JP2006052896A - Pyrolytic gasification melting system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction in heat transfer performance of a waste heat boiler and corrosion of a heat transfer surface, without increasing equipment cost and running cost, in a pyrolytic gasification melting system of garbage. <P>SOLUTION: This pyrolytic gasification melting system comprises a gasification furnace 3, a melting furnace 6, the waste heat boiler 8, a bag filter 10 for collecting a solid particle in exhaust gas exhausted from the waste heat boiler 8, a means for supplying a desalting agent to the exhaust gas flowing in the bag filter 10, and a means for backwashing the bag filter 10. A filtering speed of the bag filter 10 is set smaller than a particle tail end speed of the particle flowing out as a solid from the melting furnace 6, and is set larger than a particle tail end speed of a particle flowing out in a vaporized state from the melting furnace 6 and flowing in the bug filter 10 as a solid and a particle tail end speed of a particle including a desalting agent component. When the backwash is not performed, the collected particle is supplied to the melting furnace 6, and when the backwash is performed, the particle exhausted from the bag filter 10 is supplied to the melting furnace 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pyrolysis gasification and melting system that thermally decomposes general waste, industrial waste, and the like and collects ash as slag, and an operation method thereof.

  As shown in FIG. 4, the pyrolysis gasification and melting system for general waste and industrial waste supplies fuel and waste to the fluidized bed gasification furnace 3 as shown in FIG. Pyrolysis gasification is performed, and the generated pyrolysis gas and char mainly composed of unburned carbon and ash are combusted in the melting furnace 6 to obtain a high temperature field and slag the ash in the char. In this process, the volume of waste is reduced, and dioxins are completely decomposed and detoxified at high temperatures. The exhaust gas from the melting furnace 6 is completely burned in the secondary combustion chamber 7. The exhaust gas that has exited the secondary combustion chamber 7 is recovered by the waste heat boiler 8 and then dedusted and desalted in the dust collectors 14 and 15 and released into the atmosphere in a detoxified state.

  Moreover, in the pyrolysis gasification melting system for waste, industrial waste, etc. as described above, the molten fly ash collected by the dust collector is circulated in order to reduce the amount of waste dust f to be disposed of in landfills. The fly ash e is recycled to the melting furnace and a part is recovered as slag.

  In addition to collecting dust, the dust collector also aims to remove hydrogen chloride in the exhaust gas, and a desalting agent such as slaked lime is sprayed on the upstream side of the dust collector. For this reason, a large amount of calcium is contained in the collected molten fly ash, and the basicity becomes higher than that of pure molten fly ash. There is a correlation as shown in FIG. 5 between the basicity and the melting point. In the case of molten fly ash having a basicity exceeding 1, the melting point increases as the basicity increases. When the melting point of the molten fly ash recirculated to the melting furnace is high, there are problems such as solidification in the melting furnace and difficulty in stable operation of the melting furnace. For this reason, as shown in FIG. 4 and Patent Document 1, only two circulating fly ash e collected by the former dust collector are provided by providing two dust collectors and supplying slaked lime only to the latter dust collector. Is used to recirculate to the melting furnace. In general, a bag filter, which is a filtration type dust collector, is often used as a dust collector. In this case, it is necessary to supply diatomaceous earth h or the like to the preceding bag filter in order to prevent clogging of the bag filter. There is.

However, in such a system, two or more dust collectors are required, the equipment cost increases, and the running cost increases because diatomaceous earth is more expensive than slaked lime. In addition, high-boiling compounds that can be recovered as slag such as SiO ₂ and Al ₂ O ₃ and low-boiling compounds that cannot be recovered as slag such as Na ₂ O, K ₂ O and chloride are mixed in the molten fly ash. However, since the latter amount is large, even if the recovered molten fly ash is recycled to the melting furnace, the amount recovered as slag is limited. In addition, compounds such as Na ₂ O, K ₂ O and chloride adhere to a waste heat boiler which is a downstream device of the melting furnace, and have a problem that the heat transfer performance is deteriorated and the heat transfer surface is corroded. .

In Patent Document 2, a cyclone separator is disposed in a high temperature atmosphere in which low boiling point compounds such as Na ₂ O, K ₂ O and chloride do not precipitate in the gas phase, and only ash mainly composed of SiO ₂ or Al ₂ O ₃ is used. A technique for separating and recovering and supplying to a melting furnace is disclosed. However, in this technique, in order to maintain the structure of the cyclone separator, cooling from the outside is necessary, and the inner wall temperature of the cyclone separator becomes extremely lower than the gas temperature. For this reason, it is feared that low boiling point compounds such as Na ₂ O, K ₂ O and chloride are deposited in the vicinity of the wall, so that a large amount adheres to the wall and the cyclone separator is blocked.

  In addition, a technique has been devised in which a cyclone and a filtration dust collector are arranged in series as a dust collector, and only the molten fly ash having a large particle diameter is collected and re-supplied to the melting furnace in the cyclone. Even with this method, it is necessary to install an extra cyclone in addition to the filtration type dust collector, so that an increase in equipment cost is inevitable. Further, there is a concern about cyclone corrosion due to high concentration of hydrogen chloride contained in the exhaust gas. Although it is conceivable to protect the inner wall of the cyclone with a refractory material, a small particle diameter of molten fly ash that has not been collected due to increased frictional resistance and has passed through the cyclone will be collected. The original action and effect of collecting only the molten fly ash cannot be obtained.

JP 2001-276774 A (pages 2 to 3, FIG. 1) JP 2001-280633 A (pages 3 to 4, FIG. 1)

  SUMMARY OF THE INVENTION An object of the present invention is to prevent degradation of heat transfer performance of a waste heat boiler and corrosion of a heat transfer surface without increasing equipment costs and running costs in a pyrolysis gasification and melting system for waste with a waste heat boiler. There is.

  The present invention includes a gasification furnace for pyrolyzing and gasifying one or both of waste and industrial waste to discharge pyrolysis gas and char, a melting furnace for burning the exhausted pyrolysis gas and char, Waste heat boiler that recovers the heat of the exhaust gas discharged from the melting furnace, a filtration dust collector that collects solid particles in the exhaust gas discharged from the waste heat boiler, and an inflow into the filtration dust collector A desalting agent supply means for supplying a desalting agent to the exhaust gas to be discharged, a backwashing means for backwashing the filter cloth of the filtration dust collector, and a supply destination of the solid particles collected by the filtration dust collector A switching device for switching between the melting furnace and the other, and a control device for controlling the operation of the backwashing means and the switching device, and the filtration speed of the filtration dust collector is solid from the melting furnace. Smaller than the particle end velocity of the particles flowing out at It is set to be larger than the particle terminal velocity of the particles flowing out in a vaporized state and flowing into the filtration type dust collector as a solid, and the particle terminal velocity of the particles containing the desalting agent component. The particles collected by the filtration dust collector are supplied to the melting furnace from the end to the start of the next back washing, and the particles discharged from the filtration dust collector are not supplied to the melting furnace during the back washing. The above-mentioned problems are solved by a pyrolysis gasification melting system that controls the switching device.

According to the above configuration, low boiling point compounds such as Na ₂ O, K ₂ O and chloride are collected by adhering to the filter cloth of the filtration dust collector, and high boiling points such as SiO ₂ and Al ₂ O _3. It is possible to collect the compound by dropping it before it reaches the filter cloth, and the particles adhering to the filter cloth of the filter type dust collector are desorbed during the backwashing of the filter type dust collector. During this period, the desorbed particles are not circulated to the melting furnace, but before the next backwashing is started after the backwashing is completed, before the filter cloth is reached by the filter type dust collector. The particles collected by dropping, that is, particles of high boiling point compounds such as SiO ₂ and Al ₂ O ₃ are recirculated to the melting furnace, so that Na ₂ O, K ₂ O is applied to the heat transfer surface of the waste heat boiler. In addition, adhesion of chlorides is avoided, and deterioration of heat transfer performance and corrosion of the heat transfer surface are prevented.

  The speed of the exhaust gas in the exhaust gas duct supplying the exhaust gas to the filtration dust collector is such that the particles flowing out from the melting furnace in the exhaust gas duct fall and accumulate in order to avoid falling and depositing particles. It is desirable to set it larger than the particle terminal velocity of the particles flowing out at.

  Further, according to the knowledge of the inventors, it is desirable that the filtration rate of the filtration type dust collector is set in the range of 0.5 to 0.8 m / min.

  According to the present invention, in the pyrolysis gasification and melting system for waste with a waste heat boiler, the heat transfer performance of the waste heat boiler is prevented from being deteriorated and the heat transfer surface is prevented from corroding without increasing the equipment cost and running cost. It became possible.

  An embodiment when the present invention is applied to a pyrolysis gasification melting system for general waste will be described with reference to FIG. The illustrated pyrolysis gasification melting system includes a fluidized bed gasification furnace 3, a swirling melting furnace 6 connected to the fluidized bed gasification furnace 3 through a pyrolysis gas flow path 5, and a melting furnace 6. A secondary combustion chamber 7 provided for the complete combustion of the exhaust gas in the subsequent stage, a waste heat boiler 8 that is arranged after the secondary combustion chamber 7 for the purpose of recovering heat from the exhaust gas, and exhaust gas of the waste heat boiler 8 An exhaust gas temperature reducing device 9 connected to the outlet side by an exhaust gas duct, a bag filter 10 which is a filtration type dust collector connected to the exhaust gas outlet side of the exhaust gas temperature reducing device 9 by an exhaust gas duct 18, and the bag filter 10 A chimney 11 connected by a flue to the exhaust gas exhaust side of the gas generator, a switching device 13 connected to the dust output side of the bag filter 10, and one melting side of the switching device 13 and the melting furnace 6 are connected. Connected to the circulation fly ash pipe 16 and the other exit side of the switching device 13 A waste dust extraction line 17, a control unit 12 for controlling the switching device 13 is configured to include a.

  A fluidized bed gasification furnace (hereinafter referred to as a gasification furnace) 3 is provided with a supply hopper 1 for supplying waste and a dust supply device 2. The exhaust gas temperature reduction device 9 is provided to reduce the exhaust gas temperature in order to suppress the resynthesis of dioxins. The exhaust gas duct 18 is provided with a desalting agent supply means for supplying slaked lime g as a desalting agent to the exhaust gas flowing into the bag filter 10. In addition, backwashing means (not shown) for peeling and removing solid particles adhering to the filter cloth of the bag filter 10 is provided.

  In the system configured as described above, the dust is supplied from the supply hopper 1 through the dust supply device 2 to the gasification furnace 3, and together with the fluidized medium by the fluidized air a supplied from the diffuser pipe 4 installed at the bottom of the gasification furnace 3. Fluidize. In this process, the waste is partially combusted and pyrolyzed to generate char mainly composed of pyrolysis gas, unburned carbon and ash.

  The generated pyrolysis gas and char are sent to the melting furnace 6 and react with the separately supplied combustion air b to burn. The inside of the melting furnace 6 is maintained at a temperature higher than the melting temperature of ash, and the ash in the char melts and is recovered as slag d. Part of the ash in the char is not collected in the melting furnace 6 but flows out of the melting furnace 6 along with the exhaust gas. The exhaust gas leaving the melting furnace 6 is completely combusted in the secondary combustion chamber 7 and recovered by the waste heat boiler 8.

  Of the molten fly ash that was not collected in the melting furnace 6, those having a large particle size and specific gravity were collected before backwashing in the bag filter 10, and supplied to the melting furnace 6 again as circulating fly ash e. It is collected as slag d. The dust f having a small particle size and specific gravity including slaked lime collected after backwashing in the bag filter 10 is disposed of after landfilling.

  The backwashing interval of the bag filter is 1 hour. As shown in FIG. 2, after the backwashing is performed, the switching device 13 is switched to the waste dust side before the bagfilter differential pressure reaches the allowable maximum differential pressure. Only the waste dust is continuously discharged, and then the circulation fly ash e is re-supplied to the melting furnace 6 by switching to the circulation fly ash side. The timing of backwashing and the operation of the switching device 13 are controlled by instructions from the control device 12.

  The present embodiment is an example in which a fluidized bed type gasification furnace and a swirl type melting furnace are combined, but the present invention is not limited to these types, and a gasification furnace other than a fluidized bed type and a swivel type are used. The same operations and effects are also exhibited in combinations of other melting furnaces, combinations of gasification furnaces other than fluidized bed type and swirl type melting furnaces, and combinations of fluidized bed gasification furnaces and melting furnaces other than swirl type.

Ashes that are not collected in the melting furnace are roughly divided into two types. One collides with the inner wall of the melting furnace held at a high temperature, and high boiling point compounds such as SiO ₂ and Al ₂ O ₃ are recovered as slag, and only low boiling point compounds such as Na ₂ O, K ₂ O and chlorides are collected. It flows out of the melting furnace in a vaporized state and precipitates as a solid in a low temperature region after the waste heat boiler 8 and has a very small particle size and specific gravity. The particle end velocity is indicated by B in FIG. 3 and has an extremely small value. The other is a solid that flows out of the melting furnace in a short time without colliding with the melting furnace, and low boiling point compounds such as Na ₂ O, K ₂ O and chloride are diffused, and SiO ₂ and It is composed only of a high boiling point compound such as Al ₂ O ₃ . These are characterized by a large particle diameter and specific gravity, and the particle terminal velocity is one order of magnitude higher than B as shown by A in FIG.

  Further, the particle diameter, specific gravity, and particle terminal speed of slaked lime, which is a desalting agent, are indicated by C in FIG. 3 and have characteristics similar to those of molten fly ash with a small particle diameter indicated by B.

  In consideration of the particle end velocity of each particle, the filtration rate of the bag filter 10 in the present embodiment is larger than the particle end velocity of B and C as shown in FIG. Is set to 0.01 m / s (0.6 m / min). In this embodiment, the filtration speed is set to 0.01 m / s, but it is larger than the particle end speeds of B and C and smaller than the particle end speed of A, preferably 0.5 m. Needless to say, a speed other than 0.6 m / min may be used as long as it is from / min to 0.8 m / min.

Further, the speed of the exhaust gas in the exhaust gas duct 18 is set to be larger than the particle end speed of A, so that particles composed only of high boiling point compounds such as SiO ₂ and Al ₂ O ₃ are not deposited in the exhaust gas duct 18. It is like that.

According to the above configuration, since the filtration speed of the bag filter 10 is set to be larger than the particle end speeds of B and C and smaller than the particle end speed of A, the particle diameter and the ash flowing into the bag filter Particles A having a high specific gravity and composed only of high boiling point compounds such as SiO ₂ and Al ₂ O ₃ fall without reaching the filter cloth and are discharged from the lower hopper of the bag filter. On the other hand, slaked lime C and particles B having a small particle diameter and specific gravity easily reach the filter cloth and adhere to the filter cloth surface. Therefore, until backwashing is performed, the slaked lime C and the particles B having a small particle diameter and specific gravity do not fall and accumulate on the lower hopper.

  On the surface of the filter cloth, slaked lime C and particles B having a small particle diameter and specific gravity are densely packed and adhered to each other by the force of exhaust gas, thereby forming a layer having a certain thickness. By performing backwashing, the layer composed of slaked lime C adhering to the filter cloth and particles B having a small particle diameter and specific gravity peels off from the filter cloth and falls. Since the peeled layer is large, the terminal speed is higher than the filtration speed, and it falls to the lower hopper without reattaching to the filter cloth.

  Bag filters are backwashed in a short time, and the interval between backwashes is as long as about 1 hour. Therefore, until just before backwashing, only particles A having a large particle size and specific gravity are collected in the lower hopper and immediately after backwashing. Only slaked lime C and ash B having a small particle size and specific gravity can be recovered.

Ash A having a large particle size and specific gravity is composed of a high boiling point compound such as SiO ₂ or Al ₂ O ₃ , and if this ash is re-supplied to the melting furnace as circulating fly ash e, almost the entire amount is recovered as slag. it can. Moreover, since the ash B having a small particle size and specific gravity composed of a low boiling point compound such as Na ₂ O, K ₂ O and chloride can be disposed of in landfill after detoxification treatment, it can be disposed of on the heat transfer surface of the waste heat boiler. It can prevent deterioration of heat transfer performance and corrosion of heat transfer surface due to ash adhesion.

According to the present embodiment, only molten fly ash having a high content of high-boiling compounds such as SiO ₂ and Al ₂ O _{3 in the} molten fly ash is selectively recycled to the melting furnace and recovered as slag. , Na ₂ O, K ₂ O and low-boiling compounds such as chlorides can be prevented from flowing into the waste heat boiler, and an expensive stripping agent such as diatomaceous earth can be used without providing additional equipment such as a cyclone separator. Without using it, it becomes possible to reduce the heat transfer performance of the waste heat boiler and to prevent corrosion of the heat transfer surface. Furthermore, the amount of ash collected as slag increases, the amount of waste dust is reduced, and the environmental load is reduced.

It is a block diagram which shows the principal part structure of the pyrolysis gasification melting system which concerns on embodiment of this invention. It is a time chart which shows the operating method of the pyrolysis gasification melting system which concerns on embodiment of this invention. It is a conceptual diagram which shows the principle of this invention. It is a block diagram which shows the example of a prior art. It is a conceptual diagram which shows the relationship between the basicity of ash, and melting | fusing point.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supply hopper 2 Dust supply apparatus 3 Fluidized bed type gasification furnace 4 Aeration pipe 5 Pyrolysis gas flow path 6 Melting furnace 7 Secondary combustion chamber 8 Waste heat boiler 9 Temperature reduction apparatus 10 Bag filter 11 Chimney 12 Control apparatus 13 Switching apparatus 14, 15 Dust collector 16 Circulating fly ash pipe 17 Waste dust extraction pipe 18 Exhaust gas duct

Claims (6)

A gasification furnace for pyrolyzing and / or pyrolyzing one or both of waste and industrial waste to discharge pyrolysis gas and char, a melting furnace for burning the discharged pyrolysis gas and char, and A waste heat boiler that recovers the heat of the exhaust gas discharged, a filtration dust collector that collects solid particles in the exhaust gas discharged from the waste heat boiler, and an exhaust gas that flows into the filtration dust collector. Desalting agent supply means for supplying a salt agent, backwashing means for backwashing the filter cloth of the filtration dust collector, and a supply destination of solid particles collected by the filtration dust collector is the melting furnace. And a switching device that switches to other than that, and a control device that controls the operation of the backwashing means and the switching device,
The filtration speed of the filtration type dust collector is lower than the particle end speed of the particles flowing out of the melting furnace as a solid, the particles flowing out from the melting furnace in a vaporized state, and flowing into the filtration type dust collecting apparatus as a solid Set to be larger than the particle end velocity of the particles and the particle end velocity of the particles containing the desalting agent component,
The controller supplies particles collected by the filtration dust collector to the melting furnace from the end of backwashing to the start of the next backwashing, and particles discharged from the filtration dust collector during backwashing. A pyrolysis gasification melting system for controlling the switching device so as not to supply the gas to the melting furnace.   2. The pyrolysis gasification melting system according to claim 1, wherein a speed of exhaust gas in an exhaust gas duct for supplying exhaust gas to the filtration dust collector is set to be higher than a particle terminal speed of particles flowing out of the melting furnace as solids. Pyrolysis gasification melting system characterized by   The pyrolysis gasification and melting system according to claim 1 or 2, wherein the filtration rate of the filtration type dust collector is 0.5 to 0.8 m / min.   A gasification furnace for pyrolyzing and / or pyrolyzing one or both of waste and industrial waste to discharge pyrolysis gas and char, a melting furnace for burning the discharged pyrolysis gas and char, and A waste heat boiler that recovers the heat of the exhaust gas discharged, a filtration dust collector that collects solid particles in the exhaust gas discharged from the waste heat boiler, and an exhaust gas that flows into the filtration dust collector. Desalting agent supply means for supplying a salt agent, backwashing means for backwashing the filter cloth of the filtration dust collector, and a supply destination of solid particles collected by the filtration dust collector is the melting furnace. And a switching device for switching to the other, a control device for controlling the operation of the backwashing means and the switching device, and a method for operating a pyrolysis gasification and melting system, comprising: Particles flowing out of the melting furnace with solid filtration rate It is smaller than the terminal velocity, set to be larger than the particle terminal velocity of the particles flowing out from the melting furnace in a vaporized state and flowing into the filtration type dust collector as solid and the particle terminal velocity of the particles containing the desalting agent component. During the period from the end of backwashing to the start of the next backwashing, the particles collected by the filtration dust collector are supplied to the melting furnace, and during backwashing, the particles discharged from the filtration dust collector are removed. A method for operating a pyrolysis gasification melting system for controlling the switching device so as not to supply the melting furnace.   5. The operation method of the pyrolysis gasification melting system according to claim 4, wherein the exhaust gas velocity in the exhaust gas duct supplying the exhaust gas to the filtration dust collector is determined from the particle terminal velocity of particles flowing out of the melting furnace as a solid. A method of operating a pyrolysis gasification melting system, characterized in that it is set large. The operation method of the pyrolysis gasification melting system according to claim 4 or 5, wherein the filtration rate of the filtration dust collector is set to 0.5 to 0.8 m / min. How to operate the melting system.

Images