JP2008248068A - Method for gasifying waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for gasifying wastes, designed to stabilize the gasification of a carbonized product in a moving bed-type gasification furnace. <P>SOLUTION: The method for gasifying wastes comprises the following process: A packed bed is formed by charging a vertical-type gasification furnace with a carbonized product formed by pyrolyzing wastes. An oxidizing agent gas is then fed from below the packed bed to form a combustion zone and a pyrolysis zone by partial combustion. A generated gas is discharged via the top of the furnace, while combustion residues are ejected via the bottom of the furnace. In this process, a solid product made by mixing the carbonized product in a powdery form with an inorganic binder to effect hardening in the form of pellets is charged into the gasification furnace, thereby stabilizing forming the packed bed's combustion zone and enabling the carbonized product to be stably gasified. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a waste gasification method, and more particularly to a waste gasification method using a moving bed type gasification furnace.

  Conventionally, as a method for treating industrial waste such as municipal waste from homes and offices, waste plastic, car shredder dust, electronic equipment, cosmetics, etc., these wastes are decomposed into pyrolysis furnaces (for example, And pyrolyzing in a low oxygen atmosphere to produce pyrolysis gas and pyrolysis residue mainly composed of non-volatile components, cooling the pyrolysis residue, and then mainly using pyrolysis carbon Combustible material (hereinafter referred to as carbide) is separated, and the separated carbide and pyrolysis gas are introduced into a combustion melting furnace for combustion treatment, and the resulting combustion ash is melted with high-temperature combustion heat to form molten slag. Nonetheless, a method of discharging this molten slag and solidifying by cooling is known. As described above, in the combustion treatment of waste, the pyrolysis gas and carbide obtained by pyrolyzing the waste are used as the heat source of the combustion melting furnace.

  On the other hand, in recent years, attempts have been made to use the pyrolysis gas of carbide as a gas fuel for a gas engine or the like. For example, a biomass gasification method is disclosed in which a carbide generated by pyrolyzing biomass is put into a partial combustion gasification furnace and partially combusted, and the generated combustible gas is used as gas fuel (see Patent Document 1). .)

  On the other hand, the present inventors have reported a technique relating to a moving bed type gasification furnace as a method for gasifying waste such as wood chips and general waste (see Patent Document 2). For example, pulverized waste is put into a vertical gasification furnace to form a packed bed, oxidant gas is supplied from the bottom of the furnace to cause partial combustion, combustion zone, pyrolysis zone, drying in the furnace height direction A gas fuel can be obtained by forming a band, extracting combustion residues from the bottom of the furnace, collecting the generated gas discharged from the top of the furnace, and appropriately performing a reforming treatment.

  Thus, by using the moving bed type gasification furnace and gasifying the pyrolyzed carbide, the product gas can be efficiently recovered.

Japanese Patent Laid-Open No. 2005-112956 Japanese Patent Laid-Open No. 2004-2552

  However, when the carbide is gasified using the moving bed type gasification furnace described in Patent Document 2, most of the carbide separated from the pyrolysis residue is in a fine powder form. For example, the pressure loss of the packed bed is low. There is a possibility that the supply of oxidant gas will be insufficient, or the packed bed will be fluidized and the formation of the combustion zone will become unstable, and the gasification efficiency of the carbide will be reduced.

  An object of the present invention is to stabilize the gasification of carbides in a moving bed type gasifier.

  In order to solve the above problem, the present invention forms a packed bed by introducing carbide generated by pyrolyzing waste into a vertical gasification furnace, and oxidant gas is supplied from below the packed bed. This is a waste gasification method in which a combustion zone and a pyrolysis zone are formed by partial combustion, a product gas is discharged from the top of the furnace, and a combustion residue is extracted from the bottom of the furnace. A solid material mixed with an inorganic binder and solidified into a pellet is put into a gasification furnace.

  In this way, the powdered carbide obtained by pyrolysis is solidified to form a solid having a predetermined size and weight, and this solid is put into a gasification furnace to be packed into a packed bed. Since voids are formed, increase in pressure loss and fluidization can be suppressed, and the gasification of carbide can be stabilized. In addition, since the carbide is solidified using an inorganic binder, when the solid passes through a high-temperature combustion zone, it can be kept in a predetermined shape without melting or pulverizing. .

  In addition, since the inorganic binder is relatively stable both chemically and thermally, it can be reused for solidifying the carbide even when it is extracted from the furnace bottom, regardless of the original state.

  In this case, for example, the combustion residue extracted from the bottom of the furnace is classified, and a granular material having a particle size of a predetermined size or more is used as a solid inorganic binder. According to this, sorting becomes easy and recycling can be automated.

  Here, the inorganic binder preferably contains at least one of calcium hydroxide, slaked lime, calcium carbonate, alumina, magnesium hydroxide, magnesium oxide, magnesium carbonate, and diatomaceous earth. Since these inorganic binders are generally commercially available, they are easily available and economical.

In the gasification furnace, it is preferable to supply water vapor together with the oxidant gas from below the packed bed. According to this, since a part of the hydrocarbon content (char) generated when the carbide is pyrolyzed reacts with water vapor and is converted into CO and H ₂ , the gasification efficiency can be further improved. .

  Moreover, it is preferable that the product gas discharged | emitted from the gasification furnace thermally decomposes the tar content contained in product gas, for example by guide | inducing to a reforming furnace and carrying out partial combustion. For example, in the process of ascending the packed bed, most of the tar content in the gas is cooled and condensed in the process of ascending the packed bed, and is removed by adhering to the packing, but a slight tar content remains in the gas. Sometimes. Therefore, the product gas can be purified by partially combusting the product gas at the subsequent stage of the gasification furnace, and heating and pyrolyzing the tar content.

  ADVANTAGE OF THE INVENTION According to this invention, the gasification of the carbide | carbonized_material in a moving bed type gasification furnace can be stabilized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a system diagram of a waste gasification system according to a first embodiment to which the waste gasification method of the present invention is applied. This waste gasification system is suitably used for gasification of general waste, industrial waste, biomass and the like (hereinafter referred to as waste), but is not limited thereto.

  As shown in FIG. 1, the waste gasification system of this embodiment includes a pyrolysis drum 1, a solidification device 3, a moving bed type gasification furnace 5, a classifier 7, a gas reforming furnace 9, and a gas purification device. 11 is provided.

  The inside of the pyrolysis drum 1 (also referred to as a pyrolysis kiln) is maintained in a low oxygen atmosphere by a seal mechanism (not shown), for example, and the exhaust gas of the downstream gas engine 15 is transmitted from the line L1 to the pyrolysis drum 1. It is supplied to the heat pipe. The exhaust gas supplied to the pyrolysis drum 1 is exhausted from the chimney 17 after the inside is heated through the heat transfer tube. The waste thrown into the pyrolysis drum 1 is heated to a predetermined temperature (for example, 300 to 600 ° C., usually about 450 ° C.) and pyrolyzed, and by this pyrolysis, mainly non-volatile pyrolysis residue and pyrolysis are performed. Gas (dry distillation gas) is generated. This pyrolysis gas is supplied from the line L2 to the gas reforming furnace 9, and the tar content is removed by partial combustion.

  The pyrolysis residue discharged from the pyrolysis drum 1 is burned by removing non-combustible materials such as metal, ceramics, gravel, or debris of concrete pieces by the separation device 13 connected to the subsequent stage of the pyrolysis drum 1. The powdered carbides of the sex component are fractionated. The powdered carbide is sent to the solidifying device 3 and solidified into a predetermined shape and size, and becomes a pellet-like solid (hereinafter simply referred to as a pellet). This pellet is supplied to the gasification furnace 5 to form a packed bed. The gasification furnace 5 burns a part of the packed bed and discharges the generated gas.

  FIG. 2 is a configuration diagram illustrating an example of a main part of the moving bed type gasification furnace 5. As shown in the figure, the gasification furnace 5 is provided with an inlet 23 for introducing carbide pellets at the top of a cylindrical vertical container 21. For example, a carbide pellet carrier (for example, a screw feeder) is connected to the insertion port 23.

  A gas discharge port 25 for discharging the generated gas is provided above the container 21, and a gasifying agent supply port 27 for supplying a combustion oxidant gas (for example, air) and water vapor is provided at the bottom. ing. The gasifying agent supply port 27 is formed, for example, at the tip of the rotary shaft 29 of the rotary extractor 28 provided at the bottom. The rotary shaft 29 of the rotary extractor 28 is connected to a motor 31 so that the rotating blades 33 are rotated along with the rotation of the rotary shaft 29 so that the combustion residue of the pellets is cut out in the radial direction and extracted from the discharge port 35. It has become.

  The product gas discharged from the gas outlet 25 of the gasification furnace 5 is supplied to the gas reforming furnace 9 through a line L3, and air (oxygen) is supplied through another line. The outlet of the gas reforming furnace 9 is connected to the gas purification device 11. The gas purification device 11 includes, for example, a gas cooling tower, a condensation tower, an adsorption tower, and the like. The gas purified through the gas purifier 11 is stored in a gas holder (not shown) and then supplied to the gas engine 15. On the other hand, the waste water discharged from the gas purification device 11 is guided to the waste water treatment device 19 for waste water treatment.

  Next, the pellet manufacturing method and gasification operation will be described in detail.

  The powdered carbide guided to the solidifying device 3 is kneaded by adding an inorganic binder and water at a predetermined ratio (for example, the weight ratio of carbide: inorganic binder: water is 100: 10-30: 10-20). Then, pellets having a predetermined shape and size (for example, a cylindrical shape of φ8 mm × 20 to 30 mm) are formed. The pellets are solidified to such an extent that the shape can be maintained in the state of the molded body.

  The carbide pellets thus solidified are charged into the furnace through the charging port 23 of the gasification furnace 5 to form a packed bed from the bottom. The input amount of pellets is adjusted so that a predetermined space, that is, a set height of the packed bed is secured at least at the top of the gasification furnace 1.

  Ignition is performed by supplying an oxidizing agent from the gasifying agent supply port 27 into the gasification furnace 1 filled with pellets and blowing high-temperature air from a hot air blower not shown. Then, the supply amount of the oxidant gas is adjusted, and the combustion zone is formed mainly by partially burning only the packed bed at the bottom of the furnace. The upper layer of the packed bed is heated and pyrolyzed by the combustion heat of this combustion zone, and the generated pyrolysis gas rises in the furnace through the packed bed, that is, the gap between the pellets, and is discharged from the gas outlet 25. .

When the partial combustion and thermal decomposition of the packed bed become stable, a stable combustion zone 41 is formed from the vicinity of the bottom, a thermal decomposition zone 43 is formed at the top, and a drying zone 45 is formed at the top. Is done. For example, when the carbide reaches about 300 ° C. or more, it is thermally decomposed. Therefore, the region of the packed layer that exceeds this temperature region becomes the thermal decomposition zone 43. In the pyrolysis zone 43, the carbide component of the pellet is pyrolyzed to generate a combustible pyrolysis gas and a small amount of carbon (char). A part of the char generated here reacts with water vapor supplied from the gasifying agent supply port 27 to generate CO and H ₂ .

  The produced gas thus produced dries the pellets in the drying zone 45 in the process of rising through the gaps in the upper packed bed. As a result, the product gas is heat-exchanged with the waste to be reduced in temperature (for example, about 200 ° C.) and discharged from the gas discharge port 25.

  On the other hand, the pellets dried in the drying zone 45 are pyrolyzed in the course of moving downward in the pyrolysis zone 43 by the rotational operation of the rotary extractor 28, and then move to the combustion zone 41. Pyrolysis and combustion to ash.

  Here, the pellets are burnt by burning the carbide, but since the skeleton is formed by the inorganic binder, the pellets are not pulverized when passing through the combustion zone 41, and the shape can be kept stable. it can. Thereby, the combustion zone 41 can also be uniformly formed in a predetermined furnace height position in the horizontal direction. Further, since voids are formed in the packed bed, an increase in pressure loss is suppressed, and the oxidant gas can be supplied uniformly in the cross-sectional direction.

  Combustion residues, which are formed by burning the carbides into ash and inorganic binder, flow down the cooling zone 47 formed in the lower layer of the combustion zone 41, and are cut out by the rotary extractor 28 and discharged from the outlet 35 to the outside of the furnace. The

In the present embodiment, calcium hydroxide (Ca (OH) ₂ ) is used as the inorganic binder constituting the pellet. This calcium hydroxide releases water at about 580 ° C. to become slaked lime (CaO). Since the melting point of slaked lime is about 2000 ° C. or higher, it is not melted even in a combustion zone (for example, about 1000 ° C.), and is directly discharged from the bottom together with ash. For this reason, slaked lime can also be used as an inorganic binder. Other inorganic binders include, for example, calcium carbonate (CaCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), alumina (Al ₂ O ₃ ), magnesium hydroxide (Mg (OH) ₂ ), magnesium oxide ( MgO), magnesium carbonate (MgCO ₃ ), diatomaceous earth (SiO ₂ ), or the like can be used. These may be used alone or in combination.

  The ash and inorganic binder discharged from the gasification furnace 5 are pulverized as necessary and then guided to the classifier 7. In the classifier 7, for example, after sieving with a 1 mm sieve, the remaining residue excluding the ash that has passed through the sieve is recovered as an inorganic binder and reused. That is, the inorganic binder selected by the classifier 7 is transferred to the solidifying device 3 and mixed with the carbide.

  On the other hand, the gas reforming furnace 9 is supplied with the product gas from the gasification furnace 5 through the line L3 and is supplied with the pyrolysis gas from the pyrolysis drum 1 through the line L2. In the gas reforming furnace 9, these gases are heated to a predetermined temperature (for example, about 800 ° C.) by partial combustion using combustion air supplied by a separate system. By this heating, the tar content in the product gas and pyrolysis gas is decomposed and removed. Moreover, when water vapor | steam is contained in gas, since water-gasification reaction advances in a furnace, gasification efficiency can further be improved.

  The reformed gas thus partially burned in the gas reforming furnace 9 and discharged from the furnace is cooled and purified through the gas purifier 11 and temporarily stored in the gas holder. Supplied as

  As described above, in the present embodiment, fine powdered carbide derived from the thermal decomposition residue of waste is mixed with an inorganic binder and solidified to form a pellet-like solid, and then the solid is moved to a moving bed. Introduced into a gasification furnace of the type, so as to form a packed bed, in the gasification furnace, while suppressing an increase in the pressure loss of the packed bed, stabilizing the formation of the combustion zone, gasifying the carbide Efficiency can be improved.

  Conventionally, in a moving bed type gasification furnace, in order to stabilize gasification, incombustible pellets of a predetermined size have been added together with waste, but according to this embodiment, Since solid matter itself becomes a moving medium and plays the role of non-combustible pellets, there is an advantage that non-combustible pellets are unnecessary.

  Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is a system diagram of a waste gasification system according to a second embodiment to which the waste gasification method of the present invention is applied. In addition, about the structure same as FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In this waste gasification system, the solidification device 3 is installed outside the facility of the waste gasification system, and the pelletized carbide outside the facility is introduced into the gasification furnace 5 in the facility for gasification. The other configuration is basically the same as that of the first embodiment. Since the thermal decomposition drum 1 is not provided in the facility, the exhaust gas discharged from the gas engine 15 is discharged from the chimney 17 to the atmosphere.

  Even if comprised in this way, the effect similar to 1st Embodiment can be acquired by conveying the solidified material of a carbide | carbonized_material in a facility, and in addition, the design freedom of an installation can be raised. .

  In the present embodiment, the example in which the carbide is solidified using the solidification device 3 installed outside the facility of the waste gasification system has been described. However, the present invention is not limited to this example. For example, the carbide is collected outside the facility. Even when the carbide is solidified by the solidification device 3 installed in the facility, the same effect can be obtained.

1 is a system diagram of a waste gasification system according to a first embodiment to which a waste gasification method of the present invention is applied. It is a block diagram explaining the principal part of the moving bed type gasification furnace which implements the waste gasification method of this invention. It is a systematic diagram of the waste gasification system of 2nd Embodiment formed by applying the waste gasification method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal decomposition drum 3 Solidification apparatus 5 Gasification furnace 7 Classifier 9 Gas reforming furnace 11 Gas purification apparatus 13 Separation apparatus 15 Gas engine

Claims (5)

Carbide produced by pyrolyzing waste is put into a vertical gasification furnace to form a packed bed, and oxidant gas is supplied from below the packed bed to burn the combustion zone and pyrolysis by partial combustion. A waste gasification method in which a belt is formed and the generated gas is discharged from the furnace top and combustion residue is extracted from the furnace bottom,
A waste gasification method, wherein a solid material obtained by mixing the powdered carbide material with an inorganic binder and solidifying into a pellet is put into the gasification furnace.   2. The waste gasification method according to claim 1, wherein the combustion residue extracted from the bottom of the furnace is classified, and a granular material having a particle size of a predetermined size or more is reused as an inorganic binder of the solid material.   The waste according to claim 1 or 2, wherein the inorganic binder contains at least one of calcium hydroxide, slaked lime, calcium carbonate, alumina, magnesium hydroxide, magnesium oxide, magnesium carbonate, and diatomaceous earth. Gasification method.   The waste gasification method according to any one of claims 1 to 3, wherein water vapor is supplied together with the oxidant gas from below the packed bed.   The waste gasification method according to any one of claims 1 to 4, wherein the product gas discharged from the gasification furnace is partially combusted, and a tar content contained in the product gas is thermally decomposed. .

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