JP4863034B2 - Removal and utilization of organic exhaust gas in sintering furnace. - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing organic exhaust gas generated when heat-treating a sintered body for sintering in a sintering furnace and a method for recycling the organic exhaust gas.
[0002]
[Prior art]
In sintering a powder of metal or ceramic, an organic substance that functions to lubricate the powder or fill gaps between the powders is added to physically aggregate and mold the powder. This organic matter is removed from the sintered body by heating in a precursor step prior to sintering when the sintered body is placed on a heat resistant belt and passes through a sintering furnace.
[0003]
[Problems to be solved by the invention]
A tunnel-like high-temperature sintering furnace is often used for this kind of sintering, and the organic additive in the powder molded body is evaporated or decomposed at a temperature around 400 ° C. and diffuses into the furnace atmosphere as exhaust gas. . This gas is harmful because it produces toxic and corrosive substances. Furthermore, a part of this organic substance byclines carbon and contaminates the sintered body.
[0004]
[Means for Solving the Problems]
Therefore, in the present invention, the organic exhaust gas diffused in the furnace atmosphere is guided to the outside of the furnace preheating and sintering passage together with a part of the furnace atmosphere, where it is oxidized at a high temperature of 800 ° C. Change to carbon dioxide and make it harmless. The gas thus treated is sent into the sintering furnace and used as the furnace atmosphere.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
A metal powder molded product containing 33% of an organic material containing a phenolic resin as a binder was heat-treated by a tunnel continuous sintering furnace 1 shown in FIG. The conveyance for passing through the preheating zone 2 and the heating and sintering zone 3 in the furnace was continuously carried on a mesh belt 4 made of heat resistant steel. As shown in FIG. 2, the temperature of the preheating region 2 was sequentially increased from room temperature to 720 ° C. Most of the organic binder evaporated or decomposed at around 400 ° C. to leave the metal powder molding as an organic exhaust gas and diffused into the furnace atmosphere as indicated by the arrows in FIG. A part of the organic binder byclines carbon in the preheating area 2 and contaminates the metal powder molding. However, when the molding further proceeds in the preheating area 2, the carbon also has carbon dioxide gas in a higher temperature atmosphere. Oxygen and water vapor turned into carbon monoxide, leaving the molded product to remove contamination of the molded product. Therefore, the molded product that completed the organic release treatment was placed in the next heating zone 3 and sintered.
[0006]
On the other hand, the organic exhaust gas supported in the furnace atmosphere is sent to the exhaust gas treatment chamber 5. This exhaust gas treatment chamber was provided outside the preheating zone 2 adjacent to the entrance of the furnace 1 and maintained at a temperature of 850 ° C. under a negative pressure. The gas sucked into the exhaust gas treatment chamber 5 is connected to the blower pump 8 and is heated together with the air from the blower pipe 6 to be oxidized and decomposed to contain carbon dioxide, moisture, carbon monoxide, hydrogen, nitrogen and oxygen. It became. This composition and the ratio of each component could be selectively adjusted by the amount of air sent to the exhaust gas treatment chamber, the composition of the atmosphere in the furnace sucked into the exhaust gas treatment chamber together with the organic exhaust gas, and the like. By the way, the atmosphere in the preheating zone 2 does not use air containing a large amount of oxygen as it is to reduce the desired oxidation of the metal powder of the metal powder molding, but contains nitrogen gas, carbon dioxide gas or water vapor. Often to do.
[0007]
The exhaust gas treated in the exhaust gas treatment chamber 5 passes through the conduit 7 and is dehydrated after warming the air in the blower pipe 6, passes through the gas composition meter 10 by the gas pump 9, and serves as a protective atmosphere in the furnace by the pipe 11. It was sent to the heating zone and / or the preheating zone.
[0008]
【Effect of the invention】
After passing through the treatment chamber, the composition of the exhaust gas obtained by dehydration was controllable within the following range, and could be sufficiently used as the furnace atmosphere of the sintering furnace.
CO ₂ .......... 0.5 to 19.0%
H ₂ O ... 0.1 to 0.5
O ₂ ..... 0.1 to 2.0
CO .......... 0.1-8.0
H ₂ ..... 0.1 to 8.0
CH ₄ ..... 0.1 to 1.0
N ₂ .......... 60.0 to 80.0
[Brief description of the drawings]
FIG. 1 is an explanatory sectional view showing an example of a tunnel-shaped continuous sintering furnace suitable for carrying out the method of the present invention.
FIG. 2 is a schematic diagram showing the in-furnace temperature of the same furnace.
[Explanation of symbols]
1-sintering furnace 2-preheating zone 3-heating sintering zone 4-mesh belt 5-exhaust gas treatment chamber 6-air conduit 7-exhaust gas conduit 8-air pump 9-gas pump 10-gas composition meter 11-atmospheric gas tube

Claims (2)

The organic exhaust gas generated from the object to be sintered that passes through the sintering furnace where the preheating zone and the heating and sintering zone are connected is led to the exhaust gas treatment chamber provided in the furnace outside the both zones, and is led to the exhaust gas treatment chamber and the organic exhaust gas oxidative decomposition by heating at least oxygen added 800 ° C. or higher, use as a furnace protective atmosphere of the sintering furnace send this decomposition gas into the preheating zone and / or heat sintering zone A method for removing and using organic exhaust gas in a sintering furnace. The sintered body is a metal powder molding containing an organic binder containing a phenolic resin, the decomposition gas is dehydrated , the gas after dehydration includes any of the following components, and each component is 2. The method for removing and using organic exhaust gas in a sintering furnace according to claim 1, wherein the exhaust gas is within the following range .
_{CO 2: 0.5~19.0%, H 2} O: 0.1~0.5%, O 2: 0.1~2.0%,
_{CO: 0.1~8.0%, H 2:} 0.1~8.0%, CH 4: 0.1~1.0%,
N _2: 60.0~80.0%

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