JPH0566194B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This specification describes a method for controlling a coating oven, which can easily and easily eliminate dangers such as explosion and ignition in a continuous baking drying oven without hindering workability or productivity. We propose the results of development research on how to avoid this and ensure safe operation.

Various methods have already been proposed for energy-saving systems for continuous baking and drying ovens for paint films, and a typical example is a continuous baking and drying oven in which treated materials with paint adhered to them are passed through a continuous baking and drying oven, and the furnace exhaust gas generated is transferred to an incinerator. The solvent evaporated gas contained in the furnace exhaust gas is sequentially and continuously incinerated by incinerating the incinerator, and a heat exchanger is installed in the exhaust path of the incineration gas by this incinerator to heat the clean air, and the heated air is continuously baked and dried. It is well known to dry and bake a coating film by introducing it into a furnace. Appropriate control of the heating atmosphere in such a continuous baking and drying furnace is a mode of utilization of the present invention.

(Prior art) The heating atmosphere using preheated clean air in this type of continuous baking drying oven is divided into several zones in the direction of sheet passing, for example, through all of the 1st to 5th zones, and the heating atmosphere temperature in each zone is detected. According to the results, the damper at the dilution air intake and the damper in the clean air piping are controlled by alternately opening and closing, and the furnace exhaust gas containing solvent evaporation gas is blown all at once by a blower through the exhaust gas piping, which has a damper for each zone. It was supposed to be sucked in and guided to the incinerator.

(Problems to be Solved by the Invention) Each part of the continuous baking and drying oven, that is, the first to
The concentration of solvent vapor in the five zones is determined by the rate of temperature rise of the painted steel sheet, the evaporation rate of the solvent in the paint, and the exhaust gas flow rate depending on the restriction of the damper installed in the exhaust gas piping of each zone. Although both the speed and the solvent evaporation rate vary depending on the processing speed, sufficient consideration has not been given to controlling these dynamic factors, and as a result, the solvent concentration is much lower. Air supply and circulation operations were also added to the zones in the heated atmosphere, resulting in power consumption of thermal energy.

(Means for solving the problem) This invention heats clean air with a heat exchanger installed in the exhaust path of incineration exhaust gas by an incinerator, and uses only this heated air to treat paint adhesion. When drying materials in a continuous baking drying oven, the solvent concentration in each part of the drying oven is calculated from the solvent evaporation curve in the paint used and the temperature rise rate of the treated material, and the concentration of the solvent in each part of the drying oven is This is a coating oven control method characterized by setting the exhaust gas emission amount of each part and suppressing the solvent concentration in each part of the drying oven to below the explosive hazardous concentration.

Now, FIG. 1 shows the framework of a continuous baking and drying oven to which the control method according to the present invention is applied.

In the figure, 1 is a coating device, 2 is a processing material, 3 is a roll coater, 4 is a drying oven, and a to e are inside the drying oven.
It represents the first to fifth zones divided into several zones in the sheet passing direction.

Each zone is connected to an incinerator 7 via a blower 6 from the furnace exhaust gas pipes 5a to 5e to incinerate the solvent evaporated gas in the paint. In the figure, 8 is a fuel pipe of the incinerator 7, 9 is a heat exchanger, and 10 is a chimney.

The heat exchanger 9 preheats clean air taken in by the blower 11, and the air is blown to each zone of the drying oven 4 via circulation blowers 12a to 12e. 1 in the diagram
3 and 14 are hot air and cold air adjustment dampers, 15
is a controller that controls the alternating operation of the adjustment dampers 13 and 14 based on the detection signal of the temperature of the air sent to the first zone a (note that this control system is omitted from illustration for areas other than the first zone a to simplify the illustration). It is.

In the above points, the continuous baking drying furnace 4 follows the conventional configuration, and in addition, it is equipped with a detector 16 for measuring the rotation speed of the winding roller of the roll coater 3, for example, using the passing speed of the material 2 as the processing speed. Adjustment dampers 18a to 18a to 18e of the furnace exhaust gas passing through the exhaust gas pipes 5a to 5c according to the respective outputs of the furnace exhaust gas flow rate detectors 17a to 17c, particularly up to 5C in most cases among the exhaust gas pipes 5a to 5e.
Controllers 19a to 19 that control the aperture of 18c
Provide c.

In any case, in a steady state, the amount of heat of the clean air heated by the heat exchanger 9, that is, the amount of input heat, and the amount of heat required for drying and baking the paint film are balanced,
There is no need to control the amount of heat input.

If the amount of heat input is too large, the temperature of the heated clean air is detected by the thermometer on the outlet side of the blower 12, and the control is adjusted to open the damper 14 of the dilution air intake and at the same time throttle the damper 13 of the clean air piping. Total 15
It is done through.

(Function) Now, the concentration of solvent vapor in each zone in the baking drying furnace 4 is determined by the temperature increase rate of the treated material 2, the evaporation rate of the solvent in the coating film, and the furnace exhaust gas adjustment damper 18a~
It is determined by the exhaust gas flow rate Q ₁ to Q ₅ by 18e.

For example, in FIG. 2, the processing speed L (m/m/
The relationship between the treated material temperature MT and the amount of solvent evaporation W at the time of 1.sec) is shown. As for the amount of solvent evaporation in each zone, when the line speed changes to L', the temperature of the treated steel sheet becomes MT' and the amount of solvent evaporated also becomes W'.

Therefore, when the processing speed is L, most of the solvent evaporates in the first zone a and the second zone b, and naturally the exhaust gas flow rates Q ₁ and Q ₂ in the first and second zones are changed to Q ₃ ,
It is necessary to make it larger than Q ₄ and Q ₅ , and the exhaust gas flow rate of each zone at this time is: Q _{1 ~ 5} = K × W _{1 ~ 5} (Nm ³ /min) ... (1) Here, W _{1 ~ 5} : Solvent evaporation amount in each zone (Kg/
H), K: Calculated constants determined by solvent components.

Next, by increasing the processing speed L to L', for example, the solvent evaporation curve W' changes, so the amount of solvent evaporation W ₁ in the first zone a and the third zone changes significantly, and especially W ₃ is significantly increased, it is necessary to significantly reduce the exhaust gas flow rate _Q1 and to significantly increase the exhaust gas flow rate _Q3 .

Here, according to FIG. 1, the amount W of solvent brought into the paint is calculated using the processing speed detector 16, and
Calculate the processing material temperature MT in each zone and set the temperature in each zone to the exhaust gas flow rate controller.

The exhaust gas flow rate controllers 19a to 19c adjust the amount of solvent evaporation W1 to _W1 depending on the given processing material temperature _MT1 to _MT3 .
W ₃ C is calculated and exhaust gas flow rates Q ₁ to _{Q 3} are set using equation (1).

Furnace exhaust gas flow meters 17a to 17c as a control system,
It is necessary to include furnace exhaust gas flow rate adjustment dampers 18a to 18c and exhaust gas flow rate controllers 19a to 19c.

In the above specific example, these control systems are not incorporated in the 4th and 5th zones, but the solvent composition,
4th zone 5th depending on solvent evaporation curve, steel plate temperature, etc.
Needless to say, if there is a possibility that the amount of solvent evaporation in a zone increases, safety can be further ensured by installing a control system similar to that for zones 1 to 3 in each of these zones.

In addition, the amount of solvent brought into the paint W and the amount of solvent evaporated in each zone
W ₁ to _{W 5} are the relationship W = W ₁ + W ₂ + W ₃ + W ₄ + W ₅ , and the amount of solvent brought in W and the main exhaust gas flow rate
Q ₀ + W ₄ + W ₅ is Q ₀ = K ₀ W (Nm ³ /h)...(2) where W: Amount of solvent brought into the paint (Kg/h), K ₀ :
It is expressed as a constant determined by the solvent components.

(Example) 1 Dimensions and thickness of treated material 0.27 at a drying oven temperature of 300°C
An example in which the solvent isophorone is used is described below with a width of 914 mm and a line speed of m/min with a wet coating thickness of 40 g/m ² (dry coating thickness 20 g/m ² ).

The lower explosive limit of isophorone is 0.8%, and under these conditions the amount of solvent W brought into the drying oven is W≒
110Kg/h, and the exhaust gas flow rate to maintain safety is Q ₀ =K ₀ K≒150Nm ³ /min.

Conventionally, when this Q ₀ is equally distributed to the exhaust gas flow rate Q _{1 to 5} in each zone, each Q _{1 to 5} = 30Nm ³ /min. At this time, from the amount of solvent evaporation in each zone, the amount of solvent in each zone is W ₁ = 42% x 110Kg/h = 46Kg/h W ₂ = 26% x 110 〃 = 28 〃 W ₃ = 15% x 110 〃 ≒16 〃 W ₄ W ₅ 17% x 110 〃 ≒ 20 〃 Then, Q ₁ = 60Nm ³ /min Q ₂ = 40Nm ³ /min Q ₃ = 20 〃 Q ₄ = 15 〃 Q ₅ = 15 〃 The exhaust gas flow rate was set. As a result, we were able to operate safely.

2 In Example 1, when the temperature inside the drying oven was changed to 320°C and the line speed was changed to 120 m/min, and the operation was performed at a wet coating film thickness of 40 g/m ² (dry coating thickness 20 g/m ² ), the drying oven was brought into the drying oven. Solvent amount W≒132Kg/h
Therefore, Q ₀ ≒180Nm ³ /min.

The amount of solvent evaporated in each zone at this time is W ₁ = 25% x 132Kg/h = 33Kg/h W ₂ = 45% x 132 〃 = 59 〃 W ₃ = 20% x 132 〃 = 26 〃 W ₄ W ₅ 10 %×132 〃 = 14 〃 〃 Therefore, Q ₁ = 45Nm ³ /min Q ₂ = 80 〃 Q ₃ = 35 〃 Q ₄ = 10Nm ³ /min Q ₅ = 10 〃 It is possible to operate safely by setting the exhaust gas flow rate. Ta. 1 due to the line speed and the difference between the temperature inside the drying oven and the material temperature.
Solvent evaporation amount for each zone, zone 2, and zone 3
It is clear that W ₁ to W ₃ and, on the other hand, the exhaust gas flow rates Q ₁ to _{Q 3} for maintaining safety also vary greatly.

(Effects of the Invention) According to the present invention, dynamic factors such as the processing speed of the processed material passed through the continuous baking drying oven and the resulting relative changes in the amount of solvent evaporation gas in each zone in the oven can be used as control factors. By this, a more effective and efficient continuous baking drying operation can be appropriately controlled without explosion or ignition in the furnace.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a continuous baking drying furnace, and FIG. 2 is a graph showing the dependence of the temperature of the treated material and the amount of solvent evaporation on the processing speed in each zone in the furnace.

Claims (1)

[Claims] 1 Heat the clean air using a heat exchanger installed in the exhaust path of the incinerator exhaust gas,
When drying treated materials coated with paint in a continuous baking drying oven using only this heated air, the temperature at each location in the drying oven is determined based on the evaporation curve of the solvent in the paint used and the temperature rise rate of the treated materials. A method for controlling a coating oven, characterized in that the solvent concentration is calculated, the exhaust gas emission amount of each part of the drying oven is set accordingly, and the solvent concentration of each part of the drying oven is suppressed to below an explosive hazardous concentration.