JP5450291B2 - Heat exchange type hot air generator - Google Patents

Description

  The present invention relates to a heat exchange type hot air generator. More specifically, the present invention relates to a PID-controlled heat exchange type hot air generator that maintains the temperature of hot air after heat exchange, which has been raised by waste heat recovery, at a set temperature.

  The heat exchange type hot air generator has an advantage that it can obtain clean hot air and can reduce running cost by effectively using waste heat. For this reason, it is often used as a hot air source such as a food processing facility or a drying furnace for painted objects.

  As a PID-controlled heat exchange type hot air generator that maintains the temperature of hot air after heat exchange, which has been raised by waste heat recovery, at a set temperature, for example, as shown in FIG. What is used as a heat source for a hot-air heating furnace with a deodorizing furnace that combines a hot-air heating furnace 101 for baking a film and a deodorizing furnace 102 for burning and deodorizing a flammable harmful gas generated from a coating film in the hot-air heating furnace 101. It has been proposed (Patent Document 1). This hot air heating furnace with a deodorizing furnace is harmful by introducing and burning in-furnace gas of a heating furnace 101 that heats the object to be treated with hot air and a combustible harmful gas that evaporates from the object to be treated by heating. A deodorizing furnace 102 that renders the gas harmless and a heat exchanger 103 that recovers the heat of the exhaust gas exhausted from the deodorizing furnace 102 and raises the temperature of the hot air supplied to the hot air heating furnace 101 are provided. The heating furnace 101 keeps the furnace temperature by introducing a part of the furnace gas to the heat exchanger 103 and exchanging heat with the deodorized gas discharged from the deodorization furnace 102 and then refluxing it again in the furnace 101. Is provided. On the other hand, the deodorization furnace 102 adjusts the introduction amount of the in-furnace gas from the heating furnace 101 based on the load amount of the workpiece to be introduced into the heating furnace 101, and heats the in-furnace gas with a burner. The internal temperature is provided so as to be maintained within a predetermined range.

  In this hot air heating furnace with a deodorizing furnace, the hot air temperature of the heating furnace 101 is adjusted by controlling the amount of air on the heat receiving side guided to the heat exchanger 103. That is, by bypassing a part of the furnace gas of the heating furnace 101 without using the bypass 104 without passing through the heat exchanger 103 and mixing with the furnace gas after the temperature is raised by heat exchange, the mixture is refluxed. The temperature is controlled by controlling the amount of heat exchange. At this time, since the exhaust gas from the deodorizing furnace 102 maintained at 750 ° C. or higher is introduced into the heat exchanger 103 as a heating side fluid for deodorization, a control amount (heat exchange) for reducing the heat receiving side air volume of the heat exchanger. The upper part of the gas in the furnace led to the heat exchanger 103 has a problem that it is vulnerable to fluctuations in the heat radiation side load because the upper limit is about 50% of the heat reception side air volume. Therefore, the deodorizing amount is reduced, and the turndown ratio is ensured by reducing the air volume on the heat radiation side of the heat exchanger 103. Specifically, the temperature corresponding to the load amount of the heating furnace 101. The first target value of the amount of gas introduced into the furnace 101 to the deodorizing furnace 102 is calculated and set by the detection signal (first control amount) of the detector T1, and this first target value is set as the hot air temperature. Detection signal of the corresponding temperature detector T2 (secondary control The secondary control amount that is the final control amount for the fan F1 is calculated and set.

JP-A-5-23533

  However, since the heat exchange type hot air generator performs heat exchange via a heat exchanger, it has disadvantages such as poor responsiveness to temperature changes and takes time to start up. In particular, PID control generally starts from about 50% to 60% of the target temperature value in order to prevent overshooting, but since the movement is slow, the valve is moved in response to disturbances, etc. Even so, the movement is slow, and even if you try to increase the air volume, you cannot increase it. However, if the PID value (temperature controller) is set to an extremely small value for on / off control, there is a problem of causing hunting that cannot converge to the set temperature. For example, when used as a hot air supply source in a coating drying furnace, the drying furnace takes a long time of about 50 minutes to 1 hour compared to the direct combustion type, or the disturbance response is low, so the drying furnace door is opened. When it closes, the heat escapes and it takes time to return to the original temperature, or it is easy to cause hunting even if you try to control it to a constant temperature. There is a problem that it is vulnerable to fluctuations in the load of the furnace.

  Also, in the heat exchange type hot air generator described in Patent Document 1, since the plurality of temperature control indicators TIC2 and TIC3 each have a control target (valve, inverter frequency), the control system becomes complicated and the equipment cost is increased. At the same time, there is a high possibility of mutual entanglement between the controls and hunting. In addition, although the amount of VOC (volatile organic odorous component) generated from the drying furnace must be deodorized, there is a situation where the air flow on the heat exchanger side of the heat exchanger must be reduced by inverter control. There is a problem that the deodorization amount fluctuates regardless of the load amount in the furnace. If the amount of deodorization decreases even though the load amount in the heating furnace increases, the VOC concentration in the furnace increases, and there is a risk that the lower explosion limit concentration may be reached. Furthermore, since the heat-receiving-side air volume can be reduced only to 50%, there is a problem that the heat-receiving-side air volume is vulnerable to heat radiation side load fluctuations (deodorization furnace load fluctuations).

  SUMMARY OF THE INVENTION An object of the present invention is to provide a heat exchange type hot air generator that has a simple structure, improves responsiveness, has no hunting, and quickly converges to a set temperature.

  In order to achieve such an object, the invention described in claim 1 includes a heat facility on the heat radiating side, a heat facility on the heat receiving side, and heat exchange with the exhaust gas from the heat radiating side heat facility, A heat exchanger for heating the heat receiving equipment side gas circulating between them, and a PID-controlled heat exchange hot air for maintaining the temperature of the heat receiving equipment side gas after the heat exchange raised in temperature by waste heat recovery at a set temperature In the generator, a first damper that is provided in a heat radiation side passage that allows the exhaust gas of the heat exchanger to pass through and controls an amount of passage of the exhaust gas, and an upstream side of the first damper in the heat radiation side passage; A bypass passage that communicates with the downstream side of the outlet of the heat exchanger to bypass the heat exchanger and flows the exhaust gas; and a first passage that opens and closes the bypass passage and controls the amount of exhaust gas that passes through the bypass passage. 2 dampers and the heat dissipation side flow path A third damper that allows outside air to be introduced into the heat radiation side flow path between the heat exchanger and the heat exchanger, and the temperature of the gas in the facility of the heat receiving side heat facility is measured by a temperature sensor, and A temperature controller for instructing an opening degree of the first to third dampers, a signal converter provided independently for each of the first damper, the second damper, and the third damper; The proportional band and the rotation angle center of each signal converter that controls the opening and closing of the second and third dampers close faster than the first damper that starts to open, but late for the first damper that starts to close. The proportional band and the rotation angle center that are set to open and the rotation angle center are set respectively, and the three dampers are set in advance according to an instruction from one temperature controller based on the temperature detected from one temperature sensor. To operate with To have.

The invention according to claim 2 is the heat exchange hot air generator according to claim 1, wherein the heat receiving side heat equipment is a drying furnace, the heat radiation side heat equipment is a direct combustion type deodorizing furnace, and the heat receiving side heat A heat exchanger for preheating for heating the gas in the drying furnace extracted from the drying furnace as the equipment and introduced into the direct combustion deodorization furnace with the deodorized exhaust gas from the direct combustion deodorization furnace is the heat radiation side heat equipment. wherein the bypass passage of the heat radiating side passageway provided upstream of branches, the furnace gas extracted from the drying furnace was raised at the preheating heat exchanger between the deodorizing furnace and the heat exchanger Then, after deodorizing by introducing into the direct combustion deodorization furnace, the deodorized exhaust gas from the deodorization furnace is sequentially passed through the preheating heat exchanger and the heat exchanger, and the preheating heat exchanger utilized as a heat source for heat exchange with the drying oven gas Both further is utilized as a heat source for heating the heat receiving equipment side gas circulating between the heat exchanger and the drying furnace.

  The invention according to claim 3 is the heat exchange hot air generator according to claim 1 or 2, wherein the proportional band of the second damper and the third damper is 75% or less, 25% or more, and The rotation angle center is preferably 37.5% or less and 12.5% or more.

The invention according to claim 4 is for heat exchange in the heat exchange hot air generator according to any one of claims 1 to 3 for detecting an outlet temperature of the heat radiation side flow path of the heat exchanger. A temperature sensor, a radiating side temperature controller that controls each of the signal converters based on a detection signal of the heat exchanger temperature sensor as a slave, a cascade connection using the drying furnace temperature controller as a master, and the drying Based on the instruction output from the drying furnace temperature controller based on the detection value of the temperature sensor of the furnace, the outlet temperature setting of the heat dissipation side flow path of the heat exchanger is calculated by the heat dissipation side temperature controller It is preferable that each signal converter is cascade-controlled so as to have the outlet set temperature.

Further, an invention according to claim 5, wherein, in the heat exchange type hot air generating device according to any one of claims 1 4, inverter fan downstream from the joining position between the bypass passage and the heat radiating side passageway And performing an inverter frequency control of the inverter fan in accordance with a temperature deviation between a set temperature of the heat receiving side heat facility and a gas temperature in the heat receiving side heat facility to reduce an air flow rate of the exhaust gas from the heat radiating side heat facility. It is preferable to implement the zone PID control to be controlled .

Furthermore, the invention described in claim 6 includes a fourth damper that enables introduction of outside air between the drying furnace and the heat exchanger on the outlet side of the heat receiving side flow path of the heat exchanger, It is preferable that the drying furnace is rapidly cooled by introducing outside air into the heat receiving side flow path during the deceleration operation when the set temperature of the heat receiving side heat equipment in the zone PID control is exceeded .

In the heat exchange type hot air generator according to claim 1, when the temperature of the circulating hot air is lowered, the opening degree of the first damper is closed and the second damper is opened to switch the exhaust gas to flow to the bypass flow path side. By opening the third damper and introducing outside air (fresh air) into the heat exchanger to remove residual heat remaining in the heat exchanger, the temperature of the gas flowing on the heat exchanger radiation side is rapidly cooled. In addition, when the temperature on the heat radiation side decreases (disturbance), the opening degree of the first damper is immediately opened and the opening degree of the second damper and the third damper are also rapidly closed and opened faster than the first damper. Close degree. At this time, the first damper that starts to open from the fully closed state has the same rotation angle as the second and third dampers that start to close from the fully open state even though the opening degree of the flow path does not change as the rotation angle changes. Even in the case of a change, the influence on the opening of the flow path is large, and since the proportional band and the rotation angle center are set small unlike the first damper, the influence of the opening change of the first damper is abruptly affected. give. Therefore, since the high temperature exhaust gas flows through the heat exchanger and heats the heat receiving equipment side gas circulating between the heat exchanger and the heat receiving side heat equipment, the temperature rises by heating, and thus it is possible to respond to a rapid temperature change. . That is, since the heat exchanger heat receiving side air volume is controlled, the disturbance responsiveness is high.
Further, it is a simple PID control system of one temperature controller and one temperature sensor, which makes control easy and does not cause hunting and quickly converges to a set temperature.

  In addition, according to the present invention, the passage of the exhaust gas can be controlled in the range of 0 to 100% with respect to the heat exchanger that exchanges heat between the exhaust gas and the circulating heat receiving equipment side gas, so that a high turn-down ratio can be obtained. .

In addition, since the invention according to claim 2 is used as a heat source of a combination of a drying furnace and a direct combustion type deodorizing furnace, even if there is a fluctuation in the airflow on the heat radiation side, the amount of exhaust gas to be bypassed is controlled. Heat exchange with the gas in the furnace extracted from the furnace can be made constant, and heat exchange that has been heated up by waste heat recovery without being affected by load-side load fluctuations (deodorization furnace load fluctuations) The temperature of the subsequent hot air can be maintained at the set temperature. Therefore, the furnace gas temperature in the drying furnace can be maintained at the set temperature while deodorizing the amount of VOC generated from the drying furnace. In this way, the VOC concentration in the drying furnace does not increase, and there is no possibility of reaching the lower explosion limit concentration, so that it is possible to safely perform a paint drying operation or the like.

  According to the third aspect of the present invention, the temperature change characteristics on the heat exchanger receiving side can be freely adjusted by changing the proportional band and the rotation angle center of each signal converter.

  According to the invention described in claim 4, cascade control is performed in which the control target (in-furnace temperature of the heat-receiving-side heat facility) is one and the temperature controller is suspended by the master and the slave, and the slave-side controller ( Since the heat release side temperature) adjusts the valve opening by itself, the disturbance converges quickly, the control system is simple, and the disturbance response can be improved. In this case, the temperature deviation in the furnace can be within ± 1 ° C.

  According to the invention described in claim 5, by the zone PID, acceleration operation is performed at the initial stage of startup, and when the temperature approaches the set temperature, the inverter frequency is controlled at the steady operation frequency, thereby increasing the heat exchange amount and shortening the startup time. Is possible. In the case of the present invention, the start-up which conventionally required 50 minutes to 60 minutes can be shortened from 35 minutes to 40 minutes. That is, the rise time can be shortened to about 2/3.

  According to the sixth aspect of the present invention, the amount of heat of the heat radiating equipment side gas (deodorized exhaust gas) is suppressed by controlling the inverter frequency of the inverter fan in the heat radiating side flow path at the time of overshoot, and the heat receiving heat that is returned to the heat receiving side heat equipment. By introducing fresh air directly into the facility-side gas and quenching it, overshoot can be suppressed and it has responsiveness to sudden disturbances.

It is an equipment flow block diagram showing one embodiment of a heat exchange type hot air generator of the present invention. It is a figure which expands and shows the principal part of the equipment flow block of FIG. It is a figure which shows an example of PID control of the heat exchange type | formula hot-air generator of this invention, and shows the relationship between a temperature controller, a signal converter, and a damper. It is a graph which shows the relationship between a damper opening degree and a control output. It is a graph which shows the change of the operation state by the zone PID at the time of starting, and furnace gas temperature. The other embodiment of this invention is shown, The equipment flow block diagram of the cascade control which made the drying side temperature controller the slave and the heat-radiation side temperature controller which makes constant the exit temperature of a heat exchanger under it as a master is shown. Show. It is a graph which shows the disturbance responsiveness which compared simple feedback control and cascade control. It is an equipment flow block diagram which shows the heat exchange type hot air generator of the conventional PID control.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  1 to 3 show an example of an embodiment in which the heat exchange type hot air generator of the present invention is applied as a heat source of a paint drying furnace with a deodorizing furnace. This deodorizing furnace-equipped coating drying furnace uses a drying furnace (heat receiving side heat equipment) 1, a direct combustion type deodorizing furnace (heat radiation side heat equipment) 2, and a deodorized gas (exhaust gas) discharged from the deodorizing furnace 2 as a heat source. A heat exchanger 3 that heats the drying furnace gas extracted from the drying furnace 1 and heats it back to the drying furnace 1, and performs heat exchange according to the temperature deviation of the furnace gas in the drying furnace 1. A PID-controlled heat exchange type hot air generator that holds the in-furnace gas temperature of the drying furnace 1 at a set temperature by controlling the air volume of the exhaust gas passing through the vessel 3 is configured. In the present embodiment, the in-furnace gas extracted from the drying furnace 1 is preheated using the waste heat of the deodorized exhaust gas in the preheating heat exchanger 4 and then introduced into the deodorization furnace 2. Reference numerals 6 and 7 in the figure are flow paths for flowing odor gas.

  The drying furnace 1 includes an in-furnace gas circulation system 21 that takes out the in-furnace gas outside the furnace, passes the heat-receiving side flow path of the heat exchanger 3 and then returns to the drying furnace 1 again. Part is extracted and led to the heat exchanger 3, heat-exchanged with the deodorized gas discharged from the deodorizing furnace 2 by the heat exchanger 3, heated, and returned to the drying furnace 1 as hot air to heat the object to be processed. I am doing so. In the figure, reference numeral 20 denotes a fan for circulating the gas in the furnace.

  On the other hand, the deodorizing furnace 2 mixes in-furnace gas (odor gas) extracted from the drying furnace 1 with a burner flame, and thermally decomposes an odor component, that is, VOC (volatile organic compound) in an atmosphere of at least 750 ° C. or more. It is a direct combustion type deodorization furnace, and the gas (deodorized gas) after the deodorization treatment by thermal decomposition is exhausted after exchanging heat with the in-furnace gas flowing through the in-furnace gas circulation system 21 through the heat exchanger 3. It is provided so that. The deodorizing furnace 2 is controlled so as to maintain the temperature in the deodorizing furnace at 750 ° C. by a temperature sensor or a temperature controller (not shown). In this embodiment, the deodorizing furnace 2 is provided with a fan 5 in the introduction path of the in-furnace gas from the drying furnace 1, and the odor gas is extracted and supplied from the drying furnace 1 with a constant air volume. On the other hand, in the furnace gas circulation path 21, the fan 20 is also controlled so that the furnace gas circulates between the drying furnace 1 and the heat exchanger 3 with a constant air flow. Reference numeral 26 in the figure denotes an outside air inlet for releasing the exhaust gas after heat exchange in the heat exchanger 3 to a lower temperature and releasing it into the atmosphere.

  Here, as shown in FIGS. 2 and 3, the heat exchange type hot air generator of the present embodiment communicates the upstream side and the downstream side of the heat exchanger 3 with the heat radiation side flow path 8 of the heat exchanger 3. Thus, a bypass path 9 is provided to flow the exhaust gas around the heat exchanger 3. Specifically, a bypass path 9 is provided that branches after the preheating heat exchanger 4 and upstream of the inlet side of the heat exchanger 3 and joins at the outlet side of the heat exchanger 3. A first damper 11 that controls the amount of exhaust gas flowing into the heat exchanger 3 by opening and closing the heat dissipation side flow path 8 in the heat dissipation side flow path 8 upstream of the heat exchanger 3, and the first damper 11 A third damper 13 that can introduce outside air into the heat radiation side flow path 8 between the heat exchanger 3 and the heat exchanger 3, and a second damper that opens and closes the bypass path 9 and controls the amount of exhaust gas that passes through the bypass path 9. And a damper 12. The first to third dampers 11, 12, 13 are provided with signal converters 15, 16, 17, respectively, so that the proportional band and the rotation angle center can be set independently, and the temperature controller 23. Is provided so that the damper opening is controlled. The temperature controller 23 determines the opening degree of each of the first to third dampers 11, 12, 13 based on the output signal of the temperature sensor 27 that detects the furnace temperature of the drying furnace 1, as signal converters 15, 16, 17. The hot air temperature is adjusted by driving each signal converter 15, 16, 17 in accordance with the detection signal of the temperature sensor 27, and the PID is set so that the furnace temperature of the drying furnace 1 is the same. It is something to control. That is, the PID control system according to the present embodiment sets the three signal converters 15, 16, and 17 in advance in accordance with instructions from one temperature controller 23 based on the temperature detected from one temperature sensor 27. And the opening / closing control of the corresponding first to third dampers 11, 12, 13 is performed at the rotation angle center.

  In the case of this embodiment, the setting of the opening / closing operation of each signal converter 15, 16, 17 is the second operation of opening / closing the bypass passage 9 with respect to the opening / closing operation of the first damper 11 that opens / closes the heat radiation side passage 8. The opening / closing operation of the third damper 13 for introducing outside air into the heat radiation side flow path 8 downstream of the damper 12 and the first damper 11 as required is set to have a reverse motion. Specifically, when the first damper 11 of the heat radiation side flow path 8 is 100% open (fully open), the second damper 12 of the bypass path 9 and the third damper 13 for introducing outside air are opened. The degree is 0% (fully closed). Conversely, when the first damper 11 is fully closed, the second and third dampers 12 and 13 are set to be fully opened.

  Furthermore, the setting of the proportional band and the rotation angle center of each signal converter 15, 16, and 17 is the second relative to the setting of the proportional band and the rotation angle center of the signal converter 15 that controls the opening and closing of the first damper 11. In addition, the proportional band and the rotation angle center of the signal converters 16 and 17 for controlling the opening and closing of the third dampers 12 and 13 are set differently. That is, by setting the opening degree of the damper (proportional band, rotation angle center) for each of the signal converters 15, 16, and 17, a time lag is given to the opening / closing timing of each damper and the speed of the opening / closing operation is changed. Can be given. In the present embodiment, the setting of the proportional band and the rotation angle center of the signal converters 16 and 17 that control the opening and closing of the second and third dampers 12 and 13 closes faster than the first damper 11 that starts to open. On the other hand, the proportional band and the rotation angle center are respectively set so as to have a relationship of starting to open slowly (a relationship having a delay time) with respect to the first damper 11 that starts to close. For example, the signal converter 15 that controls opening and closing of the first damper 11 is set to a proportional band of 100% and a rotation angle center of 50%, and the second and third signal converters 16 and 17 are set to the first damper. While the speed is closed earlier than 11, the proportional band setting and the rotation angle center setting are performed in a range where the proportional band is 75% or less and the rotation angle center is 37.5% or less so as to start opening slowly. Here, the lower limit values of the proportional band setting and the rotation angle center setting of the signal converters 16 and 17 are not particularly limited, but according to experiments by the present inventors, the proportional band 25% or more and the rotation angle center 12 are set. It is preferably 5% or more. Accordingly, the proportional band and the rotation angle center of the signal converters 16 and 17 of the second and third dampers 12 and 13 are set to the proportional band 25% to 75% and the rotation angle center 12.5% to 37.5%. It is preferable to carry out in the range. However, the setting of the proportional band and the rotation angle center of the signal converters 16 and 17 of the second and third dampers 12 and 13 is not limited to the above-described range, and can be appropriately set as necessary. Needless to say.

  Further, an inverter-controlled fan 10 is provided downstream of the position where the bypass path 9 of the heat radiation side flow path 8 joins, and is detected by the set temperature of the drying furnace 1 and the temperature sensor 27 when the drying furnace 1 is started up. It is preferable to perform zone PID control in which frequency control is performed in accordance with a temperature deviation from the temperature of the drying furnace to control the amount of induced air, that is, the amount of exhaust gas from the deodorizing furnace 2. In the zone PID control, for example, as shown in FIG. 5, the value of the PID is changed stepwise for each frequency band. Specifically, as the temperature deviation is larger, the air volume on the heat radiating side and the heat receiving side is increased, that is, the air volume is increased by frequency control of the fans 5 and 10 to increase the exchange heat quantity. For example, an acceleration operation range at 60 Hz is used until a temperature deviation of −20 ° C. with respect to the set temperature, and a range up to ± 5 ° C. is operated at 45 Hz as a steady operation range, and the deceleration operation exceeds the set temperature. In the region, the operation is at 40 Hz. This makes it possible to shorten the startup time. For example, it took about 50 to 60 minutes to start the drying furnace by the heat exchange type indirect heating method, but it was shortened to 35 to 40 minutes. In addition, when the temperature of the drying furnace is left open for a long time and the temperature inside the furnace decreases significantly, such as when a significant temperature decrease occurs due to external disturbances, the temperature changes rapidly. It is also possible to increase the responsiveness. In the deceleration operation region, the amount of heat exchanged is controlled by the frequency control of the fan 10 so as not to overshoot, and at the same time, the fourth damper 14 for taking in outside air is opened and the recirculation in the furnace after passing through the heat exchanger 3. It is preferable to accelerate the convergence to the set temperature by taking outside air (fresh air) into the gas and quenching it. The fourth damper 14 is an electric damper driven by an electric motor 18 and uses an external contact signal of the temperature controller 23 to open when a preset temperature is reached and introduce outside air from the intake port 19. By doing so, it is provided to start quenching.

  According to the heat exchange type hot air generator configured as described above, when the temperature of the circulating hot air is lowered, the opening of the first damper 11 is closed and the second damper 12 is opened to allow the exhaust gas to pass through. And the third damper 13 is opened and outside air (fresh air) is introduced into the heat exchanger 3 to remove the residual heat of the heat exchanger 3, so that the heat receiving side flow path of the heat exchanger 3 is removed. The temperature of the flowing furnace gas can be cooled without delay. Further, when the temperature on the heat radiation side decreases due to disturbance or the temperature in the furnace of the drying furnace 1 decreases, the opening of the first damper 11 is opened and the second damper 12 and the third damper 13 are opened. The opening degree is closed faster than the first damper 11, the amount of exhaust gas flow through the heat exchanger 3 can be increased, and the temperature of the in-furnace gas flowing through the heat receiving side flow path of the heat exchanger 3 can be raised. At this time, when the first damper 11 starts to open from the fully closed state, the change characteristics of the damper opening degree and the air volume are abrupt. Therefore, the change characteristics of the second and third dampers 12 and 13 are the first change characteristics. It is desirable to make it close to the change characteristic of the damper 11. Since the second and third dampers 12 and 13 are set such that the proportional band and the rotation angle center are smaller and narrower than the first damper 11, the influence of the change in the opening degree of the first damper 11 is abruptly affected. give. Therefore, since the high temperature exhaust gas flows through the heat exchanger 3 and the temperature in the furnace gas circulating between the heat exchanger 3 and the drying furnace 1 is increased by heating, the response to a rapid temperature change becomes possible. . That is, since the heat exchanger heat receiving side air volume is controlled, the disturbance responsiveness is high. Moreover, it is a simple PID control system of one temperature controller 23 and one temperature sensor 27, and the control is simple and the convergence to the set temperature is fast without hunting.

  Further, when the drying furnace 1 is started up, the first damper 11 is fully opened by the instruction from the temperature controller 23 based on the furnace temperature information from the temperature sensor 27, while the second and third dampers are opened. Zone PID control as shown in FIG. 5 is carried out while 12 and 13 are fully closed. By controlling the frequency of the fans 5 and 10 to control the amount of induced air, that is, the amount of exhaust gas from the deodorizing furnace 2, the amount of exchange heat can be reduced by increasing the amount of air on the heat radiating side and the heat receiving side according to the temperature deviation. In addition, the drying furnace will be started up. Specifically, for example, an acceleration operation range at 60 Hz is used until a temperature deviation of −20 ° C., and a range up to a temperature deviation of 5 ° C. is operated at 45 Hz as a steady operation range. Operation at 40 Hz is assumed. Thereby, it is possible to shorten the time by about 1/3 compared with the case of starting up with a constant air volume, and the starting up can be completed in 35 to 40 minutes. In addition, when the temperature of the drying furnace is left open for a long time and the temperature in the furnace decreases significantly, such as when a significant temperature decrease occurs due to external disturbances, the temperature changes rapidly in the same way. It is possible to increase the responsiveness. In the deceleration operation region, the amount of heat exchanged is controlled by the frequency control of the fan 10 so as not to overshoot, and at the same time, the fourth damper 14 for taking in outside air is opened and the recirculation in the furnace after passing through the heat exchanger 3. Convergence to the set temperature can be accelerated by taking outside air (fresh air) into the gas and quenching it.

In the case of the coating drying furnace of FIG. 1, for example, when the set temperature of the drying furnace 1 is set to 180 ° C., the odor gas is extracted at about 140 ° C. and is passed through the preheating heat exchanger 4 and the exhaust gas (750 ° C.). After being preheated to about 400 ° C. by heat exchange during the period, VOC (volatile organic odor component) is thermally decomposed by in-furnace combustion introduced directly into the combustion type deodorizing furnace 2 and maintained at 750 ° C. or higher. It is discharged toward the preheating heat exchanger 4. On the other hand, the in-furnace gas of about 160 ° C. extracted from the drying furnace 1 is heat- exchanged with the exhaust gas of about 556 ° C. through the preheating heat exchanger 4 in the heat exchanger 3 and introduced as necessary. The mixture is mixed with fresh air and heated to about 220 ° C. and then refluxed to the drying furnace 1.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the present embodiment, the first to third signal converters 15, 16, and 17 are directly driven by the temperature controller 23. However, the present invention is not limited to this example. As shown in FIG. 6, disturbance response may be further improved by cascading temperature controllers. That is, a heat exchanger temperature sensor 25 that detects the outlet temperature of the heat exchanger 3 and a heat radiation side temperature controller that controls the signal converters 15, 16, and 17 based on detection signals of the heat exchanger temperature sensor 25. 24, cascaded with the heat-radiating temperature controller 24 as a slave and the drying furnace temperature controller 23 as a master, and output from the drying furnace temperature controller 23 based on the detected value of the temperature sensor 27 of the drying furnace 1 On the basis of the instruction, the heat radiation side temperature controller 24 calculates the outlet set temperature of the heat exchanger 3, and the signal converters 15, 16, and 17 can be cascade-controlled so as to have the outlet set temperature. In this case, the drying furnace temperature controller (master) 23 outputs the output between 0% and 100% according to the change in the furnace gas temperature detected by the temperature sensor 27, and the heat radiation side temperature controller (slave) accordingly. ) 24 controls the signal converters 15, 16, and 17 to change the outlet temperature of the heat exchanger 3 in the range of 200 to 600 ° C., for example. Thereby, the temperature of the drying furnace is promptly corrected as shown by the solid line in FIG. In FIG. 7, the wavy line is simple feedback control, and the solid line is cascade control.

In the above-described embodiment, the odor gas extracted from the drying furnace 1 is preheated using the deodorized exhaust gas in the preheating heat exchanger 4 and then supplied to the deodorization furnace 2. The odor gas extracted from the drying furnace 1 is directly introduced into the deodorizing furnace 2, decomposed by direct combustion in the deodorizing furnace 2, led to the heat exchanger 3, and between the furnace gas extracted from the drying furnace 1 The heat may be exchanged and discharged.

  Further, in the present embodiment, the heat exchange type hot air generator as a heat source of the paint drying furnace with a deodorizing furnace has been mainly described as an example, but it is not particularly limited thereto, and the hot air after heat exchange It goes without saying that the present invention can be applied to a heat exchange type hot air generator capable of maintaining the temperature at a set temperature.

1 Drying furnace (heat receiving side heat equipment)
2 Direct combustion type deodorization furnace (heat radiation side heat equipment)
DESCRIPTION OF SYMBOLS 3 Heat exchanger 8 Heat radiation side flow path 9 Bypass flow path 10 Inverter fan 11 1st damper 12 2nd damper 13 3rd damper 14 4th damper 15 Signal converter 16 of 1st damper 16 2nd damper 17 Signal converter of the third damper 18 Signal converter of the fourth damper 20 Fan 21 Circulating flow path 23 Temperature controller (drying furnace temperature controller; master)
24 Temperature controller (heat-side temperature controller; slave)
25 Temperature sensor for heat exchange 27 Temperature sensor

Claims (6)

A heat exchanger that heats the heat receiving equipment side gas that circulates between the heat equipment on the heat radiating side, the heat equipment on the heat receiving side, and the exhaust gas from the heat radiating side heat equipment and circulates between the heat receiving side heat equipment. In a PID-controlled heat exchange type hot air generator that maintains the temperature of the heat receiving facility side gas after the heat exchange raised in temperature by waste heat recovery at a set temperature,
A first damper which is provided in a heat radiation side passage through which the exhaust gas of the heat exchanger passes and controls an amount of the exhaust gas passed;
A bypass passage for communicating the upstream side of the first damper of the heat dissipation side passage and the downstream side of the outlet of the heat exchanger to flow the exhaust gas around the heat exchanger;
A second damper that opens and closes the bypass path and controls the amount of exhaust gas passing through the bypass path;
A third damper that enables introduction of outside air into the heat dissipation side flow path between the first damper of the heat dissipation side flow path and the heat exchanger;
A temperature controller that measures the gas temperature in the facility of the heat receiving side heat facility with a temperature sensor and indicates the opening degree of the first to third dampers;
A signal converter provided independently for each of the first damper, the second damper, and the third damper;
The proportional band and the rotation angle center of each signal converter that controls the opening and closing of the second and third dampers close earlier than the first damper that starts to open, whereas the first damper that starts closing Is set to the proportional band and the rotation angle center that start to open slowly,
A heat exchange type hot air in which the three dampers are operated at a preset proportional band and rotation angle center in accordance with an instruction from one temperature controller based on a temperature detected from one temperature sensor. Generator. The heat receiving side heat equipment is a drying furnace, and the heat radiation side heat equipment is a direct combustion type deodorization furnace, and the gas in the drying furnace extracted from the drying furnace as the heat receiving side heat equipment and introduced into the direct combustion type deodorization furnace A heat exchanger for preheating for heating with deodorized exhaust gas from a direct combustion type deodorizing furnace branches the bypass path of the heat radiating side flow path between the deodorizing furnace as the heat radiating side heat equipment and the heat exchanger. provided upstream of the drying oven furnace gas extracted from the allowed to warm by the preheating heat exchanger after deodorized by introducing into the direct fired deodorizing furnace, pre deodorizing from the deodorizing furnace The exhaust gas is sequentially passed through the preheating heat exchanger and the heat exchanger to be used as a heat source for heat exchange with the drying furnace gas in the preheating heat exchanger, and further, the drying furnace and the heat The heat receiving equipment side gas circulating between the exchangers Heat exchange type hot air generating device according to claim 1, wherein is utilized as a heat source for heating the.   2. The proportional band of the second damper and the third damper is 75% or less and 25% or more, and the rotation angle center is 37.5% or less and 12.5% or more. Or the heat exchange type hot air generator of 2. A heat exchange temperature sensor that detects an outlet temperature of the heat dissipation side flow path of the heat exchanger, and a heat dissipation side temperature controller that controls each signal converter based on a detection signal of the heat exchange temperature sensor; As a slave, cascaded with the drying furnace temperature controller as a master, and based on an instruction output from the drying furnace temperature controller based on a detection value of the temperature sensor of the drying furnace, 4. The cascade control according to claim 1, wherein the outlet set temperature of the heat radiation side flow path of the heat exchanger is calculated and the respective signal converters are cascade-controlled so as to be the outlet set temperature. 5. The heat exchange type hot air generator described in 1. An inverter fan is installed downstream of the merging position of the heat radiation side flow path and the bypass path, and the inverter depends on a temperature deviation between a set temperature of the heat receiving side heat equipment and a gas temperature in the heat receiving side heat equipment. The heat exchange type hot air generator according to any one of claims 1 to 4, wherein zone PID control is performed to control an air flow rate of exhaust gas from the heat radiation side heat equipment by performing inverter frequency control of a fan . A fourth damper that enables introduction of outside air between the drying furnace on the outlet side of the heat-receiving-side flow path of the heat exchanger and the heat exchanger, and the heat-receiving-side heat facility of the zone PID control The heat exchange type hot air generator according to claim 5, wherein the drying furnace 1 is rapidly cooled by introducing outside air into the heat receiving side channel during a deceleration operation when the set temperature is exceeded.

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