A method and system for reducing carbon content of fly ash from a circulating fluidized bed boiler

Abstract

The present application belongs to the technical field of circulating fluidized bed boiler, and discloses a method and system for reducing carbon content of fly ash of a circulating fluidized bed boiler.The method comprises: fly ash in a coarse ash bin is sent into a fly ash sorting device for preliminary settling and screening through a belt feeder, and primary air or secondary air is respectively sent into a feeding port of the belt feeder and an air inlet at the bottom of the fly ash sorting device; fly ash after preliminary settling and screening is sent into a short-cone cyclone separation chamber for cyclone separation; unburned carbon particles flow out from the bottom of the short-cone cyclone separation chamber into a carbon-rich ash collection bin for enrichment, and the remaining fly ash that is not enriched is sent to a fine ash bin through an inner cylinder of the short-cone cyclone separation chamber.The method and system can significantly reduce the carbon content of fly ash of a circulating fluidized bed boiler by preliminarily screening and rotatingly separating and enriching fly ash in a coarse ash bin to obtain carbon particles, and the obtained carbon particles can be used as fuel for secondary use, thereby effectively improving the comprehensive utilization rate of fly ash of a circulating boiler.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of circulating fluidized bed boiler, and particularly relates to a method and system for reducing carbon content of fly ash of a circulating fluidized bed boiler. BACKGROUND

[0002] The carbon content of fly ash is an important indicator for measuring the combustion efficiency of a boiler, and an excessive carbon content of fly ash will increase fuel consumption, 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, and indicators such as the loss on ignition and water requirement 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 great negative impact on environmental protection.

[0003] With the increasingly tight market of electric coal in recent years, the price of coal has risen sharply, and the circulating fluidized bed boiler (CFB boiler) has been widely used due to its outstanding advantages such as wide fuel adaptability and low pollutant emission. However, the circulating fluidized bed boiler burns low-quality coal, especially low-volatile low-quality coal, and has the problem of high carbon content of fly ash, which can be as high as 10%-25%, reducing the efficiency of the boiler and increasing energy loss, and greatly limiting the comprehensive utilization of fly ash of the circulating fluidized bed boiler (because the fly ash used in concrete requires a loss on ignition of not more than 5.0%, and excessive residual carbon will affect the strength of fly ash products, reducing the frost resistance and impermeability of fly ash products).

[0004] Currently, there are some solutions to the problem of high carbon content of fly ash of a CFB boiler, such as a fly ash bottom feeding circulating fluidized bed boiler combustion method and device for non-combustible fuel (patent application number 200310106047.8) and a gradually tapered and gradually expanded pipe, a fly ash return pump, and a fly ash reburning type circulating fluidized bed combustion equipment (patent application number 200710054674.X). The former returns fly ash to the bottom of the dense phase zone of the furnace for combustion, and the latter returns 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 of the circulating fluidized bed boiler due to the high fluidization wind speed in the furnace (usually 5-7 m / s) and the short residence time of 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 comprises a furnace, a cyclone separator, a standpipe and a return material device, the method steps are as follows: 1) a screw feeder is installed on the upper part of the standpipe, and an oxygen-enriched air generator is connected to the bottom of the return material device; 2) when the circulating fluidized bed boiler is running, the screw feeder sends fly ash into the upper part of the standpipe, the fly ash enters the return material device through the standpipe, and the coke in the fly ash in the return material device has an oxygen-enriched combustion reaction with the oxygen-enriched air generated by the oxygen-enriched air generator. In the reaction, the combustion temperature of the fly ash is controlled by adjusting the volume percentage of oxygen in the oxygen-enriched air, and after the reaction, the fly ash and flue gas return to the furnace. The method of the patent directly sends fly ash into the return material device for oxygen-enriched combustion. Since the return material device is high-temperature ash, its temperature is measured by a thermocouple, and there is a temperature limit. If the temperature is too high, the return material device will crack due to high temperature, causing ash leakage, and in severe cases, the boiler will be shut down. In actual work, oxygen-enriched combustion is not allowed in the return material device.

[0006] In actual application, due to the high carbon content of fly ash in some power plants, in order to reduce the carbon content of fly ash and reuse it, fly ash collected by a bag-type dust collector and ash collected by a roller cold slag collector are mixed and then sent into a raw coal bin again, and then sent into a furnace together with raw coal through a coal feeder for combustion. However, such operation is prone to the following problems:

[0007] (1) The average heat value of the fuel is reduced, the boiler is difficult to heat up, and the boiler can maintain operation at low load, but it is difficult to operate at high load;

[0008] (2) The low-heat-value cold ash entering the boiler has low heat emission, which can cause the bed temperature to drop, and the main and reheat steam temperature to be difficult to rise;

[0009] (3) The circulating fluidized bed boiler has limited internal volume, and it is difficult to meet the specified volumetric heat load and cross-sectional heat load. Too much low-heat-value ash entering the boiler reduces the boiler efficiency.

[0010] There are also power plants that use electrostatic precipitators to return fly ash with high carbon content under the electric field to the boiler for secondary combustion. The specific way is to directly send the fly ash of the electrostatic precipitator into the combustion chamber through a seal pump for recirculation combustion. This system is simple in structure, easy to operate and low in cost, but it still cannot solve the problem of reducing the combustion efficiency of the boiler. In addition, since it is directly sent into the combustion chamber, a hole needs to be opened in the furnace. If the hole position is not suitable or the return material is not good, it will cause unstable combustion, serious bed temperature fluctuation, low or over-temperature of the boiler heating surface. SUMMARY

[0011] The present application aims to solve at least one technical problem in the background art, and 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 in the carbon content of fly ash and reduced combustion efficiency of the boiler in the existing method for reducing the carbon content of fly ash. The carbon particles obtained by preliminary screening and rotational separation of fly ash in the coarse ash bin can significantly reduce the carbon content of 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 circulating boiler fly ash.

[0012] To achieve the above technical purposes, the present application 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 sent into the fly ash sorting device through the belt feeder for preliminary settling and screening. At the same time, primary air or secondary air is respectively sent into the feed inlet of the belt feeder and the bottom air inlet of the fly ash sorting device.

[0015] Step S2: The fly ash after preliminary settling and screening in the fly ash sorting device is subjected to cyclone separation in the short-cone cyclone separation chamber.

[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 fly ash that is not enriched is sent to the fine ash bin through the inner cylinder of the short-cone cyclone separation chamber.

[0017] Further, the fly ash sorting device is internally provided with a coarse screen layer and a fine screen layer from top to bottom.

[0018] Further, the coarse screen layer is selected to have a bed layer of 200-250 μm hole screen, and the fine screen layer is selected to have a bed layer of 180-200 μm hole screen.

[0019] Further, the coarse screen layer and the fine screen layer are both located below the ash inlet of the fly ash sorting device.

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

[0021] Further, in step S3, the carbon particles enriched in the carbon-rich ash collection bin are directly connected to the furnace back for combustion by a back connection pipe, or are sent to the coal bin for temporary storage.

[0022] Meanwhile, the application also provides a system for reducing the carbon content of fly ash of a circulating fluidized bed boiler, which comprises a coarse ash bin, a belt feeder, a fly ash screening device, a short-cone cyclone separation chamber and a carbon-rich ash collection bin connected in sequence; meanwhile, the primary air or secondary air pipeline of the circulating fluidized bed boiler is connected to the feeding port of the belt feeder and the bottom air inlet of the fly ash screening device, respectively.

[0023] The fly ash in the coarse ash bin is sent into the fly ash screening device by the belt feeder for preliminary settling and screening, and the fly ash after the preliminary settling and screening is sent into the short-cone cyclone separation chamber for cyclone separation; the carbon particles obtained by the separation flow out from the bottom of the short-cone cyclone separation chamber into the carbon-rich ash collection bin, and the remaining fly ash not enriched is sent to the fine ash bin through the inner cylinder of the short-cone cyclone separation chamber.

[0024] Further, the fly ash screening device is internally provided with a coarse screen layer and a fine screen layer from top to bottom.

[0025] Further, the coarse screen layer is selected to be a 200-250 mu m hole screen as a bed layer, and the fine screen layer is selected to be a 180-200 mu m hole screen as a bed layer.

[0026] Further, the coarse screen layer and the fine screen layer are both located below the fly ash inlet of the fly ash screening device.

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

[0028] Further, the carbon particles enriched in the carbon-rich ash collection bin are directly connected to the furnace back for combustion by a back connection pipeline, or are sent to a coal bin for temporary storage.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] (1) The method and system for reducing the carbon content of fly ash of a circulating fluidized bed boiler provided by the application overcome the problems of limited reduction of the carbon content of fly ash and reduced combustion efficiency of the boiler in the prior art, and the carbon particles obtained by the preliminary settling and screening and cyclone separation of the fly ash in the coarse ash bin can greatly reduce the carbon content of the fly ash of the circulating fluidized bed boiler, and the carbon particles can be used as fuel for secondary use, thereby effectively improving the comprehensive utilization rate of the fly ash of the circulating boiler.

[0031] (2) The application provides a method and system for reducing the carbon content of fly ash of a circulating fluidized bed boiler, and the primary air or the secondary air of the fluidized bed boiler is respectively sent into a feeding port of a belt feeder and a bottom air inlet of a fly ash screening device, wherein the primary air or the secondary air sent into the feeding port of the belt feeder is used as sealing air of a coal feeder; and the primary air or the secondary air sent into the bottom air inlet of the fly ash screening device is used for disturbing the fly ash material above the screen and intensifying the collision between fly ash material particles, so that the agglomeration of the fly ash material is avoided, the uniformity of the material flow is improved, and the effect of the screen separation is improved.

[0032] (3) The application provides a method and system for reducing the carbon content of fly ash of a circulating fluidized bed boiler, and the fly ash in a coarse ash bin is preliminarily separated and screened through coarse and fine screens in a fly ash screening device, so that the glass phase and the crystalline phase with relatively large density in the fly ash are separated out, and the particles with relatively large volume are settled on the upper coarse screen, and the particles with relatively small volume are settled on the lower fine screen, so that the function of the screen hole air supply channel and the load bearing of the screen is fully utilized, and the air inlet at the bottom of the fly ash screening device is prevented from being blocked by carbon particles.

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

[0034] Figure 1 It is a structural schematic diagram of the fly ash screening device of the embodiment of the application.

[0035] Figure 2 It is a structural schematic diagram of the short cone cyclone separation chamber of the embodiment of the application.

[0036] Figure 3 It is a short cone size diagram of the short cone cyclone separation chamber in the embodiment of the application.

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

[0038] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0039] Embodiment 1

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

[0041] In combination Figures 1-2 As shown in the accompanying drawings, the embodiment of the present application provides a method for reducing the carbon content of fly ash of a circulating fluidized bed boiler, and the method comprises the following steps:

[0042] Step S1: The ash in the coarse ash bin is sent into the fly ash sorting device 4 through the belt feeder 1 for preliminary settling and screening, and the primary air or the secondary air of the fluidized bed boiler is respectively sent into the feeding port of the belt feeder 1 and the bottom air inlet of the fly ash sorting device 4.

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

[0044] The coarse screen layer 2 and the fine screen layer 3 are arranged inside the fly ash sorting device 4 from top to bottom, and are used for preliminary settling and screening of the fly ash through density screening.

[0045] Because the main components of the fly ash are composed of three types of minerals, i.e., glass phase, amorphous phase and crystalline phase, the glass phase is mainly composed of floating beads, microbeads and magnetic beads, etc.; the amorphous phase is mainly composed of unburned carbon particles; and the crystalline phase is mainly composed of mullite, quartz sand, magnetite, hematite and periclase, etc. Most of the unburned carbon in the fly ash exists in the form of monomer, and the carbon particles in the amorphous phase are in the form of sponge and honeycomb; 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 primary air or the secondary air below the screen is used to first separate the carbon particles in the glass phase and the crystalline phase, and the coarse screen layer 2 is used to receive the carbon particles with a larger volume, and the fine screen layer 3 is used to receive the carbon particles with a smaller volume, so as to fully utilize the function of the screen hole air conveying channel and the function of bearing heavy objects of the screen, and avoid the carbon particles from blocking the air inlet at the bottom of the fly ash sorting device 4.

[0046] Considering the particle size of the fly ash and the resistance of the screen hole to the conveying air, the coarse screen layer 2 is selected to be a bed layer with a 200-250 μm hole screen, and the fine screen layer 3 is selected to be a bed layer with a 180-200 μm hole screen, and meanwhile, the coarse screen layer 2 and the fine screen layer 3 are both located below the ash inlet of the fly ash sorting device 4.

[0047] Step S2: The fly ash after the preliminary settling and screening of the fly ash sorting device 4 is sent into the short-cone cyclone separation chamber 5 for cyclone separation.

[0048] The short-cone cyclone separation chamber 5 is an effective dust collection device for accelerating the sedimentation of solid particles in the dust-containing air flow and intensifying the separation process by using a centrifugal force field, and the separation process is completed under the action of the centrifugal force field.

[0049] Under the action of the centrifugal force field, the separated materials are orderly distributed along the radial direction and the axial direction according to the particle size and the density, and the basic distribution law is that the particle size and the density gradually increase from the axial center of the separation chamber along the radial direction to the wall and from top to bottom along the longitudinal direction.

[0050] The greater the cone angle of the cone body part of the short-cone cyclone separation chamber 5, the more obvious the tendency of separating fly ash according to the density. This is because the purpose of the short-cone cyclone separation chamber 5 is to separate carbon in the fly ash, so the cone body part of the conventional cyclone separator is modified by increasing the cone angle and shortening the length of the cone body by referring to the structural characteristics of the short-cone cyclone used in ore dressing.

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

[0052] Step S3: After being separated by the short-cone cyclone separation chamber 5, the unburned carbon particles separated out flow out from the bottom of the short-cone cyclone separation chamber 5 into the carbon-rich dust collection bin 6 for enrichment, and the remaining unenriched fine fly ash is sent to the fine dust bin through the inner cylinder of the short-cone cyclone separation chamber 5.

[0053] The carbon particles enriched in the carbon-rich dust collection bin 6 are carbon-rich dust with high carbon content, which can be directly connected to the furnace by a return pipe for combustion, or sent to the coal bin for temporary storage.

[0054] Embodiment 2

[0055] In combination with Figures 1-2 The embodiment of the present application provides a system for reducing the carbon content of fly ash of a circulating fluidized bed boiler, which is used to implement the method in Embodiment 1.

[0056] The system comprises a coarse dust bin, a belt feeder 1, a fly ash sorting device 4, a short-cone cyclone separation chamber 5 and a carbon-rich dust collection bin 6 connected in sequence; and the primary air or the secondary air pipe of the circulating fluidized bed boiler is connected to the feed inlet of the belt feeder 1 and the bottom air inlet of the fly ash sorting device 4, respectively.

[0057] The primary air or secondary air sent into the inlet of the belt feeder 1 is used as sealing air of the coal feeder; the primary air or secondary air sent into the bottom air inlet of the fly ash sorting device 4 is used to disturb the fly ash material above the screen and intensify the collision between the fly ash material particles, so as to avoid the agglomeration of the fly ash material and improve the uniformity of the material flow and the effect of the screen separation.

[0058] The fly ash in the fly ash storage is sent into the fly ash sorting device 4 through the belt feeder 1 and then is subjected to the screen separation in the fly ash sorting device 4.

[0059] Specifically, the coarse screen layer 2 and the fine screen layer 3 are arranged in the fly ash sorting device 4 from top to bottom, which are used to preliminarily separate the fly ash by density screening.

[0060] Because the main components of the fly ash are composed of three kinds of minerals, i.e. glass phase, amorphous phase and crystalline phase, wherein the glass phase is mainly composed of floating beads, microbeads and magnetic beads; the amorphous phase is mainly composed of unburned carbon particles; and the crystalline phase is mainly composed of mullite, quartz sand, magnetite, hematite and periclase. Most of the unburned carbon in the fly ash exists in the form of monomer, and the amorphous phase carbon particles are in the form of sponge and honeycomb; the density of the components of the glass phase and the crystalline phase is far greater than that of the amorphous phase carbon particles, so the fly ash is first separated by the primary air or secondary air under the screen, the carbon particles of the glass phase and the crystalline phase are separated and settled, the coarse screen layer 2 is used to receive the carbon particles with large volume, and the fine screen layer 3 is used to receive the carbon particles with small volume, so as to fully utilize the function of the screen hole air channel and the function of bearing heavy objects of the screen, and avoid the carbon particles from blocking the air inlet at the bottom of the fly ash sorting device 4.

[0061] Considering the particle size of the fly ash and the resistance of the screen hole to the conveying air, the coarse screen layer 2 is selected to be a bed layer with 200-250 μm hole screen, and the fine screen layer 3 is selected to be a bed layer with 180-200 μm hole screen; meanwhile, the coarse screen layer 2 and the fine screen layer 3 are both located below the fly ash inlet of the fly ash sorting device 4.

[0062] After the preliminary screen separation in the fly ash sorting device 4, the fly ash enters the short cone cyclone separation chamber 5 for cyclone separation.

[0063] The short cone cyclone separation chamber 5 is an effective separation and collection device for accelerating the settlement of solid particles in the dust-containing air flow and intensifying the separation process by using the centrifugal force field. The separation process is completed under the action of the centrifugal force field. The separated material is orderly distributed along the radial direction and the axial direction according to the particle size and the density, and the basic distribution law is that the material gradually increases from the axial center of the separation chamber to the wall and from top to bottom.

[0064] The greater the taper angle of the frustum portion of the short-cone cyclone separation chamber 5, the more obvious the tendency of separating fly ash by density. This is because, considering that the purpose of the short-cone cyclone separation chamber 5 is to separate carbon in the fly ash, the taper angle of the frustum portion of the conventional cyclone separator is increased and the length of the frustum portion is shortened by referring to the structural features of the short-cone cyclone used in ore dressing.

[0065] Therefore, as shown in the drawings, the taper angle of the frustum portion of the short-cone cyclone separation chamber 5 in the embodiment of the present application is 120-140°, preferably 130°; and the height of the frustum portion is shortened to 1 / 3-1 / 2 of the original height H, preferably 1 / 2H, which is a short-cone cyclone. Figure 3

[0066] After being separated by the short-cone cyclone separation chamber 5, the unburned carbon particles separated are discharged from the bottom of the short-cone cyclone separation chamber 5 into the carbon-rich ash collection bin 6, and the remaining extremely fine fly ash that is not enriched is sent to the fine ash bin through the inner cylinder of the short-cone cyclone separation chamber 5.

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

[0068] The above only describes the embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the scope of the present application should be included in the protection scope of the present application.​

Claims

1. A method of reducing the carbon content of fly ash from a circulating fluidized bed boiler, characterized in that, The method comprises the following steps: Step S1: the ash in the coarse ash bin is sent into the fly ash sorting device through the belt feeder for preliminary settling screening, and the primary air or the secondary air is respectively sent into the feeding port of the belt feeder and the bottom air inlet of the fly ash sorting device; Step S2: the fly ash after the preliminary settling screening in the fly ash sorting device is sent into the short-cone cyclone separation chamber for cyclone separation; Step S3: the unburned carbon particles obtained through the cyclone separation flow out from the bottom of the short-cone cyclone separation chamber into the carbon-rich ash collection bin for enrichment, and the remaining fly ash that is not enriched is sent to the fine ash bin through the inner cylinder of the short-cone cyclone separation chamber.

2. The method of claim 1, wherein, The fly ash sorting device is internally provided with a coarse screen layer and a fine screen layer from top to bottom.

3. The method of claim 2, wherein, The coarse screen layer is selected to have a 200-250 μm aperture screen as a bed layer, and the fine screen layer is selected to have a 180-200 μm aperture screen as a bed layer.

4. The method of claim 2 or 3, wherein, Both the coarse screen layer and the fine screen layer are located below the ash inlet of the fly ash sorting device.

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

6. The method of claim 1, wherein, In step S3, the carbon particles enriched in the carbon-rich ash collection bin are directly connected to the furnace for back-furnace combustion through a back-connection pipeline, or are sent into a coal bin for temporary storage.

7. A system for reducing the carbon content of fly ash from a circulating fluidized bed boiler, characterized in that, The system comprises a coarse ash bin, a belt feeder, a fly ash sorting device, a short-cone cyclone separation chamber and a carbon-rich ash collection bin connected in sequence, and the primary air or the secondary air pipeline of the circulating fluidized bed boiler is respectively connected to the feeding port of the belt feeder and the bottom air inlet of the fly ash sorting device. The ash in the coarse ash bin is sent into the fly ash sorting device through the belt feeder for preliminary settling screening, and the fly ash after the preliminary settling screening is sent into the short-cone cyclone separation chamber for cyclone separation; the carbon particles obtained through the cyclone separation flow out from the bottom of the short-cone cyclone separation chamber into the carbon-rich ash collection bin, and the remaining fly ash that is not enriched is sent to the fine ash bin through the inner cylinder of the short-cone cyclone separation chamber.

8. The system of claim 7, wherein, The fly ash sorting device is internally provided with a coarse screen layer and a fine screen layer from top to bottom.

9. The system of claim 8, wherein, The coarse screen layer is selected to have a 200-250 μm aperture screen as a bed layer, and the fine screen layer is selected to have a 180-200 μm aperture screen as a bed layer.

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

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

12. The system of claim 7, wherein, The carbon particles enriched in the carbon-rich ash collection bin are directly connected to the furnace for back-furnace combustion through a back-connection pipeline, or are sent into a coal bin for temporary storage.

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