U.S. patent application number 15/564007 was filed with the patent office on 2018-05-24 for conveyor dishwasher and method for operating a conveyor dishwasher.
The applicant listed for this patent is ILLINOIS TOOL WORKS INC.. Invention is credited to Harald Disch, Martin Schrempp.
Application Number | 20180140160 15/564007 |
Document ID | / |
Family ID | 55702187 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180140160 |
Kind Code |
A1 |
Disch; Harald ; et
al. |
May 24, 2018 |
CONVEYOR DISHWASHER AND METHOD FOR OPERATING A CONVEYOR
DISHWASHER
Abstract
A conveyor dishwasher (2) includes a final rinse zone (18) and
at least one wash zone (12, 14, 16, 18) and also a conveyor
apparatus for conveying washware through the treatment zones of the
conveyor dishwasher (2), wherein the at least one wash zone (12,
14, 16, 18) has an associated wash tank (32, 34, 36) in which at
least a portion of the wash liquid which is sprayed in the at least
one wash zone (12, 14, 16, 18) is collected. The conveyor
dishwasher (2) also has a wastewater pump (61) for supplying wash
liquid, which is produced as wastewater during operation of the
conveyor dishwasher (2), to a heat exchanger device (60) in which
at least a portion of the thermal energy of the supplied wash
liquid is transferred to the final rinse liquid which is to be
sprayed in the final rinse zone (18).
Inventors: |
Disch; Harald; (Elzach,
DE) ; Schrempp; Martin; (Gengenbach, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ILLINOIS TOOL WORKS INC. |
Glenview |
IL |
US |
|
|
Family ID: |
55702187 |
Appl. No.: |
15/564007 |
Filed: |
April 1, 2016 |
PCT Filed: |
April 1, 2016 |
PCT NO: |
PCT/US2016/025505 |
371 Date: |
October 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A47L 15/241 20130101;
A47L 2401/12 20130101; Y02B 40/00 20130101; A47L 2501/01 20130101;
Y02B 30/52 20130101; A47L 15/4217 20130101; A47L 2501/05 20130101;
A47L 2501/06 20130101; A47L 2401/09 20130101; Y02B 40/42 20130101;
A47L 15/4291 20130101 |
International
Class: |
A47L 15/24 20060101
A47L015/24; A47L 15/42 20060101 A47L015/42 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2015 |
DE |
102015206337.2 |
Claims
1. Conveyor dishwasher (2) having a final rinse zone (18) and at
least one wash zone (12, 14, 16, 18) and also a conveyor apparatus
for conveying washware through the treatment zones of the conveyor
dishwasher (2), wherein the at least one wash zone (12, 14, 16, 18)
has an associated wash tank (32, 34, 36) in which at least a
portion of the wash liquid which is sprayed in the at least one
wash zone (12, 14, 16, 18) is collected, wherein the conveyor
dishwasher (2) has a wash system which is associated with the at
least one wash zone (12, 14, 16, 18) and has at least one wash pump
(33, 35, 45) and wash nozzles (26, 28, 30), wherein wash liquid
from the wash tank (32, 34, 36) can be supplied to the wash nozzles
(26, 28, 30) with the aid of the at least one wash pump (33, 35,
45), and wherein the wash liquid which is sprayed in the at least
one wash zone (12, 14, 16, 18) by the wash nozzles (26, 28, 30) at
least partially flows back into the wash tank (32, 34, 36) again
due to gravity, characterized in that the conveyor dishwasher (2)
has a wastewater pump (61) for supplying wash liquid, which is
produced as wastewater during operation of the conveyor dishwasher
(2), as required to a heat exchanger device (60) in which at least
a portion of the thermal energy of the supplied wash liquid is
transferred to the final rinse liquid which is to be sprayed in the
final rinse zone (18), and in that the conveyor dishwasher (2) has
an auxiliary tank (67) which forms a flow connection with the wash
tank (32, 34, 36) in particular by means of an overflow (68) or by
means of a bypass line, wherein the intake end of the wastewater
pump (61) forms a direct flow connection with the auxiliary tank
(67).
2. Conveyor dishwasher (2) according to claim 1, wherein the
conveyor dishwasher (2) has a control device (50) which is designed
to drive the wastewater pump (61) depending on a quantity of final
rinse liquid which is currently required per unit time and/or a
quantity of wastewater which is produced during operation of the
conveyor dishwasher (2) and/or depending on a liquid level of the
auxiliary tank, or on a liquid level in at least one wash tank (32,
34, 36) of the conveyor dishwasher and/or depending on a predefined
event and/or depending on an operating cycle and/or operating state
of the conveyor dishwasher (2).
3. Conveyor dishwasher (2) according to claim 1, wherein the
conveyor dishwasher (2) has a control device (50) which is designed
to switch off the wastewater pump (61) automatically when the
liquid level in the wash tank (32, 34, 36) falls below a predefined
or predefinable first level, and to switch on the wastewater pump
(61) again automatically as soon as the liquid level in the wash
tank (32, 34, 36) exceeds a predefined or predefinable second
level, wherein the first level corresponds to the second level.
4. Conveyor dishwasher (2) according to claim 2, wherein the
control device (50) is designed to initiate, as required, hot water
treatment, which is independent of the heat exchanger device (60),
of the final rinse liquid which is to be sprayed in the final rinse
zone (18), specifically in particular when: i) the thermal energy
which is transferred to the final rinse liquid, which is to be
sprayed in the final rinse zone (18), in the heat exchanger device
(60) is not sufficient to heat the final rinse liquid to a
predefined or predefinable minimum temperature; and/or ii) no wash
liquid is supplied to the heat exchanger device (60); and/or iii)
the quantity of wash liquid which is supplied to the heat exchanger
device (60) per unit time is not sufficient to heat the final rinse
liquid to a predefined or predefinable minimum temperature.
5. Conveyor dishwasher (2) according to claim 2, wherein the
conveyor dishwasher (2) has a boiler (9, 65) for heating, as
required, the final rinse liquid which is to be sprayed in the
final rinse zone (18), wherein the control device (50) is designed
to activate the boiler (9, 65) when: i) the thermal energy which is
transferred to the final rinse liquid, which is to be sprayed in
the final rinse zone (18), in the heat exchanger device (60) is not
sufficient to heat the final rinse liquid to a predefined or
predefinable minimum temperature; and/or ii) no wash liquid is
supplied to the heat exchanger device (60); and/or iii) the
quantity of wash liquid which is supplied to the heat exchanger
device (60) per unit time is not sufficient to heat the final rinse
liquid to a predefined or predefinable minimum temperature.
6. Conveyor dishwasher (2) according to claim 5, wherein the boiler
(9, 65) is designed to heat up the final rinse liquid which is to
be sprayed in the final rinse zone (18) to a predefined or
predefinable minimum temperature using electrical energy, steam, a
heat pump, gas or hot water.
7. Conveyor dishwasher (2) according to claim 2, wherein an
external boiler is provided, the conveyor dishwasher (2) forming or
being able to form a flow connection with the said external boiler
by means of a hot water connection (66), for supplying, as
required, hot water as the final rinse liquid which is to be
sprayed in the final rinse zone (18), wherein the control device
(50) is designed to activate the hot water connection (66) when: i)
the thermal energy which is transferred to the final rinse liquid,
which is to be sprayed in the final rinse zone (18), in the heat
exchanger device (60) is not sufficient to heat the final rinse
liquid to a predefined or predefinable minimum temperature; and/or
ii) no wash liquid is supplied to the heat exchanger device (60);
and/or iii) the quantity of wash liquid which is supplied to the
heat exchanger device (60) per unit time is not sufficient to heat
the final rinse liquid to a predefined or predefinable minimum
temperature.
8. Conveyor dishwasher (2) according to claim 1, wherein the wash
tank (32, 34, 36) has a capacity of 20 to 200 litres, and the
auxiliary tank (67) has a capacity of 10 to 50 litres.
9. Conveyor dishwasher (2) according to claim 1, wherein the
conveyor dishwasher (2) further has a wastewater line (62) which
forms or is able to form a flow connection with a wastewater system
(63) and by means of which the wash liquid is discharged after the
wash liquid has first passed the heat exchanger device (60).
10. Conveyor dishwasher (2) according to claim 1, wherein the heat
exchanger device (60) has at least one counterflow heat
exchanger.
11. Method for operating a conveyor dishwasher (2), in particular a
conveyor dishwasher (2) according to claim 1, wherein at least a
portion of the wash liquid which is produced as wastewater is at
least temporarily supplied to a heat exchanger device (60) in which
at least a portion of the thermal energy of the supplied wash
liquid is transferred to the final rinse liquid which is to be
sprayed in a final rinse zone (18) of the conveyor dishwasher
(2).
12. Method according to claim 11, wherein the wash liquid is
supplied as wastewater to a wastewater system (63) after passing
the heat exchanger device (60).
13. Method according to claim 11, wherein the wash liquid is
supplied to the heat exchanger device (60) cyclically and/or
depending on a liquid level in the wash tank (32, 34, 36).
14. Method according to claim 11, wherein, when no wash liquid is
supplied to the heat exchanger device (60) and/or when the thermal
energy which is transferred to the quantity of final rinse liquid,
which is to be sprayed in the final rinse zone (18), in the heat
exchanger device (60) is not sufficient to heat the final rinse
liquid to a predefined or predefinable minimum temperature, a
boiler (9, 65) which operates independently of the heat exchanger
device (60) is activated.
15. A conveyor dishwasher having multiple treatments zones
including a final rinse zone and at least one wash zone, a conveyor
apparatus for conveying washware through the treatment zones,
wherein the at least one wash zone has an associated wash tank in
which at least a portion of the wash liquid which is sprayed in the
at least one wash zone is collected, wherein a wash system is
associated with the at least one wash zone and has at least one
wash pump and wash nozzles, wherein wash liquid from the wash tank
can be supplied to the wash nozzles via operation of the at least
one wash pump, and wherein the wash liquid which is sprayed in the
at least one wash zone by the wash nozzles at least partially flows
back into the wash tank again due to gravity, wherein the conveyor
dishwasher has a wastewater pump for supplying wash liquid, which
is produced as wastewater during operation of the conveyor
dishwasher, to a heat exchanger device in which at least a portion
of the thermal energy of the supplied wash liquid is transferred to
the final rinse liquid which is to be sprayed in the final rinse
zone, wherein the conveyor dishwasher has an auxiliary tank with an
overflow connection or bypass line connection with the wash tank,
wherein the intake side of the wastewater pump is connected to
receive flow from the auxiliary tank.
16. The conveyor dishwasher according to claim 15, wherein the
conveyor dishwasher has a control device which is configured to
selective drive the wastewater pump depending on a quantity of
final rinse liquid which is currently required per unit time and/or
a quantity of wastewater which is produced during operation of the
conveyor dishwasher and/or depending on a liquid level of the
auxiliary tank, or on a liquid level in at least one wash tank of
the conveyor dishwasher and/or depending on a predefined event
and/or depending on an operating cycle and/or operating state of
the conveyor dishwasher.
17. The conveyor dishwasher according to claim 15, wherein the
conveyor dishwasher has a control device which is configured to
automatically switch off the wastewater pump when the liquid level
in the wash tank falls below a predefined or predefinable first
level, and to automatically switch on the wastewater pump again as
soon as the liquid level in the wash tank exceeds a predefined or
predefinable second level.
18. The conveyor dishwasher according to claim 17, wherein the
control device is configured to selectively initiate hot water
treatment, which is independent of the heat exchanger device, of
the final rinse liquid which is to be sprayed in the final rinse
zone, specifically in particular when: i) the thermal energy which
is transferred to the final rinse liquid in the heat exchanger
device is not sufficient to heat the final rinse liquid to a
predefined or predefinable minimum temperature; and/or ii) no wash
liquid is supplied to the heat exchanger device; and/or iii) the
quantity of wash liquid which is supplied to the heat exchanger
device per unit time is not sufficient to heat the final rinse
liquid to a predefined or predefinable minimum temperature.
19. The conveyor dishwasher according to claim 18, wherein the
conveyor dishwasher has a boiler for selectively heating the final
rinse liquid after the final rinse liquid passes through the heat
exchanger, and the control device operates the boiler for purpose
of the selective hot water treatment.
20. The conveyor dishwasher according to claim 19, wherein the
boiler is designed to heat up the final rinse liquid to a
predefined or predefinable minimum temperature using electrical
energy, steam, a heat pump, gas or hot water.
Description
TECHNICAL FIELD
[0001] The present invention relates to a conveyor dishwasher
having a conveyor apparatus for conveying washware through the
individual treatment zones of the conveyor dishwasher, wherein the
conveyor dishwasher has at least one wash zone in which wash liquid
from a wash tank associated with the wash zone is sprayed onto the
washware. The generic conveyor dishwasher further has, arranged
behind the at least one wash zone as seen in the direction of
conveying the washware, at least one final rinse zone in which
final rinse liquid is sprayed onto the washware.
BACKGROUND
[0002] A conveyor dishwasher according to the present invention is
in particular a conveyor belt dishwasher or a rack conveyor
dishwasher.
[0003] A conveyor dishwasher of the type mentioned at the outset is
known in principle from the prior art and is conventionally used in
the commercial sector. Unlike so-called programmable units, in
which the washware to be cleaned remains stationary in the
dishwasher during cleaning, in the case of conveyor dishwashers the
washware is conveyed through different treatment zones of the
conveyor dishwasher.
[0004] Conventionally, a conveyor dishwasher has as the treatment
zones at least one pre-wash zone and at least one main wash zone,
which is arranged after the pre-wash zone(s), as seen in the
direction of conveying the washware. At least one final rinse zone
is typically arranged after the main wash zones(s), as seen in the
conveying direction.
[0005] It is also known to provide, between the main wash zone and
the final rinse zone, in addition at least one post-wash zone or
pre-rinse zone. As seen in the direction of conveying the washware,
the washware, which is either received directly on a conveyor belt
or is held in wash racks, conventionally passes through an entry
tunnel, the subsequent pre-wash zones(s), main wash zone(s), any
provided post-wash zone(s), final rinse zone(s) and a drying zone
and into an exit section.
[0006] In each case, a wash system is associated with the said wash
zones (pre-wash zone, main wash zone and any provided post-wash
zone) of the conveyor dishwasher, and said wash system has a wash
pump and a line system that is connected to the wash pump and by
means of which wash liquid is supplied to corresponding spray
nozzles of the wash zones. In the respective wash zone, the wash
liquid supplied to the spray nozzles is sprayed onto the washware,
which is conveyed through the respective wash zones by a conveyor
apparatus of the conveyor dishwasher.
[0007] A wash tank is associated with each wash zone, and in said
wash tank sprayed liquid is received and/or in this wash tank
liquid for the spray nozzles of the relevant zones is provided.
[0008] In the conveyor dishwashers that are known from the prior
art, final rinse liquid is sprayed onto the washware by means of
the spray nozzles of the final rinse zone in the form of fresh
water, which may be pure or may have further additives, such as
rinse aid, added to it. At least a portion of the sprayed final
rinse liquid is conveyed, by means of a cascade system, from one
treatment zone to another in the opposite direction to the
direction of conveying the washware.
[0009] The sprayed final rinse liquid is collected in a tank
(post-wash tank) of the post-wash zone, from which it is conveyed,
by means of the wash pump of the wash system that is part of the
post-wash zone, to the spray nozzles (post-wash nozzles) of the
post-wash zone. In the post-wash zone, wash liquid is rinsed off
the washware. The liquid which is produced during this flows into
the wash tank of the at least one main wash zone, which is upstream
of the post-wash zone, as seen in the direction of conveying the
washware. Here, the liquid is conventionally provided with a
detergent and is sprayed onto the washware by a pump system (wash
pump system) that is part of the wash system of the main wash zone,
by means of the nozzles (wash nozzles) of the main wash zone.
[0010] From the wash tank of the main wash zone--where no further
main wash zone is provided--the liquid then flows into the pre-wash
tank of the pre-wash zone. The liquid in the pre-wash tank is
sprayed onto the washware by means of a pump system that is part of
the wash system of the pre-wash zone, by means of the pre-wash
nozzles of the pre-wash zone, in order to remove large pieces of
dirt from the washware.
[0011] In the commercial dishwashing sector, there are various
standards and regulations in which the requirements of performance
regarding hygiene in cleaning processes and method checks thereof
are defined. Common to all standards and regulations is the
stipulation of minimum temperatures in the wash and/or rinse zones
of the commercial dishwasher during the cleaning process. In this
way, among other things an at least partial thermal disinfection of
the washware is to be performed.
[0012] The requirements of the predetermined minimum temperatures
in the relevant treatment zones of the conveyor dishwasher have the
result that during operation of the commercial dishwasher
relatively high quantities of energy have to be applied in order to
heat the wash and rinse liquids to the required minimum
temperatures. On the other hand, in the case of currently known
conveyor dishwashers, up to 55% of the energy which is introduced
during operation of the conveyor dishwasher is discharged as waste
heat. This occurs among other things because, during operation of
the conveyor dishwasher, clouds of steam (vapor) and moist warm air
are necessarily produced, wherein in particular the clouds of steam
have to be removed from the conveyor dishwasher, at least partly in
the form of outgoing air, by means of an outgoing air system. In
this context, the outgoing air system must be designed such that at
least a large proportion of the outgoing air that is produced
during operation of the conveyor dishwasher is removed to the
outside from the room in which the conveyor dishwasher is set up in
order to be able effectively to prevent the humidity of the air in
the room in which it is set up (ambient air) from increasing to
such an extent that undesired condensation of water vapor is
produced, in particular on cool surfaces in the room in which it is
set up. In this context, it must be ensured that, depending on the
conveyor dishwasher, a quantity of outgoing air of 150 to 800
m.sup.3/h that has to be removed is produced for each
dishwasher.
[0013] It is already known, from the printed specification DE 10
2011 086 593 A1, that a heat exchanger unit having a heat exchanger
that is cooled with water, in particular fresh water, can be
associated with the outgoing air system of a conveyor dishwasher in
order to transfer thermal energy, from at least a portion of the
outgoing air that is to be removed from the conveyor dishwasher by
means of the outgoing air system, to the cooling water of the heat
exchanger associated with the outgoing air system and hence to
reduce the heat losses occurring during operation of the conveyor
dishwasher.
[0014] Even though at least a portion of the thermal energy of the
outgoing air to be removed from the dishwasher can be recovered by
this measure, one must consider the fact that up to approximately
30% of the energy that is introduced for operation of a commercial
conveyor dishwasher is discharged to the wastewater as heat losses.
In a typical conveyor dishwasher, the energy lost through the
wastewater--depending on the configuration of the dishwasher, and
the size--is approximately 5 to 15 kWh per hour of running time. In
this context, the wastewater is typically at a temperature of 40 to
75.degree. C., depending on the configuration of the dishwasher,
and the type.
[0015] Unlike the situation with programmable units, such as hood
or under-counter dishwashers, hitherto no technology has been
available by means of which the energy of the wastewater in a
conveyor dishwasher can be efficiently recovered by suitable heat
exchanger systems and can be returned to the dishwasher again by,
for example, heating up the required final rinse liquid.
[0016] This is primarily because of the continuous operation of
conveyor dishwashers, by comparison with the batch processing of
stationary programmable units: unlike the situation with
programmable units, in which with each program cycle the same
quantity of wastewater occurs as final rinsing fresh water, in the
case of conveyor dishwashers with certain operating cycles there is
no wastewater at all or a smaller quantity of wastewater than the
fresh water that is simultaneously required as final rinse liquid
for the final rinse.
[0017] If for example the conveyor dishwasher is shifted from a
standstill to an operating mode, then although the conveyor
dishwasher requires fresh water straight away for the final rinse
there is at this time no wastewater available yet from which at
least a portion of the thermal energy can be recovered in order to
heat up the fresh water required for the final rinse. This is
because, when the conveyor dishwasher starts up, first the wash
systems and wash lines are filled with wash liquid. This wash
liquid, which is required for filling the wash systems and wash
lines, is taken from the corresponding wash tank of the
corresponding wash zone, such that the level of wash liquid in the
corresponding wash tank necessarily falls. Consequently, at least
for the initial period after the conveyor dishwasher is started up,
no wastewater that can be used for heating the final rinse liquid
by means of a heat exchanger device is produced. To be more
precise, no wastewater flows away by means of a corresponding
wastewater overflow until the wash tanks or the first wash tank, as
seen in the direction of conveying the washware, has been
completely filled up or topped up.
[0018] Taking this problem as a starting point, an object of the
invention is to further develop a conveyor dishwasher of the type
mentioned at the outset such that during operation of the conveyor
dishwasher resources, in particular energy, can be saved without
having a negative effect on the cleaning result and the efficiency
of the conveyor dishwasher.
[0019] A further object of the present invention is to specify a
corresponding method for operating a conveyor dishwasher.
SUMMARY
[0020] Accordingly, in the case of a conveyor dishwasher of the
type mentioned at the outset, according to the invention it is in
particular required that it has a wastewater pump for supplying
wash liquid as required to a heat exchanger device in which at
least a portion of the thermal energy of the supplied wash liquid
is transferred to the final rinse liquid, which is to be sprayed in
the final rinse zone.
[0021] Here, the invention is based on the realization that up to
approximately 30% of the energy that is introduced during operation
of the conveyor dishwasher is transferred to the wastewater as heat
losses. By providing a corresponding heat exchanger device to which
wash liquid, and in particular the wash liquid that is produced as
wastewater during operation of the conveyor dishwasher, is supplied
as required, it is possible to recover at least a portion of the
thermal energy in the wastewater and to use it for heating the
final rinse liquid, which is to be sprayed in the final rinse zone.
In this way, during operation of the conveyor dishwasher resources
can be saved without this having an effect on the cleaning
performance or the cleaning quality of the conveyor dishwasher.
[0022] Unlike the situation with programmable units, in which with
each program cycle the same quantity of wastewater is produced
consistent with final rinsing liquid required, in the case of
conveyor dishwashers, by contrast, with certain operating cycles no
wastewater is produced, even though, depending on the loading
condition, fresh water may be required at any time as final rinse
liquid for the purpose of the final rinse.
[0023] For this reason, in a preferred further development of the
conveyor dishwasher according to the invention, it is provided for
it to be provided with a control device which is designed to drive
the wastewater pump depending on a quantity of final rinse liquid
which is currently in fact required and/or a quantity of wastewater
which is produced during operation of the conveyor dishwasher. For
example, the control device is designed to drive the wastewater
pump appropriately, depending on a liquid level in the wash tank
and/or depending on a predefined event and/or depending on an
operating cycle and/or operating state of the conveyor
dishwasher.
[0024] If for example the conveyor dishwasher is shifted from a
standstill to an operating mode, then although the conveyor
dishwasher requires fresh water straight away as final rinse water
for the final rinse, at this time no wastewater is produced yet
which is available for the purpose of heat recovery. As already
stated at the outset, this is because, when the conveyor dishwasher
starts up, first the wash systems and wash lines are filled with
wash liquid, with the result that depending on the quantity of
final rinse liquid that is supplied per unit time a certain period
is needed to re-fill the wash tanks. For this reason, in the
advantageous further development of the solution according to the
invention, it is provided for the control device actually to switch
on the wastewater pump only when, during operation of the conveyor
dishwasher, wastewater that can be used for recovery thereof is
produced.
[0025] In a further development of the last-mentioned embodiment,
it is provided in particular for the control device of the conveyor
dishwasher to be designed to switch off the wastewater pump by
means of which the wash liquid that is produced as wastewater
during operation of the conveyor dishwasher is supplied to the heat
exchanger device, preferably automatically, when the liquid level
in the wash tank falls below a predefined or predefinable level,
and to switch on the wastewater pump again, preferably
automatically, as soon as the liquid level in the wash tank again
exceeds a predefined or predefinable second level, wherein the
first level preferably corresponds to the second level. This is a
particularly easily realizable and yet effective way of switching
the wastewater pump on and off in dependence on whether during
operation of the conveyor dishwasher any wash liquid at all is
produced as wastewater.
[0026] In this context, it is in particular conceivable to provide
the wash tank with a corresponding level sensor by means of which
the current liquid level in the wash tank can be detected,
preferably continuously. Depending on the current liquid level, a
decision is then taken in the control device on whether wash liquid
is being produced as wastewater and whether this wash liquid can be
supplied to the heat recovery device.
[0027] In a further development of the last-mentioned embodiment,
the control device is in particular designed to determine the
quantity of wash liquid required as wash liquid per unit time and
to estimate the anticipated quantity of wastewater produced per
unit time and, in dependence thereon, to regulate accordingly the
quantity of wastewater that is supplied per unit time to the heat
recovery device with the aid of the wastewater pump, such that a
sufficient quantity of wash liquid for the wash process to be
performed in the wash zone is always available in the wash
tank.
[0028] In a particularly preferred further development of the
conveyor dishwasher according to the invention, it is provided for
the control device to be designed to initiate, as required, hot
water preparation, which is independent of the heat exchanger
device, of the final rinse liquid which is to be sprayed in the
final rinse zone. In this context, the term "as required" means in
particular when it is detected that the thermal energy which is
transferred to the final rinse liquid, which is to be sprayed in
the final rinse zone, in the heat exchanger device is not
sufficient to heat the final rinse liquid to a predefined or
predefinable minimum temperature, and/or when it is detected that
no wash liquid is supplied to the heat exchanger device, and/or
when it is detected that the quantity of wash liquid which is
supplied to the heat exchanger device per unit time is not
sufficient to heat the final rinse liquid to the predefined or
predefinable minimum temperature. In these cases, the control
device preferably automatically initiates hot water preparation,
which is independent of the heat exchanger device, of the final
rinse liquid which is to be sprayed in the final rinse zone, in
order to achieve a situation in which the final rinse liquid which
is actually sprayed in the final rinse zone is at the predefined or
predefinable minimum temperature, with the result that the hygiene
requirements are accordingly met.
[0029] In this context, it is in particular conceivable for the hot
water preparation, which is independent of the heat exchanger
device, to be performed with the aid of a hot water preparation
apparatus such as a boiler, wherein this hot water preparation
apparatus is preferably a constituent forming part of the conveyor
dishwasher. For example, it is conceivable for the hot water
preparation apparatus to be designed to heat up the final rinse
liquid which is to be sprayed in the final rinse zone to the
predefined or predefinable minimum temperature using electrical
energy, steam, a heat pump, gas or hot water.
[0030] As an alternative or in addition thereto, it is, however,
also conceivable for the hot water preparation, which is to be
carried out as required, of the final rinse liquid which is to be
sprayed in the final rinse zone to be performed outside the
conveyor dishwasher. It is conceivable in this case for example to
provide an external hot water preparation apparatus, for example in
the form of a hot water supply that is centralized (within the
building). Thus, in this case the conveyor dishwasher may form or
be able to form a flow connection with said external hot water
preparation apparatus by means of a corresponding hot water
connection, in order to supply, as required, hot water as the final
rinse liquid which is to be sprayed in the final rinse zone. The
control device, which is part of the conveyor dishwasher, should in
this context be designed to activate the hot water connection as
required, when the thermal energy which is transferred to the final
rinse liquid, which is to be sprayed in the final rinse zone, in
the heat exchanger device is not sufficient to heat the final rinse
liquid to a predefined or predefinable minimum temperature, and/or
when no wash liquid is supplied to the heat exchanger device,
and/or when the quantity of wash liquid which is supplied to the
heat exchanger device per unit time is not sufficient to heat the
final rinse liquid, which is to be sprayed in the final rinse zone,
to the predefined or predefinable minimum temperature.
[0031] In a preferred realization of the conveyor dishwasher
according to the invention, it is provided for the conveyor
dishwasher to have a wash system which is associated with the at
least one wash zone and has at least one wash pump and wash
nozzles, wherein wash liquid from the wash tank can be supplied to
the wash nozzles with the aid of the at least one wash pump, and
wherein the wash liquid which is sprayed in the at least one wash
zone by the wash nozzles at least partially flows back into the
wash tank again due to gravity. In other words, in this preferred
realization of the conveyor dishwasher according to the invention,
it is provided for the wash liquid to recirculate in the at least
one wash zone.
[0032] According to one aspect of the present invention, the intake
end of the wastewater pump forms a direct flow connection with the
wash tank in order to supply the wash liquid, which is produced as
wastewater, as required to the heat exchanger device. As stated
above in this context, here the conveyor dishwasher should also be
provided, in addition to the heat exchanger device, with hot water
preparation which operates independently thereof, for example in
the form of a hot water preparation apparatus (boiler) that is part
of the conveyor dishwasher, in order to be able to ensure that
there is sufficient heating of the final rinse liquid which is to
be sprayed in the final rinse zone, at least when no wash liquid is
supplied to the heat exchanger device.
[0033] As an alternative to the above-mentioned embodiment in which
the intake end of the wastewater pump forms a direct flow
connection with the wash tank, it is conceivable for the conveyor
dishwasher to have an auxiliary tank which forms a flow connection
with the wash tank in particular by means of an overflow or by
means of a bypass line, wherein the intake end of the wastewater
pump forms a direct flow connection with the auxiliary tank. The
auxiliary tank should in particular serve as a buffer reservoir in
order as required to provide interim storage of the wastewater
which is produced in the wash zone and is to be removed from the
wash zone or the wash tank of the wash zone.
[0034] In particular, the wash liquid which is subject to (interim)
storage in the auxiliary tank and has been produced in the wash
zone as wastewater no longer serves as recirculated wash liquid. In
other words, the wash system of the at least one wash zone, and in
particular the at least one wash pump of the wash system, does not
form a flow connection with the auxiliary tank.
[0035] In this embodiment, in which an auxiliary tank that is
arranged before the wash tank of the (first) wash zone of the
conveyor dishwasher, as seen in the direction of conveying the
washware, is provided, in some circumstances there is no need to
provide hot water preparation that is independent of the heat
exchanger device, since appropriate dimensioning of the auxiliary
tank enables it always to be ensured that a sufficient quantity of
wastewater can be supplied to the heat exchanger device at any time
and in any operating situation, in particular also directly during
or after the conveyor dishwasher has started up, for the final
rinse liquid which is to be sprayed in the final rinse zone to be
raised to the predefined or predefinable minimum temperature.
[0036] In practice in this context, it has been found that a
capacity of 10 to 50 liters is sufficient for the auxiliary tank in
order that the conveyor dishwasher can be operated fully
effectively without hot water preparation which is independent of
the heat exchanger device, if the capacity of the wash tank is 20
to 200 liters.
[0037] The invention relates not only to a conveyor dishwasher of
the above-mentioned type but also to a method for operating a
conveyor dishwasher of this kind, wherein at least a portion of the
wash liquid which is produced as wastewater is at least temporarily
supplied to a heat exchanger device in which at least a portion of
the thermal energy of the supplied wash liquid is transferred to
the final rinse liquid which is to be sprayed in a final rinse zone
of the conveyor dishwasher.
[0038] Exemplary embodiments of the conveyor dishwasher according
to the invention will be described in more detail below with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 shows schematically a dishwasher which is designed in
the form of a conveyor dishwasher, for the purpose of explaining
the general construction and functioning;
[0040] FIG. 2 shows schematically a wash zone of an exemplary
embodiment of the dishwasher according to the invention; and
[0041] FIG. 3 shows schematically a wash zone of a further
exemplary embodiment of the conveyor dishwasher according to the
invention.
DETAILED DESCRIPTION
[0042] FIG. 1 shows a conveyor dishwasher 2 having a conveyor
apparatus 4 for conveying washware (not illustrated) in a direction
8 of conveying through the conveyor dishwasher 2. The conveyor
dishwasher 2 has at least one wash zone, for example as illustrated
in FIG. 1, a pre-wash zone 12 and a main wash zone 14 which is
arranged after the pre-wash zone 12, as seen in the direction 8 of
conveying.
[0043] As seen in the direction 8 of conveying, after the at least
one wash zone 12, 14 there is arranged an post-wash zone 16, and
after the post-wash zone 16 there is arranged at least one final
rinse zone, for example as illustrated only a single final rinse
zone 18. In the conveyor dishwasher 2 that is illustrated
schematically in FIG. 1, adjoining the final rinse zone 18, as seen
in the direction 8 of conveying the washware, is a drying zone 40.
The respective zones 12, 14, 16, 18, 40 of the conveyor dishwasher
2 may be separated from one another by means of parting curtains
47.
[0044] In the embodiment which is illustrated schematically in FIG.
1, the entry tunnel 10 is also itself separated from the entry 11
by means of a parting curtain 47. By providing the parting curtains
47, overspray of wash liquid and final rinse liquid and the
emergence of vapor from the conveyor dishwasher 2 are
prevented.
[0045] Associated with the said treatment zones 12, 14, 16, 18 of
the conveyor dishwasher 2 are spray nozzles 20, 22, 24, 26, 28, 30.
These spray nozzles 20, 22, 24, 26, 28, 30 serve to spray liquid
onto the washware as the latter is conveyed through the respective
treatment zones 12, 14, 16, 18 by the conveyor apparatus 4. The
individual spray systems of the treatment zones 12, 14, 16, 18
ensure that the washware to be treated is sprayed from both the
upper side and the underside.
[0046] In the conveyor dishwasher 2 which is illustrated
schematically in FIG. 1, however, the final rinse zone 18 has not
only downwardly directed upper spray nozzles 20 and upwardly
directed lower spray nozzles 22 but also transversely directed
lateral spray nozzles 24 on each side of the conveyor apparatus 4.
The use of lateral spray nozzles 24 makes it possible to spray the
washware surfaces (dish surfaces) with final rinse liquid in
targeted manner even in zones that are hidden behind other objects.
Specifically when the conveyor system is fully loaded, that is to
say when the dish carrier is loaded with plates side by side, the
use of lateral spray nozzles 24 in the final rinse zone 18 is
clearly advantageous, in respect of the final rinse result
(effective rinsing of detergent residues off dish surfaces even in
hidden zones), over systems in which only upper and lower spray
nozzles 20, 22 and no transversely directed lateral spray nozzles
24 are provided in the final rinse zone 18.
[0047] Further associated with the post-wash zone 16, main wash
zone 14 and pre-wash zone 12 are tanks (post-wash tank 32, main
wash tank 34, pre-wash tank 36), for receiving sprayed liquid
and/or for providing liquid for the spray nozzles 26, 28, 30 of the
relevant treatment zones 14, 16, 18.
[0048] In the conveyor dishwasher 2 which is illustrated
schematically in FIG. 1, final rinse liquid, which is composed of
fresh water and metered-in rinse aid, is sprayed onto the washware
(not illustrated) by means of the spray nozzles 20, 22, 24 of the
final rinse zone 18, said spray nozzles 20, 22, 24 being arranged
above and below and to the side of the conveyor apparatus 4. A
portion of the sprayed final rinse liquid is conveyed, by means of
a cascade system, from one treatment zone to another in the
opposite direction to the direction 8 of conveying the washware.
The remaining portion of the final rinse liquid which is sprayed in
the final rinse zone 18 is fed directly into the pre-wash tank 36
which is associated with the pre-wash zone 12, by means of a valve
V1 and a bypass line 38.
[0049] In the cascade system, the final rinse liquid which is
sprayed by the final rinse nozzles 20, 22, 24 flows by gravity from
the final rinse zone 18 into the post-wash tank 32, which is
associated with the post-wash zone 16. The final rinse liquid which
is sprayed in the final rinse zone 18 and which is collected by the
post-wash tank 33 is then conveyed to the spray nozzles (post-wash
nozzles 26) of the post-wash zone 16 with the aid of a post-wash
pump 45. In the post-wash zone 16, wash liquid is rinsed off the
washware. The liquid which is produced during this (post-wash
liquid) flows by gravity into the main wash tank 34, which is
associated with the main wash zone 14. Preferably, a drain element
39, for example a draining board or a baffle plate, is provided for
this purpose and guides the post-wash liquid which is sprayed by
the post-wash nozzles 26 into the main wash tank 34.
[0050] According to another embodiment, which is not shown in the
drawings, the drain element 39 can be dispensed with if the main
wash tank 34 extends below the post-wash nozzles 26 of the
post-wash zone 16.
[0051] The liquid which is received by the main wash tank 34 of the
main wash zone 14 is conventionally provided with a detergent and
is sprayed onto the washware with the aid of a main wash pump 35 by
means of the spray nozzles (main wash nozzles 28) of the main wash
zone 14. The wash liquid which is sprayed by the main wash nozzles
28 flows by gravity back into the main wash tank 34.
[0052] The main wash tank 34 forms a fluid connection with the
pre-wash tank 36, which is associated with the pre-wash zone 12, by
means of an overflow line 37. The wash liquid which is sprayed in
the main wash zone 14 reaches the pre-wash tank 36 by means of said
overflow line 37 when a sufficient quantity of wash liquid is
received in the main wash tank 34.
[0053] The liquid which is received in the pre-wash tank 36 of the
pre-wash zone 12 is then sprayed onto the washware with the aid of
a pre-wash pump 33 by means of the spray nozzles (pre-wash nozzles
30) of the pre-wash zone 12, in order to remove large pieces of
dirt from the washware. The wash liquid which is sprayed by the
pre-wash nozzles 30 flows by gravity back into the pre-wash tank
36.
[0054] The pre-wash tank 36 is provided with an overflow line 31
which, when a liquid level in the pre-wash tank 36 is exceeded,
serves to supply the excess quantity of liquid to a heating device
as wastewater. This aspect is described in detail below with
reference to the illustrations in FIGS. 2 and 3.
[0055] As indicated above, the liquid which is sprayed in the main
wash zone 14 and the pre-wash zone 12 preferably contains
detergent, which is metered for example into the liquid which is
received in the main wash tank 34 of the main wash zone 14 with the
aid of a detergent metering device (not shown in the drawings).
[0056] As mentioned above, the drying zone 40 follows the final
rinse zone 18, as seen in the direction 8 of conveying the
washware. In the drying zone 40, the washware is dried by means of
dry warm air in order to blow away or dry off moisture which is on
the washware. In order to keep the humidity of the air in a range
that is favorable to drying, it is conceivable for example to
supply indoor air to the drying zone 40 from the outside, by means
of an opening, for example the exit opening for the washware.
[0057] The warm moist air in the drying zone 40 is then removed
from the drying zone 40, for example with the aid of a fan 41, by
means of a further opening. In this context, it is advantageous if
the outgoing air passes out of the drying zone 40 and through a
device 42 for heat recovery in which for example a condenser may be
provided. The device 42 for heat recovery serves to recover at
least a portion of the thermal energy in the outgoing flow.
[0058] If, before the conveyor dishwasher 2 is first started up,
the tanks which are associated with the wash zones 12, 14 and 16
(pre-wash tank 36, main wash tank 34, post-wash tank 32) are empty
or only insufficiently filled, they must first be filled by means
of a fresh water line 48 and/or by spraying final rinse liquid in
the final rinse zone 18. The fresh water line 48 is connectable to
a fresh water mains supply by means of a controllable valve V3. The
quantity of wash liquid which is available in the main wash zone 14
and the pre-wash zone 12 may be monitored, with the aid of a level
sensor that is provided in the main wash tank 34 and with the aid
of a level sensor that is provided in the pre-wash tank 36
respectively, and signaled to a control device 50.
[0059] As illustrated in FIG. 1, a fresh water container 44 may be
associated with the final rinse zone 18, for the interim storage of
at least a portion of the fresh water which is provided for the
final rinse. The fresh water container 44 is provided on one side
with a fresh water connection, which is connectable by means of a
controllable fresh water supply valve V2 to a fresh water mains
supply, and on the other is connected to the intake side of a final
rinse pump 43. It goes without saying, however, that it is also
conceivable to dispense with a fresh water container 44 for the
interim storage of at least a portion of the fresh water which is
provided for the final rinse, and to connect the fresh water supply
valve V2 directly to the intake side of the final rinse pump
43.
[0060] Nor is it absolutely necessary to provide a final rinse pump
43. Rather, it is possible for example also to use the pressure
from the fresh water mains network in order to supply the fresh
water which is to be sprayed in the final rinse zone 18, as final
rinse liquid, to the final rinse nozzles 20, 22, 24.
[0061] In the case of the conveyor dishwasher 2 which is
illustrated schematically in FIG. 1, by contrast, a final rinse
pump 43 is used, whereof the delivery side is connected by means of
a line system to a water heater 9 ("boiler"). In this context, the
line system is designed such that the liquid which is conveyed by
the final rinse pump 43 to the spray nozzles 20, 22, 24 of the
final rinse zone 18 first passes through the device 42 for heat
recovery, in which at least a portion of the thermal energy from
the outgoing air that is removed from the conveyor dishwasher is
used to heat the liquid which is supplied to the spray nozzles 20,
22, 24 of the final rinse zone 18.
[0062] As an alternative or in addition thereto, it is provided for
the liquid which is to be conveyed by the final rinse pump 43 to
the spray nozzles 20, 22, 24 of the final rinse zone 18 to pass
through a heat exchanger device 60 in which at least a portion of
the thermal energy of the wastewater which is produced during
operation of the conveyor dishwasher 2 and which is to be removed
is transferred to the final rinse liquid which is to be sprayed in
the final rinse zone 18. The construction and functioning of this
heat exchanger device 60 are described in more detail below with
reference to the embodiments according to FIGS. 2 and 3.
[0063] Rinse aid is metered into the fresh water which is supplied
to the final rinse pump 43, either directly from the fresh water
supply valve V2 or from the fresh water container 44, with the aid
of a rinse aid metering device which has a rinse aid pump 6.
Preferably, the rinse aid metering device is arranged such that the
metering of rinse aid into the fresh water is performed at a
location in which the fresh water has not yet been heated. Tests in
this context have shown that a markedly better and more even mixing
of the rinse aid with the fresh water is produced if the rinse aid
is metered into unheated fresh water.
[0064] To be more precise, rinse aid should preferably be metered
into fresh water which is at a temperature of less than 40.degree.
C., preferably less than 30.degree. C.
[0065] Consequently, in the embodiment of the conveyor dishwasher 2
which is illustrated schematically in FIG. 1, the metering of rinse
aid takes place between the final rinse pump 43 and the water
heater 9, or between the device 42 for heat recovery and the heat
exchanger device 60. In FIG. 1, the control device 50 of the
conveyor dishwasher 2 is indicated only schematically. In the
control device 50, preferably a plurality of predefined or
predefinable running programs are stored. To this end, the control
device 50 has a corresponding storage device, preferably a random
access memory (RAM). Each individual running program defines the
process parameters which have been laid down for the treatment of
the washware in the various treatment zones of the conveyor
dishwasher 2, which in particular includes the temperature, in
particular the minimum temperature, of the wash liquid which is to
be sprayed in the pre-wash zone 12, the wash liquid which is to be
sprayed in the main wash zone 14, the liquid which is to be sprayed
in the post-wash zone 16 and/or the final rinse liquid which is to
be sprayed in the final rinse zone 18.
[0066] To this end, it is preferred if a corresponding heating
device 55, 56, 58 is arranged in the pre-wash tank 36 which is
associated with the pre-wash zone 12, in the main wash tank 34
which is associated with the main wash zone 14 and/or in the
post-wash tank 32 which is associated with the post-wash zone 16,
in order to bring to temperature the liquid which is collected in
the relevant tank 32, 34, 36 in accordance with the stipulation of
a selected running program. The said heating devices 55, 56, 58 are
drivable accordingly by the control device 50.
[0067] Further, a heating device 57 of the water heater 9 is
drivable appropriately by the control device 50 in order as
required to adjust the temperature, in particular the minimum
temperature, of the final rinse liquid which is to be sprayed in
the final rinse zone 18, in the event that the final rinse liquid
which is to be sprayed has not yet been sufficiently brought to
temperature after passing through the device 42 for heat recovery
and/or after passing through the heat exchanger device 60.
[0068] A first exemplary embodiment of a heat exchanger device 60
which is downstream of the pre-wash zone 12 will be described in
more detail below with reference to the illustration in FIG. 2.
[0069] To be more precise, FIG. 2 schematically illustrates in more
detail a first exemplary embodiment of a wastewater energy recovery
system which is used for example with the conveyor dishwasher 2
which is illustrated schematically in FIG. 1 and described above.
In this exemplary embodiment of the wastewater energy recovery
system, a wastewater pump 61 is used which may be driven
appropriately by means of the above-mentioned control device 50.
The intake side of the wastewater pump 61 forms a flow connection
with a wash tank of a wash zone of the conveyor dishwasher 2.
[0070] In the text below, it is assumed that the intake side of the
wastewater pump 61 is connected to the wash tank 36 of the first
wash zone, as seen in the direction 8 of conveying the washware
(for example the pre-wash zone 12).
[0071] The wastewater pump 61 serves to supply, as required, wash
liquid which is produced as wastewater during operation of the
conveyor dishwasher 2 to the heat exchanger device 60, in which at
least a portion of the thermal energy of the supplied wash liquid
is transferred to the final rinse liquid which is to be sprayed in
the final rinse zone 18. Although it is not illustrated in FIG. 2,
it goes without saying that it is conceivable for further wash
zones to be connected between the final rinse zone 18 and the wash
zone 12, such as the main wash zone 14 and post-wash zone 16
described with reference to the illustration in FIG. 1.
[0072] As can also be seen from the illustration in FIG. 2, there
is associated with the wash zone 12 a corresponding wash system,
part of which is a wash pump (in this case, for example, the
pre-wash pump 33) by means of which the wash liquid collected in
the wash tank 36 is supplied to corresponding wash nozzles (in this
case, for example, the pre-wash nozzles 30). The wash liquid which
is sprayed in the wash zone 12 by the wash nozzles 30 at least
partially flows back into the wash tank 36 again due to gravity. In
this regard, the wash system shown in FIG. 2 is designed as a
recirculation system.
[0073] It should be emphasized in particular in this context
that--as indicated schematically in FIG. 2--the intake side of the
wastewater pump 61 forms a direct flow connection with the wash
tank 36. The delivery side of the wastewater pump 61, by contrast,
is connected to a corresponding heat exchanger device 60 in order,
as required, to supply wash liquid from the wash tank 36 to the
heat exchanger device 60.
[0074] The heat exchanger device 60 is preferably designed as a
counterflow heat exchanger in order to transfer, in a particularly
efficient manner, at least a portion of the thermal energy of the
wash liquid which is supplied to the heat exchanger device 60 to
the fresh (cold) water which is to be sprayed in the final rinse
zone 18 as final rinse liquid, and to heat this fresh water
accordingly.
[0075] After it has passed through the heat exchanger device 60,
the wash liquid is then supplied to a wastewater network 63 by
means of a wastewater line 62.
[0076] As indicated schematically in FIG. 2, the wash tank 36 of
the wash zone 12 is provided with a level sensor 64, by means of
which the liquid level in the wash tank 36 is preferably detected
continuously or at predefined times or in the case of predefined
events.
[0077] According to the invention, the control device 50 is
designed to drive the wastewater pump 61 depending on a quantity of
wastewater which is actually currently produced during operation of
the conveyor dishwasher 2. In other words, if during operation of
the conveyor dishwasher 2 no wastewater which is to be removed from
the conveyor dishwasher 2 or the wash tank 36 of the wash zone 12
is produced, the control device 50 switches off the wastewater pump
61, preferably automatically, such that no wash liquid is supplied
to the heat exchanger device 60.
[0078] In particular in the case of the exemplary embodiment of the
wastewater energy recovery system that is illustrated in FIG. 2, it
is provided for the control device 50 of the conveyor dishwasher 2
to be designed to drive appropriately, that is to switch on or off,
the wastewater pump 61 depending on a liquid level in the wash tank
36, which is detected with the aid of a level sensor 64.
[0079] Instead of driving the wastewater pump 61 in dependence on a
liquid level which is detected in the wash tank 36, it goes without
saying, however, that it is also conceivable for the control device
50 to be designed to drive the wastewater pump 61 appropriately,
depending on a predefined event and/or depending on an operating
cycle and/or operating state of the conveyor dishwasher 2. The
essential point here is that the wastewater pump 61 is only driven
and switched on if wash liquid which is to be removed from the
conveyor dishwasher 2 as wastewater, and which can thus be used for
energy recovery in the heat exchanger device 60, is actually
produced during operation of the conveyor dishwasher 2.
[0080] In the embodiment of the wastewater energy recovery system
according to the invention which is illustrated schematically in
FIG. 2, it is in particular provided for the control device 50 to
switch off the wastewater pump 61, preferably automatically, when
the liquid level in the wash tank 36, which is detected with the
aid of the level sensor 64, falls below a predefined or
predefinable first level, wherein the wastewater pump 61 is
switched on again, preferably automatically, as soon as the liquid
level in the wash tank 36 exceeds a predefined or predefinable
second level, wherein said second level preferably corresponds to
the above-mentioned first level. The first and/or second level at
which the wastewater pump 61 is switched on and off is preferably
selected such that it is ensured that a sufficient quantity of wash
liquid is always present in the wash tank 36 to be able to carry
out the wash process in the wash zone 12 in the conventional
way.
[0081] As also schematically illustrated in FIG. 2, the wastewater
energy recovery system shown there is further provided with a hot
water preparation apparatus 65 which is designed such that it is
independent of the heat exchanger device 60. By means of said hot
water preparation apparatus 65, hot water of the final rinse liquid
which is to be sprayed in the final rinse zone 18 is prepared, in
particular when the thermal energy which is transferred to the
final rinse liquid, which is to be sprayed in the final rinse zone
18, in the heat exchanger device 60 is not sufficient to heat the
final rinse liquid to a predefined or predefinable minimum
temperature when no wash liquid is supplied to the heat exchanger
device 60 and/or when the quantity of wash liquid which is supplied
to the heat exchanger device 60 per unit time is not sufficient to
heat the final rinse liquid which is to be sprayed in the final
rinse zone 18 to the predefined or predefinable minimum
temperature.
[0082] A situation of this kind occurs for example when the wash
system is started up, specifically when the liquid level in the
wash tank 36 falls below a defined level (first level) and thus a
condition is present in which no wash liquid can be removed from
the conveyor dishwasher 2 as wastewater and thus no energy can be
recovered from the wastewater in the heat exchanger device 60.
[0083] In this case, the required energy for heating the fresh
water which is to be sprayed in the final rinse zone 18 as final
rinse liquid to the required final rinse temperature has to be
provided with the aid of hot water preparation which is independent
of the heat exchanger device 60.
[0084] For this purpose, in the wastewater energy recovery system
according to the embodiment illustrated schematically in FIG. 2, a
hot water preparation apparatus 65 that is internal to the
dishwasher is used. This hot water preparation apparatus 65 may be
used in addition to the water heater 9 shown in FIG. 1, or instead
of the water heater 9 shown there. In either case, the hot water
preparation apparatus 65 is designed to heat up the final rinse
liquid which is to be sprayed in the final rinse zone to the
predefined or predefinable minimum temperature for the final rinse
liquid using electrical energy, steam, gas or hot water.
[0085] As also illustrated schematically in FIG. 2, as an
alternative or in addition to the hot water preparation apparatus
65 that is internal to the dishwasher, the hot water preparation
that is to be undertaken as required may be performed by means of
an external hot water preparation apparatus (not explicitly
illustrated in FIG. 2). It is conceivable in this context for
example for the conveyor dishwasher 2 to form a flow connection or
to be able to form a flow connection with an external hot water
preparation apparatus, for example a centralized hot water supply
provided in the building, by means of a hot water connection 66, in
order as required to supply the conveyor dishwasher 2 with hot
water which serves to be sprayed in the final rinse zone 18 as the
final rinse liquid, or which serves to heat the final rinse liquid
which is to be sprayed in the final rinse zone 18, for example by
means of a heat exchanger or heat pump system.
[0086] Preferably, in this case the control device 50 is designed
to activate the hot water connection 66 when the thermal energy
which is transferred to the final rinse liquid, which is to be
sprayed in the final rinse zone 18, in the heat exchanger device 60
is not sufficient to heat the final rinse liquid to the predefined
or predefinable minimum temperature, when no wash liquid is
supplied to the heat exchanger device 60, and/or when the quantity
of wash liquid which is supplied to the heat exchanger device 60
per unit time is not sufficient to heat the final rinse liquid
which is to be sprayed in the final rinse zone 18 to the predefined
or predefinable minimum temperature.
[0087] A further exemplary embodiment of a wastewater energy
recovery system will be described in more detail below with
reference to the illustration in FIG. 3. The wastewater energy
recovery system which is illustrated schematically in FIG. 3 is
suitable--as indeed is the wastewater energy recovery system shown
in FIG. 2--in particular for use in a wash zone, in particular the
first wash zone, as seen in the direction of conveying the washware
(pre-wash zone 12), in order to use the wash liquid that is
produced as wastewater in this wash zone (pre-wash zone 12) for
heat recovery.
[0088] Unlike the wastewater energy recovery system according to
the schematic illustration in FIG. 2, however, in the case of the
wastewater energy recovery system according to FIG. 3 it is
provided for the intake side of the wastewater pump 61 not to form
a direct flow connection with the wash tank 36 of the wash zone 12.
Rather, in this case the intake side of the wastewater pump 61
forms or is able to form a flow connection with an auxiliary tank
67. This auxiliary tank 67 forms a flow connection with the wash
tank 36 of the wash zone 12 by means of an overflow or similar
bypass line, such that the wash liquid that is produced as
wastewater in the wash zone 12 reaches the auxiliary tank 67 and is
subject to interim storage there.
[0089] In this way, it is ensured that the wash liquid (wastewater)
stored in the auxiliary tank 67 can no longer be recirculated in
the wash zone 12, since--as already explained in conjunction with
the embodiment according to FIG. 2--the intake side of the wash
pump 33 of the wash system associated with the wash zone 12 is
connected to the wash tank 36.
[0090] The wastewater which is subject to interim storage in the
auxiliary tank 67 is supplied, as required, with the aid of the
wastewater pump 61 to a heat exchanger device 60 which is
preferably designed as a counterflow heat exchanger and serves to
transfer at least a portion of the thermal energy of the wash
liquid which is supplied as wastewater to the heat exchanger device
60 to the final rinse liquid which is to be sprayed in the final
rinse zone 18.
[0091] By providing an auxiliary tank 67 of this kind, it is
ensured in particular that even when the conveyor dishwasher 2 is
started up--that is, in a condition in which no wastewater which is
to be removed and can be used for heat recovery is produced during
operation of the conveyor dishwasher 2--the heat exchanger device
60 can always be provided with wastewater from the auxiliary tank
67.
[0092] Nonetheless, it is, however, also advantageous in the case
of the wastewater energy recovery system according to FIG. 3 to
provide hot water preparation which is independent of the heat
exchanger device 60, for example in the form of a hot water
preparation apparatus 65, wherein in this case too the hot water
preparation apparatus 65 which is illustrated schematically in FIG.
3 may be designed to have the same construction as the water heater
9 shown in FIG. 1, or the hot water preparation apparatus 65 which
is illustrated schematically in FIG. 3 may replace the water heater
9 shown in FIG. 1.
[0093] The hot water preparation apparatus 65 is activated by the
control device 50 at least when the thermal energy which is
transferred to the final rinse liquid, which is to be sprayed in
the final rinse zone 18, in the heat exchanger device 60 is not
sufficient to heat the final rinse liquid to the predefined or
predefinable minimum temperature.
[0094] As also in the case of the wastewater energy recovery system
illustrated schematically in FIG. 2, in the case of the embodiment
illustrated schematically in FIG. 3 it is provided for the hot
water preparation apparatus 65 to be designed in particular to heat
up the final rinse liquid which is to be sprayed in the final rinse
zone 18 to the predefined or predefinable minimum temperature using
electrical energy, steam, gas or hot water.
[0095] In the case of the wastewater energy recovery system shown
in FIG. 3, too, a wastewater line 62 is used to supply the wash
liquid which is removed as wastewater from the conveyor dishwasher
2--once it has passed through the heat exchanger device 60--to a
wastewater network 63.
[0096] The invention is not restricted to the embodiments
illustrated in the drawings but results from an overall view of all
the features and aspects disclosed herein.
[0097] In particular, the wastewater energy recovery system
according to the invention is designed to supply wash liquid,
continuously or cyclically, to the heat exchanger device 60 with
the aid of the wastewater pump 61. In this context, the temperature
of the wash liquid, depending on the machine type and the selected
treatment program, is between 40.degree. C. and 75.degree. C. After
flowing through the heat exchanger device 60, the wash liquid
(wastewater) is cooled by approximately 20.degree. C. to 30.degree.
C., to approximately 20.degree. C. to 60.degree. C.
[0098] The thermal energy is transferred to fresh water flowing in
counterflow, with the result that said fresh water is heated by the
same temperature difference as that by which the wastewater cools.
Then, as required, the preheated fresh water is heated by a hot
water preparation apparatus 65, such as a water heater 9, to the
required process temperature of at least 65.degree. C. or at least
80.degree. C.
[0099] In particular, in this context it is also conceivable to
provide, in the wash tank 36, the wash water supply line to the
heat exchanger device 60, and/or the final rinse liquid outlet or
the downstream line for the fresh water that is heated or
pre-heated in the heat exchanger device 60, corresponding
temperature sensors so that the control device 50 can activate the
wastewater pump 61 and/or the hot water preparation apparatus 65
and/or the hot water connection 66 appropriately.
* * * * *