A study of combustion characteristics of pulverised coal under MILD combustion conditions

Abstract

In this experimental work, a laboratory-scale recuperative furnace has been used to investigate the sustainability of Moderate or Intense Low Oxygen Dilution (MILD) combustion with pulverised coal. Low-rank and high volatile Kingston brown coal and high-rank and low volatile Bowen Basin black coal with particle size in the range of 38-180􀀀 μm were injected into the furnace using either CO2 or N2 as a carrier gas. Operating conditions for stable MILD combustion of pulverised coal have been identified and evidencing MILD condition is achievable without any additional pre-heating of the air. The O2 and CO emissions were measured in parallel with NO emission. A water cooled sampling probe was used to conduct in-furnace gas sampling. Measurements of in-furnace gas concentration of CO and NO and in-furnace temperatures are presented. It was found that a significant reduction of NO emission owing to the strong NO reburning reaction inside the furnace. These findings, together with the potentiality of MILD conditions for soot depression and destruction, open the possibility of using high rank black and low rank brown coal with this technology.