Drying system having a thermal engine

A system for drying vehicle bodies and/or for controlling the temperature thereof. The system includes a cabin and has a heater for heating hot air for the cabin. The system is equipped with a mechanical energy-consuming device, for example, a generator and/or a fan. The heater contains at least one heat exchanger. The hot exhaust gas of a thermal engine can be supplied to the heat exchanger. The thermal engine is coupled to the mechanical energy-consuming device, for example, the generator, so as to move together. Because of the coupled movement, mechanical energy can be transmitted from the thermal engine to the mechanical energy-consuming device.

FIELD OF THE INVENTION

The invention relates to a system for the heating-up of, in particular metallic, workpieces, specifically of vehicle bodies, comprising a cabin, a heating system for heating intake air for the cabin, as well as a consumer of mechanical energy.

BACKGROUND OF THE INVENTION

Such a system is known from EP 1 302 737 B1, which describes a painting or coating plant for vehicle bodies, which include a drying module with a heating-up cabin for drying freshly painted or coated vehicle bodies. To this end, hot air can be circulated in the drying module with the aid of a fan. The circulated hot air is heated in a heat exchanger.

To ensure reliable operation of industrial plants and assembly lines, in particular in the production of automobiles, it is necessary to continuously supply electrical energy to the control and drive systems provided therein. This is not a given in, among others, the so-called developing countries and emerging market countries. There, a failure occasionally occurs in the utilities or power grids for electrical energy. Therefore, the utilities of production facilities are provided with emergency backup generators or systems for storing electrical energy to maintain production even in the case of a breakdown of the power supply voltage.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a system for heating-up components, which can be operated reliably and economically even during a temporary disconnection of the system from a public power grid and/or for which the total system efficiency can be increased or optimized.

This object is achieved with a system as described above in which the heating system comprises at least one heat exchanger charged with hot exhaust gas from a thermal engine, in particular a gas motor or a gas turbine, to remove heat from the hot exhaust gas for the heating to a drying temperature of intake air for the cabin, wherein the thermal engine is movably coupled to the consumer to transfer mechanical energy from the thermal engine to the consumer.

The term “gas” referred to herein is especially a mixture of air and harmful or toxic substances.

The invention is based on the insight that the enthalpy of the exhaust gas of a thermal engine, in particular an internal combustion engine for the exothermal combustion of a gas/air mixture, which is designed to run an electrical generator with several megawatts of power, exhibits a substantial amount of heat in the exhaust gas. According to the invention, the thermal output of the above-mentioned thermal engine during rated operation is preferably set to a value of 1 MW to 8 MW, whereas the installed electrical power of the electrical generator (or of another consumer) is set to about 2 MW to 10 MW. The mentioned thermal output in accordance with the invention is preferably used to heat up 1,500 kg of steel from ambient temperature to a handling or processing temperature between 130° C. and 200° C. The mentioned amount of steel corresponds, for example, to a number of about 30 vehicle bodies made from sheet steel with a weight of about 500 kg each. With a cycle time of about 30 units per hour, the vehicle bodies can be heated up to a (drying) temperature in the range between 130° C. and 200° C. in a cabin using the extractable heat energy of the exhaust gas.

To dry the mentioned vehicle bodies, a total heat power in accordance with the invention is preferably provided in a range between 3.6 MW and 6 MW and is transferred onto the bodies with an overall efficiency of about 0.05 to 0.1.

Against this background, it is a basic principle of the invention to use a thermal engine, in particular a thermal engine in the form of a gas motor or a gas turbine, as a heating system for hot air in a plant for the drying and/or for the maintaining of the temperature of metallic workpieces, in particular bodies. According to the invention, the gas motor is operated with a homogeneously gaseous combustion gas/air mixture, whereby the combustion gas preferably is under standardized conditions gaseous hydrocarbons (e.g. methane, butane, natural gas etc.), which is mixed with fresh air in an optimum ratio. Alternatively, hydrocarbon-containing exhaust gases from corresponding sources of a production facility are drawn off and enriched with fresh air and/or with a combustion gas to achieve a desired mixing composition. Further, a gas motor in accordance with the invention is, in particular, of the four-stroke engine type or of the two-stroke engine type, and which can be operated as a combustion motor according to the Otto principle, the diesel principle or the Seiliger principle. A gas turbine according to the invention can be operated in analogous manner.

The electrical power provided by the electrical generator can then be used to reliably power electrical consumers in a drying plant designed for about 30 body units, such as drive mechanisms for conveying units and fans, but also electrical control devices.

The invention further encompasses that correspondingly less electrical power has to be provided for the consumers when bodies are moved through the plant with a slow cycle time. The drying system according to the invention, therefore, provides for the drying of vehicle bodies with a tremendously high efficiency. Moreover, the generator of the system may be used to provide electrical energy to other electrical loads of a production facility, such as control devices and drive mechanisms of a painting or coating plant.

A particularly efficient heat transfer of the heat from the exhaust gas of the gas turbine to the hot air of the cabin is possible when the heat exchanger is coupled to at least one heat transfer fluid loop, which comprises at least one further heat exchanger to heat up the intake air for the drying cabin.

Preferably, the heat transfer fluid loop comprises a heater device and/or a heat reservoir for heating the heat transfer fluid during the start-up phase of the gas turbine. Thereby, a fast start-up of the system is made possible. In accordance with the invention, the heat transfer fluid loop in particular utilizes water, a salt solution, or a heat-transfer oil for circulation, wherein the heat transfer medium can act at least temporarily as an efficient heat storage medium. Preferred are aqueous solutions of potassium carbonate or calcium chloride or diesel oil, rape oil, or silicon oils (e.g. polymeric phenylsiloxanes).

Moreover, it is advantageous if the heat exchanger is connected to a further heat transfer fluid loop to provide heat to at least one heat sink operating in a low-temperature range. This further heat transfer fluid loop is also preferably a water loop, a brine loop, or a heat transfer oil loop. In an optimized embodiment, the (first) heat transfer fluid loop and the second heat transfer fluid loop comprise different heat transfer fluids, which are adapted to the respective conditions. As a result, particularly efficient operation of the plant is made possible. It is further advantageous for the energy balance of the plant when the latter comprises a heat transfer fluid loop with a heat exchanger for heating up the fresh air provided to the drying cabin.

In a plant in accordance with the invention, heat can be extracted, in particular, directly from the hot exhaust gas of the thermal engine in a heat exchanger, which heats up the intake air for the cabin, which is in the form of a drying cabin for example, and delivers it to the cabin without further treatment. In this case, it is advantageous to provide several heat exchangers, which are supplied with the hot exhaust gas in the form of a cascade and transfer the heat to the intake air for the cabin. The exhaust gas of the thermal engine flowing through the heat exchanger can further be provided to one or more further heat exchangers for the heating-up of fresh air to the cabin. Moreover, the heat from the exhaust gas of the gas turbine can be used to provide heat to a heat sink operating in a low-temperature range. To this end, exhaust gas from the gas turbine is directed to one or more further heat exchangers for the transfer of heat from the exhaust gas to a heat transfer fluid loop, for example, a heat transfer fluid loop with water as the heat transfer fluid. To ensure a sufficient exhaust gas flow, it is advantageous if the exhaust gas from the thermal engine is supplied to this at least one further heat exchanger via a fan.

An environmentally friendly and a simultaneously energy-efficient operation of the plant can be achieved by connecting the cabin with a purification reactor for the thermal regenerative oxidation of solvent-containing exhaust gas. The purification reactor receives the exhaust gas via an exhaust gas line from the cabin. At the same time, the purification reactor is connected to a heat exchanger for the transfer of heat onto a heat transfer fluid loop, which is preferably a hot water loop. With this heat transfer fluid loop, one or more heat sinks working in a low-temperature range can be provided with heat, for example one or more heat exchangers for heating up fresh air supplied to the cabin.

In a particularly preferred embodiment of the plant, a heat reservoir for storing the heat from the exhaust gas of the thermal engine is provided. Preferably, this heat reservoir is provided in a bypass conduit, which bypasses a conduit segment for the provision of exhaust gas to one heat exchanger of the plant. Moreover, it is advantageous to provide the generator of the plant with a buffer (an accumulator amongst other things), for the buffering of electrical energy. This allows providing power to the control devices and drives of the plant without simultaneously heating hot air for the drying cabin.

By feeding the thermal engine with solvent-containing, hydrocarbon-enriched exhaust gas from the cabin as combustion gas, this exhaust gas can be disposed of by incineration and simultaneously used for energy production. In principle, the thermal engine can be operated with exhaust gas from a spray booth of a painting plant. Notably, the system for heating-up can also comprise several decentrally arranged thermal engines, which can power one or more consumers of mechanical energy, such as fans, generator or even compressors. The plant in accordance with the invention is particularly suited for a painting plant for motor vehicles or motor vehicle components.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The system1shown inFIG. 1for drying workpieces is designed in particular for vehicle bodies3(or parts thereof) and comprises a cabin that is formed as a drying tunnel5or as a drying cabin. The drying tunnel5has a substantial heat demand, such that sensible heat has to be transferred to the drying tunnel from the outside at a given, with respect to the ambient conditions significantly increased, temperature level. The invention is therefore described using a plant for drying vehicle bodies as an example. In modified exemplary embodiments, a system in accordance with the invention is provided as a plant for tempering, drying, hardening and/or irradiating, but in particular for the heating-up of large metallic workpieces. Other suitable workpieces, besides vehicle bodies (or parts thereof), are large-volume systems with comparably large heat capacities, which undergo a treatment having an increased heat demand. In accordance with the teachings of the invention, the so-called dryer, the so-called drying cabin or the drying tunnel can be used for any tasks with a heat demand without deviating from the teachings in accordance with the invention.

Vehicle bodies3, which are mounted onto skids7, are transported through drying tunnel5with the aid of conveying device9. During that process, mechanical energy is consumed. Conveying device9has an electrical drive train10. The drive train10is an electrical energy consumer within the system1. The drying tunnel5has an intake lock11and an exit lock13. The drying tunnel includes a drying section15, which is located between intake lock11and exit lock13. The drying section15is preferably arranged in such a way that about15freshly painted and/or solvent-containing substrate-coated vehicle bodies3can be dried more or less simultaneously. To this end, the drying section15is dimensioned, for example, with a length L=40 m, an internal width b of 1.40 m<b<1.60 m and a headroom h of 2.60 m<h<2.00 m. In a particularly preferred embodiment, a cycle time distance of 5.2 m, thirty units per hour, and a 0.5 hour residence time result in a tunnel length of 78 m (outer width b: 3 m to 4.6 m, outside height h: 2.8 m to 3.3 m).

To dry a vehicle body that is freshly coated with paint and/or a substrate, drying must take place, depending on the kind of the paint or substrate, for about 30 minutes at a temperature T, which is in the range between 130° C.<T<200° C., usually between 140° C.<T<175° C. The drying temperature for cathodic electrodeposition painting is, for example, 180° C., for filler painting 160° C., and for a thick resist 140° C. The required heat amount for drying a vehicle body is determined by the heat amount that has to be transferred to a steel sheet of a vehicle body during a heating-up period of 15 minutes, to bring the steel sheet to the drying temperature. Because the weight of the steel sheet utilized for a vehicle body is usually of the order of 500 kg, the heat amount required for drying paint or a substrate on a freshly coated vehicle body is about 36 MJ. For the drying and/or cross-linking of common paints, a retaining period of 15 minutes at the drying temperature T is preferably provided following the heating-up time.

In the intake lock11and the exit lock13, the vehicle bodies3are transported through a gas atmosphere containing heated fresh air. By contrast, the vehicle bodies3in the drying section15of the drying tunnel5reside in a hot-air atmosphere with recirculated hot air. The temperature of the hot air corresponds in this case to the required drying temperature of a paint and/or a substrate on a vehicle body3. To ensure a uniform drying temperature for the paint or the substrate on the surface of a vehicle body3, the hot-air atmosphere is circulated within drying tunnel5with a defined flow. To this end, the drying tunnel5is provided with intake and exhaust ports (16,17), which are connected with a heat exchanger19, for inlet air in the form of hot air. The intake ports16in the drying tunnel are preferably provided with jets in a heating-up region. Further preferred is the provision of intake ports without jets in the contiguous retaining zone.

The heat exchanger19is provided with a fan21, which draws in cooled-down hot air through the heat exchanger21via one or more exit ports17and recirculates hot air into the drying tunnel5via one or more jets16in the drying tunnel5. The heat exchanger19is connected to the exhaust gas line23of a thermal engine25. Thermal engine25is a gas turbine, for example the gas turbine model SGT-400 from Siemens or the gas turbine model LM 1600 from General Electric. Instead of a gas turbine, however, it is also possible to employ gas motors or also another internal combustion engine in system1. By way of example, the gas motors of model J616 GS of type series6from Jenbacher Gasmotoren are also suitable for use in the system1.

The thermal engine25burns a combustion gas provided via pipe47. The exhaust gas of the thermal engine25generated thereby flows into exhaust gas pipe23with a temperature TEG, which lies between 300° C. and 600° C., and a mass throughput IMEGof 17 kg/s<IMEG<21 kg/s. To achieve a good flow performance for the exhaust gas, the exhaust gas pipe23is preferably provided as a hot tube with a pipe diameter of nominal width DN800.

In the heat exchanger19, heat from the exhaust gas of thermal engine25is transferred to the hot air circulated by fan21through the heat exchanger19into the drying tunnel5. From the heat exchanger19, exhaust gas from the thermal engine25is provided to a further heat exchanger27, which corresponds to heat exchanger19. In heat exchanger27, fan29is likewise used to heat circulated hot air from the drying section of the drying tunnel5to a drying temperature.

It is, of course, possible for the heating up of hot air circulated within the drying tunnel5to also provide a multitude of heat exchangers through which exhaust gas from the thermal engine is run.

From the heat exchanger27, the exhaust gas from the gas turbine25flows to a heat exchanger31for fresh air. Through this heat exchanger31, fresh air is sucked in with a fan33. This heated fresh air is provided to intake lock11and exit lock13of the drying tunnel. At the exit side of the heat exchanger31for fresh air is a further fan35. With this fan, already cooled-down exhaust gas from the thermal engine25is blown under pressure into a hot gas pipe37in a heat exchanger formed as a heat recovery boiler39. In this heat recovery boiler39, residual heat of the exhaust gas is transferred to a hot water loop41. Hot water loop41serves the purpose of providing heat to further heat sinks, such as a so-called preparation station of a painting plant, a heating system for a factory hall with work stations, or a heating system for intake and exhaust air.

To ensure an advantageous flow of the exhaust gas from the thermal engine25through heat recovery boiler39, a stack43is provided thereon. Through this stack43, cooled-down exhaust gas from the thermal engine25is released into the environment.

The drying tunnel5is connected via exhaust pipe52to purification reactor54for the thermal regenerative oxidation of solvent-comprising dryer exhaust gas from the drying tunnel5. In this purification process, dryer exhaust gas provided to the purification reactor54is heated. The purification reactor54is connected via gas line56to a heat exchanger formed as a heat recovery boiler58. In the heat recovery boiler, the heat from the discharge air purified in purification reactor54is transferred to a hot water loop60. This hot water loop60serves the purpose of providing heat to further heat sinks, which operate at low temperature. Purified exhaust air from the purification reactor54flowing through heat recovery boiler58is released into the environment through stack62. This measure ensures a good flow performance for the exhaust gas in the heat recovery boiler58.

To make possible a fast start-up of drying system1, a heating device64, that is preferably fired using fossil fuel, is provided in the exhaust gas line23between the thermal engine25and the heat exchanger19.

The thermal engine25is supplied with fresh air via connection50. It operates in good approximation according to the thermodynamic Joule-Thompson Process. The mechanical power of the thermal engine25is dimensioned such that with the enthalpy of the exhaust gas preferably up to30or even more vehicle bodies per hour can be dried at a drying temperature between 130° C. and 200° C. in the drying tunnel5. Such a thermal engine can provide a mechanical power of about 12 MW.

The thermal engine25is provided with a generator45. To this end, the thermal engine25is movably coupled to the generator45. Torque provided at a power train of the thermal engine is transferred onto the generator45using pivotable shaft46. During operation of the thermal engine25, the generator45produces electrical energy. The mechanical energy led into the generator25using the pivotable shaft46is consumed by the generator45. Like the conveyor9, the generator45is a consumer of mechanical energy in the system1. The generator45is connected to a distributor module49. Via the distributor module49, the generator45provides electrical energy to the electrical consumers of system1, such as the electrical drive train10of conveyor9and the fans (21,29,33,35), and corresponding control units.

FIG. 2depicts a system101for the drying of vehicle bodies103with a drying tunnel105, which is constructed like the dryer tunnel5of system1inFIG. 1. Also, the construction of conveyor109for the transport of the vehicle bodies103on the skids107corresponds to the one in system1. Thus, the conveyor109has electrical drive trian110. For the heating-up of hot air circulated in the drying section115of the drying tunnel105, the system101comprises a heat exchanger119and a heat exchanger127. The heat exchangers (119,127) are provided with corresponding fans (121,129) to circulate hot air through intake and exit ports (116,117) within drying tunnel105.

Contrary to the heat exchangers (19,27) of system1inFIG. 1, heat exchangers (119,127) are not directly connected to exhaust line123of thermal engine125, but are arranged in loop140with a thermal fluid in the form of hot water or a heat transfer oil. Compared to system1inFIG. 1, this measure allows installing less hot pipe with a large pipe diameter to heat hot air for the drying tunnel105with heat from the exhaust gas of the thermal engine125which is supplied with combustion gas via pipe147and with fresh air via connection150. To this end, the heat transfer fluid within the loop140transports the heat that was extracted from the exhaust gas of the thermal engine125, to the heat exchangers (119,127), where it is transferred to the hot air circulating within dryer105.

To extract heat from the exhaust gas of thermal engine125, an exhaust gas line123is connected to a heat exchanger, which is provided as heat recovery boiler139. The heat recovery boiler139is provided with a stack143. In heat recovery boiler139, heat from the exhaust gas of thermal engine125is transferred into loop140for hot water.

To make possible a fast start-up of system101, a heating device164, that is preferably fired using fossil fuel, is provided in a section142of the loop140. A heat reservoir165is provided in the connector section146of loop144. During operation of thermal engine125, heat is stored in the heat reservoir165. With this stored heat, fresh air flowing through the heat exchanger131can be heated up when the thermal engine125is operated only at low power or is at a standstill.

The loop140comprises a power branch144through which the heat of the exhaust gas of the thermal engine125can be transported to a heat exchanger131. This heat exchanger131, like the heat exchanger31in the system1, serves the purpose of heating up fresh air that is provided via fan133to the intake lock111and the exit lock113of the drying tunnel105.

The heat recovery boiler139is further connected to the loop141for hot water, which, like the loop41in the system1, serves the purpose of providing heat that was extracted from the exhaust gas of gas turbine25to further heat sinks in a low-temperature range.

Additionally, the drying tunnel105in the system101is provided with a purification reactor154for the purification of exhaust gas supplied via exhaust pipe152, which, like the purification reactor54of system1inFIG. 1, is provided with a heat recovery boiler158with a hot water loop160and a stack162. The purification reactor154is connected to the heat recovery boiler158by gas line156.

The thermal engine125of system101actuates an electrical generator145. Using distributor module149, generator145provides, as in system1inFIG. 1, electrical energy for the electrical consumers in system101.FIG. 3depicts a thermal engine225in a system301for the drying of vehicle bodies. The thermal engine225can be, in particular, provided as a gas turbine or gas motor or else as a Diesel engine. The thermal engine225is also movably coupled by a shaft226to a generator245. The thermal engine225in the system301is provided with reservoir320formed as a buffer reservoir for electrical energy and a reservoir310for heat. The reservoir310for heat is provided in a bypass conduit312that is lockable by means of controllable valves (314,316). The bypass conduit312is provided in a section of the exhaust gas conduit223of the thermal engine225in which a controllable locking valve318is arranged. The reservoir320for electrical energy is inserted into an electrical bypass conduit322. The reservoir320for electrical energy allows for storing of energy generated from an electrical current I of the generator245if it surpasses the demand of the consumers in the system provided via the distributor module249. Accordingly, the actuation of valves (314,316,318) allows for storing, with the reservoir310, of heat from the exhaust gas of the gas turbine225, when the amount of heat per time period contained in the exhaust gas exceeds the heat range for the operation of the drying cabin. As for the rest, the construction of the system301corresponds to the construction of the system1or101inFIG. 1orFIG. 2, respectively.

The combination of a reservoir310for heat and a reservoir320for electrical energy with the gas turbine225depicted inFIG. 3enables providing a system for the drying of vehicles, as are depicted inFIG. 1orFIG. 2, with heat and electrical energy, even if the thermal engine provided therein is not in operation.

The painting plant400depicted inFIG. 4comprises a system401for drying vehicle bodies403mounted on skids407which are transported through the drying tunnel405via conveying device409. The conveying device409has a drive train410. Included in system401for the drying of vehicle bodies is a thermal engine425, which can be operated with the exhaust gas of a drying tunnel405as a combustion gas. As far as the construction of the system401corresponds to the construction of the system1depicted inFIG. 1, those elements inFIG. 4that correspond to the elements depicted inFIG. 1are characterized by reference numerals that are increased by the number400relative toFIG. 1. Thus, the drying tunnel405has an intake lock411and an exit lock413as well as a drying section415. The drying tunnel405has intake and exhaust ports (416,417) which are connected to heat exchanger419. The heat exchanger419is connected to the exhaust gas line423of a thermal engine425. The thermal engine425burns a combustion gas provided via pipe447. The thermal engine425is provided with a generator445. To this end, the thermal engine425is movably coupled to the generator445. The generator445is connected to a distributor module449. From the heat exchanger419, exhaust gas from the thermal engine425is provided to a further heat exchanger427. From the heat exchanger427, the exhaust gas from the gas turbine425flows to heat exchanger431for fresh air. Fresh air is drawn in via fan433through the heat exchanger431. A further fan435is provided at the exit side of the heat exchanger431for fresh air. With this fan435, already cooled-down exhaust gas from the thermal engine425is blown under pressure into a hot gas pipe437in a heat exchanger formed as a heat recovery boiler439. In this heat recovery boiler439, residual heat of the exhaust gas is transferred to a hot water loop441. To ensure an advantageous flow of the exhaust gas from the thermal engine425through heat recovery boiler439, a stack443is provided thereon. Through this stack443, cooled-down exhaust gas from the thermal engine425is released into the environment. The thermal engine425is supplied with fresh air via connection450and a heating device464is provided in the exhaust line423between the thermal engine425and the heat exchanger419.

System401includes an exhaust duct471through which hydrocarbon-enriched exhaust gas from the drying tunnel405can be supplied to the thermal engine425as combustion gas. In exhaust duct471, a gas reservoir473is preferably provided. The exhaust gas from the drying tunnel405can be injected into gas reservoir473with a compressor475. Within the system401, a mixing chamber477is provided, in which switching of controllable valves (479,481) of the thermal engine425has the effect that fossil combustion gas from a supply source482can be mixed with exhaust gas from the drying tunnel405.

The painting plant400comprises a spray booth483. The spray booth483is a painting station. In the spray booth483, vehicle bodies485can be exposed to a spray paint by a painting robot487. The spray booth483has an extraction system489for gas comprising a fan491. Gas that has been sucked out of spray booth483can be conducted via a conduit system493with valves (495,497) into mixing chamber477. A gas reservoir496is connected between valves495and497.

Thus, the mixing chamber477is operatively connected to the supply source482for combustion gas, the spray booth483and the drying tunnel405for receiving and mixing the combustion gas from the supply source482, the exhaust gas from the spray booth483and/or the exhaust gas from the drying tunnel or cabin405. This arrangement enables running of the thermal engine425alternatively with exhaust gas from the drying tunnel405, hydrocarbon-containing exhaust gas from the spray booth483, or with combustion gas which is provided externally of system401, or with a gas mixture.

The temperature of the exhaust gas flow from the drying cabin is higher than the temperature of the exhaust gas flow from the spray booth. The temperature of the exhaust gas flow from the drying cabin can lie between 60° C. and 250° C. The temperature of the exhaust gas flow from the spray booth can lie between 20° C. and 40° C.

The flow rate of the exhaust gas flow from the drying cabin is lower than the flow rate of the exhaust gas flow from the spray booth. The flow rate of the exhaust gas flow from the drying cabin can lie between 2.000 m3N/h and 20.000 m3N/h. The flow rate of the exhaust gas flow from the spray booth can lie between 50.000 m3N/h and 2.000.000 m3N/h. The unit m3N/h is the standard cubic meter per hour, that is, a volume flow in cubic meters per hour at standard conditions.

Due to thermodynamic efficiency, thermal engines should preferably be supplied with cold combustion gas. Supplying the thermal engine with the hot exhaust gas flow from the drying cabin is therefore not efficient. By mixing the high temperature and low flow rate exhaust gas flow from the drying cabin with the low temperature and high flow rate exhaust gas flow from the spray booth, the temperature of the resulting gas flow allows a much more efficient operation of the thermal engine.

Accordingly, the thermal engine425can be provided with hydrocarbon-containing exhaust gas from the spray booth. In the thermal engine425, these exhaust gases can be incinerated.

The system501for drying vehicle bodies503depicted inFIG. 5comprises several thermal engines in the form of gas motors (571,573,575). The gas motors (571,573,575) can be, for example, the gas motor type E 2842 LE 322 or the gas motor type E 2876 TE 302 from MAN. As far as the construction of the system501corresponds to the construction of the system1depicted inFIG. 1, those elements inFIG. 5that correspond to the elements depicted inFIG. 1are characterized by reference numerals that are increased by the number500relative toFIG. 1.

Thus, vehicle bodies503, which are mounted onto skids507, are transported through drying tunnel505with the aid of conveying device509. During that process, mechanical energy is consumed. Conveying device509has an electrical drive train510. The drive train510is an electrical energy consumer within the system501. The drying tunnel505has an intake lock511and an exit lock513. The drying tunnel includes a drying section515, which is located between intake lock511and exit lock513. The drying section515is preferably arranged in such a way that about515freshly painted and/or solvent-containing substrate-coated vehicle bodies503can be dried more or less simultaneously.

To ensure a uniform drying temperature for the paint or the substrate on the surface of a vehicle body503, the hot-air atmosphere is circulated within drying tunnel505with a defined flow. To this end, the drying tunnel505is provided with intake and exhaust ports (516,517).

The drying tunnel505is connected via exhaust pipe552to purification reactor554for the thermal regenerative oxidation of solvent-comprising dryer exhaust gas from the drying tunnel505. In this purification process, dryer exhaust gas provided to the purification reactor554is heated. The purification reactor554is connected via gas line556to a heat exchanger formed as a heat recovery boiler558. In the heat recovery boiler, the heat from the discharge air purified in purification reactor554is transferred to a hot water loop560. This hot water loop560serves the purpose of providing heat to further heat sinks, which operate at low temperature. Purified exhaust air from the purification reactor554flowing through heat recovery boiler558is released into the environment through stack562. This measure ensures a good flow performance for the exhaust gas in the heat recovery boiler558.

The thermal engines (571,573) are provided in separate hot-box modules (572,574). The thermal engines (571,573), arranged within the corresponding hot-box modules (572,574), are mechanically coupled by drive shafts (577,579) to a generator (581,583) and to a fan (587,589), respectively. The fans (587,589) serve to circulate air in the drying tunnel505. The fans (587,589) transport air from the drying tunnel505in the hot-box modules (572,574) through a heat exchanger (591,593), which is arranged in the proximity of thermal engine (571,573). Each hot-box module (572,574) includes two control valves (595,597). By switching the control valves (595,597) in the hot-box modules (572,574), exhaust gas from the thermal engines can alternatively be guided via conduit section599through the heat exchangers (591,593) to heat-up circulating air from the dryer tunnel505or via conduit section601directly into the dryer tunnel505.

The thermal engine575is arranged in a module603for the heating-up of fresh air, which can be brought into the drying tunnel505via a conduit system605. Within the module603, a generator585and a fan592are provided. The fan592and the generator585are movably coupled to the thermal engine with drive shafts (594,596). With the fan592, fresh air can be drawn in and guided into the drying tunnel505. For the heating-up of the drawn-in fresh air, the fan592is connected to a heat exchanger607. The heat exchanger607, in turn, is connected via conduit section609to the thermal engine575. The exhaust gas from the thermal engine575can therefore be guided via conduit section609through the heat exchanger607into the environment. Thereby, heat from the exhaust gas of the thermal engine575can be transferred to the fresh air provided to the drying tunnel505.

The thermal engines (571,573,575) of the system501have respective cooling cycles which are not depicted inFIG. 5. These cooling cycles serve for the cooling of the combustion chambers in the thermal engines (571,573,575). With the heat from the thermal engines (571,573,575) released from the cooling cycle, heat consumers in a low-temperature range, which are not shown inFIG. 5, can be provided with heat.

The generators (581,583,585) arranged in the hot-box modules (572,574) and the module603for the heating-up of fresh air produce electrical energy that is conducted via electrical connections611to the distribution module549of the system501.

In summary, the following preferred features are particularly to be noted: a system1for the heating-up and/or drying of vehicle bodies3comprises a cabin5. It includes a heating system (19,27) for the heating-up of intake air for the cabin5. Within the system1, there is a consumer of mechanical energy, for example a generator45or a fan (21,29). The heating system comprises at least one heat exchanger (19,27). The heat exchanger (19,27) can be charged with the hot exhaust gas of a thermal engine25. The thermal engine25is movably coupled to the consumer of mechanical energy45. Due to this movable coupling, mechanical energy can be transferred from the thermal engine25to the consumer45.