JPS629835B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oven for drying and baking paint by continuously passing a paint coated strip such as a colored steel plate through the oven.

In conventional ovens, in order to prevent the organic solvent in the paint generated by heating the strip from exploding in the oven, the concentration of solvent in the oven is reduced to 1/4 of the explosion limit or less. A large amount of dilution air is supplied into the oven. In other words, this oven requires a large amount of fuel to heat a large amount of dilution air. Further, although the solvent discharged together with the dilution air is incinerated and used for indirect preheating of the combustion air, there is a lot of waste in terms of effective use of heat.

Therefore, in recent years, organic solvents generated by heating paint are sent to a fume incinerator (incinerator) along with a carrier gas (atmosphere) in an oven, where the oxygen concentration in the combustion gas is reduced to 2 to 10%.
(Below the explosive limit of the solvent)
A method has been put into practical use in which this combustion generated gas is returned to the oven and reused as a carrier gas.

According to this method, a large amount of dilution air is not used and the combustion generated gas of the incinerator is directly used as carrier gas, so it has the advantage that fuel efficiency can be greatly improved.

However, on the other hand, the atmosphere inside the oven,
Because the gas produced by combustion in the fume incinerator is used, the dew point is high, for example, around 60°C.

Therefore, if a steel plate coated at room temperature is placed in the latter oven, moisture in the atmosphere will condense on the surface of the coating film, causing a new drawback that depending on the type of paint, the painted surface may change color. It was found that this occurs.

The present invention was made in order to eliminate the drawbacks of the latter type of oven, which incinerates the atmosphere containing a solvent and circulates the combustion generated gas as the atmosphere. A preheating zone with a low dew point atmosphere different from that of the main body is provided, and the passing band is preheated to almost the same temperature as the dew point inside the oven main body before being charged into the oven main body, thereby preventing the occurrence of dew condensation. In addition, the present invention aims to provide an oven in which the solvent generated in the preheating zone is also incinerated in the incinerator of the oven main body, and the combustion generated gas is used as the atmosphere of the oven main body.

Next, the present invention will be explained with reference to the drawings which are one embodiment.

In the figure, reference numeral 1 indicates an oven according to the present invention, which consists of an oven main body 2 and a preheating zone 3. After a strip W, which is a coated steel plate, passing through the oven is preheated to about 60° C. in the preheating zone 3, The paint is dried and baked in the oven body 2.

A gas sealing device 4 is provided on the outlet side of the oven body 2 to prevent the atmosphere of the oven body 2 from mixing with outside air by sucking the atmosphere and ejecting it from the nozzle box 5. Further, an incinerator 7 is provided outside the oven body 2, and an incinerator 7 is provided outside the oven body 2.
The internal atmosphere is sucked by a fan 6 and supplied to an incinerator (fume incinerator) 7, where it is combusted and incinerated with combustion air and auxiliary fuel, and the combustion generated gas is used as the atmosphere of the oven body 2.
circulating within. In the embodiment, this combustion generated gas is transferred together with the atmosphere inside the main body 2 through a temperature setting heat exchanger 8 to a temperature corresponding to each zone (150 to 350
°C), and is supplied into the main body 2 while stirring the atmosphere in each zone. Then, a part of the combustion generated gas reaches the waste heat boiler 9, and its calorific value is effectively utilized.

In the incinerator 7, the oxygen concentration in the combustion generated gas is adjusted to 2 to 10%, and the main body 2
This prevents the solvent from exploding inside.

A sealing device/exhaust device (suction type air curtain) 10 consisting of a nozzle header 11 having a plurality of suction holes is provided on the extraction side of the pre-preparation zone 3, and sucks the atmosphere of the pre-preparation zone 3 and the oven main body 2 to drain the pre-preparation zone. The atmosphere is exhausted and supplied to the incinerator 7. Further, a nozzle header 12 is provided in the preheating zone 3 to sandwich the strip W, and heat for heating the strip W is supplied thereto. That is, the atmosphere in the preheating zone 3 is heated to 100 to 400 DEG C. by the heating device 13 using the solvent vapor-containing atmospheric combustion gas as a heat source, and is ejected from the nozzle header 12 through the preheating zone atmosphere circulation means 14. Note that the preheating zone 3 is filled with air corresponding to the amount of atmosphere sucked from the air curtain device 10 on the charging side (charging port 3a in the embodiment).
It is becoming like being sucked in from. Further, fresh air may be introduced upstream of the heating device 13 to eliminate the circulation of the atmosphere in the preheating zone 3, or the atmosphere in the preheating zone may be directly heated.

In the above configuration, the steel plate W coated at room temperature
first enters preheating zone 3 and is preheated to approximately 60°C.
Water evaporates together with the solvent in the paint in this pre-heating zone 3 as well, but this vapor is sucked in from the air curtain device 10 and fresh air is sucked in from the charging port 3a, so it circulates in the atmosphere and flows through the incinerator. Even when generated heat is used, its dew point is low. Therefore, the steel plate W is heated to a temperature higher than the dew point of the next oven body 2 without forming dew condensation on its surface, and then charged into the oven body 2.

In other words, the steel plate W is dried and baked within the oven body 2 without condensation.

In the above embodiment, one suction type air curtain device 10 was used to seal the oven main body 2 and the preheating zone 3 and to exhaust the atmosphere in the preheating zone 3, but it may be configured with separate devices. Further, although fresh air is introduced into the preheating zone 3 through the inlet 3a, a separate fresh air inlet may be provided.

As is clear from the above explanation, according to the oven of the present invention, an atmosphere containing solvent vapor is burned in an incinerator, and combustion generated gas having a predetermined oxygen concentration is circulated and used as an atmosphere on the charging side of the oven body. ,
A preheating zone is provided via a suction-type sealing mechanism, the atmosphere is made to have a lower dew point than the atmosphere inside the oven body (almost the same as the dew point of the atmosphere), and the strip is heated to a temperature higher than the dew point inside the oven body. .

Therefore, even when the strip is conveyed into the oven main body, no condensation occurs.

Furthermore, since the solvent vapor in the preheating zone is incinerated in an incinerator and the heat thereof is effectively utilized, it is possible to achieve significant energy savings as a whole.

It goes without saying that the strip is not limited to painted steel plates.

[Brief explanation of the drawing]

The drawing is an explanatory diagram of an oven according to the present invention. 2... Oven body, 3... Preheating zone, 3a...
Fresh air introduction port (charging port), 7... Incinerator, 10...
Sealing device and exhaust device (suction type air curtain),
13... Heating device, W... Strip material, 14... Preheating zone atmosphere circulation means.

Claims (1)

[Claims] 1. In an oven that incinerates an atmosphere containing solvent vapor and circulates the combustion generated gas to continuously dry and bake the paint of the paint strip passing through it, a preheating zone is provided, and a preheating zone is provided on the oven charging side of the preheating zone. A suction-type sealing device is provided to make the pre-heat zone different from the oven atmosphere, and the pre-heat zone is equipped with a pre-heat zone atmosphere circulation means, a heating device for heating the pre-heat zone atmosphere with atmosphere combustion generated gas containing solvent vapor, and a pre-heat zone atmosphere. An oven characterized by being provided with an exhaust device and a fresh air introduction port.