Circulating fluidized bed boiler combustion system with cyclone separator adjustable in separation efficiency

Abstract

The circulating fluidized bed boiler combustion system comprises a hearth, the cyclone separator, separator vertical pipes and a mixed air supply system, the mixed air supply system comprises a mixed air pipe, a primary air pipeline, a recirculating flue gas pipeline, vertical pipe spray pipes and a mixed air pipe header pipe, the vertical pipe spray pipes are distributed on the mixed air pipe, and the separator vertical pipes are distributed on the mixed air pipe header pipe. The spraying end of the vertical pipe spraying pipe is communicated with the separator vertical pipe, the recirculating flue gas pipeline is communicated with a tail flue outlet and a mixed air pipe header pipe, the tail end of the mixed air pipe header pipe is communicated with a mixed air pipe, and the primary air pipeline is communicated with the mixed air pipe header pipe; and a mixed air supply main valve, a primary air valve and a recirculating flue gas valve are respectively arranged on the mixed air main pipe, the primary air pipeline and the recirculating flue gas pipeline. The efficiency of the separator can be adjusted according to the actual combustion working condition, so that the hearth temperature is guaranteed, and the carbon content of bottom slag is controlled. And meanwhile, a good effect is also achieved on flame-retardant particle combustion enhancement and high alkali metal fuel coking inhibition.

Description

Technical Field

[0001] The invention relates to the technical field of circulating fluidized bed boiler combustion control, and in particular to a circulating fluidized bed boiler combustion system with adjustable separation efficiency of a cyclone separator. Background Art

[0002] As a core technology for the decarbonization of coal-fired power plants, circulating fluidized bed boilers (CFBs) are accelerating the transition from single coal to diversified fuels, leveraging their wide fuel adaptability and low pollutant control costs. These include expanding from traditional coal to low-carbon / zero-carbon fuels such as biomass, ammonia, and hydrogen, and gradually covering ultra-low calorific value fuels such as coal gangue, petroleum coke, sludge, papermaking waste, and industrial waste gas. However, fuel diversification poses complex challenges to the combustion stability and equipment adaptability of CFB boilers, the most significant of which is the unadjustable efficiency of the cyclone separator. A detailed analysis is provided below: 1. When burning high-ash / difficult-to-burn fuels (such as anthracite and petroleum coke), the cyclone separator is required to have a high separation efficiency. However, too high a separation efficiency will lead to excessive circulating ash, which will reduce the furnace temperature, increase the carbon content of the bottom ash, and reduce the thermal efficiency of the boiler. 2. When burning low-ash fuel, low separator efficiency will lead to insufficient circulating ash, causing excessively high furnace temperature, coking risks, and difficulty in carrying load; 3. When burning high-alkali metal fuels (such as straw and rice husks), excessive oxygen content in the separator may cause reburning of the material, which may easily cause coking of the separator and even the downstream return device, inducing the risk of shutdown.

[0003] In response to the above problems, there is an urgent need for an innovative technology that can dynamically control the efficiency of the separator. Summary of the Invention

[0004] To address the aforementioned technical issues, the present invention designs a circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency. This system achieves controllable adjustment of separation efficiency by installing a mixed air supply system in the separator riser. Furthermore, the present invention considers and mitigates the risk of reburning and coking in the separator caused by air supply to high-alkali metal fuels (such as straw and rice husks).

[0005] The present invention adopts the following technical solutions: A circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency comprises a furnace, a cyclone separator and a tail flue, a separator riser is arranged at the bottom of the cyclone separator, and the bottom of the separator riser is connected to the furnace through a pipeline, a mixed air supply system is arranged between the cyclone separator and the separator riser, and the mixed air supply system comprises a mixing air duct, a primary air duct, a recycled flue gas duct, a riser nozzle and a mixing air duct main pipe, a plurality of riser nozzles are distributed on the mixing air duct along the circumference, the injection end of the riser nozzle is connected to the separator riser along the circumference, the recycled flue gas duct is connected to the tail flue outlet and the mixing air duct main pipe, the end of the mixing air duct main pipe is connected to the mixing air duct, one end of the primary air duct is connected to the primary air, and the other end is connected to the mixing air duct main pipe, and the mixing air duct main pipe, the primary air duct and the recycled flue gas duct are respectively provided with a mixed air supply main valve, a primary air valve and a recycled flue gas valve.

[0006] Preferably, an oxygen content detector is installed on the main mixed air duct. In the mixed air supply system, the mixed air is formed by mixing the primary air and the recycled flue gas, and the oxygen concentration can be controlled.

[0007] Preferably, an air preheater is installed on the primary air duct, and the primary air comes from the hot primary air after heat exchange in the air preheater.

[0008] Preferably, the main valve, primary air valve and recirculating flue gas valve of the mixed air supply system are regulating valves.

[0009] Preferably, the plurality of riser nozzles are evenly distributed on the mixing air duct along the circumference, the injection ends of the riser nozzles are evenly connected to the separator riser along the circumference, the angle at which the riser nozzles spray into the separator riser is cut obliquely upward, and the extension line thereof does not interfere with the inner wall of the separator riser and can ensure that the airflow is smoothly injected into the bottom cone of the separator.

[0010] Preferably, a flue gas circulation fan is installed on the recirculating flue gas duct.

[0011] Preferably, the primary air is connected to the bottom of the furnace through a primary air duct.

[0012] Preferably, the tail flue outlet is connected to a chimney. The recycled flue gas comes from the low-temperature and low-oxygen flue gas at the tail outlet of the boiler.

[0013] The beneficial effects of the present invention are as follows: (1) the present invention dynamically adjusts the separator efficiency and oxygen concentration by coordinating the mixed air ratio with the opening of the mixed air system main valve, primary air valve, and recirculating flue gas valve of the mixed air supply system, thereby achieving a wide range of matching between oxygen concentration and separation efficiency, and keeping the cyclone separator efficiency within a reasonable range compatible with different fuels; (2) the present invention can not only regulate the separation efficiency of the separator, but also achieve the combustion enhancement of the flame-retardant particles and the coking suppression of the high-alkali metal fuel, so that the boiler can burn a variety of fuels. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the present invention; Figure 2 yes Figure 1 A magnified view of the partial view of M in the middle; Figure 3 yes Figure 2 Cross-sectional view in the AA direction; In the figure: 100, furnace, 200, cyclone separator, 300, separator riser, 400, mixed air supply system, 401, mixed air duct, 402, primary air duct, 403, recirculating flue gas duct, 404, riser nozzle, 405, mixed air supply main valve, 406, primary air valve, 407, recirculating flue gas valve. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: Figure 1-Figure 3 As shown, a circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency includes a furnace 100, a cyclone separator 200 and a tail flue. A separator riser 300 is provided at the bottom of the cyclone separator. The bottom of the separator riser is connected to the furnace through a pipe. A mixed air supply system 400 is arranged between the cyclone separator and the separator riser. The mixed air supply system includes a mixing air duct 401, a primary air duct 402, a recirculating flue gas duct 403, a riser nozzle 404 and a mixing air duct. Main pipe, several riser nozzles are distributed on the mixing air duct along the circumference, the injection ends of the riser nozzles are connected to the separator riser along the circumference, the recycled flue gas duct is connected to the tail flue outlet and the mixing air duct main pipe, the end of the mixing air duct main pipe is connected to the mixing air duct, one end of the primary air duct is connected to the primary air, and the other end is connected to the mixing air duct main pipe. The mixing air supply main valve 405, the primary air valve 406 and the recycled flue gas valve 407 are respectively provided on the mixing air duct main pipe, the primary air duct and the recycled flue gas duct.

[0016] An oxygen content detector is installed on the main mixed air duct. An air preheater is installed on the primary air duct. Regulating valves are used as the main valve of the mixed air supply system, the primary air valve, and the recirculating flue gas valve.

[0017] Several riser nozzles are evenly distributed around the mixing air duct. Their nozzle tips connect to the separator riser evenly along the circumference. The nozzles inject into the separator riser at an angled angle upward, ensuring that their extension lines do not interfere with the inner wall of the separator riser and ensure smooth airflow into the separator's bottom cone. A flue gas recirculation fan is installed in the recirculating flue gas duct. Primary air flows through the primary air duct to the furnace bottom. The tail flue outlet connects to the chimney.

[0018] When using the present invention, when burning high-ash fuels, the mixed air supply system 400 is activated. Based on the combustion temperature of the furnace 100, the opening of the mixed air supply main valve 405 connected to the mixed air duct 401 is controlled to control the air supply volume. This, in turn, controls the separation efficiency of the separator 200 and adjusts the amount of circulating ash entering the separator riser 300 to ensure that the furnace temperature of the circulating fluidized bed boiler remains within a reasonable range. Simultaneously, the primary air valve 406 and the recirculated flue gas valve 407 are adjusted based on the alkali metal content of the fuel and the combustion difficulty of the coal type to adjust the oxygen supply and ensure complete and reasonable combustion. The specific adjustment method is as follows: When burning high-ash, high-alkali fuels, increase the opening of recirculated flue gas valve 407 and decrease the opening of primary air valve 406 to reduce oxygen content and prevent reburning of materials and coking. When burning high-ash, difficult-to-burn fuels, decrease the opening of recirculated flue gas valve 407 and increase the opening of primary air valve 406 to provide more oxygen, maintain the furnace temperature at 100°C, reburn fine materials, and reduce the carbon content of the bottom ash. When burning low-ash fuels, close the mixed air supply system.

[0019] By adopting the circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency, the boiler can adjust the separator efficiency according to actual combustion conditions, thereby maintaining furnace temperature and controlling the carbon content of bottom ash. The system also effectively enhances the combustion of difficult-to-burn particles and inhibits the coking of high-alkali metal fuels.

[0020] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency, comprising a furnace, a cyclone separator, and a tail flue, wherein a separator riser is provided at the bottom of the cyclone separator, and the bottom of the separator riser is connected to the furnace through a pipeline, wherein: A mixing air supply system is arranged between the cyclone separator and the separator riser, and the mixing air supply system includes a mixing air duct, a primary air duct, a recirculating flue gas duct, a riser nozzle and a mixing air duct main pipe. Several riser nozzles are distributed on the mixing air duct along the circumference, and the injection end of the riser nozzle is connected to the separator riser along the circumference. The recirculating flue gas duct is connected to the tail flue outlet and the mixing air duct main pipe. The end of the mixing air duct main pipe is connected to the mixing air duct. One end of the primary air duct is connected to the primary air, and the other end is connected to the mixing air duct main pipe. The mixing air supply main valve, the primary air valve and the recirculating flue gas valve are respectively provided on the mixing air duct main pipe, the primary air duct and the recirculating flue gas duct.

2. A circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: An oxygen content detector is installed on the mixed air duct main pipe.

3. A circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: An air preheater is installed on the primary air duct.

4. A circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: The main valve, primary air valve and recirculating flue gas valve of the mixed air supply system adopt regulating valves.

5. The circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: The plurality of riser nozzles are evenly distributed on the mixing air duct along the circumference, and the injection ends of the riser nozzles are evenly connected to the separator riser along the circumference. The angle at which the riser nozzles spray into the separator riser is cut obliquely upward, and the extension line thereof does not interfere with the inner wall of the separator riser and can ensure that the airflow is smoothly injected into the bottom cone of the separator.

6. A circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: A flue gas circulation fan is installed on the recirculating flue gas duct.

7. The circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: The primary air is connected to the bottom of the furnace through a primary air duct.

8. The circulating fluidized bed boiler combustion system with adjustable cyclone separation efficiency according to claim 1, characterized in that: The tail flue outlet is connected to the chimney.

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