JP2006231301A - Gasification apparatus of waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce effect of tar on a rear flow side. <P>SOLUTION: This gasification apparatus of waste is provided with a waste gasification furnace forming a combustion zone by partial combustion, supplying an oxidizer from the lower side of a packed layer of waste supplied into a vessel, and discharging produced gas from an upper side of the vessel; and a reforming furnace gasifying tar by heating the produced gas discharged from the waste gasification furnace. Thus, the tar in the produced gas is thermally decomposed and converted to low molecular weight substance, to reduce effect of the tar on the rear flow side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a waste gasifier that processes waste using a moving bed gasifier.

  Conventionally, as a method of treating municipal waste, industrial waste, sewage sludge, etc. (hereinafter simply referred to as waste), waste is introduced into a gasification furnace to form a packed bed, and an oxidant is supplied from the bottom of the furnace. A moving bed type gasification furnace has been proposed in which waste is gasified by partially burning and forming a combustion zone, a pyrolysis zone, and a drying zone in the furnace height direction (see Patent Document 1). According to this, the waste in the drying zone can be heated and dried by the heat of the pyrolysis gas generated in the pyrolysis zone. Further, since fly ash and the like contained in the pyrolysis gas are removed in the process in which the pyrolysis gas rises in the drying zone, a relatively clean pyrolysis gas can be obtained.

Japanese Patent Laid-Open No. 2004-2552

  By the way, in the gas produced | generated by the gasification furnace of patent document 1, hydrogen, carbon monoxide, a carbon dioxide gas, water vapor | steam, a hydrocarbon, etc. are contained normally. However, for example, if the carbon compound in the waste is not sufficiently pyrolyzed, the product gas may contain a tar content.

  Thus, when the tar content is mixed into the product gas, for example, when the tar content is condensed in a wet gas cooling tower or the like provided on the downstream side of the gasification furnace, the cooling water is contaminated, or the equipment is It may adhere and cause trouble.

  An object of the present invention is to reduce the influence of the tar component on the wake side.

  In order to achieve the above object, the present invention supplies an oxidizing agent from below the packed bed of waste supplied into the container to form a combustion zone by partial combustion, and discharges the generated gas from above the container. In a waste gasification apparatus provided with a waste gasification furnace, a reforming furnace is provided that heats the product gas discharged from the waste gasification furnace to gasify the tar content.

  That is, the product gas discharged from the waste gasification furnace is guided to the reforming furnace on the downstream side and heated to a set temperature (for example, 800 ° C. or higher), whereby the tar content is pyrolyzed to lower the molecular weight. Can be made. In this way, by thermally decomposing the tar component, condensation of the tar component can be suppressed, and the influence on the downstream device can be reduced. Here, when the generated gas is heated in the reforming furnace, for example, fuel may be supplied from outside and burned, but a part of the generated gas may be burned. In addition, when water vapor | steam is contained in product gas, a water gas reaction is performed in a reforming furnace and a tar content can be removed efficiently. A component obtained by thermal decomposition or water gasification of the tar content can be used as a fuel gas.

  In this case, the reforming furnace preferably includes a baffle plate that blocks the flow of the product gas in the flow path through which the product gas flows. Thereby, the short path | pass for tar can be suppressed effectively. Moreover, by providing a baffle plate, the radiation effect in the furnace can be enhanced, heat loss can be reduced, and the decomposition efficiency of tar can be improved.

  According to the present invention, it is possible to reduce the influence of the tar component on the downstream side.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a waste gasification system including a waste gasification apparatus to which the present invention is applied. Examples of the combustible waste to be treated in this embodiment include general waste such as home and office, industrial waste, etc., and waste having a relatively large calorific value such as wood waste and waste plastic is suitably treated. .

  As shown in FIG. 1, the waste gasification system of this embodiment includes a gasification furnace 1, a reforming furnace 3, a gas cooling tower 5, a condensation tower 7, an adsorption tower 9, and a gas holder 11. The gasification furnace 1 is provided with an inlet 4 for introducing waste at the top of a cylindrical vertical container 2, and one end of a screw feeder 13 for conveying waste is connected to the inlet 4. . A hopper 15 for storing waste is connected to the other end of the screw feeder 13. Moreover, although not shown in figure, the supply means which supplies an incombustible pellet with a waste into the furnace is connected to the insertion port 4.

  A gas discharge port for discharging generated gas (pyrolysis gas) is provided above the container 2, and a gasifying agent supply port for supplying an oxidizing gas (for example, air) for combustion and water vapor is provided at the bottom. Is provided. The gasifying agent supply port is formed, for example, at the tip of the rotating shaft of the rotary extractor 17 provided at the bottom of the gasification furnace 1. The rotary shaft of the rotary extractor 17 is connected to a motor 19, and when the rotary shaft rotates, the rotary blades cut out waste combustion residues, non-combustible pellets and the like in the radial direction and discharge them from the bottom outlet. ing.

  A gas discharge port of the gasification furnace 1 is connected to a gas supply port of the reforming furnace 3 through an exhaust gas flow channel 21. A line heater 23 is provided along the gas flow path in the exhaust gas flow path 21 to heat the gas line so as not to condense water vapor in the product gas discharged from the gasification furnace 1. The gas supply port of the reforming furnace 3 is provided at the top of the vertical container, and fuel gas (for example, propane gas) and oxygen are supplied in the vicinity of the gas supply port. A gas discharge port for discharging the gas that has passed through the furnace is provided at the bottom of the reforming furnace 3.

  A gas discharge port of the reforming furnace 3 is connected to a gas supply port at the top of the gas cooling tower 5 through an exhaust gas flow path 25. In the gas cooling tower 5, the cooling water sent by the gas cooling pump 27 is ejected from a spray nozzle installed in the upper part of the tower, and is dispersed in the generated gas flowing in the furnace. The water collected at the bottom of the tower is sent to the water tank 29 for drainage treatment. For example, the water at the bottom may be circulated for use.

  A gas discharge port is provided at the bottom of the gas cooling tower 5, and this gas discharge port is connected to a gas supply port at the bottom of the condensing tower 7 via an exhaust gas flow path 31. The condensing tower 7 is provided with a packed bed 31 in the gas flow path in the tower. The packed bed 31 is supplied with, for example, caustic soda by an alkaline liquid supply pump 33.

  A gas discharge port is provided at the top of the condensing tower 7, and this gas discharge port is connected to the gas supply port of the adsorption tower 9 through the exhaust gas flow path 35. The adsorption tower 9 is provided with a packed bed 36 containing a desulfurization catalyst or the like in a gas flow path in the tower. The gas discharged from the adsorption tower 9 is connected to the gas holder 11 via the valve 37 and the compressor 39.

  Next, the operation of this embodiment will be described. First, the crushed waste is introduced into the gasifier 1 from the inlet 4. Waste introduced into the gasification furnace 1 is filled into the furnace from the bottom to form a packed bed. The amount of waste input is adjusted so that a space is formed at the top of the gasification furnace 1 at least.

  In this manner, the oxidizing agent is supplied from the gasifying agent supply port to the gasification furnace 1 filled with waste, and high-temperature air (for example, 400 ° C. or more) is blown from an ignition hot air generator (not shown). To ignite. Then, the supply amount of the oxidant gas is adjusted, and a combustion zone is formed mainly by partially burning only the waste at the bottom of the furnace. The upper layer waste is pyrolyzed by the combustion heat in the combustion zone, and the generated pyrolysis gas rises in the furnace through the gap between the filled waste and is discharged from the discharge port.

When the partial combustion and thermal decomposition of the waste become stable, a stable combustion zone is formed near the bottom of the furnace, a thermal decomposition zone is formed above it, and a waste drying zone is formed above it. The For example, when the waste reaches about 300 ° C. or more, it is thermally decomposed. Therefore, the region of the packed bed of waste exceeding this temperature region becomes a thermal decomposition zone. In the pyrolysis zone, the waste is pyrolyzed to produce combustible pyrolysis gas and carbon (char). The char generated here flows down to the combustion zone and burns, and the temperature of the combustion zone becomes about 1000 ° C. or higher. In addition, a part of the char generated in the thermal decomposition zone reacts with water vapor supplied from the gasifying agent supply port to generate CO and H ₂ .

  The generated gas thus generated passes through the drying zone and dries the waste in the process of flowing through the gap between the wastes in the upper layer. The generated gas is reduced in temperature (for example, about 200 ° C.) by drying the waste, and is discharged from the discharge port through a space formed at the top of the gasification furnace 1. In addition, even if fly ash generated in the combustion zone is accompanied by the product gas, the waste layer filled in the dry zone collects as a filter, so the amount of fly ash flowing out from the outlet is reduced. Can be reduced.

  On the other hand, the waste dried in the drying zone gradually moves to the pyrolysis zone and undergoes pyrolysis treatment, and then moves to the combustion zone where it is pyrolyzed and burned to become ash. These flow down the cooling zone formed in the lower layer of the combustion zone, and are cut out to the discharge port by the rotation of the rotary extractor 17 and discharged outside the furnace. In addition, the combustion residue, incombustible pellets etc. which were discharged | emitted out of the furnace are separated.

  By the way, the generated gas generated from the gasification furnace 1 usually contains hydrogen, carbon monoxide, carbon dioxide gas, water vapor, hydrocarbons and the like. However, for example, if the carbon compound in the waste is not sufficiently thermally decomposed, a tar content may be mixed in the product gas.

  Therefore, in the present embodiment, first, the generated gas discharged from the gasification furnace 1 is introduced into the reforming furnace 3. Fuel gas and air or oxygen are supplied to the reforming furnace 3 together with the product gas, and the product gas supplied into the furnace mainly by combustion of the fuel gas is heated, and the tar content in the gas is thermally decomposed to lower the molecular weight. The cracked gas is produced. Here, since the in-furnace temperature of the reforming furnace 3 is heated to, for example, 800 to 1000 ° C., when the generated gas contains water vapor, a water gas reaction is performed in the furnace, and the tar content is efficiently obtained. Can be removed. In the present embodiment, the inside of the furnace is heated by burning the fuel gas. Alternatively, the product gas may be partially burned and heated.

  After the tar gas is removed from the reforming furnace 3, the product gas is first cooled in the gas cooling tower 5 to a predetermined temperature (for example, about 150 ° C.) by contacting with a mist of cooling water. The product gas cooled in the gas cooling tower 5 is removed by contacting hydrogen chloride or the like in the gas with the alkali liquid in the process of being sent to the condensation tower 7 and passing through the packed bed 31. The product gas that has passed through the condensation tower 7 is cooled to 50 ° C., for example. Subsequently, this generated gas is sent to the adsorption tower 9 and comes into contact with the catalyst layer 36 to mainly absorb and remove hydrogen sulfide. The product gas from which impurities are removed in this way is stored in the gas holder 11 via the compressor 37.

  According to the present embodiment, since the product gas discharged from the gasification furnace 1 is guided to the reforming furnace 3 and heated to a set temperature (for example, 800 ° C. or higher), the tar content contained in the product gas is reduced. Can be pyrolyzed to lower the molecular weight. In this way, by thermal decomposition of the tar content, even if the product gas is cooled on the downstream side, condensation of the tar content can be suppressed, and for example, contamination of cooling water, adhesion to equipment, etc. are suppressed. can do. Moreover, when water vapor is contained in the product gas, a water gas reaction is performed in the reforming furnace 3, so that the tar content can be efficiently removed. And since the component obtained by carrying out thermal decomposition or water gasification of a tar part can be utilized as fuel gas, the recovery efficiency of energy can be improved.

  Next, the configuration of the reforming furnace 3 will be described in detail. FIG. 2 shows an example of the reforming furnace 3 of the waste gasifier to which the present invention is applied, in which (a) shows an upper cross-sectional view and (b) shows a cross-sectional view.

  As shown in the figure, the reforming furnace 3 has a gas supply port 43 formed on one end face of a cylindrical container 41. Although not shown, a supply port for supplying oxygen and fuel gas is provided around the gas supply port 43. An auxiliary burner 45 is provided in the vicinity of the gas supply port 43. A gas discharge port 47 is formed on the side surface on the other end side of the container 41. In the present embodiment, the gas discharge port 47 is arranged in an L shape with respect to the gas supply port 43, but is not limited thereto, and may be formed on an end surface.

  A gas flow path through which the generated gas flows is formed inside the container 41, and a baffle plate 48 that blocks the flow of the generated gas is formed in the gas flow path from the entire circumferential direction of the inner wall toward the cross-sectional center of the gas flow path. Projecting. For this reason, since the flow direction of the produced gas flowing in the container 41 is disturbed by the baffle plate 48, for example, a short path corresponding to tar in the produced gas can be suppressed. Moreover, since the radiation effect can be increased by forming the baffle plate 48, heat loss can be reduced and the decomposition efficiency of tar can be improved. As described above, by efficiently thermally decomposing the tar content, it is possible to further reduce the influence on the equipment on the downstream side of the reforming furnace 3. By providing the baffle plate 48, the flow rate of the product gas flowing in the furnace is reduced (for example, 20 m / sec), and the time for passing through the furnace is apparently increased (for example, about 2 seconds).

  Next, the configuration of another reforming furnace 3 different from the reforming furnace 3 of FIG. 2 will be described. 3 and 4 show an example of a reforming furnace 3 of a waste gasifier to which the present invention is applied, both of which show (a) an upper sectional view and (b) a transverse sectional view. Yes. Note that the same components as those in FIG.

  As shown in FIG. 3, the reforming furnace 3 has a pair of block-like baffle plates 49 that protrude from the inner wall toward the center of the cross section of the gas flow path, and are arranged to face each other with a set interval. Further, as shown in FIG. 4, the other reforming furnace 3 has a gas supply port 43 and a gas discharge port 53 disposed on both end surfaces of the container 41, and a baffle plate 51 at a substantially central position in the cross section of the gas flow path. It is attached. For example, the baffle plate 51 has an area larger than the area of the gas discharge port 53 and smaller than the cross-sectional area of the gas flow path. The baffle plate 51 is connected and supported to the inner wall surface of the furnace by support means (not shown).

  According to this, similarly to the reforming furnace 3 of FIG. 2, the flow direction of the produced gas flowing in the furnace is disturbed by the baffle plates 49 and 51, and therefore, for example, a short path for tar in the produced gas is provided. Can be suppressed. Moreover, since a radiation effect can be enlarged, a heat loss is reduced and the decomposition | disassembly efficiency of a tar part can be improved.

  In addition, in this embodiment, although the structure of FIGS. 2-4 was shown about the reforming furnace, it is not limited to these structures.

It is a figure which shows the structure of the waste gasification system provided with the waste gasification apparatus to which this invention is applied. An example of the reforming furnace 3 of the waste gasifier to which the present invention is applied is shown, (a) is an upper sectional view, and (b) is a transverse sectional view. An example of the reforming furnace 3 of the waste gasifier to which the present invention is applied is shown, (a) is an upper sectional view, and (b) is a transverse sectional view. An example of the reforming furnace 3 of the waste gasifier to which the present invention is applied is shown, (a) is an upper sectional view, and (b) is a transverse sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification furnace 3 Reforming furnace 5 Gas cooling tower 7 Condensing tower 9 Adsorption tower 11 Gas holder 13 Screw feeder 17 Rotary extractor

Claims (5)

Waste comprising a waste gasifier for supplying an oxidizing agent from below the packed bed of waste supplied into the container to form a combustion zone by partial combustion and discharging the generated gas from above the container In the gasifier,
A waste gasification apparatus comprising a reforming furnace for heating the product gas discharged from the waste gasification furnace to gasify tar. The waste gasifier according to claim 1, wherein the reforming furnace includes a baffle plate that blocks the flow of the product gas in a flow path through which the product gas flows. The waste gasifier according to claim 2, wherein the baffle plate is formed so as to protrude from an inner wall of the flow path toward a cross-sectional center of the flow path. The waste gasifier according to claim 3, wherein the baffle plate is formed on the entire circumferential direction of the inner wall. The waste gasifier according to claim 2, wherein the baffle plate is a plate-like member having an area smaller than a cross-sectional area of the flow path.

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