离子液体用于燃烧后二氧化碳捕集的热力学及过程模拟研究

THERMODYNAMICS AND PROCESS SIMULATIONS FOR POST-COMBUSTION CO_(2) CAPTURE WITH IONIC LIQUIDS

近年来,在CO_(2)碳捕集领域中,离子液体发挥了极大的作用。提出采用离子液体作为吸收剂用于燃烧后同时捕集CO_(2)和水汽。首先,通过COSMO-RS模型筛选了522种离子液体,选择了1-丁基-3-甲基咪唑双(三氟甲烷磺酰)亚胺盐([BMIM][Tf_(2)N])和1-乙基-3-甲基咪唑四氟硼酸盐([EMIM][BF_(4)])这2种离子液体用于同时捕集CO_(2)和水汽。其次,采用COSMO-RS模型预测了CO_(2)在离子液体中的溶解度,检验了模型预测能力。此外,分析了2种离子液体与CO_(2)分子之间的相互作用,阐明了分离机制。最后,设计并优化了离子液体(纯[BMIM][Tf_(2)N]和[BMIM][Tf_(2)N]与[EMIM][BF_(4)]等摩尔混合物)作为吸收剂同时捕集CO_(2)和水汽的工业流程。结果表明,[BMIM][Tf_(2)N]和混合离子液体均表现出良好的CO_(2)和水的捕集效果,其中混合离子液体的捕集效果优于纯[BMIM][Tf_(2)N]。在混合离子液体(摩尔比[BMIM][Tf_(2)N]∶[EMIM][BF_(4)]=1∶1)流程中,在优化的操作条件下,即质量液气比(4∶1)、吸收塔操作压力(3 MPa)、吸收剂再生温度(160℃)和压力(0.005 MPa)的优化组合,吸收塔产品气中CO_(2)含量可降低至88 ppm(摩尔分数),水汽几乎全部吸收,水含量可降低至1 ppm(摩尔分数)。

In recent years,ionic liquids(ILs)have played a noteworthy and significant role in the field of CO_(2)capture.This study proposes the usage of ILs as absorbents for the simultaneous post-combustion capture of CO_(2)and water vapor.Initially,1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide([BMIM][Tf_(2)N])and 1-ethyl-3-methylimidazolium tetrafluoroborate([EMIM][BF_(4)])were picked and selected as absorbents from a total of 522 types of ILs for the aforementioned purpose by using the COSMO-RS model,and out of these,Subsequently,the COSMO-RS model was employed to predict the solubility of CO_(2)in ILs,and its predictive accuracy was verified.Furthermore,the interaction between the two ILs and CO_(2)molecules was analyzed in order to elucidate the separation mechanism.Lastly,an industrial process for the simultaneous capture of CO_(2)and water vapor using ILs(either the pure[BMIM][Tf_(2)N]or a mixture of[BMIM][Tf_(2)N]and[EMIM][BF_(4)])as absorbents was designed and optimized.The findings and outcomes of this study showed that both the pure[BMIM][Tf_(2)N]and the mixed IL exhibited exceptional and commendable capture efficiency for CO_(2)and water vapor,with the mixed IL performing better than the pure[BMIM][Tf_(2)N].The mixed IL process(mass ratio[BMIM][Tf_(2)N]∶[EMIM][BF_(4)]=1∶1)is more recommended,because by employing the well-optimized operating conditions of absorption,liquid-gas molar ratio(4∶1),absorption tower pressure(3 MPa),absorbent regeneration temperature(160℃),and pressure(0.005 MPa),the CO_(2)content in the absorption tower product gas can be reduced to 88 ppm(molar fraction),and water vapor can be almost completely and entirely absorbed with only 1 ppm(molar fraction).