碳酸二乙酯吸收CO_2的性能评价

Performance Evaluation of CO_2 Capture with Diethyl Carbonate

全球CO_2减排的要求日益严峻,碳捕集成本较高,迫切需要开发高效率、低成本的捕集技术。碳酸二乙酯（DEC）是一种新型高效的CO_2吸收溶剂,今采用恒定溶剂法测定282.79~302.69 K下CO_2在DEC中的溶解度,并采用Prausnitz-Shair法、分子连接性指数（MCI）和PR状态方程法对其进行了预测;通过与碳酸二甲酯（DMC）的相平衡数据对比,发现相同温度下,DEC的亨利系数小于DMC。采用连续吸收-解吸实验对DEC吸收CO_2效果进行综合评价,通过研究液气比、吸收温度、解吸温度（采用加热解吸）和N_2流量（采用气提解吸）对CO_2吸收率的影响,探索出最佳操作条件;并与DMC的实验结果进行对比,发现采用N_2气提解吸,DEC系统成本明显低于DMC。加热解吸能耗高,气提解吸溶剂损失大,因而探索了一种通过压缩、冷凝进行解吸的新流程,经模拟计算,发现其流程简单,系统成本比加热解吸少,但比气提解吸多;与DMC结果进行对比,发现DEC优于DMC。结果表明,DEC是一种比较有潜力的CO_2吸收溶剂。

CO2 emission reduction is now urgently required as global warming intensifies. However, the high cost of capturing CO2 seriously restricts its development. Therefore, it is urgent to develop a high-effective carbon capture technology. Diethyl carbonate （DEC） is a novel CO2 absorbent. CO2 solubility in DEC was experimentally determined by the constant volume method at the range of 282.79-302.69 K, at same time which was predicted by Prausnitz-Shair method, Molecular Connectivity Index and Peng-Robinson （PR） equation of state. It is showed that the Henry constants of DEC are smaller than those of DMC at the same temperature by comparison of their phase equilibrium data. The continuous absorption and desorption experimental apparatus and process simulation were applied to study on the performance of DEC capturing CO2. The effects of the liquid-gas ratio, absorption temperature, desorption temperature （if thermal desorption was adopted） and N2 flow （if gas stripping desorption was adopted） on CO2 absorptivity were studied and the optimal operation conditions were obtained. Through comparison with DMC, it was found that using N2 gas stripping desorption the system cost of DEC is smaller than that of DMC. Because of the high energy consumption of thermal desorption and high solvent loss of gas stripping desorption, a novel desorption process was applied, which was modified by applying compression and condensation to desorb the loaded liquid. It simplifies the process and its system cost is smaller than that of thermal desorption, but larger than that of gas stripping desorption. It＇s found the results of DEC is better than that of DMC. Results show that DEC is a potential CO2 absorbent.