PRESSURIZED PULVERIZED FUEL COMBUSTION IN DIFFERENT CONCENTRATIONS OFOXYGEN AND CARBON-DIOXIDE

Theoretical and experimental studies showed that increasing gas pressu re at constant gas composition most strongly increases the combustion rate of less reactive coals, which are difficult to burn completely in atmospheric pulverized fuel boilers. The effect of pressure increase is greatest near 0.1 MPa and less at higher pressures. The limit at wh ich increase in pressure has an effect varies from coal to coal, depen ding on the particle size. With less reactive coals and small particle s, the effect can be seen at pressures greater than 1 MPa. The relativ e effect of pressure increases when the gas oxygen content is low, imp roving the burnout in furnaces. The effect of pressure is small for la rge particles and reactive fuels. At high pressures the rates of homog eneous and heterogeneous reactions increase raising the maximum partic le temperature; the higher temperature may increase the extent of devo latilization and further decrease the total combustion time. Combustio n rate and the temperature of burning coal particles were measured in experiments with a pressurized entrained flow reactor under the follow ing conditions: gas temperature 1073-1473 K, pressure 0.2-0.8 MPa, oxy gen partial pressure 0.025-0.1 MPa, and partial pressure of CO2 0.05-0 .2 MPa. Measured and calculated results showed increased carbon dioxid e concentration in the combustion environment to have an insignificant effect on the combustion rate in the studied temperature region, but it lowered the particle temperature to some extent, suggesting that th e gasification reaction CO2-C takes place as well. Calculations indica ted that in pressurized combustion the rate of gasification reaction i s greater at higher temperatures.