JPS6150672A - Method for operating continuous drying and baking oven of paint - Google Patents

Abstract

PURPOSE:To attain to effectively utilize quantity of heat, by preheating purified air by the combustion exhaust gas of an incinerator and performing drying and baking by this purified air while burning solvent evaporation gas by the exhaust gas, after drying and baking, and fuel. CONSTITUTION:The combustion temp. outputted from an incinerator 8A is regulated corresponding to the quantity of heat required in each zone of a drying and baking oven 6A and purified air is heated by the combustion exhaust gas of the incinerator 8A while the drying and baking in the drying and baking oven 6A is performed by the heated purified air. The solvent evaporation gas in the incinerator 8A is burnt only by the exhaust gas of this drying and baking furnace 6A and fuel. By this method, the quantity of heat of the exhaust gas can be effectively utilized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of operating a continuous drying and baking oven for paint, and in particular, a method of operating a drying and baking oven that prevents dust from adhering to the paint surface using a simple system. Regarding this, it is used in the field of drying and baking treated materials with paint attached.

[Conventional technology]

Conventionally, various methods have been proposed for energy saving systems for continuous drying and baking equipment for paint.

Representative examples thereof are disclosed in JP-A-57-50576 and JP-A-57-95585, and the features of this method will be explained with reference to FIG. The strip 2 is coated with paint by a coater roll 4 and then passed through a drying and baking oven 6. The drying and baking furnace 6 receives a part of the incineration exhaust gas from the incinerator 8 via a return gas pipe 10 and a blower 12, and uses it as a heat source for drying and baking the paint. Two heat exchangers 16 and 18 are provided in series in a discharge path 14 for the remaining incineration exhaust gas from the incinerator 8. Furnace exhaust gas from the drying and baking furnace 6 is supplied to the incinerator 8 through a furnace exhaust gas pipe 20, a blower 22, and a heat exchanger 16. Further, the incinerator 8 is supplied with combustion air via the blower 24 and the heat exchanger 18, and burns the fuel 26 in the burner 28, thereby incinerating the solvent vapor contained in the furnace exhaust gas supplied from the drying and baking furnace 6. do. A part of the incineration exhaust gas from the incinerator 8 is supplied to the drying and baking furnace 6 as described above, and the remaining part recovers exhaust heat in the two heat exchangers 16 and 18, and is radiated into the atmosphere from the chimney 30. That is, the incineration exhaust gas of the incinerator 8 is effectively used as described above,
Although the fuel consumed by the incinerator 8 is reduced, this conventional method has the following drawbacks.

(b) Since a part of the incineration exhaust gas from the incinerator 8 is used in the drying baking furnace 6, unburned matter, dust, etc. generated in the incineration exhaust gas adhere to the paint surface, which tends to cause quality problems, especially This tendency was noticeable when heavy equipment was started, and it took time to prepare the parts before starting painting.

(b) The incinerator 8 is incinerated at a constant temperature, and a part of the incineration exhaust gas of the incinerator 8 is transferred to the dry incineration furnace 6.
However, if the amount supplied to the drying and baking furnace 6 is less than the amount discharged from the drying and baking furnace 6, intrusion air will be generated from the entrance and exit of the drying and baking furnace 6, and the temperature inside the drying and baking furnace 6 will decrease. As the amount of fuel consumed by the incinerator 8 increases, the heating rate of the strip 2 slows down, and it often becomes impossible to heat up the strip 2 to the target temperature, resulting in defective cine products.

On the other hand, if the amount supplied to the drying and baking furnace 6 is larger than the amount discharged from the drying and baking furnace 6 in order to maintain the oxygen concentration inside the drying and baking furnace 6 at around 5%, the drying and baking furnace containing solvent evaporation gas may be used. The in-furnace gas of No. 6 is blown out from the entrance and exit of the drying and baking furnace 6, and the amount of solvent combusted in the incinerator 8 is reduced, so that the amount of fuel consumed in the incinerator 8 increases and the working environment deteriorates.

(A part of the incineration exhaust gas from the line cinerator 8 is used in the drying and burning furnace 6, but this exhaust gas has a low oxygen concentration,
Depending on the fuel used in the incinerator 8, the dew point may be high.If the temperature of the strip 2 is not raised above the dew point when applying the paint, quality problems such as color unevenness of the paint may occur due to dew condensation during the initial drying stage. strip 2 during application.
It is necessary to heat the temperature above the dew point. As a result, volatile components evaporate due to the high temperature of the strip 2 in the space after coating with the coater roll 4 and before entering the drying baking oven 6.
This not only deteriorates the working environment of the coater chamber but also increases the amount of fuel consumed in the incinerator 8 since the amount of solvent burned in the incinerator 8 decreases. FIG. 3 shows the relationship between 0.8% and dew point when coke oven gas is combusted. % is λ
In the range of 16 to 18%, the dew point is as high as around 40°C.

) The furnace exhaust gas from the drying and baking furnace 6 is connected to the furnace exhaust gas piping 20.
The air is blown to the incinerator 8 via the blower 22 and the heat exchanger 16, but since it contains solvent evaporation gas, there is a risk of explosion if it is excessively heated by the heat exchanger 16, so the upper limit of the heating temperature is set. For safety reasons, the temperature is limited to 500°C or less.

As a result, when high temperatures are required to dry and bake the paint, there is a shortage of heat, so it is necessary to increase the amount of fuel in the incinerator 8 and provide a bypass in the heat exchanger 16.
Energy saving effects tended to decrease on lines that manufactured a wide variety of products.

(e) Solvent evaporation gas in the furnace exhaust gas of the drying and baking furnace 6 is incinerated by the incinerator 8, but since the oxygen concentration in the incineration exhaust gas of the incinerator 8 is as low as 2 to 10%, the incineration temperature of the incinerator 8 is 760 to 760. It is necessary to raise the temperature to a high temperature of 900° C., which increases the amount of fuel consumed by the incinerator 8.

[Problem that the invention seeks to solve]

The purpose of the present invention is to solve the problems of the prior art, such as the need for adjustment time, increased fuel consumption, and reduced energy saving effect, and to use clean air with temperature control in the drying and baking furnace. The object of the present invention is to provide a method for operating a continuous drying and baking furnace for paint, which can also effectively utilize the amount of heat of incineration exhaust gas from an incinerator.

[Means for solving problems]

The gist of the present invention is as follows.

That is, in the method of operating a continuous drying and baking furnace for paint, in which the treated material to which the paint is adhered is continuously passed through the drying and baking furnace, and the generated furnace exhaust gas is guided to an incinerator to incinerate the solvent evaporation gas contained therein. a step of adjusting the incineration temperature output from the incinerator according to the required heat amount of each zone of the drying and baking furnace; a step of heating the clean air with a heat exchanger provided in the incineration exhaust gas discharge path of the incinerator; a step of mixing unheated air with the air heated by the heat exchanger to adjust the temperature of the heated air; and a step of drying and baking the paint in the furnace using only the heated air whose temperature has been adjusted by the first stage. 4. A method for operating a continuous drying and baking furnace for paint, comprising the step of increasing/decreasing the mixing ratio of the air and adjusting the combustion temperature of the incinerator in accordance with changes in the amount of heat in the furnace. It is.

The details of the present invention will be explained based on the embodiment shown in FIG. In addition, in FIG. 1, the same members as in FIG. 2 are indicated by the same reference numerals, and therefore redundant explanation will be omitted. Incinerator exhaust gas exhaust path 14 of the incinerator 8A of the present invention
A is provided with a large scale heat exchanger 32, and the heat exchanger 32
Cold air is introduced through the interlocking valve 34. Interlocking valve 3
On the entrance side of 4? A purifier 936 is provided for supplying clean air into the heat exchanger 32, and an air control valve 38 is connected to the purifier 36 for regulating the amount of clean air being taken in. An interlocking valve 4o is provided between the outlet side of the blower 36 and the heat exchanger 32 to adjust the amount of air. The heat exchanger 32 and the drying and baking furnace 6A are connected by a 'J path 42, and a plurality of blowers 12A are disposed between the path 42 and each zone of the drying and baking furnace 6A. A flow rate regulating valve 44 is inserted in which adjusts the heated air 1 by +'j1'1. Further, a superheat prevention control valve 46 is provided between the interlocking valve 40 and the discharge path 14A in order to prevent the heated air output from the heat exchanger 32 from reaching a predetermined temperature or higher. A flow meter 48 for measuring the air flow rate flowing through the passageway 42 and a pressure gauge 50 for measuring the air pressure in the passageway 42 are provided. On the other hand, the burner 28 of the incinerator 8A has fuel 26
A fuel control valve 52 is provided to adjust the amount of fuel supplied.

A furnace exhaust gas flow rate control valve 54 for adjusting the flow rate of furnace exhaust gas is provided between the blower 22 and the drying and baking furnace 6A, and a furnace exhaust gas flow meter 56 is provided between the blower 22 and the incinerator 8 as well as stones. Further, the drying and baking furnace 6A is provided with an in-furnace pressure gauge 58 for measuring the in-furnace pressure.

[Effect].

In the above configuration, the air supplied from the blower 36 is heated by the heat exchanger 32 and is blown to the drying and baking furnace 6A. In this case, the air blowing temperature is determined by the interlocking valves 34 and 40.
adjusted by. That is, the amount of heat to be supplied is controlled by mixing and outputting the amount of air that is not heated by the heat exchanger 32 bypassed by the interlocking valve 4o and the amount of heated air.This heated air is supplied to the blower 12A.
When supplying to each of the zones, the flow rate is made variable by each of the current amount control valves 44 in accordance with the temperature required by each zone of the drying and baking furnace 6A. Furthermore, the clean air control valve 3 is adjusted so that the amount of furnace exhaust gas output from the drying and baking furnace 6A is balanced with the amount of heated air output from the entire flow rate control valve 44.
Adjust by 8.

As a result, the amount of heated air and the amount of cold air are controlled so that the amount of heat of the heated air supplied to the six drying and baking ovens becomes the amount of heat necessary for the drying and baking oven 6A.

The paint is dried and baked only with the heated air whose temperature is controlled in this way. Furnace exhaust gas containing solvent evaporation gas from the drying and baking furnace 6A 1-1. Furnace exhaust gas amount W20.
The amount of furnace exhaust gas blown to the incinerator 8A via the blower 22 is controlled by the furnace exhaust gas flowmeter 56 and the furnace pressure controller 58 so that the concentration of solvent evaporated gas in the furnace of the drying and baking furnace 6A becomes a value necessary for explosion prevention. and is controlled by a furnace exhaust gas flow rate control valve 54. The incinerator 8A is basically clean air, and the furnace exhaust gas containing solvent evaporation residue and fuel 2
6, stable combustion and incineration can be performed without particularly requiring combustion air.The combustion temperature of the incinerator 8A is set to 600 to 600 so that the opening degree of the cold air side interlocking valve 40 becomes the lower limit value (io to 30% open). In order to automatically control in the range of 900° C., the opening degree of the cold air side interlocking valve 40 is detected, and the fuel control valve 52 of the incinerator 8A is controlled so that the combustion incineration temperature of the incinerator 8A becomes the set temperature.

The incinerator exhaust gas from the incinerator 8A passes through the exhaust path 14A and the heat exchanger 32, and is released into the atmosphere from the chimney 30.

The method of the present invention requires simple equipment and piping, and
Since temperature-controlled heated air is used in the drying and baking oven, factors that adversely affect the quality of the paint surface, such as dust and dew point, can be eliminated.

〔Example〕

By the method of the present invention, a strip with a thickness of 0.37 mm and a width of 914 mm was produced at a line speed of 100 m/min at a rate of 173 tons/min.
The operating specifications are shown in Table 1.

Incidentally, strips of the same value and size were processed using the conventional method shown in FIG. 2, and the results are also shown in Table 1 for comparison.

In Table 1, the embodiment of the present invention has 02
% is 20 degrees or more, the dew point is low, and the strip temperature at the inlet of the coater can be lowered by 20 degrees Celsius than the 50 degrees Celsius of the conventional example. Therefore, there is less solvent evaporation outside the furnace, and the evaporated solvent collection rate is 35 cm higher than the 60 cm of the conventional example, improving the working environment in the coater room and reducing the fuel consumption rate in the incinerator by 4 x 10" It is possible to reduce kcaJ2/.

〔Effect of the invention〕

As is clear from the above embodiments, the present invention preheats clean air with incineration exhaust gas from an incinerator, performs drying and baking in a baking drying oven using only this heated clean air, and uses only the oven exhaust gas and fuel of this baking drying oven. When the solvent evaporation gas was incinerated in the incinerator, the following effects could be achieved.

4. Unlike the conventional method, the incineration exhaust gas from the incinerator is not used in the drying baking furnace, so defects on the paint surface caused by dust and low dew points are eliminated, and the quality can be improved.

(B) The amount of heat supplied to the drying oven varies greatly depending on the product type, but even for the same product type, the width of the IJ tube,
Varies depending on plate thickness, etc. Generally, there is a long time lag in changing the temperature of high-temperature gas via a heat exchanger, but in addition to the above, this system automatically controls the combustion incineration temperature of the incinerator according to the amount of heat required for the drying oven. The amount of heat supplied to the drying and baking furnace is controlled by the amount of heated air that is controlled by the temperature. Even if the amount of heat required for the drying and baking furnace changes suddenly, such as the strip width or thickness, the ratio between the amount of heated air and the amount of cold air remains constant. By changing the amount of heat, the necessary amount of heat can be quickly supplied to the drying and baking furnace. In addition, if changes in strip width, thickness, etc. are detected in advance and feed forward control is performed to input the necessary amount of heat into the drying oven, it is possible to
Even if there is a change in plate thickness, etc., it is no longer necessary to pass the plate through until the temperature of the drying oven becomes stable.

C) Since the solvent collection rate is excellent, the working environment is improved and fuel consumption in the incinerator can be reduced. The energy saving effect is particularly remarkable during high-temperature baking operations and multi-product operations.

0 The oxygen concentration in the incineration exhaust gas of the incinerator is 15~
It is as high as 17%, and the incineration temperature of incinerator 8A is 600%.
Since it can operate in the range of ~900℃, the production volume (t/h)
It is possible to efficiently operate a wide variety of products with greatly different characteristics.

(2) Installation and piping are easy, so equipment costs are low.
Moreover, since the operating system is simple, operation is easy.

[Brief explanation of drawings]

Fig. 1 is a layout diagram showing an embodiment of the continuous drying and baking equipment for paint according to the present invention, Fig. M2 is a layout diagram of the equipment showing the conventional continuous drying and baking method for paint, and Fig. 3 is the combustion of coke oven gas. Time 0! FIG. 3 is a diagram showing the relationship between χ and dew point. 2...Strip, 6,6A...Drying baking furnace 8
．． 8 people... Incinerator, 14.14A... Discharge route, 20.2OA... Furnace exhaust gas piping, 32... Heat exchanger, 34.40... Interlocking valve 38
...Clean air control valve,

Claims (1)

[Claims] (1) In a method of operating a continuous drying and baking furnace for paint, in which the treated material with paint adhered to it is continuously passed through a drying and baking furnace, and the generated furnace exhaust gas is guided to an incinerator to incinerate the solvent evaporated gas contained therein. a step of adjusting the incineration temperature output from the incinerator according to the required heat amount of each zone of the drying and baking furnace; a step of heating clean air with a heat exchanger provided in the incineration exhaust gas discharge path of the incinerator; A step of mixing unheated air with the heated air by the heat exchanger to adjust the temperature of the heated air, and drying and baking the paint in the furnace using only the heated air whose temperature has been adjusted in the step. and a step of increasing/decreasing the mixing ratio of the air and adjusting the combustion temperature of the incinerator in accordance with changes in the amount of heat in the furnace. Operating method.