JP4620620B2 - Waste gasifier and operating method thereof - Google Patents

Description

  The present invention relates to a waste gasification apparatus that processes waste using a moving bed gasification furnace and an operation method thereof.

  As a method of treating the waste, for example, the waste is put into a gasification furnace together with incombustible pellets (for example, pumice) to form a packed bed, and an oxidant gas is supplied from the bottom of the furnace to partially burn it. There has been proposed a moving bed gasification furnace that gasifies waste by forming a combustion zone, a pyrolysis zone, and a drying zone in the furnace height direction (see, for example, Patent Document 1). According to this, the waste of the dry zone is dried by the heat of the pyrolysis gas generated in the pyrolysis zone, and fly ash etc. contained in the pyrolysis gas are removed in the process in which the pyrolysis gas rises up the drying zone. Therefore, a relatively clean pyrolysis gas can be obtained.

  By the way, in such a moving bed type gasification furnace, waste is generally put into the furnace in a crushed state to form a packed bed, but the waste contains incombustibles in addition to combustibles. For example, the size of the crushed pieces varies and the filling tends to be uneven. Therefore, drift occurs in the oxidant gas that rises in the packed bed, and the amount of oxidant gas supplied to the combustion zone becomes uneven at the same height position (cross-sectional direction) of the packed bed, and the cross section of the combustion zone There may be a temperature distribution. Even if the oxidant gas is supplied uniformly in the cross section, if the filling of the combustion zone is not uniform, a temperature distribution may be generated due to the difference in calorific value. As described above, when a low temperature region is generated due to the temperature distribution of the combustion zone, a part of the waste is not gasified but is discharged as a combustible material, so that the gasification efficiency is lowered.

  On the other hand, for example, in a shaft furnace type waste melting furnace, when supplying air necessary for burning the waste filled in the furnace from a plurality of locations on the side of the furnace, an air blowing position A technique for suppressing the drift of the air flowing in the furnace by periodically switching in the circumferential direction is disclosed (see Patent Document 2).

Japanese Patent Laid-Open No. 2004-2552 JP-A-8-285248

  However, Patent Document 2 blows in oxygen-enriched air from the side of the furnace and burns the coke of the fuel to generate a waste combustion area, a pyrolysis area, and a drying area in the furnace height direction. A waste melting region is formed below the region.

  On the other hand, the moving bed type gasification furnace supplies oxidant gas necessary for combustion of waste from the bottom of the furnace and cools the combustion residue heat-exchanged with the oxidant gas from the bottom of the furnace. It is discharging. That is, the moving bed type gasification furnace basically supplies oxygen necessary for combustion by supplying from the bottom of the furnace, whereas Patent Document 2 requires a melting region at the bottom of the furnace, so that it is necessary for combustion. Oxygen is supplied from the side of the furnace.

  Based on the difference in the oxygen supply path, the temperature distribution in the combustion zone of the moving bed type gasifier due to the drift of the oxidant gas accompanying the filling state below the combustion zone cannot occur in the configuration of Patent Document 2. Is.

  An object of the present invention is to suppress non-uniform temperature distribution in the combustion zone of a moving bed gasifier and improve gasification efficiency.

In order to solve the above-mentioned problems, the present invention is to introduce waste into a vertical gasification furnace to form a packed bed, and supply an oxidant gas from below the packed bed to generate a combustion zone and heat generated by partial combustion. In the operation method of the waste gasifier formed so that the decomposition zone is sequentially formed in the furnace height direction and the combustion residue is discharged from the bottom of the furnace, the gas is intermittently supplied from the side of the gasification furnace to the combustion zone. The filling of the combustion zone is agitated by changing the position where the gas is blown in and at least the circumferential direction with time .

  That is, the oxygen necessary for combustion in the combustion zone is supplied from below the packed bed, while the gas in the combustion zone is directly blown from the side of the combustion zone to stir the packing in the combustion zone, thereby supplying the oxidant gas from below. Even if a drift occurs, the nonuniform temperature distribution in the horizontal cross section of the combustion zone can be suppressed, so that the gasification efficiency can be improved.

Also, the predetermined pressure of the gas intermittently blown into the combustion zone from the side of the gasification furnace, since by changing at least in the circumferential direction position of blowing thereof gases over time, over the entire combustion zone always Ki de be stirred packed bed Te, it is possible to improve the gasification efficiency.

  Further, the position where gas is blown may be determined randomly as time passes, and control may be performed so that gas is blown from the determined position. According to this, it is possible to improve the gasification efficiency with a simple configuration without requiring a complicated control mechanism.

  Here, the type of gas supplied from the side of the combustion zone may be, for example, the same type of oxidant gas supplied from below the packed bed, but is not limited to this, for example, an inert gas Etc. may be used.

  Further, the waste gasification apparatus of the present invention includes a vertical gasification furnace having a charging port into which waste is introduced at the upper part of the furnace, and an oxidant from below into a packed bed of waste in the gasification furnace. An oxidant supply means for supplying a gas to form a combustion zone by partial combustion, a gas discharge port for discharging the generated gas from above the gasifier, and an exhaust means for extracting combustion residues from the furnace bottom of the gasifier, A plurality of gas supply nozzles for supplying gas to the combustion zone of the packed bed from the side of the gasification furnace, and means for changing the position of supplying the gas among the plurality of gas supply nozzles at least in the circumferential direction over time. The above problem can be solved by the configuration provided.

  ADVANTAGE OF THE INVENTION According to this invention, the gasification efficiency can be improved by suppressing the nonuniform temperature distribution of the combustion zone of a moving bed type gasification furnace.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part of a waste gasifier to which the present invention is applied. Here, although the waste gasification apparatus of this embodiment is used suitably for gasification of a general waste, an industrial waste, biomass, etc., it is not limited to this.

  As shown in the figure, the waste gasifier 1 of the present embodiment (hereinafter simply referred to as a gasification furnace) is, for example, a state in which waste is appropriately dried on the top of a cylindrical vertical container 3. And a hopper 6 for storing non-combustible pellets (for example, spherical calcined pumice, φ20 to 25 mm) used by mixing with waste in the furnace. Double dampers 8 and 10 are provided at the inlets of the hopper 5 and the hopper 6, respectively. For example, the waste is conveyed by the screw conveyor 7 and supplied into the container 3 from the input port 9, while the non-combustible pellet is supplied from the input port 9 into the container 3 by the rotary feeder 12.

  The gasification furnace 1 has a gas outlet 11 for discharging a generated gas (pyrolysis gas) on the top side wall, and a gasifying agent for supplying combustion oxidant gas (air or oxygen, etc.) and water vapor to the bottom. A supply port 13 is provided. The gasifying agent supply port 13 is formed at the tip of the rotary shaft 17 of the rotary extractor 15 that forms the bottom of the gasification furnace 1, for example. The oxidant gas and water vapor that flow through the rotary shaft 17 and are supplied into the furnace from the gasifying agent supply port 13 are supplied radially into the gasification furnace 1. The rotating shaft 17 of the extractor 15 is connected to the motor 21, and the rotating shaft 17 rotates, so that the blades 16 cut out the combustion residue of the waste in the radial direction and discharge it from the discharge port 19. Note that the gasifying agent supply port 13 is not limited to the present embodiment as long as the oxidizing agent and the water vapor are uniformly supplied in the horizontal cross-sectional direction of the gasification furnace 1, for example.

  A steam supply nozzle 18 for supplying steam into the furnace is attached to a set height position of the furnace wall, that is, a lower part of a formation position of a combustion zone 51 described later. For example, a plurality of the water vapor supply nozzles 18 are arranged in the circumferential direction at the same height position on the furnace wall.

  The gasification furnace 1 is provided with a plurality of temperature sensors 23 at predetermined intervals in the furnace height direction of the furnace wall, and one of the temperature sensors 23 is disposed at the same furnace height position as the steam supply nozzle 18. The A plurality of level sensors 25 for detecting the height of the packed bed are attached to the furnace wall above the temperature sensor 23 arranged at the uppermost stage in the furnace height direction. Although not shown, a pressure sensor for detecting the pressure in the upper space 27 of the packed bed is attached to the furnace wall above the level sensor 25.

  Next, the configuration of the nozzle 26 will be described. FIG. 2 is an enlarged schematic diagram showing the vicinity of the nozzle 26 of FIG. 1, and FIG. 3 is a cross-sectional view taken along the line AA of FIG.

  As shown in the figure, on the side wall of the vessel 3 of the gasification furnace 1, four nozzles 26 are arranged at equal intervals in the circumferential direction with the furnace height aligned, and each nozzle 26 is connected via an electromagnetic valve 28. A gas supply line 30 is connected. Here, each nozzle 26 is disposed at a furnace height position that coincides with the formation region of the combustion zone 51. The solenoid valve 28 of each nozzle 26 is electrically connected to, for example, a controller in a central operation chamber (not shown), and the solenoid valve 28 is controlled to open and close based on an electrical signal output from the controller. In this embodiment, an example in which one set of nozzle groups including four nozzles 26 is provided is shown. However, the present invention is not limited to this. For example, a plurality of nozzle groups may be provided in the furnace height direction of the combustion zone 51. However, each nozzle group may be composed of two nozzles 26 or six nozzles 26.

  Next, operation | movement of the gasification furnace 1 comprised in this way is demonstrated. First, at the time of start-up, incombustible pellets are supplied into the gasifier 1 from the inlet 9. This incombustible pellet is for improving the flowability of an oxidant or the like supplied into the furnace. When a predetermined amount of incombustible pellets is supplied, waste that has been appropriately dried and pulverized is introduced into the gasification furnace 1 from the inlet 9. The waste thrown into the furnace is filled into the furnace in a state of being uniformly mixed with the noncombustible pellets to form a packed bed.

  Next, the gasifier 1 filled with waste is ignited by supplying an oxidizing agent from the gasifying agent supply port 13 and blowing hot air (for example, 400 ° C. or more) from the hot air generator 14 for ignition. Let Then, the supply amount of the oxidant is adjusted, the waste is partially burned, and a combustion zone is formed in the packed bed. When the waste is pyrolyzed by the combustion heat of this combustion zone, pyrolysis gas is generated, and this pyrolysis gas rises in the gasification furnace 1 through the gap between the waste and is discharged from the gas outlet 11. Discharged.

In a steady state where partial combustion and thermal decomposition of waste are stable, a stable combustion zone 51 is formed in the vicinity of the bottom of the furnace, a thermal decomposition zone 53 is formed on the upper portion, and a waste drying zone 55 is further provided on the upper side. Is formed. 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 the temperature range becomes the thermal decomposition zone 53. In the pyrolysis zone 53, the waste is pyrolyzed to generate combustible pyrolysis gas and carbon (char). The char generated here flows down to the combustion zone 51 and burns, and the temperature of the combustion zone 51 becomes about 1000 ° C. or higher. Further, a part of the char generated in the thermal decomposition zone 53 reacts with the water vapor supplied to the combustion zone 51 and is converted into CO and H ₂ . The flow rate of the oxidant and water vapor supplied into the furnace is adjusted so that most of the generated char becomes combustion gas and water gas.

  The generated gas obtained by mixing the pyrolysis gas and the water gas generated in this manner passes through the drying zone 55 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 gas outlet 11 through the upper space 27 formed at the top of the gasification furnace 1. Even if fly ash generated in the combustion zone 51 accompanies the product gas, the waste layer filled in the dry zone 55 collects as a filter, and thus the fly ash flowing out from the gas outlet 11 is collected. The amount of ash can be reduced.

  On the other hand, the waste dried in the drying zone 55 gradually moves to the thermal decomposition zone 53 and undergoes thermal decomposition treatment, and then moves to the combustion zone 51 where it is thermally decomposed and burned to become ash (combustion residue). These are cooled by exchanging heat with the oxidant gas supplied from the bottom of the furnace in the process of flowing down the cooling zone 57 formed in the lower layer of the combustion zone 51, and the discharge port 19 together with the incombustible pellets by rotation of the extractor 15. Is cut out and discharged out of the furnace. The non-combustible pellets discharged to the outside of the furnace are returned to the hopper 6 and repeatedly used.

  In this way, the waste in the packed bed moves downward by the extractor 15 extracting the waste from the bottom. On the other hand, the furnace height position at which the combustion zone 51 and the pyrolysis zone 53 are formed is adjusted to a height range set by, for example, the waste extraction speed and the oxidant supply speed.

  When the gasification furnace 1 is started up, the char generated by pyrolyzing the waste is combusted in the combustion zone 51, but a part of the char passes through the combustion zone 51 and remains in the cooling zone without being burned. Since 57 may flow down, water vapor reaction is performed by supplying water vapor in order to stabilize the gasification efficiency of the waste from the start-up.

  By the way, for example, when non-combustible materials are included in the waste, the size of the waste forming the packed layer becomes non-uniform, and accordingly, the filling state such as the gap between the packings becomes non-uniform There is. That is, since the oxidant gas supplied from the gasifying agent supply port 13 at the bottom of the furnace flows up through the gap in the cooling zone 57, the flow of the oxidant gas is biased if the filling state is uneven. As a result, the supply amount of the oxidant gas per unit time reaching the combustion zone 51 becomes uneven in the cross-sectional direction of the gasification furnace 1. Since the combustion temperature in the combustion zone 51 correlates to some extent with the supply amount of the oxidant gas, if the supply amount of the oxidant gas is not uniform, a non-uniform temperature distribution occurs in the cross-sectional direction of the combustion zone 51. There is a fear. Further, even if the oxidant gas is supplied uniformly in the cross-sectional direction of the combustion zone 51, if the filling state of the combustion zone 51 is non-uniform, a difference in heat generation occurs, and similarly non-uniform temperature distribution occurs. There is a fear.

  Therefore, in the present embodiment, gas is directly blown into the combustion zone 51 from the plurality of nozzles 26 arranged in the circumferential direction at the furnace height position of the combustion zone 51 to stir the filler in the combustion zone 51, that is, disturbance. To produce. Here, the gas to be blown is set to a pressure at which at least the filler in a predetermined region of the combustion zone 51 can be stirred, and is appropriately set according to the size of the container 3 and the number of nozzles 26 installed. Here, the type of gas blown into the furnace from the nozzle 26 is not particularly limited, and may be, for example, an oxidant gas or an inert gas. For example, when oxidant gas is blown, oxygen necessary for combustion in the combustion zone 51 is basically supplied from the bottom of the furnace. Therefore, the oxidant gas blown from the nozzle 26 is more oxygen than the oxidant gas supplied from the bottom of the furnace. The concentration can be set low.

  FIG. 4 is a diagram showing the valve opening status of the electromagnetic valve 28 corresponding to the nozzles 26 arranged at positions A to D in FIG. 3 over time. Based on a signal output from a controller (not shown), the solenoid valve 28 of each nozzle 26 is opened and closed for a short time, and gas is intermittently supplied into the furnace. The timing at which the solenoid valve 28 of each nozzle 26 is opened is randomly determined with the passage of time by the controller, and the solenoid valve 28 at the determined nozzle position is controlled to be opened. That is, since the temperature of the horizontal cross section of the combustion zone 51 changes at any time depending on the filling state of the combustion zone 51 and the cooling zone 57, for example, from a control type in which the gas supply position is changed based on the temperature measurement result of the filling material. However, the type of supplying gas at random is preferable because the equipment configuration can be simplified.

  Thus, according to the present embodiment, oxygen necessary for combustion in the combustion zone 51 is supplied from the bottom of the packed bed, while gas is directly blown from the side of the combustion zone 51, that is, the filling in the combustion zone 51, that is, By stirring the carbonized waste, uneven temperature distribution in the horizontal section of the combustion zone 51 can be suppressed even if a drift occurs in the oxidant gas supplied from below. Thereby, since the combustion temperature in the combustion zone 51 can be kept in a predetermined range, gasification efficiency can be improved.

  In this embodiment, an example in which the position of the nozzle 26 that supplies gas to the combustion zone 51 is randomly changed has been described. However, the present invention is not limited to this. For example, the supply of the nozzle 26 with time elapses. You may make it change a position periodically.

  While the present invention has been described with reference to the illustrated embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea of the present invention. It goes without saying that it can be done.

It is a block diagram which shows the principal part of the waste gasification apparatus of this embodiment. It is a schematic block diagram which expands and shows a part of FIG. It is the sectional view on the AA line of FIG. It is a figure which shows the valve opening condition of the solenoid valve corresponding to the nozzle arrange | positioned in position AD in FIG. 3 with time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification furnace 11 Gas discharge port 13 Gasifying agent supply port 19 Discharge port 26 Nozzle 28 Solenoid valve 30 Gas supply line 51 Combustion zone 53 Pyrolysis zone 55 Drying zone 57 Cooling zone

Claims (4)

Waste is put into a vertical gasification furnace to form a packed bed, and an oxidant gas is supplied from below the packed bed to sequentially form a combustion zone and a pyrolysis zone by partial combustion in the furnace height direction. In the operation method of the waste gasifier configured to discharge the combustion residue from the furnace bottom,
Gas is intermittently blown into the combustion zone from the side of the gasification furnace , and the filling position of the combustion zone is agitated by changing the blowing position of the gas at least in the circumferential direction over time. The operation method of the waste gasifier. The operation method of the waste gasifier according to claim 1 , wherein a position where the gas is blown is randomly determined as time passes, and the gas is blown from the determined position. The gas, operating method of the waste gasification apparatus according to claim 1 or 2, characterized in that the oxidizing agent gas.   A vertical gasification furnace having an inlet into which waste is introduced at the top of the furnace, and a combustion zone by partial combustion by supplying an oxidant gas from below into the waste packed bed in the gasification furnace An oxidant supply means for forming; a gas discharge port for discharging the generated gas from above the gasification furnace; a discharge means for extracting combustion residues from the bottom of the gasification furnace; and the combustion zone of the packed bed in the combustion zone Waste gas having a plurality of gas supply nozzles for supplying gas from the side of the gasification furnace, and means for changing a position for supplying the gas among the plurality of gas supply nozzles at least in the circumferential direction over time Device.

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