Design and operation of a 10 kWth chemical-looping combustor for solid fuels – Testing with South African coal

This paper presents the results obtained for the operation of a 10 kWth chemical-looping combustor using a South African coal as the solid fuel and an oxygen carrier of ilmenite, a natural iron titanium oxide. A chemical-looping combustor for solid fuels was designed and built. It consists of two interconnected fluidized beds, an air reactor where the oxygen carrier is oxidized and a fuel reactor where the coal is gasified by steam and the syn-gases react with the oxygen carrier. A constant coal flow corresponding to a thermal power of 3.3 kW was introduced into the fuel reactor. The tests were conducted at temperatures above 850 °C and for a total test duration of 22 h. The particle integrity of ilmenite and the particle circulation between the two reactors were investigated and verified. The effects of particle circulation on coal conversion, gas conversion of the fuel reactor and carbon separation or CO2 capture between the air and fuel reactors were investigated. The actual CO2 capture ranged between 82.5% and 96% while the gas conversion from the fuel reactor was in the range 78–81%, based on measurements of unconverted CO and CH4.