| The calcium looping technology which involves multiple calcination/carbonation cycles, utilizes CaO derived from limestone calcium-based sorbents such as a regenerable sorbent to capture CO2at high temperature. The calcium looping is a promising technology because it possesses some advantages such as cheap, low efficiency penalty and widely available CO2sorbent. Carbide slag is a kind of industrial waste obtained in the production of acetylene. Landfill is the ordinary treatment method for carbide slag, but it results in occupation of land and brings a great threat to environment and health of mankind, it is also a waste of calcium sources. Our group has previously investigated that the carbide slag had a good CO2capture capacity in calcium looping technology. Utilizing carbide slag as calcium source instead of limestone for CO2capture can reduce environmental pollution and energy consumption from the mining of natural limestone. This novel technology which combines effective reuse of carbide slag with low-cost CO2capture in coal-fired power plants is promising.Carbide slag showed a decrease in CO2capture capacity with the number of calcination/carbonation cycles. To mitigate deactivation of carbide slag during the long-term cycles, the three modifications of carbide slag to produce new CO2sorbents were proposed in this work:precipitated calcium carbonate made by carbide slag(PCC), carbide slag modified by pyrolignucs acid(MCS) and synthetic sorbent made by combustion preparation route using glycerinum, aluminum nitrate and carbide slag as raw materials. The effects of preparations of modified sorbents and reaction conditions on cyclic CO2capture behavior of the carbide slag were discussed. The microstructures and phase transformation of the calcines from modified sorbents were investigated to reveal the reaction mechanism of CO2capture.The CO2capture behavior of PCC was investigated and a dry/wet technology of CO2capture using carbide slag for coal-fired power plant was proposed. PCC exhibits better CO2capture capacity than the carbide slag. The optimum carbonation temperature for PCC is700℃. The carbonation conversion of PCC is0.51after20cycles, which increases by38%than carbide slag after the same cycles.MCS exhibits better CO2capture capacity than the carbide slag. The carbonation conversion of MCS is0.47after20cycles, which increases by27%than carbide slag after the same cycles. MCS releases the organic substances in the first calcination and the combustion of the orgnic substances leads to increasing of the inner temperature of MCS, which results in sintering of the sorbent. The pre-calcination treatment of MCS at400℃before the1st calcination under pure N2is proposed, the released acetone was recycled. The carbonation conversion of MCS with30min pre-calcination (PMCS) is0.52, which increases by41%than carbide slag. The surface areas and pore volumes of the calcine derived from PMCS are larger than that of the calcined CS and MCS, which is beneficial for CO2capture of the PMCS in the cycles.The main chemical component of carbide slag is Ca(OH)2, which is soluble in glycerin. Al(NO3)3·9H2O is soluble in water. In order to secure uniform mixture of Ca(OH)2and A1(NO3)3·9H2O, glycerin and water are used as a solvent. Synthetic sorbent made by combustion preparation route using glycerin, aluminum nitrate and carbide slag as raw materials exhibited great capacity and stability for CO2capture. The synthetic sorbent gets optimum CO2capture capacity when the mass ratio of CaO/Al2O3is90:10, the combustion preparation temperature is800℃and the carbonation temperature is700℃. The CO2absorption of synthetic sorbent is0.42after20cycles, which increases by38%than carbide slag after the same cycles. The synthetic sorbent maintains good pore structure after20cycles which is beneficial to CO2diffusion and adsorption in sorbent. |
PDF Full Text Request