WO1998023898A1

WO1998023898A1 - Method and equipment for gasification and burning of solid waste

Info

Publication number: WO1998023898A1
Application number: PCT/JP1997/004314
Authority: WO
Inventors: Shosaku Fujinami; Kazuo Takano; Masaaki Irie; Tetsuhisa Hirose; Takahiro Oshita; Yasuo Makino
Original assignee: Ebara Corporation
Priority date: 1996-11-26
Filing date: 1997-11-26
Publication date: 1998-06-04
Also published as: JPH10160141A; AU5191698A

Abstract

A method and equipment for gasification and burning of solid waste in which the solid waste is subjected to thermal decomposition and gasification at 450°-650 °C in a fluidized bed of a fluidized bed gasification furnace, the resultant waste being subjected to melt combustion at 1200°-1500 °C in a melt combustion furnace in a subsequent stage, whereby the ash is turned into fused slag. At least one of oxygen, vapor and air is selected as a gas supplied to the fluidized bed in the fluidized bed gasification furnace. The quantity of oxygen in the gas supplied to the fluidized bed is set to 10-30 % of a quantity of theoretical combustion oxygen. The following whirling movements of a fluidized medium are generated. The fluidized medium flows down as it is fluidized in a slow fluidized bed in a central portion of a furnace bottom, flows up as it is fluidized in an active fluidized bed in a peripheral portion of the furnace bottom, flows from a central portion to a peripheral portion in a lower portion of the fluidized bed and from a peripheral portion to a central portion in an upper portion of the fluidized bed as the fluidized medium is fluidized, and flows from a central portion to a peripheral portion in the lower portion of the fluidized bed as the fluidized medium is fluidized. The melt combustion furnace is of a whirling flow type.

Description

Specification

Gasification combustion method and equipment for solid waste

(Technical field)

The present invention gasifies and combusts solid waste such as municipal solid waste, solidified fuel, slurried fuel, waste plastic, waste FRP, biomass waste, automobile waste, low-grade coal, waste oil, etc. The present invention also relates to a method and equipment for converting ash contained in waste into molten slag. Here, the solidified fuel includes what is referred to as RDF, which is obtained by crushing and sorting municipal solid waste, adding quicklime, etc., and compression-molding. Slurried fuel includes municipal solid waste that has been crushed and turned into a water slurry, and turned into oil by hydrothermal decomposition under high pressure. F R P stands for fiber reinforced plastic. Biomass waste includes water and sewage waste (contaminants, sewage, sewage sludge), agricultural waste (rice husk, rice straw, surplus products), forest waste (sawdust, bark, thinned goods), and industry Includes waste (pulp chip dust) and construction waste. Low-rank coal includes peat with a low degree of coalification, or the buttons generated during coal cleaning.

(Background technology)

At present, various companies are competing for the development of a `` gasification combustion system '' that combines gasification and high-temperature combustion as a new environmental conservation type waste treatment technology that replaces the conventional waste incineration method. Some are. The common features of these "gasification combustion systems" are as follows.

(i) Exhaust gas volume is greatly reduced by low air ratio combustion.

(ii) Dioxins and furans are hardly generated by high-temperature combustion.

(Ii) Ash in the waste is collected as harmless slag from which heavy metals do not elute. This will extend the life of the landfill and make it possible to use it for roadbed materials.

(iv) The energy held by the gas, tar, and carbides generated by gasification can be effectively used as a heat source for ash melting.

(V) By incorporating dioxin treatment and ash melting functions into the system, the entire system is compacted and the construction cost is lower than if each function were added to conventional incineration equipment.

The background to the emergence of these technologies is as follows. (a) Dealing individually with problems such as dioxin and ash melting will inevitably increase the construction cost of the treatment facility divided by the operating cost.

(b) An urgent solution is needed in response to the tightening of dioxin regulations expected in the near future.

(c) The need for ash melting has rapidly increased in order to extend the life of landfills that are becoming increasingly scarce and to make ash harmless and recycle.

(d) It has become desirable to create a system that maximizes the energy held by waste.

At present, the development of “gasification combustion system” is ahead of the others, using a vertical furnace as the gasification furnace (vertical furnace method) and a method using a rotary furnace (rotary furnace method). In the vertical furnace method, the drying and preheating zone (200 to 300 ° C), the pyrolysis zone (300 to 100 ° C), the combustion and melting zone (15 (Above 0 ° C) is formed in layers sequentially from the top, and the waste and coke introduced from the upper part of the furnace descend in the furnace while exchanging heat with the gas generated in the lower zone. The generated gas that has risen inside the furnace is burned at about 900 ° C in the subsequent combustion furnace. The carbide generated in the pyrolysis zone descends into the melting and combustion zone together with the charged coke, and is burned at a high temperature by the oxygen-enriched air supplied from the tuyere to melt the entire amount of incombustibles including metals. In the rotary furnace method, waste is crushed and then supplied to a drum type rotary furnace externally heated by high-temperature air, where it is slowly pyrolyzed to gas at about 450 ° C. The resulting char is discharged from the furnace and cooled to a temperature where it does not ignite. Thereafter, the carbide is finely pulverized and supplied to the subsequent rotary melting furnace, where it is burned at a high temperature of 130 ° C. together with the gas produced from the rotary furnace, and the ash is turned into molten slag.

The problems of these two methods are described. The vertical furnace requires auxiliary materials such as coke and oxygen-enriched air because the melting zone reaching 170 to 180 ° C is located at the bottom of the gasification furnace, and the operating cost is high. There is also a problem that the use of coke etc. increases the amount of carbon dioxide emissions. Furthermore, since almost all of the metal in the waste is melted, it cannot be recycled as bullion for each type of metal. The vertical furnace belongs to the type of fixed bed furnace as a gasification furnace, but it is stable because it stacks various types of waste in layers and has a combustion and melting zone at the bottom. Driving is difficult. In fixed-bed furnaces, it is important to ensure uniform air permeability. In the case of forces and wastes, this is difficult due to the variety of shapes, and gas blow-through and drift often occur. Addition of coke is effective in ensuring uniform air permeability, but it is still difficult to suppress fluctuations in the gas flow rate in the fixed-bed furnace and fluctuations in the furnace pressure. Gases containing dioxins / furans and their precursors generated in the pyrolysis zone are discharged from the vertical furnace without passing through the melting / combustion zone. These dioxins, furans and their precursors are not easily decomposed only by the subsequent combustion furnace.

—On the other hand, in the rotary furnace system, the gasification furnace is an externally heated rotary furnace using high-temperature air, so the furnace size cannot be avoided. In addition, there is a problem in heat transfer through the metal pipe, and tar and undecomposed products generated by thermal decomposition cover the heat transfer surface, so that heat transfer is deteriorated. In addition, it is difficult to obtain high-temperature air at about 600 ° C by exchanging heat with the exhaust gas from the furnace. The generated carbide is discharged from the rotary furnace, pulverized and then supplied to the melting and burning furnace, where it is combined with the gas supplied directly from the rotary furnace and melted and burned. For this reason, carbide handling equipment such as discharge, cooling, crushing, storage, and supply is required. During such handling, the loss of heat from the carbides due to cooling and heat dissipation is also undesirable for energy use. If the carbide is discharged outside without cooling, it is dangerous because it ignites in contact with air.

In both the vertical furnace method and the rotary furnace method, since the substantial gasification temperature is low, it is inevitable that the tar content with a slow burning rate increases in the generated gas.

(Disclosure of the Invention)

An object of the present invention is to solve the above-mentioned problems, and to provide a method and equipment for gasifying and burning solid waste, which is easy to operate, has excellent safety, is compact and has high thermal efficiency. Other objects and advantages of the present invention will be apparent in the drawings, the description of the embodiments, and the appended claims.

The present invention is based on the above-described rotary furnace system, and uses a fluidized-bed gasification furnace and a melt-burning furnace (fluidized-bed furnace system), and transfers solid waste to the fluidized-bed portion of the fluidized-bed gasification furnace. Pyrolysis gasification at 450-650 ° C, followed by melt-combustion at 1200-150 ° C in a subsequent melting and burning furnace to convert ash into molten slag gas In the combustion process. In the gasification combustion method of the present invention, one or more gases selected from oxygen, water vapor, and air are supplied to the fluidized bed, and the amount of oxygen in the gas supplied to the fluidized bed is calculated as 1% of the theoretical combustion oxygen. 0 to 30%, and a relatively slow fluidized bed is formed at the center of the furnace bottom, where the fluidized medium flows down while flowing in the fluidized bed. A relatively active and rising fluidized bed is formed, and the fluidized medium moves from the central part to the peripheral part while flowing at the lower part of the fluidized bed, and the fluidized medium moves from the peripheral part to the central part while flowing at the upper part of the fluidized bed. In this way, the swirling motion of the fluidized medium is generated so that the area ratio of the slow fluidized bed in the cross section of the fluidized bed is 40 to 60%, and the mass velocity of the fluidized gas in the slow fluidized bed is the minimum fluidized mass velocity. 2 to 6 times, and the mass velocity of the fluidizing gas in the Includes a step of 1.5 to 3 times the mass velocity of the fluidizing gas in the slow fluidized bed. Further, the gasification combustion method of the present invention can include the following configuration.

Ml: At least one gas selected from oxygen, water vapor, and air is supplied to the free-bed of the fluidized-bed gasifier, and the carbide and tar generated in the fluidized-bed are separated by the free-board. The amount of oxygen in the gas to be pyrolyzed and gasified at 650 to 850 ° C and supplied to the free board unit is set to 0 to 20% of the theoretical combustion oxygen amount of solid waste.

M 2: An inclined wall is provided along the inner wall near the surface of the fluidized bed of the fluidized bed gasifier, and the upward flow of the fluidized medium at the periphery of the fluidized bed is turned to the center to promote the swirling motion of the fluidized medium. Let it. The downward projected area of the inclined wall shall be 25 to 40% of the cross section of the fluidized bed, and the inclination angle of the inclined wall with respect to the horizontal plane shall be 30 to 60 °.

M 3: One or more gases selected from oxygen, water vapor, and air are supplied to the melting furnace. The amount of oxygen in the gas supplied to the melting furnace should be 80 to 120% of the theoretical combustion oxygen amount.

M 4: The fluidized medium of the fluidized bed gasifier is sand, alumina, dolomite or limestone.

M5: Fluidized bed gasifiers recover metals contained in solid waste from the furnace bottom in an unoxidized and clean state.

M 6: The smelting furnace is a swirling type melting furnace.

The present invention also provides a fluidized bed portion for pyrolyzing and solidifying solid waste at 450 to 65 ° C. A gasification and combustion system provided with a fluidized bed gasification furnace provided with: and a melting and combustion furnace which is provided at a stage subsequent to the fluidized bed gasification furnace and melts and burns at 120 to 150 ° C to convert ash into molten slag. Be in the reserve. In the gasification and combustion equipment of the present invention, the fluidized bed gasifier includes a fluidized gas supply having a supply port for supplying at least one gas selected from oxygen, water vapor, and air to the fluidized bed portion. It has a mechanism. The fluidizing gas supply mechanism sets the oxygen amount in the gas supplied to the fluidized bed to 10 to 30% of the theoretical combustion oxygen amount, and sets the mass velocity of the fluidizing gas at the center of the furnace bottom to the minimum fluidization mass velocity. A relatively slow fluidized bed was formed, which was 2 to 6 times larger than that of the fluidized gas, and the mass velocity of the fluidizing gas was 1.5 to 3 times the mass velocity of the fluidizing gas in the slow fluidized bed around the furnace bottom. An active fluidized bed is formed, and the area ratio of the slow fluidized bed in the section of the fluidized bed is set to 40 to 60%, while the fluidized medium flows from the peripheral part to the central part at the upper part of the fluidized bed. It produces a swirling motion of the moving fluid medium. The gasification combustion equipment of the present invention can have the following configuration.

S 1: One or more gases selected from oxygen, water vapor, and air are supplied to a free board of a fluidized bed gasifier, and carbides and tar generated in the fluidized bed section are collected in a free board section. Pyrolysis gasification at 0-850 ° C. The amount of oxygen in the gas supplied to the freeboard should be 0 to 20% of the theoretical combustion oxygen amount of solid waste c

S 2: Provide an inwardly inclined wall along the inner wall near the fluidized bed surface of the fluidized bed gasifier. The inclined wall turns the upward flow in the peripheral part of the fluid medium to the center part and promotes the swirling motion of the fluid medium, and the downward projected area of the inclined wall is 25 to 40% of the cross section of the fluidized bed. Yes, the inclination angle of the inclined wall with respect to the horizontal plane is 30 to 60 ° _c

S3: Fluidized bed gasification furnace fluid is sand, alumina, dolomite, or limestone.

S 4: The melting and burning furnace is a swirling type melting and burning furnace.

In the present invention, the solid waste is supplied to a fluidized-bed gasification furnace and pyrolyzed and gasified at 450 to 65 ° C. in a fluidized bed formed by a fluidized medium. The solid carbide generated at this time is finely pulverized by the agitating motion of the fluidized medium, and supplied to the subsequent melting and combustion furnace together with the generated gas. Solid carbides have a low burning rate, so less is desirable. Carbides are often generated at low gasification temperatures. If the gasification temperature is lower than 450 ° C, the rate of the gasification reaction becomes extremely slow and undecomposed Is deposited in the fluidized bed. Accordingly, in the present invention, the lower limit of the gasification temperature is set to 450 ° C. (preferably, 500 ° C.).

The higher the gasification temperature, the faster the gasification reaction and the less the formation of carbides. However, when the solid waste is supplied to the gasifier with a slight crushing treatment, if the gasification reaction is too fast, the fluctuation in the supply of waste will fluctuate between the gas generation amount and the furnace pressure. And adversely affect the operation of the subsequent melting furnace. Fluctuations in the amount of gas generated cause the concentration of CO in the exhaust gas of the melting furnace to rise. In addition, many solid wastes contain metals, and it is an important point of the present invention to collect these metals in an unoxidized state and to recycle them as ingots by type. In particular, in order to recover aluminum, its melting point is 660 ° C, so the gasification temperature must be lower. For these reasons, the present invention sets the upper limit of the gasification temperature at 65 ° C. (preferably, 600 ° C.).

In the present invention, the amount of heat required for pyrolysis gasification of waste is quickly supplied by an internal heat type, that is, partial combustion of waste. Internally heated gasifiers are clearly superior to externally heated gasifiers in terms of compactness and thermal efficiency.

When the gasification temperature is between 450 and 65 ° C, tar and carbide formation is inevitable. Tar and carbides have a slow burning rate, and can cause an increase in the volume of the subsequent melting furnace. In order to make a melt-burning furnace compact, the products of the gasifier must be low in tar and carbides, and must be mainly composed of gas components. For these reasons, in the present invention, preferably, the volume of the freeboard is used effectively, and oxygen-containing gas having substantially the same quality as the fluidizing gas is supplied to the freeboard of the gasification furnace. The second stage pyrolysis gasification is performed at ~ 850 ° C to convert tar and carbide into low molecular weight gas. The upper limit temperature of the second stage pyrolysis gasification in the freeboard is set at 850 ° C (preferably, 750 ° C) so that ash is not welded to the flue connecting the gasifier and the melting and burning furnace. C), and the lower limit temperature is set at 65 ° C. to promote the oxidative combustion of carbides.

The temperature of the melting and burning may be set to be 50 to 100 ° C higher than the melting temperature of the ash, but since the melting temperature of the ash varies depending on the type of waste, it is usually 1 500 ° C. In the fluidized bed furnace system of the present invention, 170 Since high temperatures of 0 to 180 ° C are not required, auxiliary materials such as coke are unnecessary.

The gas supplied to the pyrolysis gasification furnace and the melting combustion furnace is used by appropriately selecting from air, oxygen and steam according to the quality of the solid waste to be burned and the target gas properties (oxygen-rich activity). Including air). The amount of oxygen in the supplied gas is 10 to 30% for the gas supplied to the pyrolysis gasification fluidized bed when expressed as a ratio to the theoretical amount of oxygen in the waste, that is, as an oxygen ratio. In the case of gas supplied to the free board, the content is preferably 0 to 20%, and in the case of gas supplied to the melting and burning furnace, it is preferably 80 to 120%. The combined oxygen ratio is preferably about 130%.

The present invention is to completely burn solid waste without secondary pollution by using an internal swirling type fluidized bed furnace and a melting and burning furnace. An internal swirling fluidized bed reactor with a rectangular horizontal cross section was developed for the incineration of solid waste (Japanese Patent Application Laid-Open No. 57-124608, Japanese Patent Publication No. 62-5242). It is already in practical use. The fluidized bed gasifier used in the present invention is an application of this, and forms a relatively slow fluidized bed in which the fluidized medium flows down while flowing in the fluidized bed at the center of the furnace bottom. A relatively active fluidized bed is formed around the bottom of the furnace, where the fluidized medium rises while fluidizing in the fluidized bed, and the fluidized medium moves from the central part to the peripheral part at the lower part of the fluidized bed and moves to the upper part In addition, the following features are provided by generating the swirling motion of the fluid medium so that the fluid medium moves while flowing from the peripheral part to the central part.

(1) The generated carbide does not accumulate on the fluidized bed and is well and uniformly dispersed in the fluidized bed, and oxidation of the carbide is efficiently performed in the active fluidized bed. The amount of heat generated by the oxidation of carbides is quickly transferred to the fluidized medium, and is effectively used as a heat source for pyrolysis gasification in the center.

(2) On the surface of the fluidized bed, the fluid medium whose upward motion has been deflected by the inclined wall collides violently at the center, thereby promoting fine pulverization of carbides. When hard silica sand is used as the fluid medium, the fine grinding of carbides is further promoted.

(3) The solid waste can be supplied to the gasifier in a state close to no pulverization due to the swallowing action accompanying the downward movement of the fluidized medium in the slow fluidized bed. For this reason, crushing equipment can be light or omitted, and crushing power can be saved. (4) Due to the swirling motion of the fluidized medium, coarse incombustibles in solid waste can be easily discharged.

(5) The generated heat is diffused by the swirling flow of the fluidizing medium throughout the fluidized bed, and the trouble caused by the formation of the sintered product clinker can be avoided.

(6) By making the horizontal cross section of the gasification furnace circular, the manufacturing cost of the gasification furnace can be reduced compared to the case of a rectangular shape.

(7) By making the horizontal cross section of the gasification furnace circular, the scale-up does not shift in one direction as in a rectangular shape, and it is possible to cope with the future theme of pressurization.

In the case of a normal publishing type fluidized bed, the fluidized medium is fluidized uniformly in the fluidized bed, but the dispersion in the lateral direction is unexpectedly poor. Therefore, in the above points (1) to (4), the internal swirl type fluidized bed is considered to be superior to the publishing fluidized bed. In the case of a bubbled fluidized bed, if the input position of the waste is above the fluidized bed, there is a problem when undecomposed products accumulate on the fluidized bed due to poor swallowing of the waste into the fluidized bed. Supplying waste directly into the fluidized bed eliminates this problem, but causes problems such as sticking, abrasion, and corrosion of the input feeder and the necessity of gas sealing. In addition, a pyrolysis gasification zone is formed in the vicinity of the waste input area, and a carbide oxidation zone is formed in other areas.Since the dispersion of the carbide in the fluidized bed is poor, unreacted oxygen is likely to be generated, There is a disadvantage that the flammable gas in the high-strength port generated in the cracking gasification zone is wastedly burned by the unreacted oxygen.

The specific gravity of the carbide generated by pyrolysis gasification is about 1, which is less than half the specific gravity of the sand in the fluidized medium.In the publishing fluidized bed, a fluidized bed of the carbide is formed on the fluidized bed by segregation. You. Waste introduced from above the fluidized bed enters the fluidized bed of this carbide, but the heat conduction of the waste is slower because the heat conduction of the carbide is not as good as the sand of the fluidized medium. As a result, undecomposed substances are deposited in the fluidized bed of carbide, and the fluidized bed loses its original function. This is also a dangerous phenomenon, as it can sometimes lead to explosive gasification reactions. On the other hand, in the internal swirling type fluidized bed, since the carbides are uniformly dispersed in the bed due to the swirling motion of the fluidized medium, the input waste is required for thermal decomposition from the fluidized medium having good thermal conductivity. Calorie directly The waste will be pyrolized and gasified quickly.

In the internal swirling type fluidized bed furnace in which the gas dispersion plate of the present invention is inclined outward from the center of the furnace to the periphery, the fluid medium moves on the dispersion plate, so that even large-sized incombustibles accumulate on the dispersion plate. It is discharged smoothly without performing. In addition, in an internal swirling type fluidized bed furnace with inclined walls all around the furnace, the mass of the fluidized medium turned by the inclined walls collide violently at the center, so that carbide can be finely pulverized quickly. . In a normal bubbling fluidized bed, there is almost no such effect.

Prior to the present invention, the present inventors have invented an internal swirling type fluidized bed gasification furnace having a rectangular horizontal cross section (Japanese Patent Laid-Open No. 2-147692). For the reasons (1), (2) and (5) to (7) above, it was determined that the circular cross section was superior. In particular, the efficient oxidation of carbides described in (1) is the most important function as a gasifier. In the two-stage gasification, two fluidized-bed furnaces are provided, and pyrolysis gasification of waste and oxidation of carbides are performed in separate furnaces. It has a function equivalent to two-stage gasification, in which pyrolysis gasification of solid waste is mainly performed in the slow fluidized bed in the part, and the generated carbon is oxidized in the active fluidized bed in the surrounding part. Efficient gasification can be performed.

(Brief description of drawings)

FIG. 1 is a schematic vertical sectional view of one embodiment of a fluidized-bed gasification furnace used for carrying out the present invention.

FIG. 2 is a schematic vertical sectional view of another embodiment of the fluidized bed gasification furnace used for carrying out the present invention.

FIG. 3 is a schematic configuration diagram of an apparatus for performing the gasification combustion method of the present invention.

(Embodiment of the invention)

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic vertical sectional view of an embodiment of a fluidized-bed gasification furnace used for carrying out the present invention. In Fig. 1, fluidized bed gasifier 2 has gas dispersion plate 3, free board 6, inclined wall 11, incombustible discharge chute 12, air chamber for active fluidized bed 13, air for slow fluidized bed. Chamber 14 includes a slow fluidized bed 15 and an active fluidized bed 16. Fluidized bed gasifier ₂ is supplied with solid waste a, fluidized gas b for the activated fluidized bed, and fluidized gas b2 for the slow fluidized bed. Emission of synthetic gas e. The fluidized-bed gasifier 2 shown in FIG. 1 is of an internal swirl type, and the air distribution plate 3 has an inverted conical shape in which the center is highest and inclined outward. The fluidized bed on the air distribution plate 3 includes a slow fluidized bed 15 and an active fluidized bed 16.

The area occupied by the slow fluidized bed 15 is 40 to 60% in the horizontal section on the dispersion plate 3. The relationship between the diameter 1 ^ of the entire fluidized bed and the diameter r ₂ of the slow fluidized bed 15 is

r ₂ = (0.64 to 0.77) r, Region occupied by slow fluidized bed 15 and 50% in the horizontal section on the distribution plate 3, which is r ₂ 0. 7.

With minimum fluidization mass velocity G _mf of fluidizing gas begins to fluidize the fluidized medium, the mass velocity of the fluidizing gas in the slow fluidized bed 15, 2 to 6 g _mf (preferably, 3 to 5 G _mf) is . For (preferably, 1~2. 5 G _mf) of 0. 5~3G _mf conventional incineration With it easily can clinker, is easy cause can of _c clinker has been found by tests, flow It is considered that the fluidization was poor while the entire bed became carbide rich.

Table 1 shows the effect of the mass velocity G of the fluidized gas in the slow fluidized bed on clinker formation in a series of tests using a small test device (waste of 5 to 10 tons / day). , Waste plastic, scrap car shredder dust, municipal solid waste, etc. The results in Table 1, to-G _mf ratio R = GZG _mf of mass velocity G is a 2 to 6 suitable equivalents.

In order to obtain a smooth swirling motion of the fluidized medium, the mass velocity of the fluidized gas in the active fluidized bed should be 1.5 to 3 times the mass velocity of the fluidized gas in the slow fluidized bed. I understood. Results of a series of tests, the mass velocity of the fluidizing gas is slow fluidized bed 4G _mf, actively fluidized bed 8 G _mf was optimal combination. In this case, the fluidized gas mass velocity in the active fluidized bed is twice that of the slow fluidized bed.

It is desirable that the inclined wall, which inverts the fluid medium rising in the active fluidized bed to the center to promote the swirling motion of the fluidized medium, has a projected area below 25 to 40% of the cross section of the fluidized bed. In Figure 1, the diameter of the entire fluidized bed the smallest Ro径r _3! The relationship with ^ is r ₃ = (0. Ί ~ 0 · 87) r! It is represented by Increasing the sloped wall further increases the effect of reversing the flowing medium. Rather, the gas velocity increases in a narrow area above the fluidized bed, which has a serious adverse effect on solid waste falling into the fluidized bed. It becomes. It is effective that the angle of inclination of the inclined wall with respect to the horizontal plane is 30 to 60 °.

The fluidizing medium of the gasification furnace of the present invention is selected from sand such as silica sand and olivine sand, or alumina, dolomite, limestone, etc., and the fluidized bed temperature is about 450 to 65 ° C. As long as the mass velocity of the fluidizing gas is within the above range, there is no problem of clinker formation. Therefore, the fluid medium is preferably silica sand which is hard and easily available. The reason why hard silica sand is good is that carbide can be finely pulverized while swirling and flowing. The particle size of the silica sand used as the fluid medium is between 0.4 and 0.8 mm. Valuable metals such as iron, copper and aluminum contained in solid waste are discharged from the furnace bottom together with other incombustibles and fluid medium in a non-oxidized and clean state because the entire fluidized bed is in a reducing atmosphere. Then, after sieving, it is divided into coarse incombustibles containing metals and fine fluidized media. The separated fluid medium is returned to the gasification furnace and reused, but it is necessary to minimize the heat radiation in order to increase the energy efficiency of the furnace. Almost all of the metals contained in the waste with melting points higher than the fluidized bed temperature can be extracted from the bottom of the gasification furnace. In order to recover aluminum, the fluidized bed temperature must be lower than 660 ° C, the melting point of alumina.

It is recommended to use a swirling type melting furnace suitable for high-load combustion as a combustion furnace in which the generated gas is burned at a high temperature in the latter stage of the gasification furnace to melt ash into slag. This is because the furnace becomes compact due to high load combustion, and water cooling loss can be reduced. In addition, the slag mist collection efficiency can be increased by the action of the swirling flow, and the residence time of the carbide can be increased, so that the unburned loss of carbon can be reduced to the utmost. Some conventional incinerators do not have ash melting facilities or do not have ash melting facilities nearby, making it difficult to treat ash and fly ash discharged from incinerators and waste heat boilers. There is a place. By receiving such ash into this facility and treating it together with other solid waste, it will be possible to collect and use it as high-quality slag that does not contain unburned components.

In the internal swirling type fluidized bed gasification furnace used in the present invention, the amount of oxygen in the fluidized gas is small and the amount of combustibles is large in the slow fluidized bed at the center of the furnace. The process is similar to dry distillation, producing high-calorie flammable gas. The carbide generated at this time is uniformly dispersed in the active fluidized bed around the hearth by the swirling motion of the fluidized medium. Therefore, the oxygen in the fluidized gas supplied to the active fluidized bed is efficiently consumed for the oxidative decomposition of carbides. If the active fluidized bed contains a lean portion of carbides, oxygen is not sufficiently consumed and passes through the fluidized bed in an unreacted state, and the already generated high calorie fuel gas is consumed by combustion. However, in the fluidized bed furnace used in the present invention, since the carbide concentration in the active fluidized bed is kept almost constant by the swirling motion of the fluidized medium, such a situation cannot occur. High calorie fuel gas can be efficiently recovered.

As described above, the method (fluidized bed furnace method) of the present invention in which the internal swirling type fluidized bed furnace is used as a gasification furnace has the following advantages: the ease of operation, the need for coke and other auxiliary materials, and the amount of carbon dioxide generated. It is superior to the vertical furnace system in that it does not increase and many metals can be recovered in an unoxidized state.Moreover, the gasifier is extremely compact and has no moving parts. This is more advantageous than the rotary furnace method in that no equipment is required.

FIG. 2 is a schematic vertical sectional view of another embodiment of the fluidized bed gasification furnace used for carrying out the present invention. In the fluidized-bed gasification furnace shown in FIG. 2, the same members as those in FIG. 1 are denoted by the same reference numerals, and the repeated description will be omitted. The inclined wall 11 of the fluidized bed gasifier shown in Fig. 1 promotes the swirling motion of the fluidized medium, but does not prevent the waste from being swallowed into the fluidized bed and dispersing the char in the fluidized bed. If not, it can be omitted as in the embodiment of FIG. If the inclined wall is omitted, the swirling motion of the flowing medium becomes weaker, but the wear of the furnace material constituting the inclined wall can be reduced.

FIG. 3 is a schematic configuration diagram of equipment for performing the gasification combustion method of the present invention. The equipment shown in FIG. 3 includes a gasifier 2 and a rotary melting furnace 7. The gasification furnace 2 includes a quantitative supply device 1 for quantitatively supplying waste plastic waste a, a gas dispersion plate 3, a fluidized bed of silica sand 4, and a free board 6. The gasifier 2 is supplied with waste a and air b and air c for pyrolysis gasification, and discharges non-combustibles d and generated gas e. The revolving melting furnace 7 includes a primary combustion chamber 8, a secondary combustion chamber 9, a slag separation section 10, and temperature-raising parners 21 and 22. The revolving melting furnace 7 is composed of the gas e from the gasification furnace 2 and the air for melting and combustion. i is supplied, and the flue gas g and slag h are discharged. The gasifier 2 can be the internal swirling type fluidized bed gasifier of FIG. 1 or FIG. Waste a is usually mainly composed of plastic, which is separated from municipal waste as unburnable waste. The waste a is subjected to pretreatment such as crushing and sorting as required, and then supplied to the gasification furnace 2 by the screw type quantitative supply device 1. The air b is sent to the bottom of the gasifier 2 to form a fluidized bed 4 of silica sand on the gas dispersion plate 3. Waste plastic a is injected above the fluidized bed 4, falls into the fluidized bed 4 maintained at 450 to 65 ° C, comes into contact with air b, and is quickly pyrolyzed to gas. . The incombustibles d are discharged from the bottom of the gasifier 2 together with silica sand. The incombustibles d contain metals, but by setting the temperature of the fluidized bed 4 to 500 to 600 ° C, valuable metals such as iron, copper, and aluminum are recovered in an unoxidized and clean state. .

In the gasifier 2, gas, tar, and carbide are generated by pyrolysis gasification of the input waste a. The carbides are refined by the disturbance motion of the fluidized bed 4 and the attack of oxygen. Air c is blown into the free board 6 of the gasifier 2, and the second stage of pyrolysis gasification is performed at 65 to 85 ° C. In this way, gasification and decomposition of tar and carbide are promoted.

The generated gas e discharged from the upper part of the freeboard 6 is supplied to the primary combustion chamber 8 of the swirling melting furnace 7 while entraining fine carbides, and is mixed with the preheated air i in the swirling flow. It burns at a high temperature of 1200 to 1500 ° C. and moves to the secondary combustion chamber 9 while burning. The ash in the carbide is melted by high temperature to become slag mist, and is captured by the molten slag phase on the furnace wall of the primary combustion chamber 8 by the centrifugal force of the swirling flow, flows down the furnace wall, and enters the secondary combustion chamber 7 It is discharged from the bottom of the slag separation section 10. The flue gas g discharged from the rotary melting furnace 7 is discharged into the atmosphere through a heat recovery device such as a waste heat boiler, a economizer, and an air preheater and a dust removal device. The primary combustion chamber 8 and the secondary combustion chamber 9 of the revolving melting furnace 7 are provided with oil pans 21 and 22 for starting.

(The invention's effect)

The gasification and combustion equipment of the present invention is provided with a swirling fluidized bed furnace at the front stage and a melting combustion furnace at the rear stage. Solid waste is pyrolyzed and gasified at 450-650 ° C in the fluidized bed part of the fluidized-bed furnace, and the second stage is carried out at 65-850 ° C in the freeboard part of the fluidized bed furnace. of Pyrolysis gasification is performed, and thereafter, it is melt-combusted at 1200 to 150 ° C. in a melt-burning furnace, and the ash in solid waste is efficiently turned into molten slag. Slagified ash is discharged from the furnace bottom. The facility of the present invention is simple and compact, has excellent operability and safety, and can perform material recycling and energy recycling. Other effects or advantages of the present invention are as follows.

(1) Since solid waste combustion is gaseous combustion instead of solid combustion, low air ratio combustion with an air ratio of about 1.3 is realized, and the amount of exhaust gas is significantly reduced.

(2) Dioxins and furans hardly occur because high-temperature combustion is performed in a rotary melting furnace.

(3) The ash in the solid waste is melted by high temperature and becomes small slag with a small mass, so the life of the ash landfill can be extended, and the ash is converted as harmless slag from which heavy metals do not elute. Because it is collected, it can be used for roadbed materials.

(4) The energy of gas, tar, and carbide generated in the gasifier is effectively used as a heat source for ash melting.

(5) Since the solid waste gasification and combustion equipment of the present invention incorporates a dioxin treatment function and an ash melting function in the equipment, the entire equipment is compacted. The construction cost of gasification and combustion equipment is also lower than adding their respective functions to conventional incineration equipment.

(6) In the present invention, valuable metals such as iron, copper, and aluminum in solid waste can be recovered in a recyclable, unoxidized and clean state.

(7) The solid waste gasification and combustion equipment of the present invention can easily be of a high efficiency power generation type. 1 Influence of slow fluidized bed fluidized gas mass velocity G on clinker formation

(Raw material waste: waste plastic, scrap car shredder dust, municipal solid waste, etc.) Fluidized bed temperature Mass velocity G vs. G _m , Ratio test result

IN- — (j / U m f

R <n ΐϊΙ ^ Β after arΙi start Λ ^ ί.short rSL n 1 n J and the linker is vv, ^ χ,

Success. Poor flow occurs.

Small pieces of clinker are sometimes discharged Same as above, I \ ^ O.U, ヽ £ Ιϋ¾ί t¾ V Sat * <^ »C ΛΐΐϊΊ ^ ·

There is some concern about high ratio waste.

7-Pa, ί ÷ * · Λ お¹ fi} A ry Same as above 3.0 <R≤5.0. No problem for any waste.

Clinker's Ρα title has no force Flow Flow Same as above 5.0 <R≤6.0 The amount of scattering of the medium increases slightly. Fluid medium is scattered very much.

Becomes

Claims

The scope of the claims

1. The solid waste is pyrolyzed to gas at 450-650 ° C in the fluidized bed of the fluidized-bed gasification furnace, and then in the latter stage of the melting and combustion furnace at 1200-150 ° C. In the gasification and combustion method of solid waste, which melts and burns ash by melting and burning at ° C,

At least one gas selected from oxygen, water vapor, and air is supplied to the fluidized bed portion, and the amount of oxygen in the gas supplied to the fluidized bed portion is set to 10 to 30% of the theoretical combustion oxygen amount. A relatively slow fluidized bed in which the fluidized medium flows down while flowing in the fluidized bed is formed in the center, and a relatively active active fluidized bed in which the fluidized medium rises while flowing in the fluidized bed near the hearth bottom. The swirling motion of the fluid medium is such that the fluid medium flows and moves from the central part to the peripheral part at the lower part of the fluidized bed while moving at the upper part of the fluidized bed while flowing from the peripheral part to the central part. The area ratio of the slow fluidized bed in the section of the fluidized bed is set to 40 to 60%, the mass velocity of the fluidized gas in the slow fluidized bed is set to 2 to 6 times the minimum fluidized mass velocity, and active fluidization is performed. The mass velocity of fluidized gas in the bed Method characterized in that a 1.5 to 3 times the mass velocity of whether gas.

2. At least one gas selected from oxygen, water vapor, and air is supplied to the free board of the fluidized bed gasifier, and the carbides and tar generated in the fluidized bed section are supplied to the free board section. Wherein the amount of oxygen in the gas supplied to the freeboard portion is 0 to 20% of the theoretical combustion oxygen amount of solid waste at 0 to 850 ° C. Item 1 method.

3. An inclined wall is provided along the inner wall near the surface of the fluidized bed of the fluidized bed gasifier, and the upward flow of the fluidized medium at the periphery of the fluidized bed is turned to the center to promote the swirling motion of the fluidized medium. The method according to claim 1, wherein the downward projected area of the inclined wall is 25 to 40% of the cross section of the fluidized bed, and the inclined angle of the inclined wall with respect to the horizontal plane is 30 to 60 °.

4. Supply at least one gas selected from oxygen, water vapor, and air to the melting and burning furnace, and set the oxygen amount in the gas to be supplied to the melting and burning furnace to 80 to 120% of the theoretical combustion oxygen amount. The method of claim 1, wherein the method comprises:

5. The fluidized medium of the fluidized bed gasifier is sand, alumina, dolomite, or lime. The method of claim 1, wherein the method is a stone.

6. The method according to claim 1, wherein the fluidized-bed gasification furnace is for recovering metal contained in solid waste from the furnace bottom in an unoxidized and clean state.

7. The method according to claim 1, wherein the melting and burning furnace is a rotary melting and burning furnace.

8. Fluidized bed gasifier equipped with a fluidized bed for pyrolyzing and gasifying solid waste at 450 to 65 ° C, and provided at the latter stage of the fluidized bed gasifier, 120 to 150 In a gasification combustion facility that has a melting combustion furnace that melts and burns at 0 ° C to convert ash into molten slag, a fluidized bed gasification furnace is used to convert one or more gases selected from oxygen, steam, and air into a fluidized bed. A fluidizing gas supply mechanism having a supply port for supplying to the section,

The fluidized gas supply mechanism sets the amount of oxygen in the gas supplied to the fluidized bed to 10 to 30% of the theoretical combustion oxygen amount, and sets the mass velocity of the fluidized gas at the center of the furnace bottom to the minimum fluidized mass velocity. A relatively slow fluidized bed was formed, which was 2 to 6 times, and the mass velocity of the fluidizing gas around the furnace bottom was 1.5 to 3 times the mass velocity of the fluidizing gas in the slow fluidized bed. An active fluidized bed is formed, and the area ratio of the slow fluidized bed in the section of the fluidized bed is set to 40 to 60%, and the fluidized medium moves while flowing from the peripheral part to the central part at the upper part of the fluidized bed, A gasification combustion facility characterized in that a swirling motion of a fluid medium is generated at a lower part of a fluidized bed while moving from a central part to a peripheral part while moving.

9. At least one gas selected from oxygen, water vapor, and air is supplied to a free board of the fluidized bed gasifier, and the carbides and tar generated in the fluidized bed section are cooled in the free board section. The gasification according to claim 8, wherein the amount of oxygen in the gas pyrolyzed at 0 to 850 ° C and supplied to the free board is 0 to 20% of the theoretical combustion oxygen amount of the solid waste. Combustion equipment.

10. An inclined wall which is inclined inward is provided along an inner wall near the fluidized bed surface of the fluidized bed gasifier, and the inclined wall turns the upward flow in the peripheral portion of the fluidized medium to the central portion, The swirling motion of the fluidized medium is promoted, the downward projected area of the inclined wall is 25 to 40% of the cross section of the fluidized bed, and the inclined angle of the inclined wall with respect to the horizontal plane is 30 to 60 °. 9. The gasification and combustion facility according to claim 8, wherein