System adopting high concentration CO2 flue gas as coal dust drying medium in boiler

Abstract

The invention relates to a system adopting a high concentration CO2 flue gas as a coal dust drying medium in a boiler and belongs to the technical field of energy technology application and CO2 capture. The flue gas which is dehydrated and heated to a certain temperature and contains over 95 percent of CO2 is used as the drying medium for coal dust pulverizing. The drying medium is an inert gas with low oxygen content so as to solve the problem of easy explosion of a coal pulverizing system when hot air is used as the drying medium and improve the operational safety of the coal pulverizing system. Meanwhile, compared with the temperature of the hot air, the initial temperature of the drying medium can be greatly improved so as to reduce the power consumption of a coal mill, improve the fineness of coal dust, improve combustion efficiency, reduce the exhaust gas temperature and improve the heat efficiency of the boiler.

Description

technical field [0001] The invention belongs to energy technology application and CO 2 The field of capture technology, in particular to a CO 2 The flue gas with a content of more than 95% is used as a system for the drying medium of pulverized coal. Background technique [0002] Traditional pulverized coal-fired power plant boilers generally use hot air as the medium for drying and grinding raw coal to pulverized coal. After being preheated by the air preheater, a part of the cold air passing through the blower enters the pulverizing system for drying and carrying pulverized coal, and the other part is directly sent into the furnace as secondary air to ensure the complete combustion of the pulverized coal. Since the oxygen content of the hot air is 21%, the dried pulverized coal-air mixture is in danger of explosion, and the outlet temperature of the coal mill must be controlled to be lower than the explosion limit temperature, so that the temperature of the hot air fed i...

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Problems solved by technology

Since the oxygen content of the hot air is 21%, the dried pulverized coal-air mixture has the risk of explosion, and the outlet temperature of the coal mill must be controlled below the explosion limit temperature, so that the temperature of the hot air fed into the coal mill is limited, generally Therefore, on the one hand, the drying efficiency of the coal mill is affected; on the other hand, when the moisture content of the raw coal changes, in order to adapt to the limitation of the outlet temperature of the coal mill, some cold air must be mixed in, which displaces the air preheater The hot air flow rate reduces the heat recovery of flue gas at the tail of the boiler and reduces the thermal efficiency of the boiler

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