将化工热力学溶液理论和化工流程模拟有机结合，设计了正己烷-甲基环戊烷萃取精馏计算型实验。通过类导体屏蔽电荷真实溶液模型(conductor-like screening model for real solvents，COSMO-RS)计算，基于溶解性、选择性指标筛选离子液体溶剂;通过量子化学计算及屏蔽电荷密度曲线分析溶剂和溶质分子相互作用，探究离子液体促进分离过程的机理;基于筛选的溶剂，利用Aspen Plus软件计算优化萃取分离工艺。该综合实验融合了化工热力学、化工原理和过程系统工程等专业课程内容，同时将学科理论知识与工程实践应用有机结合，强化了专业基本功训练，激发了研究兴趣，提升了创新能力。
Computational experiment design of chemical engineering separation course based on the COSMO-RS theory
[Objective]Chemical engineering separation is a key course in the majors of chemical engineering and pharmaceuticals.However,several issues exist in its teaching.First,the teaching content is based on the classic mass transfer separation principle without introducing new theories and knowledge about novel chemical substances such as ionic liquids(ILs)and process intensification-assisted separation.Second,traditional experiment teachings focus only on phenomenon observations,data recording,and semi-empirical model fitting,lacking theoretical calculations and simulations at the microscopic scale to help students understand interactions and mechanisms in separation systems.Third,there are scarce combinations between theoretical knowledge and engineering issues,which hinders students'ability to solve practical engineering problems.To address these challenges,this work aims to combine basic knowledge with frontier theory and build a new framework of professional knowledge.An advanced engineering educational mode is explored in the context of new engineering majors.Using the case study of extractive distillation of methylcyclopentane(MCP)and heptane,computational experiments involving the theoretical screening of IL solvents,interpretations of IL-facilitated separation mechanisms,and process simulation and optimization are proposed to achieve course innovation.[Methods]In this article,we focus on three aspects of knowledge:extractive distillation principle,solvent screening method,and process simulation and optimization.These components form the basis of the new computational experiment,which is compared with traditional experiment teaching.For the extractive distillation principle,two additional physical quantities of solvable ability and relative volatility at infinitely diluted conditions are used to describe the solubility and separation factor of ILs,respectively.The COSMO-RS model was applied to complete the solvent screening,where sigma profiles,chemical potentials of surface segments of solute molecules,activity coefficients of solutes,and separation factors of screened IL were obtained using the calculation procedure.The process simulations were achieved via the MESH equations,namely the mass balance,energy balance,and phase equilibrium,and the optimization was realized using the sequential iteration procedures and/or sensitivity analysis.[Results]Among the examined 30 ILs,MCP exhibited larger solubility than that of heptane.Solute solubility decreased in the following order:BMPy＞BMIM＞EMMIM＞EMIM＞PCNMIM when ILs had identical anions.A trade-off relation between solubility and separation selectivity for heptane was found,and[BMIM][C1O4]was selected based on this trade-off,synthesis cost,and physiological toxicity.The[BMIM]cation with an alkyl side chain overlaps mainly with MCP in the non-polarity region,and the screen charge density of the[C1O4]anion is significantly larger than that of NMP in the hydrogen acceptor region.These results indicate stronger hydrogen bonding between[BMIM][C1O4]and MCP compared to the NMP-MCP binary system,facilitating the separation of MCP and heptane.The total annual cost(TAC)and distillate purities are used as the objective function and constraints in the process optimization.For the extractive column,the optimized operating parameters were the following:a solvent flow rate of 75 kmol/h,60 trays in the column,a feed tray number of 3 for the solvent and 32 for the feedstock,and a molar reflux ratio of 0.3.The TAC of this optimized flowsheet is 1.57 × 107 CNY.[Conclusions]In summary,this computation experiment design combines thermodynamic solvation theory with process modeling and optimization.Through this new approach,students are able to grasp the design and screening of IL solvents.The complicated microscopic interactions between ILs and solutes and the mechanism of IL-facilitated extractive separation can be deeply understood through quantum chemical calculations.Students can evaluate hydrogen bonding formation and bond strength between cations and anions by analyzing the screening charge density distribution.The ability to solve complex engineering issues can be developed through practical applications in process simulation and optimization.Overall,our computation experiment builds a comprehensive training system that bridges theoretical knowledge and engineering practice.Actual teachings indicate that this course inspires students'learning interests and promotes their innovative thinking and practical skills.It also helps the students understand engineering issues from both fundamental theoretical and practical perspectives.
万方数据
维普
