The combustion of dry lignite under oxy-fuel process conditions in a 0.5 MWth test plant

For the testing of the oxy-fuel process, an 0.5 MWth test facility of the technical institute CEBra, Centre for Energy Technology Brandenburg e. V has been in operation within a two-year trial period in cooperation with VE-G and EVN AG. A stable operation under oxy-fuel condition with lignite and hard-coal could be demonstrated. During the operation a high CO2-concentration of 92 Vol.-% in the dry flue-gas could be achieved. Further a high influence of the variation of the oxygen distribution in front of the furnace on the formation of NOx was detected.By the usage of CaCO3 during the combustion a high reduction of SO2 could be achieved under Oxy-fuel conditions. The flue gas condenser has a stable operation without slagging. The moisture content of the flue gas was reduced to 3 Ma.-% and a high potential for SO2-removal by the condensing process was detected.The burning rate under Oxy-fuel conditions varies considerably from that of air combustion. Experimental results focused on the influence of gas composition to combustion time and combustion rate of the fuels are presented. They indicate that a substitution of nitrogen by CO2 in the gas composition yield a reduction of combustion time. High CO2-concentrations in the combustion gas affect the conditions of the chemical reaction complex so that the Boudouard-reaction becomes more important.