JP2000356476A - Facilities for treatment of exhaust gas of electric furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent regeneration of harmful components due to soot and dust in exhaust gas, in facilities for treatment of exhaust gas which disposes of the exhaust gas produced from an electric furnace. SOLUTION: Exhaust gas produced from an electric furnace or a scrap preheating apparatus for the electric furnace is introduced into a combustion apparatus 2 through a duct and combusted therein. Cooling equipment 4 which cools down the exhaust gas combusted in the combustion apparatus 2 to a prescribed temperature is connected to the downstream side of the apparatus and the gas cooled down is then subjected to dust collection by a filter type dust collector 5. In facilities for disposal of exhaust gas having this constitution, dust removing equipment 3 collecting soot and dust in the exhaust gas is provided between the combustion apparatus 2 and the cooling equipment 4. This dust removing equipment 3, as dust removing equipment of a cyclone type or an inertial impaction type, removes the soot and dust in the exhaust gas beforehand.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment facility for treating exhaust gas generated from an electric furnace.

[0002]

2. Description of the Related Art When preheating metal materials in an electric furnace or a scrap preheating device, white smoke, odors, aromatic chlorine compounds, etc. are generated as harmful components in exhaust gas generated at the time of preheating. , Is an environmental problem.

[0003] Harmful components are generated in the course of chemical reaction of organic chlorine-based substances. In the electric furnace, a combustion tower is installed to completely combust the exhaust gas generated from the electric furnace.However, incomplete combustion is likely to occur due to fluctuations in the amount of exhaust gas generated from the electric furnace or exhaust gas components, and harmful It is said that components are also likely to occur. Also, even after complete combustion, decomposed chlorine, carbon, hydrogen, etc. are drifting in the exhaust gas, and when the exhaust gas is cooled down to around 300 ° C, dust in the exhaust gas becomes a catalyst to regenerate harmful components. It is said to be done.

[0004] For example, in the invention described in Japanese Patent Application Laid-Open No. 9-133476, a pair of regenerative heat exchangers are provided in a combustion tower for treating exhaust gas discharged from a preheating device for an electric furnace, and a scrap preheating device is provided. Exhaust gas discharged from is passed through the regenerative heat exchanger on one side and sent to the combustion tower, and air is supplied from an air blower to burn in the combustion tower at 800 ° C or higher, and the regenerative heat on the other side The exhaust gas is cooled to 150 ° C. or lower through a heat exchanger, guided to a discharge duct, and discharged to the atmosphere through a bag filter. At this time, a duct collector is arranged between the scrap preheating device and the heat storage exchanger to collect large dust in dust generated when exhaust gas discharged from the combustion tower is discharged. Japanese Patent Application Laid-Open No. HEI 6-117780 discloses that after decomposing harmful components by burning exhaust gas from an electric furnace or a scrap preheating device for an electric furnace using a burner in a combustion tower, the harmful components are decomposed and then rapidly cooled by a gas cooler. Prevent synthesis,
Further, there is disclosed a method of removing harmful components contained in exhaust gas by providing a bag filter in a downstream side.

The invention described in Japanese Patent Application Laid-Open No. Hei 9-133476 discloses a method in which a regenerative heat exchanger is arranged in a combustion tower, and the regenerative heat exchangers are alternately switched to discharge exhaust gas containing dust.
Most of the harmful components in the exhaust gas are thermally decomposed by heating and burning at a temperature of 00 ° C. or higher, and then cooled rapidly to prevent resynthesis and maintain a low level. Thereafter, the exhaust gas is introduced into a filtration type dust collecting facility, and further attempts to remove harmful components by the filtering type dust collecting facility.

The invention described in Japanese Patent Application Laid-Open No. HEI 6-117780 discloses a method in which exhaust gas from an electric furnace or a scrap preheating device for an electric furnace is burned and heated by a burner in a combustion tower, and the heated exhaust gas is kept in a holding chamber for a certain period of time or more. The purpose is to hold and decompose harmful components, and to directly cool the exhaust gas by a spray cooler connected to the outlet side of the holding chamber to prevent the regeneration of harmful components.

[0007]

However, the amount of exhaust gas generated when a metal material is preheated by an electric furnace or a scrap preheating device is about 2000 Nm ^{3 in an} 80 t class electric furnace.
/ Min, about 8 g / Nm ³ in the exhaust gas. The harmful components in the exhaust gas are thermally decomposed even if the exhaust gas containing the dust is heated by combustion in a combustion tower or a combustion mixing device, but the dust in the exhaust gas only increases in temperature, and the heat storage type heat exchanger and The exhaust gas that has been introduced into a dust collector or cooling facility and cooled is collected by a filter to collect dust and is released to the atmosphere. JP-A-9-133
According to the method described in Japanese Patent No. 476, when exhaust gas containing dust generated in the scrap preheating device is introduced into the regenerative heat exchanger, the dust adheres to the heat storage material used for the heat storage unit in the heat exchanger, and Dust clogging occurs and heat exchange becomes impossible.

In Japanese Patent Application Laid-Open No. Hei 6-117780, exhaust gas containing dust is thermally decomposed by a combustion and mixing device, and harmful components held in a holding chamber for a certain period of time are prevented from being regenerated.
And it is rapidly cooled by the cooling equipment on the outlet side. In this device, a spray cooler is used as cooling equipment, so when the exhaust gas containing dust is cooled by the spray water of the cooling equipment, the dust in the exhaust gas is also washed away, and the dust becomes fluid dust, and in the subsequent stage, Large-scale equipment is required for the treatment of dust.

[0009]

An exhaust gas generated from an electric furnace or a scrap preheating device for an electric furnace is introduced into a combustion tower through a duct to burn the exhaust gas, and the exhaust gas burned by the combustion tower is supplied to a subsequent stream. In an exhaust gas treatment facility that connects a cooling facility that cools to a predetermined temperature and then collects dust with a filtration type dust collection facility, a dust removal facility that collects dust in exhaust gas is disposed between the combustion tower and the cooling facility. In addition, the dust removing equipment removes dust in exhaust gas in advance as a cyclone dust removing equipment or a collision type dust removing equipment.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the equipment configuration of the present invention.

In FIG. 1, the metal material and scrap put into the electric furnace 1 are preheated and melted. The exhaust gas generated at this time flows into the combustion tower 2 via the duct 9 connected to the electric furnace. The combustion tower is a device for decomposing harmful components in exhaust gas while completely burning unburned gas in the exhaust gas generated from the electric furnace. As a result of the combustion, the temperature of the exhaust gas becomes 800 ° C. or higher. The temperature of the exhaust gas completely burned in the combustion tower is 300 to 500 ° C., which is the temperature at which the harmful components are regenerated.
The dust removing equipment 3 is arranged so as to flow into the dust removing equipment 3 before the dust removing equipment 3 is lowered. In the dust removal equipment 3, dust contained in the exhaust gas is removed, the removed exhaust gas is introduced into the cooling equipment 4 arranged on the outlet side, cooled to a predetermined temperature, and guided to the dust collection equipment 5 arranged in the subsequent stage. , Captures harmful components and emits them through the chimney 6 to the atmosphere.

In an electric furnace of the 80t class, an exhaust gas amount of about 2000 Nm ³ / min is generated. This exhaust gas contains about 8 g / Nm ³ of dust. That is, in the exhaust gas of 2000 Nm ³ / min, 16
Kg / min dust is contained.

A dust removing device 3 is provided between the combustion tower 2 and the cooling device 4.
In the case where no exhaust gas is contained, even if the harmful components in the exhaust gas are thermally decomposed in the combustion tower 2, the exhaust gas temperature decreases until the exhaust gas is introduced into the cooling facility 4 through the duct, and the exhaust gas contains The contained dust acts as a catalyst and harmful components are regenerated. In the present invention, since the dust removing device 3 is provided between the combustion tower 2 and the cooling device 4, most of the dust can be removed before the harmful component regenerates the dust acting as a catalyst, The rate of harmful component regeneration can be reduced.

As the dust removing equipment 3, a cyclone dust removing equipment or a collision type dust removing equipment is used. The higher the efficiency of the dust removal equipment, the better, but if the dust in the exhaust gas can be reduced even a little, the regeneration of harmful components generated on the secondary side can be reduced. Also,
If the dust in the exhaust gas is reduced, it is possible to reduce the contact of the harmful component after thermal decomposition with the dust, and the regeneration of the harmful component is reduced. Therefore, if the harmful component has a predetermined allowable value, the cooling temperature is increased. And the equipment cost of the cooling equipment can be reduced. If the temperature of the exhaust gas after cooling is constant,
The release amount of harmful components can be reduced. The dust removed by the dust removing equipment 3 is collected in the hopper 8 via the transport device.

[0015]

As described above, by removing the dust contained in the exhaust gas before catalyzing it, it is possible to prevent harmful components from being regenerated, and when cooling to a predetermined temperature with cooling equipment,
If the release amount of the harmful component can be reduced and the allowable value of the harmful component is kept constant, the cooling temperature can be raised, so that the equipment cost of the cooling equipment can be greatly reduced. As described above, the facility effect of the present invention is very large, and greatly contributes to the operation cost effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of the equipment showing the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Combustion tower 3 Dust removal equipment 4 Cooling equipment 5 Dust collection equipment 6 Chimney 7 Transport device 8 Hopper 9 Duct

Claims (2)

[Claims] 1. A cooling system for introducing exhaust gas generated from an electric furnace or a scrap preheating device for an electric furnace into a combustion tower via a duct to burn the exhaust gas, and cooling the exhaust gas burned in the combustion tower in a subsequent stream. In an exhaust gas treatment facility that collects dust with a filtration type dust collection facility after coupling, a dust removal facility that collects dust in exhaust gas is disposed between the combustion tower and the cooling facility. Exhaust gas treatment equipment. 2. The dust removing equipment according to claim 1, wherein the dust removing equipment is a cyclone type dust removing equipment or a collision type dust removing equipment.
Exhaust gas treatment equipment for electric furnaces.