Chemical-Looping Combustion in a 100 kW Unit for Solid Fuels
Paper i proceeding, 2012
Chemical-looping combustion is a novel technology for combustion of fossil fuels. By using a circulating bed material to transfer oxygen to the fuel, a pure stream of CO2 can be obtained from the flue gas, undiluted by N2 from the air. The main advantage of this capture technology is that there is no direct efficiency loss in obtaining the CO2 in a separate stream. This study describes results from operation in a 100 kWth chemical-looping combustor for solid fuels. The oxygen carrier used was ilmenite, an iron-titanium oxide. Coal is fed directly into a loop seal, leading to the fuel reactor, through a set of screws. All parts of the unit are fluidized with steam, except for the air reactor, which is fluidized with air, and the loop seal with the fuel insertion, which is fluidized with nitrogen. All-in-all, the unit has eleven windboxes, of which four are loop seals. Three experiments have been conducted using a Colombian coal as fuel. Operation was stable and loss of char to the air reactor was small, meaning that the CO2 capture efficiency was high (>90%). Gas concentration measurements showed the presence of unconverted CO, H2 and CH4 corresponding to an oxygen demand of 18.5% at 950°C.