Combustion method capable of reducing nitrogen oxide discharge of circulating fluidized bed

Abstract

A combustion method capable of reducing nitrogen oxide discharge of a circulating fluidized bed comprises the following steps: a combustion device provided; fuel and combustion air, the amount of which is higher than theoretical combustion air amount and lower than conventional combustion air amount is introduced into a combustion chamber of the circulating fluidized bed, so that atmosphere in the combustion chamber of the circulating fluidized bed is kept to be reducing atmosphere; gas-solid mixtures generated by the combustion chamber of the circulating fluidized bed are enabled to enter a cyclone separator, most particles in the gas-solid mixtures are separated and returned to the combustion chamber of the circulating fluidized bed again through a back-feeder, flue gas in the gas-solid mixtures flows into a tail flue through a center cylinder and an outlet flue; and afterflaming air is introduced into the center cylinder and / or the outlet flue, so that carbon monoxide and other combustible components in the flue gas are combusted completely. By adopting the method provided by the invention, the emission concentration of nitrogen oxide in the flue gas can be reduced, and meanwhile, the combustion efficiency of the circulating fluidized bed combustion device is ensured.

Description

technical field [0001] Embodiments of the present invention relate to a combustion method of a circulating fluidized bed, in particular, to a combustion method for reducing the emission of nitrogen oxides in a circulating fluidized bed. Background technique [0002] Nitrogen oxides (NOx) are one of the main pollutants of air pollution, and excessive nitrogen oxides cause serious ecological and environmental problems. Coal-fired boilers produce a large amount of nitrogen oxide gas, therefore, it is very important to control the emission of nitrogen oxides from coal-fired boilers in thermal power plants. For example, in relevant regulations, it is required that new boilers must implement 100mg / Nm 3 emission standards, while the original nitrogen oxide emission concentration of circulating fluidized bed boilers cannot directly meet the standards. Therefore, circulating fluidized bed boilers are faced with the need to further reduce the emission of nitrogen oxides. [0003] I...

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Problems solved by technology

[0005] Chinese patent application 201310723729.7 proposes a combustion method for circulating fluidized bed boilers with low nitrogen oxide emissions, which reduces nitrogen oxide emissions through staged combustion of air in the furnace and increases the distance between the three layers of secondary air, but Excessive secondary air will affect the fluidization of materials in the furnace, reduce the circulation volume, and shorten the residence time of fuel in the furnace, which is not conducive to the full combustion of fuel and affects the combustion efficiency of the boiler

Chinese patent application 201310592710.3 proposes a device and method for reducing nitrogen oxides in flue gas products of circulating fluidized bed boilers. The flue gas recirculation technology is used for the primary air and secondary air of circulating fluidized bed boilers at the same time to reduce the ignition area Oxygen concentration, thereby inhibiting the formation of nitrogen oxides; but this method increases the flue gas flow rate in the circulating fluidized bed furnace, which will aggravate the wear of the heating surface in the furnace, and at the same time, the reduction of oxygen concentration will also cause the combustion share in the dense phase zone Decrease, carbon content in ash slag increases, affect boiler combustion efficiency

Although these technologies have played a certain role in controlling the nitrogen oxide emission of circulating fluidized bed boilers, the degree of control of nitrogen oxide generation is limited. In general, it is difficult to achieve a circulating fluidized bed boiler nitrogen oxide emission of less than 100mg / Nm 3 requirements, and will adversely affect the efficient operation of the boiler

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