Method and system for reducing carbon content of fly ash of circulating fluidized bed boiler

Abstract

The invention belongs to the technical field of circulating fluidized bed boilers, and discloses a method and system for reducing the carbon content of fly ash of a circulating fluidized bed boiler. The method comprises the steps that ash in a coarse ash silo is fed into a fly ash sorting device through a belt feeder to be preliminarily settled and screened, and meanwhile primary air or secondary air is fed into a feeding port of the belt feeder and an air inlet in the bottom of the fly ash sorting device; the fly ash subjected to primary settling and screening enters a short cone cyclone separation chamber to be subjected to cyclone separation; unburned carbon particles flow out of the bottom of the short-cone cyclone separation chamber and enter a carbon-rich ash collection bin for enrichment, and residual unenriched fly ash is conveyed into a fine ash warehouse through an inner cylinder of the short-cone cyclone separation chamber. According to the method and system, the fly ash in the coarse ash silo is subjected to preliminary screening and rotary separation enrichment to obtain the carbon particles, the carbon content of the fly ash of the circulating fluidized bed boiler can be remarkably reduced, meanwhile, the carbon particles obtained through enrichment can serve as fuel for secondary utilization, and the comprehensive utilization rate of the fly ash of the circulating fluidized bed boiler is effectively increased.

Description

Technical Field

[0001] The invention belongs to the technical field of circulating fluidized bed boiler energy conservation, and in particular relates to a method and a system for reducing the carbon content of fly ash of a circulating fluidized bed boiler. Background Art

[0002] The carbon content of fly ash is an important indicator for measuring the combustion efficiency of boilers. Excessive carbon content in fly ash will increase fuel consumption, easily cause secondary combustion in the tail flue, and reduce the combustion efficiency and safety of the boiler. At the same time, the carbon content of fly ash is also a key indicator affecting the quality of fly ash. Indicators such as the loss on ignition and water demand ratio of fly ash directly affect the downstream market application of fly ash, which restricts the market application of fly ash, a large industrial solid waste, and has a significant negative impact on environmental protection.

[0003] With the increasingly tight power coal market in recent years, coal prices have risen sharply, and circulating fluidized bed boilers (CFB boilers) have been widely used due to their outstanding advantages such as wide fuel adaptability and low pollutant emissions. However, circulating fluidized bed boilers burn low-quality coal, especially low-volatile low-quality coal, and there is a problem of high carbon content in fly ash, which can be as high as 10%-25%, reducing boiler efficiency, increasing energy losses, and greatly limiting the comprehensive utilization of fly ash in circulating fluidized bed boilers (because the fly ash used in concrete requires a loss on ignition of no more than 5.0%, and excessive residual carbon will affect the strength of fly ash products and reduce the freeze-thaw resistance and impermeability of fly ash products).

[0004] At present, there are some solutions to the problem of high carbon content in fly ash of CFB boilers. Please refer to the patented fly ash bottom feeding circulating fluidized bed boiler combustion method and device for difficult-to-burn fuel (patent application number is 200310106047.8) and the gradually converging and expanding pipes and ash return pumps and fly ash reburning circulating fluidized bed combustion equipment (patent application number is 200710054674.X). The former returns the fly ash to the bottom of the dense phase zone of the furnace for combustion, and the latter returns the fly ash to the upper part of the dense phase zone for combustion. Both methods have a very limited reduction in the carbon content of fly ash in the circulating fluidized bed boiler due to the high fluidizing wind speed in the furnace (usually 5-7m / s) and the short residence time of the fly ash in the high temperature zone of the furnace.

[0005] Patent document CN102927564A discloses a method for reducing the carbon content of fly ash in a circulating fluidized bed boiler. When the circulating fluidized bed boiler includes a furnace, a cyclone separator, a riser and a return device, the method steps are as follows: 1) a screw feeder is installed on the upper part of the riser, and an oxygen-enriched air generator is connected to the air inlet chamber at the bottom of the return device; 2) when the circulating fluidized bed boiler is running, the screw feeder feeds fly ash into the upper part of the riser, and the fly ash enters the return device through the riser. In the return device, coke in the fly ash reacts with oxygen-enriched air generated by the oxygen-enriched air generator to undergo oxygen-enriched combustion reaction. During the reaction, the fly ash combustion temperature is controlled by adjusting the volume percentage of oxygen in the oxygen-enriched air. After the reaction, the fly ash and flue gas return to the furnace. The method of this patent directly sends fly ash into the return material device for oxygen-enriched combustion. Since the return material device contains high-temperature ash, its temperature is measured by a thermocouple and there is a temperature limit. Too high a temperature will cause the return material device to burn and crack, resulting in ash leakage, which may cause the furnace to shut down in severe cases. In actual working processes, oxygen-enriched combustion is not allowed at the return material device.

[0006] In actual applications, some power plants have too high carbon content in fly ash. In order to reduce the carbon content of fly ash and reuse it, they choose to mix the fly ash collected by the bag filter with the ash collected by the drum slag cooler and send it to the raw coal bunker again. Then, they are sent to the furnace together with the raw coal through the coal feeder for combustion. However, such operation is prone to the following problems:

[0007] (1) The average calorific value of the fuel decreases, making it difficult for the boiler to heat up. The boiler can maintain operation at low loads, but becomes difficult to operate when the load is increased.

[0008] (2) After the cold ash with low calorific value enters the boiler, the heat it emits is low, which will cause the bed temperature to drop, making it difficult to increase the temperature and pressure of the main reheat steam.

[0009] (3) The circulating fluidized bed boiler has a limited furnace volume and is difficult to meet the specified volumetric heat load and cross-sectional heat load. When too much low calorific value ash enters, the boiler efficiency decreases.

[0010] In other power plants, the dust removal is done by using an electrostatic precipitator, which returns the fly ash with a high carbon content under the electric field to the boiler for secondary combustion; the specific method is to directly send the fly ash from the electrostatic precipitator into the combustion chamber for recirculation and combustion through a material sealing pump. This system has a simple structure, is easy to operate, and has a low cost, but it still cannot solve the problem of reducing boiler combustion efficiency. In addition, since it is directly sent into the combustion chamber, it is necessary to open a hole in the furnace. If the hole position is not suitable, or the return material is not good, it will cause unstable combustion, severe fluctuations in bed temperature, and low or overheating of the boiler heating surface. Summary of the invention

[0011] The present invention aims to solve at least one technical problem existing in the background technology, and provides a method and system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, so as to overcome the problems existing in the existing methods for reducing the carbon content of fly ash, such as the limited reduction range of the carbon content of fly ash and the reduced boiler combustion efficiency. By preliminarily screening and rotating the fly ash in the coarse ash bin to enrich the carbon particles, the carbon content of the fly ash of the circulating fluidized bed boiler can be greatly reduced. At the same time, the enriched carbon particles can be used as fuel for secondary utilization, which can effectively improve the comprehensive utilization rate of the fly ash of the circulating boiler.

[0012] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0013] A method for reducing the carbon content of fly ash in a circulating fluidized bed boiler, the method comprising the following steps:

[0014] Step S1: The ash in the coarse ash bin is fed into the fly ash selection device through a belt feeder for preliminary sedimentation and screening. At the same time, the primary air or the secondary air is fed into the feed port of the belt feeder and the bottom air inlet of the fly ash selection device respectively;

[0015] Step S2: After the fly ash is initially settled and screened by the fly ash selection device, the fly ash enters the short cone cyclone separation chamber for cyclone separation;

[0016] Step S3: The unburned carbon particles obtained by cyclone separation flow out from the bottom of the short cone cyclone separation chamber and enter the carbon-rich ash collection bin for enrichment; the remaining unenriched fly ash is sent to the fine ash storage through the inner cylinder of the short cone cyclone separation chamber.

[0017] Furthermore, a coarse screen layer and a fine screen layer are arranged inside the fly ash selection device from top to bottom.

[0018] Furthermore, the coarse mesh layer uses a 200-250 μm mesh as a bed layer; the fine mesh layer uses a 180-200 μm mesh as a bed layer.

[0019] Furthermore, the coarse mesh layer and the fine mesh layer are both located below the ash inlet of the fly ash selection device.

[0020] Furthermore, the cone angle of the cone part of the short cone cyclone separation chamber is 120-140°, and the cone height is shortened to 1 / 3-1 / 2 of the original height H.

[0021] Furthermore, in step S3, the carbon particles enriched in the carbon-rich ash collection bin are directly connected to the furnace through a return pipe for return combustion, or sent to a coal bunker for temporary storage.

[0022] At the same time, the present invention also provides a system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, the system comprising a coarse ash bin, a belt feeder, a fly ash selection device, a short cone cyclone separation chamber and a carbon-rich ash collection bin connected in sequence; at the same time, the primary air or secondary air duct of the circulating fluidized bed boiler is respectively connected to the feed port of the belt feeder and the bottom air inlet of the fly ash selection device;

[0023] The ash in the coarse ash bin is sent to the fly ash selection device through a belt feeder for preliminary sedimentation and screening. The fly ash after preliminary sedimentation and screening enters the short cone cyclone separation chamber for cyclone separation; the separated carbon particles flow out from the bottom of the short cone cyclone separation chamber into the carbon-rich ash collection bin, and the remaining unenriched fly ash is sent to the fine ash bin through the inner cylinder of the short cone cyclone separation chamber.

[0024] Furthermore, a coarse screen layer and a fine screen layer are arranged inside the fly ash selection device from top to bottom.

[0025] Furthermore, the coarse mesh layer uses a 200-250 μm mesh as a bed layer; the fine mesh layer uses a 180-200 μm mesh as a bed layer.

[0026] Furthermore, the coarse mesh layer and the fine mesh layer are both located below the ash inlet of the fly ash selection device.

[0027] Furthermore, the cone angle of the cone part of the short cone cyclone separation chamber is 120-140°, and the cone height is shortened to 1 / 3-1 / 2 of the original height H.

[0028] Furthermore, the carbon particles enriched in the carbon-rich ash collection bin are directly connected to the furnace through a return pipe for return combustion, or sent to a coal bunker for temporary storage.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] (1) The present invention provides a method and system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, which overcomes the problems of limited reduction of the carbon content of fly ash and reduced boiler combustion efficiency in existing methods for reducing the carbon content of fly ash. The fly ash in the coarse ash bin is first subjected to preliminary sedimentation and screening, and then subjected to cyclone separation and enrichment to obtain carbon particles, thereby significantly reducing the carbon content of the fly ash in the circulating fluidized bed boiler. At the same time, the enriched carbon particles can be used as fuel for secondary utilization, which can effectively improve the comprehensive utilization rate of the fly ash in the circulating fluidized bed boiler.

[0031] (2) The present invention provides a method and system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, wherein the primary air or secondary air of the fluidized bed boiler is respectively fed into the feed port of a belt feeder and the bottom air inlet of a fly ash selection device, wherein the primary air or secondary air fed into the feed port of the belt feeder is used as the sealing air of the coal feeder; the primary air or secondary air fed into the bottom air inlet of the fly ash selection device is used to disturb the fly ash material above the screen, intensify the collision between the fly ash material particles, avoid the agglomeration of the fly ash material, improve the uniformity of the material flow, and improve the sedimentation screening effect;

[0032] (3) The present invention provides a method and system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, wherein fly ash in a coarse ash bin is first subjected to preliminary sedimentation and screening through coarse and fine screens built into a fly ash selection device, so that the glass phase and crystalline phase with higher density in the fly ash are separated first, and larger particles are settled on the upper coarse screen, and smaller particles are settled on the lower fine screen, thereby making full use of the screen's sieve hole air supply channel and heavy object bearing function to prevent carbon particles from blocking the air inlet at the bottom of the fly ash selection device;

[0033] (4) The present invention provides a method and system for reducing the carbon content of fly ash in a circulating fluidized bed boiler. When a short-cone cyclone separation chamber is used for cyclone separation, the separation efficiency and separation effect can be improved by increasing the cone angle of the cone of the short-cone cyclone separation chamber and shortening the cone length. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a fly ash selection device according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of a short cone cyclone separation chamber according to an embodiment of the present invention;

[0036] Figure 3 It is a short cone dimension diagram of the short cone cyclone separation chamber in an embodiment of the present invention;

[0037] Markings in the figure: 1-belt feeder; 2-coarse screen layer; 3-fine screen layer; 4-fly ash selection device; 5-short cone cyclone separation chamber; 6-carbon-rich ash collection bin. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] The fly ash from circulating fluidized bed boiler is generally divided into coarse ash and fine ash. The coarse ash has a high carbon content, so the ash in the coarse ash storage is selected for carbon enrichment.

[0041] Combination Figure 1-2 As shown, an embodiment of the present invention provides a method for reducing the carbon content of fly ash in a circulating fluidized bed boiler, the method comprising the following steps:

[0042] Step S1: The ash in the coarse ash bin is fed into the fly ash selection device 4 through the belt feeder 1 for preliminary sedimentation and screening. At the same time, the primary air or secondary air of the fluidized bed boiler is fed into the feed port of the belt feeder 1 and the bottom air inlet of the fly ash selection device 4 respectively.

[0043] Among them, the primary air or secondary air fed into the feeding port of the belt feeder 1 is used as the sealing air of the coal feeder; the primary air or secondary air fed into the bottom air inlet of the fly ash selection device 4 is used to disturb the fly ash material above the screen, intensify the collision between the fly ash material particles, avoid the agglomeration of the fly ash material, improve the uniformity of the material flow, and improve the sedimentation screening effect.

[0044] A coarse screen layer 2 and a fine screen layer 3 are arranged from top to bottom inside the fly ash selection device 4, which are used to perform preliminary sedimentation screening on the fly ash by density screening.

[0045] Because the main components of fly ash are composed of three types of minerals: glass phase, amorphous phase and crystalline phase. The glass phase is mainly composed of floating beads, micro beads and magnetic beads; the amorphous phase is mostly unburned carbon particles; the crystalline phase is mullite, quartz sand, magnetite, hematite, periclase, etc. Most of the unburned carbon in fly ash exists in the form of monomers, and the carbon particles in the amorphous phase are sponge-like and honeycomb-like; the component density of the glass phase and the crystalline phase is much greater than that of the carbon particles in the amorphous phase, so the fly ash is first separated by the primary air or secondary air under the screen, and the carbon particles in the glass phase and the crystalline phase are settled and separated, and the coarse screen layer 2 receives the larger carbon particles, and the fine screen layer 3 receives the smaller carbon particles, so as to make full use of the screen mesh air supply channel and the function of bearing heavy objects, and avoid carbon particles blocking the air inlet at the bottom of the fly ash selection device 4.

[0046] Taking into account the particle size of fly ash and the resistance of the sieve holes to the conveying air, the coarse mesh layer 2 uses a 200-250 μm mesh as the bed layer; the fine mesh layer 3 uses a 180-200 μm mesh as the bed layer. At the same time, the coarse mesh layer 2 and the fine mesh layer 3 are both located below the ash inlet of the fly ash selection device 4.

[0047] Step S2: After preliminary sedimentation and screening by the fly ash selection device 4, the fly ash enters the short cone cyclone separation chamber 5 for cyclone separation;

[0048] The short cone cyclone separation chamber 5 is an effective separation and dust collection device which utilizes the centrifugal force field to accelerate the settling of solid particles in the dust-laden airflow and strengthen the separation process. The separation process is completed under the action of the centrifugal force field.

[0049] The separated materials are distributed in order according to particle size and density along the radial and axial directions under the action of centrifugal force field. The basic distribution law is that the materials gradually increase from the axis of the separation chamber along the radial direction to the wall and from top to bottom along the longitudinal direction.

[0050] The larger the cone angle of the cone part of the short cone cyclone separation chamber 5 is, the more obvious the tendency of separating fly ash by density is. This is because the purpose of the short cone cyclone separation chamber 5 is to separate and enrich carbon in fly ash. Therefore, the structural characteristics of the short cone cyclone used for mineral processing are used to modify the cone part of the conventional cyclone separator, increase the cone angle, and shorten the cone length.

[0051] Therefore, if Figure 3 As shown, the cone angle of the cone part of the short cone cyclone separation chamber 5 in the embodiment of the present invention is 120-140°, preferably 130°; the cone height is shortened to 1 / 3-1 / 2 of the original height H, preferably 1 / 2H, which is a short cone cyclone.

[0052] Step S3: After cyclone separation in the short cone cyclone separation chamber 5, the separated unburned carbon particles flow out from the bottom of the short cone cyclone separation chamber 5 and enter the carbon-rich ash collection bin 6 for enrichment, while the remaining ultrafine fly ash that has not been enriched is sent to the fine ash storage through the inner cylinder of the short cone cyclone separation chamber 5.

[0053] The carbon particles accumulated in the carbon-rich ash collecting bin 6 are carbon-rich ash with a high carbon content, which can be directly connected to the furnace through a return pipe for return combustion, or sent to a coal bunker for temporary storage.

[0054] Example 2

[0055] Combination Figure 1-2 As shown, an embodiment of the present invention provides a system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, which is used to implement the method in Example 1.

[0056] The system includes a coarse ash bin, a belt feeder 1, a fly ash selection device 4, a short cone cyclone separation chamber 5 and a carbon-rich ash collection bin 6 which are connected in sequence; at the same time, the primary air or secondary air duct of the circulating fluidized bed boiler is respectively connected to the feed port of the belt feeder 1 and the bottom air inlet of the fly ash selection device 4.

[0057] Among them, the primary air or secondary air fed into the feeding port of the belt feeder 1 is used as the sealing air of the coal feeder; the primary air or secondary air fed into the bottom air inlet of the fly ash selection device 4 is used to disturb the fly ash material above the screen, intensify the collision between the fly ash material particles, avoid the agglomeration of the fly ash material, improve the uniformity of the material flow, and improve the sedimentation screening effect.

[0058] The ash in the coarse ash store is fed into the fly ash selection device 4 through the belt feeder 1, and then is subjected to sedimentation and screening in the fly ash selection device 4.

[0059] Specifically, a coarse screen layer 2 and a fine screen layer 3 are arranged from top to bottom inside the fly ash selection device 4, which are used to perform preliminary sedimentation screening on the fly ash through density screening.

[0060] Because the main components of fly ash are composed of three types of minerals: glass phase, amorphous phase and crystalline phase, among which the glass phase is mainly composed of floating beads, micro beads and magnetic beads, etc.; the amorphous phase is mostly unburned carbon particles; the crystalline phase is mullite, quartz sand, magnetite, hematite, periclase, etc. Most of the unburned carbon in fly ash exists in the form of monomers, and the carbon particles in the amorphous phase are sponge-like and honeycomb-like; the component density of the glass phase and the crystalline phase is much greater than that of the carbon particles in the amorphous phase, so the fly ash is first separated by the primary air or secondary air under the screen, and the carbon particles in the glass phase and the crystalline phase are settled and separated, and the coarse screen layer 2 receives the larger carbon particles, and the fine screen layer 3 receives the smaller carbon particles, so as to make full use of the screen mesh air supply channel and the function of bearing heavy objects, and avoid carbon particles blocking the air inlet at the bottom of the fly ash selection device 4.

[0061] Taking into account the particle size of fly ash and the resistance of the sieve holes to the conveying air, the coarse mesh layer 2 uses a 200-250 μm mesh as the bed layer; the fine mesh layer 3 uses a 180-200 μm mesh as the bed layer; at the same time, the coarse mesh layer 2 and the fine mesh layer 3 are both located below the ash inlet of the fly ash selection device 4.

[0062] The fly ash after preliminary sedimentation and screening by the fly ash selection device 4 enters the short cone cyclone separation chamber 5 for cyclone separation.

[0063] The short cone cyclone separation chamber 5 is an effective separation and dust collection device that uses the centrifugal force field to accelerate the sedimentation of solid particles in the dust-laden airflow and strengthen the separation process. The separation process is completed under the action of the centrifugal force field. Under the action of the centrifugal force field, the separated materials are orderly distributed in the radial and axial directions according to the particle size and density. The basic distribution law is: from the axis of the separation chamber to the wall and from top to bottom along the radial direction and longitudinal direction.

[0064] The larger the cone angle of the cone part of the short cone cyclone separation chamber 5 is, the more obvious the tendency of separating fly ash by density is. This is because the purpose of the short cone cyclone separation chamber 5 is to separate and enrich carbon in fly ash. Therefore, the structural characteristics of the short cone cyclone used for mineral processing are used to modify the cone part of the conventional cyclone separator, increase the cone angle, and shorten the cone length.

[0065] Therefore, if Figure 3 As shown, the cone angle of the cone part of the short cone cyclone separation chamber 5 in the embodiment of the present invention is 120-140°, preferably 130°; the cone height is shortened to 1 / 3-1 / 2 of the original height H, preferably 1 / 2H, which is a short cone cyclone.

[0066] After separation in the short cone cyclone separation chamber 5, the separated unburned carbon particles flow out from the bottom of the short cone cyclone separation chamber 5 into the carbon-rich ash collection bin 6, while the remaining ultra-fine fly ash that has not been enriched is sent to the fine ash storage through the inner cylinder of the short cone cyclone separation chamber 5.

[0067] The carbon particles accumulated in the carbon-rich ash collecting bin 6 are carbon-rich ash with high carbon content, which can be used as fuel for secondary utilization, such as being directly connected to the furnace for combustion through a return pipe, or being sent to a coal bunker for temporary storage.

[0068] The above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the application scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing the carbon content of fly ash in a circulating fluidized bed boiler, characterized in that: The method comprises the following steps: Step S1: The ash in the coarse ash bin is fed into the fly ash selection device through a belt feeder for preliminary sedimentation and screening. At the same time, the primary air or the secondary air is fed into the feed port of the belt feeder and the bottom air inlet of the fly ash selection device respectively; Step S2: After the fly ash is initially settled and screened by the fly ash selection device, the fly ash enters the short cone cyclone separation chamber for cyclone separation; Step S3: The unburned carbon particles obtained by cyclone separation flow out from the bottom of the short cone cyclone separation chamber and enter the carbon-rich ash collection bin for enrichment; the remaining unenriched fly ash is sent to the fine ash storage through the inner cylinder of the short cone cyclone separation chamber.

2. The method according to claim 1, characterized in that A coarse screen layer and a fine screen layer are arranged inside the fly ash selection device from top to bottom.

3. The method according to claim 2, characterized in that: The coarse mesh layer uses a 200-250 μm mesh as the bed layer; the fine mesh layer uses a 180-200 μm mesh as the bed layer.

4. The method according to claim 2 or 3, characterized in that: The coarse screen layer and the fine screen layer are both located below the ash inlet of the fly ash selection device.

5. The method according to claim 1, characterized in that The cone angle of the cone part of the short cone cyclone separation chamber is 120-140°, and the cone height is shortened to 1 / 3-1 / 2 of the original height H.

6. The method according to claim 1, characterized in that In step S3, the carbon particles accumulated in the carbon-rich ash collection bin are directly connected to the furnace through a return pipe for return combustion, or sent to a coal bunker for temporary storage.

7. A system for reducing the carbon content of fly ash in a circulating fluidized bed boiler, characterized in that: The system comprises a coarse ash storage, a belt feeder, a fly ash selection device, a short cone cyclone separation chamber and a carbon-rich ash collection bin which are connected in sequence; at the same time, the primary air or secondary air duct of the circulating fluidized bed boiler is respectively connected to the feed port of the belt feeder and the bottom air inlet of the fly ash selection device; The ash in the coarse ash bin is sent to the fly ash selection device through a belt feeder for preliminary sedimentation and screening. The fly ash after preliminary sedimentation and screening enters the short cone cyclone separation chamber for cyclone separation; the separated carbon particles flow out from the bottom of the short cone cyclone separation chamber into the carbon-rich ash collection bin, and the remaining unenriched fly ash is sent to the fine ash bin through the inner cylinder of the short cone cyclone separation chamber.

8. The system according to claim 7, characterized in that A coarse screen layer and a fine screen layer are arranged inside the fly ash selection device from top to bottom.

9. The system according to claim 8, characterized in that The coarse mesh layer uses a 200-250 μm mesh as the bed layer; the fine mesh layer uses a 180-200 μm mesh as the bed layer.

10. The system according to claim 8 or 9, characterized in that The coarse screen layer and the fine screen layer are both located below the ash inlet of the fly ash selection device.

11. The system according to claim 9, characterized in that The cone angle of the cone part of the short cone cyclone separation chamber is 120-140°, and the cone height is shortened to 1 / 3-1 / 2 of the original height H.

12. The system according to claim 7, characterized in that The carbon particles accumulated in the carbon-rich ash collection bin are directly connected to the furnace through a return pipe for return combustion, or sent to a coal bunker for temporary storage.

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