Finally, favorable economics can be achieved by using the purged material from the calcium looping cycle in cement production. The raw feed for cement production includes ~ 85 wt% limestone with the remaining material consisting of clay and additives (e.g. SiO, AlO etc.). The first step in the process involves calcinating limestone to produce CaO, which is then mixed with other materials in a kiln to produce clinker.
Using purged material from a Ca-looping system would reduce the raw material costs for cement production. Waste CaO and ash can be used in place of CaCO (the main constituent cement feed). The ash could also fulfill the aluminosilicate requirements otherwise supplied by additives. Since over 60% of the energy used in cement production goes into heat input for the precalciner, this integration with Ca-looping and the consequent reduced need for a calcination step, could lead to substantial energy savings (EU, 2001). However, there are problems with using the waste CaO in cement manufacture. If the technology is applied on a large scale, the purge rate of CaO should be optimized to minimize waste.