Recirculation system, treatment plant and method for operating a recirculation system

Abstract

The present invention relates to a recirculation system (104), in particular for a treatment plant (100) for treating workpieces, wherein the recirculation system (104) comprises the following: - a plurality of local recirculation modules (112), by means of which local recirculation flows (114) can be supplied to a treatment chamber (106), guided therethrough and discharged out thereof, wherein the local recirculation flows (114) each flow through the treatment chamber (106) multiple times; and - a global recirculation guide (120), by means of which a global recirculation flow (122) can be discharged from the plurality of local recirculation modules (112) and / or the treatment chamber (106), can be prepared by means of a preparation device (126) and can be supplied again to at least one of the plurality of local recirculation modules (112) and / or the treatment chamber (106).

Description

[0001] Recirculation system, treatment system and method for operating a recirculation system

[0002] The present invention relates to a recirculation system and a treatment system with a recirculation system according to the invention. Furthermore, the invention relates to a method for operating a recirculation system.

[0003] It is known from practice that the technical ventilation of treatment systems such as drying systems in the body shop, or dryers for short, requires a constant exchange of the dryer atmosphere containing solvents (exhaust air) with a solvent-free fresh air stream. For this purpose, an exhaust air volume flow is extracted from one or more points in the treatment room or drying tunnel using an exhaust air fan and fed to an exhaust air purification device, usually a technical exhaust gas purification system (TAR). The purified volume flow is available - if a TAR is used - at a temperature of approximately 450 °C for heating the dryer. The individual treatment room sections or drying sections are heated via clean gas heat exchangers, while the clean gas flow cools down along the clean gas chain.Finally, the clean gas stream passes through a fresh air heat exchanger and then exits the treatment plant at a temperature of, for example, 130 °C via the corresponding roof of the plant. The minimum exhaust air flow rate is determined according to the standard based on the lower explosion limit, but in practice is correspondingly higher, so that the energy demand of the drying plant can be covered by the clean gas enthalpy.

[0004] As an alternative to TAR-cleaned dryer systems, regenerative thermal oxidizers (RTOs) can also be used. In such systems, the outlet temperature of the clean gas from the RTO is approximately 20 K to 40 K above the inlet temperature and thus significantly lower than in a TAR. The clean gas stream is therefore not suitable for heating the individual treatment room sections or dryer zones, but is generally used only for preheating fresh air. This again results in a clean gas volume flow of typically over 100 °C, which is discharged via the roof of the system. The individual dryer sections are supplied with individual burners or electric heaters. In both cases, there is no material recirculation of the cleaned exhaust air into the drying process.

[0005] The high enthalpy flow of the clean gas can only be partially recovered by the heat exchangers downstream in the clean gas chain. A very large portion of the energy used leaves the plant unused with the clean gas flow through the roof.

[0006] Since then, the direct recycling of combustion products into the drying process has been abandoned, as combustion with natural gas can produce various combustion products (NOx, sulfur compounds, etc.) that can be process-critical.

[0007] The present invention is based on the object of providing a recirculation system which enables efficient operation with reduced exhaust air.

[0008] This object is achieved according to the invention by a recirculation system having the features according to claim 1.

[0009] The recirculation system is in particular a recirculation system for a treatment system for treating workpieces, in particular for drying vehicle bodies.

[0010] The air recirculation system comprises the following: a plurality of local air recirculation modules, by means of which local air recirculation flows can be supplied to a treatment room, passed through the treatment room, and discharged from the treatment room, wherein the local air recirculation flows each flow through the treatment room multiple times; and a global air recirculation system, by means of which a global air recirculation flow can be discharged from the plurality of local air recirculation modules and / or the treatment room, treated by means of a treatment device, and again supplied to at least one of the plurality of local air recirculation modules and / or the treatment room.

[0011] The invention is based on the idea that, to reduce the energy loss of the exhaust air flow or clean gas flow discharged via the roof, the exhaust air volume flow extracted from the treatment room or drying tunnel is fed into a special cleaning device and then at least partially recirculated into the process as cleaned recirculated air. The exhaust air cleaning device can be an electrically operated, flameless RTO.

[0012] A particular advantage is that this purely electrical heating of the gas flow prevents the introduction of foreign substances from the gas circuit, as is the case with cleaning with a TAR or a conventional RTO. Furthermore, there is no risk of unburned gas flooding the treatment plant or dryer and creating an explosion hazard.

[0013] Significant energy savings are achieved by reducing clean gas enthalpy loss through the roof. Furthermore, the cross-section of the clean gas or exhaust air duct can be reduced, or clean gas or exhaust air ducts through the roof can be completely eliminated, for example, by fully recirculating the global recirculating air.

[0014] By recirculating the global recirculated air, a fresh air heat exchanger can be made smaller, which also reduces the corresponding investment costs.

[0015] It should be understood that the treatment room may include a pre-treatment room and / or a post-treatment room.

[0016] Furthermore, with the recirculation system according to the invention, it is possible to operate the system in stand-by mode in which the clean gas enthalpy loss via the roof is almost zero.

[0017] Preferably, hot water can also be saved in the post-treatment room or the cooling zone.

[0018] In one embodiment of the invention, it can be provided that the treatment device is or comprises a treatment device for treating, in particular for cleaning, the global circulating air flow, wherein the treatment device is or comprises a thermal treatment device, in particular a purely electrically operated, preferably flameless, regenerative thermal oxidation device.

[0019] It may be advantageous if the RTO has an electrical heating device for conditioning the global circulating air flow and can also be operated autothermally if the solvent concentration has exceeded a certain limit.

[0020] In the case of an autothermal reaction, for example, at a solvent concentration of 1 g / m 3The temperature gain increases with increasing solvent concentration. RTO can act as a catalyst.

[0021] Advantageously, after treatment, no process-critical reaction products are released back into the global recirculating air stream.

[0022] In one embodiment of the invention, it can be provided that the thermal processing device is or comprises an electrical heating device, wherein it is preferably provided that thermal processing takes place exclusively by direct electrical heating, in particular electrical resistance heating, and / or by exothermic conversion of components of the global circulating air flow.

[0023] The treatment device preferably comprises a fan for conveying the global circulating air flow.

[0024] In one embodiment of the invention, it can be provided that the treatment device is provided and / or designed independently of a discharge device for discharging exhaust air, in particular spatially separated from an exhaust air line which serves to discharge exhaust air from the recirculation system.

[0025] In one embodiment of the invention, it can be provided that different and / or adjacent treatment room sections of the treatment room can be flowed through with local recirculation air flows by means of the local recirculation modules and that global recirculation air can be supplied to or adjacent to one or more local recirculation modules by means of the global recirculation system and / or that recirculation air from one or more other local recirculation modules can be discharged as a global recirculation air flow by means of the global recirculation system.

[0026] Preferably, the global circulating air flow is supplied at the beginning and / or at the end of the treatment room, in particular into an inlet lock and / or outlet lock.

[0027] It is also conceivable that the global recirculation air is fed directly to the local recirculation modules at the beginning.

[0028] The exhaust air from the treatment room sections is preferably discharged to one of the middle treatment room sections.

[0029] Thus, the global recirculated air supplied to the treatment room is fed to the treatment room sections, circulated several times within these sections by means of the local recirculation modules and then discharged for treatment.

[0030] In one embodiment of the invention, it can be provided that the global recirculation air duct opens into one or more locks of the treatment room for the fluid-effective separation of an atmosphere in the treatment room from an environment of the recirculation system.

[0031] It is advantageous that the global recirculating air flow can be supplied, in particular as a lock air flow or as part of the lock air flow, at the beginning and / or end of the treatment room and can consequently be introduced into the treatment room.

[0032] In one embodiment of the invention, it can be provided that the recirculation system comprises one or more additional heating devices provided in addition to the treatment device, by means of which one or more partial flows of the global recirculation air flow can be heated.

[0033] Alternatively or additionally, it may be provided that the entire global circulating air flow is heatable. Furthermore, alternatively or additionally, it may be provided that one or more partial flows of one or more local circulating air flows are heatable.

[0034] In one embodiment of the invention, it can be provided that an air stream passed through the treatment device can be heated by means of the treatment device at least temporarily to a temperature which brings about a chemical conversion of substances contained in the air stream, in particular solvents.

[0035] Preferably, the treatment device is an RTO, which enables cleaning of solvent-containing and / or odorous exhaust air.

[0036] With this technology, higher thermal efficiencies of up to 97% can be achieved through the use of ceramic heat storage media compared to conventional TAR. The basic principle of RTO is based on the use of several combined reactor / heat storage beds. The contaminated air stream, i.e. the global recirculating air stream discharged from the treatment chamber, is first preheated and then heated to the required reaction temperature by a gas burner or an electric heater so that the thermal conversion of the contaminants can take place. Ceramic honeycomb bodies are generally used as reactor / heat storage beds. The waste heat from the reactor is then passed through a second bed with the exhaust air, the treated global recirculating air, where the heat is stored. Once this storage bed has been heated up, the process air flow is switched.The extracted global recirculating air now passes through the heated reactor / heat bed, warming up in the process, and the pollutants are subsequently oxidized in the first bed. Subsequent operation cycles between these states. This allows this process to achieve an autothermal operating state even at very low pollutant concentrations in the exhaust air. This means that the plant heats itself using the exothermic energy released during the oxidation of the pollutants and requires no additional heating from primary energy.

[0037] Alternatively or additionally, it can be provided that an air flow passed through one or more additional heating devices can be heated by means of the one or more additional heating devices, in particular without any significant conversion of substances contained in the air flow.

[0038] In one or more additional heating devices, the global circulating air flow is preferably only heated before being fed back into the treatment room.

[0039] In one embodiment of the invention, it can be provided that the recirculation air system comprises at least one heat exchanger, by means of which thermal energy contained in a derived global recirculation air flow or in an exhaust air flow can be transferred to a fresh air flow supplied to the global recirculation air flow.

[0040] In one embodiment of the invention, it can be provided that a cooled exhaust air stream discharged from the heat exchanger can be fed to a fresh air stream and / or a cooled exhaust air stream which are assigned to a post-treatment chamber.

[0041] In one embodiment of the invention, it can be provided that at least one filter device and / or sorption device, in particular an adsorption and / or absorption device, is arranged downstream and / or upstream of the treatment device for concentrating or deconcentrating at least one element, a compound and / or a mixture of the global circulating air flow.

[0042] In filtration, suspended matter is preferably separated from a liquid or gas stream. In adsorption, however, liquid or gas components are preferably bound to a solid surface, such as the surface of activated carbon or zeolite. Finally, in absorption, a gas or air stream is preferably passed through a scrubbing liquid, thereby binding the gas components to be absorbed.

[0043] The filter device is preferably a hot-zone filter, in particular a filter for sticky substances such as phosphates, a baffle filter, or a filter candle. The efficiency of the filter device can be improved by pre-coating or cyclical filter cleaning. Alternatively or additionally, the filter device can be a chemical filter (chemisorption) or comprise quicklime. The absorption device is preferably a flue gas desulfurization system.

[0044] The object is further achieved by a treatment plant with a recirculation system according to the invention.

[0045] Preferably, the treatment plant can be supplied with a medium voltage of at least approximately 3 kV and / or at most approximately 8 kV, in particular 4,160 V to 6,600 V.

[0046] Preferably, all electrically operated heating components of the recirculation system or the treatment system, such as the preferably electrically operated additional heating devices and the processing device, can be supplied with a medium voltage of, for example, at least approximately 3 kV and / or at most approximately 8 kV, in particular 4,160 V to 6,600 V, instead of the usual 400 V. Although this may require special heating elements with corresponding additional costs, it offers great savings potential, preferably in the periphery, i.e. with regard to connections, cables, etc. In addition, a significantly lower voltage transformation factor from the supply network is necessary, which, among other things, reduces the size of the transformer station in favor of lower investment costs and saves space. Connecting an electrically operated heating component with this type of medium voltage also results in significantly smaller cable diameters.

[0047] The present invention is further based on the object of providing a method which enables an exhaust air-reduced operation of a recirculation system.

[0048] This object is achieved according to the invention by a method according to the independent method claim.

[0049] Preferably, in the method for operating a recirculation system, several local recirculation air flows are supplied to a room to be ventilated, in particular a treatment room, by means of several local recirculation modules, guided through the room, and discharged from the room, wherein the local recirculation air flows each flow through the treatment room multiple times. Furthermore, a global recirculation air flow is preferably discharged from the several local recirculation modules and / or the treatment room by means of a global recirculation system, conditioned, and fed again to at least one of the several local recirculation modules and / or the treatment room.

[0050] The method preferably has one or more of the features and / or advantages described in connection with the recirculation system.

[0051] Preferably, the recirculation system further comprises one or more of the features and / or advantages described in connection with the method.

[0052] In one embodiment of the invention, it can be provided that the global circulating air flow is heated for processing the same, in particular directly and / or exclusively by means of an electrical resistance heater and / or by exothermic conversion of components of the global circulating air flow.

[0053] In one embodiment of the invention, it can be provided that at least approximately 90%, in particular at least approximately 95%, of a total volume flow of the global circulating air flow discharged from the treatment room is processed and fed back into the treatment room.

[0054] In one embodiment of the invention, it can be provided that the processing of the global recirculating air flow takes place independently of the removal of exhaust air, in particular spatially separated from an exhaust air line which serves to remove exhaust air from the recirculating air system.

[0055] In one embodiment of the invention, it can be provided that at least approximately the entire global recirculation air flow discharged by the local recirculation modules is thermally treated during each circulation within the global recirculation system, in particular without the use of additives or other introduction of substances into the global recirculation air flow.

[0056] In one embodiment of the invention, it can be provided that the global circulating air flow is passed at least partially or at least approximately completely through the processing device and is heated at least temporarily to a temperature which brings about a chemical conversion of substances contained in the air flow, in particular solvents, and that at least part of the heat temporarily contained in the global circulating air flow is recuperated, so that the global circulating air flow leaves the processing device at a temperature which lies between an inlet temperature and a temporary maximum temperature.

[0057] In one embodiment of the invention, it can be provided that the global circulating air flow is passed partially or at least approximately completely through one or more additional heating devices and that the temperature of the global circulating air flow is raised by a maximum of approximately 20 K, in particular a maximum of approximately 15 K, in particular without intermediate overheating and the resulting conversion of substances contained in the circulating air flow.

[0058] Further preferred features and / or advantages of the invention are the subject of the following description and the drawings of exemplary embodiments.

[0059] The figures show:

[0060] Fig. 1 is a schematic representation of a first embodiment of a treatment plant;

[0061] Fig. 2 is a schematic representation of a second embodiment of a treatment plant;

[0062] Fig. 3 is a schematic representation of a third embodiment of a treatment plant;

[0063] Fig. 4 is a schematic representation of a fourth embodiment of a treatment plant;

[0064] Fig. 5 is a schematic representation of a fifth embodiment of a treatment plant;

[0065] Fig. 6 is a schematic representation of a sixth embodiment of a treatment plant; Fig. 7 is a schematic representation of a seventh embodiment of a treatment plant;

[0066] Fig. 8 is a schematic representation of an eighth embodiment of a treatment plant;

[0067] Fig. 9 is a schematic representation of a ninth embodiment of a treatment plant;

[0068] Fig. 10 is a schematic representation of a tenth embodiment of a treatment plant;

[0069] Fig. 11 is a schematic representation of an eleventh embodiment of a treatment plant; and

[0070] Fig. 12 is a schematic representation of a twelfth embodiment of a treatment plant.

[0071] Identical or functionally equivalent elements are provided with the same reference numerals in all figures.

[0072] A first embodiment of a treatment plant, designated as a whole by 100, shown in Fig. 1 is used for the treatment of workpieces (not shown), in particular for the drying of vehicle bodies.

[0073] The treatment plant 100 is in particular a dryer 102 for drying previously coated vehicle bodies.

[0074] The treatment system 100 comprises a recirculation system 104, a treatment room 106 and a post-treatment room 108.

[0075] The treatment room 106 comprises several treatment room sections 110.

[0076] The treatment room sections 110 are assigned to several separate, local recirculation modules 112 of the recirculation system 104. The local recirculation modules 112 each circulate a local recirculation flow 114 in a local recirculation duct 116 through the respectively assigned treatment room section 110.

[0077] The local recirculation modules 112 preferably comprise a fan and a preferably electric heating device for heating the respective local recirculation air flow 114.

[0078] The workpieces to be treated, in particular vehicle bodies, are conveyed through the treatment chamber 106 and the post-treatment chamber 108 along a conveying direction 118.

[0079] The recirculation system 104 further comprises a global recirculation duct 120, which guides a global recirculation flow 122.

[0080] The global recirculating air flow 122 is discharged from the treatment room 106 at the level of one of the central treatment room sections 110 and is then at least partially fed back to the latter.

[0081] In this case, a global circulating air flow 124 discharged from one of the central treatment chamber sections 110 is fed to a processing device 126 arranged downstream of the treatment chamber 106 for processing.

[0082] The processing in the processing device 126 is preferably carried out by means of an RTO, which is preferably an electrically operated, flameless RTO.

[0083] A global recirculating air flow 128 treated in the treatment device 126 is divided downstream of the treatment device 126 into a diverted global recirculating air flow 130 and a recirculated global recirculating air flow 132.

[0084] The diverted global recirculating air flow 130 serves to transfer its thermal energy in a heat exchanger 133 to a supplied fresh air flow 134. The heat exchanger 133 is preferably an air-to-air heat exchanger, such as a tube-bundle or plate heat exchanger, in which the diverted global recirculating air flow 130 is cooled as much as possible during the transfer of thermal energy to the supplied fresh air flow 134, e.g., to 60°C, in order to retain as much thermal energy as possible in the treatment system 100.

[0085] The derived global recirculating air flow 130 is, after flowing through the heat exchanger 133, discharged as cooled exhaust air flow 136 either to the environment, ie via the roof, or fed to an exhaust gas line in which further cleaning takes place.

[0086] The standard volume flow of the cooled exhaust air flow 136 preferably corresponds to that of the supplied fresh air flow 134, whereby the fresh air flow 134 is partly sucked in via the locks and partly guided via the heat exchanger 133 (usually 500 Nm 3 / h suction per lock). In particular, this standard volume flow is 2,000 Nm 3 / h.

[0087] The heat transfer from the diverted global recirculating air flow 130 to the supplied fresh air flow 134 in the heat exchanger 133 results in a preheated fresh air flow 138, which is fed to the returned global recirculating air flow 132 for refreshment.

[0088] The mixed global circulating air flow 140 is then heated in an additional heating device 142.

[0089] In the first embodiment shown in Fig. 1, the heated global circulating air flow 144 is fed to an inlet lock 146 and / or an outlet lock 148 of the treatment chamber 106.

[0090] The recirculated global recirculating air stream 132, which is mixed with the preheated fresh air stream 138, is, as already mentioned, heated as a mixed global recirculating air stream 140 in the auxiliary heating device 142. The auxiliary heating device can be a combustion chamber, but is preferably an electric heating device. The heating brings the flowing global recirculating air stream to a temperature favorable or suitable for the lock operation of the inlet lock 146 and / or outlet lock. The auxiliary heating device 142 compensates for fluctuations in the outlet temperature from the conditioning device 126 through rapid temperature control, which fluctuations in the RTO systems are caused by the cyclical switching process between the states. The use of a downstream, preferably electric, auxiliary heating device with low inertia and rapid controllability is therefore particularly advantageous.

[0091] After the heated global recirculating air flow 144 is supplied to the treatment chamber 106, it is circulated there several times by means of the local recirculating air modules 112. The global recirculating air flow 120 is preferably a continuous process for conditioning the local recirculating air flow 114 circulated in the treatment chamber sections 110 and the local recirculating air modules 112.

[0092] The discharged global recirculating air flow 124, which is fed to the treatment device 126, is preferably based on the air quantity requirement of the inlet lock 146 and / or outlet lock 148, wherein this requirement is particularly dependent on the capacity utilization of the treatment plant 100.

[0093] The post-treatment chamber 108 adjoins the treatment chamber 106 in the conveying direction 118.

[0094] The aftertreatment chamber 108 comprises several aftertreatment chamber sections 150.

[0095] A heat exchanger 152 is assigned to the aftertreatment chamber 108, which transfers the thermal energy contained in an exhaust air stream 154 to a supplied fresh air stream 156. However, a bypass system (not shown) is more common, whereby the fresh air intake can suck in a partial flow of fresh air.

[0096] A preheated fresh air stream 158 is supplied to one of the aftertreatment chamber sections 150 by the heat exchanger 152.

[0097] A cascade air duct 160 is formed between the aftertreatment chamber sections 150. After transferring at least a portion of the thermal energy, the exhaust air stream is discharged downstream of the heat exchanger 152 as a cooled exhaust air stream 162.

[0098] Fig. 2 shows a second embodiment of the treatment plant 100.

[0099] In the embodiment of the treatment plant 100 shown in Fig. 2, the global recirculating air flow 144 heated in the additional heating device 142 is alternatively fed directly to the externally arranged, local recirculating air modules 112, ie the local recirculating air modules 112 which are assigned to the treatment room sections 110 with the inlet lock 146 and the outlet lock 148.

[0100] The supply to the two externally arranged, local recirculation modules 112 is carried out for reasons of balance and in favor of optimal flushing of the treatment room 106.

[0101] It is also conceivable to supply more than two recirculation modules 112.

[0102] In the case of a supply of the heated recirculating air flow 144 to the local recirculating air modules 112, the inlet lock 146 and the outlet lock 148 are operated as recirculating air locks.

[0103] It should be understood that the returned, heated circulating air, which due to the processing at least approximately corresponds to a clean gas, can be supplied to the outer areas of the treatment room 106, ie in particular to the corresponding local circulating air modules 112 and / or the inlet lock 146 and / or outlet lock 148, and is then conveyed in particular by the local circulating air duct 116 from both ends of the treatment room 106 towards the center of the treatment room 106.

[0104] The standard volume flow of the heated global circulating air flow 144 is preferably 10000 Nm 3 / h.

[0105] Consequently, the third embodiment of the treatment plant 100 shown in Fig. 3 shows a combination of the supply options of the heated circulating air flow 144, which is accordingly supplied both to the inlet lock 146 and the outlet lock 148 as well as to at least the two local circulating air modules 112 arranged externally in Fig. 3.

[0106] The combined supply is particularly advantageous when large amounts of air are provided or circulate in the global recirculation air duct, ie when the amount of air guided in the global recirculation air flow 122 is greater than the air requirement of the inlet lock 146 and outlet lock 148.

[0107] In the fourth embodiment of the treatment plant 100 shown in Fig. 4, the diverted global recirculating air flow 130, after the transfer of at least part of its thermal energy to the supplied fresh air flow 134 in the heat exchanger 133, is not embodied as cooled exhaust air, but is supplied as a supply air flow 164 to a pretreatment chamber 166, which is arranged upstream of the treatment chamber 106 with respect to the conveying direction 118 and comprises one or more pretreatment chamber sections 168.

[0108] The pretreatment room sections 168 are also each assigned to a local recirculation module 112.

[0109] The pretreatment chamber section 168 arranged at the beginning of the pretreatment chamber 166 also has its own inlet lock 146.

[0110] The supply air flow 164 can be fed to the inlet lock 146 of the pretreatment room 166 and / or to one of the local recirculation modules 112 assigned to the pretreatment room sections 168.

[0111] Preferably between the two or in the middle of several pretreatment room sections 168, an exhaust air flow 170 can also be carried out via the roof or into an exhaust gas line for cleaning, the standard volume flow of which is preferably 2,000 Nm 3 / h.

[0112] As an alternative to the fourth embodiment shown in Fig. 4, in a fifth embodiment of the treatment plant 100, which is shown in Fig. 5, the returned global recirculating air flow 138 is not mixed with preheated fresh air from a fresh air heat exchanger, but the supplied fresh air flow 134 is directly mixed with the treated global recirculating air flow 128.

[0113] As a result, the mixed global recirculating air flow 140 is fed without preheating to the inlet lock 146 of the pretreatment chamber 166 and / or to one of the local recirculating air modules 112 assigned to the pretreatment chamber sections 168.

[0114] Further alternatively to the fourth and fifth embodiments, Fig. 6 shows a sixth embodiment of a treatment plant 100 in which the exhaust air flow 170 of the pretreatment chamber 166 is guided to the heat exchanger 132.

[0115] The thermal energy contained in the exhaust air stream 170 is transferred to the supplied fresh air stream 134 in the heat exchanger 133.

[0116] It may also be advantageous if the cooled exhaust air stream 136 is not led out of the treatment plant 100 via the roof, but rather - as shown in Fig. 7 in a seventh embodiment of the treatment plant 100 - is fed to the cooled exhaust air stream 162 and / or the supplied fresh air stream 156 of the heat exchanger 152, which is assigned to the after-treatment chamber 108.

[0117] Feeding the cooled exhaust air stream 136 into the area of ​​the post-treatment chamber 150, which preferably forms a cooling zone, reduces the heating energy requirement there, especially during winter operation. Furthermore, this supply eliminates the need for an exhaust air duct in the treatment system 100 to discharge the exhaust air over the roof. This air is now guided out of the treatment system 100 via the exhaust air stream 162 of the post-treatment chamber 108.

[0118] In the event that the after-treatment room 108 does not have a heat energy requirement, the cooled exhaust air flow 136 associated with the global recirculating air flow 122 can also be led out over the roof together with the exhaust air flow 162 of the after-treatment room 108 with the aid of a bypass.

[0119] In an eighth and ninth embodiment of the treatment system 100, which is shown in Figs. 8 and 9, respectively, the preheated fresh air flow 138 is first further heated by means of the additional heating device 142, which is preferably an electric heating device, before being mixed with the recirculated global air flow 132, i.e. the additional device is arranged directly downstream of the heat exchanger 133 and not, as in the first to seventh embodiments, directly upstream of the treatment chamber 106.

[0120] The preheated fresh air flow 138 leading from the heat exchanger 133 is heated by means of the additional heating device 142 to a heated fresh air flow 172 such that, after being mixed with the returned global recirculating air flow 132, the fresh air flow 172 results in the heated global recirculating air flow 144, which has the temperature suitable or favorable for the treatment room 106 or the locks 146, 148.

[0121] In this case, the additional heating device 142 can be designed as a simple heating device, in particular without a protective casing, since it comes into contact exclusively with the supplied fresh air and not with the global circulating air.

[0122] Furthermore, the additional device 142 can be connected to or have a controller 174 in order to regulate the temperature of the air flow after the additional heating device 142 and / or after the heated fresh air flow 172 has been mixed into the recirculated global air flow 132.

[0123] Since the fluctuations in the outlet temperature of the conditioned global recirculating air flow 128 are cyclical and therefore easily predictable, the controller 174 can be operated in a model-predictive manner, ie the output of the additional heating device 142 can be adjusted in advance, thus preventing, in particular, specified limit values ​​from being reached and / or exceeded.

[0124] The heated global recirculating air flow 144 is fed to the inlet lock 146 and the outlet lock 148 of the treatment chamber 106 after admixing according to the eighth embodiment in Fig. 8, whereas in the ninth embodiment in Fig. 9 it is fed to at least two of the local recirculating air modules 112.

[0125] It is also conceivable here that the heated global recirculating air flow 144 is alternatively fed both to the locks 146, 148 and to at least one local recirculating air module 112. Fig. 10 shows a tenth embodiment of the treatment system 100, in which the diverted global recirculating air flow 130, comparable to the eighth and ninth embodiments, transfers its thermal energy in the heat exchanger 133 to a supplied fresh air flow 134, and the heated fresh air then flows through the preferably additional heating device 142 as a preheated fresh air flow 138 to be further heated therein. The additional heating device 142 is not absolutely necessary because the air mixture is brought to the desired mixing temperature by the additional heating device 176 anyway.

[0126] The heated fresh air flow 172 is then mixed with the recirculated global recirculation air flow 132, thereby forming a global recirculation air flow 144.

[0127] In the tenth embodiment, the local recirculation modules 112 do not comprise their own heating devices, but a central heating device 176, in particular an electric heating device, is arranged upstream of the local recirculation modules 112, which further heats the heated global recirculation air flow 144 before it is fed to the local recirculation air flows 114 via the local recirculation modules 112 and is circulated in the local recirculation guides 116.

[0128] Furthermore, the treatment plant 100 according to Fig. 10 has a bypass air duct 178, which can guide the discharged global air flow 124 past the processing device 126 if necessary.

[0129] The standard volume flow in the bypass air duct 178 is preferably in the range of 0 to 10000 Nm, depending on requirements 3 / h.

[0130] Fig. 11 shows an eleventh embodiment of the treatment plant 100, which, like the tenth embodiment, has a bypass air duct 178 to guide the discharged global air flow 124 past the processing device 126.

[0131] The bypass air recirculation system 178 is particularly advantageous when the treatment system is operated energy-efficiently at partial load. The global recirculation air flow 122, which is routed to the treatment device 126, which is preferably an electrically heated, flameless RTO, as well as the partial flow leaving the treatment system 100, can be adjusted depending on the load, for example, via flap control in the corresponding flow paths / flow ducts. The fresh air flow can also be adjusted accordingly using a volume flow measurement and a control device.

[0132] Alternatively, as shown in Fig. 11, a constant volume flow can be provided for all load cases. However, with reduced system utilization, only a partial flow is supplied to the treatment device 126, while the remaining global recirculation flow is routed via the bypass recirculation duct 178. Depending on the load case, the bypass can be adjusted in stages.

[0133] Instead of an adjustable recirculation volume share via the bypass, the entire global recirculation flow 122 to the processing device 126 can also be adjusted depending on the load.

[0134] In the global recirculation system 120, as shown in Fig. 11, a first fan 180 is arranged downstream of the processing device 126 and a second fan 182 is arranged downstream of the first fan 180, both of which serve in particular to extract global recirculation air from the treatment room 106.

[0135] However, it is also conceivable that the first fan 180 is arranged upstream of the processing device 126, while the second fan 182 is arranged downstream of the processing device 126.

[0136] The first fan 180 preferably drives the global circulating air at a constant rate, while the throughput of the second fan 182 can be adjusted to the air volume requirement of the locks 146, 148.

[0137] Similar to the seventh embodiment, the cooled exhaust air stream 136 is not discharged via the roof, but is fed into the exhaust air stream 162 and / or the fresh air stream 156 of the heat exchanger 152 of the post-treatment chamber 108. Although the introduction of foreign substances into the treatment system 100 by natural gas is avoided during treatment with electrical heating in the treatment device, contamination from paint components and their combustion products, which are released during the treatment of the workpieces in the treatment chamber 106, can still occur.

[0138] Contamination of channels or ducts by the following substances is conceivable: a) particles (silane compounds, phosphates); and / or b) other chemical reaction products (cracking products); and / or c) sulfur compounds.

[0139] The significantly reduced exhaust air operation of the treatment plant 100 according to the invention also results in d) an increase in the concentration of components such as CO2; and / or e) a decrease in the concentration of oxygen.

[0140] In particular, for cleaning the global recirculating air flow 124 supplied to the treatment device 126, the following measures can be taken with respect to contaminations a) to c): a) hot-area filters of the treatment plant 100, in particular a filter for sticky substances (e.g., phosphates), baffle filters, filter candles, pre-coating of filters, and cyclical filter cleaning; and / or b) chemical filters (chemisorption) or quicklime; and / or c) flue gas desulfurization.

[0141] All devices a) to c) can be arranged before and / or after the processing cleaning device 126.

[0142] Fig. 12 shows a twelfth embodiment of the treatment system 100, which essentially corresponds to the seventh embodiment. However, for illustrative purposes, the discharged global recirculating air flow 124 is discharged downward in Fig. 12, whereby the global recirculating air flow 122, unlike in the embodiments in Figs.

[0143] 1 to 11, runs clockwise. The global recirculation duct 120 of the treatment system 100 in Fig. 12 has an inlet 184 upstream of the additional heating device 142, with which the mixed global recirculation flow 140 can be fed to the inlet lock 146 without additional heating.

[0144] Furthermore, the recirculating air duct 120 has a return 186 downstream of the additional heating device, with which at least a part of the heated global recirculating air flow can be guided into the feed 184.

[0145] A first throttle valve 188 is arranged in the supply 184 and a second throttle valve 190 is arranged in the return 186.

[0146] By means of the flap-controlled and / or regulated supply 184 and the likewise flap-controlled and / or regulated return, two temperature levels can be set for the inlet and the outlet of the treatment chamber 106, in particular when heating the treatment chamber 106; namely a lower temperature level at the inlet with preferably maximum heating at the outlet.

[0147] During operation, this temperature difference can be adjusted by controlling and / or regulating the throttle valves 188, 190.

[0148] Furthermore, the following possibilities are known or at least conceivable for saving energy during start-up and shut-down of the treatment plant 100: a) Optimized heating, i.e., exhaust-free; in this case, no exhaust air flow is directed over the roof, the recirculation is complete, and all flaps for a partial flow leaving the treatment plant are closed; b) A break-time mode, which is also exhaust-free; and c) An exhaust-free standby operation over, for example, two shifts, in which the roller doors are closed and all fans in the recirculating air are reduced to a minimum power.

[0149] Treatment plant dryer

[0150] Recirculation system

[0151] Treatment room Post-treatment room Treatment room section Local recirculation module Local recirculation flow Local recirculation duct

[0152] Conveying direction global recirculation flow global recirculation flow discharged global recirculation flow treatment device treated global recirculation flow discharged global recirculation flow returned global recirculation flow heat exchanger

[0153] Fresh air flow Cooled exhaust air flow Preheated fresh air flow Mixed global recirculation air flow Additional heater Heated global recirculation air flow Inlet lock

[0154] Outlet lock

[0155] Aftertreatment room section heat exchanger

[0156] Exhaust air flow

[0157] Fresh air flow preheated fresh air flow recirculating air flow cooled exhaust air flow

[0158] Supply air flow

[0159] Pre-treatment room

[0160] Pretreatment room section

[0161] Exhaust air flow heated fresh air flow

[0162] Controller central heating device

[0163] Bypass air circulation first fan second fan

[0164] Feeding

[0165] Feedback first throttle valve second throttle valve

Claims

Claims: Recirculating air system (104), in particular for a treatment system (100) for treating workpieces, wherein the recirculating air system (104) comprises: several local recirculating air modules (112) by means of which local recirculating air streams (114) can be supplied to, passed through and discharged from a treatment room (106), wherein the local recirculating air streams (114) pass through the treatment room (106) multiple times; and a global recirculating air system (120) by means of which a global recirculating air stream (122) can be discharged from the several local recirculating air modules (112) and / or the treatment room (106), processed by means of a processing device (126) and supplied again to at least one of the several local recirculating air modules (112) and / or the treatment room (106).Recirculating air system (104) according to claim 1, characterized in that the conditioning device (126) is or comprises a conditioning device (126) for conditioning, in particular for cleaning, the global recirculated air stream (122), wherein the conditioning device (126) is or comprises a thermal conditioning device, in particular a purely electrically operated, preferably flameless, regenerative thermal oxidizer. Recirculating air system (104) according to claim 2, characterized in that the thermal conditioning device (126) is or comprises an electric heating device, wherein it is preferably provided that thermal conditioning is carried out exclusively by direct electrical heating, in particular electrical resistance heating, and / or by exothermic conversion of components of the global recirculated air stream (122).Recirculating air system (104) according to one of claims 1 to 3, characterized in that the processing device (126) is provided and / or designed independently of a discharge device for the discharge of exhaust air. is, in particular, spatially separated from an exhaust air duct which serves to discharge exhaust air (136) from the recirculation system (104). Recirculation system (104) according to one of claims 1 to 4, characterized in that, by means of the local recirculation modules (112), different and / or adjacent treatment room sections (110) of the treatment room (106) can be supplied with local recirculation air streams (114), and that, by means of the global recirculation system (120), global recirculation air can be supplied to or adjacent to one or more local recirculation modules (112), and / or that, by means of the global recirculation system (120), recirculation air from one or more other local recirculation modules (112) can be discharged as a global recirculation air stream (120).A recirculating air system (104) according to any one of claims 1 to 5, characterized in that the global recirculating air system (116) opens into one or more airlocks (146, 148) of the treatment chamber (106) for the fluid-effective separation of an atmosphere in the treatment chamber (106) from the surroundings of the recirculating air system (104). A recirculating air system (104) according to any one of claims 1 to 6, characterized in that the recirculating air system (104) comprises one or more additional heating devices (142) provided in addition to the treatment device (126), by means of which a) one or more partial flows of the global recirculating air stream (122); and / or b) the entire global recirculating air stream (122); and / or c) one or more partial flows of one or more local recirculating air streams (114) can be heated.Recirculating air system (104) according to claim 7, characterized in that a) an airflow passed through the treatment device (126) can be heated at least temporarily by means of the treatment device (126) to a temperature which causes a chemical conversion of substances contained in the airflow, in particular solvents; and / or b) an airflow passed through one or more auxiliary heating devices (142) can be heated by means of the one or more auxiliary heating devices (142), in particular without significant conversion of substances contained in the airflow. A recirculating air system (104) according to any one of claims 1 to 8, characterized in that the recirculating air system (104) comprises at least one heat exchanger (133) by means of which thermal energy contained in a derived global recirculated air stream (130) or in an exhaust air stream (170) can be transferred to a fresh air stream (134) supplied to the global recirculated air stream (122). A recirculating air system (104) according to claim 9, characterized in that a cooled exhaust air stream (136) discharged from the heat exchanger (133) can be supplied to a fresh air stream (156) and / or a cooled exhaust air stream (162) which are assigned to a post-treatment chamber (108).A recirculating air system (104) according to any one of claims 1 to 10, characterized in that at least one filter device and / or sorption device, in particular an adsorption and / or absorption device, is arranged downstream and / or upstream of the treatment device (126) for concentrating or reducing at least one element, compound, and / or mixture of the global recirculated air stream (122). A treatment system (100) with a recirculating air system (104) according to any one of claims 1 to 11. A treatment system (100) according to claim 12, characterized in that the treatment system (100), in particular one or more or all electrically operated auxiliary heating devices and / or a treatment device, can be supplied with a medium voltage of at least approximately 3 kV and / or at most approximately 8 kV, in particular 4,160 V to 6,600 V.Method for operating a recirculating air system (104) in which several local recirculating air streams (114) are supplied to a treatment room (106) by means of several local recirculating air modules (112), passed through it and discharged from it, wherein the. Local recirculated air streams (114) flow through the treatment chamber (106) multiple times; and in which a global recirculated air stream (122) is extracted from the multiple local recirculated air modules (112) and / or the treatment chamber (106) by means of a global recirculated air guide (120), processed, and fed again to at least one of the multiple local recirculated air modules (112) and / or the treatment chamber (106). The method according to claim 14, characterized in that the global recirculated air stream (122) is heated for processing, in particular directly and / or exclusively by means of an electric resistance heater and / or by exothermic conversion of components of the global recirculated air stream (122).A method according to claim 14 or 15, characterized in that at least approximately 90%, and in particular at least approximately 95%, of the total volume flow of the global recirculated air stream (122) discharged from the treatment chamber (106) is treated and returned to the treatment chamber (106). A method according to any one of claims 14 to 16, characterized in that the treatment of the global recirculated air stream (122) is carried out independently of any discharge of exhaust air (136), and in particular is spatially separated from an exhaust air duct which serves to discharge exhaust air (136) from the recirculated air system (104).A method according to any one of claims 14 to 17, characterized in that at least approximately the entire global recirculated airflow (124) discharged by the local recirculation modules (112) is thermally treated during each circulation within the global recirculation system (120), in particular without the use of additives or other introduction of substances into the global recirculated airflow (122). A method according to any one of claims 14 to 18, characterized in that the global recirculated airflow (122) is at least partially or at least... approximately completely passed through the processing device (126) and thereby heated at least temporarily to a temperature which causes a chemical transformation of substances contained in the air stream, in particular solvents, and that at least a part of the heat temporarily contained in the global recirculated air stream (122) is recuperated, so that the global recirculated air stream (122) leaves the processing device (126) at a temperature which lies between an inlet temperature and a temporary maximum temperature.Method according to one of claims 14 to 19, characterized in that the global recirculated air stream (122) is partially or at least approximately completely passed through one or more auxiliary heating devices (142) and that the temperature of the global recirculated air stream (122) is thereby increased by at most approximately 20 °C, in particular at most approximately 15 °C, in particular without intermediate overheating and the resulting transformation of substances contained in the recirculated air stream.

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