Biomass Chemical Looping Gasification for Power Generation

Chemical looping gasification (CLG) technology has proven to present itself as a promising alternative to conventional thermal power generation processes, offering potentially higher efficiencies and lower costs. To determine its feasibility on a large scale, a biomass chemical looping gasification combined cycle (BCLGCC) model using Aspen Plus software was developed, validated using experimental data and scaled up to 650 MW. A techno-economic and sustainability analysis was then conducted and compared to 4 other power generation technologies with and w/o CCS. BCLGCC presents promising economic and environmental results, showing that the efficiencies of the CCS and Non-CCS plants equal to 36% and 41%, respectively, with COE (including government subsidies) for both CCS and Non-CCS equal to 15.9 ¢/kWh and 12.8 ¢/kWh, both of which are lower than the average COE in the UK. A life cycle energy use, CO2 emissions and cost input evaluation of a 650 MW BCLGCC and a BIGCC/CIGCC power generation plants with and w/o CCS are analysed then compared to coal/biomass combustion technologies. The life cycle evaluation covers the whole power generation process including biomass/coal supply chain, electricity generation and the CCS process. Gasification power plants showed lower energy input and CO2 emissions, yet higher costs compared to combustion power plants. Coal power plants illustrated lower energy and cost input; however higher CO2 emissions compared to biomass power plants. Coal CCS plants can reduce CO2 emissions to near zero, while BCLGCC and BIGCC plants with CCS resulted in negative 680 and 769 kg-CO2/MWh, respectively. Regarding the total life cycle costs input, BCLGCC with and w/o CCS equal to 149.3and 199.6 £/MWh, and the total life cycle energy input for both with and without CCS is equal to 2162 and 1765 MJ/MWh, respectively. Finally, a set of BCLG experiments were conducted in a fixed bed reactor using fresh hematite and pine sawdust. The experiments consisted of testing the effect of temperature, biomass to oxygen carrier (OC) ratio and multiple cycles on the gas yield, LHV, cold gas efficiency, carbon conversion, XRD results, SEM imagine of the surface of the OC and EDX data. The results showed that the carbon conversion was low compared to when using other sources of biomass, and consequently LHV, gas yield, cold gas efficiency. Moreover, it was observed that as temperature, reaction time and B/OC ratio increased the surface of the oxygen carrier would undergo sintering and agglomeration, with the oxygen being consumed reducing the main component of the hematite (Fe2O3) into three phases including Fe3O4, FeO and Fe.