蒸汽活化钙基吸收剂联合脱碳脱硫特性

Sequential SO_2/CO_2 capture using CaO-based sorbents reactivated by steam

利用管式炉(TF)、蒸汽发生器和热重分析仪(TGA)研究了钙基吸收剂联合脱碳脱硫以及水合特性,并通过N2吸附实验对不同烧结程度以及水合前后样品的孔隙结构进行了测量。结果表明,无水合时,40次碳化循环后的样品碳化活性降至18%,但仍具有44%的硫化活性,比新鲜剂仅低4%,说明脱碳失效剂仍是良好的脱硫剂。碳循环失效剂经蒸汽活化后其碳化活性可提高至68%左右,且具有与新鲜剂类似的活性下降规律。每两次碳化循环后进行一次蒸汽活化,可使样品保持65%的平均转化率。蒸汽活化后吸收剂硫化率可提高至80%,远高于新鲜剂,由电镜扫描实验发现这是由于水合时颗粒产生了大的裂缝和破碎,提供了大量产物可自由生长的外表面积。不考虑颗粒磨损,利用钙基吸收剂先循环脱碳再蒸汽活化最后脱硫是一项联合脱除烟气中CO2和SO2的新方法。

The properties of sequential CO2/SO2 capture using CaO-based sorbent reactivated by steam were studied experimentally with two tube furnaces（TF）,a steam generator and a thermogravimetric analyzer（TGA）.The pore structures of samples at different stages of experiment were investigated by N2 adsorption-desorption.The results showed that the residual carbonation activity for the sorbent after 40 CO2 looping cycles under dry condition was only 18%,while the sulfation activity for that sample was 44%,only 4% lower than the original sample,indicating that the spent sorbent in CO2 capture was still active in SO2 retention.The highly cycled sorbent could be reactivated by steam at 100℃ under atmospheric pressure,and the carbonation activity could be restored to about 68% which decayed in the next CO2 looping cycles in the same way as the fresh sample.The average conversion of the sorbent during 20 cycles could be kept at above 65% when one steam reactivation is conducted after every two CO2 looping cycles.It was the loss of surface area and pore volume that caused the decay of sorbent activity,while the sulfation conversion was not proportional to surface area or pore volume.Although the original sample had the best pore structure,the steam reactivated sorbent got the highest sulfation conversion of 80%,much higher than the original sample.From SEM analysis,the improvement resulted from the fracture of sorbent during hydration and dehydration,which provided more particle outer surface where reaction product could grow freely.The product growing space had a greater influence on sulfation than on carbonation due to greater molar volume of CaSO4 than CaCO3,thus sulfation conversion was higher than carbonation conversion for reactivated sorbent and highly cycled sorbent with more macropores.Despite particle attrition,it was practical to use CaO-based sorbent with steam reactivation for capturing CO2 and SO2 sequentially.