JPH0525744Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention uses waste heat generated when exhaust gas exhausted from a paint drying furnace is passed through a deodorizing device and harmful malodorous substances in the exhaust gas are combusted and decomposed. This relates to an exhaust heat recovery device from a paint drying oven that uses a heat exchanger to recover
In particular, the present invention relates to an exhaust heat recovery device configured to use exhaust heat recovered by a heat exchanger to heat a chemical liquid or a degreasing liquid in a pretreatment device.

[Conventional technology]

Automotive painting pre-treatment equipment heats the chemical and degreasing liquids used to coat and degrease the surface of the metal to be painted to the required operating temperature (for example, around 50°C) through heat exchange with hot water. I'm trying to warm it up.

That is, a hot water tank for heating the chemical liquid and a hot water tank for heating the degreasing liquid are installed near the chemical conversion tank and the degreasing tank, which store the chemical liquid and degreasing liquid used for pre-treatment of painting, respectively. The chemical liquid in the chemical conversion tank and the degreasing liquid in the degreasing tank are circulated through each heat exchanger into which warm water is sent, respectively, and the chemical liquid and degreasing liquid are heated to the required operating temperature.

By the way, the inside of the baking drying oven for car paint is
The paint film is baked and dried by heating in a high-temperature atmosphere of 170°C to 180°C, and the exhaust gas containing harmful odor substances such as organic solvents, paint resins, and their curing agents that evaporate from the paint film is removed from the exhaust duct. Exhaust and
The exhaust gas is passed through a catalytic combustion type or direct combustion type deodorizing device installed in the exhaust duct to burn and decompose harmful malodorous substances in the exhaust gas, converting it into harmless and odorless deodorizing gas, and then releasing it to the outside.

The deodorizing gas after the harmful malodorous substances are burned and decomposed has a high temperature of 200°C to 300°C or higher.

Therefore, as shown in FIG. 2, the present applicant has developed a heat exchanger installed in an exhaust duct 1 to transfer high-temperature waste heat generated when harmful malodorous substances in the exhaust gas exhausted from a paint drying furnace are combusted and decomposed. Collected in vessels 2 and 2',
Conventionally, an exhaust heat recovery device has been employed which uses the recovered exhaust heat to heat the hot water in the chemical liquid heating hot water tank 3 and the degreasing liquid heating hot water tank 4.

That is, FIG. 2 is a flow sheet diagram showing a conventional exhaust heat recovery device, in which an exhaust duct 1 has a system in which exhaust gas exhausted from a paint drying furnace is passed through a deodorizing device 5 to burn and decompose harmful malodorous substances. Two heat exchangers 2 and 2' are installed adjacently on the upstream and downstream sides of the exhaust duct 1, and the upstream heat exchanger 2 collects the high-temperature waste heat generated when Outbound pipe 6 for collection
A hot water tank 3 for heating chemical liquid is connected through a and return pipe 6b, and a heat exchanger 2' on the downstream side is connected to a hot water tank 3 for heating degreasing liquid through an outgoing pipe 7a for exhaust heat recovery and a return pipe 7b. A hot water tank 4 is connected.

Then, the hot water in each hot water tank 3 and 4 is circulated and fed to the heat exchangers 2 and 2' by pumps 8 and 9 installed in outgoing pipes 6a and 7a, respectively, and heated with high-temperature waste heat. At the same time, hot water stored in the hot water tanks 3 and 4 is circulated and fed into heat exchangers 12 and 13 provided near the chemical conversion tank 10 and the degreasing tank 11, respectively. Further, the chemical liquid in the chemical conversion tank 10 and the degreasing liquid in the degreasing tank 11 are circulated and fed to each heat exchanger 12 and 13, and these chemical liquid and degreasing liquid are supplied to each heat exchanger from hot water tanks 3 and 4, respectively. The water is heated to the required operating temperature by heat exchange with hot water fed into the exchangers 12 and 13.

[Problems to be solved by the invention] However, in the conventional exhaust heat recovery device shown in FIG. 2, two heat exchangers 2 and 2' are provided in the exhaust duct 1, and 2', hot water tank 3 for heating chemical liquid, and hot water tank 4 for heating degreasing liquid.
There are an outgoing pipe 6a, a return pipe 6b, and an outgoing pipe 7a, respectively.
Since two systems of exhaust heat recovery piping consisting of the exhaust heat recovery pipe and the return pipe 7b are connected, there is a problem in that the equipment cost increases. In particular, in ordinary painting equipment, the heat exchanger 2 installed in the exhaust duct 1 of the paint drying oven,
Since the installation location of 2' and the installation locations of the hot water tanks 3 and 4 provided near the chemical conversion tank 10 and degreasing tank 11 of the pretreatment device are far apart, the cost of piping has increased significantly.

In addition, the hot water in the hot water tank 3 for heating the chemical liquid and the hot water tank 4 for heating the degreasing liquid are used at the same time and have almost the same operating temperature, but as shown in FIG. When two heat exchangers 2 and 2' are installed adjacently on the downstream side, the exhaust heat temperature recovered by the upstream heat exchanger 2 is high, but the temperature of the exhaust heat recovered by the downstream heat exchanger 2' is high. There is a problem in that the temperature of the recovered exhaust heat becomes low and the efficiency of exhaust heat recovery is poor.

Furthermore, in this case, when the temperature of the hot water heated by the upstream heat exchanger 2 becomes too high and it is desired to reduce the recovery of waste heat by the heat exchanger 2, exhaust air is removed from before the heat exchanger 2. Bypass pipe 1a of duct 1
When some of the waste heat is released through the heat exchanger 2', the temperature of the waste heat recovered from the heat exchanger 2' on the downstream side fluctuates, making it extremely difficult to control the temperature of the hot water heated by the heat exchanger 2'. There was a problem.

For this reason, the present applicant installed only a heat exchanger 2 connected to, for example, a hot water tank 3 for heating a chemical liquid in the exhaust duct 1, as shown in FIG. The exchanger 2' and the outgoing pipe 7a and return pipe 7b for exhaust heat recovery connected between the heat exchanger 2' and the hot water tank 4 for heating the degreasing liquid are omitted, and the exhaust heat is circulated to the heat exchanger 2. The hot water in the chemical liquid heating hot water tank 3 that has been fed and heated is circulated and fed to the heat exchanger 14 provided between the degreasing liquid heating hot water tank 4 and the degreasing liquid heating hot water tank 3. A new method for heating the hot water that is circulated from the hot water tank 4 to the heat exchanger 14 was experimentally attempted.

This method uses exhaust heat recovered by a heat exchanger 2 installed in an exhaust duct 1 to directly heat the hot water stored in one hot water tank 3, and then directly heats the hot water stored in one hot water tank 3.
Since the hot water stored in the tank is indirectly heated by heat exchange with the hot water in the hot water tank 3, there is only one long pipe system (outgoing pipe 6a and return pipe 6b) for exhaust heat recovery. is sufficient, and equipment costs are significantly reduced.
Another advantage is that the difficult temperature control of the hot water heated by the heat exchanger 2' disposed downstream of the heat exchanger 2, as in the conventional method, is not required.

However, on the other hand, the hot water stored in the chemical liquid heating hot water tank 3 and the degreasing liquid heating hot water tank 4 have almost the same operating temperature, and the temperature difference is very small. At the same time, the recovery efficiency of waste heat recovered from the hot water in the hot water tank 3 through the heat exchanger 14 to the hot water in the hot water tank 4 becomes very poor, and at the same time, the chemical liquid and degreasing stored in the chemical converting tank 10 and the degreasing tank 11 When the temperature of the hot water stored in the hot water tanks 3 and 4 changes in response to changes in the heat load of the liquid, the hot water in the hot water tank 4 to be heated by heat exchange with the hot water in the hot water tank 3. The temperature of the hot water becomes higher than that of the hot water in the hot water tank 3, resulting in a problem that heat cannot be recovered.

[Means for solving problems]

Therefore, the present invention is capable of efficiently recovering waste heat to effectively heat hot water for heating chemical liquids and hot water for heating degreasing liquids, has low equipment costs, and can reach difficult temperatures for each hot water heated by waste heat. The purpose is to provide an exhaust heat recovery device that does not require any control.

In order to achieve this objective, the present invention uses a heat exchanger to recover the waste heat generated when the exhaust gas exhausted from the paint drying oven is passed through a deodorizing device and the harmful malodorous substances in the exhaust gas are combusted and decomposed. In the exhaust heat recovery device from the paint drying furnace, which is used for heating hot water stored in a hot water tank for heating a chemical liquid and a hot water tank for heating a degreasing liquid in a pretreatment device, the hot water tank Hot water stored in one of the tanks is circulated and fed to the heat exchanger through an outgoing pipe and a return pipe for exhaust heat recovery, and through an outgoing pipe and a return pipe for hot water circulation connected between the two hot water tanks. A control means configured to circulate hot water between the two hot water tanks, and controlling the amount of hot water circulated and fed through the hot water circulation outgoing and return pipes to maintain a constant water level in the two hot water tanks. It is characterized by having the following.

[Effect]

According to the present invention, exhaust heat is recovered by circulating only the hot water stored in either the hot water tank for heating the chemical liquid or the hot water tank for heating the degreasing liquid to the heat exchanger. Therefore, only one outgoing pipe and one return pipe for exhaust heat recovery are connected between the heat exchanger and the hot water tank, and the equipment cost is significantly reduced.

In addition, outgoing and return pipes for hot water circulation are connected between one hot water tank that circulates hot water to the heat exchanger and the other hot water tank, so that hot water is directly circulated between both hot water tanks. Therefore, the recovery efficiency of waste heat is very high.
The hot water in both hot water tanks is effectively heated.

In addition, since the operation of the hot water circulation pump installed in the outgoing and return pipes for hot water circulation is controlled to maintain the water level in both hot water tanks constant, the hot water circulated between both hot water tanks. There is no risk of hot water overflowing from one hot water tank due to water level fluctuations and causing heat loss.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described based on the drawings.

FIG. 1 is a flow sheet diagram showing an example of the exhaust heat recovery device according to the present invention.

Note that parts common to FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this example, exhaust heat is provided between a heat exchanger 2 installed in an exhaust duct 1 and a chemical liquid heating hot water tank 3 to circulate hot water in the hot water tank 3 to the heat exchanger 2. The outgoing pipe 6a and return pipe 6b for recovery are connected, and hot water is circulated between the hot water tank 3 for heating the chemical liquid and the hot water tank 4 for heating the degreasing liquid. Outgoing pipe 15a and return pipe 15b for hot water circulation
is connected.

Hot water circulation pumps 16a and 16b are installed in the outgoing pipe 15a and the return pipe 15b, respectively.
The operation of each of the pumps 16a and 16b is controlled to maintain the water level in both hot water tanks 3 and 4 constant based on detection signals from liquid level gauges 17a and 17b that detect the water levels in the hot water tanks 3 and 4. has been done.

In addition, the hot water stored in the hot water tank 3 for heating the chemical liquid is circulated and fed to the heat exchanger 12 via the outgoing pipe 18a and the return pipe 18b for hot water circulation, and is fed into the hot water tank 4 for heating the degreasing liquid. The hot water stored in is configured to be circulated and fed to the heat exchanger 13 via an outgoing pipe 19a and a return pipe 19b for hot water circulation.

Then, the chemical liquid stored in the chemical conversion tank 10 is circulated and fed to the heat exchanger 12 via the outgoing pipe 20a and return pipe 20b for chemical liquid circulation, and the heat exchanger 12
The degreasing tank 11 is heated to the working temperature by heat exchange with the hot water in the hot water tank 3 which is circulated to the degreasing tank 11.
The degreasing liquid stored in the outgoing pipe 21 for circulating the degreasing liquid
a and the return pipe 21b to the heat exchanger 13, and is heated to the operating temperature by heat exchange with the hot water in the hot water tank 4, which is circulated to the heat exchanger 13. has been made.

Note that the suction port of the hot water circulation pump 16a installed in the hot water circulation outgoing pipe 15a is opened close to the open end of the exhaust heat recovery return pipe 6b connected to the chemical liquid heating hot water tank 3. , and a return pipe 15b for hot water circulation.
The suction port of the hot water circulation pump 16b installed in the hot water circulation pump 16b is opened close to the open end of the return pipe 19b for hot water circulation connected to the hot water tank 4 for heating the degreasing liquid.

Then, the exhaust gas exhausted from the paint drying oven at a displacement of 130Nm ³ /min is passed through the deodorizing device 5 to burn and decompose the harmful malodorous substances in the exhaust gas and produce a high-temperature (190°C to 260°C) deodorizing gas. A heat exchanger 2 with an exhaust heat recovery calorific value of 150000 Kcal/h is installed in the exhaust duct 1 to be generated, and the chemical liquid is passed through the exhaust heat recovery outgoing pipe 6a into the heat exchanger 2 at a flow rate of 125/min. Warm water in heating water tank 3 (50℃;
375,000 Kcal/h) and heated hot water (70°C;
525000 Kcal/h) is refluxed into the chemical liquid heating hot water tank 3 through the exhaust heat recovery return pipe 6b, and the hot water in the hot water tank 3 is heated to 55°C. That is, the exhaust heat recovered from the heat exchanger 2 (supplied heat amount:
150000Kcal/h) to maintain the temperature of the hot water in the hot water tank 3 at 50°C to 55°C.

At the same time, hot water (55°C; 825,000 Kcal/h) in the hot water tank 3 is fed into the hot water tank 4 for heating the degreasing liquid at a flow rate of 250/min through the outgoing pipe 15a for hot water circulation. The same amount of hot water (50°C;
750000 Kcal/h) is refluxed into the chemical liquid heating hot water tank 3. As a result, the chemical liquid heating hot water tank 3
The amount of heat supplied from inside to the hot water tank 4 for heating the degreasing liquid is 75000 Kcal/h, which is equivalent to 1/2 of the amount of heat supplied from the heat exchanger 2 to the hot water tank 3 for heating the chemical liquid. The temperature of the hot water in the hot water tank 4 for warming the degreasing liquid is also always maintained at 50°C to 55°C.

The hot water stored in these hot water tanks 3 and 4 is circulated and fed to the heat exchangers 12 and 13, respectively, and is circulated from the chemical conversion tank 10 and the degreasing tank 11 to the heat exchangers 12 and 13, respectively. The supplied chemical liquid and degreasing liquid are heated to the required operating temperature of approximately 50°C.

In this way, according to this embodiment, the exhaust duct 1
Only one heat exchanger 2 is installed in the system, and only the hot water in the chemical liquid heating hot water tank 3 is circulated and fed to the heat exchanger 2. Therefore, one system is used as exhaust heat recovery piping. It is sufficient to provide only the outgoing pipe 6a and the return pipe 6b, and the equipment cost is significantly reduced.

In addition, an outgoing pipe 15a and a return pipe 15b for hot water circulation are provided between the chemical liquid heating hot water tank 3 that heats hot water using the exhaust heat recovered from the heat exchanger 2 and the degreasing liquid heating hot water tank 4. are connected so that hot water is directly circulated between the hot water tanks 3 and 4.
The recovery efficiency of waste heat is very good, and both hot water tanks 3
The hot water in and 4 is effectively heated.

In particular, the suction port of the hot water circulation pump 16a, which is installed in the hot water circulation outgoing pipe 15a that sends the hot water in the hot water tank 3 into the hot water tank 4, reaches a high temperature (70°C) due to the exhaust heat recovered from the heat exchanger 2. Hot water heated to hot water tank 3
If the opening is close to the open end of the exhaust heat recovery return pipe 6b, the relatively high-temperature hot water in the hot water tank 3 is sent into the hot water tank 4, and the hot water in the hot water tank is The hot water inside 4 is heated more effectively. In addition, the suction port of the hot water circulation pump 16b interposed in the return pipe 15b for hot water circulation that returns the hot water in the hot water tank 4 to the hot water tank 3 is provided for heat exchange with the degreasing liquid in the degreasing tank 11. When the opening is close to the open end of the return pipe 19b for hot water circulation that recirculates low-temperature hot water, relatively low-temperature hot water in the hot water tank 4 is sent back into the hot water tank 3, and the hot water is returned to the hot water tank. 4
The temperature drop inside is suppressed. Therefore, the temperatures of the hot water stored in both hot water tanks 3 and 4 can be reliably maintained at substantially the same temperature.

Also, an outgoing pipe 15a and a return pipe 15b for hot water circulation.
Each hot water circulation pump 16a and 16b installed in
The circulating water volumes are set to be the same (250/min), but if the water volumes are even slightly different, the water levels of hot water in hot water tanks 3 and 4 will change significantly over time. However, there is a risk that hot water will overflow from one of the hot water tanks, causing heat loss. However, according to the present invention, the operation of the hot water circulation pumps 16a and 16b is controlled to maintain the water level in the hot water tanks 3 and 4 constant, for example,
When the water level in the hot water tank 4 falls by more than a certain level and the water level in the hot water tank 4 rises by more than a certain level, the water level change will be reflected in each hot water tank 3.
and 4, and the operation of the hot water circulation pump 16a installed in the hot water circulation outgoing pipe 15a is temporarily stopped by the detection signals from the liquid level gauges 17a and 17b. be done. As a result, the supply of hot water from the hot water tank 3 to the hot water tank 4 is stopped, and the water level in the hot water tank 3 starts to rise, and the water level in the hot water tank 4 starts to fall, causing both the hot water tanks 3 and When the water level in the hot water circulation pump 16a has recovered to a certain level, the operation of the hot water circulation pump 16a is restarted in response to a detection signal from the liquid level gauges 17a and 17b that detect this. Therefore, according to the present invention, water level fluctuations occur in the hot water tank 3 for heating the chemical liquid and the hot water tank 4 for heating the degreasing liquid, which circulate hot water to each other, and hot water overflows from one of the hot water tanks. There is no such problem.

In the embodiment, the case where the exhaust heat recovery pipe (the outgoing pipe 6a and the return pipe 6b) is connected between the heat exchanger 2 and the hot water tank 3 for heating the chemical solution is described.
The present invention is not limited to this, and a pipe for recovering exhaust heat may be connected between the heat exchanger 2 and the hot water tank 4 for heating the degreasing liquid.

[Effect of idea]

As described above, according to the present invention, the waste heat is removed from the two systems in which the hot water tank for heating the chemical liquid and the hot water tank for heating the degreasing liquid are connected to the heat exchanger for recovering the waste heat. Since only one system of recovery piping is sufficient, the cost of equipment for providing very long piping can be significantly reduced.

Further, between the hot water tank for heating the chemical liquid and the hot water tank for heating the degreasing liquid, outgoing pipes and return pipes for hot water circulation are connected to circulate hot water between the two hot water tanks. Therefore, the waste heat recovery efficiency is very high, and the hot water in both hot water tanks is effectively heated. Furthermore, the operation of the hot water circulation pumps installed in the outgoing and return pipes for hot water circulation is controlled to maintain a constant water level in the hot water tank for heating the chemical liquid and the hot water tank for heating the degreasing liquid. Therefore, there is a variety of excellent effects in that there is no risk of hot water overflowing from one of the hot water tanks and causing heat loss due to fluctuations in the water level of the hot water circulated between the two hot water tanks.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet diagram showing an example of the waste heat recovery device according to the present invention, Fig. 2 is a flow sheet diagram showing a conventional waste heat recovery device, and Fig. 3 is an experimental fabrication diagram showing a comparison with the present invention. It is a flow sheet diagram of the exhaust heat recovery device. Explanation of symbols, 1... Exhaust duct, 2... Heat exchanger, 3... Hot water tank for heating chemical liquid, 4... Hot water tank for heating degreasing liquid, 5... Deodorizing device, 6a... Exhaust heat Outgoing pipe for recovery, 6b... Return pipe for exhaust heat recovery, 10...
Chemical conversion tank, 11... Degreasing tank, 15a... Outgoing pipe for hot water circulation, 15b... Return pipe for hot water circulation, 16a,
16b... Hot water circulation pump, 17a, 17b...
Liquid level indicator.

Claims (1)

[Scope of Claim for Utility Model Registration] [1] Exhaust gas discharged from a paint drying oven is passed through a deodorizing device 5, and the exhaust heat generated when harmful malodorous substances in the exhaust gas are combusted and decomposed is transferred to a heat exchanger 2.
Exhaust heat recovery device from a paint drying furnace is used to heat the hot water stored in the chemical liquid heating hot water tank 3 and the degreasing liquid heating hot water tank 4 of the pretreatment equipment. In, the hot water tanks 3, 4
The hot water stored in one side of the pipe 6 is used for exhaust heat recovery.
An outgoing pipe 15a and a return pipe 15 for circulating hot water are connected between the hot water tanks 3 and 4 and are circulated to the heat exchanger 2 through the hot water tanks 3 and 4.
Hot water is circulated between the two hot water tanks 3 and 4 through the hot water circulation outgoing pipe 15.
An exhaust heat recovery device characterized by comprising a control means for maintaining the water levels in both the hot water tanks 3 and 4 constant by controlling the amount of hot water circulated through the hot water tanks 3 and 4. [2] The control means includes hot water circulation pumps 16a and 16b interposed in the hot water circulation outgoing pipe 15a and return pipe 15b, and a liquid level gauge 17a that detects the water level in the hot water tanks 3 and 4. 17b, and is configured to adjust the feed rate of the pumps 16a, 16b based on detection signals from the liquid level gauges 17a, 17b, according to claim 1 of the utility model registration claim. .