Abstract
In this work, woody biomass is converted by chemical looping combustion (CLC) in the auto-thermally operated 150-kW pilot unit at SINTEF Energy Research in Norway, using ilmenite as an oxygen carrier. The pilot unit consists of two inter-connected circulating fluidized bed reactors, being the air and fuel reactor, respectively. The unit is simplified compared to many other lab and pilot units by not having a carbon stripper. The aim of the present study is to evaluate the main performance parameters when operating a relatively large CLC unit in auto-thermal mode, using a cheap natural mineral, ilmenite, as oxygen carrier. Another aspect with the tests is to verify if the omission of a carbon stripper can provide high enough capture efficiencies for solid fuels as biomass, with a large share of volatiles and a char remnant with high reactivity. As a comparison, tests with petcoke were performed, to assess the effect when using a fuel with a low share of volatiles and slow char conversion. The results imply that CO2 capture efficiencies can be well above 95 % in a larger industrial unit operating on biomass, even without a carbon stripper, but that a carbon stripper is definitely needed for fuels with less volatiles and low char reactivity.© 2023 The Authors