A low-NOx co-combustion system and method for power plant boilers with high-temperature flue gas preheating semi-coke

Abstract

The invention relates to a low NOx hybrid combustion system and method for preheating semi-coke by high-temperature flue gas of a power station boiler. According to the hybrid combustion system and method, a preheating pipeline and a cyclone preheating separator are adopted, the semi-coke is directly preheated through the high-temperature flue gas, so that the temperature of the semi-coke sprayedinto a hearth is remarkably improved; meanwhile, a stable ignition region for combustion of bituminous coal is arranged at the lower part of the hearth, so that ignition and flame stabilization of combustion of ultra-low volatile semi-coke fuel are facilitated, and the large proportion (larger than or equal to 45%) blending combustion of the semi-coke fuel of the power station boiler is achieved;a preheating product with the relatively strong reducibility is produced while the semi-coke is preheated, the preheating product is directly sprayed into the middle part of the hearth through a combustor, a NOx reduction zone is formed on the upper part of a preheating semi-coke combustion zone, so that emission of NOx is greatly reduced, and low NOx combustion of ultra-low volatile carbon-basedfuel is effectively realized; and air or pure oxygen over fire air is injected into the upper part of a combustion region of the hearth so that the fuel can be completely combusted, and the carbon content of the fly ash and the NOx emission can be effectively reduced.

Description

technical field [0001] The invention relates to a co-combustion system and method for a power plant boiler, in particular to a low NO power plant boiler with high-temperature flue gas preheating semi-coke x Co-combustion systems and methods. Background technique [0002] Cascade utilization of coal is one of the important ways of clean and efficient utilization of coal. The by-products of coal pyrolysis and gasification, semi-coke and residual carbon, are burned as high-grade clean fuels to generate electricity, which is an important part of realizing clean and efficient cascade utilization of coal. Semi-coke is a low volatile solid carbon product obtained by dry distillation and pyrolysis of non-caking or weakly caking high-volatile bituminous coal under medium and low temperature conditions. my country's low-rank coal reserves are close to 500 billion tons, accounting for about 42% of the proven coal reserves. This is a type of coal with a low degree of coalification. T...

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Problems solved by technology

In 2014, Xi’an Thermal Engineering Institute realized the safe and stable blending of 33% semi-coal on the pulverized coal boiler of Yinhe Power Plant’s 135MW unit for the first time in China, and in 2015 on the lean coal boiler of Shenwan Energy’s Chizhou Power Plant’s 2×320MW unit In order to safely and stably burn 30% semi-coke, but found that the efficiency of the boiler has decreased

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