Exhaust air control system

Abstract

Temperature control system (2) for heat treatment for the purposes of tempering or coating drying, in particular of powder coatings, paints or other surface-forming layers, of workpieces to be coated (4) with a plant housing (6) that encloses a heat treatment area (8) for the workpieces (4) in which they can be subjected to an increased heat treatment temperature, which can be generated by means of a heating device (W), and with an exhaust air device (14) by means of which an exhaust air flow (A) can be generated for the removal of exhaust air, water vapor and / or reaction products from the heat treatment area (8) and which has an actuating device (16) for changing an exhaust air volume flow (V) of the exhaust air flow (A), characterized in that the actuating device (16) is part of a control arrangement (22) by means of which the exhaust air volume flow (V) can be controlled, wherein the actuating device (16) has a throttle damper (20) adjustable by means of an actuator (24) for adjusting the exhaust air volume flow (V), and the actuator (24) can be controlled by a control electronics (30) of the control arrangement (22), which controls the actuator (24) depending on a comparison of a determined actual volume flow value (VI) with a setpoint volume flow value (VS) of the exhaust air volume flow (V) specified by the control electronics (30), where the target volume flow rate (VS) of the exhaust air volume flow rate (V) can be determined as a function of a difference between an actual temperature value (TI) and a target temperature value (TS) and depending on the process phase.

Description

[0001] The invention relates to a temperature control system for the heat treatment of workpieces for the purpose of tempering, curing, and / or coating drying, in particular of powder coatings, paints, or other surface-forming layers on metal workpieces, according to the preamble of claim 1. The invention further relates to a method for operating such a temperature control system. This system comprises a housing that encloses a heat treatment area for the workpieces. Within this heat treatment area, the workpieces can be subjected to an elevated heat treatment temperature, for example, by means of circulating air, thermal radiation (infrared), or combinations thereof. The heat treatment is carried out at a temperature higher than the ambient temperature, which is generated by a heating device.The heating device can, for example, include a burner and a blower or an oven. Furthermore, the temperature control system has an exhaust air device by means of which an exhaust airflow can be generated to remove exhaust air, water vapor and / or reaction products, such as cracking products in particular, from the heat treatment area, and which includes an adjustment device for changing the exhaust air volume flow.

[0002] Conventional temperature control systems typically feature exhaust air devices with fixed, adjustable dampers. These dampers are set to maintain a target exhaust air flow rate as close as possible to the desired volume flow rate during the temperature control process. Differential pressure switches monitor the exhaust air flow and can shut down the system if the target flow rate is undershot. Alternatively or additionally, mobile measurements of specific parameters are also known. If predetermined threshold values ​​are exceeded or fallen below, the measured values ​​allow for manual readjustment of the exhaust air devices or shutdown of the system.

[0003] From CN 106955829 A, a temperature control system is known, comprising a pre-drying section, a powder application section, and a curing section. The system incorporates a hot air recirculation system and an exhaust air device for discharging exhaust gases.

[0004] A disadvantage of conventional temperature control systems is that the exhaust air system and / or airflow can only be adjusted to changing process conditions with great difficulty. Therefore, the exhaust air system is usually set to a fixed value to generate a predetermined target volume flow during a heat treatment process. This fixed setting must be chosen to ensure sufficient removal of substances that are hazardous to health or operations and that are generated during heat treatment from the heat treatment area.Due to this essentially fixed target volume flow rate throughout a heat treatment process, a relatively high heat loss and / or a high time requirement for temperature changes can occur in the different heat treatment phases, depending on the treatment temperature to be set, which in turn has a negative impact on the economic efficiency of the respective heat treatment process.

[0005] DE 10 2015 219 898 A1 describes a workpiece processing system for drying and / or hardening coated workpieces in a multi-zone process chamber. A process air line is provided for introducing and / or discharging process air into the individual zones of the process chamber. Furthermore, a control device is provided by means of which the heating power of a heating device can be adjusted to a process air volume or vice versa. The aim is to achieve the lowest possible energy consumption.

[0006] DE 10 2015 012 466 A1 describes a device for temperature control of vehicle bodies with a temperature control chamber. Fresh air is supplied to the temperature control chamber via a fresh air supply system, and recirculated air from the exhaust air of the temperature control chamber is supplied via a recirculation system. A control device is configured such that the total volume flow of supplied fresh air and recirculated air does not fall below a minimum limit.

[0007] The object of the invention is to avoid the aforementioned disadvantages in a temperature control system of the type and to enable more economical heat treatment.

[0008] This problem is solved by a temperature control system with the features of claim 1. The actuator of the exhaust air device is part of a control arrangement by which the exhaust air volume flow can be regulated, or is necessarily regulated, depending on measured values. The actuator has a throttle valve adjustable by means of an actuator motor for setting the exhaust air volume flow, the actuator motor being controllable by control electronics of the control arrangement. These control electronics control the actuator by comparing the determined actual volume flow value with a target volume flow value of the exhaust air volume flow specified by the control electronics.The target volume flow rate of the exhaust air is determined by the control electronics based on the difference between a measured actual temperature and a predefined target temperature, as well as depending on the process phase or the current treatment phase of the temperature control system, such as a heating phase, a treatment phase, and / or a cooling phase of the respective heat treatment process. This control of the exhaust air volume flow allows it to be adapted to the different heat treatment phases of a heat treatment process, thereby increasing the overall process efficiency. By controlling the exhaust air flow across the different heat treatment phases, the heat requirement can be minimized and the time required to reach a desired temperature reduced. The actuator can, for example, be a Belimo motor.This allows for particularly precise and automated adjustment of the throttle valve and exhaust air volume flow based on measured values. This enables the exhaust air volume flow to be continuously adapted to each current heat treatment phase and its corresponding process conditions throughout the entire heat treatment process. The actuator can be controlled in such a way that the actual volume flow value is continuously adjusted to the target volume flow value, which changes particularly between the different heat treatment phases. This allows a preferred exhaust air flow to be predefined for each heat treatment phase, thereby optimizing treatment time and heat requirements. Alternatively or additionally, the target volume flow value can also be entered manually.

[0009] In a particularly preferred embodiment, the control arrangement includes flow sensors for determining the actual volume flow rate of the exhaust air. This allows the current exhaust air volume flow rate to be determined throughout a heat treatment process and the setting of the actuator to be adjusted accordingly.

[0010] Advantageously, the control arrangement incorporates temperature sensors to determine the actual temperature value in the heat treatment area, and the control electronics determine the target volume flow rate of the exhaust air based on the difference between the determined actual temperature value and a predefined target temperature value, such as the desired heat treatment temperature during the treatment phase. This allows the exhaust air flow to also be used to assist in setting the heat treatment temperature in the heat treatment area and to be taken into account when controlling the heating device.

[0011] Preferably, the control arrangement includes air sensors for determining at least one other air parameter in the heat treatment area, and the setpoint volume flow rate can be determined by the control electronics as a function of at least one air parameter measured by the air sensors, such as a measured value for CO, CO2, an explosive substance, humidity, powder content, and / or pressure or vacuum. This ensures that the substances in question are reliably removed from the heat treatment area and, in particular, do not reach a critical value at which there would be a risk to operators or a reduction in the quality of the workpieces being treated.

[0012] It is advantageous if the control system continuously determines the actual temperature value and / or the actual volume flow rate and / or at least one air measurement value in the heat treatment area and signals this information to the control electronics. This allows the exhaust air flow and the heat treatment temperature to be continuously controlled during operation of the temperature control system based on the measured values, which in turn minimizes the heat demand throughout a heat treatment process.

[0013] Preferably, the control arrangement includes at least one transmitter by means of which the at least one measured value determined by the flow sensor, the temperature sensor and / or the other air measuring sensor can be continuously signaled to the control electronics in order to ensure precise and delay-free control of the exhaust air device and / or the heating device.

[0014] Alternatively or additionally, the control electronics are connected to an input interface, and the target volume flow rate of the exhaust air volume flow can be determined based on workpiece parameters of at least one of the workpieces to be coated. These workpiece parameters can be transmitted to the control electronics via the input interface. The workpiece parameters can include, for example, dimensions, weight, material specifications, coating type, and / or thickness. The input interface can include a keyboard, voice input, scanning capability, and / or sensors for the automatic acquisition of specific workpiece parameters.

[0015] Furthermore, the control arrangement advantageously includes an output and / or storage unit by which the signaled measured values ​​can be output and / or documented. Output can be achieved, for example, through printing, voice output, or by forwarding information, such as within a network. Documentation can also be accomplished by storing the data in local or external memory. This allows the energy flows and temperature profiles generated during a heat treatment process to be monitored and documented, for example, for quality assurance purposes.

[0016] Furthermore, the aforementioned problem is solved by a method for operating a temperature control system in one of the aforementioned embodiments, in which a heat treatment area to be loaded with one or more coated workpieces is heated to a target temperature value in a heating phase, the target temperature value is essentially maintained in a treatment phase, and the heat treatment area is cooled relative to the target temperature value in a cooling phase, wherein a free flow cross-section of the exhaust air device is adjusted depending on the process phase, i.e., depending on the respective current treatment phase. In the heating phase, the free flow cross-section of the exhaust air device is reduced to a minimum or completely closed by the control device in order to minimize or completely stop the exhaust air volume flow.During the cooling phase, the free flow cross-section of the exhaust air system is increased to a maximum by the actuator to maximize the exhaust air volume flow. This allows the actual temperature in the heat treatment area to be adjusted to the target temperature particularly quickly in each treatment phase. As a result, the heating phase, in which the target temperature is set in the heat treatment area, can be carried out very efficiently in a short time and with minimized heat consumption. Overall, this allows for significant savings in fuel quantities, especially oil or gas. Furthermore, the minimized exhaust air volume flow results in substantial CO2 savings. Additionally, the cooling phase, in which the heat treatment area is cooled below the target temperature of the treatment phase, can be carried out in a particularly short time.The shortened cooling phase allows the recirculating air fans, which must be operated during the heating and treatment phases in the heat treatment area, to be switched off earlier, thus saving electricity.

[0017] Furthermore, it is advantageous if the free flow cross-section of the exhaust air device is adjusted by the actuator depending on the difference between the setpoint temperature and an actual temperature value determined by the temperature sensors. In this way, the compensation of any difference between the setpoint and actual temperature values ​​can be supported and thus accelerated in all treatment phases of a heat treatment process, and especially during transitions between treatment phases.

[0018] Preferably, the exhaust air volume flow profile of the exhaust air system is determined and documented throughout a heat treatment process. This allows, for example, the creation of an emissions certificate. Furthermore, in conjunction with temperature monitoring, this method can determine how much heat is lost through the exhaust air during a heat treatment process. Overall, this allows for better recording and monitoring of the energy flows within the temperature control system.

[0019] Advantageously, a temperature profile in the heat treatment area can also be determined and documented throughout a heat treatment process, for example to create a quality certificate or to be able to prove a heat requirement for the heat treatment process in question.

[0020] It should be noted that all the features of the object according to the invention described above are interchangeable or combinable with each other, provided that such an exchange or combination is not excluded for technical reasons.

[0021] The figures illustrate an exemplary embodiment of the invention. They show: Fig. 1 a longitudinal section through a temperature control system according to the invention, Fig. 2 a cross-section through the temperature control system on level II Fig. 1 and Fig. 3 a temperature and exhaust air volume flow diagram of a heat treatment process carried out with the temperature control system.

[0022] Fig. Figure 1 shows a temperature control system 2 for the heat treatment of workpieces 4, such as coated metal parts. The heat treatment serves the purpose of temperature control, curing, and / or coating drying, particularly of powder coatings, paints, or other surface layers on the metal workpieces to be coated. The temperature control system 2 has a housing 6 that encloses a heat treatment area 8, into which the workpieces 4 to be treated can be moved, for example, via a rail-guided transport system T. Alternatively or additionally, the workpieces could also be moved manually or by means of a lifting / transporting device, such as a crane, forklift, or other vehicle.In heat treatment area 8, an increased heat treatment temperature can be generated by means of a heating device W, which for this purpose includes, for example, a burner 10 and a blower 12. The heating device W can thereby generate, for example, a circulating airflow U in heat treatment area 8.

[0023] As from Fig. As can be seen in section 2, the recirculation airflow U can be used as an alternative or in addition to the floor-side fan 12 according to Fig. 1 can also be generated by at least one laterally arranged blower 12, by means of which the recirculated airflow U can be generated, in particular also vertically.

[0024] As from Fig. As can be further seen from Figure 1, the temperature control system 2 has an exhaust air device 14, through which an exhaust air flow A can be generated from the heat treatment area 8. This exhaust air device 14 has an actuating device 16 by means of which an exhaust air volume flow V, or a volume of air per unit of time that can be passed through the exhaust air device 14 and generates the exhaust air flow A, can be changed or set. The exhaust air volume flow V can be set by any known and suitable means. For example, the actuating device 16 can, as shown, enclose a free flow cross-section 18, which can be enlarged, reduced, or completely closed by means of a throttle valve 20. Advantageously, the exhaust air device 14 has, as shown, a controllable exhaust air fan 32, with which the exhaust air flow A can be actively generated, intensified, or decelerated.

[0025] As from Fig. As can be further seen from Figure 1, the exhaust air device 14 is part of a control arrangement 22 which, in addition to the exhaust air device 14, includes at least one actuator 24 for adjusting the throttle valve 20, a temperature sensor 26 for measuring an actual temperature value TI in the heat treatment area 8, a flow sensor 28 for measuring an actual volume flow value VI, at least one air measurement sensor 25 for determining at least one further air measurement value LM and a control electronics 30 for controlling the heating device W, the actuator 24 and / or the exhaust air blower 32 depending on the determined actual temperature value TI, the actual volume flow value and / or the further air measurement value LM.

[0026] The at least one air measurement value LM can be determined by a parameter of the recirculated airflow U relevant to operational safety, the health of the operating personnel and / or the treatment quality of the workpieces 4. For example, the air measurement value LM can refer to the content of CO or CO2, at least one explosive substance, moisture, a powder or paint and / or to the pressure or negative pressure of the air present in the heat treatment area 8.

[0027] Furthermore, the control arrangement 22 can include an output and / or storage unit 34, which, for example, is configured as part of a control cabinet, a computer workstation, and / or a computer network, as shown. In particular, the output and / or storage unit 34 has a monitor 35 for the optical output of information and at least one input interface SS for inputting workpiece parameters of at least one workpiece 4 to be processed. The input interface SS is exemplified by a keyboard. Alternatively or additionally, an input interface SS in the form of voice input, a scanner, or other sensor technology can also be provided.

[0028] Wired and / or wireless connection means 36 are provided for connecting the individual elements of the control arrangement 22, which can be formed by any known and suitable signal transmission means, such as data or coaxial cables, radio, Bluetooth or infrared transmission means.

[0029] In addition, the air measurement sensor 25, the temperature sensor 26 and the flow sensor 28 each have a transmitter 38 by means of which the determined actual temperature values ​​TI, the actual volume flow value VI and / or the other air measurement values ​​LM can be signaled to the control electronics 30.

[0030] The control electronics 30 contain at least one setpoint temperature value TS or can be determined in a predetermined manner, for example, depending on characteristics of the workpieces 4 to be treated, such as at least one dimension, surface finish, and / or coating thickness of the workpiece. The actual temperature value TI determined by the temperature sensor 26 can be compared with the setpoint temperature value TS by the control electronics 30 in order to detect any deviation between them and adjust the actual temperature value TI accordingly.

[0031] Furthermore, at least one target volume flow value VS can be stored in the control electronics 30 or determined in a predetermined manner, for example depending on the process phase, i.e. depending on whether the heat treatment process is currently in a heating phase PH, a treatment phase PB or a cooling phase PK according to Fig. 3. For each treatment phase, a preferred target volume flow rate VS of the exhaust air flow A is predefined, which optimizes the ratio of treatment time to heat requirement. The actual volume flow rate VI determined by the flow sensor 28 can then be compared with the target volume flow rate VS by the control electronics 30 in order to detect any deviation between them and adjust the actual volume flow rate VI accordingly.

[0032] Furthermore, at least one threshold value SW of one of the other air measurement values ​​LM can be stored in the control electronics 30 or determined in a predetermined manner, for example, depending on a coating of the workpieces 4 to be treated or a treatment method intended for them. The air measurement value LM determined by the air measurement sensor 25 can thus be compared with the respective threshold value SW in order to detect, if necessary, an exceedance or fall below the relevant threshold value SW and to correct it by means of the control electronics 30.

[0033] Preferably, the actual temperature value TI, the actual volume flow value VI and / or at least one other air measurement value LM are continuously determined in order to be able to continuously adjust these values ​​as needed via the control electronics 30.

[0034] In the above-mentioned adjustments of the actual temperature value TI, the actual volume flow value VI and / or at least one other air measurement value LM, the control electronics 30 controls the exhaust air device 14 and the heating device W in such a way that as little heat energy as possible is consumed when adjusting to the setpoint values ​​and complying with the threshold values.

[0035] As in Fig. As further shown in Figure 1, a section 40 can also be connected downstream of the exhaust air device 14, in which heat energy carried away via the exhaust air flow A can be further utilized. Section 40 can, for example, be formed by a separate room or a separate system, or by an additional heating device, such as a furnace for heating a room or system. The temperature of the additional heating device can, for example, be regulated depending on the exhaust air flow A.

[0036] The operation of temperature control system 2 is running according to Fig. 3 as follows: During the heating phase PH, the heat treatment area 8 is first heated by means of the burner 10 and the blower 12 of the heating device W in order to raise the actual temperature value TI from an ambient temperature TU to the target temperature value TS intended for the respective heat treatment process, as shown in the diagram according to Fig. 3 shown. Here, the target temperature value can, for example, range between 100 and 300°C, depending on the treatment method intended for the workpieces 4 in question.

[0037] In order to keep the time required to reach the target temperature TS as short as possible and at the same time minimize the energy required in the heating phase PH, the free flow cross-section 18 of the exhaust air device 14 is designed according to Fig. 1. At least at the beginning of the heating phase, the pH is closed or reduced to a minimum.

[0038] When the target temperature TS is reached, the workpieces 4 to be treated are moved into the heat treatment area 8 to start treatment phase PB. The actual temperature TI is then continuously adjusted throughout treatment phase PB to the target temperature TS, which is fixed for treatment phase PB or determined based on parameters of the workpieces 4, in order to ensure optimal heat treatment.

[0039] At the same time, at the latest when the workpieces 4 are received in the heat treatment area 8, the actual volume flow value VI, which can be determined via the flow sensors 28, is also adjusted to a specific target volume flow value VS in order to ensure a continuous removal of substances hazardous to health or operations from the recirculated air flow U from the heat treatment area 8 via the exhaust air flow A and, in particular, to avoid their concentration.

[0040] Depending on the difference between the setpoint temperature TS and the measured actual temperature TI, as determined by the temperature sensor 26, the control unit 30 continuously adjusts the free flow cross-section 18 of the exhaust air device 14 via the actuator 16 throughout the treatment phase PB. A heat energy loss generated by an increased exhaust air flow A can simultaneously be compensated for by the control electronics 30 by temporarily switching on or increasing the power output of the heating device W.

[0041] In addition, the control electronics 30 can change the setpoint volume flow rate VS if a threshold value SW of one of the other air measurements LM is detected by the air measurement sensor 25 as being exceeded or fallen below, in order to adjust, for example, the CO, CO2, moisture, or powder content, or a content of explosive substances. A corresponding adjustment event E of the setpoint volume flow rate VS is in Fig. Figure 3 illustrates this. The adjustment event E with respect to the exhaust air volume flow V allows the respective parameter to be set to a concentration at which a risk to the operating personnel and / or damage to the temperature control system 2 or the workpieces 4 can be ruled out, and a specified treatment quality of the workpieces 4 is ensured. Here, too, the heat energy loss generated by the variable exhaust air flow A can be compensated for by the control electronics 30 by switching on or changing the power output of the heating device W.

[0042] After a treatment phase PB duration stored in or determined by the control electronics 30, the cooling phase PK begins. As shown in the diagram... Fig.As can be seen in Figure 3, the actual volume flow rate VI of the exhaust air flow A is increased by maximizing the free flow cross-section 18. This minimizes the duration of the cooling phase PK. The shortened cooling phase PK allows the fans 12 in the heat treatment area 8, which operate at elevated temperatures to protect the temperature control system 2 and / or the workpieces 4, to be switched off earlier, thus saving drive energy or electricity.

[0043] Throughout the entire heat treatment process, the exhaust air volume flow profile VV of the actual volume flow value VI can be determined using the flow sensor 28 and documented using the output and / or storage unit 34, for example, to generate an emissions certificate. Furthermore, in conjunction with temperature measurement, this allows the amount of heat lost via the exhaust air flow A during a heat treatment process to be determined. Overall, this enables the energy flows of the temperature control system 2 to be recorded and monitored.

[0044] Furthermore, throughout the entire heat treatment process, a temperature profile TV of the actual temperature value TI in the heat treatment area 8 can be recorded using the temperature sensor 26 and documented using the output and / or storage unit 34, in order to provide, for example, proof of quality for the heat-treated workpieces 4 or their coating.

[0045] It should be noted that all the elements and features described above of the various embodiments of the object according to the invention are interchangeable or combinable with each other, provided that such an exchange or combination is not excluded for technical reasons.

Claims

[1] Temperature control system (2) for heat treatment for the purposes of tempering or coating drying, in particular of powder coatings, paints or other surface-forming layers, of workpieces to be coated (4) with a system housing (6) that encloses a heat treatment area (8) for the workpieces (4) in which they can be subjected to an increased heat treatment temperature, which can be generated by means of a heating device (W), and with an exhaust air device (14) by means of which an exhaust air flow (A) can be generated for the removal of exhaust air, water vapor and / or reaction products from the heat treatment area (8) and which has an actuating device (16) for changing an exhaust air volume flow (V) of the exhaust air flow (A), characterized by, that the actuating device (16) is part of a control arrangement (22) by means of which the exhaust air volume flow (V) can be controlled, wherein the actuating device (16) has a throttle damper (20) adjustable by means of an actuator (24) for adjusting the exhaust air volume flow (V), and the actuator (24) can be controlled by a control electronics (30) of the control arrangement (22), which controls the actuator (24) depending on a comparison of a determined actual volume flow value (VI) with a setpoint volume flow value (VS) of the exhaust air volume flow (V) specified by the control electronics (30), where the target volume flow rate (VS) of the exhaust air volume flow rate (V) can be determined as a function of a difference between an actual temperature value (TI) and a target temperature value (TS) and depending on the process phase. [2] Temperature control system according to claim 1, characterized by, that the control arrangement (22) has a flow sensor (28) for determining the actual volume flow value (VI) of the exhaust air volume flow (A). [3] Temperature control system according to claim 1 or 2, characterized by , that the control arrangement (22) has a temperature sensor (26) for determining the actual temperature value (TI) in the heat treatment area (8) and the control electronics (30) determines the setpoint volume flow rate (VS) of the exhaust air volume flow rate (V) as a function of a difference between the actual temperature value (TI) and a setpoint temperature value (TS). [4] Temperature control system according to one of claims 1 to 3, characterized by , that the control arrangement (22) has an air measurement sensor (25) for determining at least one other air measurement value (LM) in the heat treatment area (8) and the setpoint volume flow value (VS) can be determined by the control electronics (30) depending on the at least one air measurement value (LM). [5] Temperature control system according to any one of claims 1 to 4, characterized by , that the control arrangement (22) continuously determines the actual temperature value (TI) and / or the actual volume flow value (VI) and / or the at least one air measurement value (LM) and signals it to the control electronics (30). [6] Temperature control system Claim 5, characterized by , that the control arrangement (22) has at least one transmitter (38) by means of which at least one of the measured values ​​(TI; VI; LM) can be signaled to the control electronics (30). [7] Temperature control system according to any one of claims 1 to 6, characterized by , that the control electronics (30) is connected to an input interface (SS) and the setpoint volume flow value (VS) of the exhaust air volume flow (A) can be determined as a function of workpiece parameters of at least one of the workpieces (4) to be coated, which can be transferred to the control electronics (30) at the input interface (SS). [8] Temperature control system according to any one of claims 1 to 7, characterized by , that the control arrangement (22) has an output and / or storage unit (34) by means of which the signaled measured values ​​(TI; VI; LM) can be output and / or documented. [9] Method for operating a temperature control system according to one of claims 1 to 8, wherein a heat treatment area to be equipped with one or more coated workpieces (4) During a heating phase (PH), the heat treatment area (8) is heated to the target temperature value (TS), During a treatment phase (PB), the actual temperature value (TI) is adjusted to the target temperature value (TS). During a cooling phase (PK) the heat treatment area (8) is cooled down compared to the target temperature value (TS), characterized by, that a free flow cross-section (18) of the exhaust air device (14) is adjusted depending on the process phase, wherein in the heating phase the free flow cross-section (18) of the exhaust air device (14) is reduced to a minimum by the actuating device (16) and in the cooling phase (PK) the free flow cross-section (18) of the exhaust air device (14) is increased to a maximum by the actuating device (16). [10] Method according to claim 9, characterized by , that in the treatment phase (PB) the free flow cross-section (18) of the exhaust air device (14) is adjusted by the actuating device (16) depending on a difference between the setpoint temperature value (TS) and the actual temperature value (TI) determined by the temperature sensor (26). [11] Method according to claim 9 or 10, characterized by , that an exhaust air volume flow profile (V) of the exhaust air device (14) is determined and documented over an entire heat treatment process. [12] Method according to any one of claims 9 to 11, characterized by , that a temperature profile (TV) in the heat treatment area (8) is determined and documented throughout the heat treatment process.

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