Combustible Matter Conversion in an Oxy-fuel Circulating Fluidized-Bed (CFB) Environment

Studies on combustible matter conversion during oxy-fuel combustion in a circulating fluidized-bed (CFB) environment are presented. A CFB facility has been modified to be ready for operation in an oxy-fuel mode, which means an elevated partial pressure of oxygen in a gaseous atmosphere of O-2/CO2. The maximum thermal load of the unit is estimated at 0.1 MW, and the main dimensions of combustion chamber are as follows: a height of 5 m and an inner diameter of 0.1 m. Polish bituminous coal was burnt. The paper is focused on carbon and combustible sulfur behavior in a combustion chamber that runs under oxy-fuel CFB conditions. The analysis is based on sampling of in-furnace flue gases and calculations of carbon and sulfur conversion ratios. The effect of both oxygen fraction in O-2/CO2 mixtures and excess oxygen was studied. An increased concentration of CO2 visibly inhibits fuel conversion and does not affect SO2 formation. A higher excess oxygen accelerates burnout of combustible matter; however, the value of 1.15 seems to be sufficient with respect to efficient combustion. The described investigations are the first part of the core work scheduled in the project "Advanced Technologies for Energy Generation: Oxy-combustion Technology for PC and FBC Boilers with CO2 Capture".