 51%, at
least 55%, at least 60%, at least 65%, at least 70%, at least 75%,
at least 80%, at least 85%, at least 90% and at least 95% of said
desired amount of PU's.
31. The apparatus according to claim 29, wherein the lengths of
said intermediate conduits are substantially as short as possible
so as to minimize the volume of liquid product that is not in heat
exchange relationship with a flow of fluid.
32. The apparatus according to claim 29, the apparatus further
comprising: one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing through said first conduit means into the one or
more pasteurizing heat exchangers and the pasteurized liquid
product flowing through said third conduit means from the one or
more pasteurizing heat exchangers so as to cool the pasteurized
liquid product, pre-heat the unpasteurized liquid product to
product inlet temperature and recuperate heat energy from the
pasteurized liquid product; the lengths of said first and third
conduit means extending between the one or more pasteurizing heat
exchangers and the one or more regenerative heat exchangers being
substantially as short as possible so as to minimize the volume of
liquid product that is not in heat exchange relationship with a
flow of said fluid.
33. An apparatus for pasteurizing a flow of a liquid product
consisting of beer, milk, milk products, fruit juice, fruit juice
products or similar consumable liquids, the amount of such liquid
product to be pasteurized being at least around 1,000 1/hr, the
apparatus comprising: a pasteurizing heat exchanger for exchanging
heat between the flow of liquid product and a flow of fluid,
preferably water, so as to heat or cool the liquid product during
the passage thereof through the pasteurizing heat exchanger; first
conduit means for introducing the flow of liquid product at a
product inlet temperature into an inlet of the pasteurizing heat
exchanger; second conduit means for introducing the flow of fluid
at a fluid inlet temperature into the pasteurizing heat exchanger;
third conduit means for discharging the flow of liquid product from
an outlet of the pasteurizing heat exchanger at a product outlet
temperature; and one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing through said first conduit means into the
pasteurizing heat exchanger and the pasteurized liquid product
flowing through said third conduit means from the pasteurizing heat
exchanger so as to cool the pasteurized liquid product, pre-heat
the unpasteurized liquid product to product inlet temperature and
recuperate heat energy from the pasteurized liquid product; the
lengths of said first and third conduit means extending between the
pasteurizing heat exchanger and the one or more regenerative heat
exchangers being substantially as short as possible so as to
minimize the volume of liquid product that is not in heat exchange
relationship with a flow of said fluid.
34. The apparatus according to claim 33, further comprising one or
more additional pasteurizing heat exchangers comprising the
features of the pasteurizing heat exchanger according to claim 33,
all the pasteurizing heat exchangers being arranged in series and
having intermediate conduits for conducting the flow of liquid
product from the outlet of one pasteurizing heat exchanger to the
inlet of the succeeding pasteurizing heat exchanger, and the
lengths of said intermediate conduits being substantially as short
as possible so as to minimize the volume of liquid product that is
not in heat exchange relationship with a flow of fluid.
35. An apparatus for pasteurizing a flow of a liquid product
consisting of beer, milk, milk products, fruit juice, fruit juice
products or similar consumable liquids, the amount of such liquid
product to be pasteurized being at least around 1,000 1/hr, in a
continuous flow and having a heating area, a pasteurizing area and
a cooling area, and pump elements for feeding the product in a
given flow from the admission opening in the apparatus to its
discharge opening, through the above areas in the order in which
they are mentioned, whereby the heating, the pasteurizing and the
cooling is effected by the transfer of heat between the product
itself in cold and in hot condition and a liquid, preferably water,
which flows through one or more heat exchangers and a holding pipe
without temperature regulation, in the said areas, the areas being
divided into zones which extend in the flow direction of the
product, and the temperature of the water is adjusted in accordance
with the course of the heat transfer aimed at in the zone, wherein
one of the part zones is connected to hot and cold water,
characterized in that the apparatus between the cold and the hot
part of the regenerative heat exchanger contains a pasteurizing
part consisting of heat exchangers, said heat exchangers being
divided into zones, each of which has a connection for both a
heating medium and a cooling medium, or only for a cooling medium
in one or more of the zones, the pasteurizing part being connected
to the cold and the hot part of the regenerative heat exchanger by
means of conduits and the holding pipe solely consisting of said
conduits.
36. A method for the pasteurization of a continuous flow of a
liquid product consisting of beer, milk, milk products, fruit
juice, fruit juice products or similar consumable liquids, the
amount of such liquid product to be pasteurized being at least
around 1,000 1/hr, in an apparatus which has a heating area, a
pasteurizing area and a cooling area, and pump elements for feeding
the product in a given flow from the admission opening in the
apparatus to its discharge opening, through the above areas in the
order in which they are mentioned, whereby the heating, the
pasteurizing and the cooling is effected by the transfer of heat
between the product itself in cold and in hot condition and a
liquid, preferably water, which flows through one or more heat
exchangers and a holding pipe without temperature regulation, in
the said areas, the areas being divided into zones which extend in
the flow direction of the product, and the temperature of the water
is adjusted in accordance with the course of the heat transfer
aimed at in the zone, characterized in that: one of the
pasteurizing zones is connected to hot and cold water; the
pasteurizing area is divided into a number of individual
pasteurizing zones with connection for both heating and cooling or,
in the event of a stop in production, for cooling of the product in
order to hold the temperature under the pasteurizing temperature,
and upon restarting to heat the product again to a temperature
close to the pasteurizing temperature; the pasteurizing area is
connected to the heating area and the cooling area by means of
conduits; and the holding pipe solely consists of said
conduits.
37. An apparatus for the pasteurizing of liquid products in a
continuous flow, the apparatus comprising: a regenerative part into
which the product is fed by a supply pump; a pasteurizing part to
which the product is led from the regenerative part and from which
pasteurizing part the product is led back to the regenerative part,
both the regenerative part and the pasteurizing part consisting of
heat exchangers; a mixing valve for supplying hot or cold water to
the pasteurizing part, so that the pasteurizing part cannot only
heat the product to the pasteurization temperature, but also cool
the product down in the event of a stop in production; and
temperature sensors placed before and after the pasteurizing part
for controlling the pasteurization process..
38. The apparatus according to claim 37, wherein the apparatus
comprises two main heat exchangers, a regenerative heat exchanger
which is divided into two zones, and a pasteurizing heat exchanger
which is divided into three zones.
39. The apparatus according to claim 38, wherein a temperature
sensor is placed after each of said three pasteurizing zones so as
to register whether or not the necessary temperatures have been
achieved so that heating and cooling, respectively can be
controlled on the secondary side of the pasteurizing heat
exchanger.
40. A method for the pasteurizing of liquid products in a
continuous flow, comprising the steps of: providing a regenerative
part of a pasteurizing apparatus and a pasteurizing part of said
pasteurizing apparatus, both the regenerative part and the
pasteurizing part comprising heat exchangers; feeding product into
the regenerative part; leading the product from the regenerative
part to the pasteurizing part; leading the product from the
pasteurizing part back to the regenerative part; heating the
product in the regenerative part by transfer of heat from the
product led back to the regenerative part from the pasteurizing
part; heating the product to the pasteurization temperature in the
pasteurizing part and cooling the product down in the pasteurizing
part in the event of a production stop by supplying hot or cold
water, respectively, to the pasteurizing part; and controlling the
pasteurization process by means of temperature sensors placed
before and after the pasteurizing part.
41. The method according to claim 40, wherein the pasteurizing
apparatus comprises two main heat exchangers, a regenerative heat
exchanger which is divided into two zones, and a pasteurizing heat
exchanger which is divided into three zones.
42. The method according to claim 41, comprising the further steps
of: providing a temperature sensor placed after each of said three
pasteurizing zones; by means of said temperature sensors
registering whether or not the necessary temperatures have been
achieved; and based on said registration by said temperature
sensors, controlling heating and cooling, respectively, on the
secondary side of the pasteurizing heat exchanger.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of co-pending
International Application No. PCT/DK99/00290, filed Jun. 1,
1999.
FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a method of pasteurizing a
flow of a liquid product consisting of beer, milk, milk products,
fruit juice, fruit juice products or similar consumable liquids,
the amount of such liquid product to be pasteurized being at least
around 1,000 l/hr.
[0004] In connection with heat treating such liquid products to
eliminate the bacterial content thereof, a measure of the
effectiveness of the heat treatment or pasteurization is the uptake
of Pasteurizing Units, PU's. The uptake of PU's is a function of
the temperature of the liquid product and the time period in which
the liquid product is at a temperature at which PU's are taken
up.
[0005] It is essential for most applications that a minimum number
of PU's be taken up, but on the other hand over-pasteurization
should not happen as it will be detrimental to the quality of the
pasteurized product.
[0006] Many pasteurizing methods and apparatus have a heat
exchanger for heating the product up to a certain pasteurizing
temperature at which the product is maintained for a period of
time. Two conventional types of such apparatus are described in the
following in connection with FIGS. 1 and 2 in the accompanying
drawings. These known pasteurizers, as well as the pasteurizer
disclosed in U.S. Pat. No. 4,997,662, have a holding tube in which
the liquid product flows at a certain temperature to which it has
been heated before entering the holding pipe.
[0007] In case of an anomaly in the operation of the pasteurizer
such as a stoppage or a sharp decrease in flow rate of the product,
the product in the holding pipe is subjected to over-pasteurization
or under-pasteurization so that it has to be discarded. A by-pass
can be established or water can substitute the product until normal
operation is obtained again.
SUMMARY OF THE INVENTION
[0008] A main object of the invention is to provide a method
wherein the above drawbacks have been eliminated and wherein a more
secure pasteurization is achieved where under-pasteurization can be
avoided under substantially all conditions, anomalous or not.
[0009] According to the invention, this object is achieved by
providing one or more heat exchangers for exchanging heat between
the flow of liquid product and heating and/or cooling means,
respectively, and maintaining the flow of liquid product inside
said one or more heat exchangers during a period of time and at
temperatures sufficient for the uptake of Pasteurizing Units (PU's)
the majority of a desired predetermined amount of PU's being taken
up by the flow of liquid product during said period of time.
[0010] Hereby, the pasteurizing takes place in a region of the
pasteurizer where it is possible to regulate the temperature of the
product and thus avoid over and under-pasteurization when
operational anomalies such as stoppages occur.
[0011] The advantages of the method according to the invention are
greater the greater the degree of pasteurization is carried out in
said region and therefore the said majority advantageously is at
least 51% of said desired amount of PU's, preferably at least 55%,
more preferably at least 60%, even more preferably at least 65%,
even more preferably at least 70%, even more preferably at least
75%, even more preferably at least 80%, even more preferably at
least 85%, even more preferably at least 90% and even more
preferably at least 95%.
[0012] The invention also relates to a method of pasteurizing a
flow of a liquid product consisting of beer, milk, milk products,
fruit juice, fruit juice products or similar consumable liquids,
the amount of such liquid product to be pasteurized being at least
around 1,000 l/hr, the method comprising the steps of:
[0013] providing a pasteurizing heat exchanger for exchanging heat
between the liquid product and a flow of fluid, preferably water,
so as to heat or cool the liquid product during the passage thereof
through the pasteurizing heat exchanger, introducing the flow of
liquid product at a product inlet temperature into an inlet of the
pasteurizing heat exchanger, introducing the flow of fluid at a
fluid inlet temperature into the pasteurizing heat exchanger,
discharging the flow of liquid product from an outlet of the
pasteurizing heat exchanger at a product outlet temperature, and
controlling the rate of flow of the flow of liquid product and/or
said product inlet temperature and/or the rate of flow of the flow
of fluid and/or said fluid inlet temperature and/or said product
outlet temperature such that the flow of liquid product takes up
the majority of the Pasteurizing Units, PU's, required for
obtaining a desired degree of pasteurization during the passage of
said flow of liquid product through the pasteurizing heat
exchanger.
[0014] Advantageously said majority is at least 51% of said desired
amount of PU's, preferably at least 55%, more preferably at least
60%, even more preferably at least 65%, even more preferably at
least 70%, even more preferably at least 75%, even more preferably
at least 80%, even more preferably at least 85%, even more
preferably at least 90% and even more preferably at least 95%.
[0015] In most cases it is advantageous to provide several
pasteurizing heat exchangers so as to be able to regulate the
temperature and PU uptake more efficiently and quickly, and
therefore the method according to the invention preferably further
comprises the steps of:
[0016] providing one or more additional pasteurizing heat
exchangers comprising the features of the pasteurizing heat
exchanger according to claim 3, all the pasteurizing heat
exchangers being arranged in series such that the flow of liquid
product is conducted from the outlet of one pasteurizing heat
exchanger to the inlet of the succeeding pasteurizing heat
exchanger, and controlling the rate of flow of the flow of liquid
product through the series of pasteurizing heat exchangers and/or
said product inlet temperature of at least the first of the heat
exchangers in said series and/or the rate of flow of the flow of
fluid through at least one and preferably all the heat exchangers
in said series and/or said fluid inlet temperature of the flow of
fluid introduced into at least one and preferably all the heat
exchangers in said series and/or said product outlet temperature of
at least the last of the heat exchangers in said series such that
the entire flow of liquid product takes up a majority of the
Pasteurizing Units, PU's, required for obtaining a desired degree
of pasteurization during the passage of said liquid product through
said series of pasteurizing heat exchangers.
[0017] Hereby, it is achieved that the PU's taken up by the product
in the pasteurizing heat exchangers may be regulated more
accurately and rapidly.
[0018] Advantageously, said majority is at least 51% of said
desired amount of PU's, preferably at least 55%, more preferably at
least 60%, even more preferably at least 65%, even more preferably
at least 70%, even more preferably at least 75%, even more
preferably at least 80%, even more preferably at least 85%, even
more preferably at least 90% and even more preferably at least
95%.
[0019] So as to maximize the volume of product being heat treated
in a region where the temperature can be regulated, preferably the
length of the path of the flow of liquid product from the outlet of
one of the pasteurizing heat exchangers in said series to the inlet
of the succeeding pasteurizing heat exchanger in said series is
substantially as short as possible so as to minimize the volume of
liquid product that is not in heat exchange relationship with a
flow of fluid.
[0020] In most cases it is advantageous to provide a heat
recuperating section to recuperate heat from the hot pasteurized
product and therefore the method preferably further comprises the
steps of:
[0021] providing one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing into the one or more pasteurizing heat exchangers
and the pasteurized liquid product flowing from the one or more
pasteurizing heat exchangers so as to cool the pasteurized liquid
product, pre-heat the unpasteurized liquid product to product inlet
temperature and recuperate heat energy from the pasteurized liquid
product, and determining the number of PU's taken up by the liquid
product when flowing through the one or more regenerative heat
exchangers in both directions and when flowing along paths of flow
leading to and from the one or more pasteurizing heat exchangers
from and to, respectively, the one or more regenerative heat
exchangers such that the amount of additional PU's to be taken up
by the liquid product in the one or more pasteurizing heat
exchangers can be determined.
[0022] Hereby, the influence of the regenerative heat exchangers
may be taken into account in the regulation of the temperature in
the pasteurizing heat exchangers in a manner not subject to
inaccuracies because of the effect of said regenerative heat
exchangers.
[0023] So as to reduce the volume of liquid product in a region
without temperature regulation possibility, the method preferably
comprises the further step of:
[0024] providing one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing into the one or more pasteurizing heat exchangers
and the pasteurized liquid product flowing from the one or more
pasteurizing heat exchangers so as to cool the pasteurized liquid
product, pre-heat the unpasteurized liquid product to said first
temperature and recuperate the heat energy from the pasteurized
liquid product, wherein the length of said paths of flow to and
from the one or more pasteurizing heat exchangers from and to,
respectively, the one or more regenerative heat exchangers are
substantially as short as possible so as to minimize the volume of
liquid product that is not in heat exchange relationship with a
flow of said fluid.
[0025] In a further aspect the invention relates to a method of
monitoring the uptake of Pasteurizing Units, PU's, of a flow of
liquid product consisting of beer, milk, milk products, fruit
juice, fruit juice products or similar consumable liquids, the
amount of such liquid product to be pasteurized being at least
around 1,000 l/hr, in a pasteurizing apparatus comprising means for
exchanging heat between one or more flows of a fluid, preferably
water, and the flow of liquid product.
[0026] In the known methods of pasteurization the monitoring of the
PU uptake is very coarse and inaccurate, and therefore the security
against deficient pasteurization is relatively low.
[0027] An object of the invention is to provide a method of
monitoring the PU uptake that is much more secure and accurate so
as to be able to provide a pasteurized product with a consistently
high quality.
[0028] This object is achieved according to the invention by the
method comprising the steps of:
[0029] measuring consecutive values of the temperature and of the
rate of flow of the fluid and the liquid product at first points
along the paths of flow thereof through the apparatus, establishing
a mathematical model of the apparatus and, based on said measured
consecutive values and the parameters for the heat transfer between
the flows of fluid and the flow of liquid product at a number of
second points along said paths of flow, calculating the number of
PU's taken up by a portion of liquid at any or all of said second
points.
[0030] Hereby, the PU uptake may be monitored in an accurate and
rapid manner, the accuracy depending on the number of second points
in the model and therefore preferably the number of second points
is sufficiently large for obtaining a desired accuracy of the
monitoring of said uptake of PU's, the number of second points
advantageously being at least 5, preferably at least 25, more
preferably at least 50, even more preferably at least 100, even
more preferably at least 150, even more preferably at least 200,
even more preferably at least 300, even more preferably at least
400, even more preferably at least 500, even more preferably at
least 600, even more preferably at least 700, even more preferably
at least 800, even more preferably at least 900, even more
preferably at least 1,000, the maximum number of said second points
being determined by the calculating capacity of a computing means
utilized for calculating said number of PU's.
[0031] The number of second points chosen will be a trade off
between the desired accuracy of the monitoring and the cost of the
calculating capacity.
[0032] A further aspect of the invention is to provide a method of
controlling the uptake of Pasteurizing Units, PU's, of a flow of
liquid product consisting of beer, milk, milk products, fruit
juice, fruit juice products or similar consumable liquids, the
amount of such liquid product to be pasteurized being at least
around 1,000 l/hr, in a pasteurizing apparatus comprising means for
exchanging heat between one or more flows of a fluid, preferably
water, and the flow of liquid product.
[0033] In the known methods of pasteurizing such liquid products,
the method of controlling the uptake of PU's by the product is very
simple and coarse and therefore the security against under and
over-pasteurization is relatively low, particularly in connection
with operational anomalies such as stoppages and re-starts.
[0034] An object of the invention is therefore to provide a method
of controlling said PU uptake that is accurate, rapid and allows
fine-tuning of the pasteurizing process.
[0035] According to the invention this object is achieved by the
method comprising the steps of:
[0036] measuring consecutive values of the temperature and of the
rate of flow of the fluid and the liquid product at first points
along the paths of flow thereof throughout the apparatus,
establishing a mathematical model of the apparatus and, based on
said measured consecutive values and the parameters for the heat
transfer between the flows of fluid and the flow of liquid product
at a number of second points along said paths of flow, calculating
the number of PU's taken up by a portion of liquid at any of said
second points, and altering the temperature and/or rate of flow of
one or more of the flows of fluid and/or the rate of flow of the
flow of the liquid product such that any unacceptable difference
between the calculated uptake of PU's and a desired uptake of PU's
for one or more portions of liquid product at corresponding one or
more second points is eliminated before said one or more portions
exit the apparatus.
[0037] The invention further relates to a method of monitoring the
operation of a pasteurizing apparatus for pasteurizing a flow of
liquid product consisting of beer, milk, milk products, fruit
juice, fruit juice products or similar consumable liquids, the
amount of such liquid product to be pasteurized being at least
around 1,000 1/hr, said apparatus comprising the following
elements:
[0038] one or more heat exchangers for heating and/or cooling the
flow of liquid product,
[0039] sources of flows of heating and/or cooling fluid for heating
and/or cooling the flow of liquid product by means of heat exchange
between the flows of fluid and the flow of liquid product, a source
of the flow of liquid product to be pasteurized, receiving means
for receiving the pasteurized flow of liquid product, the apparatus
further comprising:
[0040] conduits for flow communication between said elements of the
apparatus,
[0041] temperature sensing means for sensing the temperature of the
liquid product and of said fluid at first points along the flow
paths of the liquid product and the fluid, respectively,
[0042] flow rate sensing means for sensing the flow rate of the
flows of fluid and of the flow of liquid product,
[0043] computing means connected to said temperature sensing means
and said flow rate sensing means for receiving measured values of
temperatures and flow rates, respectively,
[0044] the method comprising the steps of:
[0045] measuring consecutive values of the temperature and of the
rate of flow of the fluid and the liquid product at said first
points, establishing a mathematical model of the apparatus, and,
based on said measured consecutive values and the parameters for
the heat transfer between the flows of fluid and the flow of liquid
product at a number of second points along said paths of flow,
calculating the number of PU's taken up by a portion of liquid at
any or all of said second points, the number of second points
preferably being sufficiently large for obtaining a desired
accuracy of the monitoring of said uptake of PU's.
[0046] Advantageously, the number of second points is at least 5,
preferably at least 25, more preferably at least 50, even more
preferably at least 100, even more preferably at least 150, even
more preferably at least 200, even more preferably at least 300,
even more preferably at least 400, even more preferably at least
500, even more preferably at least 600, even more preferably at
least 700, even more preferably at least 800, even more preferably
at least 900, even more preferably at least 1,000, the maximum
number of said second points being determined by the calculating
capacity of a computing means utilized for calculating said number
of PU's.
[0047] In a currently preferred embodiment of the method according
to the invention, said second points consist of sections, cells or
finite elements into which at least part and preferably
substantially the entire lengths of the paths of flow of the flows
of fluid and the flow of liquid product have been subdivided, each
such finite element comprising a certain volume of fluid and/or
liquid product and being allocated certain parameters for the heat
transfer to and from the liquid product and/or to and from the
fluid in said each finite element.
[0048] Hereby a particularly accurate and rapid method is
obtained.
[0049] The invention further relates to a method of controlling the
operation of a pasteurizing apparatus for pasteurizing a flow of
liquid product consisting of beer, milk, milk products, fruit
juice, fruit juice products or similar consumable liquids, the
amount of such liquid product to be pasteurized being at least
around 1,000 l/hr, said apparatus comprising the following
elements:
[0050] one or more heat exchangers for heating and/or cooling the
flow of liquid product,
[0051] sources of flows of heating and/or cooling fluid for heating
and/or cooling the flow of liquid product by means of heat exchange
between the flows of fluid and the flow of liquid product,
[0052] a source of the flow of liquid product to be
pasteurized,
[0053] receiving means for receiving the pasteurized flow of liquid
product,
[0054] the apparatus further comprising:
[0055] conduits for flow communication between said elements of the
apparatus,
[0056] temperature sensing means for sensing the temperature of the
liquid product and of said fluid at first points along the flow
paths of the liquid product and the fluid, respectively,
[0057] temperature control means for controlling the temperature of
the flows of fluid,
[0058] flow rate sensing means for sensing the flow rate of the
flows of fluid and of the flow of liquid product,
[0059] flow rate control means for controlling the flow rate of the
flows of fluid and of the flow of liquid product,
[0060] computing means connected to said temperature sensing means
and said flow rate sensing means for receiving measured values of
temperatures and flow rates, respectively, to said flow control
means for sending signals thereto for controlling said rates of
flow and to said temperature control means for sending signals
thereto for controlling said temperature of the flows of fluid,
[0061] the method comprising the steps of:
[0062] measuring consecutive values of the temperature and of the
rate of flow of the fluid and the liquid product at said first
points, establishing a mathematical model of the apparatus, based
on said measured consecutive values and the parameters for the heat
transfer between the flows of fluid and the flow of liquid product
at a number of second points along said paths of flow, calculating
the number of PU's taken up by a portion of liquid at any or all of
said second points, and by means of said signals sent by the
computing means regulating the temperature and/or the rate of flow
of one or more of the flows of fluid and/or the rate of flow of the
flow of the liquid product such that any unacceptable difference
between the calculated uptake of PU's and a desired uptake of PU's
for one or more portions of liquid product at corresponding one or
more second points is eliminated before said one or more portions
exit the apparatus.
[0063] Hereby a particularly accurate method is obtained for
ensuring that no portion of the liquid product is under-pasteurized
while at the same time limiting the extent of the corresponding
over-pasteurization. In conventional methods the product is often
severely over-pasteurized as a general operational principle so as
to avoid under-pasteurization.
[0064] Advantageously, the number of second points is sufficiently
large for obtaining a desired accuracy of the controlling of said
uptake of PU's, and the number of second points is at least 5,
preferably at least 25, more preferably at least 50, even more
preferably at least 100, even more preferably at least 150, even
more preferably at least 200, even more preferably at least 300,
even more preferably at least 400, even more preferably at least
500, even more preferably at least 600, even more preferably at
least 700, even more preferably at least 800, even more preferably
at least 900, even more preferably at least 1,000, the maximum
number of said second points being determined by the calculating
capacity of a computing means utilized for calculating said number
of PU's.
[0065] In a currently preferred embodiment of the method according
to the invention, said second points consist of sections, cells or
finite elements into which at least part and preferably
substantially the entire lengths of the paths of flow of the flows
of fluid and the flow of liquid product have been subdivided, each
such finite element comprising a certain volume of fluid and/or
liquid product and being allocated certain parameters for the heat
transfer to and from the liquid product and/or to and from the
fluid in said each finite element.
[0066] The invention further relates to a method of controlling the
uptake of Pasteurizing Units, PU's, of a flow of liquid product
consisting of beer, milk, milk products, fruit juice, fruit juice
products or similar consumable liquids, the amount of such liquid
product to be pasteurized being at least around 1,000 1/hr, in a
pasteurizing apparatus comprising means for exchanging heat between
one or more flows of a fluid, preferably water, and the flow of
liquid product, said method comprising the steps of:
[0067] measuring consecutive values of the temperature and of the
rate of flow of the fluid and the liquid product at first points
along the paths of flow thereof throughout the apparatus,
establishing a mathematical model of the apparatus, based on said
measured consecutive values and the parameters for the heat
transfer between the flows of fluid and the flow of liquid product
at a number of second points along said paths of flow, calculating
the number of PU's taken up by a portion of liquid product at any
of said second points, establishing an ideal PU-uptake value for
each of said second points for the uptake of PU's by the liquid
product along the path of flow thereof through the apparatus for a
given rate of flow of the flow of liquid product, for given rates
of flow of the flows of fluid and for given temperatures of the
flows of fluid, and altering the temperature and/or rate of flow of
one or more of the flows of fluid and/or the rate of flow of the
flow of the liquid product such that all portions of liquid product
at the corresponding one or more second points have a PU-uptake at
least equal to said ideal PU-uptake value at the corresponding
second point.
[0068] Hereby a method is achieved for ensuring that no portion of
the product is under-pasteurized.
[0069] The invention also relates to a method of controlling the
uptake of Pasteurizing Units, PU's, of a flow of liquid product
consisting of beer, milk, milk products, fruit juice, fruit juice
products or similar consumable liquids, the amount of such liquid
product to be pasteurized being at least around 1,000 1/hr, in a
pasteurizing apparatus comprising the following elements:
[0070] one or more heat exchangers for heating and/or cooling the
flow of liquid product,
[0071] sources of flows of heating and/or cooling fluid for heating
and/or cooling the flow of liquid product by means of heat exchange
between the flows of fluid and the flow of liquid product,
[0072] a source of the flow of liquid product to be
pasteurized,
[0073] receiving means for receiving the pasteurized flow of liquid
product,
[0074] the apparatus further comprising:
[0075] conduits for flow communication between said elements of the
apparatus,
[0076] temperature sensing means for sensing the temperature of the
liquid product and of said fluid at first points along the flow
paths of the liquid product and the fluid, respectively,
[0077] temperature control means for controlling the temperature of
the flows of fluid,
[0078] flow rate sensing means for sensing the flow rate of the
flows of fluid and of the flow of liquid product,
[0079] flow rate control means for controlling the flow rate of the
flows of fluid and of the flow of liquid product,
[0080] computing means connected to said temperature sensing means
and said flow rate sensing means for receiving measured values of
temperatures and flow rates, respectively, to said flow control
means for sending signals thereto for controlling said rates of
flow and to said temperature control means for sending signals
thereto for controlling said temperature of the flows of fluid,
[0081] the method comprising the steps of measuring consecutive
values of the temperature and of the rate of flow of the fluid and
the liquid product at said first points, establishing a
mathematical model of the apparatus, based on said measured
consecutive values and the parameters for the heat transfer between
the flows of fluid and the flow of liquid product at a number of
second points along said paths of flow, calculating the number of
PU's taken up by a portion of liquid at any or all of said second
points, establishing an ideal PU-uptake value for each of said
second points for the uptake of PU's by the liquid product along
the path of flow thereof through the apparatus for a given rate of
flow of the flow of liquid product, for given rates of flow of the
flows of fluid and for given temperatures of the flows of fluid,
and by means of said signals sent by the computing means regulating
the temperature and/or the rate of flow of one or more of the flows
of fluid and/or the rate of flow of the flow of the liquid product
such that all portions of liquid product at the corresponding one
or more second points have a PU-uptake at least equal to said ideal
PU-uptake value at the corresponding second point.
[0082] Advantageously, the number of second points is sufficiently
large for obtaining a desired accuracy of the controlling of said
uptake of PU's, and the number of second points is at least 5,
preferably at least 25, more preferably at least 50, even more
preferably at least 100, even more preferably at least 150, even
more preferably at least 200, even more preferably at least 300,
even more preferably at least 400, even more preferably at least
500, even more preferably at least 600, even more preferably at
least 700, even more preferably at least 800, even more preferably
at least 900, even more preferably at least 1,000, the maximum
number of said second points being determined by the calculating
capacity of a computing means utilized for calculating said number
of PU's.
[0083] In a currently preferred embodiment of the method according
to the invention, said second points consist of sections, cells or
finite elements into which at least part and preferably
substantially the entire lengths of the paths of flow of the flows
of fluid and the flow of liquid product have been subdivided, each
such finite element comprising a certain volume of fluid and/or
liquid product and being allocated certain parameters for the heat
transfer to and from the liquid product and/or to and from the
fluid in said each finite element.
[0084] In a further aspect the invention relates to an apparatus
for pasteurizing a flow of a liquid product consisting of beer,
milk, milk products, fruit juice, fruit juice products or similar
consumable liquids, the amount of such liquid product to be
pasteurized being at least around 1,000 l/hr, the apparatus
comprising:
[0085] a pasteurizing heat exchanger for exchanging heat between
the flow of liquid product and a flow of fluid, preferably water,
so as to heat or cool the liquid product during the passage thereof
through the pasteurizing heat exchanger
[0086] first conduit means for introducing the flow of liquid
product at a product inlet temperature into an inlet of the
pasteurizing heat exchanger,
[0087] second conduit means for introducing the flow of fluid at a
fluid inlet temperature into the pasteurizing heat exchanger,
[0088] third conduit means for discharging the flow of liquid
product from an outlet of the pasteurizing heat exchanger at a
product outlet temperature, and
[0089] control means for controlling the rate of flow of the flow
of liquid product and/or said product inlet temperature and/or the
rate of flow of the flow of fluid and/or said fluid inlet
temperature and/or said product outlet temperature such that the
flow of liquid product takes up the majority of the Pasteurizing
Units, PU's, required for obtaining a desired degree of
pasteurization during the passage of said flow of liquid product
through the pasteurizing heat exchanger.
[0090] Hereby, an apparatus is provided allowing correct
pasteurization of the product under all operational conditions
including anomalous conditions such as stoppages and re-starts.
Advantageously, said majority is at least 51% of said desired
amount of PU's, preferably at least 55%, more preferably at least
60%, even more preferably at least 65%, even more preferably at
least 70%, even more preferably at least 75%, even more preferably
at least 80%, even more preferably at least 85%, even more
preferably at least 90% and even more preferably at least 95%.
[0091] In a currently preferred embodiment, the apparatus according
to the invention further comprises:
[0092] one or more additional pasteurizing heat exchangers
comprising the features of the pasteurizing heat exchanger
according to claim 24, all the heat exchangers being arranged in
series and having intermediate conduits for conducting the flow of
liquid product from the outlet of one pasteurizing heat exchanger
to the inlet of the succeeding pasteurizing heat exchanger, and
[0093] control means for controlling the rate of flow of the flow
of liquid product through the series of pasteurizing heat
exchangers and/or said product inlet temperature of at least the
first of the heat exchangers in said series and/or the rate of flow
of the flow of fluid through at least one and preferably all the
heat exchangers in said series and/or said fluid inlet temperature
of the flow of fluid introduced into at least one and preferably
all the heat exchangers in said series and/or said product outlet
temperature of at least the last of the heat exchangers in said
series such that the entire flow of liquid product takes up a
majority of the Pasteurizing Units, PU's, required for obtaining a
desired degree of pasteurization during the passage of said liquid
product through said series of pasteurizing heat exchangers, said
majority advantageously being at least 51% of said desired amount
of PU's, preferably at least 55%, more preferably at least 60%,
even more preferably at least 65%, even more preferably at least
70%, even more preferably at least 75%, even more preferably at
least 80%, even more preferably at least 85%, even more preferably
at least 90% and even more preferably at least 95%.
[0094] Furthermore, in the currently preferred embodiment of the
apparatus according to the invention, the lengths of said
intermediate conduits are substantially as short as possible so as
to minimize the volume of liquid product that is not in heat
exchange relationship with a flow of fluid, and advantageously, the
apparatus further comprises:
[0095] one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing through said first conduit means into the one or
more pasteurizing heat exchangers and the pasteurized liquid
product flowing through said third conduit means from the one or
more pasteurizing heat exchangers so as to cool the pasteurized
liquid product, pre-heat the unpasteurized liquid product to
product inlet temperature and recuperate heat energy from the
pasteurized liquid product,
[0096] the lengths of said first and third conduit means extending
between the one or more pasteurizing heat exchangers and the one or
more regenerative heat exchangers being substantially as short as
possible so as to minimize the volume of liquid product that is not
in heat exchange relationship with a flow of said fluid.
[0097] The invention further relates to an apparatus for
pasteurizing a flow of a liquid product consisting of beer, milk,
milk products, fruit juice, fruit juice products or similar
consumable liquids, the amount of such liquid product to be
pasteurized being at least around 1,000 l/hr, the apparatus
comprising:
[0098] a pasteurizing heat exchanger for exchanging heat between
the flow of liquid product and a flow of fluid, preferably water,
so as to heat or cool the liquid product during the passage thereof
through the pasteurizing heat exchanger
[0099] first conduit means for introducing the flow of liquid
product at a product inlet temperature into an inlet of the
pasteurizing heat exchanger,
[0100] second conduit means for introducing the flow of fluid at a
fluid inlet temperature into the pasteurizing heat exchanger,
[0101] third conduit means for discharging the flow of liquid
product from an outlet of the pasteurizing heat exchanger at a
product outlet temperature
[0102] one or more heat recuperating or regenerative heat
exchangers for exchanging heat between the unpasteurized liquid
product flowing through said first conduit means into the
pasteurizing heat exchanger and the pasteurized liquid product
flowing through said third conduit means from the pasteurizing heat
exchanger so as to cool the pasteurized liquid product, pre-heat
the unpasteurized liquid product to product inlet temperature and
recuperate heat energy from the pasteurized liquid product,
[0103] the lengths of said first and third conduit means extending
between the pasteurizing heat exchanger and the one or more
regenerative heat exchangers being substantially as short as
possible so as to minimize the volume of liquid product that is not
in heat exchange relationship with a flow of said fluid.
[0104] Preferably, the apparatus according to the invention further
comprises one or more additional pasteurizing heat exchangers
comprising the features of the above mentioned pasteurizing heat
exchanger, all the pasteurizing heat exchangers being arranged in
series and having intermediate conduits for conducting the flow of
liquid product from the outlet of one pasteurizing heat exchanger
to the inlet of the succeeding pasteurizing heat exchanger, and the
lengths of said intermediate conduits being substantially as short
as possible so as to minimize the volume of liquid product that is
not in heat exchange relationship with a flow of fluid.
[0105] The invention furthermore concerns an apparatus for the
pasteurizing of liquid products in a continuous flow, the apparatus
consisting of:
[0106] a regenerative part into which the product is fed by a
supply pump, and
[0107] a pasteurizing part to which the product is led from the
regenerative part and from which pasteurizing part the product is
led back to the regenerative part, both the regenerative part and
the pasteurizing part consisting of heat exchangers.
[0108] The invention also concerns a method for the pasteurizing of
liquid products in a continuous flow and comprising the following
steps:
[0109] providing a regenerative part of a pasteurizing apparatus
and a pasteurizing part of said pasteurizing apparatus, both the
regenerative part and the pasteurizing part consisting of heat
exchangers,
[0110] feeding product into the regenerative part,
[0111] leading the product from the regenerative part to the
pasteurizing part,
[0112] leading the product from the pasteurizing part back to the
regenerative part,
[0113] heating the product in the regenerative part by transfer of
heat from the product led back to the regenerative part from the
pasteurizing part.
[0114] In the manufacture of products which can be spoiled by
bacteria, especially within the foodstuffs industry, it is commonly
known to destroy the bacterial flora by pasteurization, which is a
heat treatment which kills the harmful bacteria by exposing them to
higher temperatures than they can tolerate.
[0115] The effect of the pasteurization is measured in PU and
depends on the temperature which is used, and on the time for which
the product is exposed to this temperature.
[0116] However, the product is also damaged by intense heating, and
demands are therefore placed on the heat treatment with regard to
time and temperature.
[0117] Such a pasteurization of a continuous flow of a liquid
product is known e.g. from the brewing industry, in the form of
beer or similar products which must later be containerised, for
example in bottles.
[0118] The product to be pasteurized can either be pasteurized
before it is transferred to smaller containers, or after the
containers have been filled.
[0119] The following description deals only with a pasteurization
process which takes place before the product is transferred to
smaller containers, a so-called plate pasteurization.
[0120] The product flow through a plate pasteurization apparatus
will normally take place in the following manner: The product flows
into a plate heat exchanger's regenerative part, where energy is
exchanged between the cold product on the way in and the hot
already-pasteurized product on its way out. The product is thus
first heated in the regenerative section, after which it is pumped
into the next section of the heat exchanger where it is heated to
the pasteurization temperature.
[0121] The product is now led out into a "holding pipe", the length
and flow rate through which is determinative of the pasteurization
time. Out of regard for space, the holding pipe is often configured
as en elongated spiral. When the product has passed through and
reaches the end of the holding pipe, the product has been
pasteurized and it is led into the second chamber in the
regenerative part of the heat exchanger, where it is cooled down to
the discharge temperature by the cold product flowing into the heat
exchanger.
[0122] The pasteurized product can now be filled into a container.
In order to adjust the capacity between the filling plant and the
pasteurization apparatus, there is often introduced a flow-control
valve and a buffer tank.
[0123] Moreover, use can be made of a cooler if it is desired to
further reduce the discharge temperature.
[0124] A stop in production can occur if other machines, such as
e.g. the filling plant or the bottling machine are stopped. A stop
in the production line is a problem for a plate pasteurization
apparatus, which is dependent on a continuous process in order to
achieve the correct processing. During a stoppage, the product in
the holding pipe, which has the pasteurization temperature, will
not have the possibility of being cooled down.
[0125] Consequently, the product becomes over-pasteurized and will
normally be discarded before the line is re-started.
[0126] A second problem is to achieve the correct temperatures when
the line is re-started. The regenerative section will have the
average temperature between the cold and the hot product, while at
the same time the supply of heat to the heating section is closed
down. Therefore, the "new" product must be discarded until the
temperature is correct, or it must be replace by water which is
also discarded.
[0127] These circumstances result in a loss of resources and not
least in a delay in the re-starting of the production. Therefore,
the above-mentioned buffer tank will often be introduced after the
plate pasteurization apparatus. This buffer tank will normally be
capable of containing up to half an hour's production, and can
hereby reduce the number of stoppages of the plate pasteurization
apparatus.
[0128] Another way in which this problem can be solved is to
provide the plate pasteurization apparatus with a by-pass. Compared
with the simple plate pasteurization apparatus, here there is
introduced an extra valve which can open for the circulation, so
that the pasteurized product can again be used as input to the
plate pasteurization apparatus. The function of the cooler during
the by-pass is to cool the pasteurized product down to the normal
input temperature, so that the temperature balance is maintained
through the whole of the plate pasteurization apparatus.
[0129] The result is that the same product is pasteurized again and
again and therefore becomes over-pasteurized. For this reason, the
plate pasteurization apparatus will often be filled with water just
before it goes into by-pass. Before re-starting, the water must
again be replaced by the product. This procedure takes time and
results in a great consumption of water and a certain product
wastage, which means that a large buffer tank after the plate
pasteurization apparatus is necessary in order to reduce the number
of times the production line is stopped.
[0130] The use of a by-pass also has the result that during a
stoppage, continuous use is made of the same energy for heating as
during operation. Moreover, a corresponding energy is used for the
cooling of the product or the water which is circulated.
[0131] It is therefore the object of the invention to provide a
method for avoiding the disadvantages of space-demanding equipment
and resource demanding procedures and to avoid product wastage by
over-pasteurization.
[0132] This object is achieved by a method of the kind disclosed in
the introduction, said method according to the invention being
characterized in heating the product to the pasteurization
temperature in the pasteurizing part and cooling the product down
in the pasteurizing part in the event of a production stop by
supplying hot or cold water, respectively, to the pasteurizing
part, and controlling the pasteurization process by means of
temperature sensors placed before and after the pasteurizing
part.
[0133] By this method it is ensured that pasteurization can take
place without a great waste of the product and of substitution
water and a high consumption of energy during an operational
stoppage, in that during the stoppage it is not necessary to
replace the product with water. At the same time, it is also
ensured that no under-pasteurization of the product occurs, and
that over-pasteurization is limited to the greatest possible
extent.
[0134] The method also ensures that it is possible for production
to take place without a buffer tank between the pasteurization
apparatus and the filling machine, or with a possible buffer tank
with very small volume.
[0135] The invention also concerns an apparatus for execution of
the method and of the kind disclosed in the introduction, said
apparatus according to the invention being characterised in that it
further comprises a mixing valve for supplying hot or cold water to
the pasteurizing part, so that the pasteurizing part cannot only
heat the product to the pasteurization temperature, but also cool
the product down in the event of a stop in production, and
temperature sensors placed before and after the pasteurizing part
for controlling the pasteurization process..
[0136] This apparatus results in a considerable saving in space, in
that despite the introduction of a further heat exchanger, space is
saved for both holding pipe and for the buffer tank. Moreover,
since there is no continuous consumption of energy for heating and
cooling during a stop in production, a saving in energy is
achieved.
[0137] Furthermore, a more simple cleaning of the apparatus is
achieved, i.e. Central Inplace Cleaning, in that the construction
does not include extra pipe loops or pipe ends without flow.
Moreover, the buffer tank is very small or can be omitted
completely, which all-in-all will save large amounts of CIP liquids
and CIP-installations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0138] In the following, the methods and the apparatus according to
the present invention will be described more in detail by way of
example only and with reference to the accompanying drawings
where:
[0139] FIG. 1 shows a diagrammatic view of a conventional
pasteurizer for liquid products such as beer,
[0140] FIG. 2 shows a similar view of another conventional
pasteurizer for liquid products such as beer,
[0141] FIG. 3 shows a diagrammatic view of an embodiment of a
pasteurizer according to the invention, the view being simplified
so as to render the principle of the invention more clear,
[0142] FIGS. 4-5 taken together show a diagrammatic view of an
embodiment similar to the one shown in FIG. 3, but more in detail
and showing more of the elements comprised by the pasteurizer and
forming part of the monitoring and control system for PU uptake
according to the invention, FIGS. 4 and 5 being intended for being
viewed together by matching the references A and B in the two
Figures,
[0143] FIG. 6 shows diagrammatic vertical elevational view of a
pasteurizing heat exchanger with one zone and two strokes, i.e.
corresponding for example to section 18 in FIGS. 3 or 4,
[0144] FIG. 6a shows a flow-diagram illustrating the flow paths of
beer and water through a series of two-stroke heat exchangers,
[0145] FIG. 7 shows an enlarged view of a detail of the heat
exchanger in FIG. 6,
[0146] FIG. 8 is an illustration of the parameters determining the
heat transfer and PU-uptake in the heat exchanger shown in FIG.
6,
[0147] FIG. 9 is a simplified diagrammatic graph showing the result
of the conventional pasteurizers' control system for controlling
the uptake of PU's,
[0148] FIG. 10 is an illustration similar to FIG. 9 illustrating
the result of a PU-control system according to the invention,
[0149] FIGS. 11 and 12 show graphs similar to FIGS. 9 and 10 for
two different flow-rates of beer, FIG. 11 for 380 hl/hr and FIG. 12
for 120 hl/hr, the temperature of the beer at various positions
through the pasteurizer also being shown,
[0150] FIG. 13 is a table showing values for beer temperature,
PU-uptake, heat treatment, number of finite elements and
end-of-zone positions,
[0151] FIG. 14 is a graph similar to FIGS. 11 and 12 showing a
simulated situation where an anomaly in the flow of liquid product
has taken place and how the control system reacts,
[0152] FIG. 15 shows a block diagram of control loops for
controlling the PU-uptake according to the invention,
[0153] FIGS. 16 and 17 are isometric views from two sides of a
pasteurizing apparatus according to the invention.
[0154] FIG. 18 shows a diagrammatic view of another embodiment of a
pasteurizing apparatus for the pasteurization of liquid products in
a continuous flow,
[0155] FIG. 19 shows a diagrammatic view of a pasteurizing
apparatus as shown in FIG. 1, but with two regenerative zones and
three pasteurizing zones, and
[0156] FIG. 20 shows a diagrammatic view of a pasteurizing
apparatus as shown in FIG. 19, but with re-circulation in the
regenerative part.
DETAILED DESCRIPTION OF THE INVENTION
[0157] Referring now to FIG. 1, the illustrated plate pasteurizer
comprises a plate heat exchanger consisting of two sections, a
regenerative or heat recuperating section 2 and a heating section
3. The plate pasteurizer further comprises a so-called holding pipe
4, a liquid product feed pump 5, a booster pump 6, a temperature
sensor 7, a flow control valve 8, a not shown buffer tank and a not
shown filling apparatus for filling the pasteurized liquid product
into containers. Hot water is supplied to the heating section 3 of
the plate heat exchanger in a not shown manner such that heat
exchange may take place between the hot water and the liquid
product in the section 3. The cold liquid product is supplied to
the regenerative section 2 by means of the feed pump 5, and hot
pasteurized liquid product is also supplied to the regenerative
section 2 in counter-flow with the cold unpasteurized liquid
product so that the cold liquid product is pre-heated and the hot
pasteurized product is cooled by recuperating the heat from the hot
product and transferring it to the cold product.
[0158] The thus pre-heated product is transferred to the heating
section 3 by means of the booster pump 6, and the product is heated
up to a predetermined pasteurizing temperature by means of heat
exchange in section 3 with the hot water supplied in counter-flow
to said section. The temperature of the heated product supplied to
the holding pipe 4 is monitored by the temperature sensor 7 so that
the pre-determined temperature of the heated product may be
maintained by altering the temperature of the hot water supplied to
the heating section as a function of the rate of flow of the
product through the pasteurizer. The length of the holding pipe 4,
which often is configured as an elongate helix, together with the
rate of flow and the temperature of the heated product will
determine the amount of pasteurizing units, PU's, that is taken up
by the product during its passage through the holding pipe.
[0159] When the product exits the holding pipe 4 it is assumed to
have taken up the required amount of PU's for the degree of
pasteurization desired. The product is conducted into the
regenerative regenerative 2 where it is cooled to the exit
temperature by transferring heat to the cold product in
counter-flow. The pasteurized product may then be transferred to
the filling station to be filled into containers.
[0160] To coordinate the capacity of the filling station with the
capacity of the pasteurizer, the flow-control valve 6 and the not
shown buffer tank are utilized.
[0161] If a production stop occurs, for instance if other machines
such as the filling station or a succeeding packing station stops,
this constitutes a problem for the conventional pasteurizing
apparatus shown in FIG. 1 which is dependent on a continuous
process to achieve the correct heat treatment of the product.
[0162] During stop there will be no possibility of cooling the
product in the holding pipe 4 and therefore the product therein
will remain at the pasteurizing temperature. The product will
therefore be over-pasteurized and will normally be discarded before
re-starting the pasteurizer.
[0163] Another problem is to attain the correct temperatures of the
product and in the rest of the system during re-start. The
regenerative section 2 has the average temperature between the cold
and the hot product at the same time that heat supply to the
heating section 4 is closed down. Therefore, the "new" product must
be discarded until the temperature measured by the temperature
sensor is correct, or alternatively, the product must be replaced
by water which is also discarded.
[0164] The above causes waste of resources and, not least, delays
re-start of the production. These problems can be reduced by
utilizing a buffer tank with a large capacity after the plate
pasteurizer. If the buffer tank, as is normal, contains up to 30
minutes of production, the number of stops of the pasteurizer may
be reduced. However, the size of the buffer tank may not be very
large because of space constraints and loss of the contents thereof
at the end of the working day.
[0165] This conventional pasteurizer furthermore has a very simple
system for controlling the amount of PU's taken up by the liquid
product. The PU-control system consists in measuring the
temperature at the inlet of the holding pipe by means of the
temperature sensor and supposing that all the liquid product in the
pasteurizer will be treated correctly. If one or more portions of
the product have been under-pasteurized, for instance in connection
with a stop, the control system will have no possibility of
reacting to ensure that all portions of the liquid product have
received the required amount of PU's. It is very important that all
portions of the product be pasteurized correctly, as otherwise
serious quality problems will arise.
[0166] Referring now to FIG. 2, the pasteurizer 1 comprises a
regenerative section 2, a heating section 3, a holding pipe 4, a
feed pump 5, a booster pump 6, a temperature sensor 7 and a
flow-control valve 8. This pasteurizer further comprises a cooling
section 9 and a bypass valve 10. The bypass valve 10 may open for
circulation such that the pasteurized product exiting from the
cooling section 9 may be used as input to the pasteurizer
again.
[0167] During bypass the function of the cooling section 9 is to
cool the pasteurized product down to the normal input temperature
such that the temperature balance through the entire pasteurizer
may be maintained. This entails that the same product is
pasteurized again and again and therefore becomes over-pasteurized.
Therefore, the pasteurizer will often be filled with water just
before it is stopped. Before re-start, the water is to be replaced
by the product again. This procedure takes time and entails a large
consumption of water. Therefore it is necessary to have a quite
large buffer tank after the pasteurizer to reduce the number of
stops of the pasteurizer.
[0168] The bypass furthermore entails that during a stop the same
energy as during normal operation is used to heat and additional
corresponding energy is used to cool the product or the water that
is being circulated.
[0169] This pasteurizer with bypass has the same simple PU-control
system as the pasteurizer shown in FIG. 1 and therefore it has the
same disadvantages.
[0170] In connection with such heat exchanger pasteurizers having a
holding pipe wherein the pasteurization takes place, a PU-control
system may be based on the following suppositions:
[0171] The temperature is constant during the whole course of the
pasteurizing treatment.
[0172] The region of the pasteurizer wherein PU's are taken up by
the liquid product, i.e. the holding pipe, is constant so that the
volume of the product taking up PU's is constant.
[0173] When suppositions 1.1 and 1.2 are complied with and when the
temperature T and the flow are known, the PU-uptake can be
calculated according to the following equation:
PU=volume/flow*exp((T-X)/Z),
[0174] where X and Z are constants.
[0175] The PU's taken up, the temperature and the rate of flow are
controlled in three control loops:
[0176] The level in the buffer tank is compared with the desired
value for the level. The desired rate of flow is calculated by
means of a regulator.
[0177] Based on the desired rate of flow, the desired PU's and the
constant treatment volume, a desired temperature is calculated. The
temperature is altered very slowly so as to maintain supposition
1.1, i.e. that the temperature is constant throughout the entire
holding pipe.
[0178] The rate of flow is regulated such that the error between
the calculated and the desired PU-uptake is minimized, i.e. the
rate of flow is increased to reduce PU-uptake or the rate of flow
is decreased to increase the PU-uptake.
[0179] This control system is based on averages and cannot
compensate for anomalies in the operation or anomalous conditions
in connection with a stoppage or a re-start so that no security is
to hand that all portions of the liquid product have taken up the
desired amount of PU's. In connection with pasteurizing of beer
where over-pasteurization is quite detrimental to the quality of
the beer as regards taste, it is desirable to ensure that the
required amount of PU's is taken up without over-pasteurizing the
rest of the beer more than absolutely necessary.
[0180] This is an important aspect of the present invention whereby
it is ensured that all portions of the liquid product to be
pasteurized have received the desired amount of PU's without
subjecting the rest of the liquid product being pasteurized to more
over-pasteurization than absolutely necessary.
[0181] Referring now to FIG. 3 and to a certain extent to FIGS.
4-5, the pasteurizer according to the present invention comprises a
heat recuperating or regenerative heat exchanger 11 comprising two
zones 12 and 13 into which cold beer is introduced by means of a
feeding pump 14, the cold beer being pre-heated in zones 12 and 13
of the regenerative heat exchanger 11 by exchanging heat with hot
pasteurized beer flowing in counter-flow through the heat exchanger
11. The pre-heated beer is conducted to a pasteurizing heat
exchanger 15 through a conduit 16 by means of a booster pump
17.
[0182] The pasteurizing heat exchanger comprises four double stroke
plate heat exchanger sections 18-21 arranged in series. Each of the
sections 18-21 is connected to supplies of hot and cold water from
not shown sources of hot and cold water through a conduit 22. The
hot and cold water flows through the sections 18-21 so as to heat
or cool, respectively, the beer flowing in counter-flow thereto.
Throttle valves 23-26 regulate the flow of either cold or hot water
through each of the sections 18-21, respectively.
[0183] The heated and pasteurized beer is transferred from the
outlet of the pasteurizing heat exchanger section 21 to an inlet of
the regenerative heat exchanger section 13 by means of a conduit
27. The cool beer leaves an outlet of the regenerative plate heat
exchanger section 12 and is directed to a cooling heat exchanger 28
wherein the beer is cooled to a temperature suitable for being
filled into containers. From the cooling heat exchanger 28 the cool
beer is transferred to a beer buffer tank 29 and from the beer
buffer tank by means of an output pump 30 to a not shown filling
device. Temperature sensors T1, T2 . . . T10 are arranged along the
flow of beer for monitoring the temperature of the beer at
different points along the flow path of the beer through the
pasteurizer.
[0184] The conduit 16 and especially the conduit 27 are as short as
possible so that the volume of beer in a region without possibility
of regulating the temperature of the beer is kept to a minimum. It
is especially important that the connecting conduit between the
pasteurizing section 21 and the regenerating section 13 is as short
as possible because the temperature of the beer is highest
here.
[0185] Contrary to all the known pasteurizing devices, the
pasteurizer according to this invention has no holding tube in
which the pasteurizing takes place. It could be argued that the
conduits 16 and 27 are short holding tubes, but according to the
invention the function of a holding tube in conventional
pasteurizers is not desirable in the pasteurizer according to the
invention for the reasons set out above.
[0186] Even though a small proportion of the required PU's is taken
up by the beer in the regenerating heat exchanger section 13, the
great majority of the PU's taken up by the beer takes place in the
pasteurizing heat exchanger 15 where the temperature can be
regulated both upwards and downwards such that, as will be
explained in the following, a PU-control system can be implemented,
that can ensure that all portions of the beer flow have taken up
the required amount of PU's.
[0187] If the conditions during operation, during a stoppage or
during a re-start after a stoppage require a regulation of the
temperature of the beer in the pasteurizing heat exchanger 15, the
temperature of the beer may be regulated by heating or cooling the
beer in the sections 18-21 as is required by the PU-control system
chosen for a particular application.
[0188] In broad terms, during normal operation anomalies may occur
giving rise to variations in the flow-rate of the beer which will
require a fine-tuning of the temperatures in the sections 18-21, or
a total stop of the operation may be required because of for
instance stoppage of the filling station and excessive filling of
the buffer tank 29, and this latter situation requires more radical
regulation of the temperature of the beer in various parts of the
pasteurizer. When re-starting after a stop or at the beginning of a
working day, more radical regulation of the temperature of the beer
must also take place.
[0189] All the necessary regulations of the temperature of the beer
can be carried out by supplying either hot water or cold water to
various or all of the pasteurizing heat exchanger sections 18-21
and/or by varying the rate of flow of the beer. When a stoppage
occurs, it is for example necessary to cool the beer in the
pasteurizing heat exchanger according to a certain procedure, the
simplest procedure being to cool the beer in all the sections 18-21
by supplying cold water to the sections so as to cool the beer
therein.
[0190] Another procedure could be to continue the flow of beer for
a small period of time corresponding to the volume of beer in the
last pasteurizing heat exchanger section 21 and solely cooling the
beer in said section 2 1. Thereby cooler beer that does not take up
PU's is transferred to the regenerator section 13 and no
over-pasteurization of this volume will take place.
[0191] If the stop is of a longer duration, a cooling of the
sections 20-18 takes place to a temperature reducing or totally
eliminating the uptake of PU's in said sections so as to avoid
over-pasteurization in said sections. It will be clear to those
skilled in the art that many different PU-control procedures may be
applied depending on the circumstances, the duration of the
stoppage, reduced capacity of the filling station etc.
[0192] When re-starting after a stop or a sharp reduction in the
flow rate of the beer, various strategies may be adopted because of
the various possibilities of regulating the temperature in the
pasteurizing sections 18-21.
[0193] Normally, the first pasteurizing section 18 will be heated
to a higher temperature than under normal operation so as to ensure
that a sufficient number of PU's may be taken up by the first
portion of beer pasteurized after a stop. However, this depends on
the temperature of the beer in the rest of the pasteurizer sections
19-21 and other factors such as allowable flow and therefore
different strategies may be adopted or a combination of strategies
may be adopted so as to ensure that all portions of the beer has
taken up the required amount of PU's.
[0194] Referring now to FIGS. 4 and 5, a more detailed view of the
pasteurizing apparatus according to the invention shown in FIG. 3
is illustrated, there also being a difference as regards the flow
regulation of cold and hot liquid to the four pasteurizer sections
18-21. The difference consists in that in the embodiment according
to FIGS. 4-5 hot water may be supplied from a hot water tank 31 to
the zones 18-20 simultaneously or to zones 18-21 simultaneously
while cold water may be supplied from a cold water tank 32 either
to all zones 18-21 or solely to zone 21.
[0195] In the following a list is given of the various positions of
the various elements shown in FIGS. 4-5, the position number being
indicated by a numeral in a circle, the corresponding explanation
as regards function and capacity being given including an item No.
which refers to the same type of element, for instance item No. 13
is a temperature sensor with a maximum of 75.degree. C.
[0196] Flow Positions
1 Pos PosName Item 1 Feeding pump 2 Beer Pump, 200 hl/h, 9,2 bar 2
Pressure Isolation 3 Shut off Valve 3 Infeed flow 1 Flow Meter,
beer 0-200 hl/h 4 Conductivity 30 Conductivity Sensor 5 T supply 13
PT100 Sensor, Tmax = 75.degree. C. 6 Infeed Pressure 10 Pressure
sensor 0-10 bar 7 Reg. 1/8 4 Heat Exchanger, Regenerative A = 35 m2
8 T Zone 1 13 PT100 Sensor, Tmax = 75.degree. C. 9 Reg. 2/7 4 Heat
Exchanger, Regenerative A = 35 m2 10 Booster Pump 5 Beer Pump, 200
hl/h, 2,2 bar 11 T Zone 2 13 PT100 Sensor, Tmax = 75.degree. C. 12
T Zone 3 13 PT100 Sensor, Tmax = 75.degree. C. 13 Tref Zone 3 13
PT100 Sensor, Tmax = 75.degree. C. 14 T Zone 4 13 PT100 Sensor,
Tmax = 75.degree. C. 15 Tref Zone 4 13 PT100 Sensor, Tmax =
75.degree. C. 16 T Zone 5 13 PT100 Sensor, Tmax = 75.degree. C. 17
Tref Zone 5 13 PT100 Sensor, Tmax = 75.degree. C. 18 Zone 3 (past)
7 Heat Exchanger, Pasteurizing 19 Zone 4 (past) 7 Heat Exchanger,
Pasteurizing 20 Zone 5 (past) 7 Heat Exchanger, Pasteurizing 21
Zone 6 (past) 7 Heat Exchanger, Pasteurizing 22 T Zone 6 13 PT100
Sensor, Tmax = 75.degree. C. 23 Tref Zone 6 13 PT100 Sensor, Tmax =
75.degree. C. 24 Past. Pressure 10 Pressure sensor 0-10 bar 25 T
Zone 7 13 PT100 Sensor, Tmax = 75.degree. C. 26 T Zone 8 13 PT100
Sensor, Tmax = 75.degree. C. 27 Output cooler 21 Heat Exchanger
Glycol/Beer 28 T output 13 PT100 Sensor, Tmax = 75.degree. C. 29
Beer flow control 9 Control Valve, Beer 30 Pressure sensor 10
Pressure sensor 0-10 bar 31 Pressure Isolation 3 Shut off Valve 32
Flow out 1 Flow Meter, beer 0-200 hl/h 33 Filler Flow 1 Flow Meter,
beer 0-200 hl/h 40 Fresh Water to hot tank 14 Ball Valve, On/Off 41
Hot Water Buffer Tank 16 Tank, Water, 10 hl, Open 42 Cleaning
Nozzle 31 Tank Cleaning Nozzle 43 Hot Water Level 32 Tank Level
(Pressure) 44 Drain Cold Tank 14 Ball Valve, On/Off 45 Clean Hot
Tank 37 Manual Ball Valve 46 Shut off Hot Water 37 Manual Ball
Valve 47 Water pump 17 Pump, Water, 1200 hl/h, 2 bar 48 HE Hot
Water 18 Heat Exchanger, Steam/water. 49 T Water 13 PT100 Sensor,
Tmax = 75.degree. C. 50 Hot by-pass 14 Ball Valve, On/Off 51
Heating all zones 14 Ball Valve, On/Off 52 Flow zone 3 38 Flow
meter for water 0-1000 hl/h 53 Flow zone 4 38 Flow meter for water
0-1000 hl/h 54 Flow zone 5 38 Flow meter for water 0-1000 hl/h 55
Flow zone 6 38 Flow meter for water 0-1000 hl/h 56 Cooling all
zones 14 Ball Valve, On/Off 57 Cooling Zone 6 14 Ball Valve, On/Off
58 T Cold Water 13 PT100 Sensor, Tmax = 75.degree. C. 59 Heat
Exchanger Glycol/ Water 26 Heat exchanger, Glycol/Water 60 Shut off
Hot Water 37 Manual Ball Valve 61 Clean Hot Tank 37 Manual Ball
Valve 62 Cold Water Level 32 Tank Level (Pressure) 63 Cold
Circulation Pump 17 Pump, Water, 1200 hl/h, 2 bar 64 Cleaning
Nozzle 31 Tank Cleaning Nozzle 65 Cold Water Buffer Tank 16 Tank,
Water, 10 hl, Open 66 Fresh Water to cold tank 14 Ball Valve,
On/Off 67 Cold by-pass 14 Ball Valve, On/Off 68 Cold return Zone 6
14 Ball Valve, On/Off 69 Cold return all Zones 14 Ball Valve,
On/Off 70 Hot return all zones 14 Ball Valve, On/Off 71 Drain Hot
Tank 14 Ball Valve, On/Off 72 T Cold Tank 13 PT100 Sensor, Tmax =
75.degree. C. 73 T Cold Tank 13 PT100 Sensor, Tmax = 75.degree. C.
80 Glycol Shut Off 37 Manual Ball Valve 81 Glycol Shut Off 37
Manual Ball Valve 82 Glycol control valve 22 Control valve 3-way,
Glycol 83 Glycol pump 23 Glycol circulation pump 84 Glycol Shut Off
37 Manual Ball Valve 85 Glycol Shut Off 37 Manual Ball Valve 86
Glycol control valve 22 Control valve 3-way, Glycol 87 Glycol Pump
23 Glycol circulation pump 88 Condensate Shut Off 37 Manual Ball
Valve 89 Steam Trap 20 Steam Trap 90 Water Take Out, Steam 36 Water
Take OUT, Steam 91 Steam Shut Off 37 Manual Ball Valve 92 Strainer
Steam 35 Strainer for Steam 93 Steam Trap 20 Steam Trap 94 Steam
valve 19 Control valve, Steam
[0197] Those skilled in the art will readily understand the
possibilities of regulating flows and temperatures on the basis of
FIGS. 4-5 and the above listing of elements.
[0198] However, those skilled in the art will also readily
understand that many modifications are possible as regards the
number of sections or zones in the pasteurizing heat exchanger, the
number of regenerative zones, the combination possibilities of
supplying cold and hot water to the various zones in the
pasteurizing heat exchanger and possibilities of adding special
heat exchangers for special purposes.
[0199] Those skilled in the art will readily appreciate that the
more temperature and flow sensors are installed in the system, the
better the possibilities are of monitoring and controlling the
uptake of PU's by the liquid product being pasteurized. The
important features to keep in mind when modifying or supplementing
the shown and described embodiments of a pasteurizing apparatus
according to the invention are that the great majority of the
uptake of PU's by the liquid product should take place in the
pasteurizing zone, and the volume of liquid product contained in
the conduits 17 and 27 leading to the regenerative zones 12 and 13
should be as small as possible.
[0200] In the following, methods according to the invention for
monitoring and controlling the pasteurizing process will be
explained, it being understood that said methods may be applied to
many different configurations of pasteurizing apparatus according
to the invention and in fact for some of the methods also to
conventional pasteurizing apparatus having a holding pipe wherein
the pasteurizing takes place without possibility of regulating the
temperature during said pasteurization.
[0201] The methods according the invention for monitoring and
controlling the uptake of PU's by the liquid product to be
pasteurized are based on establishing a mathematical model of the
apparatus and measuring temperatures and rates of flow at different
points of the apparatus such as indicated in FIGS. 4-5 and defining
a number of other points or sections of the flow-paths of the
liquid product and/or the flow-paths of the heat transfer fluids.
By applying the mathematical model containing parameters for the
heat transfer at the different points or sections, the uptake of
PU's by the volume of liquid product in said sections or points may
be calculated such that the total uptake of PU's by said volumes
may be monitored and controlled throughout the pasteurizing
process.
[0202] Referring now to FIGS. 6 and 7, a plate heat exchanger 18
with two strokes has channels between thin vertical plates 33
having an embossed pattern, the plates defining channels for
heating or cooling water and for beer. The plate heat exchanger 18
is a well-known conventional plate heat exchanger. The beer and the
water flow through the heat exchanger in mutual counter-flow so as
to afford the most efficient heat exchange between the beer and the
water.
[0203] For the purposes of the mathematical model mentioned above,
the heat exchanger 18 is considered as consisting of a number of
sections, cells or finite elements as shown in FIG. 7, where finite
element n is bounded by two cross-sections through an entire stroke
of the heat exchanger such that the volume in said finite element n
of water and beer, respectively, is considered for that finite
element. The number of finite elements into which each stroke or
for that matter the entire heat exchanger may be considered as
being sub-divided for the purposes of the mathematical model is
chosen considering a trade-off between the accuracy of the
mathematical model and the calculation of the PU-uptake for each
volume of beer in each finite element and the calculating capacity
of a computing means employed to perform the necessary calculation
with a frequency also determined by such a trade-off.
[0204] The element n contains beer from all the beer plate spaces
in one stroke and water from all the plate spaces in the same
stroke as well as the stainless steel of all the plates in the
stroke comprised between said boundaries. It is supposed that the
temperature of the beer, of the water and of the steel plate does
not vary across the stroke, i.e. that the flow of beer and water is
evenly distributed in all the channels. Therefore the volumes of
beer and water and steel may be added together within the
boundaries of given element n.
[0205] Referring now to FIG. 6a, the flow of beer and water through
the system of heat exchangers shown in FIGS. 3, 4 and 5 so as to
illustrate the flow of water and beer through the system in another
way.
[0206] Referring now to FIG. 8, the volume Vb of beer, Vp of steel
plate, Vw water represents the total volume of beer, plate and
water within the boundaries of element n. Therefore each
calculation element is characterized by a constant beer volume
(VB), water volume (VW) separated by a plate with width equal to
the thickness of a single plate and an area corresponding to the
areas of all the plates in the element n, as well as a heat
transfer coefficient. The element has four operational data,
accumulated PU-uptake (PU) for the beer, the temperature of the
beer (Tb), the temperature of the water (Tw) and the temperature in
the center of the plate (Tp). Each element furthermore contains the
PU-values of a number of ideal PU-curves (ideal set curve 1-X) for
a number of ideal curves as discussed in the following.
[0207] The heat transfer coefficient is calculated based on a
supposition that both the flow of water and beer is very turbulent
and thereby maintains the same temperature in the whole element.
The heat transfer thus consists of a heat transmission from beer to
the plate, a heat transmission through the plate to the center of
the plate, a heat transmission from the center of the plate to the
surface of the plate and a heat transmission to the water. This is
shown by the temperature gradient uppermost in FIG. 8 and the
arrows at the bottom part of FIG. 8. The heat transfer coefficient
is determined by experiments as a function of beer flow-rate and
water flow-rate as will be explained in the following in connection
with the explanation of the "adaptive adjustment of the heat
transfer coefficient".
[0208] The calculation of the operational data in the elements is
updated for each sample (calculation cycle). The calculation is to
be performed as often as necessary to be able to suppose that the
heat transmission is constant, i.e. that the temperatures only
change slowly compared to the frequency of sampling or
calculation.
[0209] After each calculation/sample the liquid and fluid volumes
are moved a number of finite elements in the flow direction
corresponding to the measured flow and the frequency of
calculation/sampling. The calculated number of elements that the
volumes are to be moved in the flow-direction is rounded up or down
to the closest integral number. The error introduced by this
rounding up or down is stored and is added to a next calculation
before said calculation is rounded up or down, and so on.
[0210] The calculation is carried out as follows for each finite
element and for each sample/calculation:
[0211] Calculate the heat transmission from beer to plate based on
the start temperatures.
[0212] Calculate the heat transfer from the plate to water based on
the start temperatures.
[0213] Calculate the total energy transmission in the course of one
sample (3.1 and 3.2 are assumed to be constant during the sampling
period).
[0214] Calculate PU-uptake and add same to the accumulated value of
PU-uptake for the finite element in question.
[0215] Calculate the PU-error as the difference between the actual
PU-value and an ideal PU-value.
[0216] Calculate the new temperatures of the beer, the water and
the plate.
[0217] Move the beer (Tb, PU) and the water (Tw) a number of finite
elements in the flow-direction thereof corresponding to the
respective flow-rates thereof.
[0218] The above calculation sequence is repeated for each element
and for each sample.
[0219] In this manner data is constantly generated for allowing
monitoring of the PU-uptake of all the volumes defined by the
finite elements n such that various strategies for controlling the
pasteurizing process may be implemented.
[0220] The "adaptive adjustment of the heat exchange coefficients"
mentioned above takes place as described in the following.
[0221] The heat transfer coefficient can be determined by operating
the pasteurizing apparatus while adjusting the heat transfer
coefficient with the purpose of minimizing the difference between
the calculated and the measured output temperatures at the
discharge of each heat exchanger. Manual adjustment of the heat
transfer coefficient can be done during commissioning or at any
time in order to minimize the errors. Adaptive adjustment (auto
tuning) can be done during normal operation or in a specially
designed start-up sequence. The purposes of a regular adaptive
adjustment of the heat exchange coefficients are:
[0222] Adapt to any minor changes in the system due to scaling,
wear etc.
[0223] In case of a major change in the coefficients, the system
will go into alarm mode.
[0224] The development over time will provide information about
necessary cleaning and maintenance.
[0225] Referring now to FIGS. 9 and 10, the graphs therein
illustrate the uptake of PU by the liquid product as a function of
the position of the finite element along the flow-path of the
liquid product, in this case the number of finite elements being
300. In both graphs an ideal curve 34 for the uptake of PU's as a
function of the position of the portion of liquid product in
question along the path flow of the liquid product is shown. The
curve 35 shows the actual PU-uptake, and the dip 36 indicates a
certain volume of the liquid product that has received too few PU's
because of some anomaly such as a stop or a sharp reduction in
flow-rate of the liquid product. In the conventional control system
for conventional pasteurizers having a holding pipe, the
temperature will be measured at the entrance to the holding pipe
and it will be assumed that all beer in the pasteurizer will be
treated correctly. If an anomaly such as 36 occurs, the control
will not have any possibility to react and, as illustrated in FIG.
9, a certain volume 36 will be under-pasteurized when it exits the
pasteurizer.
[0226] In the control system according to the invention, an ideal
curve 34 is calculated for a given flow and the flow-rate of the
liquid product and/or of the heat transfer fluid as well as the
temperature thereof may be controlled such that the volume being
treated having the worst discrepancy as regards PU-uptake compared
with the ideal value is compensated for by increasing the PU-uptake
generally in the pasteurizer with a value just sufficient to bring
the volume with the worst discrepancy up to the ideal curve. The
control system according to the invention will calculate that there
is liquid product that does not follow the ideal curve and will for
instance decrease the flow-rate thereof until the worst portion is
on the ideal curve.
[0227] The ideal curve employed may be calculated or measured. The
measured ideal curve can be established in the following
manner.
[0228] The pasteurizer is operated with a constant flow until
thermal balance is obtained and the correct PU-uptake is calculated
in the simulation for the pasteurized beer. The calculated
PU-uptake value and the measured treatment temperature for all the
positions in the pasteurizer are stored in the computer whereby an
ideal curve is established.
[0229] Alternatively a calculated ideal curve can be used, the
calculated ideal curve being established by a simulation of the
system or a traditional calculation of the heat transfer.
[0230] It is necessary to use different ideal curves corresponding
to different flows as the shape of the curve changes with varying
flow-rate. This will be explained more detailed in the
following.
[0231] Referring now to FIGS. 11, 12 and 13, two different ideal
curves for a flow-rate of 380 hl/hr and 120 hl/hr 37, 38,
respectively, are shown for different positions along the flow-path
of the beer to be pasteurized, the flow-path being sub-divided into
1,600 finite elements. The number of PU's taken up is indicated
multiplied by 5 for better clarity. The graphs also show the
temperature of the beer as a function of the position along the
flow-path, i.e. in each of the 1,600 finite elements. The ends of
the two heating regenerating zones, the four pasteurizing zones and
the two cooling regenerative zones are shown with respect to the
position, i.e. the end of the first pasteurizing zone, reference
No. 18 in FIGS. 3 and 4 and "past.3" in the table in FIG. 13 is
positioned at position or finite element No. 640, and similarly,
the temperature curves 39 and 40 in FIGS. 11 and 12, respectively,
show that the temperature of the beer along the flow-path is
different for different flow-rates, and consequently, the ideal
curves for PU-uptake 37, 38, respectively, are also different.
[0232] The ideal curves may be calculated or measured. A measured
ideal curve can be established by operating the pasteurizer with a
constant flow until balance has been obtained, and the correct
PU-uptakes are calculated in the simulation for the pasteurized
beer. The calculated PU-uptake value and the measured heat
treatment temperature (the temperature of the water flowing in) for
all positions in the pasteurizer are stored in the memory of the
calculator whereby an ideal curve is established. Alternatively, a
calculated ideal curve can be employed, said calculated ideal curve
being established by simulating the pasteurizer or by a traditional
calculation of heat transmission.
[0233] For different flow-rates, a number of ideal curves and heat
treatment temperatures are stored, and the ideal curve and
treatment temperature corresponding to a specific flow-rate is
found by interpolating between the thus established ideal curves,
whether they be measured or calculated.
[0234] The table in FIG. 13 shows, as mentioned above, possible
ideal curves with a nominal flow-rate of 380 hl/hr, and 120 hl/hr
with a desired PU-uptake value of 10.
[0235] During stable operation at a certain flow-rate of beer, the
actual PU-uptake curve for the beer will follow the ideal curve for
that flow-rate. However, if for instance a stoppage occurs, several
strategies may be employed. For instance the flow-rate may be
reduced and the last pasteurizing zone (past.6) is cooled so that
the PU-uptake level in the first three zones are raised and at the
same time a colder pasteurized beer flow is created to the first
cooling regenerative zone (reg.7/2) having the highest
temperatures. During re-start after a stop all four pasteurizing
zones (past.6) may be used to heat at constant temperature such
that a "flat" curve results for ensuring that finite elements with
PU-uptake values higher than the required minimum holds back the
flow-rate from increasing.
[0236] As mentioned above, many different strategies may be
employed depending on the situation, the number of pasteurizing
zones, the required minimum PU-uptake, the character of the liquid
product to be treated and so on.
[0237] Referring now to FIG. 14, the graph shows the ideal curve
for a flow-rate of 380 hl/hr and the corresponding temperature
curve 39. The curve 40 shows the actual uptake of PU's after the
flow-rate suddenly is reduced from 380 hl/hr to 300 hl/hr. The
control system is then allowed to automatically adjust for this
sudden decrease in flow-rate and it can be seen from the curve 40
that the actual uptake of PU's is above the ideal curve at the
outlet of the last pasteurizing heat exchanger (past.6) while the
PU-uptake at the inlet to the first pasteurizing heat exchanger
(past.3) is very proximate to the ideal curve. The control method
or system according to the invention regulates the flow-rate of the
beer and of the heat transfer fluid such that the actual PU-uptake
curve 40 quickly moves back to coincide with the ideal PU-uptake
curve 38.
[0238] In the following, one embodiment of control loops pertaining
to the PU-uptake control method according to the invention will be
described in connection with FIG. 15, which is a block diagram of
three novel control loops for controlling a pasteurizer according
to the invention.
[0239] The control loops shown in FIG. 15 are applicable to the
pasteurizing apparatus shown in FIGS. 4-5.
[0240] Flow demand/set-point [4]:
[0241] The flow demand from the filler station [2] is added to the
flow demand form the level regulator in the buffer tank [1] [3]
[0242] Temperature set-point 1 (optimal) [6]
[0243] From the above flow demand the control will interpolate [5]
between the flow-value for the ideal curves and find the
corresponding temperature, called temp set-point 1 [6].
[0244] Temperature set-point 2 (limited) [8]
[0245] Limitations to temperature changes [7] are made in order to
ensure that the physical system can follow the setpoint 2 with a
small temperature error. This is important to ensure stable
temperatures and a stable PU-uptake.
[0246] Hot water temperature [9]
[0247] The regulator for the steam heat exchanger controls the
temperature of the hot water. The set-point for the regulator is
the above set-point 2 (limited) [8]
[0248] The ideal PU-curve [14] is interpolated [13] from the
temperature set-point 2 (limited) in order to make the ideal curve
match the actual conditions as well as possible.
[0249] The PU error [15] is found as the actual calculated value
[12] minus the interpolated ideal PU-value [14].
[0250] The most important PU error [15] is the smallest value of
the PU error present in the pasteurizer within the current sample
time.
[0251] The beer flow [18] is controlled by a regulator [16] which
uses the most important PU error (15) as input. If the most
important PU error is negative, the flow is reduced and if the
error is positive, the flow is increased.
[0252] Hereby an embodiment of an automatic PU-uptake control
system according to the invention has been described, but as
mentioned above, other possible control systems will be obvious to
those skilled in the art based on the principles of the
invention.
[0253] Thus, a much simpler control method could be by basing the
control system on a pre-determined sequence under certain anomalous
conditions while utilizing the monitoring method for PU-uptake
according to the invention such that for example under a stop, a
pre-determined sequence for closing down the flow of beer and
cooling of the pasteurizing zone may be utilized, the sequence
being developed based on a series of test runs where the finite
element mathematical model is used to monitor the result and ensure
that no beer is under-pasteurized. Under operation the monitoring
method according to the invention based on the finite element
mathematical model will also monitor the operation and give an
alarm if the chosen pre-determined sequence results in
under-pasteurization of the beer.
[0254] Referring now to FIGS. 16 and 17 which are isometric views
from two sides of a pasteurizing apparatus according to the
invention and generally corresponding to the flow-diagram or
diagrammatic view in FIGS. 4 and 5 with the difference that in this
embodiment shown in FIGS. 16 and 17 cooling and heating,
respectively, may only take place in all the pasteurizing heat
exchanger (past. 1-past .4) simultaneously. The flow of water and
beer, respectively, is shown by means of the arrows. The apparatus
is quite compact and is mounted on a base plate 50 having a cabinet
51 for all the regulating and computing equipment, the base plate
50 being of a size allowing the entire apparatus to be transported
in a commercially available 40 ft marine container. This is of
great importance for the economical aspects of the apparatus
according to the invention as the compactness allows shop-floor
construction, trial operation and even part commissioning which
entails large savings both as regards installation time and
costs.
[0255] Referring now to FIG. 18, an apparatus for the pasteurizing
of liquid products in a continuous flow, as for example fluid
foodstuffs and beverages, consists of a regenerative part 102 into
which the product is fed by a supply pump 101.
[0256] After the regenerative part 102, the product is led further
to the pasteurizing part 106 which cannot only heat the product to
the pasteurization temperature, but also cool the product down in
the event of a stop in production. Both the regenerative part 102
and the pasteurizing part 106 consist of heat exchangers. Heating
or cooling takes place by supplying hot or cold water via a mixing
valve 116 to the pasteurizing part 106. Temperature sensors 105,
111 are placed before and after the pasteurizing part 106, so that
the pasteurization process can be controlled. Between the
regenerative part 102 and the pasteurizing part 106 there are also
placed booster pumps 104, 112 which ensure that the product has
constant over-pressure in the apparatus.
[0257] The product is now led back to the regenerative part 102
where it transfers its heat to the product in the inlet. Hereafter,
the product is led to an outlet 18 where, for example, a filling
plant (not shown) can be placed.
[0258] The apparatus can be produced in several configurations,
depending on demands regarding temperatures and pasteurizing. The
temperatures used in the following are thus only examples, since
each product has its own specific temperature requirements.
[0259] The apparatus taken here as starting point (see FIG. 19) is
intended for the pasteurizing of beer. The apparatus consists of
two main heat exchangers, i.e. a regenerative heat exchanger which
is divided into two zones 102,103, and a pasteurizing heat
exchanger which is divided into three zones 106, 108, 110.
[0260] The product is led into the regenerative zone 102 by means
of a supply pump 1, where the product at 2.degree. C. is heated to
33.degree. C. The product is now led further to the second
regenerative zone 103 where it is heated to 65.degree. C. A booster
pump 104 and 112 ensures that there is an over-pressure, partly in
the pasteurizing heat exchanger 106, 108, 110 and partly in the
cooling part of the regenerative heat exchanger 102,103. This
over-pressure ensures that in the event of a possible leakage, air
or fluid does not come into the pipe system, but only out. In this
way it is avoided that bacteria capable of survival are transferred
to the pasteurized product.
[0261] A temperature sensor 105 is provided before the inlet to the
pasteurizing heat exchanger.
[0262] A valve 121 (see FIG. 20) is placed as close as possible to
the pasteurizing heat exchanger. During normal operation, this
valve 121 ensures that the inlet and the outlet from the
regenerative heat exchanger 103 on the nonpasteurized side are held
separate. During a stop in production, the valve 121 is opened,
whereby re-circulation is made possible in this side of the
regenerative heat exchanger 103. This valve is optional and is not
used in the cases/configurations where the outlet temperature from
the heat exchanger 103 is below the temperature limit for the
recording of PU.
[0263] At the inlet to the first zone 6 of the pasteurizing heat
exchanger, the product at 65.degree. C. is heated on the primary
side to 72.degree. C., this temperature being held through the
zones 108 and 110.
[0264] A valve 122 is placed as close as possible after the
pasteurizing heat exchanger. Under normal operation, this valve
must ensure that the inlet and outlet from the regenerative heat
exchanger 103 are held separate on the pasteurized side. During a
stop in production, the valve is opened, whereby re-circulation
becomes possible in this second side of the regenerative heat
exchanger 103. When the product leaves the last pasteurizing zone
110, it is pumped via the booster pump 112 into the cooling part of
the regenerative part 103 and is cooled down to approx. 40.degree.
C., and further to the last regenerative zone 102 where the product
is cooled down to 9.degree. C. A flow-control valve 113 can be
placed after the regenerative part. Hereafter, the product flows
through a cooler 114 and further to an outlet 118 where a possible
buffer tank and/or a bottling or containerising plant is placed.
With an embodiment having a minimal buffer tank, the flow-control
valve 113 ensures that the buffer tank does not get over-filled,
i.e. that the flow is controlled by the level in the buffer
tank.
[0265] In an apparatus without buffer tank, it is the filling plant
(not shown) which determines the flow through the apparatus.
[0266] The cooler 114 is used only if the outlet temperature of the
product becomes too high, e.g. as a result of a stop in operations
and subsequent restarting.
[0267] A temperature sensor 107, 109, 111 is placed after each
pasteurizing part 106, 108, 110. A temperature sensor 115 is also
placed after the cooler 114. These sensors register whether or not
the necessary temperatures have been achieved, so that heating and
cooling respectively can be controlled on the secondary side of the
pasteurizing heat exchanger 106, 108, 110.
[0268] The heating/cooling sources in the regenerative part 102,
103 consist of the product itself (hence regenerative), and in the
pasteurizing part 106, 108, 110 of hot and cold water 19, 20
respectively, where the amount of heat in the water is determined
by signals from the temperature sensors 107, 109, 111 in the
individual pasteurizing zones 106, 108, 110. The regulation of the
water supply itself is effected in a mixing valve 116 of commonly
known type. The return water from the secondary side of the
pasteurizing heat exchanger is led away via a return pipe 117,
possibly for heating with a view to re-use in the heat
exchanger.
[0269] The following is a description of the apparatus during a
stop in production.
[0270] The regenerative heat exchanger can be divided into two
zones 102 and 103 as shown, or constitute a single zone. In the
event of a stop in production, the temperature profile in the first
zone will be constant for the first minutes, after which the
temperature will slowly approach the average temperature for the
heat exchanger. In the second zone, or if there is only one zone,
the temperature in the last part of the exchanger and in the pipe
connections hereto will be so high that PU is recorded. To avoid
this, re-circulation takes place in both the regenerative zones and
pipe connections until a constant average temperature is achieved
below the temperature limit for the recording of PU (e.g.
53.degree. C.). The re-circulation is effected by opening the
valves 121 and 122.
[0271] The pasteurizing zones 106, 108, 110 will be cooled down to
e.g. 56.degree. C. during a production stop, so that the recording
of PU is stopped.
[0272] The following is a description of the apparatus when
re-started after a stop in production.
[0273] After a stop in production, ail of the pasteurizing zones
are re-heated to the normal temperatures to ensure that no
under-pasteurization occurs, and also that over-pasteurizing is
limited as much as possible.
[0274] When re-starting an apparatus without buffer tank, the
process is controlled by raising the temperature on the secondary
side of the pasteurizing heat exchanger 106, 108, 110 depending on
the speed of flow.
[0275] The above embodiments and the apparatus according to the
invention have been described by way of example, and various
modifications and amendments will be obvious to those skilled in
the art without departing from the scope of the appended
claims.
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