CO2 Capture Performance of Mesoporous Synthetic Sorbent Fabricated Using Carbide Slag under Realistic Calcium Looping Conditions

Calcium looping is techno-economically feasible for industrial CO2 reduction. Carbide slag as a waste from the PVC (polyvinyl chloride) industry is a good candidate for low-cost calcium-based CO2 sorbents. A novel synthetic sorbent with rich mesopores was fabricated from high alumina cement, carbide slag, and byproduct of biodiesel, in order to overcome the loss in CO2 capture capacity of calcium-based sorbents with the number of carbonation/calcination cycles. The CO2 capture capacities of synthetic sorbents were examined under the severe calcination condition of high CO2 concentration and high temperature, which is close to the actual atmosphere for industrial applications. The effects of high alumina cement addition, byproduct of biodiesel addition, calcination condition, and steam addition in carbonation atmosphere on CO2 capture by the synthetic sorbents were also discussed. Results show that the synthetic sorbent with 90 wt % CaO achieves the highest CO2 capture capacity of about 0.27 g/g after 30 cycles under the realistic calcination condition, which is 1.7 times higher than that of carbide slag. N2 physisorption measurement reveals typical mesoporous structure in the synthetic sorbent with 90 wt % CaO and large amounts of pores in the range of 10–100 nm are maintained over 10 cycles. C12A7 (Ca12Al14O33) and C2AS (Ca2Al2SiO7) are found in the synthetic sorbent, which are uniformly distributed as the pore skeleton between CaO grains. The combining effect of the mesoporous structure and stabilization of pores over the repeated cycles is responsible for the high CO2 capture capacity of the synthetic sorbent. The synthesized mesoporous CO2 sorbent appears promising for the implementation of the cost-effective CO2 capture technique.