Investigation of NOx Emissions for Superfine Pulverized Coal in Air-Staging Combustion

Superfine pulverized coal combustion is a new pulverized coal combustion technology that has better combustion stability, higher combustion efficiency, and comprehensive cost-effective operation. The novelty of this present paper is that fundamental experiments on an electrically heated drop-tube furnace were carried out to understand the NOx emissions of air-staging combustion for two superfine pulverized bituminous coals used in China for the first time. The results indicate that high-volatile-containing Neimenggu (NMG) coal possesses better effectiveness of NOx abatement than low-volatile-containing Shenhua (SH) coal. Interesting saddle-point effects of the highest NOx emissions have been found for both coals around the average particle size of 17.44 mu m for SH coal and similar to 30 mu m for NMG coal. For different stoichiometric ratios and positions of over fire air (OFA) ports, NMG coal provides a higher ability of deNO(x) efficiency than SH coal. The superfine pulverized coal combustion of the NMG_25.86 mu m particle can even reach the highest deNO(x) efficiency up to 70%. The findings of this paper will provide guidance for further studies on the NOx emission characteristics of superfine pulverized coal combustion.