Pilot tests with waste and biomass in a 150 kWth autothermal CLC unit

Carbon capture and storage from biogenic feedstocks have recently been emphasized as an important contributor to reach climate neutrality by 2050. Chemical looping combustion (CLC) is an attractive technology in this respect, as it can convert biogenic fuels with high electric efficiency and relatively low capture cost. CLC with biomass has already been demonstrated up to 1 MWth scale, but no pilot demonstrations using waste-derived fuels have been done. In this work, pilot tests with solid recovered waste fuel (SRF) are performed in the 150 kWth scale CLC pilot unit at SINTEF Energy Research in Norway. Tests with woody biomass performed in the same unit serve as a reference. The fuel feeding rate is equivalent to about 115 kWth based on the fuel’s lower heating value. The oxygen carrier (OC) material is Norwegian ilmenite. The results show that the CO₂ capture efficiency is high, 97.5–98% for the SRF cases. This is even higher than the two biomass cases, which had capture efficiencies of 93.5–95%. The high CO₂ capture efficiencies are obtained even though this pilot unit has a simplified design without a carbon stripper between the fuel and air reactor. The results indicate that for such reactive and volatile fuels as woody biomass and SRF waste, a carbon stripper might be omitted, saving both investment and operational costs. The fuel reactor (FR) gas conversion efficiency is 80–81% for the SRF cases and slightly lower for biomass with values of 76.5–79.5%. In one test with biomass, ilmenite was mixed with a large share of manganese oxide. This resulted in an increase of the FR gas conversion efficiency of nearly 9%-points. This is most likely due to the higher ability of manganese oxide to release oxygen directly into the FR gas phase, which will ensure a better conversion of volatiles. In essence, the tests show that both SRF and woody biomass are suitable fuels for CLC, that stable autothermal operation can be achieved, and that the carbon capture rate can be high for these fuels even without a carbon stripper.