Characterization of the oxy-fired regenerator at a 10 kWth dual fluidized bed calcium looping facility

Calcium looping is a CO2 capture technology, developed in the last years with great potential to contribute to the reduction of greenhouse gases emissions. It consists of a carbonator where CO2 contained in power plant flue gas, is absorbed by CaO producing CaCO3 and a regenerator where the CaCO3 is calcined to CaO releasing a highly concentrated CO2 stream. A key aspect of the process is the oxy-combustion of the fuel in the regenerator to provide the heat for the endothermic calcination reaction. This implies high CO2 concentration in the off-gas and requires a flue gas recycle. Aim of this work is the characterization of the regenerator operation under this environment and thus experiments were performed at the 10 kWth IFK Dual Fluidized Bed facility. Regenerator efficiency and sorbent performance in terms of chemical activity and mechanical stability are the two basic parameters investigated, while the active space time is used for interpretation of the results. It is found that high calcination conversions can be achieved with temperatures less than 920 °C. Sorbent achieves a residual CO2 carrying capacity similar to the one referred to the literature. The sorbent proved to be mechanically strong thus optimistic percentage of material loss was recorded to be 0.8 wt.%/h or 0.024 mol Ca/mol CO2.