JPH0256565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves forming a high-temperature hearth in the lower part of the furnace by burning carbon-based combustible materials, supplying industrial waste or its intermediate processed material to the high-temperature hearth and melting it. The present invention relates to a method for melting industrial waste in which a molten material is taken out of the furnace from the lower part of the bed, air for combustible gas combustion is supplied above the high-temperature hearth, and combustion exhaust gas is discharged from the upper part of the furnace.

The above method controls the amount of oxygen-containing gas supplied to the high-temperature hearth so that the temperature of the high-temperature hearth becomes high and the consumption of carbon-based combustible materials such as coke that forms the high-temperature hearth decreases. Moreover, the unburned gas that tends to be produced is completely combusted by supplying air above the high-temperature hearth, which has the advantage of preventing pollution such as air pollution and the generation of bad odors. However, conventionally, in order to supply air for combustible gas combustion, as shown in FIG. Because the entire amount was being supplied, the temperature of the flue gas in the furnace 3 became extremely high, and the concentration of nitrogen oxides (NOx) in the flue gas from the flue gas passage 8 increased, and dust fused to the inner walls of the furnace. These problems tend to occur, and further improvements are desired.

An object of the present invention is to prevent pollution through complete combustion while sufficiently and reliably suppressing NOx generation and dust adhesion to the inner wall of the furnace. The key point is to devise ways to prevent the consumption of carbon-based combustible substances from increasing unnecessarily.

The characteristic means of the industrial waste melting method according to the present invention is that air for flammable gas combustion is supplied above and above the high-temperature hearth formed at the lower part of the furnace by combustion of carbon-based combustible materials, and is arranged at multiple locations above and below the furnace. Then, a part of the combustion exhaust gas discharged from the upper part of the furnace to the exhaust gas passage is cooled and then supplied to the upper part of the high-temperature hearth, and the temperature of the combustion exhaust gas in the exhaust gas passage is detected by a thermometer. In order to maintain the detected temperature within the set range, the amount of cooled combustion exhaust gas supplied to the high-temperature hearth is adjusted with a flow control valve, the oxygen gas concentration of the combustion exhaust gas in the exhaust gas path is detected with a meter, and the detected oxygen The purpose is to adjust the amount of air supplied from the tuyere to the combustible gas combustion air using a flow control valve so as to maintain the gas concentration within a set range.

The effects of the characteristic means of the present invention are as follows. In other words, by dividing and supplying air for combustible gas combustion into upper and lower parts, the combustion area of unburned gas can be lengthened vertically, and the combustion speed of unburned gas can be reduced. The flame temperature can be kept low overall and with little variation in the vertical direction. Moreover, since the combustion exhaust gas that does not contain oxygen gas or contains only a small amount of oxygen gas is cooled and supplied above the high-temperature hearth, a direct cooling effect is performed on the combustion exhaust gas, and a dilution effect of the combustion exhaust gas on oxygen-containing gas is achieved. This made it possible to reduce the combustion rate of unburned gas. Furthermore, since the supply amount of the cooled combustion exhaust gas is adjusted to maintain the combustion exhaust gas temperature within the set range, it is possible to reliably prevent the combustion exhaust gas from increasing in temperature. Furthermore, in order to maintain the oxygen gas concentration of the combustion exhaust gas within the set range required for complete combustion, the supply amount of air for combustible gas combustion is adjusted, making it possible to reliably prevent pollution such as air pollution and bad odors caused by the exhaust gas. Since the air for flammable gas combustion is supplied above the high-temperature hearth, the disadvantageous situation where the consumption of carbon-based combustible materials such as expensive caucus increases due to complete combustion of the flammable gas can be sufficiently avoided. It can be prevented. As a result, overall, the flue gas temperature above the high-temperature hearth is controlled to ensure complete combustion of unburned gas and is economically advantageous, while effectively preventing NOx generation and dust adhesion to the furnace inner wall. It became possible to keep it as low as possible.

Next, an example will be shown with reference to FIG.

Coke and industrial waste are alternately or simultaneously opened and closed by double dampers 1a and 1b,
The coke layer supplied from the hopper 2 into the vertical furnace 3 and filled in the lower part of the furnace is combusted by the air supplied from the primary tuyere 4 to form a high-temperature hearth 5. The waste 6 is heated and melted, and the molten material flows down the gap in the high-temperature hearth 5 and is taken out of the furnace from the lower part of the high-temperature hearth 5 through a discharge passage 7.

Most of the combustion exhaust gas rising from the high-temperature hearth 5 is transferred from an exhaust gas path 8 connected to the upper part of the furnace to an exhaust heat boiler 9, a dust removal cyclone 10, an air preheater 11,
It is sent to the desulfurization device 12, the wet dust removal device 13, and the exhaust blower 14 in that order and released into the atmosphere, and
A part of the combustion exhaust gas is passed through the exhaust passage 7 to keep the molten material warm.
released into the atmosphere. The air preheater 11 preheats the combustion air supplied from the blower 15 to the primary tuyere 4 to maintain the temperature of the high-temperature hearth 5 at a high enough temperature to melt the industrial waste. Based on the information from the furnace internal pressure detector 29 at the top of the furnace 3, the controller 30 automatically operates the damper 16 to adjust the furnace internal pressure and appropriately set the combustion exhaust gas supply ratio to the exhaust gas path 8 and the exhaust path 7. That's what I do.

Combustible gas combustion air is supplied to the blower 15 above the high temperature hearth 5 from the secondary tuyere 17 and the tertiary tuyere 18 connected in parallel with the primary tuyere 4 to the upper and lower parts of the furnace 3, The unburned gas from the waste 6 is completely combusted and the combustion exhaust gas is sent to the exhaust gas passage 8, and the combustion of the unburned gas is dispersed throughout the space above the high-temperature hearth 5, and the flame temperature is lowered to increase the furnace temperature. Suppresses internal temperature rise and prevents NOx generation and dust adhesion to the furnace inner wall.

Based on the information from the flow meter 19a, the controller 20a
The flow control valve 21a is automatically operated to maintain the amount of combustion air supplied from the primary tuyere 4 to the high-temperature hearth 5 almost constant, and the flow meter 19 is also automatically operated.
b. By the action of the controller 20b and the flow control valve 21b, the amount of air supplied from the tertiary tuyere 18 for combustible gas combustion is maintained almost constant, and the amount of combustion exhaust gas downstream of the flow meter 19c and the wet dust remover 13 Based on the information from the meter 22 that detects the oxygen gas concentration, the controller 20c automatically operates the flow control valve 21c to adjust the amount of air supplied from the secondary tuyere 17 for combustible gas combustion to the oxygen gas in the combustion exhaust gas. Adjust so that the concentration is maintained within the set range, for example around 2%,
In addition, the overall amount of air supplied should be just the right amount, coke should not be consumed more than necessary, and combustion should be sufficiently carried out in the furnace. In addition, secondary and tertiary tuyere 17, 18
The ratio of air supply from the secondary tuyere 17 is 70 to 80% of the total supply from both tuyeres 17 and 18.
Preferably, 30 to 20% of the amount is supplied from the tertiary tuyeres 18.

The combustion exhaust gas, which has been sufficiently cooled by the wet dust removal device 13, is transferred to the secondary tuyere 17, the primary tuyere 23a for cold exhaust gas directly above it, and the secondary tuyere 23b for cold exhaust gas further above it through a regulating valve. 24a, 24b, 24
c, the flow control valve 28 is automatically operated by the controller 27 based on the information from the flowmeter 25 and the thermometer 26 that detects the combustion exhaust gas temperature near the entrance of the exhaust gas path 8. Then, the total amount of cooled combustion exhaust gas supplied is adjusted so that the temperature detected by the thermometer 26 is maintained within the set range, for example, about 900°C. Prevents dust from adhering to the surface.

In addition, the industrial waste input from Hopper 2 is
For example, sewage sludge, municipal waste incineration ash, tire waste,
They are various things such as waste catalysts, or intermediate processed products thereof.

Next, another example will be shown.

The air for combustible gas combustion may be supplied above the high-temperature hearth 5 at three or more locations above and below the furnace 3, and supply conditions such as the distribution supply position and air distribution ratio may be changed as appropriate depending on the situation. Moreover, the specific means for adjusting the flow rate is not limited.

In order to supply the cooled combustion exhaust gas to the upper part of the high-temperature hearth 5, one or two places above and below the furnace 3, or even four
In order to effectively suppress the local temperature rise of the flame, it is possible to supply the entire amount of air for combustible gas combustion from the same tuyere or from separate tuyeres. When supplying from the same tuyere, the tuyeres may be either upper or lower, and furthermore, the supply amount setting range, the specific means for maintaining it, the collection position of the cooled combustion exhaust gas, etc. can be changed as appropriate. .

In addition to coke, appropriate carbon-based combustible materials such as briquettes such as anthracite and graphite electrode scraps can be used to form the high-temperature hearth.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of an example of an apparatus used in the method of the present invention, and FIG. 2 is a flow sheet of an example of an apparatus used in a conventional method. 3... Furnace, 5... High temperature hearth, 17... Tuyere.

Claims (1)

[Scope of Claims] 1. A high-temperature hearth 5 is formed in the lower part of the furnace by combustion of carbon-based combustible materials, and industrial waste or its intermediate processed material is supplied to the high-temperature hearth 5 and melted. An industrial waste melting method in which the molten material is taken out of the furnace 3 from the lower part of the furnace 3, combustible gas combustion air is supplied above the high-temperature hearth 5, and combustion exhaust gas is discharged from the upper part of the furnace. Tuyeres 17 and 23 arranged at multiple locations above and below the furnace 3 to supply air for gas combustion
a, 23b, and a part of the combustion exhaust gas discharged from the upper part of the furnace to the exhaust gas passage 8 is cooled and then supplied to the upper part of the high temperature hearth 5.
The temperature of the combustion exhaust gas is detected by the thermometer 26, and the amount of cooled combustion exhaust gas supplied to the high temperature hearth 5 is adjusted by the flow rate control valve 28 so as to maintain the detected temperature within the set range. The oxygen gas concentration of the combustion exhaust gas No. 8 is detected by the meter 22, and the amount of air supplied from the tuyere 17 to the combustible gas combustion air is controlled by the flow control valve so as to maintain the detected oxygen gas concentration within the set range. Industrial waste melting method controlled by 21c. 2. The method according to claim 1, characterized in that at least a portion of the cooled combustion exhaust gas is supplied from the same tuyere 17 as at least a portion of the combustible gas combustion air.