An experimental study of MILD combustion of pulverized coal in a recuperative furnace

Abstract

Moderate or Intense Low Oxygen Dilution (MILD) combustion technology has been identified as an innovative approach to reducing combustion generated pollutants and increasing thermal efficiency. The present experimental study investigates the performance and operation characteristics of a parallel jet MILD combustion furnace using pulverized coal as the fuel. Kingston brown coal and Bowen basin anthracite coal with particle size in the range of 38-180 μm was injected into the furnace using CO2 as a carrier gas. It was found that MILD conditions are achievable for coal particles without additional pre-heating of the air. Measurements of in-furnace combustion gas concentration of CO and NO, exhaust gas emissions, and furnace temperatures are presented. The in-furnace combustion data are analyzed to better understand the combustion characteristics of coal under the MILD condition in a recuperative furnace. High CO concentration was recorded at lower portion of the furnace for brown coal. It was also found that for the same equivalence ratio (φ = 0.88) the NO emission dropped to 45% for brown coal in comparison to that measured for anthracite coal.