石灰石循环分离CO_2过程活性下降原因分析

Activity Decline Analysis of the Cyclic CO_2 Capture Using Limestone

为了得到石灰石循环分离CO2过程活性下降的原因,在热重分析仪上考察了石灰石循环煅烧/碳酸化反应特性,并利用扫描电镜(scanning electron microscopy,SEM)考察了不同循环次数下样品表面结构的差异。结果表明:CaO碳酸化反应主要由化学反应控制阶段和产物层扩散阶段组成,石灰石循环反应活性降低主要由化学反应控制阶段CaO转化率的下降引起,而其根本原因是循环反应过程中烧结所引起的空隙结构变化促使反应迅速的化学反应控制阶段提前结束,CaO碳酸化反应较早地进入到反应缓慢的产物层扩散控制阶段。

In order to get the reason for the activity decline of recycling CO2 separation with limestone, the charac teristics of limestone cyclic calcination / carbonation reaction were experimentally investigated in a thermogravimet ric analyzer, and the differences of sample surface structure of different cycle number were examined using Scan ning Electron Microscopy （SEM）. The results show that CaO carbonation reaction mainly consists of chemical re action controlling stage and product layer diffusion controlling stage. The main reason of the decreasing activity of limestone recycling reaction activity is the decrease of the CaO conversion rate of the chemical reaction controlling stage. And the basic reason is that the space structure change caused by sintering during recycling reaction makes the quick chemical reaction controlling stage ending early, and CaO carbonation reaction turns into slow product layer diffusion controlling stage more early.