JP2004264017A - Municipal waste gasification furnace and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for gasifying combustible materials such as waste and coal, and generating a produced gas including a large amount of flammable components of which ash contents are meltable by self heat quantity for melting and burning. <P>SOLUTION: This gasification furnace for gasifying the waste is a fluid bed furnace 2 having a circular horizontal cross-section, and the fluid bed furnace comprises a central fluidized-gas supplying means for forming a moving bed where the fluidized medium is precipitated on a central part of the furnace, and a circumferential fluidized-gas supplying means for forming a fluid bed where the fluidized medium rises, at a circumferential part of the furnace. A bed material forms the circulated flow through the moving bed and the fluid bed, the waste is supplied to the fluid bed furnace 2 to be gasified, the fluid bed furnace 2 comprises a noncombustible material discharge port for discharging the noncombustible material included in the waste and the bed material, and comprises a valve for sealing the internal pressure of the fluid bed furnace 2 in discharging the noncombustible material included in the waste and the bed material to separate the discharged noncombustible material and the bed material, and the separated bed material is returned to the fluid bed furnace 2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a gasification furnace for gasifying municipal solid waste in a fluidized bed furnace, and a method and an apparatus for melting ash by burning generated combustible gas and fine particles in a fusion combustion furnace at a high temperature.

  2. Description of the Related Art In recent years, it has been desired to incinerate a large amount of municipal waste and waste plastics and other wastes to reduce the amount thereof, and to effectively utilize the heat of incineration. Since waste incineration ash usually contains harmful heavy metals, it is necessary to take measures such as solidifying heavy metal components in order to treat incineration ash by landfill. In order to cope with these problems, a method and apparatus for burning solids have been proposed in Japanese Patent Publication No. 62-35004. In the combustion method disclosed in this publication, a solid material is pyrolyzed in a fluidized bed pyrolysis furnace, and pyrolysis products, that is, combustible gas and particles are introduced into a cyclone combustion furnace. In the cyclone combustion furnace, flammable components are burned with high load by pressurized air, and ash collides with the wall surface due to the swirling flow, melts and flows down the wall surface, turns into molten slag, drops from the outlet to the water chamber, and is solidified .

  In the method disclosed in Japanese Patent Publication No. 62-35004, a high gasification efficiency is obtained because the entire fluidized bed is in an active fluidized state and a large amount of unreacted combustibles are scattered out of the furnace along with the generated gas. There were disadvantages such as not being able to. Conventionally, as a gasification raw material that can be used in a fluidized bed furnace, coal or the like has been powdered coal having a particle size of 0.5 to 3 mm, and waste has been crushed to several tens of mm. If it is larger than this, fluidization will be hindered, and if it is smaller than this, it will not be completely gasified and will fly out of the furnace as unreacted combustibles along with the generated gas. Therefore, in conventional fluidized bed furnaces, it is indispensable to crush and size using a pulverizer or the like in advance as a pretreatment before charging the gasification raw material into the furnace, and do not fall within a predetermined particle size range. Gasification feedstock was not available and yields had to be sacrificed to some extent.

  In order to solve the above-mentioned problems, a fluidized-bed gasification method and a fluidized-bed gasification furnace disclosed in Japanese Patent Application Laid-Open No. 2-147692 have been proposed. In the fluidized-bed gasification method disclosed in this publication, the horizontal cross section of the furnace is rectangular, and the mass velocity of the fluidizing gas ejected upward from the center of the furnace bottom into the furnace is increased from two side edges of the furnace bottom. The mass velocity of the fluidizing gas to be supplied is made smaller, the upward flow of the fluidizing gas is diverted to the central part of the furnace above the bottom edge of the furnace, and a moving bed is formed in the central part of the furnace where the fluidized medium sinks, Fluidized beds in which the fluidized medium is actively fluidized are formed on both side edges of the furnace, and combustibles are supplied to the moving bed. The fluidizing gas is a mixture of air and steam or a mixture of oxygen and steam, and the fluidizing medium is quartz sand.

  However, the method disclosed in Japanese Unexamined Patent Publication No. Hei 2-147692 has the following disadvantages. That is, (1) In the entire moving bed and the fluidized bed, a gasification endothermic reaction and a combustion reaction occur simultaneously, and volatile components that are easily gasified are gasified and burned at the same time, and fixed carbon (char) and tar components that are difficult to gasify are burned. And the like are scattered outside the furnace as unreacted substances with the produced gas, and high gasification efficiency cannot be obtained. (2) When the produced gas is burned and used in a combined steam and gas turbine power plant, it is necessary to use a pressurized fluidized bed furnace. Have difficulty. The preferred gasifier internal pressure is determined by the application of the product gas. When it is used as a general combustion gas, it may be about several thousand mmAq. However, when it is used as a fuel for a gas turbine, several kgf / cm2 or more is required. When it is used as, more than ten and several kgf / cm2 or more is appropriate.

  Regarding waste treatment such as municipal solid waste, reduction of the amount of combustible waste by combustion still plays an important role, and accompanying this, in recent years, measures against dioxins, detoxification of dust, and improvement of energy recovery efficiency For example, the need for environmentally friendly waste treatment technology is increasing. The amount of incineration of municipal solid waste in Japan is about 100,000 tons / day, and the total energy of municipal solid waste corresponds to about 4% of the power consumption of Japan. At present, the energy utilization rate of municipal solid waste is only about 10%. However, if the utilization rate can be increased, the consumption of fossil fuel will be reduced accordingly, which can contribute to the prevention of global warming.

However, current incineration systems include the following problems. That is, (1) there is a problem of corrosion due to HCl, and the power generation efficiency cannot be increased. (2) Pollution prevention equipment for HCl, NOx, SOx, mercury, dioxin, and the like is complicated, and cost and space are increasing. (3) The installation of incineration ash melting equipment is increasing due to the strengthening of laws and regulations, land shortage at the final disposal site, etc.Therefore, construction of separate equipment is required, and a large amount of electricity is consumed. I have. (4) To remove dioxin, expensive equipment is required. (5) It is difficult to recover valuable metals.
JP-B-62-35004 JP-A-2-147792

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to increase the amount of combustible gas such as municipal waste, waste such as waste plastic, and combustible materials such as coal, and particularly from municipal waste. It is to generate with efficiency. It is another object of the present invention to provide a combustible gasifier that is suitable for recovering energy and that can easily generate high-pressure combustible gas. Another object of the present invention is to provide a gasification and fusion combustion method and apparatus capable of generating a combustible gas containing a large amount of combustible components and melting the combustion ash by the self-calorific value of the generated combustible gas. is there. In the present invention, the generated gas supplied to the melting furnace has a sufficient amount of heat to generate a high temperature of 1300 ° C. or more by its own heat, and is made to be a homogeneous gas containing char and tar. The incombustibles are discharged from the gasifier without any trouble. Still another object of the present invention is to provide a gasification method and apparatus capable of extracting and recovering valuable metals in municipal solid waste from a fluidized bed furnace in a reducing atmosphere without oxidizing. Further objects of the present invention will become apparent in the description of embodiments with reference to the drawings.

  In order to achieve the above object, the gasification furnace of the present invention includes a fluidized bed made of a fluidized medium in an apparatus for melting ash after gasifying municipal solid waste, wherein the fluidized bed is heated to a temperature of 450 ° C to 650 ° C. C., a fluidized-bed furnace that receives municipal solid waste and is heated in the fluidized-bed to generate gas and char, and the gas and the char generated from the fluidized-bed furnace are introduced, and oxygen or oxygen is introduced. And a melting furnace for introducing a mixed gas of air and air, burning the gas and the char, and melting ash accompanying the char.

  Further, the gasification method of the present invention is a method of melting ash after gasifying municipal solid waste, wherein the temperature of the fluidized bed in the fluidized bed furnace is maintained at 450 ° C. to 650 ° C. Heating in a fluidized bed to generate gas and char, supplying the gas and char generated from the fluidized bed furnace to the melting furnace, and introducing oxygen or a mixed gas of oxygen and air to the melting furnace. And burning the gas and the char to melt ash accompanying the char.

  (1) The gasifier of the present invention can have a high load and can have a small furnace.

  (2) In the present invention, since the fluidized-bed furnace can maintain combustion with a small amount of air, the fluidized-bed furnace is set to a low air ratio and low temperature (450 to 650 ° C.) to minimize heat generation and slowly burn. By doing so, a homogeneous product gas containing a large amount of flammable components can be obtained, and most of the flammable components of gas, tar, and char can be used in the next-stage fusion combustion furnace.

  (3) In the present invention, iron and aluminum in incombustibles can be used as unoxidized valuables.

  (4) According to the present invention, there is provided a method or equipment which makes garbage disposal harmless and has a high energy utilization rate.

  In the present invention, the central fluidizing gas is one of three gases: steam, a mixture of steam and air, and air. In addition, the peripheral fluidizing gas is one of three types of gas: oxygen, a mixed gas of oxygen and air, and air. Therefore, there are nine combinations of central fluidizing gas and peripheral fluidizing gas, as shown in Table 1. Which combination is selected depends on whether importance is placed on gasification efficiency or economy.

  The combination having the highest gasification efficiency is No. Although the combination is 1, the cost is high because of the large amount of oxygen consumption. The order of decreasing oxygen consumption and then steam consumption decreases gasification efficiency, but also reduces cost. The oxygen used in the present invention may be of high purity or of low purity obtained using an oxygen-enriched membrane. No. The combination of air and air of No. 9 is known as combustion air of a conventional incinerator. However, in the present invention in which the horizontal section of the fluidized bed furnace is circular, the downward projection of the inclined wall provided above the peripheral portion in the furnace is performed. Since the area is larger than the downward projected area of the inclined wall when the horizontal cross section of the fluidized bed furnace is rectangular, the flow rate of the peripheral fluidizing gas can be increased, and therefore the oxygen supply amount can be increased, so that the gasification efficiency is improved. Can be done.

  Preferably, the method of the present invention further includes an intermediate fluidizing gas in which the fluidizing gas is supplied into the furnace from a middle portion of the bottom between the central portion and the peripheral portion of the bottom. The mass velocity of the intermediate fluidization gas is between the mass velocity of the central fluidization gas and that of the peripheral fluidization gas. The intermediate fluidizing gas is one of two types of gas: a mixture of steam and air, and air. Therefore, the number of combinations of the central fluidizing gas, the intermediate fluidizing gas, and the peripheral fluidizing gas is 18, and it is advantageous that the oxygen content increases in order from the central portion of the furnace to the peripheral portion, Preferred combinations are shown in Table 15 below.

  Which one of the combinations in Table 2 is selected depends on whether importance is placed on gasification efficiency or economic efficiency. Among the combinations in Table 2, the combination with the highest gasification efficiency is No. Although the combination is 1, the cost is high because the oxygen consumption is large. The order of decreasing oxygen consumption and then steam consumption decreases gasification efficiency, but also reduces cost. The oxygen used in Tables 1 and 2 may be of high purity or of low purity obtained using an oxygen-enriched film.

  When the fluidized bed furnace is large, the intermediate fluidizing gas is preferably a plurality of fluidizing gases supplied from a plurality of concentric intermediate portions provided between the central portion of the furnace bottom and the peripheral portion of the furnace bottom. . In this case, it is preferable that the oxygen concentration of the fluidizing gas be the lowest in the central part of the furnace and be higher as approaching the peripheral part.

  In the method of the present invention, preferably, the fluidizing gas supplied to the fluidized bed furnace contains an air amount of 30% or less of the theoretical combustion air amount required for combustion of combustibles. Incombustibles are taken out from the vicinity of the bottom of the fluidized bed furnace, classified, and the obtained sand is returned into the fluidized bed furnace. The combustible gas and fine particles generated in the fluidized bed furnace are burned at a high temperature of 1300 ° C. or more in the melting and burning furnace, and the ash is melted. The gas turbine is driven by the exhaust gas from the melting and burning furnace. The pressure in the fluidized bed furnace is maintained at or below atmospheric pressure or above atmospheric pressure depending on the application. Combustibles are waste, coal, and others.

  The present invention also provides an apparatus in which combustibles are gasified in a fluidized bed furnace. In the apparatus of the present invention, the fluidized bed furnace has a side wall having a substantially circular horizontal cross section, a fluidizing gas dispersion mechanism arranged at the bottom of the furnace, an incombustible material outlet arranged at an outer periphery of the fluidizing gas dispersion mechanism, and fluidization. Central supply means for supplying fluidized gas to flow vertically upward into the furnace from near the center of the gas dispersion mechanism, and flowing fluidized gas vertically upward into the furnace from the periphery of the fluidized gas dispersion mechanism. Peripheral supply means for supplying a fluidized gas flowing vertically upward from the peripheral supply means to the furnace central portion, and a free board disposed above the inclined wall, the central supply means comprising: The fluidizing gas having a relatively low mass velocity and a relatively low oxygen concentration is supplied, and the peripheral supply means supplies the fluidizing gas having a relatively high mass velocity and a relatively high oxygen concentration.

  In the apparatus of the present invention, there is provided an intermediate supply means for supplying the fluidized gas vertically upward into the furnace from the ring-shaped intermediate portion between the central portion and the peripheral portion of the fluidized gas dispersion mechanism. The intermediate supply means has a mass velocity intermediate between the mass velocities of the fluidizing gas supplied from the central supply means and the peripheral supply means, and an oxygen concentration intermediate between the oxygen concentrations of the fluidizing gas supplied from the central supply means and the peripheral supply means. Supply a concentration of fluidizing gas. The peripheral supply means can be formed by a ring-shaped supply box. The combustible material inlet is disposed above the fluidized bed furnace, the combustible material inlet drops the combustible material above the central supply means, and the fluidized gas dispersion mechanism is formed to be lower at the peripheral portion than at the central portion. it can.

  The incombustible material outlet may have a ring portion disposed on the outer periphery of the dispersing mechanism and a conical portion that decreases downward from the ring-shaped portion. The noncombustible material outlet may include a fixed amount discharger, a first seal swing valve, a swing cut valve, and a second seal swing valve arranged in series.

  The apparatus of the present invention may include a melting and burning furnace that burns combustible gas and fine particles generated in a fluidized bed furnace at a high temperature to melt ash. The melting and burning furnace has a cylindrical primary combustion chamber having a substantially vertical axis, and a combustible gas inlet for supplying the combustible gas and fine particles generated in the fluidized bed furnace to the cylindrical primary combustion chamber in a swirling manner around the axis. A secondary combustion chamber communicated with the cylindrical primary combustion chamber; and a discharge port provided at a lower portion of the secondary combustion chamber and capable of discharging molten ash. Exhaust gas from the secondary combustion chamber of the melting and burning furnace is introduced into a waste heat boiler and an air preheater, and waste heat is recovered. The gas turbine can be driven by the exhaust gas from the secondary combustion chamber of the melting combustion furnace. The exhaust gas can be released to the atmosphere after being introduced into the dust collector and the dust is removed. Exhaust gas from the secondary combustion chamber of the melting and burning furnace is introduced into a waste heat boiler and an air preheater, and waste heat can be recovered. The gas turbine can be driven by the exhaust gas from the secondary combustion chamber of the melting combustion furnace. The exhaust gas is introduced into the dust collector, and is discharged into the atmosphere after dust is removed.

In the gasifier of the present invention, heat is diffused by the circulating flow of the fluidized-bed furnace, so that the load can be increased and the furnace can be downsized.
In the present invention, since the fluidized-bed furnace can maintain combustion with a small amount of air, the fluidized-bed furnace is set to a low air ratio and a low temperature (450 to 650 ° C.), and the heat generation is minimized, and the fluidized-bed furnace is slowly burned. As a result, a homogeneous product gas containing a large amount of combustibles can be obtained, and most of the combustibles of gas, tar, and char can be used in the next stage combustion furnace.
In the present invention, large incombustibles can be easily discharged by the circulating flow of the fluidized bed furnace. In addition, iron and aluminum in incombustibles can be used as unoxidized valuables.
In the method or apparatus of the present invention, the horizontal cross section of the fluidized bed furnace is made substantially circular, so that the furnace has a pressure-resistant structure, the fluidized bed furnace is pressurized above atmospheric pressure, and the combustible material supplied into the furnace is It is easy to make the pressure of the combustible gas generated from high pressure high. High-pressure flammable gas can be used as fuel for gas turbines and boiler / gas turbine combined plants that can operate with high efficiency, and therefore, by using flammable gas in such plants, energy from combustibles can be reduced. Recovery efficiency can be improved. In the method or the apparatus of the present invention, when mainly treating refuse, in order to prevent odor and harmful combustion gas from leaking from the fluidized bed furnace, it is preferable that the furnace pressure is equal to or lower than the atmospheric pressure. Since the horizontal cross section of the fluidized bed furnace is circular, the furnace wall can easily withstand external pressure.

  In the present invention, the mass velocity of the central fluidizing gas supplied to the fluidized bed furnace is made smaller than the mass velocity of the peripheral fluidizing gas, and the upward flow of the fluidizing gas above the peripheral part in the furnace is changed to the central part of the furnace. As a result, a moving bed in which the flowing medium is settled and diffused is formed in the center of the furnace, and a fluidized bed in which the flowing medium is actively fluidized is formed in the periphery of the furnace. The combustibles supplied into the furnace are gasified into combustible gas while circulating with the fluidized medium from the lower part of the moving bed to the fluidized bed and from the top of the fluidized bed to the moving bed. The combustibles are first gasified in the descending moving bed in the center of the furnace, mainly by the volatiles due to the heat of the flowing medium (typically using silica sand). And, since the oxygen content of the central fluidizing gas forming the moving bed is small, the combustible gas generated in the moving bed is hardly burned and rises to the freeboard together with the central fluidizing gas, and the calorific value is high. It becomes a high quality product gas.

  The combustibles, which have lost volatiles and are heated in the moving bed, that is, fixed carbon (char) and tar, are then circulated into the fluidized bed, and peripheral fluidization with a relatively high oxygen content in the fluidized bed. The gas is burned in contact with the gas, converted into combustion gas and ash, and generates combustion heat that maintains the inside of the furnace at 450 to 650 ° C. The fluidized medium is heated by the heat of combustion, and the heated fluidized medium is turned to the central part of the furnace above the peripheral part of the furnace and descends in the moving bed, thereby lowering the temperature in the moving bed to a temperature required for gasification of volatile matter. To maintain. Since the center of the furnace where the combustibles are charged is in a low oxygen state, a product gas having a high combustible content can be generated. In addition, the metals in the combustibles can be recovered from the incombustibles outlet as unoxidized valuables.

  In the present invention, when the gas, ash, and other fine particles generated in the fluidized bed furnace are burned in the melting and burning furnace, the generated gas contains a high flammable content, so that no heating fuel is required, and the inside of the melting furnace is not required. Can be raised to a high temperature of 1300 ° C. or more, and the ash can be sufficiently melted in the melting furnace. The molten ash can be easily taken out of the melting furnace and solidified by a known method such as water cooling. Thus, the ash volume is significantly reduced and the harmful metals in the ash are solidified, leaving the ash in a landfillable form. Other effects of the present invention will be apparent from the claims and the description of the embodiments with reference to the drawings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto, but is defined by the claims. In addition, in FIGS. 1 to 14, members denoted by the same reference numerals are the same members or corresponding members, and redundant description is omitted in the description of each drawing.

  FIG. 1 is a schematic longitudinal sectional view of a main part of a gasifier of a first embodiment for carrying out the gasification method of the present invention, and FIG. 2 is a schematic horizontal sectional view of the gasifier of FIG. is there. In the gasifier shown in FIG. 1, the fluidizing gas supplied into the fluidized bed furnace 2 through the fluidizing gas dispersing mechanism 106 arranged at the furnace bottom flows upward from the vicinity of the center 4 of the furnace bottom into the furnace. And a peripheral fluidizing gas 8 supplied as an upward flow from the furnace bottom peripheral portion 3 into the furnace.

  As shown in Table 1, the central fluidizing gas 7 is one of three types of gas: steam, a mixed gas of steam and air, and air, and the peripheral fluidizing gas 8 is oxygen, oxygen and A mixture of air and one of three types of air. The oxygen content of the central fluidizing gas is less than or equal to the oxygen content of the peripheral fluidizing gas. The air amount of the entire fluidizing gas is set to 30% or less of the theoretical combustion air amount necessary for combustion of the combustibles 11, and the inside of the furnace is set to a reducing atmosphere.

  The mass velocity of the central fluidizing gas 7 is less than the mass velocity of the peripheral fluidizing gas 8 and the upward flow of the fluidizing gas above the perimeter in the furnace is diverted by the deflector 6 to the central part of the furnace. . As a result, a moving bed 9 in which the fluidized medium (usually silica sand) is settled and diffused is formed in the center of the furnace, and a fluidized bed 10 in which the fluidized medium is actively fluidized is formed in the periphery of the furnace. Is done. The fluidized medium rises in the fluidized bed 10 around the furnace, as shown by the arrow 118, is then turned by the deflector 6, flows above the moving bed 9, descends in the moving bed 9, and then moves down the arrow. As shown by 112, it moves along the gas dispersion mechanism 106 and flows below the fluidized bed 10 to circulate through the fluidized bed 10 and the moving bed 9 as shown by arrows 118 and 112.

  The combustible material 11 supplied from the combustible material supply port 104 to the upper part of the moving bed 9 is heated by the heat of the flowing medium while descending in the moving bed 9 together with the flowing medium, and mainly the volatile matter is gasified. . Since there is no or little oxygen in the moving bed 9, the generated gas composed of the gasified volatiles is not burned and passes through the moving bed 9 as indicated by an arrow 116. Therefore, the moving bed 9 forms the gasification zone G. The product gas that has moved to the free board 102 rises as indicated by an arrow 120 and is discharged from the gas outlet 108 as the product gas 29.

  Mainly char (fixed carbon content) and tar 114 which are not gasified in the moving bed 9 move from the lower part of the moving bed 9 to the lower part of the fluidized bed 10 in the peripheral part of the furnace together with the fluidized medium as shown by an arrow 112, It is burned by the peripheral fluidizing gas 8 having a relatively high oxygen content and is partially oxidized. The fluidized bed 10 forms an oxidation zone S for combustibles. In the fluidized bed 10, the fluidized medium is heated by combustion heat in the fluidized bed to a high temperature. The high temperature fluid medium is inverted by the inclined wall 6 as shown by an arrow 118, moves to the moving bed 9, and becomes a heat source for gasification again. The temperature of the fluidized bed 10 is maintained at 450 to 650 ° C. so that the suppressed combustion reaction continues.

  According to the gasification furnace 1 shown in FIGS. 1 and 2, the gasification zone G and the oxidation zone S are formed in the fluidized bed furnace 2, and the fluidized medium serves as a heat transfer medium in both zones. , A high-quality combustible gas having a high calorific value is generated, and in the oxidation zone S, char and tar 114 that are difficult to gasify can be efficiently burned. Therefore, the gasification efficiency of combustibles can be improved, and high-quality combustible gas can be generated.

In the horizontal section of the fluidized bed furnace 2 shown in FIG. 2, the moving bed 9 forming the gasification zone G is circular at the center of the furnace, and the fluidized bed 10 forming the oxidation zone S is formed around the moving bed 9. It is formed in a ring shape. A ring-shaped incombustible substance discharge port 5 is arranged on the outer periphery of the fluidized bed 10. By making the gasification furnace 1 cylindrical, a high furnace pressure can be easily supported. A pressure vessel (not shown) can be separately provided outside the gasification furnace, instead of the structure in which the gasification furnace itself receives the internal pressure of the gasification furnace.

  FIG. 3 is a schematic vertical sectional view of a main part of a gasifier of a second embodiment for carrying out the gasification method of the present invention, and FIG. 4 is a schematic horizontal sectional view of the gasifier of FIG. is there. In the gasifier of the second embodiment shown in FIG. 3, the fluidizing gas includes a central fluidizing gas 7 and a peripheral fluidizing gas 8, and a middle portion of the furnace bottom between the central portion of the furnace bottom and the peripheral portion of the furnace bottom. And an intermediate fluidizing gas 7 'supplied into the furnace from the furnace. The mass velocity of the intermediate fluidizing gas 7 ′ is chosen between the mass velocity of the central fluidizing gas 7 and the peripheral fluidizing gas 8. The intermediate fluidizing gas is any one of three types of gas: steam, a mixture of steam and air, or air.

  In the gasifier of FIG. 3, as in the case of the gasifier of FIG. 1, the central fluidizing gas 7 is one of three gases: steam, a mixture of steam and air, and air. The peripheral fluidizing gas 8 is one of three gases: oxygen, a mixed gas of oxygen and air, and air. The oxygen content of the intermediate fluidizing gas is selected between the oxygen content of the central fluidizing gas and the oxygen content of the peripheral fluidizing gas. Therefore, the preferred combinations of the fluidizing gases are 15 in Table 2. In each combination, it is important that the oxygen supply increases as it extends from the center to the periphery of the fluidized bed furnace. The air amount of the entire fluidizing gas is set to 30% or less of the theoretical combustion air amount necessary for combustion of the combustibles 11, and the inside of the furnace is set to a reducing atmosphere.

  As in the case of the gasifier of FIG. 1, in the gasifier of FIG. 3, a moving bed 9 in which a flowing medium settles is formed in the center of the furnace, and a moving bed 10 in which the flowing medium rises in the periphery of the furnace. Is formed. A fluidized medium circulates through the moving and fluidized beds as indicated by arrows 112 and 118. Between the moving bed 9 and the fluidized bed 10, an intermediate layer 9 'in which the fluidized medium diffuses mainly in the lateral direction is formed. The moving bed 9 and the intermediate layer 9 'form a gasification zone G, and the fluidized bed 10 forms an oxidation zone S.

  The combustible material 11 introduced into the upper part of the moving bed 9 is heated while descending in the moving bed 9 together with the fluidized medium, and the volatile matter is gasified. The char and tar not gasified in the moving bed 9 and some of the volatiles move to the intermediate layer 9 'and the fluidized bed 10 together with the fluidized medium, and are partially gasified and partially burned. Mainly char and tar which are not gasified in the intermediate layer 9 'move into the fluidized bed 10 around the furnace together with the fluidized medium and are burned in the peripheral fluidized gas 8 having a relatively high oxygen content. The fluidized medium is heated in the fluidized bed 10 and circulates to the moving bed 9 to heat the combustibles in the moving bed 9. Regarding the oxygen concentration of the intermediate layer, depending on the type of combustibles (whether there is a lot of volatile matter, or a lot of char and tar), etc., lower the oxygen concentration and mainly gasify, or increase the oxygen concentration. Whether oxidative combustion is the main component is selected.

In the horizontal section of the fluidized-bed furnace shown in FIG. 4, the moving bed 9 forming the gasification zone is circular at the center of the furnace, and has an intermediate zone 9 formed by the intermediate fluidized gas 7 'along the outer periphery thereof. And the fluidized bed 10 forming the oxidation zone is formed in a ring around the intermediate zone 9 '. A ring-shaped incombustible substance discharge port 5 is arranged on the outer periphery of the fluidized bed 10. By making the gasification furnace 1 cylindrical, a high furnace pressure can be easily supported. The furnace pressure can be received by the gasifier itself or by providing a separate pressure vessel outside the gasifier.

  FIG. 5 is a schematic vertical sectional view of a gasifier according to a third embodiment of the present invention. In the gasifier 1 of FIG. 5, the gasification raw material 11 made of combustibles such as refuse is supplied to the fluidized bed furnace 2 of the gasifier 1 by the double damper 12, the compression feeder 13, and the dust feeder 14. . The compression feeder 13 compresses the gasified raw material into a plug shape, thereby sealing the furnace pressure. The dust compressed in a plug shape is separated by a loosening device (not shown) and sent to the furnace by a dust feeder 14.

  In the gasifier of FIG. 5, the central fluidizing gas 7 and the peripheral fluidizing gas 8 are supplied in the same manner as in the embodiment of FIG. 1, and therefore are reduced to the fluidized bed furnace 2 in the same manner as in the embodiment of FIG. An atmosphere gasification zone and an oxidation zone are formed. The fluidized medium serves as a heat transfer medium in both zones, and in the gasification zone, high-quality combustible gas with a high calorific value is generated. In the oxidation zone, char and tar 114, which are difficult to gasify, are efficiently burned, resulting in high gasification. Efficiency and high quality combustible gas can be obtained. In the embodiment of FIG. 5, a roots blower 15 communicating with the double damper 12 and the free board 102 of the gasification furnace 1 is provided, and when the compression of dust is insufficient, the dust leaks from the furnace through the compression feeder to the double damper 12. Return the gas into the furnace. Preferably, the roots blower 15 sucks an appropriate amount of air and gas from the double damper 12 and returns it into the furnace so that the upper part of the double damper 12 is at atmospheric pressure.

  In the gasifier of FIG. 5, in order to discharge incombustibles from the fluidized-bed furnace 2, the incombustibles discharge port 5, the conical chute 16, the fixed-quantity discharger 17, the first swing valve for sealing 18, the swing cut valve 19, and the seal are used. The second swing valve for use 20 and the discharger with trommel 23 are arranged in order, and are operated as follows.

  (1) When the first swing valve 18 for sealing is opened, the second swing valve 20 is closed, and the furnace pressure is sealed by the second swing valve 20, the constant-rate discharger 17 is operated and the fluid medium is discharged. Is discharged from the conical chute 16 to the swing cut valve 19. (2) When the swing cut valve 19 receives a predetermined amount of incombustible material, the fixed amount discharger 17 is turned off, the first swing valve 18 is closed, and the furnace pressure is sealed by the first swing valve 18. Then, the discharge valve 22 is opened, and the inside of the swing cut valve 19 is returned to the atmospheric pressure. Next, the second swing valve 20 is completely opened, and the swing cut valve 19 is opened, so that incombustibles are discharged to the continuous discharger 23 with trommel. (3) After the second swing valve 20 is completely closed, the equalizing valve 21 is opened, and the inside of the first swing valve 18 and the inside of the conical chute 16 are equalized. The valve 18 is opened and returns to the first step (1). These steps (1) to (3) are automatically and repeatedly operated.

The continuous discharger 23 with trommel is operated continuously, discharges large incombustibles 27 out of the system by trommel, transports sand and small incombustibles by the sand circulation elevator 24, and removes fine incombustibles 28 by the classifier 25. After that, the sand is returned to the gasification furnace 1 via the lock hopper 26. In such an incombustible discharge mechanism, since the two swing valves have only a pressure sealing function without receiving incombustibles, it is necessary to avoid the incombustibles from being caught in the seal portions of the first and second swing valves 18 and 20. Can be. When the furnace pressure may be slightly negative, the sealing function is unnecessary.

  FIG. 6 is a schematic vertical sectional view of a gasifier according to a fourth embodiment of the present invention. In the gasifier of FIG. 6, the supply of the gasification raw material 11 and the sealing of the furnace pressure related thereto are performed in the same manner as the mechanism for discharging the non-combustible material shown in FIG. This is performed using a combination of the first and second swing valves 18. The compression feeder 13 has been removed. In the embodiment of FIG. 6, gas leaking from the furnace into the first swing valve 18 is returned to the furnace via the discharge valve 22 and a blower (not shown). After the first swing valve 18 is completely closed, the pressure equalizing valve 21 is opened, and the pressure in the swing cut valve 19 is made equal to the furnace internal pressure.

  FIG. 7 is a flowchart showing an example of the purification process of the product gas produced by the gasifier of the present invention. In the refining process of FIG. 7, the gasification raw material 11 and the fluidizing gases 7 and 8 are supplied to the gasification apparatus 1. The combustible gas generated in the gasifier 1 recovers heat in the waste heat boiler 31, is cooled, and is sent to the cyclone separator 32, where solids 37 and 38 are separated. Thereafter, the generated gas is washed and cooled by water in the water washing tower 33, and hydrogen sulfide is removed in the alkali washing tower 34, and then stored in the gas holder 35. The unreacted char 37 in the solids separated by the cyclone separator 32 is returned to the gasifier 1, and the remaining solids 38 are discharged out of the system. As in the embodiment of FIG. 5, of the non-combustibles discharged from the gasifier 1, large non-combustibles 27 are discharged out of the system, and sand is returned to the gasifier 1. The wastewater discharged from the washing towers 33 and 34 is introduced into a wastewater treatment device 36 and is treated for detoxification.

FIG. 8 is a flowchart showing an example of a process in which the combustible product gas and the fine particles generated in the gasifier 1 are introduced into the melting and burning furnace 41 and are burned at a high temperature to melt the ash. In the process of FIG. 8, the product gas having a high flammability produced by the gasifier 1 is introduced into the melting and burning furnace 41. Oxygen, a mixed gas of oxygen and air, or air is blown into the melting and burning furnace 41, the generated gas and fine particles are burned at 1300 ° C. or more, ash is melted, and harmful substances such as dioxin and PCB are decomposed. You. The ash 44 melted in the melting and burning furnace 41 is quenched, turned into slag, and reduced in weight. The combustion exhaust gas generated in the melting and burning furnace 41 is quenched by a scrubber 42 to prevent re-synthesis of dioxin. The exhaust gas quenched by the scrubber 41 is further filtered to remove the dust 38 and discharged from the exhaust tower 55 to the atmosphere.

  FIG. 9 is a vertical sectional perspective view of a gasification and melting and burning apparatus according to a fifth embodiment of the present invention. 9, the gasifier 1 is almost the same as the embodiment of FIG. 1, but the gas outlet 108 is connected to the combustible gas inlet 142 of the melting and burning furnace 41. The melt-burning furnace 41 includes a cylindrical primary combustion chamber 140 having a substantially vertical axis, and a secondary combustion chamber 150 inclined horizontally. The combustible gas 120 and fine particles generated in the fluidized bed furnace 2 are supplied to the primary combustion chamber 140 via the combustible gas inlet 142 so as to swirl around its axis.

  The primary combustion chamber 140 includes a starter burner at an upper end and a plurality of air nozzles 134 that supply combustion air in a swirling manner about an axis. The secondary combustion chamber 150 communicates with the primary combustion chamber 140 at the lower end thereof, and is disposed at a lower portion of the secondary combustion chamber and capable of discharging the molten ash, and an exhaust port disposed above the discharge port 152. An opening 154, an auxiliary burner 136 disposed near a portion communicating with the primary combustion chamber, and an air nozzle 134 for supplying combustion air are provided. The exhaust port 154 includes a radiation plate 162 to reduce the amount of heat lost from the exhaust port 154 due to radiation.

  FIG. 10 is a layout view of a fluidized bed gasification and melting and combustion apparatus according to an embodiment of the present invention used in combination with a waste heat boiler and a turbine. In FIG. 10, the gasifier 1 includes a conveyor 172 that conveys the large incombustibles 27 discharged from the discharger 23 and the fine noncombustibles 28 discharged from the classifier 25 together. An air jacket 185 is arranged around the conical chute 16 for taking out incombustibles from the lower part of the fluidized-bed furnace 2, and the air in the air jacket 185 is heated by hot extraction sand. The auxiliary fuel F is supplied to the primary and secondary combustion chambers 140 and 150 of the melting and burning furnace 41. The molten ash 44 discharged from the discharge port 152 of the melting and burning furnace 41 is received in the water chamber 178, rapidly cooled, and discharged as slag 176.

  In FIG. 10, the combustion gas discharged from the melting and burning furnace 41 is discharged to the atmosphere via the waste heat boiler 31, the economizer 183, the air preheater 186, the dust collector 43, and the induction ventilator 54. The combustion gas discharged from the air preheater 186 is added with a neutralizing agent N such as slaked lime before entering the dust collector 43. After the water W is supplied to the economizer 183 and preheated, the water W is heated by the boiler 31 into steam, and drives the steam turbine ST. After the air A is supplied to the air preheater 186 and heated, the air A is further heated in the air jacket 185 and supplied to the melting and burning furnace 41 and, if necessary, the free board 102 via the air pipe 184.

  The fine particles 180 and 190 collected at the bottom of the waste heat boiler 31, the economizer 183, and the air preheater 186 are conveyed to the classifier 25 by the sand circulation elevator 24 to remove fine incombustibles 28, and returned to the fluidized bed furnace 2. . The fly ash 38 separated in the filter 43 contains alkali metal salts such as Na and K volatilized at a high temperature, and is thus treated by a chemical in the processor 194.

  In the apparatus of FIG. 10, the combustion in the fluidized-bed furnace 2 is a low-temperature partial combustion at a low air ratio, and a high-calorie combustible gas can be generated by maintaining the fluidized-bed temperature at 450 ° C. to 650 ° C. it can. In addition, since combustion is performed in a reducing atmosphere at a low air ratio, iron and aluminum are obtained as non-oxidized valuables in non-combustibles. The high-calorie combustible gas and char generated in the fluidized bed furnace 2 can be burned at a high temperature of 1300 ° C. or more in the melting and burning furnace 41 to melt ash and decompose dioxin.

  FIG. 11 is a layout diagram of a fluidized bed gasification and melting and combustion apparatus according to an embodiment of the present invention used in combination with the gas cooling chamber 280. 11, the gasifier 1, the melting and burning furnace 41, the water chamber 178, the dust collector 43, the induction ventilator 54, and the like are the same as those in FIG. In FIG. 11, a gas cooler 280 and an independent air preheater 188 are provided in place of the waste heat boiler, and the gas cooler 280 is supplied from the melting and burning furnace 41 through a high-temperature duct 278 covered with refractory and heat-insulating material. To be introduced. In the gas cooler 280, the combustion gas is instantaneously cooled by the fine water spray to prevent re-synthesis of dioxin. The exhaust gas flow velocity of the high-temperature duct 278 is set to a low speed of 5 m / sec or less. A hot water generator 283 is arranged above the gas cooler 280. The air heated by the air preheater 188 is supplied to the free board 102 of the gasification furnace 1 and the melting and burning furnace 41.

  FIG. 12 is a layout diagram of a fluidized bed gasification and melting and burning apparatus according to an embodiment of the present invention used in combination with the waste heat boiler 31 and the reaction tower 310. 12, the gasifier 1, the melting and burning furnace 41, the water chamber 178, the waste heat boiler 31, the steam turbine ST, the economizer 183, the air preheater 186, the dust collector 43, the inducing fan 54, and the like are the same as FIG. The same is true. In FIG. 12, a reaction tower 310 and a superheater heating combustor 320 are disposed between the waste heat boiler 31 and the economizer 183. In the reaction tower 310, a neutralizing agent N such as slaked lime slurry is added to the combustion exhaust gas to remove HCl. The solid fine particles 312 discharged from the reaction tower 310 are sent to the classifier 25 by the sand circulation elevator 24 together with the solid fine particles 180 discharged from the waste heat boiler 31. In the heating combustor 320, the unburned gas and the auxiliary fuel F are burned, and the steam temperature is raised to about 500 ° C. In the apparatus shown in FIG. 12, the power generation efficiency can be about 30% because the steam has a high temperature and a high pressure and the air ratio is small and the sensible heat taken out of the exhaust gas is small.

  FIG. 13 is a layout view of a gasification cogeneration type fluidized bed gasification and fusion combustion apparatus according to an embodiment of the present invention. 13, a gasifier 1, a melting and burning furnace 41, a water chamber 178, a waste heat boiler 31, a dust collector 43, an induction fan 54, and the like are the same as those in FIG. In FIG. 13, a reaction tower 310 is disposed between the waste heat boiler 31 and the dust collector 43. In the reaction tower 310, a neutralizing agent N such as slaked lime slurry is added to the combustion exhaust gas to remove HCl. The exhaust gas from the reaction tower 310 is used in the gas turbine 420 via the dust collector 43. In the gas turbine 420, the air A is compressed by the compressor C and supplied to the combustor CC, and the fuel F is combusted in the combustor CC. Is the working fluid of the turbine T. The exhaust gas of the gas turbine 420 passes through the superheater 430, the economizer 440, and the air preheater 450 in this order, and is discharged to the atmosphere by the induction ventilator 54. The steam generated in the waste heat boiler 31 is heated by the exhaust gas of the gas turbine 420 in the super heater 430 and supplied to the steam turbine ST.

  FIG. 14 is a flow chart showing the steps of the fluidized bed gasification and melt combustion method of the combined pressurized gasification power generation type of the embodiment of the present invention. The high-temperature and high-pressure generated gas 29 generated in the pressurized gasification furnace 1 is introduced into the waste heat boiler 31 ′ to generate steam and cool itself. The product gas exiting the waste heat boiler is divided into two parts, one is added to the melting and burning furnace 41 and the other is added with the neutralizing agent N to neutralize the HCl and is introduced into the dust collector 43 '. In the dust collector 43 ', the low-melting substance in the product gas solidified by the temperature drop is separated from the product gas, sent to the melting and burning furnace 41, and melted. The product gas from which the low melting point material has been removed is used as a fuel gas in the gas turbine GT. Exhaust gas of the gas turbine GT is heat-exchanged by a super heater SH and an economizer ECo, and then processed by an exhaust gas processor 510 to be released into the atmosphere. The exhaust gas from the melting and burning furnace 41 is introduced into an exhaust gas processor 510 via a heat exchanger EX and a dust collector 43. The molten ash 44 discharged from the melting furnace is rapidly cooled into slag. The solid matter 38 discharged from the dust collector 43 is subjected to chemical treatment in a processor 194.

  According to the process of FIG. 14, the gas generated from the waste is used as a fuel after the HCl and solids are removed, so that the gas turbine is not corroded and the HCl is removed. Therefore, high-temperature steam can be generated by the gas turbine exhaust gas.

1 is a schematic vertical sectional view of a main part of a gasifier according to a first embodiment of the present invention. FIG. 2 is a schematic horizontal sectional view of a fluidized bed furnace of the gasifier of FIG. 1. FIG. 4 is a schematic vertical sectional view of a main part of a gasifier according to a second embodiment of the present invention. FIG. 3 is a schematic horizontal sectional view of a fluidized bed furnace of the gasifier of FIG. 2. FIG. 4 is a schematic vertical sectional view of a gasifier according to a third embodiment of the present invention. FIG. 4 is a schematic vertical sectional view of a gasifier according to a fourth embodiment of the present invention. The flowchart which shows an example of the refinement | purification process of a generated gas. The flowchart which shows an example of the process in which ash is melted. FIG. 13 is a schematic vertical sectional perspective view of a gasification and melting and burning apparatus according to a fifth embodiment of the present invention. 1 is a layout view of a fluidized bed gasification and melting and combustion apparatus according to an embodiment of the present invention used in combination with a waste heat boiler and a turbine. FIG. 2 is a layout view of a fluidized bed gasification and fusion combustion apparatus according to an embodiment of the present invention used in combination with a gas cooling chamber. 1 is a layout view of a fluidized bed gasification and melting and burning apparatus according to an embodiment of the present invention used in combination with a waste heat boiler and a reaction tower. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a layout diagram of a fluidized bed gasification and melting and combustion apparatus according to a gasification cogeneration type embodiment of the present invention. FIG. 2 is a flow chart showing steps of a fluidized bed gasification and melt combustion method according to an embodiment of the combined pressurized gasification power generation type of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1; Gasification apparatus, 2; Fluidized bed furnace, 3; Furnace bottom peripheral part, 4; Furnace bottom central part, 5; Noncombustible material discharge port, 6; Inclined wall, 7; Central fluidizing gas, 7 '; Gasification gas, 8; Peripheral fluidization gas, 9; Moving bed, 9 '; Intermediate layer, 10; Fluidized bed, 11; Gasification raw material (combustible material), 12; Double damper, 13; Compression feeder, 14; Feeder, 15; Roots blower, 16; Conical chute, 17; Constant discharger, 18, 20; Swing valve, 19, 19 '; Swing cut valve, 22; Discharge valve, 23; Continuous discharger with trommel, 24; Recirculation elevator, 25; Classifier, 27, 28; Noncombustible, 29; Product gas, 31, 31 '; Waste heat boiler, 32; Cyclone separator, 36; Wastewater treatment unit, 37; Unreacted char, 38; Min, 41; melting and burning furnace, 43, 43 '; dust collector, 44; melting Induction ventilator, 55; Exhaust tower, 102; Free board, 104; Combustible material supply port, 106; Gas dispersion mechanism, 108; Gas outlet, 114; Char tar, 134; Combustion burner, 140; Primary combustion Combustion gas inlet, 150; Secondary combustion chamber, 162; Radiant plate, 176; Slag, 178; Water chamber, 183; Economizer, 185; Air jacket, 186, 188; Air preheater, 194, 510; Processor, 280; Gas cooler, 310; Reaction tower, 320; Super heater heating combustor, 420; Gas turbine, A; Air, C; Compressor, CC; Combustor, ECo; Economizer, F: Auxiliary fuel, G: gasification zone, N: neutralizer, S: oxidation zone, SH: super heater, ST: steam turbine, T: turbine, W: water.

Claims (6)

After gasifying municipal solid waste, the ash melts,
A fluidized bed furnace comprising a fluidized bed made of a fluidized medium, maintaining the temperature of the fluidized bed at 450 ° C. to 650 ° C., receiving municipal solid waste, and heating the fluidized bed to generate gas and char;
Introducing the gas and the char generated from the fluidized bed furnace and introducing oxygen or a mixed gas of oxygen and air, and burning the gas and the char to melt ash accompanying the char. Furnace and
A gasification and melting apparatus characterized by having: The gasification and melting apparatus according to claim 1, wherein the gas and the char are burned at 1300 ° C or more in the melting furnace. The melting furnace includes a cylindrical combustion chamber having a substantially vertical axis, and the gas and char generated in the fluidized bed furnace are transferred from an upper end of the cylindrical combustion chamber around the axis of the cylindrical combustion chamber. It is made to supply so as to turn,
The gas according to claim 1 or 2, further comprising a plurality of nozzles for supplying the oxygen or the mixed gas of oxygen and air to the upper end portion of the cylindrical combustion chamber so as to swirl around the axis. And melting equipment. In the method of melting ash after gasifying municipal solid waste,
Maintaining the temperature of the fluidized bed in the fluidized bed furnace at 450 ° C. to 650 ° C., receiving municipal solid waste and heating in the fluidized bed to generate gas and char,
Supplying the gas and the char generated from the fluidized bed furnace to the melting furnace,
Introducing oxygen or a mixed gas of oxygen and air into the melting furnace,
Melting the ash accompanying the char by burning the gas and the char;
A gasification and melting method characterized by the above-mentioned. 4. The gasification and melting method according to claim 3, wherein the gas and the char are burned at 1300 [deg.] C. or more in the melting furnace. The melting furnace includes a cylindrical combustion chamber having a substantially vertical axis, and the gas and char generated in the fluidized bed furnace are transferred from the upper end of the cylindrical combustion chamber to the axis of the cylindrical combustion chamber. Supply to swirl around
The gasification and gasification system according to claim 4 or 5, wherein the oxygen or the mixed gas of oxygen and air is supplied so as to swirl around the axis at an upper end portion of the cylindrical combustion chamber. Melting method.

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