循环煅烧/碳酸化反应中CaO微观结构变迁特性

Variation behavior of CaO microstructure during cyclic calcination/carbonation

对CaO在循环反应中的碳酸化特性和微观结构变迁特性进行了研究.研究表明,CaO在700℃碳酸化时能取得最佳的CO2捕捉性能,高煅烧温度不利于CaO的碳酸化.随着循环次数的增加,CaO的孔隙由粗糙、具有网状连接和多孔的结构逐渐向平滑、孔间连接较差和较少孔的结构转变.CaO比表面积和比孔容均随循环次数增加而减小.前10次循环反应使CaO比表面积衰减迅速,此后变化缓慢.随着循环次数的增加,CaO的孔容和孔表面积分布均变差,CaO平均孔径逐渐增大.每次循环中,CaO中孔（2-50nm）的孔表面积大于大孔（大于50nm）的孔表面积.CaO碳酸化转化率随其比表面积和比孔容增加而增大,但当超过比表面积和比孔容的临界值后其转化率则可能减小.

The cyclic carbonation characteristics and microstructure variation performance of CaO were investigated. The results show that CaO exhibits the optimum CO2 capture performance at the carbonation temperature of 700 ℃. The high calcinaiton temperature is not beneficial to the carbonation of CaO. The pores of CaO become smooth, poor connecting and less porous instead of rough, net-shaped interconnected and porous as the cycle number increasing. CaO shows a reduction in specific surface area and pore volume with the number of cycles. The specific surface area of CaO has a sharp decay during the initial 10 cycles, and then the variation slows down with further increase of cycle number. The pore volume and pore surface area distributions of CaO exhibit worse with the number of cycles. The average pore size of CaO increases with the number of cycles. The surface area of mesopore （2 to 50 nm） is higher than that of macropore （above 50 nm） at each cycle. The carbonation conversion of CaO exhibits an improvement with the increase of specific surface area and pore volume; however, it may decrease when the specific surface area and pore volume are over some critical value.