JPH08121727A - Secondary combustion furnace structure for melting furnace of wasted matter - Google Patents

Abstract

PURPOSE: To reduce the amount of air for combustion, prevent ash from fusing trouble and compact facilities such as a boiler, a dust collector, a smoke washing device and the like by providing a secondary combustion furnace of a boiler type, which burns gas produced from a melting furnace. CONSTITUTION: In a device, recovering waste heat by burning gas, produced from the waste melting furnace 1 of a shaft furnace type, in a secondary combustion furnace 12, a combustion burner 27 is installed at the upper part of the secondary combustion furnace 12 so as to be faced downwardly, the upper furnace body inner wall of the secondary combustion furnace 12 is constituted of a refractory wall to make a high-temperature combustion area, the central part of the furnace body wall is constituted of a boiler wall and the lower part of the furnace body inner wall is constituted of a refractory wall to make a complete combustion area. In another way, the combustion burner 27 is installed at the upper part of the secondary combustion furnace 12 so as to be faced downwardly, the inner wall of the upper furnace body of the secondary combustion furnace 12 is constituted of a refractory wall to make the high-temperature combustion area, the central part and the lower part of the furnace body wall are constituted of the boiler wall and a flue, constituted of a refractory wall, is connected to the lower part of the furnace body to make the complete combustion area.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is obtained by using a lumpy carbonaceous combustible substance such as coke as a heat source, municipal waste, sewage sludge, various industrial wastes, or their dehydration, drying, incineration, crushing treatment, or the like. The present invention relates to a melting furnace that heats and melts an intermediate processed product and recovers it as a civil engineering material, a concrete fine aggregate, and a slag material for surface makeup aggregate.

[0002]

2. Description of the Related Art In order to melt-treat such waste, a coke-mixed waste is charged from the top of a shaft furnace, and an oxygen-containing gas or an oxygen-enriched gas is blown into the furnace from a tuyere to produce coke. And carbonaceous matter generated by thermal decomposition in a high-temperature hearth at a high temperature, and sequentially descends in the dry zone, carbonization gasification zone and combustion melting zone in the furnace to form molten slag. The melting furnace in which the waste packed bed in the inside is raised as a countercurrent flow and recovered as a combustible gas is disclosed in Japanese Examined Patent Publication No. 52-24790, Japanese Unexamined Patent Publication No. 60-23714 and Japanese Unexamined Patent Publication No. 05-3405.
No. 20 publication.

A secondary combustion furnace for the gas generated from the melting furnace is disclosed in Japanese Patent Application Laid-Open No. 56-127110. The first disclosed technology mentioned above is to inject a gas containing 40% or more of oxygen into the waste to recover the gas, the molten slag, and the molten metal.

The second one is good melting of industrial waste and intermediate products thereof, such as incineration ash of waste and fine dust collected from a melting furnace, while preventing troubles due to dust scattering. It is designed so that it can be processed.
The third is a technology that recovers dust in raw gas and supplies it to a secondary combustion furnace for combustion in a fixed amount. The fourth one is a secondary combustion furnace composed of refractory walls, in which the directions of ejection holes for gas and combustion air are devised.

However, when the gas generated from the melting furnace is burned in the secondary combustion furnace, it is necessary to completely burn it while controlling the temperature of the combustion gas to be equal to or lower than the softening melting temperature of ash.

That is, if the ash is burned at a temperature higher than the softening / melting temperature of the ash, troubles such as ash fusion on the furnace wall of the secondary combustion furnace occur. Therefore, conventionally, a method has been adopted in which the combustion exhaust gas temperature of the secondary combustion furnace is excessively supplied and diluted with air to lower the combustion exhaust gas temperature.

However, the method of diluting with air has a drawback in that the amount of combustion exhaust gas increases, so that the dust collector after the combustion furnace, the smoke washing device, the exhaust gas suction blower, and the building equipment become large.

However, no method for solving these problems by the conventional disclosed technology has been presented. That is, the above-mentioned first disclosed technology describes the operating conditions of the melting furnace main body, and the above-mentioned second and third disclosed technologies collect the dust discharged from the melting furnace. However, the technique for blowing the gas into the melting furnace or the secondary combustion furnace again is provided, but the technique for the secondary combustion of the gas generated from the melting furnace is not provided.

Furthermore, the fourth disclosed technique relates to the gas and combustion air supply holes of the secondary combustion furnace, and does not provide a technique for reducing the amount of exhaust gas.

[0010]

Generally, when a waste material is melt-processed, the heat generation amount of the gas generated from the melting furnace changes due to a change in the quality of the waste. That is, the gas generated in the melting furnace contains combustible gas and combustible dust, but the amount of heat generation varies depending on the nature of the waste to be treated. Especially, the fluctuation amount of combustible dust is large.

However, it is impossible to predict in advance the change in the calorific value of the generated gas, and unlike other combustion equipment, the amount of air required for combustion cannot be calculated in advance and supplied to the secondary combustion furnace. Therefore, the combustion gas temperature is measured and the temperature is usually adjusted to 800 to 1050 ° C. That is, when the combustion gas temperature is 800 ° C. or lower, unburned matter remains in the exhaust gas, and when it is 1050 ° C. or higher, the ash is softened and melted and fused to the combustion furnace wall.

Under these conditions, the problem to be solved by the present invention is to reduce the amount of combustion exhaust gas by burning the gas generated from the melting furnace without diluting it with an excess of combustion air.

In the conventional secondary combustion furnace, as shown in FIGS. 5 and 6, the furnace wall of the secondary combustion furnace 12 is composed of a refractory wall 15. Gas generated in the melting furnace is supplied into the secondary combustion furnace 12 through the gas discharge pipe 6 and the gas pipe 11 from the gas ejection hole 23, and combustion air passes through the air supply pipe 13 and the air ejection hole 24 through 2 It is supplied into the next combustion furnace. Scraper 25 for removing dust accumulated in the pipe
And a drive device 26 is provided.

When the excess combustion air is reduced by such a conventional technique, the temperature of the combustion exhaust gas rises, and problems such as ash contained in the gas being fused to the furnace wall occur. Therefore, it is necessary to lower the combustion exhaust gas temperature below the ash fusion temperature while reducing the combustion air.

Further, in the secondary combustion furnace having the structure shown in FIG. 5, since the air and the generated gas are discharged in the inner circumferential direction, the combustion flame collides with the furnace wall, and the ash melted in the high temperature part of the flame center is generated. Problems such as fusion with the furnace wall tend to occur.

When the calorific value of the generated gas fluctuates in a state where the combustion air is reduced, for example, when the calorific value rapidly increases, the combustion air amount becomes insufficient due to the delay of the combustion control. Therefore, when reducing the combustion air, it is necessary to stabilize the fluctuation of the heat generation amount.

[0017]

[Means for Solving the Problems] Means for characterizing the present invention for solving the above-mentioned problems is to combust gas generated from a shaft furnace type waste melting furnace in a secondary combustion furnace to generate waste heat. In the apparatus designed to recover, a combustion burner is installed downward on the upper part of the secondary combustion furnace, and the inner wall of the upper furnace body of the secondary combustion furnace is constituted by a refractory wall to form a high temperature combustion zone.
The central part of the furnace body wall is composed of a boiler wall, and the lower part of the furnace body wall is composed of a refractory wall to form a complete combustion zone.

Alternatively, a combustion burner is installed downward on the upper part of the secondary combustion furnace, and the upper inner wall of the secondary combustion furnace is constituted by a refractory wall to form a high temperature combustion region, and the central part of the furnace body wall is formed. The lower part is composed of a boiler wall, and the lower part of the furnace body is connected to a flue composed of a fireproof wall to form a complete combustion zone.

[0019]

According to the present invention, the central portion of the secondary combustion furnace for the generated gas of the melting furnace is constituted by the boiler wall instead of the conventional refractory wall, and the combustion gas is cooled to blow excess combustion air. It is possible to reduce the amount of flue gas because it can be combusted without being burned. That is, when the combustion air is reduced, the combustion gas temperature rises, but the elevated temperature is cooled by the boiler wall installed on the wall of the combustion chamber.

The refractory wall is, for example, a furnace wall made of a heat insulating brick or castable refractory inside a furnace wall made of steel plate, and a refractory brick or castable refractory inside the furnace wall. The wall is a furnace wall in which boiler tubes are arranged side by side like a wall, or a boiler tube is arranged inside a refractory wall along the wall to form like a wall.

Further, by composing the combustion furnace with the boiler wall, troubles such as ash fusion can be prevented. That is, unlike a fire wall, the boiler wall is a cold metal wall, so the fused ash is immediately cooled and falls off the wall. The ash that has peeled off is discharged from under the furnace.

Further, according to the present invention, a combustion flame is formed downward by installing a burner at the upper part of the secondary combustion furnace and burning it downward, and since it is formed in parallel without colliding with the furnace wall, the flame is formed. The high temperature area in the center does not directly collide with the furnace wall.

Therefore, the semi-molten ash in the high temperature region of the flame does not fuse to the wall. Further, since the gas pipe for supplying the generated gas connected to the burner faces downward or obliquely downward, there is no problem of blockage due to dust in the gas, and a cleaning device in the pipe is unnecessary.

Further, the gas generated in the melting furnace contains combustible gas and combustible dust, and as described above, the amount of heat generated varies depending on the nature of the waste to be treated, and particularly the amount of combustible dust varies. If the calorific value rapidly increases under a small amount of combustion air, the combustion air amount will be insufficient due to delay in combustion control, and problems such as incomplete combustion will occur, thus stabilizing fluctuations in the calorific value. It is necessary. For that purpose, the combustible dust in the generated gas is collected, temporarily stored in the hopper, and supplied in a constant amount, so that the variation in the calorific value of the generated gas is made uniform.

Further, in the present invention, by installing a high temperature combustion zone constituted by a refractory wall in the upper part of the secondary combustion furnace, when the calorific value of the generated gas fluctuates, the temperature fluctuation is mitigated by the heat storage effect of the refractory material. And burns stably. Further, since a high temperature region composed of a refractory wall is formed in the upper part of the combustion furnace, unburned dust and the like are completely burned.

In the present invention, the unburned component in the combustion exhaust gas is completely combusted by installing the flue constructed by the refractory wall at the lower part of the secondary combustion furnace or at the outlet of the combustion chamber.

Furthermore, according to the present invention, by composing the furnace wall at the center of the secondary combustion furnace for combusting the gas generated in the melting furnace by the boiler wall, the combustion gas in the combustion furnace is different from the conventional method. Since the temperature is high, the combustion exhaust gas temperature in the boiler as a whole of the boiler in the combustion furnace and the boiler in the downstream of the combustion furnace can be raised on average, so the heat transfer area can be reduced and the boiler can be made compact. Can be That is, in the conventional method, the temperature at the inlet of the boiler is 850 ° C., whereas in the present invention, the temperature in the combustion furnace of the boiler system is 1050 to 850 ° C., and the inlet temperature of the downstream boiler is 850 ° C. Yes, the average gas temperature is high because the boiler gas temperature in the combustion furnace is high. Furthermore, since the amount of combustion exhaust gas can be reduced, equipment such as a dust collector, a smoke washing device, and a blower can be made compact. Furthermore, civil engineering and building equipment for these mechanical equipment can be made compact.

It is also possible that the central part and the lower part of the combustion furnace are composed of boiler walls, and the flue composed of the refractory wall is installed in the lower part of the furnace body to form a complete combustion zone. This method requires a flue of a refractory wall, but considering the system as a whole, it is compact and economically advantageous.

[0029]

EXAMPLE FIG. 1 shows an example in which coke was used as a lumpy carbonaceous combustible substance.

In FIG. 1, waste, coke and lime are charged into the melting furnace 1 from a charging device 4 provided at the upper part of the melting furnace 1. Air supply pipe 3a and oxygen supply pipe 3 connected to tuyeres 2 provided around the lower part of melting furnace 1.
Air and oxygen are respectively supplied through b. The air and oxygen supply amounts are adjusted by an air flow rate control valve 22a and an oxygen flow rate control valve 22b, respectively.

A part of the combustibles of coke and waste is burned inside the melting furnace 1, and the ash and non-combustibles are heated to a high temperature to be in a molten state and discharged from the slag discharge hole 5 to the outside of the furnace. . Gas and dust generated in the melting furnace are discharged from a gas discharge pipe 6 provided at the top of the melting furnace 1.

The gas discharge pipe 6 is provided with a dust collecting device 7 for collecting the dust in the gas, temporarily storing the collected dust in the storage tank 8 and then disconnecting it from the cutting device 9. The secondary combustion furnace 1 is discharged and passes through the dust supply pipe 10.
2 is supplied. In addition, this embodiment is an example in which a mechanical transfer device such as a screw conveyor is adopted as a dust supply device. Dust collector 7 and storage tank 8
It is possible to make the fluctuations of unburned dust uniform by such means.

On the other hand, the gas passing through the dust collecting device 7 is supplied to the secondary combustion furnace 12 through the gas pipe 11. The upper and lower parts of the secondary combustion furnace 12 are constituted by a boiler wall 14, and the central part thereof is constituted by a fireproof wall 15. The temperature of the combustion exhaust gas flowing into the lower part constituted by the fireproof wall 15 in order to completely burn the unburned components in the combustion exhaust gas is set to 800 to 1050.
Approximately ℃. Further, since the flame does not come into direct contact with the refractory wall, trouble such as ash fusion does not occur.

Combustion air is supplied to the secondary combustion furnace 12 from the air supply pipe 13a, and is mixed with gas and combustible dust and burned in the furnace.

The combustion exhaust gas passes through the boiler 16, the exhaust heat is recovered, the exhaust gas pipe 17, the dust collector 18 and the smoke washing device 19 remove dust and pollutants, and the blower 20. , Discharged from the chimney 21.

FIG. 2 shows the secondary combustion furnace of the present invention. A burner 27 is installed above the secondary combustion furnace 12, and the generated gas and unburned dust are supplied from the gas pipe 11 and the dust supply pipe 10. A central portion of the combustion furnace is constituted by a boiler wall, and an upper portion thereof is provided with a high temperature combustion zone constituted by a refractory wall 15. Further, a zone constituted by a refractory wall is provided in the lower part of the combustion furnace, and the temperature of the combustion gas flowing into this zone is usually 800 ° C. or higher. In this example, a zone lined with refractory was provided at the bottom of the secondary combustion furnace.
FIG. 3 shows an embodiment in which the central part and the lower part of the secondary combustion furnace 12 are constituted by boiler walls, and the flue for discharging combustion exhaust gas to the lower part of the combustion furnace is constituted by the refractory wall 15.

FIG. 4 shows the heat removal rate (heat removal amount / sensible combustion exhaust gas sensible heat × 100) of the boiler of the secondary combustion furnace, the oxygen concentration in the combustion exhaust gas, and the combustion exhaust gas amount (exhaust gas amount of the present invention / exhaust gas amount of prior art × 100). ) Is a graph showing the carbon monoxide concentration (ppm) in the exhaust gas. The lower heating value of waste is 2500
This is the case of kca1 / kg. In the prior art, the oxygen concentration in the combustion exhaust gas is about 13%, but if the excess air for combustion is reduced to make the oxygen concentration in the combustion exhaust gas 6%, the combustion exhaust gas amount will be almost halved (57%). The heat removal rate in this case is 4
2%, and the concentration of carbon monoxide in the exhaust gas is 10 pp
There is no problem as low as m.

Further, if the rate of heat removal is increased to make the oxygen concentration in the combustion exhaust gas 5%, the concentration of carbon monoxide in the exhaust gas increases due to the shortage of combustion air. The rate of heat removal decreases as the heat value of waste decreases. Considering the fluctuation of the waste quality, it is advisable to remove heat so that the oxygen concentration in the combustion exhaust gas is 6 to 8%.

[0039]

According to the present invention, the following effects can be realized.

(1) By composing the central portion of the furnace wall of the secondary combustion furnace for burning the generated gas of the melting furnace with the boiler wall, the ash is fused to the combustion temperature without supplying excessive combustion air. It can be suppressed to a temperature equal to or lower than the temperature. Therefore, the amount of combustion exhaust gas can be reduced.

(2) By installing a burner at the upper part of the secondary combustion furnace and burning it downward, a combustion flame is formed downward and is formed in parallel without colliding with the furnace wall, so that the flame central portion is formed. The high temperature area of the will not directly collide with the furnace wall. Therefore, the semi-molten ash in the high temperature region of the flame does not fuse to the wall. Further, since the gas pipe for supplying the generated gas connected to the burner is directed downward or obliquely downward,
There is no problem of blockage due to dust in the gas, and there is no need for a cleaning device in the piping.

(3) By installing a high-temperature combustion zone composed of a refractory wall in the upper part of the secondary combustion furnace, when the calorific value of the generated gas fluctuates, the temperature fluctuation is alleviated by the heat storage effect of the refractory and the temperature is stable. And burn. Further, since a high temperature region composed of a refractory wall is formed in the upper part of the combustion furnace, unburned dust and the like are completely burned.

(4) By constructing the lower part of the secondary combustion furnace that combusts the gas generated in the melting furnace with a refractory wall, it is possible to completely burn unburned components in the combustion exhaust gas.

(5) By composing the furnace wall of the secondary combustion furnace for combusting the gas generated in the melting furnace with the boiler wall, the combustion exhaust gas temperature in the boiler can be increased on average as compared with the conventional method. Therefore, the boiler can be made compact.

(6) By constructing the furnace wall of the secondary combustion furnace that combusts the gas generated in the melting furnace by the boiler wall, the amount of combustion exhaust gas can be reduced, and therefore the equipment such as the dust collector, the smoke washing device, and the blower can be made compact. You can Furthermore, civil engineering and building equipment for these mechanical equipment can be made compact.

(7) By forming the furnace wall of the secondary combustion furnace that combusts the gas generated in the melting furnace by the boiler wall, troubles such as ash fusion can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 shows a secondary combustion furnace of the present invention.

FIG. 3 shows another embodiment of the present invention.

FIG. 4 is a graph showing the heat removal rate of the boiler of the secondary combustion furnace, the oxygen concentration in the combustion exhaust gas, the combustion exhaust gas amount, and the carbon monoxide concentration in the exhaust gas.

FIG. 5 shows a conventional secondary combustion furnace.

FIG. 6 shows a conventional secondary combustion furnace.

[Explanation of symbols]

1 Melting Furnace 2 Tuyere 3a Air Supply Pipe 3b Oxygen Supply Pipe 4 Charging Device 5 Slag Discharge Hole 6 Gas Discharge Pipe 7 Dust Collection Device 8 Storage Tank 9 Cutting Device 10 Dust Supply Pipe 11 Gas Pipe 12 Secondary Combustion Furnace 13a Air supply pipe 13b Air supply pipe 14 Boiler wall 15 Fireproof wall 16 Boiler 17 Exhaust gas pipe 18 Dust collector 19 Smoke cleaning device 20 Blower 21 Chimney 22a Air flow rate control valve 22b Oxygen flow rate control valve 23 Gas ejection hole 24 Air ejection hole 25 Scraper 26 Drive Equipment 27 burners

Claims (2)

[Claims] 1. A device for recovering waste heat by combusting a gas generated from a shaft furnace type waste melting furnace in a secondary combustion furnace so that a combustion burner faces downward in the upper part of the secondary combustion furnace. Along with the installation, the upper furnace body wall of the secondary combustion furnace is constituted by a refractory wall to form a high temperature combustion zone, the central portion of the furnace body wall is constituted by a boiler wall, and the lower portion of the furnace body wall is a refractory wall. The secondary combustion furnace structure of the waste melting furnace, which is characterized by being configured as a complete combustion zone. 2. An apparatus in which a gas generated from a shaft furnace type waste melting furnace is burned in a secondary combustion furnace to recover waste heat, and a combustion burner is directed downward on the upper part of the secondary combustion furnace. Along with the installation, the upper furnace body wall of the secondary combustion furnace is composed of a refractory wall to form a high temperature combustion area, the central part and the lower part of the furnace body wall are composed of a boiler wall, and the lower part of the furnace body has a refractory wall. A secondary combustion furnace structure for a waste melting furnace, characterized in that the flue configured by is connected to form a complete combustion zone.