CO2 capture performance using limestone modified with propionate acid during calcium looping cycle

Limestone was modified with excessive propionate acid solution. The cyclic CO2 capture performance of the modified limestone during calcium looping cycle was investigated using a thermo-gravimetric analyzer (TGA) and a twin fixed-bed calcination/carbonation reactor system. The results obtained prove that the modified limestone can be an effective sorbent for CO2 capture at high temperature. The modified limestone exhibits obviously faster carbonation rate, and achieves higher carbonation conversion than the original one under the same reaction conditions. The optimum carbonation temperature for modified limestone is between 680 degrees C and 720 degrees C. Higher calcination temperature can aggravate sintering of the sorbent during calcination periods. The modified limestone shows better anti-sintering properties than original one at high calcination temperature. Long-term CO2 capture capacity of the sorbent is enhanced by modification using propionate acid, resulting in a carbonation conversion of 0.31 for modified limestone after 100 cycles, while the value for original limestone is only 0.08. The surface morphology of the modified limestone after the first calcination is much more porous and the pores are more connective than that of the original one. A much better pore structure is kept after 100 cycles for modified limestone. It indicates that modified limestone is much more sintering resistant than original one during cyclic reactions.