Search

Abstract: Combustion experiments of two Chinese coals were conducted in a 50kWth circulating fluidized bed (CFB) combustor in air and O2/CO2 atmospheres, and the effects of atmosphere and O2 staging on combustion characteristics including temperature distribution profiles, combustion efficiency, gaseous pollutant emission and desulfurization efficiency were investigated. Results show that O2 enrichment in the atmosphere elevates the temperature level in the riser and improves the combustion efficiency. Without limestone addition, O2 enrichment in the atmosphere augments SO2 and NO emission and reduces CO emission. The desulfurization efficiency under higher O2 concentration is higher with the same Ca/S molar ratio in O2/CO2 atmosphere. O2 staging provides more operation flexibility for oxy-fuel CFB combustion. As O2 concentration in the primary gas increases, combustion efficiency and desulfurization efficiency are improved. O2 staging can reduce the NO emission to a large extent in O2/CO2 atmosphere. [Copyright &y& Elsevier]

Abstract: Oxy-fuel Circulating Fluidized Bed (CFB) combustion technology, a very promising technology for CO2 capture, combines many advantages of oxy-fuel and CFB technologies. Experiments were carried out in a 50kWth CFB facility to investigate how operation parameters influence the NO emission in O2/CO2 atmospheres. The simulated O2/CO2 atmospheres were used without recycling the flue gas. Results show that NO emission in 21% O2/79% CO2 atmosphere is lower than that in air atmosphere because of lower temperature and higher char and CO concentrations in the dense bed. Elevating O2 concentration from 21% to 40% in O2/CO2 atmosphere enhances fuel-N conversion to NO. Increasing bed temperature or oxygen/fuel stoichiometric ratio brings higher NO emission in O2/CO2 atmosphere, which is consistent with the results in air-fired CFB combustion. As primary stream fraction increases, NO emission increases more rapidly in O2/CO2 atmosphere than that in air atmosphere. Stream staging is more efficient for controlling NO emission in oxy-CFB combustion than that in air combustion. Oxygen staging provides an efficient way to reduce NO emission in oxy-CFB combustion without influencing the hydrodynamic characteristic in the riser. [ABSTRACT FROM AUTHOR]