Influence of vent air valve opening on combustion characteristics of a down-fired pulverized-coal 300 MWe utility boiler

Industrial experiments have been performed on a down-fired pulverized-coal 300 MWe utility boiler with vent air valve opening of 100% and 40%. The gas temperature distribution along the primary air and coal mixture flow, gas temperature distribution in the furnace, and gas components such as O₂, CO, CO₂ and NO_x in the near-wall region were measured for the first time. The influence of vent air valve opening on coal combustion in the furnace was determined. The results indicate that ignition of the primary air and pulverized-coal mixture is delayed. The position of the gas temperature peak is above the arches. Emission of NO_x is up to 2101 mg/m³ (at 6% O₂ dry) with vent valve opening of 40%.