JP2000039122A - City garbage gasifying/melting system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable treatment of a large amount of city garbage with a relatively smaller ash melting furnace. SOLUTION: In a city garbage gasifying/melting system which is provided with a circulating fluidized bed type gasifying furnace 1 to gasify city garbage by thermal decomposition and an ash melting furnace 3 to melt incineration residue thereof utilizing a combustion heat of a thermal decomposition gas thereof a gas supply system is so arranged to comprise a supply line 16 with which a part alone of the thermal decomposition gas generated from the gasifying furnace 1 is branched off a discharge port 19a to be guided to the ash melting furnace 3, a cyclone 2a and a supply line 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a municipal waste gasification / melting system and method for combining a gasifier and an ash melting furnace to incinerate municipal waste at a high temperature and melt and treat the residue.

[0002]

2. Description of the Related Art As a next-generation municipal solid waste treatment facility, a gasification and melting system is being developed. In this gasification and melting system, garbage is first steamed and pyrolyzed in a low air-fuel ratio atmosphere at about 500 ° C,
Generate gas. Next, the residue after the thermal decomposition is heated and melted at about 1300 ° C. using the pyrolysis gas as a fuel, thereby processing and processing into a glassy slag.

According to this system, unlike conventional incineration, garbage is decomposed in a high-temperature atmosphere, so that generation of harmful substances such as dioxin and odor is suppressed.
There are advantages such as a high energy recovery rate and easy resource recovery from slag.

FIG. 4 shows the configuration of such a conventional gasification and melting system. This system includes a fluidized bed gasifier 1 and a rotary kiln ash melting furnace 3.

[0005] The municipal solid waste is introduced into the gasification furnace 1 by the supply hopper 10. Combustion and refuse flowing air are introduced into the gasifier 1 through an air supply system 9 to incinerate municipal waste. At this time, by setting the air-fuel ratio λ to less than 1, a gas such as CO or H ₂ is generated by the partial combustion reaction. This generated gas is sent to the cyclone 2 from the gas outlet 19 at the upper part of the gasification furnace 1 by the gas supply line 16, and the fluidized sand and incineration residues contained in the gas are separated, and the gasification is again performed by the return line 22. It is returned to the furnace 1 and only the produced gas is sent to the ash melting furnace 3 by the combustion gas line 17. On the other hand, the ash containing the incineration residue stored in the bottom of the gasification furnace 1 is taken out of the furnace by the extraction device 14, and iron, aluminum, etc. are separated from the ash by the ash / metal separation device 15. Since the inside of the gasification furnace 1 is in a reducing atmosphere, rust-free high-purity metal can be recovered, and recycling can be easily performed. The ash from which the metal content has been removed is sent to the ash melting furnace 3 by the ash transport system 11.

[0006] In the ash melting furnace 3, combustion air is introduced into the generated gas sent from the gasification furnace 1 through a combustion air supply system 8 and burned. As a result, the furnace temperature was reduced to about 1300
C., and the ash is melted in this high temperature atmosphere to form slag. This slag is sent out of the furnace, taken out of the slag reservoir 6, and recycled. On the other hand, the combustion gas is further sent to the secondary combustion furnace 4 and is supplied to the secondary combustion air supply system 13.
, And at the same time, the temperature is increased by the superheater 5 to completely burn the unburned matter. The exhaust gas is sent to an exhaust gas treatment system 12, where the exhaust heat is recovered by a boiler or the like, and a process of removing unnecessary substances in the gas is performed.

[0007]

In systems of this kind, in particular, the insulating properties of ash melting furnaces which produce slag at high temperatures,
It is necessary to keep the heat distribution in the furnace uniform. However, when the entire amount of gas generated in the gasification furnace is supplied to the ash melting furnace as fuel, the ash may be scattered in the ash melting furnace due to the large amount of gas. In order to reduce the flow velocity, it was necessary to increase the cross-sectional area of the ash melting furnace, and the ash melting furnace was enlarged. As a result, it becomes difficult to maintain the heat insulating property and the uniformity of the heat distribution, and the construction cost of the plant increases and the maintenance cost also increases. Further, there is a disadvantage that the energy recovery efficiency is reduced when the size is increased.

Therefore, the present invention has been made in view of the above problems,
It is an object of the present invention to provide a municipal waste gasification and melting system and method capable of treating a large amount of municipal waste with a relatively small ash melting furnace.

[0009]

In order to solve the above-mentioned problems, a municipal solid waste gasification and melting system according to the present invention comprises a circulating fluidized bed gasifier for pyrolyzing municipal solid waste and gasifying the same. An ash melting furnace that melts the incineration residue of the gasification furnace by using the combustion heat of the pyrolysis gas, and in a municipal solid waste gasification and melting system, only a part of the pyrolysis gas generated by the gasification furnace And a gas supply system for introducing the gas into the ash melting furnace.

On the other hand, the method for gasifying and melting municipal solid waste according to the present invention comprises the steps of thermally decomposing municipal solid waste supplied by a circulating fluidized bed type gasifier and gasifying the same; Melting the incineration residue of the furnace by using the heat of combustion of the pyrolysis gas, wherein the municipal solid waste gasification and melting method comprises: It is characterized by being led to.

The present inventors have examined general municipal waste and found that the amount of heat required to heat the entire amount of ash generated by incineration to 1200 ° C. or more, which is its melting point, is the amount of heat that municipal waste itself has. About 1 of about 2400 kcal / kg
It was confirmed that it was about 4%. Therefore, it has been found that the amount of gas supplied to the ash melting furnace can be significantly reduced if only the pyrolysis gas necessary for raising the temperature to a temperature higher than the melting point of the ash is introduced into the ash melting furnace. In the ash melting furnace, it is necessary to keep the gas flow rate in the furnace low in order to prevent the ash from scattering, and the larger the gas supply amount, the larger the sectional area of the furnace, that is, the larger the furnace. In the present invention, the supply of the pyrolysis gas to the ash melting furnace is suppressed, so that the furnace can be downsized.

Further, secondary air inlets for introducing secondary air for combustion may be provided at a plurality of positions at different heights in the gasification furnace. Thereby, the temperature distribution in the gasification furnace is made uniform, and the thermal decomposition reaction proceeds uniformly throughout the furnace.

The gas outlet from the gasification furnace to the gas supply system may be provided in a region of the gasification furnace having a gas temperature of 300 to 500 ° C. In order for the thermal decomposition reaction to proceed,
The gas temperature must be 300 ° C. or higher, and by introducing a relatively low temperature gas of 500 ° C. or lower into the gas supply port, it becomes possible to provide a blower, a flow control valve, and the like in the gas supply system.

The municipal waste gasification and melting system according to the present invention comprises a gasifier, a ash melting furnace, first and second cyclones for separating and removing solids in a gas, and a gasifier. A first gas supply line connecting the first cyclone and the first cyclone provided near the bottom of the gasifier; and a second gas discharge port and a second cyclone provided above the gasifier. A second gas supply line connecting the first and second cyclones, a return line connecting a solid discharge port of each of the first and second cyclones with a solid input port provided at the bottom of the gasification furnace; A combustion gas supply line connecting a gas outlet and a combustion gas inlet of the ash melting furnace, a secondary combustion furnace arranged downstream of the ash melting furnace, a second cyclone gas outlet and a secondary combustion furnace; And a secondary combustion gas supply line for connecting Preferred.

[0015]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. To facilitate understanding of the description, the same reference numerals are given to the same components as much as possible in each drawing.

FIG. 1 is a schematic diagram showing an embodiment of a municipal waste gasification and melting system according to the present invention. First, the structure of this system will be described. The basic configuration is the same as the conventional system shown in FIG.

The fluidized-bed gasifier 1 is provided with a supply hopper 10 for supplying municipal solid waste and an air supply system 9 for supplying air for combustion and flow. Two gas outlets for pyrolysis gas at the bottom
9a and 19b are provided, and an air intake 18 for secondary combustion is provided in the middle part.

A gas outlet 19 at a relatively lower portion of the gasifier 1
a is connected to a cyclone 2a for gas-solid separation, the lower part of the cyclone 2a is connected to a return line 22 to the gasifier 1, and the upper part thereof is a combustion gas supply line. 17 is connected to the ash melting furnace 3 (for example, a rotary kiln type).

On the other hand, the gas outlet 19 in the upper part of the gasifier 1
b is connected to the cyclone 2b by the gas supply line 20, and the lower part of the cyclone 2b is
The upper part of the cyclone 2b is connected to the secondary combustion furnace 4 by the secondary combustion gas supply line 21 in the same manner as the lower part of the cyclone 2b.

The outlet of the ash melting furnace 3 is connected to the upper part of the slag reservoir 6 and is connected to the secondary combustion furnace 4. The secondary combustion furnace 4 is provided with a secondary combustion air inlet 13, the outlet of which is connected to an exhaust gas treatment system 12 (not shown).

Further, the bottom of the gasification furnace 1 is connected to a furnace bottom ash extraction device 14, which is connected to an ash / metal separation device 15. The ash outlet of the ash / metal separator 15 is connected to the ash inlet of the ash melting furnace 3 by the ash transport system 11.

FIG. 2 is a detailed explanatory view of the gas supply line 16. The line 16 includes a heat exchanger 16a for exchanging pyrolysis gas and air flowing in the line 16 and a line 16
An adjustment valve 16b for adjusting the flow rate of the gas flowing through the inside and a blower 16c for forcibly sending the gas to the cyclone 2a are arranged.

Next, a method for gasifying and melting municipal solid waste of the present invention, which is carried out by the system of the present embodiment, will be described with reference to FIGS. FIG. 3 is a graph showing a gas temperature distribution in the gasification furnace 1, and symbols A to D on the horizontal axis of the graph.
Correspond to the positions of the corresponding symbols A to D in FIG.

The municipal solid waste is put into the gasifier 1 through the supply hopper 10, and the air-fuel ratio λ when the waste is used as fuel from the air supply system 10 is less than 1, preferably 0.2 to 0.1.
An amount of air corresponding to 3 is introduced. The air causes the municipal waste to flow in the gasifier 1, and at the same time, partially burns the waste corresponding to the air-fuel ratio. The temperature of the remaining refuse and combustion ash is raised by this combustion heat, and pyrolysis gases such as CO and H ₂ are generated by the pyrolysis reaction. further,
The pyrolysis gas is burned by the secondary combustion air introduced from the air inlet 18, the temperature in the gasification furnace 1 rises, the flow in the furnace is promoted, and the temperature distribution in the furnace is appropriately adjusted. Can be controlled. As shown in FIG. 3, at positions C and D above the air intake 18, the furnace temperature is 1000
Reach nearly ℃. On the other hand, at the lower positions A and B, a relatively low temperature is maintained. However, except for the vicinity of the position A near the refuse inlet, the entire furnace has a thermal decomposition reaction of 300 to 95.
It is 0 ° C. The gas outlet 19a is located in a relatively low temperature area.

A part of the generated pyrolysis gas is extracted from the gas discharge port 19a and led to the cyclone 2a via the gas supply line 16. In the gas supply line 16, as shown in FIG. 2, the combustion air supplied to the ash melting furnace 3 is heated by the heat exchanger 16a. As a result, the pyrolysis gas is once cooled. The amount of the pyrolysis gas flowing into the cyclone 2a can be adjusted by the adjusting valve 16b and the blower 16c.

As described above, the amount of heat required to heat the entire amount of incinerated municipal waste ash to 1200 ° C. or more, which is the melting point, is about 14% of the calorific value of municipal waste of about 2,400 kcal / kg. Therefore, it suffices to supply a sufficient amount of pyrolysis gas to generate this heat. Approximately 40% of the calorific value of municipal waste is used in the pyrolysis reaction in the gasifier 1, and the amount of heat generated when the pyrolysis gas is burned is about 1400 kca per kg of municipal waste.
Therefore, the amount of the pyrolysis gas required to heat the entire amount of the ash above the melting point is about 24% of the total generated pyrolysis gas. In consideration of the difference in the composition of the refuse, the ratio of the pyrolysis gas led to the ash melting furnace 3 is preferably set to about 10% to about 50%.

By cooling the pyrolysis gas with the heat exchanger 16a, it is not necessary to use a device having high heat resistance for the regulating valve 16b and the blower 16c, so that equipment costs and maintenance costs can be reduced. Further, by preheating the combustion air of the ash melting furnace 3, the energy generated from the refuse is not wasted.

In the cyclone 2a, incineration residues mixed in the pyrolysis gas sent and fluidized sand added to promote the flow in the gasification furnace 1 are settled and removed.
The removed incineration residues and the like are returned to the gasification furnace 1 via the return line 22. The pyrolysis gas from which these solids have been removed is led to the ash melting furnace 3 via the supply line 17.

On the other hand, the incineration residue in the gasification furnace 1 is taken out of the gasification furnace 1 by the extraction device 14, and then the ash /
The metal component is removed by the metal separation device 15. Iron, aluminum, etc. mixed in the garbage are reduced in the gasifier 1,
Since paints and the like are decomposed, they can be recovered in a highly pure state, and are easy to recycle. The remaining incineration residue is sent to the ash melting furnace 3 by the ash transport system 11.

In the ash melting furnace 3, a sufficient amount of pyrolysis gas necessary to melt the incineration residue at a high temperature is supplied.
The furnace is burned by the combustion air supplied from the air inlet 8 to keep the furnace temperature at about 1300 ° C. At this time, in the present embodiment, the supply amount of the pyrolysis gas can be significantly reduced as compared with the conventional furnace, so that the size of the furnace itself can be made compact. As a result, it becomes easy to maintain heat insulation and uniformity of heat distribution in the furnace. Furthermore, furnace equipment costs and maintenance costs can be reduced, and maintenance becomes easier.

The incineration residue is melted in the ash melting furnace 3 to be converted into slag, sent to the slag reservoir 6, and collected.
Since the inside of the ash melting furnace 3 is at a high temperature, and harmful substances such as dioxin are thermally decomposed at a high temperature, they are not mixed into the slag. This slag can be used for construction materials and the like.

On the other hand, the gas outlet 19 at the upper part of the gasifier 1
From b, gas corresponding to most of the pyrolysis gas generated in the gasification furnace 1 is discharged and sent to the cyclone 2b by the gas supply line 20. The operation in the cyclone 2b is the same as the operation of the cyclone 2a described above, and the description is omitted. The incineration residue and the like are returned to the gasification furnace 1 via the return line 22, and the pyrolysis gas from which solid matter has been removed
The secondary combustion gas is supplied to the secondary combustion furnace 4 by the secondary combustion gas supply line 21. Then, the pyrolysis gas and the exhaust gas of the ash melting furnace 3 are reburned by the secondary air introduced from the air inlet 13. Since this reburning is performed at a high temperature, no dioxin or the like is generated. The final exhaust gas is sent to an exhaust gas treatment system 12 (not shown) to collect exhaust heat and remove nitrogen oxides and the like.

The pyrolysis gas to be led to the ash melting furnace 3 is not required to be led from the gas discharge port 19a provided in the lower part of the gasification furnace 1,
For example, a line connected to the upper part of the gasification furnace 1 may be branched, or may be branched after the cyclone 2b. In this case, it is not necessary to provide a plurality of cyclones.

The system shown in FIG. 2 is partially or entirely provided with a line 17 between the cyclone 2 a and the ash melting furnace 3.
May be provided.

A plurality of air inlets for secondary combustion in the gasification furnace 1 may be provided at different heights, or in the case of a small furnace capable of adjusting the heat distribution to some extent by the flowing air. May not be provided.

[0036]

As described above, according to the present invention,
Since only the necessary and sufficient amount of pyrolysis gas is supplied to the ash melting furnace, the ash melting furnace can be downsized with respect to the processing amount.
Equipment costs and maintenance costs can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an embodiment of the present invention.

FIG. 2 is a detailed explanatory diagram of a pyrolysis gas supply line of the embodiment of FIG.

FIG. 3 is a graph showing a temperature distribution in a gasification furnace in the embodiment of FIG.

FIG. 4 is an explanatory diagram showing a conventional embodiment.

[Explanation of symbols]

1 gasifier, 2 cyclone, 3 ash melting furnace, 4 2
Next combustion furnace, 10: supply hopper, 11: ash transport system, 15: ash / metal separator, 16: supply line.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigeru Suzuki 63-30 Yuyugaoka, Hiratsuka-shi, Kanagawa F-term in Hiratsuka Works of Sumitomo Heavy Industries, Ltd. (Reference) 3K061 AA07 AA11 AA23 AB02 AB03 AC01 BA01 BA08 CA01 CA07 EA01 EB12 NB03 3K078 AA01 AA08 BA03 BA22 CA02 CA13 4G012 JF03 JG03

Claims (7)

[Claims] 1. A circulating fluidized-bed gasifier for pyrolyzing municipal waste to gasify it, and an ash melting furnace for melting incineration residues of the gasifier using the combustion heat of the pyrolysis gas. A municipal waste gasification and melting system comprising: a municipal waste gasification and melting system comprising a gas supply system for guiding only a part of the pyrolysis gas generated in the gasification furnace to the ash melting furnace. . 2. The municipal waste gasification and melting system according to claim 1, wherein a secondary air inlet for introducing secondary air for combustion is provided at a plurality of positions at different heights in the gasification furnace. . 3. A gas outlet from the gasification furnace to the gas supply system has a gas temperature of 300 to 500 in the gasification furnace.
The municipal solidification gasification and melting system according to claim 1, which is provided in a temperature range of ℃. 4. A circulating fluidized-bed gasifier for pyrolyzing and gasifying municipal solid waste, and an ash melting furnace for melting incineration residues of the gasifier using the combustion heat of the pyrolysis gas. And a first and second cyclone for separating and removing solid matter in a gas, and a first gas outlet provided near a bottom of the gasification furnace. A first gas supply line connecting the first cyclone and a second gas supply line connecting a second gas outlet provided at an upper portion of the gasification furnace and the second cyclone; A return line connecting a solids outlet of each of the first and second cyclones with a solids inlet provided at the bottom of the gasification furnace; a gas outlet of the first cyclone and the ash melting; Combustion gas supply connecting the combustion gas inlet of the furnace A secondary combustion furnace disposed downstream of the ash melting furnace; a gas outlet of the second cyclone; and a secondary combustion gas supply line connecting the secondary combustion furnace. Municipal solid waste gasification and melting system. 5. A step of pyrolyzing and gasifying municipal solid waste input in a circulating fluidized-bed type gasifier, and burning the incineration residue of the gasifier in a ash melting furnace to produce heat of combustion of the pyrolysis gas. Melting the municipal solid waste using the municipal solid waste, the method comprising: guiding only a part of the pyrolysis gas generated in the gasification furnace to the ash melting furnace. Gasification
Melting method. 6. The method according to claim 1, further comprising a step of introducing secondary air from secondary air inlets provided at a plurality of positions at different heights in the gasification furnace to burn gas in the gasification furnace. The method for gasifying and melting municipal solid waste according to claim 5. 7. A gas temperature in the gasification furnace of 300 to 50.
The method for gasifying and melting municipal solid waste according to claim 5, wherein a gas extracted from a gas outlet provided in a region of 0 ° C is guided to the ash melting furnace.