Influence of Secondary Air Ratio on Gas-Solid Mixing and Combustion in a 300MWe CFB Boiler Furnace

This paper reports an experimental investigation on the influence of secondary air ratio (SAR) on gas-solid mixing and combustion, which carried out in a 300 MWe circulating fluidized bed boiler. The boiler furnace has a large width-depth ratio of 3.35 and 3 cyclones arranged asymmetrically. The parameters studied were temperature distribution of bed, flue-gas temperature, solid concentration and NOX emission. Results showed that temperature was not evenly distributed along the width of the furnace. The temperature of middle zone was 50~80°C higher than side zones. The temperature profiles became more uniform when SAR increased. Both average bed temperature and bed temperature deviation decreased with increment of secondary air. Moreover, average solid concentration of the furnace increased with increasing SAR. SAR had no distinct effect on average flue-gas temperature but temperature distribution of the 3 exits became more uniform when SAR increased. NOX emission was less than 160 mg/m³ during the test and decreased with increasing SAR.