JP2017145972A - Solid particle recovery device and fluidized bed boiler facility - Google Patents

Abstract

An object of the present invention is to provide a solid particle recovery device capable of efficiently recovering solid particles entrained in exhaust gas using woody biomass as a fuel upstream of a bag filter. Exhaust gas in an exhaust gas duct 40 provided with an economizer 15 into which exhaust gas from a boiler 1 using woody biomass as fuel is introduced, an air preheater 17 and a bag filter 19 are sequentially provided from the upstream side to the downstream side. In the recovery device 100 for recovering solid particles therein, the recovery device 100 includes a hopper 35 below the economizer, a hopper 37 below the air preheater, and a hopper 19a below the bag filter, on the air preheater side. A baffle plate 41 having a flat portion facing the exhaust gas flow direction on the inlet side of the hopper 37 and guiding solid particles in the exhaust gas to the economizer-side hopper 35 and the air preheater-side hopper 37 has an upper end at the hopper It was arranged so that it was above the edge and the lower end was below the hopper edge. With the baffle plate 41, the solid particles can be efficiently recovered by the both hoppers 35 and 37. [Selection] Figure 2

Description

  The present invention relates to a solid particle recovery device for recovering solid particles such as ash in exhaust gas using woody biomass as fuel, and a fluidized bed boiler facility equipped with the solid particle recovery device, and in particular, a economizer provided in an exhaust gas duct. The present invention relates to a solid particle recovery device that recovers solid particles from the lower part of an air preheater and a fluidized bed boiler facility that includes the solid particle recovery device.

  Coal-fired boilers are the mainstream as combustion devices such as boilers installed in thermal power plants and factories. For example, the following Patent Document 1 discloses an exhaust gas treatment in which exhaust gas from a coal-fired boiler is exhausted to the atmosphere after sequentially passing through a economizer, a denitration device, an air preheater (A / H), and a dust collector (bag filter). A method is disclosed, in which exhaust gas is circulated from the economizer outlet to a combustion chamber of a boiler via a gas recirculation dust collector. And since a large amount of ash is generated in the exhaust gas due to the combustion of coal, the hopper at the lower part of the economizer, the hopper at the gas recirculation dust collector, the hopper at the lower part of the denitration device, the hopper at the lower part of the A / H, the lower part of the bag filter Ashes are collected in hoppers and transported to fly ash silos.

  Patent Document 2 below discloses an exhaust gas treatment method in which exhaust gas from a pulverized coal fired boiler is sequentially discharged to the atmosphere after passing through a economizer, a reduction catalyst, and A / H. And the structure which provided the hopper in the flue between the economizer below and the economizer and a catalyst in order to collect the granular ash by fuel derived from combustion is indicated, respectively. Yes.

  In addition, other types of boilers include fluidized bed boilers. A fluidized bed boiler is a boiler that burns with a fluid medium such as sand while mixing the fuel with the medium in the furnace, and is capable of low-temperature combustion at 750-900 ° C., so it has the effect of suppressing the generation of thermal NOx. High and environmental impact is low. In addition, it is excellent in that it can burn a wide range of properties and has high combustion efficiency, and has recently been widely used as a garbage incinerator. Note that thermal NOx refers to NOx that is generated when nitrogen and oxygen contained in combustion air react at a high temperature and become NO.

  Patent Document 3 below discloses an exhaust gas treatment method in which exhaust gas generated from a circulating fluidized bed boiler is exhausted to the atmosphere after passing through a centrifugal separator, bag filter, and SOx reduction device. The ash particles entrained in the flue gas are discharged, the ash particles are separated from the flue gas using a centrifugal separator, and the separated ash particles are returned to the heating furnace and recirculated. In Patent Document 3, since sulfur-containing carbonaceous fuel is used, calcium carbonate is supplied to a heating furnace and a flue to reduce sulfur dioxide in exhaust gas, and ash particles are recycled to the heating furnace. The utilization efficiency of calcium carbonate is increased.

  Furthermore, Patent Document 4 below discloses a configuration in which exhaust gas generated in a combustor is discharged to the atmosphere through a cyclone, a convection heat transfer unit, A / H, and a bag filter in a circulating fluidized bed boiler, The solid particles recovered from the lower part of the convection heat transfer part and the lower part of the A / H are stored in the silo and returned to the combustor. This circulating fluidized bed boiler functions as a garbage incinerator and suppresses the generation of dioxins by introducing a calcium compound into the combustor so that the hydrogen chloride concentration at the combustor outlet is kept below a predetermined value.

JP 60-133214 A Japanese Patent Laying-Open No. 2015-124913 Special table 2008-503707 gazette JP-A-6-66417

  The combustion exhaust gas of a fluidized bed boiler contains combustion ash containing unburned components and fluidized sand that is a fluidized medium of the fluidized bed. It will scatter to the device on the downstream side of the road and cause damage or wear inside the device. In particular, scattering to a economizer or a bag filter on the downstream side of the exhaust gas flow channel from A / H may cause damage to the filter cloth of the bag filter. Although the durability of the bag filter is made of metal, the cost is increased.

  In addition, combustion ash containing unburned matter from the combustion process adhered to the filter cloth of the bag filter, and contacted with air for backwashing of the bag filter, etc., and recombusted, growing in a lump in the hopper below the bag filter. When the clinker is generated, the duct from the hopper to the silo is blocked, causing a discharge failure.

  According to the configuration described in Patent Document 1, a high-temperature coal ash is introduced into an A / H inlet flue, and heat recovery is performed to transport the low-temperature coal ash to a fly ash silo. Prevents thermal damage to the filter. However, if the ash cannot be efficiently collected by the hopper at the lower part of the economizer or the lower part of the A / H, the generation of clinker in the hopper of the bag filter cannot be suppressed.

  According to the configuration described in Patent Document 2, a baffle plate is provided at the upper part of the hopper below the economizer so that the solid particles collected in the hopper do not flow out to the outside. The structure which collects ashes by providing a low-repulsion part above a hopper is disclosed. When coal is used as the fuel, coal ash has a relatively large specific gravity, so that it is easy to collect in the lower part of the flue and is also easily collected in the hopper.

  Due to the problem of global warming caused by carbon dioxide in recent years, a biomass fuel called carbon neutral has been attracting attention. Biomass is an organic matter produced by living organisms through photosynthesis, and carbon dioxide released by burning biomass is carbon dioxide absorbed from the atmosphere by photosynthesis during the growth of the organism. Thus, biomass is a neutral fuel that does not increase atmospheric carbon dioxide during the life cycle of the organism. Among them, woody biomass fuel has a high purchase price under the Special Renewable Energy Measures Law (FIT Law) and is expected to promote its use.

  By the way, the conventional biomass fuel is formed into pellets or crushed into chips, so that the water content is generally kept low and constant. Recently, however, forest thinnings are often brought directly into the boiler, and the high moisture content and the large fluctuations in the high moisture region have triggered the problems described below.

  The fluidized bed boiler is an optimum combustion apparatus for direct combustion of biomass because of its high adaptability to fuel and low environmental load. Biomass power generation based on this fluidized bed boiler is expected to spread in the future.

  In the fluidized bed boiler, as described in Patent Document 3 and Patent Document 4, the combustion ash and fluidized sand accompanying the exhaust gas are recovered in the hopper at the bottom of the bag filter and the lower part of the A / H and returned to the fluidized bed to replenish. The amount of fluid sand to be reduced is reduced. However, wood biomass combustion ash is lighter in specific gravity than coal ash, and thus is not collected by these hoppers and is likely to be scattered to a bag filter on the downstream side. In addition, if the amount of combustion ash containing unburned components that are returned to the fluidized bed is reduced due to difficulty in being collected by the hopper, the amount of unburned components that are finally discharged outside the furnace increases. It is not preferable.

  Woody biomass fuel has a large variation in moisture in the fuel that is received, and when the amount of moisture is large, the amount of exhaust gas increases, the furnace temperature decreases, and the residence time of combustion decreases. Tend to get worse. In addition, the increase in the amount of exhaust gas leads to an increase in superficial velocity, and the amount of fluid sand that becomes a cause of wear increases, so wear of hoppers, ducts, ash transport piping, etc. for collecting ash, unburned components, etc. It becomes a factor causing. Furthermore, when the flammability deteriorates, the unburned matter increases, so that coarse ash does not burn out and adheres to the filter cloth of the bag filter. If a clinker growing in a lump is generated due to cloth damage or reburned ash falling on the hopper below the bag filter, the duct from the hopper to the silo is blocked, causing a discharge failure.

  Therefore, an object of the present invention is to efficiently recover solid particles such as ash and fluidized sand containing unburned components accompanying the exhaust gas using woody biomass as the fuel upstream of the exhaust gas flow path from the bag filter. It is to provide a solid particle recovery device and a fluidized bed boiler facility equipped with the solid particle recovery device.

The object of the present invention can be achieved by adopting the following constitution.
The invention according to claim 1 includes a economizer (15) for exchanging heat between exhaust gas and water discharged from a combustion device using woody biomass as fuel, and an air preheater (15) for exchanging heat between exhaust gas and air. 17) and a solid filter for collecting solid particles in the exhaust gas flowing through the exhaust gas duct (40), which is sequentially provided from the upstream side to the downstream side in the exhaust gas flow direction with a bag filter (19) that collects dust in the exhaust gas. (100), wherein the solid particle recovery device (100) is provided in an exhaust gas duct below the economizer, and is a economizer-side hopper (35) capable of recovering solid particles in the exhaust gas, and an air preheater. An air preheater side hopper (37) provided in a lower exhaust gas duct and capable of recovering solid particles in the exhaust gas, and a hopper (19a) below the bag filter, the exhaust gas flow of the air preheater side hopper (37) Direction upstream A baffle plate (41) having a flat portion facing the exhaust gas flow direction and guiding solid particles in the exhaust gas to the economizer-side hopper (35) and the air preheater-side hopper (37). (41) is a solid particle recovery device arranged such that the upper end is above the hopper edge and the lower end is below the hopper edge.

  According to the second aspect of the present invention, the air preheater side hopper (37) on the downstream side in the exhaust gas flow direction from the baffle plate (41) has a flat portion facing the hopper bottom, and the solid particle hopper in the hopper. 2. The solid particle recovery device according to claim 1, wherein the re-scattering prevention plate (43) that prevents scattering to the outside is arranged so that the upper end of the re-scattering prevention plate (43) is below the hopper edge. 3.

  According to a third aspect of the present invention, the baffle plate (41) is arranged such that the upper end thereof is located above the exhaust gas duct (40) above the air preheater-side hopper (37). 2. The solid particle recovery device according to 2.

  The invention according to claim 4 is the solid particles according to any one of claims 1 to 3, wherein the economizer-side hopper (35) and the air preheater-side hopper (37) are disposed adjacent to each other. It is a recovery device.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the baffle plate (41) has a configuration in which a plurality of elongated plate members (41a, 41b) are arranged in a staggered manner in the exhaust gas flow direction. The solid particle recovery device described in 1. above.

The invention according to claim 6 is a fluidized bed boiler (1) using woody biomass as a fuel, and a economizer (15) for exchanging heat between the exhaust gas discharged from the fluidized bed boiler (1) and water, An exhaust gas duct (40) provided with an air preheater (17) for exchanging heat between exhaust gas and air, and a bag filter (19) for collecting soot and dust in the exhaust gas sequentially from the upstream side to the downstream side in the exhaust gas flow direction; The solid particle recovery device (100) according to any one of claims 1 to 5, and the solid particles in the economizer side hopper (35) and the air preheater side hopper (37) are fluidized bed boilers. This is a fluidized bed boiler facility provided with a circulating section (56) to be sent to (1).
In addition, the solid particle in this specification is meant to include not only dusts such as ash, soot, and unburned matter generated by combustion of fuel, but also fluidized medium (mainly sand) of a fluidized bed boiler.

(Function)
As described above, solid particles such as ash and fluidized sand containing unburned components generated by the combustion of fuel are accompanied by a high-temperature exhaust gas flow and scattered to a bag filter downstream of the exhaust gas flow path. Cause damage. In addition, when woody biomass is used as fuel, when burning high-moisture fuel, the amount of exhaust gas increases and the amount of unburned fuel increases, so that coarse combustion ash does not burn out and adheres to the filter cloth of the bag filter. Therefore, if the clinker grows in a lump due to damage to the filter cloth due to recombustion with air during backwashing of the bag filter, or dropping of reburned ash to the hopper below the bag filter, The duct to the door will be blocked, causing a discharge failure. In addition, since the combustion ash of a fine particle has completed combustion by the residence time in a boiler, it does not re-burn and does not become a target of a problem.

  Since wood biomass has a lower specific gravity than coal, even if a hopper is provided below the economizer or A / H, the combustion ash is carried on the exhaust gas flow and is difficult to accumulate in the hopper. In the configuration described in Patent Document 2, coal ash whose specific gravity is about 10 times or more larger than that of woody biomass is targeted and is easily collected in the hopper, but is not discharged to the outside due to the recoil hitting the hopper. The baffle plate at the top of the hopper prevents outflow.

  On the other hand, in the case of woody biomass, it is difficult to accumulate in the hopper as described above. For example, even if the baffle plate for solid particles described in Patent Document 2 is provided on the hopper above the economizer, it is trapped in the hopper. Since there is almost no effect to be collected in the first place, the effect of preventing the outflow by the baffle plate is not expected, and the combustion ash flowing through the flue passes through and is directly scattered on the bag filter on the downstream side. Moreover, in the structure which provided the low repulsion part on the flue and side wall above a hopper along with an exhaust gas flow as disclosed by FIG. 11 of patent document 2, it is accompanied by the upward exhaust gas flow similarly. Ashes pass through the low repulsion part and flow upward.

  The boiler exhaust gas passes through the superheater, economizer, and air preheater, and then flows into the bag filter. Therefore, it is desirable that coarse combustion ash that adversely affects downstream equipment can be collected as much as possible by the hopper below the economizer and the hopper below the A / H on the upstream side of the exhaust gas flow path from the bag filter. Therefore, the present inventors use these hoppers below the economizer and the hopper below the A / H in order to efficiently collect solid particles such as ash derived from wood biomass fuel having a low specific gravity. The present invention was completed by intensive studies on the position, shape, size, etc. of the baffle plate installed in the vicinity of the hopper.

  First, when considering mainly collecting ash in the hopper below the economizer where the exhaust gas flows first (sometimes called economizer hopper), this is the baffle plate on the outlet side of the economizer hopper. It is possible to provide it. However, since the flow path is narrowed by the economizer hopper and the baffle plate, there is a portion where the flow rate of the exhaust gas increases, so that the potential to cause wear of the baffle plate and the economizer hopper becomes high. When these members are worn, replacement of members and maintenance are required, so that operation efficiency and processing efficiency are deteriorated.

  Since it is sufficient that the coarse combustion ash can be collected upstream of the bag filter, it is sufficient that the total amount of ash that can be collected by both hoppers is increased, instead of collecting either hopper as the main. Therefore, by providing a baffle plate on the entrance side of the hopper below the A / H (sometimes referred to as the A / H hopper), it is thought that coarse ash can be efficiently recovered by both hoppers, We studied earnestly.

  By providing the baffle plate at the hopper inlet side on the A / H side downstream of the economizer hopper so that the flat portion thereof faces the exhaust gas flow direction, coarse combustion ash hitting the baffle plate can be obtained. In addition to being guided by the A / H hopper, the recoil also falls to the upstream economizer hopper. If the upper end of the baffle plate is above the hopper edge, the coarse combustion ash flowing through the exhaust gas duct above the hopper hits the baffle plate and is guided into the hopper. At this time, if the lower end of the baffle plate is above the hopper edge, there is a possibility that coarse combustion ash may pass through the lower portion of the baffle plate. Therefore, the upper end of the baffle plate may be disposed above the hopper edge, and the lower end of the baffle plate may be disposed below the hopper edge. In addition, since the exhaust gas once flows into the economizer hopper, it flows through the part where the duct side and the flow path are separated and widened, so the flow rate increases slightly when passing through the baffle plate, but the flow rate is so much Does not rise. Therefore, wear of the baffle plate, the economizer hopper, the A / H hopper, etc. can be prevented.

  That is, according to the first aspect of the present invention, the baffle plate is on the entrance side of the A / H hopper, the upper end of the baffle plate is above the hopper edge, and the lower end of the baffle plate is below the hopper edge. As a result, the ash hitting the baffle plate can be guided to the A / H hopper and the economizer hopper, and the ash passing through the baffle plate can be prevented. Accordingly, the ash recovery rate is improved.

  In addition, since the specific gravity of wood biomass-derived ash is light, even if it flows into the hopper once, it may fly up and be scattered outside the hopper. Therefore, by installing a re-scattering prevention plate in the A / H hopper on the downstream side of the baffle plate, ash scattered outside the hopper can be suppressed. When the upper end of the re-scattering prevention plate is above the hopper edge, it is considered that the ash in the hopper is carried to the exhaust gas flow flowing through the exhaust gas duct at the upper part of the hopper. Therefore, the ash can be kept in the hopper by arranging the re-scattering prevention plate so that the upper end is below the hopper edge. Therefore, according to the invention of claim 2, in addition to the action of the invention of claim 1 above, even if coarse combustion ash flowing into the A / H hopper rises, it hits the re-scattering prevention plate, Re-scattering to the outside of the hopper can be suppressed.

  Further, if the upper end of the baffle plate is at the upper part of the exhaust gas duct above the hopper, most of the coarse combustion ash flowing through the exhaust gas duct hits the baffle plate. Therefore, according to the invention described in claim 3, in addition to the action of the invention described in claim 1 or claim 2, coarse combustion ash flowing in the upper part of the exhaust gas duct can also be collected with high probability. The recovery rate of the flowing coarse ash can be improved.

  Since the economizer hopper and the A / H hopper are arranged adjacent to each other, the distance between the baffle plate and the economizer hopper is also close. It becomes easy to be guided to the container hopper. Therefore, according to the invention described in claim 4, in addition to the action of the invention described in claims 1 to 3, the recovery rate in the economizer hopper upstream of the A / H hopper is improved.

  In addition, the baffle plate has a configuration in which a plurality of elongated plates are arranged in a staggered manner in the exhaust gas flow direction, so that the coarse combustion ash reliably hits the baffle plate and the exhaust gas flows through the gaps between the plates, thereby causing a pressure loss. Can be prevented. Therefore, according to the fifth aspect of the invention, in addition to the effects of the first to fourth aspects of the invention, it is possible to improve the collection rate of ash and suppress the increase in pressure loss.

  In the fluidized bed boiler, the sand used as the fluidized medium is also scattered with the exhaust gas. According to the invention described in claim 6, the fluidized bed boiler facility is described in any one of claims 1 to 5. By providing this solid particle recovery device, fluid sand that scatters together with coarse combustion ash can be recovered in the A / H hopper and the economizer hopper by the baffle plate and the re-scattering prevention plate. Therefore, the replenishment amount of fluidized sand is reduced by returning the recovered coarse combustion ash and fluidized sand to the fluidized bed boiler.

  According to the first aspect of the present invention, by installing the baffle plate, solid particles such as ash and unburned matter in the exhaust gas can be efficiently recovered by both the A / H hopper and the economizer hopper. Therefore, the recovery rate of solid particles is improved. Moreover, since the rapid increase in the flow velocity is suppressed even when the exhaust gas passes through the baffle plate, the potential for causing wear of the baffle plate and the economizer-side hopper, and further the potential for causing damage to the bag cloth filter cloth can be reduced.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1 above, even the coarse combustion ash derived from the woody biomass fuel that is light in specific gravity and easily scattered, hits the re-scattering prevention plate, Re-scattering from the A / H hopper to the outside can be suppressed.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, the upper end of the baffle plate is located above the exhaust gas duct, so that the coarse particles flowing through the exhaust gas duct are burned. Ashes can be recovered efficiently.

  According to the invention of claim 4, in addition to the effects of the inventions of claims 1 to 3, the economizer side hopper and the A / H side hopper are arranged adjacent to each other, so that the A / H side The recovery rate of solid particles in the economizer-side hopper upstream from the hopper can be improved.

  According to the fifth aspect of the present invention, in addition to the effects of the first to fourth aspects of the present invention, the baffle plate in which a plurality of elongated plate members are arranged in a staggered arrangement is used to suppress an increase in pressure loss while being solid. The collection rate of particles can be improved.

  According to the invention described in claim 6, by providing the solid particle recovery device according to any one of claims 1 to 5 in the fluidized bed boiler facility, the recovery amount of sand scattered together with the ash is improved. The amount of sand replenishment can be reduced. Moreover, if unburned part particle | grains can be collect | recovered, a combustion efficiency can be improved by returning to the combustion part of a boiler.

It is a systematic diagram (schematic diagram) of boiler equipment which is one example of the present invention. It is a partial detail drawing of the ash collection | recovery apparatus of the boiler equipment of FIG. It is an AA arrow directional view of FIG. 4A is a view taken along line BB in FIG. 2 (upstream side plate), and FIG. 4B is a view taken along line CC in FIG. 2 (downstream side plate). It is a partial detail drawing of the ash collection | recovery apparatus which showed another example of the baffle board of FIG. FIG. 6A is a perspective view of an installation example of the case 1, and FIG. 6B is a perspective view of an installation example of the case 2 (Example). 7A is a perspective view of an installation example of the case 3, and FIG. 7B is a perspective view of an installation example of the case 4 (comparative example). FIG. 8A shows an example of a U-shaped cross section, and FIG. 8B shows an example of an L-shaped baffle plate. FIG. 6 is a diagram showing a flow analysis result of case 1. FIG. 6 is a diagram showing a flow analysis result of case 2. FIG. 6 is a diagram showing a flow analysis result of case 3. FIG. 6 is a diagram showing a flow analysis result of case 4. It is the figure which showed the measurement result of the particle size distribution of black ash. It is the figure which showed the collection rate and passage rate of black ash. It is a systematic diagram (schematic diagram) of another example (comparative example) of the boiler installation of FIG.

  Embodiments of the present invention are shown below.

  FIG. 1 shows a system diagram of boiler equipment according to an embodiment of the present invention. FIG. 2 shows a partial detailed view of the boiler ash recovery device (solid particle recovery device) of FIG. The internal side view (partial sectional view) of the hopper part below and A / H is shown. 3 shows an AA arrow view (plan view) in FIG. 2, FIG. 4A shows an BB arrow view (partially omitted) in FIG. FIG. 4B shows a view (partially omitted) taken along line CC in FIG. Further, FIG. 5 shows another example of the baffle plate of FIG.

  When the fluidized bed boiler 1 is started, the fluidized bed 61 is brought into a fluidized state while the inside of the furnace and the fluidized bed 61 are heated to a predetermined temperature or higher by liquid fuel such as kerosene supplied to the burner 5 and the like. Woody biomass fuel is charged, burned in the furnace 7, and after reaching a predetermined load, the burner 5 and the like are extinguished and burned in a woody biomass fired state. Exhaust gas generated by combustion passes through the superheater 11, the evaporative water pipe portion 13, and the economizer 15 from the outlet portion 9, and heat exchange is performed between the exhaust gas and water. Steam is generated by exchanging heat between the water and the exhaust gas, and a turbine (not shown) is rotated by the high-pressure steam, and power is generated by a generator connected to the turbine.

  Further, the heat exchange between the combustion air and the exhaust gas is performed at A / H 17, so that the temperature of the combustion air is raised, and the primary air is supplied from the primary air pipe 65 from the lower part of the furnace 7, and the secondary air pipe 67 is supplied from the furnace 7. Secondary air is supplied into the furnace 7 from the after-air port 69 before the can. The flow rates of the primary air and the secondary air are adjusted by a damper 63 provided in each of the pipes 65 and 67. The exhaust gas whose gas temperature has been reduced to a constant temperature by A / H 17 is discharged from the chimney 21 after the dust is removed by the bag filter 19.

  In the lower part of the furnace 7, a fluidized bed 61 is formed by a fluid medium such as sand. For the purpose of removing foreign substances (sand and clinker which has become larger due to ash adhesion) in the fluidized bed 61, sand is removed from the bottom of the boiler furnace. , Extracted in a discharger 23, screened by a separator 25, then air conveyed to a sand supply silo 29 by a blower 27 and re-introduced into the furnace 7. Sand is also replenished from the sand silo 31.

Next, the ash collection device 100 will be described.
As shown in FIG. 2, an economizer hopper 35 and an A / H hopper 37 are provided below the economizer 15 and below the A / H 17, respectively. Further, an entrance (upstream) of the A / H hopper 37 is provided. The baffle plate 41 is arranged in an upright position so that its upper end is above the hopper edge 37a and its lower end is below the hopper edge 37a.

The exhaust gas flows from the outlet portion 9 in the arrow D direction (downward), passes through the horizontal portion 40a between the economizer hopper 35 and the A / H hopper 37, and flows in the arrow E direction (upward).
Solid particles such as ash and sand flowing in the exhaust gas duct 40 together with the exhaust gas hit the baffle plate 41 when the upper end of the baffle plate 41 is above the hopper edge, and are guided to the A / H hopper 37 and the reaction thereof. Then, it falls to the upstream economizer hopper 35 as well. Further, since the lower end of the baffle plate 41 is below the hopper edge 37a, it is possible to prevent slipping of the coarse combustion ash below the baffle plate 41.

  Accordingly, it is possible to prevent coarse combustion ash and sand flowing through the exhaust gas duct 40 from being scattered on the bag filter 19 on the downstream side, and to eliminate the risk of damage. Therefore, even if the filter cloth of the bag filter 19 is made of cloth. no problem. The same applies to the fly ash silo bag filter 49.

  According to the common sense of those skilled in the art, the baffle plate 41 is usually provided in the hopper on the upstream side in the gas flow direction (right side in the illustrated example). However, the present inventors have found that the problem cannot be solved by the idea, and have decided to provide the hopper downstream (left side in the illustrated example). This point is connected to the feature of the present invention.

  In addition, since the specific gravity of the ash derived from the woody biomass is light, even if it is collected once, it may fly up and be scattered in the exhaust gas duct 40. Therefore, the ash in the hopper 37 is carried to the exhaust gas flowing through the exhaust gas duct 40 by disposing the re-scattering prevention plate 43 in the A / H hopper 37 so that the upper end thereof is below the hopper edge 37a. The scattering to the outside of the hopper 37 can be suppressed while preventing this. That is, even if the ash in the A / H hopper 37 soars, it is collected by hitting the re-scattering prevention plate 43 and making a U-turn. In FIG. 2, the re-scattering prevention plate 43 is installed along the horizontal direction with its end in contact with the hopper inner wall, but is installed in an oblique direction even if the end is not in contact with the hopper inner wall. Any arrangement may be used as long as the ash collision surface faces the hopper bottom side.

  The soot dust contains mainly wood biomass fuel-derived ash and sand, and in the economizer hopper 35 and the A / H hopper 37, coarse ash and sand having a relatively large particle size are collected. . The collected ash and sand are continuously discharged quantitatively by the rotary valve 45 and are carried to the sand bag filter 39 by air conveyance from the blower 27. At this time, if the curved portion of the pipe is a ceramic lining pipe or the flow rate is adjusted to 15 to 20 m / s by opening and closing the valve 53 for adjusting the flow rate of the pipe, the wear of the pipe can be suppressed. Adjustment of the rotary valve 45 and the valve 53 is performed by a control device (not shown), thereby enabling continuous operation.

  Further, the sand bag filter 39 is fed out by a predetermined amount by the rotary valve 45 and is sent to the sand supply silo 29 through the circulation pipe 56. At this time, by partially bypassing the pressure equalizing pipe 55, the flow of coarse ash becomes smooth. According to the present embodiment, the fluid sand that scatters with the ash can be recovered in the A / H hopper 37 and the economizer hopper 35, so that the recovery amount of the fluid sand is improved, and the recovered fluid sand is circulated to the furnace 7. The replenishment amount of the fluid sand supplied to the furnace 7 is also reduced.

  On the other hand, the fine combustion ash having a relatively small particle size passes through the economizer hopper 35 and the A / H hopper 37 and is collected by the bag filter 19 on the downstream side of the A / H 17. The bag filter 19 is fed out by a fixed amount by a rotary valve 45 and sent to a fly ash silo bag filter 49 by a vacuum pump 47. Further, the fly ash silo bag filter 49 is fed out by a fixed amount by the rotary valve 45 and sent to the fly ash silo 51. The bag filter 19 collects fine combustion ash and contains almost no fluid sand. Therefore, the ash stored in the fly ash silo 51 is effectively used after wet processing or dry processing.

  As described above, in addition to the economizer hopper 35, the A / H hopper 37, and the bag filter 19, the ash collection device 100 includes a sand bag filter 39, a sand supply silo 29, a fly ash silo bug filter 49, It is composed of a fly ash silo 51 and the like.

  Further, as shown in FIGS. 2 and 3, since the economizer hopper 35 and the A / H hopper 37 are disposed adjacent to each other, the distance between the baffle plate 41 and the economizer hopper 35 is also reduced. The coarse-grained combustion ash that hits is easily guided to the economizer hopper 35, and the recovery rate of the coarse-grained combustion ash in the economizer hopper 35 is improved. In the present specification, the adjacent arrangement means that each structural body is formed when the hopper edges of the economizer hopper 35 and the A / H hopper 37 are in contact with each other and between the economizer hopper 35 and the A / H hopper 37. This means that there are enough ducts necessary for the connection.

  If the upper end of the baffle plate 41 is above the exhaust gas duct 40, for example, near the ceiling of the horizontal portion 40a, most of the coarse combustion ash flowing through the exhaust gas duct 40 will hit the baffle plate 41. Coarse-burning ash flowing in the upper part of 40 can also be collected with a high probability.

  On the other hand, when the length (height) of the baffle plate 41 is shorter, the pressure loss of the exhaust gas is reduced. For example, as shown in FIG. 5, the length of the baffle plate 41 is set to the inner diameter (height) of the duct 40. ) Is also possible. The flow rate of the exhaust gas is determined by the relationship between the structure and size of the casing, the properties of the biomass fuel, the amount of exhaust gas, and the like. When the flow velocity is high, even particles with a large specific gravity are scattered, but when the flow velocity is low, not only particles with a large specific gravity but also particles with a large shape are easily dropped and collected even when the specific gravity is small.

  When the upper end of the baffle plate 41 is at half the height of the flow path, the upper part of the baffle plate 41 (the upper half of the flow path) has relatively little ash, and there is no obstacle to keep the flow speed high. Be drunk. And the installation part (lower half of a flow path) of the baffle board 41 has comparatively much ash, and it hits the baffle board 41 and the flow velocity falls and is collected. Accordingly, when the flow velocity is high and it is necessary to suppress the increase in pressure loss due to the installation of the baffle plate 41 as much as possible, the upper end of the baffle plate 41 is set to a half height position of the flow path as shown in FIG. As a result, the pressure loss can be kept low. In this case, the exhaust gas flow velocity above the baffle plate 41 is increased, but the specific gravity is small and fine ash is selectively accompanied. On the other hand, the exhaust gas flow velocity on the lower side where the baffle plate 41 is installed is relatively slower than that on the upper side. Particles with large specific gravity such as fluid sand and particles with large shape such as coarse combustion ash are likely to flow with the exhaust gas, but collide with the baffle plate 41. In this case, the flow rate is lowered and collected, so that a predetermined collection rate can be secured.

  Further, as shown in FIG. 4, the baffle plate 41 may have a configuration in which a plurality of elongated plates 41 a and 41 b are arranged in a staggered manner. FIG. 4 (A) shows the arrangement of the upstream side plate 41a, and FIG. 4 (B) shows the arrangement of the downstream side plate 41b. In the illustrated example, the upstream side plate 41a and the downstream side plate 41b are installed along the exhaust gas flow direction, and are staggered so as not to overlap when viewed from the exhaust gas flow direction. With this arrangement, the solid particles accompanying the exhaust gas flow reliably hit the plates 41a and 41b of the baffle plate 41, and the exhaust gas has gaps such as between the upstream side plates 41a, between the downstream side plates 41b, between the upstream side plate 41a and the downstream side plate 41b. By flowing, an increase in pressure loss of exhaust gas can be prevented.

  In order to confirm the effect of this example, when only the baffle plate 41 is installed as an example (case 1), when both the baffle plate 41 and the re-scattering prevention plate 43 are installed (case 2), and as a comparative example, Flow occurs when the baffle plate 41 is installed on the outlet side (downstream side) of the economizer hopper 35 (case 3), and when the baffle plate 41 is installed in the duct 40 downstream of the A / H hopper 37 (case 4). Analysis was performed to calculate the solid particle collection rate, the maximum exhaust gas flow velocity, and the exhaust gas pressure loss.

  Regarding the collection rate, in this flow analysis, the number of all particles entrained in the exhaust gas was repaired in each hopper, and the collection rate was calculated. In addition, the total balance was confirmed by counting the number of particles remaining in the duct and the number of particles entrained by the exhaust gas.

  Moreover, the pressure loss was calculated | required as follows. The sum of the average value of the static pressure and the average value of the dynamic pressure as the pressure value is obtained as the average value of the total pressure. ) And the difference between the total pressure average value in the predetermined cross section. The pressure loss (draft loss) described in Table 1 below is calculated as the difference between the total pressure average value of the inflow surface and the total pressure average value of the outflow surface (parallel cross section of the duct outlet) in each case.

  FIGS. 6A and 6B are perspective views of installation examples of the case 1 and the case 2 as examples, and FIGS. 7A and 7B show the case 3 and the case 4 as comparative examples. The perspective view of the example of installation is shown. In these drawings, the baffle plate 41 is indicated by a solid line so that the shape and position of the baffle plate 41 can be easily understood, and a part of the economizer hopper 35, the A / H hopper 37, and the exhaust gas duct 40 are indicated by broken lines. . The flow analysis conditions were as follows.

Exhaust gas amount: 41,000 m ³ N / h, economizer hopper inlet gas temperature: 228 ° C., dust concentration: 0.6 g / m ³ N, dust particle size: 0.6 mm, dust density: 0.1 t / m ³
In FIG. 8, the example of the cross section of the baffle board 41 is shown. FIG. 8A shows an example of a U-shaped cross section of the baffle plate 41 shown in FIGS. 2 and 5, and FIG. 8B shows an example of an L-shaped cross section.

  As the baffle plate 41, a plate having a U-shaped cross section (200 mm × 1500 mm) shown in FIG. 8A was installed in a staggered arrangement using 10 pieces in total in the exhaust gas flow direction. The baffle plate 41 was installed in the vertical direction in the cases 1 to 3 and in the horizontal direction in the case 4 so that the flat surface portion (the U-shaped opening side) faces the exhaust gas flow direction.

  Each of the hoppers 35 and 37 is a quadrangular pyramid, the economizer hopper 35 has a bottom (2000 mm × 1680 mm) and a height of 1200 mm, and the A / H hopper 37 has a bottom (2000 mm × 2010 mm) and a height of 1200 mm. The width of 40 is 2000 mm, the height is 1500 mm, and the distance between the hoppers 35 and 37 (the distance between the edges) is 590 mm.

  9 shows the flow analysis result of case 1, FIG. 10 shows the flow analysis result of case 2, FIG. 11 shows the flow analysis result of case 3, and FIG. A flow analysis result is shown (perspective view). (B) of each figure shows the enlarged view of the X part (X1-X4) of (A) of each figure, (D) of each figure is an enlarged view of the Y part (Y1-Y4) of (C) of each figure. The figure is shown. This analysis was modeled by general-purpose fluid analysis software (Ansys Fluent (manufactured by Ansys Japan Co., Ltd.)) and carried out by steady analysis by a finite volume method. Table 1 shows the collection rate of solid particles, the maximum flow rate of exhaust gas, and the pressure loss of exhaust gas in each case. In addition, Eco in a table | surface is a economizer.

  In Case 4 (FIG. 12), the total collection rate was low and the maximum flow rate and pressure loss were high, and none of these values were the best. As shown in FIGS. 12B and 12D, the exhaust gas flow velocity after passing through the baffle plate 41 increased to 23.8 m / s or more. In case 3 (FIG. 11), although the total collection rate is higher than in case 1, the exhaust gas passes through the gap between the lower side of the baffle plate 41 and the upper part of the hopper 35 as shown in the R part, and the maximum flow velocity is 23 m. / S. If there is a portion where the flow velocity is large even locally, it becomes a cause of wear of baffle plates, hoppers, etc., and the life of these members is shortened, which is not preferable. The pressure loss was also very high compared to cases 1 and 2. The higher the flow rate, the greater the pressure loss.

  In Case 1 (FIG. 9), the total collection rate was slightly lower than in Case 3, but the maximum flow rate was suppressed to 21.5 m / s, and the pressure loss was also low. Further, in case 2 (FIG. 10), the collection rate in the A / H hopper 37 is improved by the effect of the re-scattering prevention plate 43. Moreover, the pressure loss was the lowest and the best result was obtained. Overall, it is determined that Case 1 and Case 2 are applicable.

  Further, when the baffle plate 41 is formed of a U-shaped plate (or an L-shaped cross-section as shown in FIG. 8B), the exhaust gas hits the plate as shown in FIG. 9B. When it is guided to the U-shaped space, it will be easier to flow downward. Further, the baffle plate 41 is supported by a support plate 57 (fixed to the inner wall of the duct) through which the lower part of each plate of the baffle plate 41 passes, or the upper part of each plate of the baffle plate 41 is supported by a support member 59 (fixed to the inner wall of the duct). By supporting it, the support structure is strengthened, and the swing of the baffle plate 41 due to the exhaust gas flow can be suppressed.

  Although not shown, by installing an air blaster of non-combustible gas such as nitrogen or carbon dioxide in the hopper 19a below the bag filter 19, or by increasing the diameter of the pipe where the rotary valve 45 is installed ( For example, from 50 mm to 65 mm), the ash flow becomes even smoother.

  In this example, for Case 2 where the best results were obtained, flow analysis was performed using the same analysis model as Example 1 using the dust distribution and dust density of black ash actually collected as fly ash. did. Woody biomass used as fuel is the result of elemental analysis shown in Table 2, but is obtained by crushing cedar thinned wood without subjecting it to drying or the like. In the table, “wood” refers to a material obtained by pulverizing wood into a thin rectangular shape, and “chipper” refers to a material obtained by pulverizing into a slender fiber.

  As shown in Table 2, it is not necessary to put limestone into the furnace 7 because the cedar thinning material contains almost no sulfur, unlike coal. And the woody biomass was burned on the following operating conditions using the boiler equipment shown in FIG. The boiler equipment shown in FIG. 15 is equipment (comparative example) before improvement to the equipment in FIG. 1, and the baffle plate 41 and the re-scattering prevention plate 43 are not installed, and the economizer hopper 35 and the A / A All ash and sand collected by the H hopper 37 and the bag filter 19 are sent from the fly ash silo bag filter 49 to the fly ash silo 51. Other parts are common to the boiler equipment of FIG.

  In the facility before improvement, all the ash and sand were stored in the fly ash silo 51, but there were problems such as blockage in the system, damage, wear of the transportation piping, and the like, and there was a problem in stable operation. However, improvements to the facility of FIG. 1 eliminate all problems such as blockage, damage, and wear of transportation piping in the facility system. Further, in the upstream economizer hopper 35 and the A / H hopper 37, coarse combustion ash and fluidized sand with a large amount of unburned matter are collected in the furnace 7. Furthermore, the downstream bag filter 19 collects combustion ash having a small particle size and a small amount of unburned fuel. Therefore, it is possible to improve the combustion efficiency by reducing the unburned content and reduce the replenishment amount of the fluidized sand.

  The fluidized bed boiler is a single-cylinder self-sustained natural circulation / forced circulation type boiler of the air nozzle type (supplying air from the bottom of the furnace). The furnace shape is 5.6m in width x 3.6m in depth. This is a boiler with a furnace height of 16.6 m and a power transmission end output of 5000 kW. A kerosene burner was used for start-up. Then, the wood chips were supplied from the feeder 3, put into the furnace 7, and then burned in and on the fluidized bed 61. This is a system that converts rotational energy into electricity by rotating steam generated at the fluidized bed boiler 1 to the turbine to rotate the turbine at high speed and rotating a generator connected to the turbine. Basically, it operates continuously for one year at the rated load.

  Table 3 shows the composition analysis results of black ash collected as coarse ash with a large amount of unburned ash. The fuel applied as woody biomass is chipped cedar thinned wood, but compared to general woody biomass, it has a feature that it has a lot of Ca and K as ash properties peculiar to cedar . Since these components have the property of lowering the ash melting point, caution is required for ash adhesion in the ash furnace and heat transfer tubes.

Moreover, in FIG. 13, the measurement result of the particle size distribution of the black ash analyzed by the laser method is shown. As a measuring apparatus, a laser diffraction particle size distribution measuring apparatus (model LA920) manufactured by Horiba, Ltd. was used. The average particle size of black ash dust was 290 μm, and the dust density was 0.2 t / m ³ . The conditions such as the amount of exhaust gas and the gas temperature at the entrance of the economizer hopper 35 are the same as those in the first embodiment.

  FIG. 14 shows the results of flow analysis using the same analysis model as in Example 1. The analysis conditions are the same as in Example 1 except for the average particle diameter and dust density of the dust. The solid line indicates the collection rate of the upstream economizer hopper 35, the broken line indicates the collection rate of the downstream A / H hopper 37, and the alternate long and short dash line indicates the black ash passage rate (passage rate of both hoppers). ). For example, ash with a particle size of 1000 μm describes the result of 76% collection by the upstream hopper, 19% collection by the downstream hopper, and the remaining 5% passing through the outflow surface (100% in total).

  Among the ash, coarse ash having a relatively large particle diameter is scattered on the bag filter 19 without burning out, thereby causing damage or wear. According to FIG. 14, when the collection rates of the upstream economizer hopper 35 and the downstream A / H hopper 37 are totaled, especially coarse ash having a particle size of 1.5 mm (1500 μm) or more has almost the passing rate. As a result, it was zero and it was almost possible to collect. Even ash with a particle size of about 1000 μm had a collection rate of 95%. Since the ash having a large particle size is likely to fall, it is mainly collected by the upstream economizer hopper 35. It can be said that it is mainly collected by the A / H hopper 37.

  In the thinned timber in Table 2, the total moisture is about 55% and the planned value (base condition for performance calculation etc.) is 44%, but the actual moisture of the thinned timber varies from 20% to 60%. Since the pellet-like biomass fuel is processed, the water content is adjusted to be constant, but the thinned wood collected from the raw forest is not treated at all, which results in variations in the water content.

  If only fuel with high moisture content is the planned condition, flammability can be eliminated by raising the temperature in the furnace by applying a refractory material to the furnace inner wall, but there are also fuels with low moisture content as actual operating conditions It is also necessary to consider that ash adheres to the high temperature part of the refractory material and causes the generation of clinker. Therefore, when using raw woody biomass fuel with a wide variation in moisture content, the temperature in the furnace cannot simply be raised. When a fuel with a high water content is applied, the flammability deteriorates and the amount of unburned fuel increases, which is scattered on the bag filter 19 or causes a discharge failure in the hopper 19a below the bag filter 19. However, even when such a fuel is used, the ash recovery device 100 can effectively collect coarse ash and fluid sand containing a large amount of unburned components upstream of the bag filter 19.

  In this example, in order to confirm the effect of reducing the unburned content in the ash for the case 2 where the best result was obtained, each equipment of the boiler equipment of FIG. 1 (case 2) and the boiler equipment of FIG. The unburned matter in the ash of the fly ash silo 51 was measured. The unburned ash content was calculated from the weight before and after heating by heating a 1 gram sample of combustion ash collected from the fly ash silo 51 in the air at 800 ° C. for 2 hours.

  The operating conditions of the equipment were the same as in Example 2, and when the ash was collected 22 times in the boiler equipment of FIG. 15, the proportion of unburned ash in the ash averaged in the range of 17.4 to 34.5 (%). It was 24.6 (%). Further, when the ash was collected seven times in the boiler facility of FIG. 1, the ratio of the unburned portion in the ash was an average of 16.2 (%) in the range of 10.97 to 20.6 (%). From this result, it was confirmed that the improvement was about 8%.

  Further, when the particle size distribution of ash was measured for Case 2 using the same laser diffraction particle size distribution measuring apparatus and sieve as in Example 2, ash with a particle size of 1 mm or more was 2.3% of the total ash of fly ash silo 51. Therefore, it can be said that the combustion ash of coarse particles is 2.3% or less. Most of the coarse ash is put into the economizer hopper 35 and the A / H hopper 37 by the effect of the baffle plate 41. It was confirmed that it was collected.

  From the above, it was confirmed that returning the coarse ash collected by the economizer hopper 35 and the A / H hopper 37 to the furnace 7 also reduces the unburned content. Moreover, since most of the solid particles collected by the fly ash silo 51 are fine ash, since the high quality ash can be collected, the effective use of ash is also high.

  In this example, in case 2 where the best results were obtained, the sand in each of the boiler equipment of FIG. 1 (case 2) and the boiler equipment of FIG. 15 was confirmed in order to confirm the effect of reducing the amount of sand scattering. The replenishment amount of was measured. The required amount of fluid sand was replenished from the sand silo 31 using a flexible container bag of 1.25 tons per bag. Specifically, when the bed height (layer thickness) calculated by the differential pressure between the lower part and the upper part of the fluidized bed 61 is displayed in the central operation room by the control device, when the bed height becomes lower than the predetermined bed height. Fluid sand was replenished. The measurement period was 28 days.

  The replenishment amount of sand in the boiler facility of FIG. 15 was 10 t (total amount for 28 days), whereas the replenishment amount of sand in the boiler facility of FIG. 1 was 1.25 t (total amount for 28 days). Therefore, the replenishment amount of sand was remarkably reduced to 12.5% before improvement.

  As an ash recovery device that recovers ash from combustion gas discharged from a combustion device such as a boiler, it may be used.

DESCRIPTION OF SYMBOLS 1 Fluidized bed boiler 3 Feeder 5 Burner 7 Furnace 9 Outlet part 11 Superheater 13 Evaporative water pipe part 15 Eco-container 17 A / H 19 Bag filter 21 Chimney 23 Ejector 25 Separator 27 Fan 29 Sand supply silo 31 Sand silo 35 Section Charcoal hopper 37 A / H hopper 39 Sand bag filter 40 Exhaust gas duct 41 Baffle plate 43 Re-scattering plate 45 Rotary valve 47 Vacuum pump 49 Fly ash silo bag filter 51 Fly ash silo 53 Valve 55 Pressure equalization piping 56 Circulation piping 57 support plate 59 support member 61 fluidized bed 63 damper 65 primary air piping 67 secondary air piping 69 after air port 100 ash recovery device

Claims (6)

A economizer that exchanges heat between exhaust gas and water discharged from a combustion device that uses woody biomass as fuel, an air preheater that exchanges heat between exhaust gas and air, and a bag filter that collects soot and dust in the exhaust gas Is a solid particle recovery device that recovers solid particles in the exhaust gas flowing through the exhaust gas duct sequentially provided from the upstream side to the downstream side of the exhaust gas flow direction,
The solid particle recovery device is provided in the exhaust gas duct below the economizer, and is provided in the economizer-side hopper capable of recovering solid particles in the exhaust gas, and the exhaust gas duct below the air preheater, and the solid particles in the exhaust gas Equipped with an air preheater side hopper capable of recovering and a hopper at the bottom of the bag filter,
A baffle plate having a flat portion facing the exhaust gas flow direction upstream of the air preheater side hopper in the exhaust gas flow direction and guiding solid particles in the exhaust gas to the economizer hopper and the air preheater side hopper, A solid particle recovery apparatus, wherein the upper end of the baffle plate is located above the hopper edge and the lower end is located below the hopper edge.   A re-scattering prevention plate that has a flat portion facing the hopper bottom in the air preheater side hopper downstream of the baffle plate in the exhaust gas flow direction and prevents the solid particles in the hopper from scattering outside the hopper. 2. The solid particle recovery apparatus according to claim 1, wherein the re-scattering prevention plate is disposed so that an upper end thereof is below the hopper edge.   3. The solid particle recovery device according to claim 1, wherein the baffle plate is disposed so that an upper end of the baffle plate is located above an exhaust gas duct above the air preheater-side hopper.   The solid particle recovery device according to any one of claims 1 to 3, wherein the economizer-side hopper and the air preheater-side hopper are disposed adjacent to each other.   5. The solid particle recovery apparatus according to claim 1, wherein the baffle plate has a configuration in which a plurality of elongated plate members are arranged in a staggered manner in an exhaust gas flow direction. A fluidized bed boiler powered by woody biomass,
Exhaust gas flows through a economizer that exchanges heat between the exhaust gas discharged from the fluidized bed boiler and water, an air preheater that exchanges heat between the exhaust gas and air, and a bag filter that collects dust in the exhaust gas. Exhaust gas duct sequentially provided from the upstream side to the downstream side,
The solid particle recovery device according to any one of claims 1 to 5,
A fluidized bed boiler facility comprising a circulation unit for sending solid particles in the economizer hopper and the air preheater side hopper to a fluidized bed boiler.