Dynamic Characteristics of a Boiler with Low-NOX Combustion

Abstract

Due to the strictest nitric oxide (NOx) emission limit in the world, a large number of thermal power plants in China have reformed their pulverized coal (PC) boilers with the 3rd generation low-NOx combustion technology which integrates bias combustion burners with separated over fire air (SOFA) nozzles. The 3rd generation low-NOx combustion technology effectively reduces the NOx concentration in flue gas at furnace outlet, from more than 350 mg/m3 to 100–150 mg/m3 in steady states when burning bituminous coal. However, as the utilization of the 3rd generation low-NOx combustion technology, the dynamic process of PC boiler becomes extremely slower than it used to be, on the countrary to the demands of power grid, who expects that the coal fired power plant changes its power load as rapidly as possible. In order to accelerate load changing rate in PC boilers with the 3rd generation low-NOx combustion technology, operating optimization tests, including combustion optimizations in steady states and study on dynamic characteristics during load changing processes, were conducted on a 600 MW commercial boiler. The former works reduce NOx concentration, from 130 to 100 mg/m3, in flue gas at furnace outlet. In addition, the latter works accelerate boiler load changing rate from 1% ECR to 2% ECR, narrowing down the range of steam temperature fluctuation. All these works not only enhance the security of boiler and turbine, but also speed up power load changing process, especially benifit to the flexibility of coal-fired thermal power plant.