Formation of Reductive and Corrosive Gases during Air-Staged Combustion of Blends of Anthracite/Sub-bituminous Coals

Abstract

Air-staged combustion of blended coals is now a common choice for coal-fired boilers in China as a primary method to control NOx emission. Reductive gases, CO and H2, and corrosive gases, H2S and COS, are generated in the fuel-rich zone which leads to problems of high temperature corrosion, slagging and fouling under a reducing atmosphere. This study focuses on the generation properties of reductive and corrosive gases during blended coals air-staged combustion. Experiments of anthracite, sub-bituminous, and their blends with different mixing ratios were conducted in a drop tube furnace. Generation characteristics of reductive gases, CO and H2, and corrosive gases, H2S and COS, in the fuel-rich zone were carefully studied at 1573 and 1673 K with different stoichiometric ratios in primary combustion zone. Blending effects on char burnout and NOx emission were also reported. It was found concentrations of CO and H2 increase obviously in the fuel-rich zone by blending sub-bituminous into anthracite due to th...