JPH10160141A - Method and apparatus for gasifying and combusting solid waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for gasifying and combusting solid waste in which operation is easy with excellent safety, compact construction, and good heat efficiency. SOLUTION: A solid waste is primary combusted at 450 to 650 deg.C in a fluidized bed layer 4 of a fluidized bed gasifying furnace 2, and is then secondary combusted at 650 to 850 deg.C in a free board part 6, and is further tertiary combusted at 1200 to 1500 deg.C in a later stage combustion furnace whereby an ash fraction is melted into slag. Herein, the fluidized bed and the free board part of the fluidized bed gasifying furnace is selected from one or more of oxygen, water vapor, and air, and the amount of oxygen in the gas supplied to the fluidized bed is 10 to 30% of the theoretical combustion amount of oxygen, the amount of oxygen in the gas supplied to the free board part is 0 to 20% of the theoretical combustion amount of oxygen. For the fluidized bed layer 4 there is used an internal turning fluidized bed gasifying furnace where a fluid catalyst is lowered 15 along a central part while being fluidized and the fluid catalyst is raised 16 along a peripheral part while being fluidized, and for the combustion furnace there is used a turning melting furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to solid waste, especially municipal solid waste, solidified fuel, slurried fuel, waste plastic, waste FRP, biomass waste, automobile waste,
The present invention relates to a method and an apparatus for gasifying and burning solid waste such as low-grade coal and waste oil, and for converting ash contained in the waste into molten slag. Among the above, solidified fuel is called RDF, which is obtained by crushing and sorting municipal solid waste and then adding quicklime etc. and compression-molding. For slurried fuel, municipal solid waste is crushed into water slurry, and hydrothermal treatment is performed under high pressure. Includes those that have been oiled by decomposition. FRP is a fiber reinforced plastic, and biomass waste includes water and sewage waste (contaminants, sewage, sewage sludge), agricultural waste (rice husk, rice straw, surplus products), forest waste (Nokokoku) Burk, thinned wood, industrial waste (pulp chip dust), construction waste, etc. Low-grade coal includes peat with a low degree of coalification, and waste produced during coal cleaning.

[0002]

2. Description of the Related Art At present, various companies are competing for the development of a "gasification combustion system" that combines gasification and combustion as a new environmental conservation type waste treatment technology that replaces the conventional incineration method, and has already entered the practical range. Some have reached. The common features of such a "gasification combustion system" are as follows. Due to the low air ratio combustion, the amount of exhaust gas is greatly reduced. Dioxins and furans are hardly generated by high-temperature combustion. Ash in the waste is recovered as harmless slag from which heavy metals do not elute. As a result, the life of the landfill can be extended,
It can also be used for roadbed materials. The retained energy of gas, tar, and carbide generated by gasification can be effectively used as a high-temperature source for melting ash. Since the functions of dioxin treatment and ash melting are incorporated in the system, the entire apparatus is made compact, and the construction cost is lower than that of a conventional incineration facility.

[0003] To give a background to the emergence of such technology, if the individual problems such as dioxin and ash melting were individually addressed, it would be inevitable that the construction cost and operating cost of the treatment facility would be relatively high. Immediate resolution was required. It was necessary to keep up with the anticipated tightening of dioxin regulations in the near future. The need for ash melting has rapidly increased in order to extend the life of landfills, which are becoming increasingly tight, and to make ash harmless and recycle. It has become desirable to create a system that maximizes the energy held by waste.

At present, the development of the "gasification and combustion system" has been preceded by a method using a vertical shaft furnace as a gasification furnace (hereinafter referred to as "S method") and a method using a rotary kiln furnace (hereinafter referred to as "R"). Method). In the former S method,
Drying and preheating zone (200-300 ° C) in gasification furnace,
A pyrolysis zone (300 to 1000 ° C) and a combustion / melting zone (1500 ° C or higher) are formed in layers from the top, and the waste and coke introduced from the upper part of the furnace are separated from the gas and heat generated in the lower zone. Lower inside the furnace while replacing.
The generated gas that has risen inside the furnace is about 900 in the subsequent combustion furnace.
Burned at ℃. The carbide generated in the pyrolysis zone descends with the charged coke to the melting and combustion zone,
It burns at high temperature with oxygen-enriched air supplied from the tuyere, and melts the entire amount of ash and inorganic substances. In the latter R method, waste is crushed and then supplied to a drum type rotary furnace externally heated by high-temperature air, and is slowly pyrolyzed and gasified at about 450 ° C. over time. The carbide generated at this time is discharged from the furnace and cooled to a temperature that does not ignite. Next, the finely pulverized carbide is supplied to a later-stage revolving-type melting furnace, where it is burned at a high temperature of 1300 ° C. together with a generated gas from a rotary furnace to convert ash into molten slag.

The problems of these two systems will be described. In the S-type shaft furnace, since a melting zone reaching 1700 to 1800 ° C. is present at the bottom of the gasification furnace, the use of auxiliary materials such as coke and oxygen-enriched air is inevitable, thereby increasing operating costs. In addition, there is a problem that the use of coke or the like increases the amount of carbon dioxide emitted. further,
Since almost all of the metal in the waste is melted, it cannot be recycled as bullion for each type of metal. The gasification furnace of this system belongs to the type of fixed-bed furnace, but it is difficult to operate stably because wastes of various shapes are stacked in layers and a combustion / melting zone is provided at the bottom. This is because in a fixed-bed furnace, it is very important to flow gas uniformly in the bed, that is, to ensure gas permeability.However, this is difficult due to the variety of waste shapes, and gas blow-through and drift are likely to occur. is there. The addition of coke has the purpose of ensuring such air permeability, but is not sufficient, and it is difficult to suppress fluctuations in gas flow rate and furnace pressure. Further, since not all of the generated gas passes through a high-temperature portion exceeding 1000 ° C., it is impossible to completely suppress the production of dioxins and furans.

On the other hand, since the R type gasification furnace is an external heating type rotary furnace using high-temperature air, heat transfer is not good, so that the furnace is inevitably increased in size. In addition, there is a problem that the heat transfer is further deteriorated because tar and undecomposed substances generated by the thermal decomposition cover the heat transfer surface. Obtaining high-temperature air as high as 600 ° C. by heat exchange with exhaust gas is impossible on the material of the heat exchanger. On the other hand, the generated carbide is pulverized after being discharged from the rotary furnace and then supplied to the combustion furnace, where it is combined with a gas directly supplied from the rotary furnace to perform high-temperature combustion. For this reason, handling equipment for carbides such as discharge, cooling, pulverization, storage, and supply is required. It is not desirable from the viewpoint of energy utilization that the heat possessed by the carbide is lost due to cooling or heat radiation during such handling. If the carbide is discharged to the outside without cooling, it is dangerous because it ignites when it comes into contact with air. The actual gasification temperature of both the S method and the R method is 450
Since the temperature is lower than ℃, there is a disadvantage that tar having a low burning rate increases.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and provides a method and apparatus for gasifying and burning solid waste, which is easy to operate, has excellent safety, is compact and has high thermal efficiency. The task is to provide

[0008]

In order to solve the above-mentioned problems, according to the present invention, solid waste is primarily combusted at 450 to 650 ° C. in a fluidized bed portion of a fluidized bed gasifier, and then solidified in a freeboard portion. The method for gasification and combustion of solid waste, wherein secondary combustion is performed at 650 to 850 ° C., and tertiary combustion is performed at 1200 to 1500 ° C. in a subsequent combustion furnace to melt ash into slag is provided. The gas supplied to the fluidized bed portion and the free board portion is selected from one or more of oxygen, water vapor and air, and the amount of oxygen in the gas supplied to the fluidized bed portion is 10 to 30% of the theoretical combustion oxygen amount. , The amount of oxygen in the gas supplied to the freeboard section is set at 0 to the theoretical combustion oxygen amount.
20%, the horizontal cross section of the fluidized bed gasifier is circular, a relatively slow fluidized bed is formed at the center of the furnace bottom, a relatively active fluidized bed is formed at the periphery of the furnace bottom, and near the surface of the fluidized bed. An inwardly sloping wall is provided along the inner wall of the furnace, and the flow of the fluid medium is turned from the peripheral part to the central part, so that the fluid medium descends while fluidizing in the slow fluidized bed at the central part of the furnace wall. The fluidized medium rises while flowing in the active fluidized bed at the periphery, while the fluidized medium moves from the central part to the peripheral part at the lower part of the fluidized bed and the fluidized medium moves from the peripheral part to the central part at the upper part of the fluidized bed. And the area ratio of the slow fluidized bed in the section of the fluidized bed is 40 to 40%.
60%, the mass velocity of the fluidizing gas in the slow fluidized bed is 2 to 6 times the minimum fluidizing mass velocity, and the mass velocity of the fluidizing gas in the active fluidized bed is 1.5 times the mass velocity of the fluidizing gas in the slow fluidized bed. The projected area below 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 °. Further, a gas selected from one or more of oxygen, water vapor, and air is supplied to the combustion furnace, and the amount of oxygen in the gas is set to 80 to 120% of the theoretical combustion oxygen amount.

In the fluidized-bed gasification furnace at the preceding stage for gasifying and burning the solid waste, sand, alumina, dolomite, and limestone are preferably used as a fluidized medium. From the bottom of the gasification furnace, metals contained in the solid waste can be recovered in an unoxidized and clean state. At this time, it is preferable to use a rotary melting furnace as the combustion furnace after the gasification furnace. Further, in the present invention, a fluidized bed gasifier consisting of a fluidized bed part for primary combustion at 450 to 650 ° C and a freeboard part for secondary combustion at 650 to 850 ° C, and a subsequent stage of 1200 to 1500 ° C In a solid waste gasification combustion device having a combustion furnace for tertiary combustion and melting ash into molten slag, the fluidized bed portion and the free board portion of the fluidized bed gasification furnace include oxygen, steam, and air. A supply port for supplying a gas selected from one or more is provided, and the amount of oxygen in the gas supplied to the fluidized bed is set to 10 to 30 times the theoretical combustion oxygen amount.
%, And a control mechanism for controlling the amount of oxygen in the gas supplied to the freeboard portion to 0 to 20% of the theoretical combustion oxygen amount. The fluidized bed gasifier has a circular horizontal cross section, The fluidized gas has a mass velocity of 2-6 times the minimum fluidized mass velocity to form a relatively slow fluidized bed, and the mass velocity of the fluidized gas in the fluidized bed is reduced around the furnace bottom. A relatively active fluidized bed 1.5 to 3 times the mass velocity is formed, and an inwardly inclined wall is provided along the inner wall near the surface of the fluidized bed. Of the fluidized medium that moves while being fluidized from the central part to the central part. The area ratio of the slow fluidized bed in the section of the fluidized bed is 40 to 60%, and the projected area below the inclined wall is 25% of the section of the fluidized bed. ~ 40%, the inclination angle of the inclined wall with respect to the horizontal plane It was 0 to 60 ° is obtained by the gasification and combustion apparatus of solid waste, characterized in.

[0010]

Next, the present invention will be described in detail.
In the present invention, a study (F method) using an internal swirling type fluidized bed gasifier and a combustion furnace (preferably a swirling melting furnace) has been made by studying the above-mentioned R method. The solid waste is fed to a gasifier and is placed in a fluidized bed formed by a fluidized medium at 450
Pyrolysis gasification at ~ 650 ° C. The carbide generated during gasification is finely pulverized by the agitating motion of the fluidized bed, and is supplied to the subsequent combustion furnace together with the gas. However, it is desirable that the amount of carbide having a low burning rate be small even though it is miniaturized. Therefore, it is not preferable that the gasification temperature is too low because the amount of carbides increases. In addition, the gasification temperature is 45
When the temperature is lower than 0 ° C., the pyrolysis gasification reaction becomes extremely slow, which causes a troublesome problem that undecomposed products tend to be deposited. Therefore, the lower limit of the gasification temperature is 450 ° C.
(Preferably 500 ° C.).

On the other hand, the higher the gasification temperature, the smaller the generation of carbides and the faster the pyrolysis gasification reaction. However, in the present invention, since the waste is supplied to the gasification furnace in a state as near as possible without crushing, if the reaction is too fast, the fluctuation in the amount accompanying the supply of the waste will fluctuate in the gas generation amount and the furnace pressure. And adversely affect the operation of the combustion furnace. Fluctuations in the amount of gas generated cause an increase in the CO concentration in the exhaust gas from the combustion furnace. Although many wastes contain metals, it is an important point of the present invention to recover these metals in an unoxidized state and to recycle them as bullion for each type.
Particularly when the object is aluminum, the melting point is 660 ° C., so that the gasification temperature needs to be lower than this. Thus, the upper limit of the gasification temperature is 650 ° C. (preferably 600 ° C.).
° C). The amount of heat required for pyrolysis gasification of waste is quickly and efficiently supplied by partially burning waste. Such a method of supplying heat is generally called an internal heat type, and an internal heat type furnace is clearly superior to an external heat type in terms of compactness and thermal efficiency.

However, in such a low gasification temperature range, generation of tar and carbide having a low combustion rate is inevitable. This is a factor that increases the volume of the subsequent combustion furnace. In order to make the combustion furnace compact, it is necessary to increase the gasification temperature to obtain a gas composition mainly composed of gas components. For this purpose, and in order to prevent the fluidized bed from expanding due to the accumulation of carbides and to effectively utilize the volume of the freeboard portion of the gasifier, the present invention uses a fluidized gas in the freeboard portion of the gasifier. Supplying oxygen-containing gas of almost the same quality, 650-850
The secondary combustion, that is, the second-stage gasification was performed at ℃. Most of the tars and carbides are converted into low molecular weight gas by the secondary combustion. Thus, the load of the combustion furnace can be reduced and the combustion furnace can be made compact. In addition, the upper limit of the temperature in the secondary combustion was set to 850 ° C. (preferably 750 ° C.) in order not to deposit ash in the flue connecting the gasification furnace and the combustion furnace. The lower limit of the temperature at the time of the secondary combustion was 650 ° C. in order to prevent the accumulation of carbide in the fluidized bed. However, secondary combustion in the freeboard section is not absolutely necessary. It is determined on a case-by-case basis depending on the nature of the waste.

The tertiary combustion in the combustion furnace may be set at a temperature 50 to 100 ° C. higher than the temperature at which the ash melts, but the ash melt temperature varies depending on the type of waste. To 1500 ° C. In the present F method, since a high temperature of 1700 to 1800 ° C. is not required as in the S method, no auxiliary material such as coke is required at all. Depending on the quality of the target solid waste and the target gas properties,
The gas supplied to the primary to tertiary combustion is appropriately selected and used from air, oxygen, and steam. Of course, oxygen-rich air is also included in this. When the oxygen amount in the gas is represented by a ratio to the theoretical combustion oxygen amount of the waste, that is, the oxygen ratio, primary combustion is 10 to 30%, secondary combustion is 0 to 20%,
The tertiary combustion is preferably set to 80 to 120%. The oxygen ratio including the primary to tertiary combustion is preferably about 130%.

The present invention is a system for completely burning solid waste without secondary pollution by combining an internal swirling type fluidized bed gasifier and a combustion furnace (preferably a swirling melting furnace). is there. An internal swirling fluidized bed furnace having a rectangular horizontal section has been developed for incineration of solid waste and has already been put into practical use (Japanese Patent Application Laid-Open No. 57-124608, Japanese Patent Publication No.
2-5242). The fluidized bed gasifier developed for the "gasification combustion system" has a circular horizontal section, a slow fluidized bed at the center of the fluidized bed, and an active fluidized bed at the periphery along the wall, and a fluidized medium. The swirl flow descends the slow fluidized bed in the central part and rises the active fluidized bed in the peripheral part, thereby giving the following features.

[0015] Since the generated carbide does not accumulate on the fluidized bed and is well and uniformly dispersed in the fluidized bed, the oxidation of the carbide particularly in the active fluidized bed is efficiently performed. The heat generated by the oxidation of the carbide is quickly transmitted to the fluidized medium, and is effectively used as a heat source for pyrolysis gasification in the central portion. On the surface of the fluidized bed, the fluid medium whose upward motion has been turned by the inclined wall collides violently in the center,
Fine grinding of carbides is promoted. Due to the use of hard silica sand as the flowing medium, the comminution of carbides is further promoted. The solid waste can be supplied to the gasification furnace in a nearly non-crushing state by the swallowing action accompanying the downward movement of the fluidized medium in the slow fluidized bed. For this reason, crushing equipment can be omitted or eliminated, and the power for crushing can be greatly reduced.

[0016] Due to the swirling flow of the flowing medium, even coarse incombustibles resulting from non-crushing charging can be easily discharged. Due to the swirling flow of the fluid medium throughout the fluidized bed,
Since the generated heat is diffused, it is possible to avoid troubles caused by a sintered product or clinker. The manufacturing cost is lower than when the horizontal section is rectangular. The scale-up does not shift in only one direction as in the case of a rectangle, and it can cope with future pressurization.

In the case of a commonly used bubbling type fluidized bed, although the fluidized medium is fluidized uniformly in the fluidized bed,
Lateral dispersion is not very good. Therefore, it is considered that the internal swirling type fluidized bed of the present invention is superior to the bubbling fluidized bed in the above points (1) to (4). If the position where the waste is charged in the bubbling fluidized bed is above the fluidized bed, there is a problem that undecomposed substances are deposited on the bed due to poor swallowing of the waste into the fluidized bed. Feeding the waste directly into the fluidized bed eliminates this problem, but creates problems and challenges such as sticking, wear, corrosion, and gas sealing on the input feeder. In addition, a pyrolysis gasification zone is formed in the vicinity of the waste input portion, and a carbide oxidation zone is formed in other portions. However, since the dispersion of the carbide in the layer is not good, unreacted oxygen is easily generated, and the pyrolysis gas is generated. The high calorie combustible gas generated by the gasification zone is unnecessarily burned by the unreacted oxygen, and therefore has a disadvantage that a high calorie combustible gas cannot be efficiently obtained. Naturally, the scattering amount of the carbide also increases.

The carbide generated by the pyrolysis gasification has a specific gravity of about 0.5, which is one hour smaller than that of sand used as a fluid medium.
/ 5th place. For this reason, in the bubbling fluidized bed, a fluidized bed of carbide may be formed on the fluidized bed of the fluidized medium due to segregation. Waste introduced from above the fluidized bed enters the fluidized bed of the carbide. The heat transfer to the waste is slower due to the poorer heat conduction of the carbides compared to the fluidized medium, which results in undecomposed products being deposited in the fluidized bed of carbides. In this case, the fluidized bed of the fluidized medium does not perform its original function. This is also a dangerous phenomenon, as it can sometimes lead to explosive reactions.

On the other hand, in the internal swirling type fluidized bed, the carbides swirl together with the fluidized medium, so that the waste introduced into the gasification furnace transfers the heat required for thermal decomposition from the fluidized medium having good heat conduction. You can receive it directly. Therefore, the waste is quickly gasified by pyrolysis. In the internal swirling type fluidized-bed gasification furnace of the present invention, the fluidized medium moves on the dispersion plate inclined outward from the center toward the periphery, so that even large-sized incombustibles can be easily deposited on the dispersion plate. Is discharged. In the internal swirling type fluidized bed, it is observed that the mass of the fluidized medium turned by the inclined wall provided on the entire inner circumference of the furnace violently collide with the central part, and therefore, the carbide is quickly pulverized. I can do it. Bubbling-type fluidized beds have little such effect.

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

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 shows a vertical sectional view of a fluidized-bed gasification furnace. In FIG. 1, 2 is a gasifier, 3 is a dispersion plate, 6 is a free board, 1
1 is an inclined wall, 12 is an incombustible discharge chute, 13 is an air chamber for an active fluidized bed, 14 is an air chamber for a slow fluidized bed, 15 is a slow fluidized bed, and 16 is an active fluidized bed. b ₁ fluidizing gas for actively fluidized layer, b ₂ is the fluidizing gas for slow fluidized bed. In the internal swirling type fluidized bed gasification furnace shown in the figure, the air distribution plate has an inverted conical shape, the highest at the center, and inclined outward. The fluidized bed on it is divided into a slow fluidized bed and an active fluidized bed. The area occupied by a slow fluidized bed is
In a horizontal section on the dispersing plate, it is preferable that the ratio is 40 to 60% of the whole. The diameter of the entire fluidized bed is r ₁ and the diameter of the slow fluidized bed is r ₂
Expressed in, and _{r 2 = (0.64~0.77) r 1} .
Usually, the above area ratio is often set to 50%.
In that case, r ₂ = 0.71r ₁ .

The mass velocity of the fluidizing gas in the slow fluidized bed is 2 to 6 G when the minimum fluidization mass velocity is represented by G _mf.
mf (preferably 3 to 5 G _mf ). Usually 0.5 to 3 G _mf (preferably 1 to 2.
Is a 5G _mf), to be susceptible can of clinker it revealed the results of the test in this. It is considered that clinker is likely to occur because gasification at a relatively low temperature of 450 to 650 ° C. makes the entire fluidized bed rich in carbide. Further, in order to obtain a smooth swirling flow of the fluidized medium, the mass velocity of the fluidizing gas in the active fluidized bed is 1.5 to the mass velocity of the fluidizing gas in the slow fluidized bed.
It turned out that it is better to increase it by three times. In a series of tests,
The optimum combination of the mass velocity of the fluidizing gas was 4 _{Gmf in the} slow fluidized bed and 8 _{Gmf in the} active fluidized bed. in this case,
The fluidized gas mass velocity in an active fluidized bed is twice that of a slow fluidized bed.

With respect to the inclined wall which promotes the swirling flow of the fluidized medium by inverting the fluidized medium rising in the active fluidized bed to the center, its downward projected area is 25 to 40 of the cross section of the fluidized bed.
% Is desirable. In FIG. 1, if the furnace diameter at the narrowest part is r ₃ , r ₃ = (0.77 to 0.87)
r ₁ . Even if the inclined wall is made larger, the effect of inverting the flowing medium does not change much. Rather, the adverse effect of preventing solid waste from falling into the fluidized bed is greater because the gas velocity in the narrow portion above the fluidized bed is increased. In addition,
The inclination angle θ of the inclined wall with respect to the horizontal plane is 30 to
An angle of 60 ° is effective. The fluidizing medium of the gasifier in the present invention is selected from sand such as silica sand and olivine sand, or alumina, dolomite, limestone, etc.
Since the fluidized bed temperature is as low as about 450 to 650 ° C., there is no problem of agglomeration if the mass velocity of the fluidizing gas is within a predetermined range. Therefore, it is preferable to use hard and easily available silica sand. Hardness is good because carbides can be pulverized while fluidizing. In the case of silica sand, the average particle size is 0.4 to 0.8.
mm.

Since valuable metals such as iron, copper, and aluminum contained in solid waste are in a reducing atmosphere throughout the fluidized bed, they are not oxidized and clean from the furnace bottom, and other non-combustible materials and fluids After being discharged together with the medium and then sieved, it is separated into a coarse incombustible material containing metal and a fine fluidized medium. The separated fluid medium is returned to the gasification furnace and reused. In order to increase the energy efficiency of the furnace, it is necessary to suppress heat radiation as much as possible.
Almost all of the metals contained in the waste having a melting point higher than the fluidized bed temperature can be taken out from the bottom of the gasification furnace. Among metals, particularly for recovery of aluminum, the fluidized bed temperature may be set lower than 660 ° C., which is the melting point of aluminum.

In the latter stage of the gasification furnace, a swirling melting furnace suitable for high load combustion is preferably used as a combustion furnace for burning ash by melting the produced gas at a high temperature. 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 centrifugal effect of the swirling flow, and the unburned loss of carbon can be reduced to the utmost in order to keep carbides on the furnace wall for a long time. Some conventional incinerators include
Because there is no ash melting facility or there is no ash melting facility nearby, there are places where it is difficult to treat under-furnace ash and fly ash discharged from incinerators and waste heat boilers. By accepting such ash in this facility and treating it together with other solid waste, a way to collect and use it as high-quality slag that does not contain unburned matter is opened.

In the internal swirling type fluidized bed gasifier according to 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 bottom. It is closer to a dry distillation condition, and as a result, a high calorie combustible gas is generated. The carbide generated at this time is uniformly dispersed in the active fluidized bed around the furnace bottom by the swirling motion of the fluidized medium. Therefore, oxygen in the fluidizing gas supplied to the active fluidized bed is efficiently consumed for oxidative decomposition of carbides. If a thin portion of carbides exists in the active fluidized bed, 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 method, the carbide concentration in the active fluidized bed is kept almost constant by the swirling motion of the fluidized medium, so that this cannot occur. Gas can be efficiently recovered.

As described above, the present invention (F method) in which the internal swirling type fluidized bed furnace is used for the gasification furnace is easy to operate, does not require auxiliary materials such as coke, and has a small carbon dioxide generation amount. It is superior to the S method in that it does not increase the amount of metal, and in that many metals can be recovered in an unoxidized state. In addition, the gasification furnace is extremely compact and there is no operating part. Is clearly advantageous over the R method in that it is unnecessary.

Next, the present invention will be described with reference to FIG. FIG. 2 shows a schematic configuration diagram of an example of an apparatus used for the gasification combustion method of the present invention. In the figure, 1 is a fixed amount supply device, 2 is a gasification furnace, 3 is a dispersion plate, 4 is a fluidized bed of silica sand, 6 is a free board, 7 is a revolving melting furnace, 8 is a primary combustion chamber, and 9 is a secondary combustion. The chamber 10 is a slag separation section. a is waste plastic, b is primary air, c is secondary air, d is noncombustible, e is generated gas, g is combustion exhaust gas, h is slag, and i is tertiary air. The gasification furnace 2 is the internal swirling type fluidized bed gasification furnace shown in FIG. 1, but is omitted in this figure. The waste plastics a used here are assumed to be those mainly composed of plastics separated and collected as unsuitable garbage in general municipal waste.

The waste plastic a is crushed if necessary.
After performing pretreatments such as sorting, it is supplied to the gasification furnace 2 by the screw type quantitative supply device 1. Primary air b is fed into the bottom of the gasification furnace 2 to form a fluidized bed 4 of silica sand on the dispersion plate 3. The waste plastic a is charged above the fluidized bed 4, falls into the fluidized bed 4 maintained at 450 to 650 ° C., comes into contact with the primary air b, and is quickly pyrolyzed into gas. The incombustibles d are discharged from the bottom of the gasification furnace 2. The non-combustible material d contains a metal, but practically, by setting the fluidized bed temperature to 500 to 600 ° C, iron,
Valuable metals such as copper and aluminum are recovered in an unoxidized and clean state. Gas, tar and carbides are generated by pyrolysis gasification. The carbide is refined by the disturbance motion of the fluidized bed 4. Secondary air is blown into the free board 6 of the gasification furnace 2, and the second stage gasification is performed at 650 to 850 ° C. Thus, gasification and decomposition of tar and carbides are promoted.

The generated gas e from the upper part of the free board 6 is
The high-temperature combustion of 1200 to 1500 ° C. is performed while entraining fine carbides and being supplied to the primary combustion chamber 8 of the swirling melting furnace 7 and mixing with the preheated tertiary air i in the swirling flow. The combustion is completed in the next secondary combustion chamber 9, and the combustion exhaust gas g is discharged from above the slag separation unit 10. The ash in the carbides becomes slag mist due to the high temperature, 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 9 to form slag. It is discharged from the bottom of the separation unit 10. Note that the combustion exhaust gas g that has exited the swirling melting furnace 7 is discharged to the atmosphere through a series of heat recovery devices such as a waste heat boiler, a economizer, and an air preheater and a dust removal device. In addition, in the primary combustion chamber 8 and the secondary combustion chamber 9 of the swirling type melting furnace 7, an oil burner 11 for starting and an auxiliary is installed.

[0031]

When the present invention is applied to gasification and combustion of solid waste, the following effects can be obtained. Since gas combustion replaces solid combustion, combustion at a low air ratio of about 1.3 is realized, and the amount of exhaust gas is significantly reduced. Due to high temperature combustion, dioxins are hardly generated. Ash in the waste is recovered as harmless slag from which heavy metals do not elute. As a result, the life of the landfill can be extended,
It can also be used for roadbed materials. The energy of gas, tar, and carbide generated in the gasifier can be effectively used as a high-temperature source for melting ash.

Since the functions of dioxin treatment and ash melting are incorporated in the system, the entire apparatus is made compact, and the construction cost is lower than when each function is provided to a conventional incinerator. Valuable metals such as iron, copper and aluminum can be recovered in a recyclable, unoxidized and clean state. It is easy to use a high-efficiency power generation type. In the present invention, a fluidized-bed furnace is disposed in a gasification furnace, and a combustion furnace is disposed in a subsequent stage. After primary combustion at 450 to 650 ° C in a fluidized bed portion, secondary combustion is performed at 650 to 850 ° C in a freeboat portion. After that, tertiary combustion is performed at 1200 to 1500 ° C. in a combustion furnace, and the ash is efficiently converted into molten slag and discharged from the bottom of the combustion furnace, thereby achieving simplicity and compactness.
It provides high value-added, environmentally-friendly waste treatment technology that improves material recycling, energy recycling, and ease of operation and safety.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a fluidized-bed gasification furnace used in the present invention.

FIG. 2 is a schematic configuration diagram showing an example of an apparatus used for the gasification combustion method of the present invention.

[Explanation of symbols]

1: quantitative feeder, 2: gasifier, 3: dispersion plate, 4: fluidized bed, 6: free board, 7: swirling melting furnace, 8: primary combustion chamber, 9: secondary combustion chamber, 10: slag Separation unit, 11:
Inclined wall, 12: incombustible discharge chute, 13: air chamber for active fluid layer, 14: air chamber for slow fluidized bed, a: waste plastic, b: primary air (b _1: fluidizing for actively fluidized bed Gas, b ₂ : fluidizing gas for slow fluidized bed), c: secondary air, d: non-combustible, e: product gas, g: combustion exhaust gas, h:
Slag, i: tertiary air

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23G 5/30 ZAB F23G 5/30 ZABR F23J 1/00 F23J 1/00 B F23L 7/00 F23L 7/00 AZ (72) Inventor Tetsuhisa Hirose 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Takahiro Ohshita 11-1 Asahi-cho Haneda, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Yasuo Makino 11-1 Asahi-cho, Haneda, Ota-ku, Tokyo Inside Ebara Corporation

Claims (6)

[Claims] 1. A primary combustion of solid waste at 450 to 650 ° C. in a fluidized bed portion of a fluidized bed gasifier, followed by a secondary combustion at 650 to 850 ° C. in a free board portion, and a subsequent combustion furnace In the gasification and combustion method for solid waste in which ash is melted and slag-formed by tertiary combustion at 1200 to 1500 ° C., gas supplied to the fluidized bed portion and the free board portion of the fluidized bed gasifier is oxygen, The amount of oxygen in the gas supplied to the fluidized bed is selected from one or more of water vapor and air, and the amount of oxygen in the gas supplied to the freeboard is 10 to 30% of the theoretical combustion oxygen. 0-2 of quantity
0%, the horizontal section of the fluidized bed gasifier is circular,
A relatively slow fluidized bed is formed at the center of the furnace bottom, a relatively active fluidized bed is formed around the furnace bottom, and an inwardly inclined wall is provided along an inner wall near the surface of the fluidized bed to allow the flow of the fluid medium to flow. By turning from the peripheral part to the central part, the fluid medium descends while fluidizing in the slow fluidized bed in the central part of the furnace bottom, while the fluid medium rises while fluidizing in the active fluidized bed in the peripheral part of the furnace bottom, In the lower part of the fluidized bed, the fluidized medium causes a swirling motion such that the fluidized medium moves from the central part to the peripheral part while being fluidized from the peripheral part to the central part in the upper part of the fluidized bed. 40-60 area ratio of slow fluidized bed
%, The mass velocity of the fluidized gas in the slow fluidized bed is 2 to 6 times the minimum fluidized mass velocity, and the mass velocity of the fluidized gas in the active fluidized bed is 1.5 times the mass velocity of the fluidized gas in the slow fluidized bed. A method for gasifying and burning solid waste, wherein the projected area below 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 °. 2. A gas selected from one or more of oxygen, water vapor, and air is supplied to the combustion furnace, and the amount of oxygen in the gas is 80 to 120% of the theoretical combustion oxygen amount. The method of claim 1, wherein: 3. The method according to claim 1, wherein the fluidized bed gasifier uses sand, alumina, dolomite, or limestone as a fluidized medium. 4. The method according to claim 1, wherein the fluidized-bed gasification furnace recovers the metal contained in the solid waste in an unoxidized and clean state from the furnace bottom. 5. The method according to claim 1, wherein the combustion furnace is a rotary melting furnace. 6. A fluidized bed gasification furnace comprising a fluidized bed section for primary combustion at 450 to 650 ° C. and a freeboard section for secondary combustion at 650 to 850 ° C.
A combustion furnace for performing tertiary combustion at 200 to 1500 ° C. to melt and convert ash to slag, wherein the fluidized bed portion and the freeboard portion of the fluidized bed gasification furnace contain oxygen, steam, A supply port for supplying a gas selected from one or more of air is provided, and the amount of oxygen in the gas supplied to the fluidized bed portion is 10 to 30% of the theoretical combustion oxygen amount. The fluidized-bed gasifier has a circular horizontal cross section, and the mass velocity of the fluidized gas is minimized at the center of the furnace bottom. And a relatively slow fluidized bed at 2 to 6 times the mass velocity of the fluidized gas is formed at the periphery of the furnace bottom to 1.5 to 3 times the mass velocity of the fluidized gas in the slow fluidized bed. To form a relatively active fluidized bed The inner wall near the surface of the bed is provided with an inclined wall that is inclined inward, causing a swirling motion of the fluid medium that moves while flowing from the peripheral part to the central part at the upper part of the fluidized bed. , The area ratio of the slow fluidized bed is 40 to 60%, 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 °. Gasification and combustion equipment for solid waste.