EP1676082B1 - System and method for drying objects - Google Patents

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.

Description

1. a) einer Trocknerkabine, die mindestens einen Abschnitt aufweist, in welchem die Gegenstände heißer Luft aus gesetzt sind;
2. b) einer Heizeinrichtung, welche die in die Trocknerkabine eingeführte Luft erhitzt;

sowie
ein Verfahren zum Trocknen von Gegenständen, bei dem Luft erhitzt und die Gegenstände mit erhitzter Luft beaufschlagt werden.The invention relates to a system for drying objects with

1. a) a dryer booth having at least a portion in which the objects of hot air are set out;
2. b) a heater which heats the air introduced into the dryer booth;

such as
a method for drying objects, in which air is heated and the articles are exposed to heated air.

Both environmental and cost reasons, the handling of energy when drying objects is increasingly paid attention. In particular, when drying large, painted objects, such as vehicle bodies, considerable amounts of energy must be used, so that energy savings lead to significant cost reductions.

In known dryers of the type mentioned above, as used in particular for drying freshly painted vehicle bodies, are used as a heater for the dryer air thermal afterburning equipment use. These thermal afterburners already contribute to energy saving in so far as, as it extracts from the dryer cabin, hydrocarbon-containing air by combustion their energy content while cleaning this air at the same time, see, for example US Pat. No. 4,656,758 ,

In general, however, the energy content of the exhaust air of the dryer booth is not sufficient to achieve the combustion temperature required for complete cleaning. The dryer-waste air stream to be disposed of must therefore be heated to a temperature necessary for complete oxidation of the organic constituents contained in the dryer exhaust air. For this purpose, appropriate fuels are to be supplied. The hot air leaving the thermal afterburning apparatus is now fed to one or more heat exchangers by transferring some of their heat energy to the air circulated in the dryer booth. A direct introduction of the combustion air of the thermal afterburning device in the dryer cabin is due to the sometimes disturbing the quality of the paint surface in the exhaust still verhandenen or resulting foreign substances and the schchtteren temperature control to avoid. The air originating from the thermal post-combustion device and cooled in the heat exchanger (s) is then fed to the chimney at a temperature which is not too different from the temperature prevailing inside the dryer booth. Typical is a value of 160 ° C.

Although considerable energy savings have already been achieved with these known dryers, further possibilities are sought to save energy. In addition, the heat exchangers, which must be used for the reasons mentioned above, a relatively high expenditure on equipment.

Object of the present invention is to provide a device and a method of the type mentioned, with which can be dried with less expenditure on equipment with less use of primary energy.

• c) die Heizeinrichtung mindestens eine Hochtemperatur-Brennstoffzelle umfaßt, deren Prozess-Abluft der Trocknerkabine als heiße Luft zuführbar ist;
• d) eine Steuerung vorgesehen ist, welche
  • da) die Hochtemperatur-Brennstoffzelle ungeachtet der von ihr erzeugten elektrischen Energie so betreibt, daß die von ihr erzeugte thermische Energie dem Bedarf in der Trocknerkabine entspricht;
  • db) die von der Hochtemperatur-Brennstoffzelle erzeugte elektrische Energie in der jeweils anfallenden Menge anderen Verbrauchern zuführt.

This object is achieved, as far as the device is concerned, in that

• c) the heating device comprises at least one high-temperature fuel cell, the process exhaust air of the dryer cubicle can be supplied as hot air;
• d) a controller is provided, which
  • da) operating the high-temperature fuel cell regardless of the electrical energy generated by it, so that the thermal energy generated by it corresponds to the demand in the dryer cubicle;
  • db) supplies the electrical energy generated by the high-temperature fuel cell in the respective amount accumulating other consumers.

It is known that in high-temperature fuel cells, two types of energy, namely electrical and thermal energy incurred. It is also known that when both types of energy can be used, a primary energy efficiency of up to 90% can be achieved. However, hitherto, the high-temperature fuel cells have been used primarily with the intention of generating as much electrical energy as possible; for the thermal energy, which inevitably resulted, then appropriate consumers were sought. Where such consumers did not exist, the thermal energy was lost.

According to the invention, this known concept of operating high-temperature fuel cells is turned upside down. For use in dryers, the fuel cell is primarily regarded as a heating device which supplies thermal energy for heating the dryer air. Accordingly, the high-temperature fuel cell is also operated according to the demand for thermal energy in the dryer booth. It is initially irrelevant how much electrical energy inevitably accumulates in this context. For this electrical energy is now the principle that always find consumers to whom this electrical energy can be supplied. This is all the easier as electrical energy is a higher energy form, which is more versatile than thermal energy.

For the utilization of the resulting electrical energy, the following philosophy is advantageously followed: The controller employs the electrical energy of the high-temperature fuel cell primarily for electrical equipment belonging to the plant itself and secondarily for electrical consumers located outside the plant. In this way, the system is largely self-sufficient in terms of electrical energy. Since the demand for thermal energy in dryers can be very high, in many cases more electrical energy is generated than consumers in the plant can lose weight themselves. Only this excess energy is then dissipated to consumers outside the plant itself.

If the thermal energy generated by the high-temperature fuel cell, in particular when starting the system, not sufficient, must be fed from the electrical network become.

Within the plant itself, the electrical energy of the high-temperature fuel cell is primarily used for the heat generation serving electrical consumers, eg. B. for infrared emitters, and secondarily for other electrical consumers, eg. As electric drives used.

Again, this principle reflects that, according to the invention, the high-temperature fuel cell is considered as a source of thermal energy. So far as electrical energy is excessive, this can be used to heat the objects to be dried, which in turn reduces the need for heated air. The fuel cell can then be operated at a lower power overall, if a self-sufficient operation of the entire system is desired.

If, after the food serving the heat generating electrical consumers of the plant still electrical energy remains, this is used for electrical drives as possible within the plant itself, so for example for the motors of blowers used or conveyors.

Only when the electrical energy can not be consumed within the system itself, in an advantageous embodiment of the system according to the invention, the excess energy is supplied primarily to an energy storage and secondary to the general electrical network. As energy storage, both a battery and an electrolysis device for generating hydrogen come into consideration. Also the energy storage increase the autarky of the plant, since in phases, in which the electrical and / or thermal performance of the high temperature fuel cell is insufficient, energy can be removed.

In known systems of the type mentioned above, as mentioned above, thermal afterburning used to recover the considerable amounts of energy that are needed, while cleaning the dryer exhaust air. Since in systems according to the invention the heated dryer air originates from the high-temperature fuel cell in most cases, a regenerative afterburning apparatus can be provided for cleaning the hydrocarbon-containing air leaving the drying chamber. This performs the cleaning process with less energy than a thermal post-combustion device. The resulting excess thermal energy is insufficient to operate the dryer.

Nevertheless, according to a further preferred embodiment of the invention, it may be expedient to provide a heat exchanger in which a heat exchange takes place between the hot air removed from the regenerative afterburning apparatus and air taken from the outside atmosphere and supplied to the drier booth. In this heat exchanger, therefore, the gas leaving the regenerative afterburning device, which has only a low temperature, is taken off further heat, in order to supply it to use within the dryer booth.

1. a) als heiße Luft die Prozess-Abluft einer Hochtemperatur-Brennstoffzelle verwendet wird;
2. b) die Hochtemperatur-Brennstoffzelle ungeachtet der dabei erzeugten elektrischen Energie entsprechend dem Bedarf an thermischer Energie bei dem Trocknervorgang betrieben wird;
3. c) die von der Hochtemperatur-Brennstoffzelle erzeugte elektrische Energie in der jeweils anfallenden Menge elektrischen Verbrauchern zugeführt wird.

The above object is, as regards the method for drying of objects, solved by

1. a) as hot air, the process exhaust air of a high-temperature fuel cell is used;
2. b) the high-temperature fuel cell is operated in accordance with the need for thermal energy in the drying process, regardless of the electrical energy generated thereby;
3. c) the electrical energy generated by the high-temperature fuel cell is supplied in each case amount of electrical consumers.

The advantages of the method according to the invention correspond to the o. G. Advantages of the device according to the invention.

Advantageous embodiments of the method according to the invention, which likewise find their analogue in embodiments of the device according to the invention already explained above, are specified in claims 8 to 12.

Since electrical energy is generally available at leisure in the method according to the invention, it makes sense, after reaching the operating temperature of the fuel cell, to at least partially heat the fuel gas by electrical energy. This increases the thermal efficiency. The outlet temperature of the process exhaust air thus increases to about 600 ° C.

Where an inert atmosphere is required in the dryer cubicle, especially when processing UV-curing lacquers, the process exhaust air of the high-temperature fuel cell can directly form the inert atmosphere. It is sufficiently clean from home and consists almost exclusively of natural gas as fuel gas made of carbon dioxide, which plays an important role in the curing of UV coatings.

Figur 1

schematisch eine Anlage zum Trocknen von Fahrzeug- karosserien;

Figur 2

etwas detaillierter eine in der Anlage der Figur 1 enthaltene Hochtemperatur-Brennstoffzelle sowie deren nächste Umgebung;

Figur 3

eine zweite Ausführungsform einer erfindungsge- mäßen Anlage.

Embodiments of the invention will be explained in more detail with reference to the drawing; show it

FIG. 1

schematically a system for drying vehicle bodies;

FIG. 2

a little more detailed one in the annex of the FIG. 1 contained high-temperature fuel cell and their immediate vicinity;

FIG. 3

A second embodiment of a system according to the invention.

The system shown in the drawing for drying vehicle bodies comprises as a central component the actual dryer booth 1, which is divided by a partition wall 2 in a preheating zone 3 and a main drying zone 4. The freshly painted vehicle bodies are first introduced by means of a conveying system, not shown, in the preheating zone 3 and brought there by the combined effect of a introduced via a line 5 hot air and electrically operated infrared radiator 6 to a temperature of slightly below 100 ° C. The majority of the solvent is expelled. The highly solvent-containing air is removed via a line 7 of the dryer and fed to an aftertreatment described below.

The thus preheated vehicle bodies then pass into the main drying zone 4, which in turn can be divided once again into a warm-up and a holding zone.

Due to the greater length of the main drying zone 4 compared to the preheating zone 3, it is indicated that the vehicle bodies in the main drying zone 4 are longer than in the preheating zone 3. In a continuous flow process, these different treatment times are reflected in different plant lengths.

Within the main drying zones 4, the vehicle bodies are brought to a temperature of 180 ° C. on the one hand with hot air, which is likewise supplied via the line 5, and on the other hand with process exhaust air which is fed in via lines 8. The hot air within the main dryer section 4 is circulated for uniform heating by means of fans 9. At the described temperature, the remaining solvents escape from the paint on the vehicle bodies; the paint is cured.

One or more high-temperature fuel cells 10 are used to generate the hot process exhaust air fed via the lines 8 into the main dryer section 4. Such high-temperature fuel cells 10 can be operated with virtually all hydrocarbon-containing fuel gases, in particular with natural gas but also biogas, sewage gas, landfill gas or other industrial residual gases, such as those incurred in painting. The fuel gas is supplied to the high-temperature fuel cell 10 via the line 21. It is there with the help of an electric heater 22 (see. FIG. 2 ) brought to operating temperature. The heater 22 is powered during startup of the plant from external power and operated after reaching the operating temperature with the current generated by the high-temperature fuel cell 10 itself. This is because electrical Energy is generally present in excess, while the thermal energy of the high-temperature fuel cell 10 should be as completely as possible supplied to the dryer cubicle 1.

The air required for combustion is supplied via a connected to the outside atmosphere line 23 in which a controllable flap 24 is located.

Inside the high temperature fuel cell 10 there is a temperature of about 650 °. The result is a process exhaust air leaving the high-temperature fuel cell 10 at a temperature of about 600 ° C. This process exhaust air is virtually free of impurities so that it can be entered via lines 8 without interposing a heat exchanger directly into the dryer cabin 1, where a temperature of about 180 ° C is set. If 1 UV-curing lacquers are processed in the dryer cubicle, the inert atmosphere required for this purpose can be formed directly from the process exhaust air, which consists largely predominantly of carbon dioxide, especially when natural gas is used as fuel gas.

Almost 60% of the total energy is generated as electrical energy, more than 40% as thermal energy.

Before discussing the use of the various types of energy and the control of the high-temperature fuel cell 10 used for this purpose, first the description of the entire system is finished:

The drying oven 1 via the line 7 leaving, highly solvent-containing exhaust air is first fed to a regenerative afterburner 11, in which the organic pollutants burned, the Exhaust air is thus cleaned. This cleaned, about 230 ° C hot exhaust air is fed with the help of a fan 12 a chimney 13 either directly or by way of a heat exchanger 14. The hot cleaned air gives off some of its heat to atmospheric air of about 20 ° C, which sucked by means of another blower 15, pushed through the heat exchanger 14 and then via the above-mentioned line 5 into the dryer cabin 1 with a temperature of about 180 ° C is introduced. The conduit 5 continues to a controllable flap 25 and terminates between the flap 24 and the high-temperature fuel cell 10 in the conduit 24. By adjusting the flaps 24 and 25 can be seen the amount and the temperature of the high-temperature fuel cell 10 supplied air determined become.

The energy management of the entire system is carried out by means of an electronic control in the following manner:

The primary control variable is the need for thermal energy needed in the main dryer zone 4. The fuel cell 10 is operated so that the required thermal energy generated and the corresponding amounts of heated exhaust air via lines 8 in the main dryer zone 4 can be entered. In doing so, no consideration is given to the simultaneously occurring electrical energy. The procedure is as follows: First of all, the electrical loads of the system itself are supplied via the line 18, which are used to generate heat, in particular the infrared radiators 6 and the electric heating device 22. Excess electrical energy is supplied via the lines 17 to the system Blowers 12, 15 fed. In conventional dryer systems remains even now excess electrical energy, with which via the line 19 electrical drives, z. B. of the vehicle bodies transporting conveyor, are supplied. Then still remains electrical energy, this is either delivered via the line 20 in the electrical network or cached, for example in the form of an electrolytic hydrogen production.

This in FIG. 3 illustrated embodiment of a dryer plant differs from the above based on the FIGS. 1 and 2 described only in that no Nachverbrennungsvorrichtung and no downstream of this heat exchanger, which transfers heat from the regenerative afterburner air leaving the air sucked from the outside atmosphere, are provided. Instead, the line 5 opens via a controllable flap 28 in the leading to the chimney 13 line 26; the conduit 27, via which fresh air is sucked in; Also includes a controllable flap 29 and opens between the fan 15 and the line 26 in the line 5. About the flaps 28 and 29 can be seen clearly determine the amount and temperature of the dryer cabin 1 supplied air.

Claims (14)

1. System for drying objects, comprising:

   a) a drying cubicle including at least one section in which the objects are exposed to hot air;

   b) a heating device which heats the hot air introduced into the drying cubicle,
   characterised in that

   c) the heating device includes at least one high temperature fuel cell (10) the process waste air from which can be fed to the drying cubicle (1) as hot air;

   d) there is provided a control system which

   da) so operates the high temperature fuel cell (10) regardless of the electrical energy generated thereby that the thermal energy generated thereby meets the requirement in the drying cubicle (1);

   db) supplies whatever quantity of electrical energy is generated by the high temperature fuel cell (10) to other electrical consumers.
2. System according to claim 1, characterised in that the control system utilises the electrical energy of the high temperature fuel cell (10) primarily for electrical consumers (6, 12, 15) belonging to the system itself and secondarily for electrical consumers located outside the system.
3. System according to claim 2, characterised in that the control system utilises the electrical energy of the high temperature fuel cell (10) within the system itself primarily for the electrical consumers (6) used for heat generation, for example, infrared radiators, and secondarily for other electrical consumers, for example, electrical drives.
4. System according to any one of the preceding claims, characterised in that the control system supplies the surplus electrical energy of the high temperature fuel cell (10) not consumed in the system itself primarily to an energy accumulator and secondarily to the general electrical mains supply.
5. System according to any one of the preceding claims, characterised in that there is provided a regenerative post-combustion device (11) to which air extracted from the drying chamber (1) and containing hydrocarbon is fed for purification.
6. Method according to claim 5, characterised in that a heat exchanger (14) is provided in which a thermal exchange takes place between hot air drawn from the regenerative post-combustion device (11) and air drawn from the ambient atmosphere and fed to the drying cubicle (1).
7. Method for drying objects, wherein air is heated and the objects are subjected to the influence of the heated air,
   characterised in that:

   a) the process waste air from a high temperature fuel cell (10) is used as hot air;

   b) the high temperature fuel cell (10) is operated according to the requirement for thermal energy of the drying process regardless of the electrical energy generated thereby.

   c) the electrical energy generated by the high temperature fuel cell (10) is fed in whatever quantity is obtained to electrical consumers.
8. Method according to claim 7, characterised in that the electrical energy of the high temperature fuel cell (10) is utilised primary for electrical consumers (6, 12, 15) belonging to the system itself and secondarily for electrical consumers located outside the system.
9. Method according to claim 7 or 8, characterised in that the electrical energy of the high temperature fuel cell (10) 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 any one of claims 7 to 9, characterised in that the surplus electrical energy of the high temperature fuel cell (10) 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 any one of claims 7 to 10, characterised in that the air produced during drying and containing hydrocarbon is post-combusted regeneratively.
12. Method according to claim 11, characterised in that 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 any one of claims 7 to 12, characterised in that upon attainment of the operating temperature of the fuel cell (10) the fuel gas is heated at least partially by electrical energy supplied from the fuel cell (10) itself.
14. Method according to any one of claims 7 to 13, characterised in that the process waste air from the high temperature fuel cell (10) forms an inert atmosphere in the drying cubicle (1).

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