JPH11173520A - Method and device for fluidized bed type thermal decomposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain operation performance of a gasifying and melting system for combustibles contained in various kinds of wastes, such as the municipal refuse, industrial wastes, etc., even when the load of the system becomes smaller than a rated load. SOLUTION: Refuse is pyrolytically gasified in a fluidized thermal decomposition incinerator 2 while a fluid medium is made to flow and steam is generated from a boiler 9 by burning the pyrolytic gas obtained from the furnace 2. The combustion gas is extracted from the halfway of the boiler 9 and introduced to the incinerator 2 after the gas is mixed with fluidized air. During he rated operation of the incinerator 2, the incinerator 2 can maintain good fluidization at a low excess oxygen rate and the temperature of a fluidized bed can be maintained. At a low-load time, in addition, the same fluidization and fluidized bed temperature as those obtained during the rated operation can be maintained by further adjusting the circulating amount of the combustion gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed pyrolysis method and apparatus for combustibles contained in municipal solid waste and / or various wastes using a fluidized bed.

[0002]

2. Description of the Related Art As a method of treating municipal solid waste and various kinds of waste (hereinafter sometimes simply referred to as garbage in the present invention), a furnace such as a fluidized bed type combustion furnace or a stoker type combustion furnace is known. The refuse is burned in the inside, and the obtained exhaust gas and combustion residue are processed in respective processing systems. These conventional refuse incineration facilities have the problem of generating highly toxic dioxin on the exhaust gas side and the problem of shortage of final disposal sites on the combustion residue side, and drastic improvement has been desired.

On the other hand, in recent years, incineration of waste by gasification and melting has been proposed, and fluidized bed, kiln and shaft furnace gasification and melting systems have been studied by leading manufacturers, respectively, and some have been put into practical use. ing. In these techniques, a char consisting of a gas containing a combustible gas and a carbon content is generated in a refuse drying step and a pyrolysis gasification step, and then the char is burned. As a result, high-temperature combustion can be maintained, dioxin is thermally decomposed, and the combustion residue is sufficiently reduced in volume as incineration sludge, and can be reused for roadbed materials and the like.

The outline of a fluidized bed type gasification and melting system for refuse is as follows. The refuse supplied to the fluidized bed pyrolysis gasifier is mixed with a fluid medium such as sand and fluidized using a fluidizing fluid such as air, and reacts with the blown air in a reducing atmosphere. It is gasified and produces flammable pyrolysis gas and solid char. The obtained pyrolysis gas is all burned in a pyrolysis gas combustion furnace or a melting furnace and introduced into an exhaust heat recovery device. Incombustibles such as metals and debris in the garbage (residue from the bottom of the combustion furnace) are extracted from the bottom of the pyrolysis gasifier, and separated from the fluid medium by utilizing the difference in physical properties such as particle size and specific gravity. Is done. Combustible gas, char and fly ash are sent to the ash melting furnace located on the downstream side of the fluidized bed pyrolysis gasifier and used as a heat source, and most of the incombustibles such as fly ash are melted. Is done. The gas after these treatments is purified by an exhaust gas purification device and then released into the atmosphere.

[0005]

However, the above-mentioned conventional waste gasification and melting system has the following problems. The most serious problem is that it is difficult to respond to load fluctuations. The refuse gasification and melting system has a sophisticated heat balance when based on self-combustion by refuse, and it is difficult to maintain its performance at a point other than the rated point. In addition, this system requires a continuous operation for 24 hours over a long period of time, and is not used for so-called quasi-reactor operation in which daily start / stop is performed for the attachment of cold char and solidification of sludge. Not suitable.

[0006] The load fluctuation of the gasification and melting system is not due to the demand from the load side, but to the amount of waste to be incinerated. The amount of waste varies from year to week. Since the installed capacity is determined by assuming the maximum load, the operation is usually performed at a load below the rating. Conventionally, about two to three gasification / melting furnaces are provided for this purpose, and the number of operating gasification / melting furnaces is adjusted to absorb load fluctuations. However, if a plurality of gasification / melting furnaces are installed in parallel, there is a gasification / melting furnace that stops the operation depending on the amount of generated garbage. On the other hand, fluidized bed gasification
The melting furnace can apply a higher hearth load than other conventional incinerators, and may have a smaller facility size per unit waste.

[0007] Therefore, even in a series of gasification and melting furnaces provided with a plurality of furnaces, while maintaining the performance based on the self-combustion of refuse in a load range from a rated load to a load of about 50% or less, for example. If it can be operated, the operation of the gasification and melting system will have a very large cost advantage. This load fluctuation does not fluctuate suddenly as in the demand base, and it is only necessary that a transition between static operating states according to a plan is possible. However, prior art gasification and melting systems have not met such realistic and pressing challenges.

An object of the present invention is to maintain the operation performance of a gasification and melting system for combustibles contained in various wastes such as municipal solid waste and / or industrial waste even when the load becomes smaller than the rated load. It is. Another object of the present invention is to improve the function of a fluidized-bed gasification / melting system and enable stable operation.

[0009]

The present invention has the following construction. (1) a drying step of drying a combustible containing a solid; and a pyrolysis gasification of the combustible while the dried solid is fluidized in a fluidized medium with a fluidizing fluid in a fluidized bed pyrolysis gasifier. A pyrolysis gasification step to be performed; a melting step of melting combustion fly ash by burning the pyrolysis gas obtained in the pyrolysis gasification step and the char generated in the pyrolysis gasification step; A fluidized bed pyrolysis method including a heat recovery step of recovering heat from a combustion gas obtained by burning the char and a heat exchange medium into a heat exchange medium, and an exhaust gas treatment step of purifying exhaust gas that has passed through the heat recovery step, A fluidized bed type pyrolysis method in which a part of the combustion gas is extracted from the middle of the heat recovery step, mixed with a fluidizing fluid for fluidizing a fluidized medium, and introduced into a fluidized bed type pyrolysis gasifier.

(2) In the fluidized bed type pyrolysis method,
The combustion gas extracted from the middle of the heat recovery process is supplied to the drying process, supplied to the empty tower of the fluidized bed pyrolysis gasifier, or the drying process and the empty tower of the fluidized bed pyrolysis gasifier. Fluidized bed pyrolysis method for supplying both.

(3) In the fluidized bed type pyrolysis method,
Two or more solid-gas separators are provided to separate the pyrolysis gas obtained in the fluidized bed pyrolysis gasifier and the solids entrained in the pyrolysis gas, and the amount of combustibles containing solids or the generation of pyrolysis gases A fluidized bed pyrolysis method in which the number of solid-gas separators to be used is selected according to the amount, and the solids separated by the solid-gas separator are used as a heat source in a melting step.

(4) In the fluidized bed type pyrolysis method,
A gas combustion step of burning the pyrolysis gas obtained in the pyrolysis gasification step in accordance with the input amount of the combustible material including the solid matter or the generation amount of the pyrolysis gas by bypassing the melting step and the heat recovery step; And a fluidized bed pyrolysis method for introducing the flue gas cooled in the cooling step into the flue gas treatment step. The apparatus used in the fluidized bed pyrolysis method is also within the scope of the present invention.

[0013]

In one gasification melting system of the present invention,
Exhaust gas is extracted from the waste heat boiler, mixed with fluidized air, and introduced into a fluidized bed pyrolysis gasifier. As a result, in the rated operation, good fluidization can be maintained at a low oxygen excess rate, and the bed temperature can be maintained. Further, when the load is low, by further adjusting the amount of exhaust gas recirculation, fluidization and bed temperature similar to the rated one can be maintained, and the thermal decomposition gasification performance of the refuse does not decrease.

According to the present invention, the combustion gas introduced from the middle of the heat recovery device is further mixed with preheated air introduced into the fluidized bed pyrolysis gasification furnace as a fluidizing fluid of the fluidized medium. When a fluidized fluid is used, the flow rate of the fluidized fluid introduced into the pyrolysis gasifier can be maintained at a high speed suitable for fluidizing the fluidized medium while maintaining a low air-fuel ratio. In addition, the gas flow rate in the empty tower portion in the fluidized bed type pyrolysis gasification furnace is also fast, which makes it possible to form suitable conditions for transporting the char. As described above, in addition to the air introduced into the fluidized bed type pyrolysis gasifier, the combustion gas of the heat recovery device is also mixed with the air and introduced, so that even at a low load, according to each load, By recirculating the planned amount of combustion gas, the performance of pyrolysis gasification of refuse in a fluidized bed pyrolysis gasifier can be sufficiently exhibited.

Further, when a part of the combustion gas obtained by the heat recovery apparatus is recirculated to the fluidized bed pyrolysis gasifier, the recirculated gas injection portion is emptied by the fluidized bed pyrolysis gasifier. In the case of the lower part of the tower, even if the amount of incinerated waste decreases, the gas velocity in the empty tower part is increased, and the solid scattered gas such as a cyclone separator is not dropped. Can be sent out. Thus, even if the amount of generated pyrolysis gas fluctuates due to a decrease in the incineration amount of refuse, solids such as generated char can be reliably sent out to a solid-gas separator such as a cyclone separator, and There is no danger of lowering the efficiency of separating pyrolysis gas and char.

The efficiency of a solid-gas separator such as a cyclone separator is greatly reduced when the gas amount is smaller than the rating. However, when a plurality of the separators are provided, when a large amount of pyrolysis gas is generated, a plurality of the separators are used. When the amount of generated pyrolysis gas is small, the gas can be passed through a small number, and the solid-gas separation efficiency of the separator can be maintained.

Furthermore, unlike the case where air is used for drying the refuse, since the oxygen concentration of the combustion gas is, for example, about 5%, by introducing the combustion gas from the heat recovery device to the refuse drying device, There is no danger of burning refuse, and refuse drying can be effectively performed using the high-temperature combustion gas.

Further, the pyrolysis gas obtained in the pyrolysis gasification step is burned by bypassing the melting step and the heat recovery step in accordance with the input amount of combustible material including solid matter or the generation amount of the pyrolysis gas, and the gas is burned. By cooling the flue gas obtained by combustion and treating the flue gas, the pyrolysis gasifier can be operated even when the equipment that constitutes the gasification and melting system downstream of the pyrolysis gasifier is not operating. Since it can be maintained, the thermal decomposition treatment of refuse, which is the original purpose of the gasification and melting system, can be continued.

Since the waste is measured in advance before being introduced into the apparatus of the present invention, when the amount of waste introduced into the apparatus of the present invention is smaller than the design rated value of the apparatus of the present invention, the above-described combustion of the present invention is performed. The amount of gas circulated to the pyrolysis gasifier can be adjusted according to the amount of waste incineration.

[0020]

Embodiments of the present invention will be specifically described below with reference to the drawings. An outline of the flow of the waste gasification and melting system shown in FIG. 1 will be described. Municipal refuse and / or various wastes (hereinafter, sometimes referred to as garbage) input from a refuse dryer 1 to a fluidized bed pyrolysis gasifier 2 are pyrolyzed by the pyrolysis gasifier 2 to remove char. The pyrolysis gas contained flows toward the furnace top. The pyrolysis gas discharged from the top of the fluidized bed pyrolysis gasification furnace 2 is separated from solids such as char or fly ash which are scattered along with the pyrolysis gas in the cyclone separator 3 and the separated pyrolysis gas Is a fuel source for the cyclone furnace 5 that melts solids such as fly ash together with the char. On the other hand, the incombustibles obtained in the fluidized-bed pyrolysis gasifier 2 are sent to a separation facility 6 to separate recyclables such as metals from rubbles, and the fluidized medium is circulated and supplied to the garbage dryer 1. You.

In the cyclone furnace 5, pyrolysis gas from the cyclone separator 3, char from the char service hopper 7, fly ash, and fly ash collected by the heat recovery section downstream of the slag boiler 9 and the bag filter 15 are provided. Is supplied, and the fly ash is melted by the pyrolysis gas and char and, if necessary, the auxiliary fuel. The combustion gas obtained in the cyclone furnace 5 is supplied to the superheater 10 and the evaporator 1 in the slag boiler 9.
1. After being used for heat exchange of the fluid by the air preheater 12 and the economizer 13, the dust is removed by the bag filter 15, and the purified gas is discharged from the chimney 16 into the atmosphere.

The waste gasification / melting system of FIG. 1 having the above-described schematic structure will be described in detail. The refuse roughly crushed by the crusher (not shown) is introduced into the great refuse dryer 1 via the double damper 19. Here, the refuse is sequentially transferred forward while the height of the refuse layer is leveled by an oscillating grate. During this transfer, the moisture is reduced to about 50% by weight by hot air supplied from the bottom of the refuse dryer 1. The garbage contained has a water content of about 30 to 2
Dry to 0% by weight. Then, it is charged into the fluidized bed pyrolysis gasifier 2 while being air-sealed by a feeder 20 composed of a screw type conveyor and a rotary valve.

In the system shown in FIG. 1, the slag boiler 9
Hot air (* 2HA in FIG. 1) of about 300 ° C. from an air preheater 12 installed in the inside is supplied to the refuse dryer 1 for refuse drying. In this case, it is necessary to maintain hot air (preheated air) for drying the dust at a temperature at which the dust does not ignite.

The preheated air after the refuse drying step is sent to a cooler 23 after a solid content is separated by a cyclone 21. Since the moisture content of the preheated air after the refuse drying step is increased, the preheated air is once cooled by the cooler 23 to collect the drain. If the preheated air is not cooled, the corrosive components contained in the preheated air will corrode the devices that make up the air flow path,
Such corrosive components are collected in the drain by cooling. The preheated air discharged from the refuse dryer 1 after being cooled is returned to the cyclone furnace 5, and is effectively used as combustion air.

Although the odor of the refuse is mixed in the air from the refuse drying machine 1, the cyclone furnace 5 in the high temperature region is used.
The odor can be decomposed by returning the odor, and the odor can be prevented from flowing to the outside.

A pipe grid type air diffuser 24 is provided in the fluidized bed type pyrolysis gasifier 2, and a fluid medium made of sand or the like is fluidized by a fluidizing fluid ejected from the air diffuser 24. Garbage is pyrolyzed. Under the condition that the air-fuel ratio is about 0.1 to 0.3 in the fluidized bed pyrolysis gasifier 2, the crushed refuse is pyrolyzed by the fluidizing fluid, and the generated pyrolysis gas, char and fly ash are generated. It is taken out from the top of the fluidized bed pyrolysis gasifier 2. The pyrolysis gas containing no char varies depending on the composition of the refuse and the like, but an example in which slaked lime described below is not added into the pyrolysis gasifier 2 shows the following components and their content ratio (% by weight). ) And its calorific value was 1,066 kcal / kg. _{CO 12.4; CH 4 8.4; N} 2 22.7; H 2 O 50.2; CO 2 6.2; Cl 2 200ppm

[0027] Further, combustion residues (also referred to as furnace bottom residues) such as metals and incombustibles and a fluid medium are discharged from the furnace bottom of the pyrolysis gasifier 2 by a noncombustible material / fluid medium extracting device 25 and separated by a separation facility 6. By this, it is separated into recyclable materials such as metals, rubbles and fluid media.

One of the features of the present invention is that the fluid medium is conveyed to the refuse dryer 1 by means of air flow, for example, by an inert gas, or circulated by a transfer conveyor. About 300 ° C supplied to the dryer 1
Is supplied to the refuse dryer 1 and becomes a heat source for drying the refuse.

The preheated air (* 2HA in FIG. 1) obtained at about 300 ° C. obtained by the air preheater 12 is introduced into the fluidized-bed pyrolysis gasifier 2 to obtain a fluidized bed having a low air-fuel ratio. Can compensate for the lack of heat of reaction in the reactor. In general, the air-fuel ratio of the pyrolysis gasification furnace 2 is very low, such as 0.1 to 0.3, and the pyrolysis gasification of combustibles in the refuse is performed.

According to the present invention, when the amount of waste incineration decreases, the preheated air introduced into the pyrolysis gasifier 2 is supplied to the slag boiler 9 by about 400 to 450 on the downstream side of the air preheater 12.
By mixing a combustion gas at 1 ° C. (* 1GR in FIG. 1) into a fluidized fluid, the flow rate of the fluidized fluid from the air diffuser 24 can be reduced while maintaining a low air-fuel ratio. Can be maintained at a high speed suitable for Further, the present invention is characterized in that the gas flow velocity in the empty tower portion in the fluidized bed type pyrolysis gasification furnace 2 is similarly fast, and conditions suitable for transporting the char can be formed.

That is, when the amount of waste input decreases and the amount of waste incinerated falls below the rated value, a pyrolysis gasifier is used to maintain an air-fuel ratio (about 0.1 to 0.3) for pyrolysis gasification. The amount of preheated air flowing into the fluidized bed 2 is also reduced. Therefore, the fluidizing gas velocity for fluidizing a solid material consisting of a fluid medium such as sand and refuse in the fluidized bed pyrolysis gasifier 2 is reduced. Not only is it not possible to sufficiently fluidize the solids, but also the superficial velocity of the gas in the superficial section decreases, and ash etc. are deposited on the fluidized bed, increasing the height of the fluidized bed. As a result, the thermal decomposition of combustibles cannot be performed sufficiently.

Therefore, when the amount of waste is reduced, the flue gas from the slag boiler 9 is mixed and introduced into the preheated air introduced into the air diffuser 24 to increase the fluidized gas velocity of the solid and increase the solid matter. Promote gasification of
By increasing the superficial velocity of the gas in the superficial tower, it is possible to easily extract the pyrolysis gas accompanying the ash and the char to the cyclone separator 3.

As described above, in addition to the preheated air introduced into the diffuser 24, the combustion gas of the slag boiler 9 is also mixed and introduced into the preheated air, so that the amount of waste that is measured in advance in the present system is small. Even when the incineration amount becomes lower than the rated value, fluidization is performed by recirculating the previously planned amount of combustion gas from the slag boiler 9 to the diffuser pipe 24 of the gasifier 2 according to each incineration amount. Conditions can be ensured, and the performance of pyrolysis gasification of refuse in the fluidized bed pyrolysis gasifier 2 can be maintained.

At this time, the operation when the amount of waste incineration is reduced will be specifically described. The air-fuel ratio in the pyrolysis gasifier 2 is maintained at 0.3. When the incineration amount is 100%, 200 to the diffuser 24 of the pyrolysis gasifier 2
℃ preheated air is introduced in the amount of air per unit time (Qa), the gas temperature of the empty tower is 600 ℃, the unit time introduced into the air diffuser 24 when the amount of waste incineration is reduced to 50% Assuming that the amount of preheated air per unit is 1/2 Qa and the amount of exhaust gas per unit time is Qg, the following equation (1) is established based on the relationship shown in Table 1 below.

[0035]

[Table 1]

V _g ′ = v _ga + v _gg (1) where v _g = Qa × (600 + T) / (200 + T) / A (2) v _ga = １ ／ × Qa × (550 + T) / (200 + T) / A (3) v _gg = Q _g × (550 + T) / (450 + T) / A (4) A = cross-sectional area of the pyrolysis gasifier 2, T = 273. Q _g = Q _g1 + Q _g2 (5)

[0037] In Table, being equal v _g 'and v _g, equivalent substance transport performance transport. In the equation (1), v _ga is obtained from the equation (3). Although v _gg is obtained from equation (4), Q _g is unknown. Q _g is represented by equation (5),
Q _g1 on the right side is defined as supplementing the minimum flow rate for fluidization that is insufficient for 1/2 Qa. Therefore, Q _g2
Is an unknown, and Q _g2 is obtained by sequentially solving the above equations.

Similarly to the preheated air recirculated to the fluidized bed pyrolysis gasifier 2, the combustion gas of the slag boiler 9 needs to be pressurized to a pressure higher than that required for fluidizing the fluidized medium. And the combustion gas is supplied to the recirculation fan 27.
Is boosted.

The fluidized bed pyrolysis gasification furnace 2 contains:
A desalinating agent such as slaked lime is added from the empty tower. As in the following formula (6), the chlorine component contained in the refuse or the like can be fixed as calcium chloride by slaked lime. Ca (OH) ₂ + 2HCl → CaCl ₂ + 2H ₂ O (6)

Since this reaction proceeds at an optimum temperature of 500 to 700 ° C., the temperature is adjusted so that the inside of the fluidized bed pyrolysis gasification furnace 2 enters this temperature range. This temperature adjustment is performed by controlling the supply amount of preheated air from the air diffuser 24 and the amount of recirculated combustion gas mixed with the preheated air.

Since the concentration of chlorine in the composition of the pyrolysis gas generated in the fluidized bed pyrolysis gasifier 2 is about 200 ppm, about 3 to 3 parts per million of the hydrogen chloride generated from the chlorine component.
A desalinating agent such as 5 mol of slaked lime is added into the fluidized bed pyrolysis gasifier 2. Here, in place of the slaked lime, other desalting agents, for example, quick lime, magnesium hydroxide, caustic soda, caustic potash and the like may be used.

The pyrolysis gas, scattered char and fly ash generated in the fluidized bed pyrolysis gasifier 2 are supplied to the cyclone separator 3 from the top of the pyrolysis gasifier 2.
The reaction of the above formula (1) proceeds even from the fluidized bed type pyrolysis gasifier 2 to the cyclone separator 3. Since the pyrolysis gas contains an alkali component (calcium, sodium, potash, etc.), not only the calcium component from slaked lime added as the desalting agent but also the desalination reaction proceeds with the alkali component. Particularly, since the pyrolysis gas is agitated in the cyclone separator 3, the contact efficiency between the alkali component accompanying the pyrolysis gas and the chlorine component generated from refuse or the like is good, and the reaction of the above formula (1) and the similar formulas. The reaction between the alkaline component and the chlorine component is effectively performed. According to the actually measured value, the concentration of hydrogen chloride in the gas at the inlet of the cyclone separator 3 was 200 ppm, but the concentration in the gas at the outlet of the cyclone separator 3 was reduced to 50 ppm or less.

Hydrogen chloride concentration in pyrolysis gas is 50 ppm
Below, the corrosiveness of the gas is of little concern. Therefore, the combustion gas of about 1400 ° C. obtained by burning the pyrolysis gas in the cyclone furnace 5 as a fuel source does not corrode the heat transfer tubes such as the superheater 10.

A desalinating agent such as slaked lime may be added to the cyclone separator 3. Fluidized bed pyrolysis gasifier 2
The pyrolysis gas generated in step (1) is sent to the cyclone separator 3, where it is gravity-sorted into a gas component consisting of the pyrolysis gas and an ash-char mixture consisting of fly ash and char entrained by the pyrolysis gas. Therefore, the char falls and is stored in the char service hopper 7. The char service hopper 7 has a certain capacity, and by storing the char in advance, the fluctuation of the incineration amount of refuse can be absorbed.

On the other hand, the pyrolysis gas separated by the cyclone separator 3 is introduced into a cyclone furnace 5 which is a combustor of the slag boiler 9. On the other hand, the ash / char mixture is also supplied from the char service hopper 7 to the cyclone furnace 5.
Then, the pyrolysis gas and the char are both burned to a high temperature in the cyclone furnace 5 because they are sent by air using the blower 28. Since the char separated by the cyclone separator 3 has high purity and is stored in the char service hopper 7 in an amount equal to or greater than a predetermined amount, even if the incineration amount of refuse fluctuates, melting of the ash in the cyclone furnace 5 And stable combustion energy can be supplied.

As described above, once the char is stored in the char service hopper 7, the cyclone furnace 5 is
And the system after the slag boiler can be operated independently of the fluidized bed pyrolysis gasifier.

For example, during maintenance or failure of the system after the cyclone furnace 5 and the slag boiler 9, the fluidized bed pyrolysis gasifier 2 at the preceding stage may be kept operating, and the char generated at this time is supplied to the char service hopper 7. You can save it. Further, when the operation of the fluidized bed pyrolysis gasification furnace 2 at the preceding stage is stopped, the charcoal stored in the char service hopper 7 can be used to operate the cyclone furnace 5 and the system after the slag boiler 9.

The pyrolysis gas in the cyclone furnace 5 and the combustion gas of about 1400 ° C. generated by the combustion of the char pass through the screen tubes 29 to the downstream side of the boiler 9 where the heat exchangers in the slag boiler 9 are installed. Be guided. on the other hand,
The ash becomes a melt in the furnace of the cyclone furnace 5,
It falls via a lower spout (not shown). The molten solids entrained by the combustion gas are also cooled by the screen tube 29, become liquid, and travel down the screen tube 29 to fall. The dropped melt falls into a water-sealed tank 31 and becomes quenched slag. This is extracted from the tank bottom and reused as a resource.

On the other hand, the combustion gas obtained in the cyclone furnace 5 generates superheated steam by heating a superheater 10 in a slag boiler 9, and the superheated steam is used for driving a steam turbine 32 to generate a generator 33. To generate electricity. Next, the combustion gas sequentially heats the evaporator 11, the air preheater (air heater) 12, and the economizer 13, and enters an exhaust gas treatment step.

Here, as described above, in the example shown in FIG.
The combustion gas in the slag boiler 9 downstream of the air preheater 12 is extracted and recirculated to the fluidized bed pyrolysis gasifier 2.
The combustion gas temperature in this case is about 400 to 450 ° C. The temperature of the recirculated gas can be predetermined depending on the location where the gas is extracted from the boiler 9.

The gas whose temperature has dropped to about 200 ° C. or lower from the slag boiler 9 is collected by the bag filter 15 after the chlorine content in the gas is fixed by a desalinating agent such as slaked lime. In the bag filter 15, combustion fly ash is also collected.
Dioxin generated by the chlorine component is almost completely suppressed in the cyclone furnace 5 and the slag boiler 9 under a high-temperature atmosphere, but the dioxin is generated between the outlet of the furnace 5 or the boiler 9 and the bag filter 15. The dioxin to be resynthesized is removed by the bag filter 15, and the remaining dioxin and heavy metal components, which are traces of adding activated carbon to the gas, are removed.

The purified gas component discharged from the bag filter 15 is sent to the chimney 16 by the induction ventilator 36 and discharged to the atmosphere. Note that the combustion fly ash collected by the bag filter 15 is returned to the cyclone furnace 5 by pneumatic transportation and melted together with the combustion fly ash collected by the heat recovery device after the boiler by pneumatic transportation.

In FIG. 1, a damper 38 provided in a combustion gas flow path or an air flow path maintains an air heat ratio of 0.1 to 0.3 and fluidization conditions for pyrolysis when the amount of waste incineration falls below a rated value. Is controlled to open and close.

FIG. 2 is an embodiment of another waste gasification and melting system according to the present invention. The same devices as those described in the system shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The system is different from the system shown in FIG. 1 in the following three points. The first point is that a part of the combustion gas (* 1GR) obtained in the slag boiler 9 is recirculated to the fluidized bed pyrolysis gasifier 2, and the recirculation gas injection part is connected to the diffuser 24.
In addition to mixing with the preheated air (* 2HA) introduced into the furnace, it is also introduced into the lower part of the empty tower of the fluidized bed type pyrolysis gasification furnace 2. In the system according to the present invention, which uses relatively fine sand as a fluid medium in the fluidized bed pyrolysis gasifier 2 and allows the fluid medium to flow with a small amount of air (air-fuel ratio: 0.1 to 0.3), If the incineration amount of the refuse is lower than the rated value, there arises a problem that the char and fly ash generated in the fluidized bed pyrolysis gasifier 2 cannot be efficiently entrained on the gas side. Therefore, in order to cope with such a case, the recirculated combustion gas from the slag boiler 9 is injected into the lower portion of the empty tower portion of the fluidized bed type pyrolysis gasifier 2 as well as the diffuser tube 24 to evacuate the air. By increasing the gas velocity in the tower, the char on the layer can be scattered and sent to the cyclone separator 3.

Thus, even if the amount of generated pyrolysis gas fluctuates due to the amount of incineration below the rated value of the refuse, solids such as generated char can be reliably sent out to the cyclone separator 3. There is no danger of lowering the efficiency of separating pyrolysis gas and char.

The second difference between the system shown in FIG. 2 and the system shown in FIG. 1 is that a plurality of cyclone separators 3 are provided. If the rated gas amount is smaller than the rated gas, the efficiency of the cyclone separator 3 is greatly reduced. Therefore, it is conceivable to increase the gas recirculation amount to prevent the gas amount below the rated gas amount. There is also the above problem, and it is not possible to increase the gas recirculation amount due to only the solid-gas separation efficiency of the cyclone separator 3.
Therefore, as shown in FIG. 2, a plurality of cyclone separators 3, for example, two as shown, are installed, and the damper 38 is opened and closed. When the generation amount of the decomposition gas is small, the gas is passed through one unit so that the solid-gas separation efficiency of the cyclone separator 3 can be maintained. Thus, by installing a plurality of cyclone separators 3, it is possible to cope with a wide range of loads.

A third difference between the system shown in FIG. 2 and the system shown in FIG. 1 is that the recirculated exhaust gas (* 1 GR) from the slag boiler 9 is also introduced into the refuse dryer 1. .

Unlike the case where air is used for drying refuse, by using a recirculation gas having an oxygen concentration of, for example, about 5% from the slag boiler 9, the recirculation gas is reduced to 450%.
Garbage drying can be performed using a high temperature fluid of about ° C. The higher the temperature of the drying fluid, the higher the efficiency of refuse drying. However, by using the recirculated exhaust gas (* 1GR) of about 450 ° C. from the slag boiler 9, the refuse drying is performed in the present invention. Done effectively.

At this time, as in the system shown in FIG. 1, air of about 300 ° C. from the air preheater 12 obtained by the slag boiler 9 can be used together with the recirculation gas for drying the refuse. In this case, it is necessary to maintain the preheated air for drying the refuse at a temperature at which the refuse does not ignite.

The preheated air is also used as fluidized air in the pyrolysis gasifier 2 and combustion air in the cyclone furnace 5. Since the size of the air preheater 12 to be installed may be too large, the balance may be lacking as a whole system. But,
The above problem can be reduced by using the recirculated gas in combination with the preheated air for drying the refuse.

Although the water content in the recirculated gas is low and suitable for refuse drying, the water content increases after the refuse drying step. As a result, the corrosive components contained in the gas, when not cooled, corrode the flow path and the device through which the gas flows, but such corrosive components are collected in the drain by cooling. Further, the recirculated gas discharged from the refuse dryer 1 after cooling has a low oxygen partial pressure, and therefore is returned to the empty tower of the slag boiler 9.

FIG. 3 shows a flow chart of the pyrolysis gasification and melting system shown in FIG.
1 and a gas cooling device 42, and a system path for allowing exhaust gas discharged from the gas cooling device 42 to flow into exhaust gas treatment equipment such as the bag filter 15.

By providing a flow path for the pyrolysis gas including the gas combustion furnace 41 and the gas cooling device 42 (42a, 42b) shown in FIG. 3, the cyclone furnace 5 and the downstream device can be maintained or maintained. In the event of a failure, by opening / closing an appropriate damper 38 with the pyrolysis gas discharged from the pyrolysis gasification furnace 2, the operation for reducing the operation rate of the cyclone furnace 5 and the apparatus downstream thereof can be continued or stopped. Thus, the operation of the apparatus on the side of the pyrolysis gasifier 2 can be continued.

As the gas combustion furnace 41, any type of gas furnace may be used as long as it can burn ordinary combustible gas. The pyrolysis gas is burned in the gas combustion furnace 41 to obtain an exhaust gas of about 1200 ° C. The exhaust gas is cooled by the gas cooling device 42.

The cooling device 42 is preferably divided into a pre-cooling device 42a and a post-cooling device 42b to sequentially dilute the exhaust gas. In the pre-stage cooling device 42a, the exhaust gas is diluted with air until the exhaust gas is cooled to approximately 450 ° C. to obtain an exhaust gas (* 3GR) of approximately 450 ° C., which is supplied to the diffuser tube 24 of the pyrolysis gasification furnace 2. The use of a mixture with the preheated air to be introduced (* 2HA), as described with reference to FIG. 1, particularly for maintaining the fluidized state of the fluidized medium of the pyrolysis gasifier 2 when the incineration amount is reduced. The same effect can be obtained. On the other hand, the char collected by the cyclone 3 is stored in the hopper 7.

The exhaust gas is further diluted with air in the post-stage cooling device 42b to obtain an exhaust gas cooled to a temperature of about 250 ° C.
5 and the like.

Here, the exhaust gas discharged from the post-stage cooling device 42b is reduced to about 2
The amount (Qg) of the exhaust gas discharged from the post-cooling unit 42b per unit time (Qg) in order to keep the temperature of about 00 ° C. and to maintain the gas capacity balance of the pyrolysis gasification and melting system It is necessary to keep it below the gas capacity allowed in the melting system. here,
Since the exhaust gas processing capacity has a sufficient margin when burning only the pyrolysis gas, the system can be inexpensively constructed by performing dilution by mixing air as a gas cooling device.

Further, about 4% obtained by the pre-stage cooling device 42a
When the exhaust gas at 50 ° C. (* 3GR) is introduced into the diffuser 24 of the pyrolysis gasification furnace 2, the fluidized bed is maintained in the pyrolysis gasification furnace 2 and the charcoal in the empty tower is maintained. ash is accompanied by pyrolysis gas flow rate of the exhaust gas necessary to flow from the gasification furnace 2 (material-conveying gas flow rate: v _g ') is the same as described in FIG.

Further, the air preheater 12 is used in place of the pre-cooler 42a to obtain about 120
The exhaust gas at 0 ° C. may be processed by the air preheater 12 and further passed through the post-stage cooling device 42b, and then processed by the exhaust gas processing equipment.

FIG. 4 shows the gasification and melting system shown in FIG.
A flow path through which a pyrolysis gas containing is added.
In this case, the exhaust gas (* 3G.
R. 2) is supplied to the air diffuser 24 or the empty tower of the pyrolysis gasification furnace 2 as in the case shown in FIG. 2, and the other part of the exhaust gas is introduced into the refuse dryer 1.

In the gasification and melting system according to the embodiment of the present invention shown in FIGS. 1 to 4, when any of the devices constituting the system is maintained, when it is out of order, and / or when the amount of waste incineration is reduced. In such a case, it is necessary to keep the cyclone furnace 5 in operation as much as possible. Once the operation of the cyclone furnace 5 at a high temperature of about 1400 ° C. is temporarily stopped, it is not only long time is necessary to restart the cyclone furnace 5 at the same high temperature state, but also the molten ash solidifies, In some cases, melting is impossible.

The operation of the cyclone furnace 5 is maintained in the following manner. First, the ash is normally melted by the pyrolysis gas from the pyrolysis gasification furnace 2 and the heat of combustion by the char accompanying the pyrolysis gas and the char from the char service hopper 7. Furnace 2
When the pyrolysis gas and the char from the fuel are not supplied to the cyclone furnace 5, the molten state of the ash is maintained by using the char and the auxiliary fuel stored in the char service hopper 7. Next, when the amount of the molten ash in the cyclone furnace 5 further decreases, the ash is kept molten using a smelt spout burner (not shown) provided in the furnace 5. Also, the operation of the cyclone furnace 5 is stopped only when the molten ash is exhausted.

As described above, according to the present invention, a compact municipal waste gasification and melting system can be realized as compared with the prior art.
Locational and economical benefits are high. Further, according to the present invention, the combustion gas obtained in the slag boiler 9 is recirculated to the fluidized-bed pyrolysis gasifier 2 to reduce the air-fuel efficiency of the fluidized-bed pyrolysis gasifier 2 to 0.1 or less. Can be operated with very few values. The resulting gas has a high flammable content and contains almost no combustion gas such as CO ₂ . At the same time, the recovery of carbon as char is improved, and a system with extremely good thermal efficiency can be obtained.

Further, according to the present invention, it is possible to operate in a wide load range according to the amount of waste by using technologies such as gas recirculation and operation of a plurality of cyclone separators 3.
There is no need to build excess equipment. As a result, since the construction area is small, it is possible to add it to the existing incineration equipment, so that narrow land can be effectively used.

When the recirculated gas is introduced into the empty tower of the fluidized bed type pyrolysis gasifier 2, the good char is conveyed to the gas side. Further, according to the present invention, since the recirculated gas can be used for the drying step in the dryer, the size of the air preheater can be made relatively compact, and a system can be constructed without increasing the height of the boiler.

[0077]

According to the present invention, a compact waste pyrolysis / melting system can be realized, which has a high locational and economical advantage, and can be used without deteriorating the performance even when the amount of waste incineration is relatively small. Can be operated.

[Brief description of the drawings]

FIG. 1 is a flow diagram of an overall fluidized bed pyrolysis system according to an embodiment of the present invention.

FIG. 2 is a flow diagram of an overall fluidized bed pyrolysis system according to another embodiment of the present invention.

FIG. 3 is a flow chart of an overall fluidized bed pyrolysis system according to an embodiment of the present invention.

FIG. 4 is a flow diagram of an overall fluidized bed pyrolysis system according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Garbage dryer 2 Fluidized bed pyrolysis gasifier 3 Cyclone separator 5 Cyclone furnace 6 Separation equipment 7 Char service hopper 9 Slag boiler 10 Superheater 11 Evaporator 12 Air preheater 13 Energy saving device 15 Bag filter 41 Gas combustion furnace 42 Gas cooling equipment

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23G 5/30 ZAB F23G 5/30 ZABB ZABE 5/46 ZAB 5/46 ZABZ 5/50 ZAB 5/50 ZABE ZABQ ZABK F23J 1/00 F23J 1/00 / 00 B 15/06 15/00 K (72) Inventor Shuji Mori 1-2-10 Isogo, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Babcock Hitachi, Ltd. Yokohama Engineering Center (72) Inventor Takashi Morimoto Kure-shi, Hiroshima No. 6-9, Takaracho Inside Kure Factory, Babcock Hitachi Co., Ltd. (72) Inventor Manabu Manabu 3-36, Takaracho, Kure City, Hiroshima Pref.

Claims (19)

[Claims] 1. A drying step of drying a combustible containing a solid, and pyrolyzing the combustible while fluidizing the dried solid with a fluidizing fluid in a fluidized bed pyrolysis gasifier. A pyrolysis gasification step of gasification, a melting step of melting the combustion fly ash by burning the pyrolysis gas obtained in the pyrolysis gasification step and the char generated in the pyrolysis gasification step, A fluidized bed thermal decomposition method including a heat recovery step of recovering heat from a combustion gas obtained by combustion of a cracked gas and a char into a heat exchange medium, and an exhaust gas treatment step of purifying an exhaust gas that has passed through the heat recovery step. Fluidized bed pyrolysis characterized in that a part of the combustion gas is extracted from the middle of the heat recovery process, mixed with a fluidizing fluid for fluidizing the fluidized medium, and introduced into a fluidized bed pyrolysis gasifier. Method. 2. Combustion extracted from the middle of the heat exchange step using air as a heat exchange medium used in the heat recovery step, using air preheated in the heat recovery step as a fluidizing fluid for fluidizing the fluid medium. The fluidized bed pyrolysis method according to claim 1, wherein a gas is premixed with the preheated air and used as the fluidized fluid. 3. The fluidized bed according to claim 1, wherein the amount of combustion gas from the heat recovery step introduced into the fluidized bed pyrolysis gasifier is adjusted according to the amount of combustibles containing solids. Thermal decomposition method. 4. The method according to claim 1, wherein air is used as a heat exchange medium used in the heat recovery step, and the air preheated in the heat recovery step is used for drying combustibles including solids in the drying step. The fluidized bed pyrolysis method as described in the above. 5. The fluidized medium obtained by separating recyclable materials and rubbles from the fluidized medium discharged from the bottom of a fluidized bed pyrolysis gasifier is supplied to a drying step. The fluidized bed pyrolysis method as described in the above. 6. One or more solid-gas separators for separating a pyrolysis gas obtained in a fluidized-bed type pyrolysis gasification furnace and a solid matter entrained in the pyrolysis gas are provided. 2. The fluidized bed type pyrolysis method according to claim 1, wherein the solid material is used as a heat source in the melting step. 7. A drying step of drying a combustible containing a solid, and pyrolyzing the combustible while fluidizing the dried solid with a fluidizing fluid in a fluidized bed pyrolysis gasifier. A pyrolysis gasification step of gasification; a melting step of melting the combustion fly ash by burning the pyrolysis gas obtained in the pyrolysis gasification step and the char generated in the pyrolysis gasification step; A fluidized bed pyrolysis method comprising a heat recovery step of recovering heat from a combustion gas obtained by burning gas and char to a heat exchange medium, and an exhaust gas treatment step of purifying exhaust gas that has passed through the heat recovery step. The combustion gas extracted from the middle of the heat recovery step is supplied to the drying step, supplied to the empty tower of the fluidized bed pyrolysis gasifier, or the drying step and the fluidized bed pyrolysis gasifier are evacuated. Characterized by supplying to both tower sections Fluidized bed pyrolysis method. 8. The amount of combustion gas from a heat recovery step for supplying to an empty tower of a fluidized bed pyrolysis gasifier according to the amount of combustibles containing solids is adjusted. The fluidized bed pyrolysis method as described in the above. 9. A drying step of drying a combustible containing a solid, and pyrolyzing the combustible while fluidizing the dried solid with a fluidizing fluid in a fluidized bed pyrolysis gasifier. A pyrolysis gasification step of gasification; a melting step of melting the combustion fly ash by burning the pyrolysis gas obtained in the pyrolysis gasification step and the char generated in the pyrolysis gasification step; A fluidized bed pyrolysis method comprising a heat recovery step of recovering heat from a combustion gas obtained by burning gas and char to a heat exchange medium, and an exhaust gas treatment step of purifying exhaust gas that has passed through the heat recovery step. And two or more solid-gas separators for separating the pyrolysis gas obtained in the fluidized-bed pyrolysis gasifier and the solids entrained in the pyrolysis gas, and the amount of the combustibles containing the solids or the pyrolysis The solid-gas separator used according to the amount of gas generated Select the number, fluidized bed pyrolysis process, wherein the solids separated in the solid gas separator to a heat source of the melting step. 10. A drying step for drying a combustible material containing a solid matter, and the combustible material containing the dried solid matter is fluidized by a fluidizing fluid in a fluidized bed pyrolysis gasifier with a fluidizing fluid. A pyrolysis gasification step of pyrolyzing the material
A melting step of melting the combustion fly ash by burning the pyrolysis gas obtained in the pyrolysis gasification step and the char generated in the pyrolysis gasification step; and burning the pyrolysis gas and the char. A fluidized bed type pyrolysis method comprising: a heat recovery step of recovering heat from a combustion gas to a heat exchange medium; and an exhaust gas treatment step of purifying exhaust gas that has passed through the heat recovery step, wherein the amount of combustible material including solid matter Alternatively, a gas combustion step in which the pyrolysis gas obtained in the pyrolysis gasification step is burned by bypassing the melting step and the heat recovery step according to the amount of generated pyrolysis gas, and cooling of the combustion exhaust gas obtained in the gas combustion step A fluidized bed type pyrolysis method, comprising: introducing a combustion exhaust gas cooled in the cooling step to an exhaust gas treatment step. 11. The fluidized-bed type pyrolysis gasifier according to claim 10, wherein the gas obtained in the cooling step is mixed with a fluidized fluid for fluidizing the fluidized medium and introduced into a fluidized-bed pyrolysis gasifier. Pyrolysis method. 12. A gas obtained in the cooling step is supplied to a drying step, a gas is supplied to an empty column of a fluidized-bed pyrolysis gasifier, or a drying step and a fluidized-bed pyrolysis gasifier are performed. The fluidized bed type pyrolysis method according to claim 10, wherein the mixture is supplied to both of the empty towers. 13. A drying apparatus for drying a combustible material including a solid matter, and a fluidizing fluid supply unit, wherein the combustible material is fluidized by a fluidizing fluid supplied from the fluidizing fluid supply unit. Fluidized-bed pyrolysis gasifier for pyrolyzing and gasifying the pyrolysis gas, and pyrolysis gas obtained in the fluidized-bed pyrolysis gasification furnace and char generated in the pyrolysis gasification step to burn combustion ash. A melting furnace for melting; a heat recovery device for recovering heat to a heat exchange medium from a combustion gas obtained by burning the pyrolysis gas and char in the melting furnace; and an exhaust gas purification for purifying exhaust gas discharged from the heat recovery device A fluidized bed type pyrolysis apparatus provided with a device, wherein a gas flow path for supplying combustion gas extracted from the heat recovery apparatus to fluidized fluid supply means of a fluidized bed type pyrolysis gasification furnace is provided. Fluidized bed pyrolysis equipment. 14. The heat recovery apparatus is provided with an air preheater for preheating air used as a fluidizing fluid of a fluidized bed type pyrolysis gasifier, and the air preheated by the air preheater is supplied to the fluidized bed type pyrolysis gas. Providing a preheating air flow path for supplying to the fluidizing fluid supply means of the gasification furnace, and combining the preheating air flow path and the gas flow path for supplying the combustion gas extracted from the heat recovery device to the fluidizing fluid supply means. 14. The fluidized bed pyrolysis apparatus according to claim 13, wherein: 15. An air preheater for preheating air used as a fluidizing fluid in a fluidized bed pyrolysis gasifier in a heat recovery device, and a preheater for supplying air preheated by the air preheater to a drying device. 2. An air flow path is provided.
4. A fluidized bed type pyrolysis apparatus according to 3. 16. A supply path for supplying a drying device with a fluidized medium after separating resources and rubbles in a fluidized medium discharged from a furnace bottom of a fluidized bed pyrolysis gasification furnace is provided. The fluidized bed pyrolysis apparatus according to claim 13, wherein: 17. A fluidized bed pyrolysis gasifier for drying a combustible containing solid matter, a fluidized bed pyrolysis gasifier for fluidizing a fluidized medium while fluidizing a fluidized medium, and the fluidized bed pyrolysis gasifier. A melting furnace for melting the combustion fly ash by burning the pyrolysis gas and the char generated in the pyrolysis gasification step; and a heat exchange medium from the combustion gas obtained by burning the pyrolysis gas and the char in the melting furnace. Fluidized bed type pyrolysis apparatus equipped with a heat recovery device for recovering heat to the air and an exhaust gas purification device for purifying exhaust gas discharged from the heat recovery device, wherein the combustion gas extracted from the heat recovery device is supplied to a drying device. A fluidized bed type pyrolysis apparatus comprising a gas flow path and / or a gas flow path for supplying to an empty tower of a fluidized bed type pyrolysis gasification furnace. 18. A fluidized bed pyrolysis gasifier for pyrolyzing and gasifying a combustible containing solids while fluidizing a fluidized medium, a pyrolysis gas obtained by the fluidized bed pyrolysis gasifier, and A melting furnace for melting the combustion fly ash by burning the char generated in the pyrolysis gasification step, a heat recovery device for burning the pyrolysis gas and the char in the melting furnace and recovering heat to a heat exchange medium; A fluidized bed type pyrolysis apparatus provided with an exhaust gas purifying apparatus for purifying exhaust gas discharged from a recovery apparatus, wherein a pyrolysis gas obtained in a fluidized bed pyrolysis gasifier and a solid entrained in the pyrolysis gas Two or more solid-gas separators are provided to separate the solid components, and the number of solid-gas separators to be used can be selected according to the amount of pyrolysis gas generated. Featured a solids supply path used as a heat source Fluid bed pyrolyzer for. 19. A fluidized bed pyrolysis gasifier for pyrolyzing and gasifying combustibles containing solids while fluidizing a fluidized medium, a pyrolysis gas obtained by the fluidized bed pyrolysis gasifier, A melting furnace for melting the combustion fly ash by burning the char generated in the pyrolysis gasification step, a heat recovery device for burning the pyrolysis gas and the char in the melting furnace and recovering heat to a heat exchange medium; A fluidized bed type pyrolysis device equipped with an exhaust gas purification device that purifies exhaust gas discharged from the recovery device.The pyrolysis gas obtained in the fluidized bed type pyrolysis gasification furnace bypasses the melting furnace and the heat recovery device. A fluidized bed type pyrolysis apparatus comprising: a gas combustion furnace for performing combustion by burning; and one or more air mixers for diluting exhaust gas obtained in the gas combustion furnace with air.