JPS5849787B2 - Recirculating heating drying oven - Google Patents

Description

[Detailed description of the invention] The present invention relates to a recirculating heating drying oven (hereinafter referred to as a drying oven).

). ? Conventional drying ovens used for baking and hardening automobile bodies, etc. are tunnel-type drying ovens with four to six continuous zones. For example, as shown in FIG. 1, each zone of the drying oven body 1 has an independent combustion chamber. 2-24 and burner 3-3
4 is installed, the combustion chambers 2 to 24 and burners 3, to 3
4, the fuel sent through the fuel supply pipe 4 is combusted with the air from the air supply pipe 5, and each zone A1 to A4 (~X) is maintained at a predetermined temperature, and the exhaust gas 19 of each zone is transferred to }
It is usually discharged from 18, to 18-4.

In the figure, 41 to 44 are fuel supply valves, 8 to 84 are combustion air blowers, 13 is an object to be painted (for example, a car body), 11 is a flow direction of hot air, and 14 is an exhaust collection duct. .

By the way, the exhaust gas from the drying oven contains large amounts of combustible substances (which become a source of pollution as hydrocarbons) such as organic solvents, low-molecular resins, and tar components that have volatilized from the paint etc. of the object to be coated. Therefore, it must be purified before it can be discharged outside the furnace, that is, into the atmosphere.

However, as mentioned above, if a purifying device is installed in each exhaust duct provided in each zone, or if the exhaust gas from each exhaust duct is processed together, the processing device There are problems in that the number of devices increases and the device becomes larger, which is not only uneconomical but also reduces processing efficiency.

Usually, a single afterburner system is used for purification, and as a result, a large amount of heat is discarded along with the exhaust gas.

However, since the air for fuel combustion is normally supplied around 5 to 6 times the theoretically required amount of oxygen, there is still a large amount of oxygen remaining in the exhaust gas, but this oxygen is heated by the above process. It was thrown away and was extremely uneconomical.

In addition, as a prior art, for example, Japanese Patent Application Laid-Open No. 4846628
No. 48-62032, Japanese Patent Application Laid-open No. 1973-
Publication No. 36362 can be mentioned.

As a result of intensive research aimed at effectively removing large amounts of combustible substances (hazardous components) that cause pollution contained in exhaust gases and effectively utilizing the amount of heat contained in exhaust gases, the inventors of the present invention have developed the previous method. By supplying the furnace gas of one zone in stages to the burner combustion chamber of the next zone and using it as combustion gas, harmful components in the exhaust gas can be removed and the calorific value of the exhaust gas can be used, reducing fuel consumption. In addition, by installing a catalyst bed in the combustion chamber, harmful components that cannot be removed by the burner can be removed, so the afterburner equipment for treating exhaust gas can be small, reducing equipment costs, etc. The present invention was completed by discovering that the following effects can be obtained.

The drying furnace of the present invention is a burner-heated drying furnace in which a plurality of zones are connected, in which a conduit for guiding the furnace gas of the previous zone is connected to a burner combustion chamber of the next zone, and one or more zones are connected. It has a structure in which a catalyst bed is attached to the combustion chamber and a series of conduits are installed to connect the combustion chamber to the next zone. It is characterized in that it is decomposed continuously and stepwise, and is sufficiently purified at the time of exhaustion.

Relatively low-temperature catalysts such as platinum-based, palladium-based, platinum-palladium-based, and copper-manganese-based catalysts are effective in the catalyst bed of the present invention, and are filled with such catalysts.

These catalysts were heated at 200°C as shown in the diagram in Figure 2.
At the above treatment temperature, it is possible to remove 80% or more of the hydrocarbons.

(Figure 2 shows the purification rate using a platinum-palladium catalyst.

) The hot air used in the conventional burner heating drying oven has a temperature of 200 to 350'C in a steady state, and these catalysts can be used without changing the conventional heating drying conditions. The drying furnace can significantly reduce the hydrocarbon content in the exhaust gas by installing a catalyst.

Furthermore, since the furnace gas from the previous zone is guided step by step to the burner combustion chamber of the next zone, where it comes into contact with the high-temperature flame caused by fuel combustion, it is also subjected to combustion and thermal decomposition here, so it is synergistically reduced. , purified.

Furthermore, the drying oven of the present invention can reuse high-temperature exhaust gas from the previous zone as combustion air for the next zone, significantly reducing fuel costs. Of course you can.

For these reasons, the installation of independent afterburner equipment, which has recently been widely adopted as a measure to deal with hydrocarbon emission regulations, eliminates the need for large capital investments and the enormous fuel and operating costs required for its operation, resulting in an economical solution. The effect is extremely large.

The structure of the drying oven of the present invention will be explained with reference to the drawings.

Although FIG. 3 is a schematic sectional view of the drying oven of the present invention, the present invention is not limited thereto.

As shown in the figure, in the drying furnace of the present invention, a conduit 15-1 for guiding the furnace gas in the first zone is connected to a burner combustion chamber 2-2 in the second zone. A catalyst bed 16 is attached behind the flame 9, and a series of conduits 1[2 connecting the burner combustion chamber 2-2 and the second zone of the drying furnace are installed continuously.

That is, the furnace gas in the first zone is transferred to the burner combustion chamber in the second zone, the furnace gas in the second zone is transferred to the burner combustion chamber in the third zone, and the same series is repeated.

Although not shown, the furnace gas exhaust from the final zone is discharged into the atmosphere through a normal fan and duct exhaust.

In the figure, 6 represents a combustion air filter, 8 and 8 represent combustion air blowers, and 10-1 and 10-2 represent blowers.

To operate the drying oven of the present invention, fuel such as LPG is introduced into the burner 3-1 in the first zone through the fuel supply valve 4-1, and air is further introduced through the combustion air supply blower 8-1. The high-temperature combustion gas is sent into the first zone furnace through the air supply duct IL1 by the blower 10-1 to bring the inside of the first zone furnace to a predetermined temperature, and the object to be coated (for example, a car body) passing through the zone. 13 is heated and dried.

Furnace gas containing organic solvents, low-molecular resins, tar, and moisture volatilized and generated from the object to be coated by this heating and drying is discharged through the exhaust collection duct N4-1 and into the conduit 15-1 to the burner combustion chamber of the second zone. Leads to 2-2.

Next, fuel such as LPG is fed into the burner combustion chamber 2-2 of the second zone in the same way as before the Teja fuel supply valve 4-2, and combustion air is sent in from the blower 8-2 for mixed combustion in the burner 3-2, resulting in a high-temperature flame. 9 and generate high temperature gas.

On the other hand, the furnace gas of the first zone introduced through the conduit 15-1 is fed into the burner combustion chamber 2-2, and comes into contact with the high-temperature flame 9 and the high-temperature gas.
Here, the hydrocarbons contained in the gas in the furnace are combusted and decomposed, and when they pass through the catalyst bed 16 installed in the combustion chamber, the hydrocarbons that have not been completely decomposed by the flames and high-temperature gas are affected by the action of the catalyst. is decomposed at a higher rate.

At this time, since there is still a large amount of oxygen remaining in the furnace gas in the first zone, the action of promoting combustion within the combustion chamber is also performed at the same time.

Incidentally, since the furnace gas in the first zone can be used as combustion air as it is, the combustion air blower 8-
The conduit 15-1 may be directly connected to the burner 3-2.

In addition, all or one catalyst bed or an appropriate number of catalyst beds in the second zone and subsequent zones are provided in the combustion chamber.

Next, the high-temperature gas produced in the second zone burner combustion chamber is blown into the second zone furnace by the blower 10-2 through the conduit 11-2 and the air duct 12-2, and as before, the hot gas is blown into the second zone furnace. heat up.

Further, the furnace gas in the second zone passes through the collecting duct 14-2 and the conduit 15-2 to the burner combustion chamber (
(not shown), and the same process is repeated thereafter.

In the present invention, the above-mentioned series are arranged continuously, and although not shown, they are discharged to the outside of the system in the final zone.

? As mentioned above, the recirculating heating drying oven of the present invention can be obtained by simply modifying the existing paint drying oven, and it can significantly reduce harmful substances in exhaust gas and minimize air pollution and odor problems. The industrial value of the present invention is extremely large, since it is possible to suppress combustion and to circulate and burn high-temperature furnace exhaust gas, thereby significantly reducing fuel costs.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a conventional heating drying furnace with a set of burners, and FIG. 2 is a graph showing the relationship between catalyst treatment temperature and hydrocarbon purification rate. Note that this purification rate graph shows values when a platinum-palladium catalyst is used. FIG. 3 is a schematic cross-sectional view of the recirculating heating drying oven of the present invention. In the figure, 1...Drying furnace body, 2...Combustion chamber, 3...Harner, 4...Fuel supply pipe, 4-4... ... Fuel supply valve, 5 ... Air supply pipe, 6 ... Curved combustion air filter, 7, 11
, 15...Curved conduit, 8...Curved combustion air blower,
9...flame, 1o...bending blower, 12...
... Air supply duct, 13 ... Curved object to be painted, 14 ...
・Exhaust collection duct, 16・Curve・Catalyst bed, 17・Curve・Hot air flow direction, 18... Exhaust duct, 19...
...Indicates exhaust gas.

Claims (1)

[Claims] 1. In a burner-heated drying furnace in which a plurality of zones are arranged in series in the direction of movement of the dried material, a conduit for guiding the furnace gas of the previous zone is connected to the burner combustion chamber of the next zone, and the second zone is It has a structure in which a catalyst bed is installed in one or more combustion chambers, and a series of conduits are installed to connect the combustion chamber and the next zone. A recirculating heating drying furnace that is characterized by continuously and stepwise decomposing and purifying harmful substances such as hydrocarbons contained therein.