Cl含量对钙基吸收剂微观结构以及动力学性能的影响

Effect of Cl content on the microstructure and dynamic performance of calcium-based sorbent

通过浸渍法向分析纯CaCO_3中添加Cl,在双固定床反应器系统和热重分析仪上研究了其对钙基吸收剂循环捕集CO_2性能的影响,利用离子反应模型对添加Cl后吸收剂化学反应控制阶段进行动力学分析。结果显示:Cl对钙基吸收剂循环捕集CO_2性能具有不利影响。当Cl/Ca摩尔比大于0.25%后,随Cl/Ca摩尔比增加,化学反应控制阶段反应速率和持续时间均减小,导致在该阶段最终碳酸化转化率降低。对添加Cl前后吸收剂孔隙分布特性进行分析发现,添加Cl导致煅烧后吸收剂烧结加剧,比表面积降低,10~120nm范围内孔分布减少,导致CO_2在吸收剂内部扩散阻力增加,同时能与CO_2反应的CaO量减少,这是导致吸收剂化学反应控制阶段碳酸化反应速度较慢、最终碳酸化转化率较低的主要原因。鉴于Cl的不利影响,在选择钙基材料作为CO_2吸收剂或合成高活性复合吸收剂时,应避免吸收剂中Cl含量过高。

The CO2 capture peformance of the CaCO3 doped with Cl through impregnation method was investigated in a dual fixed-bed reactor together TGA measurment.A gas-solid ion reactive adsorption kinetics model was employed to describe the chemical-reaction controlled stage of the carbonation process of the sorbent.The results show that the existence of Cl has negative effect on the CO2 capture with the calcium based sorbent.When the Cl/Ca molar ratio is greater than 0.25%,both the carbonation rate and the lasting time during the chemical reaction controlled stage decrease with the increae of the Cl/Ca molar ratio,leading to a low ultimate carbonation conversion in this stage.The pore distribution of the Cl-doped sorbent were analyzed through N2 adsorption method.The existence of Cl leads to a lower BET surface area and reduced pore distribution in the range of 10-120nm,resulting in higher CO2 diffusion resistance in the sorbent and less CaO that can react with CO2.Thus,the carbonation rate and ultimate conversion of the Cl-doped sorbent in the chemical reaction controlled stage are lower.Therefore,high content Cl in the final sorbents should be avoided when choosing calcium materials as CO2 sorbent or synthesizing high reactive calcium-based sorbent.