Solar-driven calcium looping system for carbon capture in cement plants: Process modelling and energy analysis

The cement industry produces around 6-7% of the global anthropogenic CO2 emissions. This sector, therefore, needs to be decarbonized to meet the international goals on greenhouse gas emissions. In a cement plant, however, around 60% of the CO2 emissions are hard-to-abate because they come from the calcination of the raw materials. Carbon capture is thus needed to perform deep decarbonization of the cement production process. Among all the carbon capture technologies proposed in the literature, Calcium looping (CaL) is one of the most promising ones. This work analyses on novel solar-driven CaL process for carbon capture in a cement plant. In the system proposed, the energy required for the CO2 sorbent regeneration is fully supplied by a heliostat field. The performances of the overall system were evaluated through detailed process modelling and energy analyses. Primary energy consumption and CO2 emissions (sum of both direct process emissions and indirect emissions due to electricity consumption) were assessed considering different grid electricity mixes and integration levels (IL) between the carbon capture system and the clinker kiln. We estimate that the integration of a solar-driven CaL in a cement plant could be able to reduce over 90% of the plant CO2 emissions. Furthermore, this solution could potentially decrease the plant fuel consumption thanks to the reuse of the exhausted sorbent in the production process. On the other hand, a large heliostat field will be required to feed energy to the CaL process. Both the carbon intensity of the grid electricity mix and the IL impact on the system energy and carbon balance, as shown by the obtained values for the specific primary energy consumption for CO2 avoided (SPECCA) index. Obtained SPECCA indexes vary between a maximum of 2.17 MJ/kgCO2, obtained for an IL of 20% and grid electricity produced entirely from renewables, and a minimum of 0.57 MJ/kgCO2, estimated for an IL of 80% and grid electricity produced from state-of-the-art pulverized coal.