RESEARCH ON CO-COMBUSTION OF SEWAGE SLUDGE AND COAL IN OXY-FUEL CONDITIONS

Oxy-fuel co-combustion of municipal dried sewage sludge and coal was conducted to observe the combustion characteristics as well as pollutant emissions generated under different oxygen injection rate in oxy-fuel atmosphere in 0.1 MWt CFB reactor. As a feed gas a mixture of oxygen and carbon dioxide was used. Oxygen concentration in a feed gas varied from 21 % to 30 % per volume. The following blending ratios of sewage sludge to coal were chosen: 50 %, 30 % and 10 %. Flue gas components were on-line measured by a gas analyzer, determining CO2, CO, SO2, SO3, NO2, NO, N2O, NH3, HCN concentrations by non-dispersive infrared absorption. During the study the influence of oxygen concentration in the gas atmosphere and the mass fraction of sewage sludge in the fuel blend on the emission of sulfur and nitrogen compounds in the O-2/CO2 atmosphere with varied proportions of components in the blend were determined. It was found that oxygen concentration in the gas mixture has a significant influence on the process conditions. When the oxygen concentration in the gas mixture increased, the temperature of thermal processing of fuel blends was higher. The proportion of sewage sludge also affected the obtained profiles, which was particularly visible at 21 % oxygen content in the gas mixture. Then the conversion ratios of nitrogen and sulfur contained in blending fuel to NO, NO2, N2O, NH3, HCN, SO2, SO3 and H2S were determined. This paper reports some of the major findings obtained from these research activities.