【作者】 武向红；

【导师】 郑丹星；

【作者基本信息】 北京化工大学 ， 化学工程， 2010， 博士

【摘要】 吸收分离是一种重要的气体处理过程,在环境保护、低碳化学品生产、以及低碳技术的能源利用新方式等许多方面的应用日益广泛。吸收分离技术开发的关键是研究优良的吸收剂。高吸收能力的吸收剂,是提高装置生产能力,降低能源消耗和产品综合成本等的关键。本文旨在研究指导吸收剂开发的理论基础,并探索CO2体系和乙烯体系的吸收剂新材料。基于热力学性质与分子间相互作用的能量关联,本文探索吸收剂选择的热力学判据,并通过实验测定气液相平衡数据和气体吸收分离工艺的流程模拟验证吸收剂评价方法的可行性。主要内容如下：首先通过归纳和分析气体吸收过程的气液相平衡(VLE)热力学特征行为,提出了两个选择吸收剂的热力学评价准则,可以根据气体吸收质和吸收剂二元体系的最大超额Gibbs函数GEmax和吸收势ψi来选择吸收剂。即体系的GEmax数值越小,吸收剂的吸收效果越显著。另一方面,也可以分析气体吸收质的吸收势。ψi数值越大,则吸收剂的吸收效果越显著。在没有实验数据时,GEmax和ψi的数值可以采用UNIFAC模型预测。基于上述工作,本文分别筛选了分离CO2和分离C2H4的吸收剂。研究结果表明：醇类和酯类对CO2的吸收效果较好。而在酯类中甲酸酯类对CO2的吸收效果明显优于其它酯类。酯类、醚类和酮类对C2H4的吸收效果明显。在芳烃吸收剂中,从甲苯、二甲苯到三甲苯,ψi数值显著增大,而GEmax数值显著减小。其次,搭建了静态法测定VLE数据的实验装置。测定了CO2+丁醚二元体系的VLE数据,使用PR状态方程对VLE数据进行拟合,得到方程的二元交互作用参数Kij0.0401。并分别测定了C2H4+甲苯二元体系以及的C2H4+1,3,5-三甲苯二元体系的VLE数据,开展了VLE数据关联与模型化研究。综合比较CO2体系和乙烯体系的实验数据以及VLE文献数据,采用本研究提出的GEmax值与ψi值对体系吸收特性的评价得到实验验证。即GEmax值越小,或ψi值越大,y1／x1值也越小,气体在吸收剂的溶解度越大。最后,本文利用Aspen Plus软件和VLE研究得的模型参数,开展了CO2体系和乙烯体系的吸收分离工艺研究,以进一步验证本研究的理论工作。采用丁醚为吸收剂的合成气CO2净化工艺流程模拟结果表明,净化气的CO2含量可以低于0.4%以下,采出气CO2的纯度可以达到95.37%以上,原料混合气的CO2回收率可以达到86%以上,分离效果良好；该工艺的能耗要小于现有的低温甲醇洗工艺(Rectisol法)和以聚醇醚(Selexol)为吸收剂的工艺。采用1,3,5-三甲苯作为吸收剂,从干气中回收C2H4的工艺流程模拟结果表明,与以液化石油气为吸收剂的专利流程比较,本流程具有吸收、解吸操作压力低,吸收剂损失小,能耗低的优点。更多还原

【Abstract】 Absorption is an important method for gas separation. It has been widely used in environment protection, low-carbon chemicals manufacturing and new energy resource utilizing. To develop an appropriate absorbent is the primary achievement of the absorption technology. High efficient absorption is the key point to increase the facility output, decrease the energy consumption and product comprehensive cost.A focus on theoretical basis of developing new absorbent was studied in the paper, and novel absorbents for CO2 system and ethylene system were under researching as well. On the basis of energy correlation between thermodynamic properties and molecule interactions, the thermodynamic criterions of absorbent selection were investigated. Through measuring the data of vapor-liquid phase equilibrium (VLE) and simulating the gas absorption processes, this evaluation method of absorbent is proven. The main contents are shown as follows.Firstly, two thermodynamic criterions for absorbent selection were proposed by analyzing and evaluating thermodynamic characteristic behaviors of VLE in absorption process, i.e. the appropriate absorbent can be selected by the extrema value of the excess Gibbs function (GEmax) and the absorption potential(ψi) for a binary system of absolute-gas and absorbent. The less the system GEmax value is, the more significant the absorption effect will be; on the other hand, it can be evaluated by the absorption potential of the gas-absolute. Namely, the bigger theψi value is, the more significant the absorption effect will be. Meanwhile, the GEmax value and theψi value can be estimated by UNIFAC model.Base on the above research, the absorbents for CO2 system and C2H4 system were chosen accordingly. By analysis and comparison, alcohols and esters have a good absorption effect for CO2 system, especially, formate esters have a much more better performance than other esters; esters, ethers and ketones have a good effect for C2H4 system. For the series of aromatic hydrocarbons, from toluene, xyluene to trimethylbenzene, theψi value was significantly increasing, but the GEmax value was singnificantly decreasing.Secondly, the experimental apparatus has been set up to measure VLE data using static equilibrium method. The VLE data of CO2+butyl ether system was determined and correlated by the Peng-Robinson equations of state, then the binary interaction parameter (ky) was reduced, kij= 0.0401. The VLE measurements and data correlations for C2H4+toluene system and C2H4+1,3,5-trimethylbenzene system were performed respectively. By analysing the VLE experimental results and the reference data of CO2 systems and C2H4 systems, it was validated the absorption performance evaluations using the GEmaxvalue and theψi value proposed by this work. Namely, the less of the GEmax value, or the bigger of theψi value, the less y1/x1 is, and the bigger gas solubility is in the absorbents.Finally, the theoretical proposal of the paper has been validated as well by following research. The absorption processes of CO2 system and C2H4 system have been simulated by adopting Aspen Plus software and the VLE model parameters obtained from this work. The simulation result for the syngas purifying process by butyl ether absorbent shows that the CO2 content of purified gas can be lower than 0.4%, the CO2 content of off-gas can be up to 95.37% or more, the CO2 recovery ratio for feed-stock can be more than 86%, appearing excellent separating results; whilst the energy consumption was much less than present technologies by Rectisol absorbent and Selexol absorbent. The simulation result for the C2H4 recovering process by 1,3,5-trimethylbenzene absorbent shows that the process has lower operating pressure of absorbing and desorbing, less lose of absorbent and less energy consumption, compared with the patent process using LPG as absorbent.更多还原