Blending Wastes of Marble Powder and Dolomite Sorbents for Calcium-Looping CO(2) Capture under Realistic Industrial Calcination Conditions

The use of wastes of marble powder (WMP) and dolomite as sorbents for CO(2) capture is extremely promising to make the Ca-looping (CaL) process a more sustainable and eco-friendly technology. For the downstream utilization of CO(2), it is more realistic to produce a concentrated CO(2) stream in the calcination step of the CaL process, so more severe conditions are required in the calciner, such as an atmosphere with high concentration of CO(2) (>70%), which implies higher calcination temperatures (>900 °C). In this work, experimental CaL tests were carried out in a fixed bed reactor using natural CaO-based sorbent precursors, such as WMP, dolomite and their blend, under mild (800 °C, N(2)) and realistic (930 °C, 80% CO(2)) calcination conditions, and the sorbents CO(2) carrying capacity along the cycles was compared. A blend of WMP with dolomite was tested as an approach to improve the CO(2) carrying capacity of WMP. As regards the realistic calcination under high CO(2) concentration at high temperature, there is a strong synergetic effect of inert MgO grains of calcined dolomite in the blended WMP + dolomite sorbent that leads to an improved stability along the cycles when compared with WMP used separately. Hence, it is a promising approach to tailor cheap waste-based blended sorbents with improved carrying capacity and stability along the cycles under realistic calcination conditions.