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CN-122015083-A - Fluidized bed combustion system and method

CN122015083ACN 122015083 ACN122015083 ACN 122015083ACN-122015083-A

Abstract

The invention provides a fluidized bed combustion system and a combustion method, wherein the fluidized bed combustion system comprises a fluidized bed combustion reaction device and a mild gasification reaction device, the fluidized bed combustion reaction device comprises a dilute phase zone arranged in the middle and a dense phase zone arranged at the lower part, a gas phase outlet of the mild gasification reaction device is connected with a gas phase inlet of the dilute phase zone, and a solid phase outlet of the mild gasification reaction device is connected with a solid phase inlet of the dense phase zone. The system has the advantages of stable combustion, high denitration efficiency, compact structure, simple and convenient operation and low running cost, is suitable for low-nitrogen transformation and new construction of coal and biomass combustion devices, and has good industrial application prospect and popularization value.

Inventors

  • LI SONGGENG
  • DING GUANGCHAO
  • LIU TAISHAN

Assignees

  • 中国科学院过程工程研究所

Dates

Publication Date
20260512
Application Date
20260323

Claims (10)

  1. 1. A fluidized bed combustion system, characterized in that the fluidized bed combustion system comprises a fluidized bed combustion reaction device and a mild gasification reaction device; the fluidized bed combustion reaction device comprises a dilute phase zone arranged in the middle part and a dense phase zone arranged in the lower part; the gas phase outlet of the mild gasification reaction device is connected with the gas phase inlet of the dilute phase zone, and the solid phase outlet of the mild gasification reaction device is connected with the solid phase inlet of the dense phase zone.
  2. 2. The fluidized bed combustion system of claim 1, wherein the fluidized bed combustion system comprises a supply air system; Preferably, the air supply system comprises an air supply system, an over-fire air system and a fluidization air system, wherein a gas outlet of the air supply system is connected with a material inlet of the mild gasification reaction device, a gas outlet of the over-fire air system is connected with an over-fire air inlet of the dilute phase zone, and a gas outlet of the fluidization air system is connected with a fluidization air inlet of the dense phase zone.
  3. 3. Fluidized bed combustion system according to claim 1 or 2, characterized in that the fluidized bed combustion reaction means comprise a circulating fluidized bed and/or a bubbling fluidized bed.
  4. 4. A fluidized bed combustion system according to any one of claims 1 to 3, wherein a gas-solid separation assembly is connected to the top of the dilute phase zone; Preferably, the top of the gas-solid separation assembly is provided with an exhaust port; preferably, the bottom of the gas-solid separation assembly is connected with a feed back leg, and the feed back leg is connected with the dense phase zone; preferably, a loosening air inlet is formed in the bottom of the feed back leg.
  5. 5. The fluidized bed combustion system according to any one of claims 1 to 4, wherein the mild gasification reaction device comprises a cyclone type mild gasification reaction device and/or a spiral type mild gasification reaction device; Preferably, the mild gasification reaction device may be arranged in 1 to 4 circumferential directions of the fluidized bed combustion reaction device.
  6. 6. A fluidized bed combustion method, characterized in that the fluidized bed combustion method is performed in the fluidized bed combustion system according to any one of claims 1 to 5.
  7. 7. The fluidized bed combustion method according to claim 6, characterized in that the fluidized bed combustion method comprises the steps of: The fuel and the auxiliary agent are mixed in proportion, enter the mild gasification reaction device and are combusted to generate semicoke and crude gas, the semicoke and the residual fuel enter the dense-phase zone through the solid-phase inlet, and the crude gas enters the dilute-phase zone through the gas-phase inlet and is mixed with flue gas generated by fluidized combustion in the dense-phase zone for further combustion.
  8. 8. The fluidized bed combustion method of claim 7, wherein the fuel comprises coal and/or biomass; Preferably, the auxiliary comprises an oxide or salt of at least one element of iron, calcium or aluminium.
  9. 9. The fluidized bed combustion method according to claim 7, wherein the mass ratio of fuel to auxiliary agent is not less than 10.
  10. 10. The fluidized bed combustion method according to claim 7, wherein the gas phase inlet of the dilute phase zone is disposed in a temperature range of 700-950 ℃ along a height direction of the fluidized bed combustion reaction apparatus.

Description

Fluidized bed combustion system and method Technical Field The invention relates to the technical field of solid fuel combustion and pollution control, in particular to a fluidized bed combustion system and a fluidized bed combustion method. Background The nitrogen oxides can cause environmental problems such as acid rain, photochemical smog, greenhouse effect and the like, and cause serious harm to the atmospheric environment and human health. The state has come out of strict regulatory measures, requiring that nitrogen oxides in important areas and industries reach ultra-low (50 mg/Nm 3). Solid fuels (e.g., coal, biomass) when combusted produce fuel-type and thermal-type nitrogen oxides. The fluidized bed combustion technology is characterized in that the combustion temperature is relatively low, fuel type nitrogen oxides are mainly used, and the control of the generation of the fuel nitrogen is key. In the prior art, various ideas are proposed by research and patents around staged conversion, zone combustion and pollutant cooperative control of solid fuels. For example, patent CN1203117a discloses a decoupling circulating fluidized bed combustion system based on a Circulating Fluidized Bed (CFB) and a desulfurization and denitration method thereof, which couple carbonization (or pyrolysis) of coal with a combustion process by using solids such as high-temperature circulating ash as a heat carrier, and reduce nitrogen oxides in flue gas by using pyrolysis gas. The device is developed based on traditional fuel coal, and pyrolysis is carried out on materials mainly through high-temperature circulating ash as a heat carrier, when working condition adjustment or fuel property change, system heat matching and material stay characteristics are easy to deviate, operation stability maintenance difficulty is high, and resistance exists in industrial large-scale application and popularization. The patent CN109539245B and the patent CN101158468B respectively disclose a pulverized coal pyrolysis decoupling combustion device and a pulverized coal high-temperature preheating method, and the core point is that pulverized coal is reburning after being preheated and modified at high temperature, so that the stability and low-nitrogen combustion of the pulverized coal can be realized. However, the device is mainly aimed at a pulverized coal furnace, and in addition, the problems of complex structure, reduced combustion efficiency and the like of a preheater exist. In addition, in the combustion process, fuel nitrogen is mainly released in the form of ammonia gas and hydrogen cyanide, and is a key intermediate for generating and reducing nitrogen oxides, so that the formation of the nitrogen oxides in the combustion process is directly determined. In paper "BAI Z, JIANG X Z, LUO K H. A reactive molecular dynamics study of NO removal by nitrogen-containing species in coal pyrolysis gas[J]. Proceedings of the Combustion Institute, 2023, 39(4): 4573-4581", ammonia reacts with NO under the condition of oxygen deficiency to mainly generate nitrogen and water, the byproduct N 2 O is very little, HCN easily generates NO and N 2 O in a low-temperature region (873-1200K), and NO generation is remarkably increased in a high-temperature region (> 1200K). In paper "WARGADALAM V J, LöFFLER G, WINTER F, et al. Homogeneous formation of NO and N2O from the oxidation of HCN and NH3 at 600-1000℃[J]. Combustion and Flame, 2000, 120(4): 465-478", when NH 3 and HCN coexist, NH 3 preferentially participates in the reduction reaction of NO, and HCN delays the reaction and is easy to generate N 2 O, so that the denitration effect is remarkably reduced, and reducing the generation amount of HCN and improving the NH 3/HCN ratio (ammonia-cyanide ratio) become key technical ways for strengthening gas phase reduction of nitrogen oxides by raw gas or pyrolysis gas. In view of the foregoing, there is a need for developing a high-efficiency low-nitrogen combustion system and a matching technical solution that are easy to implement in an engineering manner, and a clean and efficient low-nitrogen combustion technology is needed. Disclosure of Invention In view of the problems in the prior art, the invention provides a fluidized bed combustion system and a fluidized bed combustion method, which realize high-efficiency cooperative control of low nitrogen oxide emission while considering engineering feasibility and combustion stability, and are suitable for CFB and BFB furnace types and old boiler reconstruction applications. To achieve the purpose, the invention adopts the following technical scheme: In a first aspect, the present invention provides a fluidized bed combustion system comprising a fluidized bed combustion reaction apparatus and a mild gasification reaction apparatus; the fluidized bed combustion reaction device comprises a dilute phase zone arranged in the middle part and a dense phase zone arranged in the lower part; the gas phase outlet of th