Optimizing Synergy between Phosphogypsum Disposal and Cement Plant CO2Capture by the Calcium Looping Process

In this work, a novel joint processing route that integrates the disposal of phosphogypsum waste with CO 2 emissions reduction in a cement plant was proposed. The route mainly includes three parts: direct aqueous carbonation of phosphogypsum, use of the obtained carbonation product for CO 2 capture in the calcium looping process (CLP), and manufacture of cement clinker using the spent CaO-based sorbent. The direct use of the CO 2 derived from cement plant flue gas (20 vol % CO 2 ) is able to convert 94.5% of CaSO 4 in the phosphogypsum into CaCO 3 . However, a long time of 90 min is required for the completion of the conversion. Therefore, we proposed to introduce a part of the highly concentrated CO 2 gas stream separated from the CLP and, hence, to increase the overall CO 2 concentration of the carbonation gas stream. It was found that only 45 min is needed to achieve a comparable carbonation level when the gas stream containing 45 (or 60) vol % CO 2 was used. Moreover, the solid carbonation residues derived from phosphogypsum carbonation possess relatively good cyclic CO 2 capture performance, which is superior to the CaCO 3 reagent. It indicates that the joint processing route proposed here is feasible, which can not only recycle the phosphogypsum waste but also reduce the CO 2 emissions in the cement plant.