JPH04243580A - Operation of painting drying oven - Google Patents

Abstract

PURPOSE:To enhance painting quality after drying by avoiding the generation of an air stream over the zones in a painting drying oven in the operation of the painting drying oven wherein the discharged air from a plurality of the zones in the oven is subjected to incineration treatment in a combustion apparatus and the fresh air distributed and supplied to the zones in the oven is heated by the heat exchange with the discharged combustion gas from the combustion apparatus. CONSTITUTION:With respect to the zones 3 in an oven, the amounts of discharged air and the supply amounts of heated fresh air are fixed to almost equal amounts Qa, Qb, Qc and the temp. Ta of heated fresh air is set so that the quantity of heat applied to the respective zones 3 in the oven by the supply of heated fresh air always becomes insufficient with respect to the necessary quantities Wa, Wb, Wc of heat of the zones 3 in the oven and the outputs of the radiation heating devices 12 arranged to the respective zones 3 in the oven are adjusted so that the insufficient quantities of the necessary quantities Wa, Wb, Wc of heat are compensated by the radiation heating devices 12 with respect to the heat load fluctuations of the respective zones 3 in the oven.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method of operating a paint drying oven for heating and drying various coated objects such as automobile bodies and plate materials to be processed into various objects after painting. The exhaust air from each of the plurality of furnace zones lined up in the conveyance direction is incinerated by a combustion device, and the fresh air heated by exchanging heat with the high-temperature combustion gas from the combustion device is delivered to the furnace zone. This invention relates to a method of operating a paint drying oven that distributes and supplies in parallel.

0002

[Prior Art] Conventionally, in the operating method of this type of paint drying furnace (see Fig. 3), heating is distributed to each furnace zone 3 in response to heat load fluctuations in each furnace zone 3. fresh air O
The supply amount Q of A is individually changed and adjusted by the damper 13 installed in the branch air supply path 5, and the required heat amount Wa,
Wb and Wc were to be given.

In the figure, 7 is a combustion device for incinerating the exhaust air EA from each of the furnace zones 3, and 9 is a combustion device for incinerating the fresh air OA supplied to each of the furnace zones 3 at a high temperature from the combustion device 7. A heat exchanger 15 exchanges heat with gas G to heat it to a predetermined temperature, and 15 exchanges heat with exhaust air EA from each of the in-furnace zones 3 with high-temperature combustion gas G from combustion device 7 prior to incineration. This is a heat exchanger that preheats the

[0004] Furthermore, in the case where a radiant heating device is additionally installed in each of the in-furnace zones 3, the radiant heating devices are continuously operated at a constant output, and the thermal load fluctuations in each in-furnace zone 3 are On the other hand, the amount Q of heated fresh air supplied to each in-furnace zone 3 was individually changed and adjusted so that the shortage of the required heat amounts Wa, Wb, and Wc was compensated for by the supply of heated fresh air OA.

[0005]

[Problems to be Solved by the Invention] However, in this type of paint drying oven, in order to provide sufficient ventilation in each zone in the oven and quickly remove the solvent gas generated during drying, it is necessary to install a combustion device. In order to stably perform the incineration process of the exhaust air in the furnace, it is necessary to maintain a constant amount of exhaust air. If the amount of heated fresh air supplied to each furnace zone is changed and adjusted individually according to the temperature, the air supply and exhaust balance of each furnace zone will fluctuate, resulting in airflow between the furnace zones. , the air flow condition changes, and due to the generation of air flow between the zones in the furnace and the change in the air flow condition, dust and generated solvent gas are transferred between the zones in the furnace. However, there was a problem in that the quality of the coating deteriorated after drying.

An object of the present invention is to solve the above-mentioned problems by imparting heat to the furnace zone and adjusting the amount of heat imparted in a rational manner.

[0007]

[Means for Solving the Problems] A first feature of the method of operating a paint drying furnace according to the present invention is a combustion device that uses exhaust air from each of a plurality of furnace zones lined up in the conveying direction of the paint to be dried. In a method in which fresh air is incinerated and heated by exchanging heat with the exhaust combustion gas from the combustion device, it is distributed and supplied to the furnace zones in parallel, and the exhaust air is distributed to each of the furnace zones in parallel. and the amount of heated fresh air supplied are fixed to approximately equal values, and the temperature of the heated fresh air supplied to each of the furnace zones is controlled by the heated fresh air supply to each of the furnace zones. The temperature is set so that the amount of heat to be applied is always insufficient for the amount of heat required for each zone in the furnace, and the shortage of the amount of heat in the furnace is The purpose is to adjust the output of each of the radiant heating devices so as to compensate for the radiant heating devices installed in each zone, and its functions and effects are as follows.

[0008]

[Operation] That is, in the first characteristic means described above, the amount of exhaust air and the amount of heated fresh air supplied for each zone in the furnace are fixed to approximately equal values, and the output of each radiant heating device is adjusted. Because it deals with heat load fluctuations in each furnace zone, regardless of heat load fluctuations in each furnace zone (in other words, regardless of adjustment of the amount of heat applied to each furnace zone), It is possible to maintain the supply/exhaust balance of the zones and avoid the generation of airflow between zones in the furnace.

[0009] Also, the temperature of the heated fresh air is set at such a temperature that the amount of heat given to each zone in the furnace by supplying the heated fresh air is always insufficient for the amount of heat required for each zone in the furnace. If the set temperature is selected appropriately, it can be used as a fixed value for the amount of exhaust air and the amount of heated fresh air supplied to each zone in the furnace. A necessary and suitable value can be selected for exhaust air incineration treatment.

0010

As a result of the above operations, according to the first characteristic means of the present invention, the ventilation function for each zone in the furnace and the exhaust air incineration processing function in the combustion device are maintained well.
In addition, it is possible to appropriately adjust the amount of heat applied in response to heat load fluctuations in each furnace zone, while avoiding the generation of air currents between zones within the furnace. The deterioration in coating quality after drying caused by this can be prevented.

(Second and third characteristic means of the present invention)

00
12. A second feature of the present invention is that the combustion device is of a catalytic combustion type.

In other words, in a general direct combustion type combustion device, the incineration temperature required to sufficiently incinerate the exhaust air is high, so the high temperature combustion gas discharged from the combustion device has a large amount of heat. In carrying out the above-mentioned first characteristic means, the amount of heat imparted to each of the zones in the furnace by supplying heated fresh air is limited so that the amount of heat given to each zone in the furnace is always insufficient for the amount of heat required for each zone in the furnace. This means that the amount of heat recovered from the high-temperature combustion gas decreases due to heat exchange between the high-temperature combustion gas from the combustion equipment and fresh air.
If a general combustion equipment is used, where the required incineration temperature is high and the amount of heat retained in the exhaust combustion gas is large, the amount of heat that cannot be recovered and is disposed of outside the system increases, leading to a problem of large energy loss. .

In this regard, if a catalytic combustion type combustion device that can sufficiently incinerate exhaust air even at low temperatures is adopted, the amount of heat retained in the exhaust combustion gas from the combustion device can be reduced while the exhaust air is sufficiently incinerated. Therefore, in implementing the first characteristic means described above, the amount of heat applied to each zone in the furnace by supplying heated fresh air is limited so that the amount of heat provided to each zone in the furnace is always insufficient for the amount of heat required for each zone in the furnace. It is also possible to maintain a high heat recovery rate from exhaust combustion gas, reducing energy loss for the entire equipment. It is possible to maintain the advantage of achieving energy savings by using it as a heat source.

A third feature of the present invention resides in that the radiation heating device is of an electric heating type.

In other words, it is possible to adopt a radiation heating device that uses the hot air generated by a combustion type hot air generator as a heat source, but in this case, the cost of the device is high because it requires ancillary facilities for a hot air duct that requires sufficient insulation. At the same time, this also brings about additional waste heat loss from the combustion exhaust gas, which is disadvantageous in terms of energy saving.

In this regard, if an electric heating type is adopted as the radiant heating device, the above-mentioned hot air duct ancillary facilities and
By being able to avoid additional waste heat loss from combustion exhaust gas, it becomes even more advantageous in terms of equipment costs and energy savings.

[0018]

[Example] Next, an example of the present invention will be described.

As shown in FIGS. 1 and 2, in a tunnel-shaped paint drying furnace in which a painted object 1 to be dried is transported inside the furnace by a conveyor device 2, the interior of the furnace is divided into a plurality of zones in the conveying direction of the painted object 1. A branch exhaust duct 4 that exhausts solvent gas and tar components generated during drying together with the air in the zone, and a branch air supply duct 5 that supplies heated fresh air are divided into zones. It is connected to each of 3.

Exhaust air EA from each zone 3 led from the branch exhaust duct 4 to the main exhaust duct 6 is passed through a catalytic combustion type combustion device 7 having a catalyst layer 7a made of platinum, palladium, etc.
This incineration process incinerates the solvent gas and tar components in the exhaust air and purifies the exhaust air.

On the other hand, the fresh air OA led through the main air supply duct 8 is heated by exchanging heat with the exhaust combustion gas G (incinerated exhaust air) from the combustion device 7 in the heat exchanger 9, and then The zone is supplied via the branch air supply duct 5.
3.

In the figure, 10 is an air supply fan, and 11 is an exhaust fan.

Each zone 3 has a circular internal cross-sectional shape, and an electrothermal radiation heating device 12 is disposed over almost the entire inner circumference thereof.

Further, the heated fresh air OA supplied from the branch air supply duct 5 is blown out from a jet nozzle 16 disposed at the bottom of the zone toward the coated object 1 in the zone 3, and the solvent is By blowing heated fresh air OA that does not contain gas or tar components toward the painted object 1 and causing it to flow around the painted object 1, the generated solvent gas and generated tar components around the painted object 1 can be efficiently removed and removed. To prevent deterioration in coating quality due to condensation of generated solvent gas and generated tar components on the surface of a coated object.

The coated object 1 is dried by radiant heating by the radiant heating device 12 and by convection heating by supplying heated fresh air OA. By adjusting the dampers 13 and 14 installed in the branch exhaust duct 4 and the branch air supply duct 5, respectively, it is possible to achieve sufficient zone ventilation to eliminate solvent gas and tar components in equal amounts. Quantities Qa, Qb
, Qc, thereby maintaining the supply/exhaust balance of each zone 3 and eliminating the zone containing furnace dust, solvent gas, and tar components.
Avoid the generation of air currents between zones, which can cause deterioration in coating quality due to zone-to-zone migration.

Furthermore, by setting the amount of exhaust air sent to the combustion device 7 to be a constant amount (Qa+Qb+Qc), the incineration processing function of the exhaust air EA in the combustion device 7 is stabilized.

In this example, by using the catalytic combustion type combustion apparatus 7, which has a lower incineration temperature and a lower temperature of exhaust combustion gas than a direct combustion type combustion apparatus, the heat exchanger 9 can generate fresh gas. The air heating temperature, that is, the temperature Ta of heated fresh air OA supplied to zone 3, is determined by the above amount Q.
The amount of heat given to each zone 3 by supplying heated fresh air of a, Qb, and Qc (Qa×Ta, Qb×Ta, Qc×T
The temperature at which a) is always insufficient for the required amount of heat Wa, Wb, and Wc in each zone, and the heat load variation in each zone 3 due to the presence or absence and size of the coated object 1 (in other words, ,
Fluctuations in the amount of heat Wa, Wb, Wc required for drying the coated object 1)
, the radiant heating device 12 compensates for the shortfall in the required heat amounts Wa, Wb, and Wc (Wa=Qa×Ta+w
a, Wb=Qb×Ta+wb, Wc=Qc×Ta+wc
), the outputs wa, wb, wc of each radiant heating device 12 are adjusted according to the heat load fluctuation of each zone 3.

[0028] As an example of the incineration temperature Tb of the catalytic combustion type combustion device 7 and the supply temperature Ta of the heated fresh air OA, Tb = 300°C and Ta = 150°C.

Next, another embodiment of the present invention will be described.

The combustion device 7 for incinerating the exhaust air EA from each zone 3 is not limited to a catalytic combustion type; for example, it can heat fresh air OA distributed to each zone 3. In other cases, a direct combustion type may be used, such as when there is a use for recovering the heat retained in the combustion gas.

The radiation heating device 12 installed in each zone 3 is not limited to an electric heating type, but a type using hot air as a heat source may also be applied.

[0032] Note that although reference numerals are written in the claims section for convenience of reference to the drawings, the present invention is not limited to the structure of the accompanying drawings by such entry.

[Brief explanation of the drawing]

[Figure 1] Schematic vertical cross-sectional view showing the furnace configuration

[Figure 2] Cross-sectional view

[Fig. 3] Schematic vertical cross-sectional view showing a conventional example

[Explanation of symbols]

1 Painted object to be dried 3
zone 7
Combustion device 12
Radiant heating device EA
Exhaust air OA Fresh air G Combustion gas Qa
, Qb, Qc Exhaust air amount/heated fresh air supply amount Ta
Heated fresh air temperature Wa,
Wb, Wc Required heat amount wa, wb, wc Output

Claims (3)

[Claims] [Claim 1] Exhaust air (EA) from each of a plurality of furnace zones (3) lined up in the conveyance direction of the painted object (1) to be dried.
is incinerated by a combustion device (7), and this combustion device (7)
) A method of operating a paint drying furnace which distributes and supplies heated fresh air (OA) through heat exchange with exhaust combustion gas (G) to the furnace zone (3) in parallel. Zone (
For each of (3), the amount of exhaust air and the amount of heated fresh air supplied are fixed to approximately equal values (Qa, Qb, Qc), and heated fresh air (
The temperature (Ta) of OA) is determined by the amount of heat (Qa×Ta,
The temperature is set such that Qb×Ta, Qc×Ta) is always insufficient for the required heat amount (Wa, Wb, Wc) of each of the in-furnace zones (3), and A radiant heating device (1) installed in each of the in-furnace zones (3) is used to compensate for the shortfall in the required amount of heat (Wa, Wb, Wc) for each heat load variation.
2) A method of operating a paint drying furnace in which the outputs (wa, wb, wc) of each of the radiant heating devices (12) are adjusted to compensate for the above. 2. The method of operating a paint drying furnace according to claim 1, wherein the combustion device (7) is of a catalytic combustion type. 3. The method of operating a paint drying oven according to claim 1, wherein the radiant heating device (12) is of an electric heating type.