JPH0810679A - Coating drying device - Google Patents

Abstract

PURPOSE:To reduce equipment cost by miniaturizing a heat medium oil heating boiler which serves as a heat source for a hot blast circulation type tunnel furnace of a heat medium oil indirect heating system to such an extent that a furnace interior is maintained at an actual use temperature, and at the same time, enable even a small-sized heating boiler to increase an intra-furnace temperature to the actual use temperature in a time almost equivalent to that required for heating by a conventional heating boiler. CONSTITUTION:Heat medium oil circulation piping 12 which feeds by circulation a heat medium oil heated by the heat discharged by a power generation device 16 which generates an electric power as an emergency power supply for coating facilities, is connected to a heat exchanger 8 interposed in a hot blast circulation passage 11 for feeding a hot blast by circulation into a tunnel furnace 3. In addition, closable doors 4, 4 which block the inlet and outlet 2, 2 of the tunnel furnace 3 when a coating drying device stops are formed at the inlet and outlet 2, 2. Further, in the hot blast circulation passage 11, a bypass 18 with an interposed heat retaining fan 17 for blowing an air heated by the hat released by the heat exchanger 8 when the coating drying device stops, is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating dryer using a hot air circulation type tunnel furnace for drying coating films on automobile bodies or the like which are continuously conveyed by a conveyor.

[0002]

2. Description of the Related Art For example, in a tunnel furnace of a coating dryer for drying a coating film on an automobile body, hot air sucked through a return duct from inside the furnace is heated to a working temperature and introduced into the furnace again from a supply duct. A hot air circulation path is formed. Then, due to the difference in the heat source that heats the hot air to the operating temperature, the high-temperature heat medium oil is supplied to the heat exchanger interposed in the hot air circulation path, and the heat medium is indirectly heated by the heat exchanger. Method, a combustion gas indirect heating method in which high-temperature combustion gas is supplied to the heat exchanger installed in the hot air circulation path to indirectly heat the hot air by the heat exchanger, and a burner installed in the hot air circulation path. There is a combustion gas direct heating system designed to directly heat hot air.

By the way, since a tunnel furnace for drying a coating film of an automobile body has a length of several tens to hundreds of tens of meters, a temperature distribution required for uniform temperature distribution in the furnace or a required temperature distribution. In order to obtain the above, if the tunnel furnace is divided into multiple zones along its longitudinal direction and hot air circulation paths are formed in each zone, in the case of the combustion gas indirect heating method and the combustion gas direct heating method, each hot air circulation A burner is required for each route, it is difficult to centrally manage, and many maintenance personnel are required.

On the other hand, in the heat transfer oil indirect heating method, it is sufficient to circulate and supply the heat transfer oil heated to a high temperature in the heat transfer oil heating boiler to each heat exchanger, so that the auxiliary equipment for each zone is simplified. In addition, if multiple lines are formed in the coating plant, even if a tunnel furnace is installed for each line, only one heat transfer oil boiler is required, which not only facilitates maintenance. The advantages are that the life of the heat exchanger in each zone is long, there is no risk of fire, temperature control is easy, and centralized control is possible.

[0005]

However, in the case of heating the inside of the tunnel type furnace by the heating medium oil indirect heating method, the temperature inside the furnace is once increased to the working temperature, and so much is needed to maintain the working temperature. Although it does not require the amount of heat of the furnace, if the operation is restarted after the temperature inside the furnace has dropped for a long time after the operation has been stopped for a long time, a large amount of Requires heat,
At this time, the heating oil heating boiler must be designed in accordance with the amount of heat required, so that there is a problem that the heating boiler becomes large and the equipment cost increases.

That is, most of the operating time is sufficient if a relatively small amount of heat capable of maintaining the inside of the furnace at the working temperature can be supplied, but the temperature inside the furnace lowered to room temperature is raised to the working temperature within a predetermined time. In order to do so, a large heating boiler must be operated at full power only during that time, so it was not possible to use a small heating boiler. Therefore, the present invention reduces the facility cost by using a small heating boiler that can maintain the tunnel furnace at the operating temperature, and at the same time, even for a small heating boiler, the operating temperature in the furnace can be kept in the same time as the conventional one. The technical issue is to be able to raise the temperature up to.

[0007]

In order to solve this problem, the first invention of the present application is directed to a tunnel furnace having openings at both ends, and hot air sucked from the inside of the furnace through a return duct from a heat exchanger. In a coating dryer equipped with a hot-air circulation path that has a hot-air circulation fan that heats up to the operating temperature with the supplied heat and then reintroduces it from the supply duct into the furnace, use the heat exchanger as an emergency for coating equipment. A heat transfer oil circulation pipe that circulates and supplies heat transfer oil heated by the exhaust heat of a power generator that generates electric power to be used as a power source is connected to the entrance of the tunnel furnace and the operation of the coating dryer is stopped. An opening / closing door that is closed at times is provided, and the hot air circulation path blows air heated by the heat released by the heat exchanger into the furnace of the tunnel furnace in the hot air circulation path. Wherein the bypass passage is formed that interposed.

Further, in the second invention of the present application, instead of forming the bypass passage in which the heat insulating fan is interposed, the air heated by the heat released by the heat exchanger when the coating drying apparatus is stopped is operated. It is characterized by comprising a control device for operating the hot air circulation fan with a small amount of air that can be blown into the furnace of the tunnel furnace.

[0009]

According to the present invention, during normal operation, the heat transfer oil heated to a high temperature is supplied to the heat exchanger, and the hot air circulation fan installed in the hot air circulation path is operated, Heat is exchanged between the hot air sucked from the inside of the furnace through the return duct and the high-temperature heat transfer oil, the hot air is heated to the working temperature, and the hot air is supplied again into the furnace. At this time, since the hot air sucked through the return duct is at a high temperature close to the operating temperature, the amount of heat supplied via the heat transfer oil is also small, and therefore the heat transfer oil heating boiler can be small in size.

When the operation of the drying device is completed, the hot air circulation fan is stopped and the opening / closing door arranged at the entrance / exit of the tunnel furnace is closed, so that high temperature air is trapped in the furnace. Therefore, the air in and out of the furnace is prevented from flowing in and out, and the temperature in the furnace becomes difficult to escape to the outside of the furnace.

In addition, the power generator for generating electric power, which serves as an emergency power source for the coating equipment, is operated almost without a break in case of emergency, and is heated by the exhaust heat of the power generator so as not to be abnormally heated. Since the heat medium oil circulation pipe for circulating and supplying the heat medium oil is connected to the heat exchanger interposed in the hot air circulation furnace, a small amount of heat is always supplied to the heat exchanger.

Therefore, when the heat insulation fan of the bypass passage formed in the hot air circulation passage is operated, the air heated by the heat released by the heat exchanger is blown into the furnace of the tunnel furnace, and the furnace is heated. Even if the internal temperature falls below the operating temperature, it does not fall to room temperature, so that the furnace can be heated to the operating temperature in a short time when the amount of heat supplied is small when the operation is restarted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments shown in the drawings. 1 is a flow sheet showing a coating and drying apparatus according to the present invention, FIG. 2 is a time chart thereof, and FIG. 3 is a time chart showing another embodiment.

The coating / drying apparatus 1 of this example has a plurality of tunnel furnaces 3, 3 ... Opening the inlets / outlets 2 and 2 at both ends, and operating the coating / drying apparatus 1 at the inlets / outlets 2 and 2. Opening / closing doors 4 and 4 are provided to close the entrances and exits 2 and 2 at rest. Further, each tunnel furnace 3 is divided into a plurality of zones, and a radiant heating zone 5 in which a radiant panel 5 is arranged is formed on the inlet side, and a convection heating zone 6 for blowing hot air directly onto the work is formed on the subsequent stage side. Has been formed.

In each of the zones 5 and 6, the hot air sucked from the inside of the furnace through the return duct 7 is heated to the working temperature by the heat supplied from the heat exchanger 8 and introduced into the furnace from the supply duct 9 again. A hot air circulation path 11 having a circulation fan 10 interposed therein is provided. The heat exchanger 8 installed in the hot air circulation path 11 is connected to a heat medium oil circulation pipe 12 that circulates the heated heat medium oil without interruption, and the heat medium oil circulation pipe 12 is connected to the heat medium oil circulation pipe 12. A medium oil heating boiler 13 is interposed. The heat transfer oil heating boiler 13 includes a combustion chamber 15 that heats the heat transfer oil via the heat exchanger 14, and
The heat exchanger 14 is configured to recover the exhaust heat of a power generator 16 that generates electric power that serves as an emergency power source for coating equipment. Then, the heat generated in the combustion chamber 15 and the power generator 16 is supplied to the heat transfer oil via the heat exchanger 14 to heat at least the temperature in the furnace to a predetermined working temperature. ing.

In addition, the hot air circulation path 11 is provided with a heat insulating fan 17 for blowing air heated by the heat emitted from the heat exchanger 8 into the furnace of the tunnel furnace 3 when the coating drying apparatus 1 is out of operation. A mounted bypass passage 18 is formed. As the heat insulation fan 17, a small one having a smaller air volume than the hot air circulation fan 10 is used, and the heat insulation fan 17 is on / off controlled by a control signal of the control device 19. This control device 1
A temperature sensor 20 for detecting the ambient temperature in the tunnel furnace 3 is connected to 9 and the heat insulation fan 17 is operated when the ambient temperature detected by the sensor 20 falls below a preset predetermined temperature. The switch signal is output.

The above is an example configuration of the present invention.
The operation will be described. First, when the automobile body is dried, the heat transfer oil that has recirculated through the heat transfer oil circulation pipe 12 is transferred to the combustion chamber 15 and the power generation device 1 in the heat exchanger 14.
It is heated to a high temperature by the heat generated in 6 and sent to the heat exchanger 8 arranged in each tunnel furnace 3. As described above, the heating oil heating boiler 13 includes the power generation device 16 as well as the combustion chamber 15.
Since the exhaust heat of is also used as a heat source, the size can be reduced accordingly.

Next, the heat transfer oil heated to a high temperature is fed to the heat exchangers 8, 8 ... Which are provided in the hot air circulation path 11 of each tunnel furnace 3, and the hot air circulation fan 10 tunnels the heat exchanger oil. Heat exchange is performed between the hot air sucked from the inside of the furnace 3 through the return duct 7 and the heat transfer oil, and is heated to the operating temperature. Then, the hot air circulation fan 10 feeds the gas again to the tunnel furnace 3 through the supply duct 9, the inside of the furnace is maintained at the working temperature (for example, 150 ° C.), and the coating film is dried with a constant quality.

When the work of one day is completed, the hot air circulation fan 10 and the heat medium oil heating boiler 13 are stopped, and at the same time, the hot air circulating fan 10 and the heat transfer oil heating boiler 13 are distributed to the respective inlets and outlets 2 and 2 before the temperature of each tunnel furnace 3 is lowered. The opening / closing doors 4 and 4 provided are closed.
(FIG. 2: T ₀ ). As a result, the air inside and outside the furnace does not come in and out, hot air does not flow out of the furnace, and cold outside air does not enter the furnace.Therefore, the temperature inside the furnace does not drop sharply and is extremely slow. And decline. In addition,
Even if the operation of the coating / drying apparatus 1 is stopped, the power generator 16 that generates electric power as an emergency power source for the coating equipment is operated almost without interruption, so that the heat transfer oil is transferred to the heat transfer oil via the heat exchanger 15. Exhaust heat is provided.

The temperature inside each tunnel furnace 3 is
When the temperature is monitored by each temperature sensor 20 and drops below a preset predetermined temperature (for example, 80 ° C.), the control device 19
Outputs a switch signal for activating the heat insulation fan 17 in the bypass 18 provided in the hot air circulation path 11 of the tunnel furnace 3 (FIG. 2: T ₁ ). When the heat insulation fan 17 is rotated, the air in the furnace is sucked from the return duct 7, heat is exchanged with the heat transfer oil by the heat exchanger 8, and the heated air is introduced into the furnace through the supply duct 9. As it is delivered, the temperature inside the furnace rises.

Next, when the temperature inside the furnace detected by the temperature sensor 20 reaches a preset temperature (for example, 80 ° C.), the rotation of the hot air circulation fan 10 is stopped (FIG. 2:
T ₂ ), while repeating this, the temperature in the furnace is maintained at a heat retention temperature of about 80 ° C. At this time, the heat transfer oil circulating in the heat transfer oil circulation pipe 12 can be kept at a predetermined temperature (for example, 80 ° C.) lower than the working temperature by the exhaust heat of the power generation device 16 Since the amount of air blown by the heat insulation fan 17 is smaller than that of the hot air circulation fan 10, the amount of air circulated in the hot air circulation path 11 is small, and the heat transfer oil of the heat transfer oil is passed through the heat exchanger 8. The inside of the furnace is maintained at an appropriate temperature without taking heat more than necessary.

When the operation of the coating drying furnace 1 is restarted, the heat insulating fan 17 is stopped and at the same time, the heating medium oil heating boiler 13 and the hot air circulating fan 10 are started to make the inside of each tunnel furnace 3 predetermined. the temperature is raised to a use temperature (e.g., 0.99 ° C.) (FIG. 2: T ₃ ~T _4). At this time, the temperature inside the furnace is 80 ℃
Since it is kept warm at 80 ° C, it is sufficient to raise the temperature from 80 ° C to 150 ° C, and if the temperature is raised within a certain period of time, it is possible to raise the temperature with a smaller amount of heat than when heating from room temperature to the operating temperature. Therefore, the heating oil heating boiler 13 can be downsized. Then, after the inside of the furnace reaches a predetermined operating temperature, the opening and closing doors 4 and 4 of the entrances and exits 2 and 2 are opened to carry in the work.

The temperature sensor 20 is not limited to the case of being provided for each tunnel furnace 3, but may be provided for each of the heating zones 5 and 6 and the heat insulating fan 17 is operated individually for each of the zones 5 and 6. May be. Further, the case where the hot air circulation path 11 is formed for each of the zones 5 and 6 of the tunnel furnace 3 has been described, but even when only one hot air circulation path 11 is formed for each tunnel furnace 3. Good.

FIG. 3 is a time chart showing another embodiment. In this example, instead of installing the temperature sensor 20,
The control device 19 has a built-in timer, and is configured to output a control signal for starting the operation of the heat insulation fan 17 when a switch signal is output from the timer a predetermined time before the operation of the coating drying apparatus 1 is restarted. .

This means that even if the inside of the furnace is not always kept at a constant temperature when the operation is stopped, if the inside of the furnace is heated to a keeping temperature of about 80 ° C. which is higher than room temperature when the operation is restarted, Similarly to the above, the present invention focuses on the fact that the inside of each tunnel furnace 3 can be heated to a predetermined operating temperature (for example, 150 ° C.). However, the heat quantity of the exhaust heat of the power generation device 16 is not so large, and it takes a long time to raise the temperature to the heat retention temperature when the temperature inside the furnace falls to room temperature. For example, 8:30 am) is set in advance, and the heat insulating fan 17 is started, for example, 3 hours before that.

First, when the work of one day is completed, the hot air circulating fan 10 and the heat medium oil heating boiler 13 are stopped, and at the same time, the opening / closing doors 4, 4 arranged at the entrances / outlets 2, 2 of each tunnel furnace 3. Block 4 (FIG. 3: T ₀ ). And
The temperature inside the furnace gradually decreases, and when the operation is restarted (for example, 8 am
At 3 hours before (hour 30 minutes) (5:30 am), a control signal for starting the heat insulation fan 17 is output from the control device 19 based on the switch signal output from the timer 20 (FIG. 3: T). ₁ ).

As a result, the air in the furnace is heated by the heat insulation fan 17
Is sucked from the return duct 7 and heat-exchanged with the heat medium oil by the heat exchanger 8, and the heated air is fed into the furnace through the supply duct 9 and the temperature inside the furnace gradually rises. . Then, when the operation of the coating / drying apparatus 1 is restarted (8:30 am), the temperature inside the furnace reaches a preset temperature (for example, 80 ° C.), and here the heating oil heating boiler 13 and the hot air circulating fan 10 are used. When activated, the temperature rises from 80 ℃ to 150
It is sufficient to raise the temperature to ° C (Fig. 4: T _{2 to} T ₃ ), and in this case as well, the heating oil heating boiler 13 can be downsized.

FIG. 4 is a flow sheet showing another coating drying apparatus according to the present invention, and FIG. 5 is a time chart thereof. In addition, the same reference numerals are given to portions common to FIG. 1 and detailed description is omitted. In this example, instead of operating the heat insulation fan 17 when the coating drying apparatus 1 is not operating, the hot air circulation fan 10 interposed in the hot air circulation path 11 is controlled by, for example, an inverter to reduce the rotation speed and operate with a small air volume. I am trying to let you.

That is, when the operation of the coating / drying apparatus 1 is completed, the opening / closing doors 4 and 4 are closed, and the hot air circulating fan 10 and the heat medium oil heating boiler 1 which have been operated with a large air volume.
3 is stopped and the temperature in the furnace gradually decreases (Fig. 5:
T ₀ ). Then, when the temperature inside the furnace detected by the temperature sensor 20 falls below a preset temperature (for example, 80 ° C.), the hot air circulation fan 1 is rotated at a rotational speed lower than the normal rotational speed.
A control signal for rotating 0 is output from the control device 19,
A small amount of air is circulated in the hot air circulation path 11 (FIG. 5: T _{1 to} T ₂ ). At this time, since the heat transfer oil heated by the exhaust heat of the power generator 16 is supplied to the heat exchanger 8, the heat circulates the air circulating in the hot air circulation path 11 and sends it to the furnace. It is supplied and the temperature in the furnace rises.

Next, when the temperature inside the furnace detected by the temperature sensor 20 reaches a preset temperature (for example, 80 ° C.), the rotation of the hot air circulation fan 10 is stopped (FIG. 5:
T ₂ ), while repeating this, the temperature in the furnace is maintained at a heat retention temperature of about 80 ° C. Then, when the operation of the coating drying furnace 1 is restarted, the hot air circulating fan 10 is operated at a normal rotation speed and, at the same time, the heating medium oil heating boiler 13 is activated,
The inside of each tunnel furnace 3 has a specified operating temperature (for example, 150
(° C.) (FIG. 5: T _{3 to} T ₄ ). Also in this case,
It is sufficient to raise the temperature from 80 ° C. to 150 ° C., and the heating oil heating boiler 13 can be downsized. In addition, when the hot air circulation fan 10 is operated with a small air volume, the operation is not limited to the case where the temperature sensor 20 detects the temperature inside the furnace, and the operation is started before a fixed time when the operation of the coating drying apparatus 1 is restarted using a timer. You may do it.

[0031]

As described above, according to the present invention, when the operation of the coating dryer is stopped, the exhaust heat of the emergency power generator is used to keep the inside of the tunnel furnace warm, and the operation is restarted. Sometimes it is enough to raise the temperature of the inside of the furnace that is kept warm to the operating temperature, so if the temperature is raised within the same time, the amount of heat is less than when heating from room temperature to the operating temperature.
Therefore, there is a very excellent effect that the heating oil heating boiler can be downsized and the facility cost can be reduced.

[Brief description of drawings]

FIG. 1 is a flow sheet showing a coating / drying apparatus according to the present invention.

FIG. 2 is its time chart.

FIG. 3 is a time chart showing another embodiment.

FIG. 4 is a flow sheet showing another coating drying apparatus according to the present invention.

FIG. 5 is a time chart thereof.

[Explanation of symbols]

1 ... Coating drying device 2 ... Doorway 3 ... Tunnel furnace 4 ... Opening door 7 ... Return duct 8 ... Heat exchanger 9 ... Supply duct 10 ... Hot air circulation Fan 11 ... Hot air circulation path 12 ... Heat oil oil circulation piping 13 ... Heat oil oil heating boiler 14 ... Heat exchanger 15 ... Combustion chamber 16 ... Power generator 17 ... Heat insulation Fan 18 ... Bypass 19 ... Control device 20 ... Temperature sensor

Claims (4)

[Claims] 1. A tunnel-type furnace (3) having openings (2, 2) at both ends, hot air sucked from inside the furnace through a return duct (7) is supplied with heat from a heat exchanger (8). The heat exchanger (8) in a coating drying apparatus provided with a hot air circulation path (11) having a hot air circulation fan (10) which is heated to a working temperature and introduced again into the furnace from a supply duct (9). Is connected to a heat medium oil circulation pipe (12) for circulating and supplying heat medium oil heated by exhaust heat of a power generation device (16) that generates electric power that serves as an emergency power source for coating equipment. The doorway (2, 2) of 3) is provided with an opening / closing door (4, 4) that closes the doorway (2, 2) when the coating dryer is not operating, and the hot air circulation path (11) is The air heated by the heat released by the heat exchanger (8) when the coating dryer is stopped is Paint drying apparatus characterized by bypass the heat insulating fan (17) is interposed for blowing air to the tunnel shape furnace in the furnace (18) is formed. 2. The coating / drying apparatus according to claim 1, further comprising a control device (19) for operating the heat insulation fan (17) when the atmospheric temperature of the tunnel furnace (3) becomes lower than a predetermined temperature. 3. The coating / drying apparatus according to claim 1, further comprising a control device (19) for starting the operation of the heat insulation fan (17) by a switch signal output from a timer at a predetermined time before restarting the operation of the coating / drying apparatus. apparatus. 4. A tunnel type furnace (3) having openings (2, 2) at both ends is provided with hot air sucked from inside the furnace through a return duct (7) by heat supplied from a heat exchanger (8). The heat exchanger (8) in a coating drying apparatus provided with a hot air circulation path (11) having a hot air circulation fan (10) which is heated to a working temperature and introduced again into the furnace from a supply duct (9). Is connected to a heat medium oil circulation pipe (12) for circulating and supplying heat medium oil heated by exhaust heat of a power generation device (16) that generates electric power that serves as an emergency power source for coating equipment. The doorway (2, 2) of 3) is provided with an opening / closing door (4, 4) that closes the doorway (2, 2) when the coating drying apparatus is not operating, and the heat exchange is performed when the coating drying apparatus is not operating. The air heated by the heat emitted from the vessel (8) is sent into the furnace of the tunnel furnace (3). A coating drying apparatus comprising a control device (19) for operating the hot air circulation fan (10) with a small air volume that can be blown.