Double-circuit gasification and combustion system based on circulating fluidized bed and method and application thereof

Abstract

The invention discloses a double-circuit gasification and combustion system based on a circulating fluidized bed and a method and application thereof. The double-circuit gasification and combustion system comprises a gasifier, a primary separator, a heat exchanger, a secondary separator, a boiler and an ash bin, wherein the inlet of the primary separator communicates with the outlet of the gasifier; the gas outlet of the primary separator communicates with the heat medium inlet of the heat exchanger; the heat medium outlet of the heat exchanger communicates with the inlet of the secondary separator; gas subjected to primary separation is subjected to heat exchange for cooling in the heat exchanger; the gas outlet of the secondary separator communicates with the boiler; the solid outlet of the primary separator communicates with the inlet of a first material return valve; one side outlet of the first material return valve communicates with a first material return opening of the gasifier, and the other side outlet of the first material return valve communicates with the ash bin; the solid outlet of the secondary separator communicates with the inlet of a second material return valve; and one side outlet of the second material return valve communicates with a second material return opening of the gasifier, and the other side outlet of the second material return valve communicates with the ash bin.

Description

technical field [0001] The invention relates to the field of efficient and clean combustion, in particular to a circulating fluidized bed-based dual-loop gasification combustion system, method and application. Background technique [0002] Circulating fluidized bed gasifier has the characteristics of wide adaptability of raw materials and easy engineering scale-up. It has developed rapidly in my country and is widely used in the field of thermochemical conversion and energy utilization of coal and biomass solid waste. [0003] At present, the common biomass gasification and combustion system technology in engineering is: after the biomass raw material is gasified and burned in the circulating fluidized bed gasifier, the high-temperature gas produced carries a large number of particles through the cyclone separator for gas-solid separation. The high-temperature ash is captured and returned to the gasification furnace through the standpipe and the feeder, and the gas carries t...

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Problems solved by technology

[0004] However, due to the short residence time of the raw material particles in the furnace and the low temperature of the gasification furnace (generally lower than 900°C), the carbon content of the fly ash in the gasification gas is generally about 20%. The carbon content in some ash and fly ash can even be as high as 30% for biomass raw materials that are large or have different herbal and woody components. High carbon content in ash is one of the main reasons for the reduction of system efficiency

[0005] For example, for the industrial biomass of traditional Chinese medicine dregs, the raw materials of dregs produced by different types and different formulas are complex and diverse, and contain more wood fibers. The raw materials also need to be pulverized before gasification treatment, but considering the economics of project operation, The homogeneity of the material entering the gasifier is far inferior to that of pulverized coal

Therefore, the operating conditions of the multi-material mixed biomass raw material gasification system are more complicated, prone to uneven reaction and incomplete gasification, resulting in unstable system pressure and blockage of the return valve, thereby affecting the stability of the system run

[0006] As for the application mode of directly feeding into the boiler for combustion, due to the limited gas-solid separation efficiency of the cyclone separator, a considerable amount of fly ash is carried into the boiler combustion chamber during the gasification combustion, and the dust generated during long-term operation will inevitably stain the water wall. pollution and corrosion, affecting boiler heat transfer efficiency and safe operation

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