The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

Calcium looping is a CO2 capture scheme using solid CaO-based sorbents to remove CO2 from flue gases, e.g., from a power plant, producing a concentrated stream of CO2 (∼95%) suitable for storage. The scheme exploits the reversible gas–solid reaction between CO2 and CaO(s) to form CaCO3(s). Calcium looping has a number of advantages compared to closer-to-market capture schemes, including: the use of circulating fluidised bed reactors—a mature technology at large scale; sorbent derived from cheap, abundant and environmentally benign limestone and dolomite precursors; and the relatively small efficiency penalty that it imposes on the power/industrial process (i.e., estimated at 6–8 percentage points, compared to 9.5–12.5 from amine-based post-combustion capture). A further advantage is the synergy with cement manufacture, which potentially allows for decarbonisation of both cement manufacture and power production. In addition, a number of advanced applications offer the potential for significant cost reductions in the production of hydrogen from fossil fuels coupled with CO2 capture. The range of applications of calcium looping are discussed here, including the progress made towards demonstrating this technology as a viable post-combustion capture technology using small-pilot scale rigs, and the early progress towards a 2 MW scale demonstrator.

Research highlights▶ A review paper on Ca-looping as a novel post-combustion CO2 capture scheme. ▶ Introduction to the technology including a review of current sorbent performance. ▶ The implications of integrating Ca-looping CO2 capture and cement production. ▶ Overview of results from world-wide Ca-looping pilot-plant scale trials. ▶ Advanced Ca-looping applications including H2 production/electricity generation.