JPH01299675A - Operating method for drier - Google Patents

Abstract

PURPOSE:To reduce the time from the start-up of a drier to its normal operation by forming a closed circuit for circulating hot air in the exhaust system, and heating a catalyst to a specified treating temp. by the hot air circulating in the closed circuit. CONSTITUTION:The drier 8 is started up, and the atmosphere in a drying furnace 1 is heated to a specified temp. In this case, the closed circuit H for circulating the hot air mixed with the combustion gas of a catalyst heating burner 10 is formed in the exhaust system 7. The catalyst 9 is heated to a specified treating temp. by the hot air circulating in the circuit H. Concretely, when the atmosphere in the drying furnace 1 is heated to 170-180 deg.C at the start-up of the drier, the combustion amt. of the burner 3 provided in the hot air circulating path N and the output of a hot air circulating fan 5 are increased as compared with those in the normal operation, and an enormous volume of the hot air at >=200 deg.C is circulated and supplied into the drying furnace 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention supplies exhaust gas generated in various drying ovens such as paint baking drying ovens to a catalytic combustion type deodorizing device installed in the exhaust system. The present invention relates to a method of operating a drying device for deodorizing and purifying treatment.

[Conventional technology]

As shown in FIG. 2, this type of drying apparatus includes a hot air circulation path N formed in a paint baking drying oven 1 for baking a coating film electrodeposited on the surface of an object W to be painted, such as an automobile body, for example. The hot air circulation path N includes a burner 3 that heats the air in the drying oven l sucked from the return duct 2 to a predetermined operating temperature, and the air heated by the burner 3 is returned to the drying oven l through the supply duct 4. A hot air circulation fan 5 is interposed to introduce hot air into the air.

Further, the drying oven L is provided with an exhaust system 7 that uses an exhaust fan 6 to exhaust exhaust gas containing harmful malodorous substances that evaporate from the coating film of the object W to be coated. A deodorizing device 8 is installed, which includes a catalyst 9 that burns and decomposes malodorous substances, and a catalyst heating burner 10 that heats the catalyst 9 to a predetermined processing temperature.

By the way, at the start of operation of this drying apparatus, the temperature of the atmosphere inside the drying oven 1 is raised to a baking temperature of 170° C.-180° C. by the hot air circulated and supplied from the hot air circulation path N.
After waiting for the catalyst 9 of the deodorizing device 8 to be heated to a processing temperature of 300°C to 450°C by the catalyst heating burner 1O, the workpiece W to be coated is started to be carried into the drying oven 1. It is said that

This is because if the atmospheric temperature inside the drying oven 1 is too low, there is a risk of poor baking of the coating film, and if the processing temperature of the catalyst 9 is too low, the decomposition ability of the catalyst 9 may not be fully demonstrated. Alternatively, foreign matter caused by incomplete combustion of harmful malodorous substances contained in the exhaust gas may adhere to and deposit on the catalyst layer, causing damage and impairing the durability of the expensive catalyst 9.

[Problem to be solved by the invention]

For this reason, in the past, it took a long time from the start of the drying device until the workpiece W to be coated could be carried into the drying oven 1, and the problem was that the entire coating line could not be started up quickly. was there.

In particular, the burner lO for catalyst heating is
The temperature of the exhaust gas fed from the inside to the deodorizing device 8 is high, the processing air volume of the catalyst 9 that burns and decomposes the gas components is small, or the reaction heat of the catalyst 9 becomes abnormally large, causing a restriction. Considering that the catalyst performance will deteriorate if the temperature exceeds that temperature, a small burner with a small combustion amount is used. This was significantly longer than the warm-up time, which caused a significant delay in starting up the coating line.

In other words, when the temperature inside the drying oven 1 is rising, the amount of combustion of the burner 3 interposed in the hot air circulation path N and the amount of combustion of the hot air circulation fan 4 are determined.
By increasing the amount of air blown than during constant operation,
As shown in the graph in Figure 3, it is relatively short (30 minutes ~
Although the required baking temperature was reached in 90 minutes), the catalyst 9 of the deodorizing device 8 did not reach the predetermined processing temperature until 30 minutes or more had passed after the completion of temperature rise in the drying oven 1.

In the past, a drying device (Utility Model Application No. 61-98576,
(Refer to Japanese Utility Model Application No. 62-1113582) and a drying device in which a deodorizing device 8 is interposed in the hot air circulation path N (Refer to Japanese Utility Model Application No. 62-1113582).
-44277.

There is also a drying method (see Japanese Utility Model Application No. 61-87574), but in these, the temperature rising time in the drying oven I was longer than that of the drying apparatus shown in FIG.

That is, not only during the constant operation of the drying oven 1 (but also when the temperature is rising and the object to be coated W is not carried in), combustible exhaust gas is not sent to the catalyst 9 of the deodorizing device 8, so the drying oven 1 is The hot air sent into the interior cannot be heated to a high temperature using the reaction heat of the catalyst 9, and is heated only by the combustion heat of a small catalyst heating burner lO provided to heat the catalyst 9. Therefore, it took a long time to raise the temperature inside the drying furnace 1.In addition, if the combustion amount of the burner 10 is increased, the temperature raising time inside the drying furnace 1 can be shortened, but in this case, the catalyst 9 Performance deteriorates due to overheating, resulting in a significant decrease in durability.

Therefore, even if the catalyst heating burner 10 is small, the present invention aims to significantly shorten the start-up time from when the drying device starts until it can shift to constant operation. The objective is to be able to quickly heat the catalyst 9 to a predetermined processing temperature with good thermal efficiency without deteriorating its performance.

[Means to solve the problem]

In order to achieve this object, the present invention provides a deodorizing system having a catalyst for burning and decomposing harmful malodorous substances in the exhaust gas and a catalyst heating burner for heating the catalyst in an exhaust system that discharges the exhaust gas generated in the drying furnace. In the method of operating a drying device in which the drying device is installed, when the drying device is started and the temperature is increased to heat the atmosphere inside the drying furnace to a required temperature, the exhaust system is heated by combustion gas from the catalyst heating burner. A closed circuit is formed in which hot air circulates, and the catalyst is heated to a predetermined processing temperature by the hot air circulating in the closed circuit.

[Effect]

According to the method of the present invention, the hot air that circulates in the closed circuit formed in the exhaust system and is heated by the catalyst heating burner receives heat repeatedly and is heated to a high temperature in a short time with high thermal efficiency. The catalyst heated by the hot air also reaches the predetermined processing temperature in a short time.

This makes it possible to quickly raise the temperature of the catalyst on its own in accordance with the temperature rise time in the drying oven and independently from the temperature rise in the drying oven, so the drying equipment can be started and operated constantly. The start-up time until the transition to the next stage is significantly shortened, and at the same time, performance deterioration due to overheating of the catalyst is also prevented.

(Example) Hereinafter, an example of the present invention will be specifically described based on the drawings.

FIG. 1 is a flow sheet diagram of a drying apparatus showing an example of the method of the present invention.

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

In the present invention, when the drying device is started and the atmosphere inside the drying furnace 1 is heated to a required temperature, the exhaust system 7 is closed so that hot air mixed with combustion gas from the catalyst heating burner IO circulates. A circuit H is formed, and hot air circulating within the closed circuit H heats the catalyst 9 to a predetermined processing temperature.

Here, the closed circuit H includes an upstream duct 7a of an exhaust system 7 that supplies exhaust gas generated in the drying furnace 1 to a deodorizing device 8, and a high-temperature processed gas that has been deodorized and purified by a catalyst 9 of the deodorizing device 8. The downstream duct 7b that discharges the
The bypass duct 7c is connected between the bypass duct 7a and the bypass duct 7b.

That is, in the exhaust system 7, an automatic damper 11 is installed upstream of the connection between the upstream duct 7a and the bypass duct 7c, and the automatic damper 11 is installed between the downstream duct 7b and the bypass duct 7.
An automatic damper 12 is interposed downstream of the connection part of C,
Further, an automatic damper 13 is also installed in the bypass duct 7c.

Then, when starting the drying equipment, the automatic damper 1
1 and 12 are closed, the automatic damper 13 is opened,
A closed circuit H is formed from the upstream duct 1-7a with the exhaust fan 6 interposed therein, through the deodorizing device 8, the downstream duct 7b, the bypass duct 7c, and back to the upstream duct 7a.

Furthermore, a heat exchanger 14 is interposed between the upstream duct 7a and the downstream duct 7b, and the heat exchanger 14 is used to supply heat from inside the drying furnace 1 to the deodorizing device 8 through the upstream duct 7a during constant operation of the drying device. The exhaust gas is preheated by heat exchange with high-temperature processing gas sent from the deodorizing device 8 to the heat exchanger 14 through the downstream duct 7b.

Note that 15 is a blower that supplies combustion air to the catalyst heating burner lO.

Therefore, when starting the drying device and heating the atmosphere inside the drying furnace l to a predetermined baking temperature (170°C to 180°C), the burner 3 installed in the hot air circulation path N is heated. The amount of combustion and the amount of air blown by the hot air circulation fan 5 are increased compared to those during constant operation to circulate and supply a large amount of hot air of 200°C or more into the drying oven 1, thereby raising the temperature of the atmosphere inside the drying oven 1 in a short time. .

In parallel with this, the automatic dampers 11 and 12 installed on the upstream and downstream sides of the exhaust system 7 are closed, and the automatic damper 13 installed on the bypass duct 7c is opened, and the exhaust system At the same time, a burner 10 for heating the catalyst of the deodorizing device 8 installed in the closed circuit H is formed in the closed circuit H.
The hot air mixed with the combustion gas of the burner IO and heated is circulated by the exhaust fan 6.

As a result, the hot air circulating in the closed circuit H is mixed with the combustion gas of the catalyst heat burner 10 and is directly added to the mixture.

At the same time, the heat exchanger 1 is heated by the burner lO.
It is indirectly heated by heat exchange with the hot air sent into the air tank 4, and is heated to a high temperature in a short time with good thermal efficiency by receiving heat repeatedly.

Therefore, the catalyst 9 heated by the hot air circulating in the closed circuit H reaches the predetermined processing temperature in a very short time, and the temperature of the catalyst 9 is rapidly raised in accordance with the temperature rise time in the drying oven l. As a result, the start-up time of the drying device is significantly shortened. Further, the catalyst 9 is in a drying oven l.
Since the temperature is raised separately from the internal temperature rise, it is possible to prevent performance deterioration due to overheating.

Note that while hot air is being circulated in the closed circuit H, the automatic damper 12 installed on the downstream side of the exhaust system 7 is not fully closed, and the air is supplied from the blower 15 to the catalyst heating burner °10. Leave it slightly open so that the same amount of hot air as the combustion air being used can be exhausted.

In this way, when the atmosphere in the drying oven 1 reaches the predetermined baking temperature of 170°C to 180°C, and the catalyst 9 also reaches the predetermined processing temperature of 300°C to 350°C, the heating is completed. , the combustion amount of the burner 3 installed in the hot air circulation path N and the air blowing amount of the hot air circulation fan 5 are reduced, and from then on, control is left to the temperature fluctuations in the drying oven 1, and the upstream of the exhaust system 7 is The automatic dampers 11 and 12 installed on the side and the downstream side are fully opened, the automatic damper 13 installed on the bypass duct 7C is fully closed, the closed circuit H is released, and the air inside the drying oven 1 is discharged from the exhaust fan 6. The object W to be coated is then sucked out and fed to the deodorizing device 8, and then the object W to be coated is started to be carried into the drying oven 1.

As a result, the paint film of the workpiece W carried into the drying oven 1 is baked at a predetermined temperature, and exhaust gas containing harmful malodorous substances that evaporate from the paint film is introduced into the exhaust system 7. The gas components are sent to the deodorizing device 8 and are effectively combusted and decomposed by the catalyst 9 heated to a predetermined processing temperature.

According to the method of the present invention, the exhaust system 7 is blocked by the closed circuit H when the temperature inside the drying oven 1 is raised, but the workpiece W to be coated is carried into the drying oven 1 when the temperature is rising. Since no harmful malodorous substances are generated, there is no risk of contaminating the surrounding environment even if the inside of the drying oven 1 is not evacuated.

〔Effect of the invention〕

As described above, according to the present invention, when the drying device is started and the atmosphere inside the drying furnace is heated to a required temperature, the exhaust system in which the deodorizing device is installed is heated by the catalyst heating burner. A closed circuit is formed in which the heated air circulates.
Since the catalyst is heated by the hot air circulating in the closed circuit, the heating time for heating the catalyst to the predetermined processing temperature is significantly shorter than in the past, and the drying equipment can be started up and maintained at a constant temperature. This has the very excellent effect of significantly shortening the start-up time before shifting to operation, and at the same time preventing deterioration of catalyst performance.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet diagram of a drying apparatus showing an example of the method of the present invention, FIG. 2 is a flow sheet diagram of a drying apparatus showing a conventional method, and FIG. 3 is a graph showing problems of the conventional method. Explanation of symbols ■ - Drying oven, N - Hot air circulation path, 6 - Exhaust fan, 7 - Exhaust system, 8 - Deodorizing device, 9 - Catalyst, 10 -
-Catalyst heating burner, H...-Closed circuit, 11...-Automatic damper, 12--Automatic damper, 13--Automatic damper. Figure 1 Base 8 Ancestors 94 4 10 Figure 3

Claims (1)

[Claims] In a method for operating a drying device in which a deodorizing device having a catalyst for burning and decomposing harmful malodorous substances in the exhaust gas and a catalyst heating burner for heating the catalyst is interposed in an exhaust system for discharging exhaust gas generated in a drying furnace. , at the time of heating up the drying equipment and heating the atmosphere inside the drying oven to the required temperature,
A closed circuit is formed in the exhaust system in which hot air heated by the combustion gas of the catalyst heating burner circulates, and the catalyst is heated to a predetermined processing temperature by the hot air circulating in the closed circuit. How to operate the drying equipment.