U.S. patent application number 10/576986 was filed with the patent office on 2007-05-10 for system and method for drying objects.
This patent application is currently assigned to EISENMANN MASCHINENBAU GMBH & CO. KG. Invention is credited to Michael Hager, Apostolos Katefidis, Werner Swoboda.
Application Number | 20070101607 10/576986 |
Document ID | / |
Family ID | 34584739 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070101607 |
Kind Code |
A1 |
Katefidis; Apostolos ; et
al. |
May 10, 2007 |
System and method for drying objects
Abstract
The invention to a system which is used to dry objects,
comprising a drying cubicle (1), known per se, wherein the objects
are exposed to hot air. The process waste air from a high
temperature fuel cell (10) is used as hot air which is directly
introduced into the drying cubicle (1). The high pressure fuel cell
(10) is operated, according to thermal energy required for the
drying process, whereby according to the extent thereof electric
energy is also accumulated and is disregarded when controlling the
high temperature fuel cell (10), whereby electrical consumers for
said electrical energy can always be found. The inventive system
and method for drying objects are relatively inexpensive and have a
very high energy utilisation ratio.
Inventors: |
Katefidis; Apostolos;
(Gaertringen, DE) ; Hager; Michael; (Schoenaich,
DE) ; Swoboda; Werner; (Boeblingen, DE) |
Correspondence
Address: |
FACTOR & LAKE, LTD
1327 W. WASHINGTON BLVD.
SUITE 5G/H
CHICAGO
IL
60607
US
|
Assignee: |
EISENMANN MASCHINENBAU GMBH &
CO. KG
Tubinger Strasse 81,
Boeblingen
DE
71032
|
Family ID: |
34584739 |
Appl. No.: |
10/576986 |
Filed: |
October 2, 2004 |
PCT Filed: |
October 2, 2004 |
PCT NO: |
PCT/EP04/11036 |
371 Date: |
December 27, 2006 |
Current U.S.
Class: |
34/371 ;
431/115 |
Current CPC
Class: |
F26B 15/12 20130101;
F26B 23/02 20130101; F26B 2210/12 20130101 |
Class at
Publication: |
034/371 ;
431/115 |
International
Class: |
F23C 9/00 20060101
F23C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2003 |
DE |
103 49 090.6 |
Claims
1. System for drying objects, comprising: a drying cubicle
including at least one section in which the objects are exposed to
hot air; a heating device which heats the hot air introduced into
the drying cubicle, wherein the heating device includes at least
one high temperature fuel cell the process waste air from which can
be fed to the drying cubicle as hot air; there is provided a
control system which so operates the high temperature fuel cell
regardless of the electrical energy generated thereby that the
thermal energy generated thereby meets the requirement in the
drying cubicle; and supplies whatever quantity of electrical energy
is generated by the high temperature fuel cell to other electrical
consumers.
2. System according to claim 1, wherein the control system utilises
the electrical energy of the high temperature fuel cell primarily
for electrical consumers belonging to the system itself and
secondarily for electrical consumers located outside the
system.
3. System according to claim 2, wherein the control system utilises
the electrical energy of the high temperature fuel cell within the
system itself primarily for the electrical consumers used for heat
generation, for example, infrared radiators, and secondarily for
other electrical consumers, for example, electrical drives.
4. System according to claim 1, wherein the control system supplies
the surplus electrical energy of the high temperature fuel cell not
consumed in the system itself primarily to an energy accumulator
and secondarily to the general electrical mains supply.
5. System according to claim 1, wherein there is provided a
regenerative post-combustion device to which air extracted from the
drying chamber and containing hydrocarbon is fed for
purification.
6. System according to claim 5, wherein a heat exchanger is
provided in which a thermal exchange takes place between hot air
drawn from the regenerative post-combustion device and air drawn
from the ambient atmosphere and fed to the drying cubicle.
7. Method for drying objects, wherein air is heated and the objects
are subjected to the influence of the heated air, the method
comprising: the process waste air from a high temperature fuel cell
is used as hot air; the high temperature fuel cell is operated
according to the requirement for thermal energy of the drying
process regardless of the electrical energy generated by said high
temperature fuel cell; and, the electrical energy generated by the
high temperature fuel cell is fed in whatever quantity is obtained
to electrical consumers.
8. Method according to claim 7, wherein the electrical energy of
the high temperature fuel cell is utilised primary for electrical
consumers belonging to the system itself and secondarily for
electrical consumers located outside the system.
9. Method according to claim 7, wherein the electrical energy of
the high temperature fuel cell is utilised within the system itself
primarily for the electrical consumers used for heat generation,
for example, infrared radiators, and secondarily for other
electrical consumers, for example, electrical drives.
10. Method according to claim 7, wherein the surplus electrical
energy of the high temperature fuel cell not consumed in the system
itself is supplied primary to an energy accumulator and secondarily
to the general electrical mains supply.
11. Method according to claim 7, wherein the air produced during
drying and containing hydrocarbon is post-combusted
regeneratively.
12. Method according to claim 11, wherein the air heated by
post-combustion is used for heating air which is drawn from the
ambient atmosphere and fed to the drying process.
13. Method according to claim 7, wherein upon attainment of the
operating temperature of the fuel cell the fuel gas is heated at
least partially by electrical energy supplied from the fuel cell
itself.
14. Method according to claim 7, wherein the process waste air from
the high temperature fuel cell forms an inert atmosphere in the
drying cubicle.
Description
[0001] The invention relates to a system for drying objects,
comprising [0002] a) a drying cubicle having at least one section
in which the objects are exposed to hot air; [0003] b) a heating
device which heats the air introduced into the drying cubicle, and
to a method for drying objects whereby air is heated and the
objects are exposed to the influence of heated air.
[0004] For environmental and cost reasons increasing attention
being is being paid to the management of energy when drying
objects. In particular when drying large, painted objects such as
vehicle bodies, considerable quantities of energy must be used, so
that energy savings result in considerable reductions in cost.
[0005] With known driers of the type described in the introduction,
as used in particular for drying freshly-painted vehicle bodies,
thermal post-combustion devices are used as the heating device for
the drying air. These thermal post-combustion devices contribute to
energy saving in so far as they extract by combustion the energy
content of the air containing hydrocarbon drawn from the drying
cubicle, while simultaneously purifying this air.
[0006] In general, however, the energy content of the waste air
from the drying cubicle is insufficient for attaining the
combustion temperature required for complete purification. The
waste air stream from the drier to be disposed of must therefore be
heated to a temperature necessary for the complete oxidation of the
organic components contained in said waste drying air. Suitable
fuels must be added for this purpose. The hot air leaving the
thermal post-combustion devices is now supplied to one or more heat
exchangers, which transfer a part of their heat energy to the air
circulating in the drying cubicle. Direct introduction of the
combustion air from the thermal post-combustion device into the
drying cubicle is to be avoided because of foreign matter still
present or produced in the waste air, which may impair the quality
of the paint surface, and because of inferior temperature control.
The air leaving the thermal post-combustion device and cooled in
the heat exchangers is then conducted to the flue at a temperature
which does not differ very widely from the temperature prevailing
inside the drying cubicle. A value of 160.degree. C. is
typical.
[0007] Although considerable energy savings are achieved with such
known driers, further possible ways of saving energy are sought.
Moreover, the heat exchangers which must be used for the
above-mentioned reasons entail relatively high equipment cost and
complexity.
[0008] It is the object of the present invention to specify a
device and a method of the type mentioned in the introduction with
which drying can be carried out with lower equipment cost and
complexity and with the use of less primary energy.
[0009] This object is achieved with regard to the device in that
[0010] c) the heating device includes at least one high temperature
fuel cell the process waste air from which can be fed as hot air to
the drying cubicle; [0011] d) a control system is provided which
[0012] da) operates the high temperature fuel cell in such a way
that the thermal energy generated by it meets the requirement in
the drying cubicle regardless of the electrical energy generated by
said high temperature fuel cell; [0013] db) the electrical energy
generated by the high temperature fuel cell is supplied to other
consumers in whatever quantity is obtained.
[0014] It is known that in high temperature fuel cells two types of
energy, electrical and thermal energy, are obtained.
[0015] It is also known that in cases when both types of energy can
be used a utilisation ratio of up to 90% of the primary energy can
be achieved. Hitherto, however, high temperature fuel cells have
been used with the primary intention of generating as much
electrical energy is possible; suitable consumers were then sought
for the thermal energy which was necessarily also produced. When
such consumers were not present the thermal energy was lost.
[0016] According to the invention this known concept for operating
high temperature fuel cells is reversed: for use in driers the fuel
cell is regarded primarily as a heating device which supplies
thermal energy for heating the drying air. The high temperature
fuel cell is therefore operated according to the amount of thermal
energy required in the drying cubicle. It is initially immaterial
how much electrical energy is necessarily also obtained in this
process. For this electrical energy the principle now applies that
consumers to which this electrical energy can be supplied will
always be found. This is the more easily the case because
electrical energy is a higher-value energy form more versatile in
its applications than thermal energy.
[0017] For the utilisation of the electrical energy obtained the
following philosophy is advantageously applied: the control system
uses the electrical energy from the high temperature fuel cell
primarily for electrical consumers belonging to the system itself
and secondarily for electrical consumers located outside the
system. In this way the system is largely self-sufficient with
regard to electrical energy. Because the requirement for thermal
energy in driers can be very high, in many cases more electrical
energy is generated than the consumers in the system itself can
absorb. Only this surplus energy is then supplied to consumers
outside the system.
[0018] If the thermal energy generated by the high temperature fuel
cell is insufficient, in particular when starting the plant,
additional energy must be drawn from the electrical mains
supply.
[0019] Within the system itself the electrical energy of the high
temperature fuel cell is used primarily for the electrical
consumers used for generating heat, for example infrared radiators,
and only secondarily for other electrical consumers, for example
electrical drives.
[0020] This principle, too, reflects the fact that, according to
the invention, the high temperature fuel cell is regarded as a
source of thermal energy. To the extent that a surplus of
electrical energy is present, it can be used for heating the
objects to be dried, which in turn reduces the requirement for
heated air. The fuel cell may then be operated with a lower total
output if the most self-sufficient possible operation of the whole
system is sought.
[0021] If surplus electrical energy still remains after feeding of
the electrical consumers of the system used for generating heat,
this surplus electrical energy is used as far as possible for
electrical drives within the system itself, for example, the motors
of fans or conveying devices.
[0022] Only when the electrical energy cannot be consumed within
the system itself is the surplus energy supplied, in an
advantageous embodiment of the system according to the invention,
primarily to an energy accumulator and secondarily to the general
electrical mains supply. As energy accumulators, both a storage
battery and an electrolysis device for producing hydrogen are
possible. The energy accumulators also increase the
self-sufficiency of the plant, since energy can be drawn from them
in phases in which the electrical and/or thermal output of the high
temperature fuel cell is insufficient.
[0023] In known systems of the type mentioned in the introduction
thermal post-combustion devices are used, as already mentioned, to
obtain the considerable quantities of energy required and at the
same time to purify the waste air from the drier. Because, in
systems according to the invention, the preponderant part of the
heated drying air originates in any case from the high temperature
fuel cell, a regenerative post-combustion device may be provided
for purifying the air containing hydrocarbon which leaves the
drying cubicle. The regenerative post-combustion device carries out
the purification process with lower energy consumption than a
thermal post-combustion device. The surplus thermal energy thus
made available is not sufficient for operating the drier.
[0024] Nevertheless, according to a further preferred embodiment of
the invention, it may be advantageous to provide a heat exchanger
in which a thermal exchange takes place between the hot air
extracted from the regenerative post-combustion device and the air
drawn from the ambient atmosphere and fed to the drying cubicle. In
this heat exchanger, therefore, further heat is extracted from the
gas leaving the regenerative post-combustion device and now having
only a low temperature, and supplied for utilisation within the
drying cubicle.
[0025] The above-mentioned object is achieved, with regard to the
method for drying objects, in that [0026] a) the process waste air
of a high temperature fuel cell is used as hot air; [0027] b) the
high temperature fuel cell is operated according to the requirement
for thermal energy in the drying process, regardless of the
electrical energy generated in such operation; [0028] c) the
electrical energy generated by the high temperature fuel cell is
supplied to electrical consumers in whatever quantity is
obtained.
[0029] The advantages of the method according to the invention
correspond analogously to the above-mentioned advantages of the
device according to the invention.
[0030] Advantageous embodiments of the method according to the
invention, which likewise have their analogies in the embodiments
of the inventive device explained above, are specified in claims 8
to 12.
[0031] Because electrical energy is generally freely available with
the method according to the invention, it is appropriate, upon
reaching the operating temperature of the fuel cell, to heat the
fuel gas at least partially with electrical energy. Thermal
efficiency is thereby increased. The exit temperature of the
process waste air is thus increased to approximately 600.degree.
C.
[0032] If an inert atmosphere is required in the drying cubicle, in
particular when processing UV-curing paints, the process waste air
of the high temperature fuel cell may directly form the inert
atmosphere. It is inherently sufficiently clean and, especially
when natural gas is used as the fuel gas, consists almost entirely
of carbon dioxide, which plays an important part in the curing of
UV paints
[0033] Embodiments of the invention are explained in more detail
below with reference to the drawings, in which:
[0034] FIG. 1 is a schematic representation of a system for drying
vehicle bodies;
[0035] FIG. 2 shows in somewhat more detail a high temperature fuel
cell contained in the system of FIG. 1, and its immediate
environment;
[0036] FIG. 3 shows a second embodiment of a system according to
the invention.
[0037] The system for drying vehicle bodies shown in the drawings
comprises as central components the actual drying cubicle 1, which
is subdivided by a partition 2 into a pre-heating zone the 3 and a
main drying zone 4. The freshly-painted vehicle bodies are first
introduced by means of a conveying system (not shown) into the
pre-heating zone 3, where they are heated to a temperature of
somewhat below 100.degree. C. through the combined effect of hot
air introduced via a line 5 and electrically energised infrared
radiators 6. As this happens the major part of the solvent is
expelled. The air, with a high solvent content, is extracted from
the drying cubicle via a line 7 and supplied to a post-treatment
described below.
[0038] The vehicle bodies pre-heated in this way then enter the
main drying zone 4, which in turn may be subdivided into a heating
and a holding zone. The greater length of the main drying zone 4 in
comparison to the pre-heating zone 3 indicates that the vehicle
bodies remain in the main drying zone 4 longer than in the
pre-heating zone 3. In a continuous-transit method, these different
treatment times are reflected in different plant lengths.
[0039] Within the main drying zone 4, the vehicle bodies are heated
to a temperature of 180.degree. C., on the one hand with hot air,
which is also supplied via the line 5 and, on the other, with
process waste air which is fed via lines 8. The hot air inside the
main drying section 4 is circulated by means of fans 9 for uniform
heating. At the temperature referred to the remaining solvents are
removed from the paint on the vehicle bodies; the paint is fully
cured.
[0040] To generate the hot process waste air fed to the main drier
section 4 via the lines 8, one or more high temperature fuel cells
10 are used. Such high temperature fuel cells 10 may be operated
with practically all fuel gases containing hydrocarbon, in
particular natural gas or biogas, sewage gas, refuse dump gas or
other residual industrial gases, such as are also obtained in
painting technology. The fuel gas is fed to the high temperature
fuel cells 10 via the line 21. In the fuel cell 10 it is heated to
operating temperature by means of an electrical heating device 22
(see FIG. 2). During start-up of the plant the heating device 22 is
fed with externally-generated current and after reaching of the
operating temperature is operated with current generated by the
high temperature fuel cell 10 itself. This is because a surplus of
electrical energy is generally present, whereas the thermal energy
of the high temperature fuel cell 10 must be fed as completely as
possible to the drying cubicle 1.
[0041] The air required for combustion is supplied via a line 23
connected to the ambient atmosphere, in which line 23 a
controllable flap 24 is located.
[0042] In the interior of the high temperature fuel cell 10 a
temperature of approximately 650.degree. C. is present. Process
waste air is produced and leaves the high temperature fuel cell 10
at a temperature of approximately 600.degree. C. This process waste
air is practically free of impurities, so that it can be fed
directly into the drying cubicle 1 via the lines 8 without the
interposition of a heat exchanger. If UV-curing paints are
processed in the drying cubicle 1, the inert atmosphere required
for this process may be formed directly from the process waste air,
by far the predominant part of which consists of carbon dioxide, in
particular when natural gas is used as the fuel gas.
[0043] Barely 60% of the total energy is obtained as electrical
energy and 40%, estimated conservatively, as thermal energy.
[0044] Before the use of the different types of energy and the
control system of the high temperature fuel cell 10 employed for
this purpose are discussed in detail, the description of the total
system will first be completed:
[0045] The waste air with high solvent content leaving the drying
cubicle 1 via the line 7 is supplied first to a regenerative
post-combustion device 11 in which the organic impurities are burnt
and the waste air is thus purified. This purified air, having a
temperature of approximately 230.degree. C., is fed by means of a
fan 12 to a flue 13 either directly or via a heat exchanger 14. In
the heat exchanger 14 the hot purified air dissipates a proportion
of its heat to atmospheric air at approximately 20.degree. C. which
is sucked in by means of a further fan 15, forced through the heat
exchanger 14 and is then introduced into the drying cubicle 1 at a
temperature of approximately 180.degree. C. The line 5 leads
further to a controllable flap 25 and into the line 24 between the
flap 24 and the high temperature fuel cell 10. As is apparent, the
quantity and temperature of the air fed to the high temperature
fuel cell 10 can be determined by adjusting the flaps 24 and
25.
[0046] The energy management of the total system is effected by
means of an electronic control system in the following manner:
[0047] The primary control value is the quantity of thermal energy
required in the main drying zone 4. The fuel cell 10 is so operated
that the required thermal energy is generated and the corresponding
quantities of heated waste air can be fed into the main drying zone
4 via the lines 8. The electrical energy obtained at the same time
is disregarded. With this electrical energy the following procedure
is adopted: the electrical consumers of the system itself used for
obtaining heat, in particular the infrared radiators 6 and the
electrical heating device 22, are first supplied via the line 18.
Surplus electrical energy is fed via the lines 17 to fans 12, 15
present within the system. With conventional drier systems there
still remains surplus electrical energy, with which electrical
drives, for example of the conveyor transporting the vehicle
bodies, are supplied via the line 19. If electrical energy still
remains, it is either discharged into the electrical mains network
via the line 20 or temporarily stored, for example in the form of
electrolytic hydrogen generation.
[0048] The embodiment of a drier system shown in FIG. 3 differs
from that described above with reference to FIGS. 1 and 2 only in
that no post-combustion device and no heat exchanger connected
downstream thereof, which transfers heat from the air leaving the
regenerative post-combustion device to the air drawn from the
ambient atmosphere, is provided. Instead, the line 5 leads via a
controllable flap 28 into the line 26 which leads to the flue 13;
the line 27 through which fresh air is drawn in also contains a
controllable flap 29 and leads into the line 5 between the fan 15
and the line 26. As is apparent, the quantity and temperature of
the air supplied to the drying cubicle 1 can be determined using
the flaps 28 and 29.
* * * * *