【作者】 王彬；

【导师】 张小斌； 韩一松；

【作者基本信息】 浙江大学 ， 工程硕士（专业学位）， 2020， 硕士

【摘要】 随着现代社会科技发展,电子、冶金、石油精炼和航空航天等产业对纯氮、纯氧等工业气体的需求日益激增,大型低温空气分离已成为目前大规模生产高纯气体产品的主要技术。目前在空分系统设计和运行中,节能降耗已成为主要考虑的因素。精馏塔是低温空气分离系统降低能耗的关键部机。精馏过程的流动和传热传质机理建模正是实现精馏塔设计与优化、精馏系统实时控制的核心。为开发出准确度高且求解速度快的过程机理模型,本文围绕非平衡级模型开展了以下研究工作:1.通过阅读和整理大量文献,详细论述了与低温精馏过程机理建模和精馏塔优化设计相关的国内外研究进展。首先总结了空气分离过程的主要技术和发展趋势,阐明了精馏过程机理建模对低温系统在线控制的研究意义;而后整理并介绍了近20年国内外学者研究现状,阐述了平衡级模型、混合级模型和非平衡级模型的研究进展和应用案例;同时结合动态控制需求,综述了动态预测模型的建模方法和不同类型以及在低温空分领域的应用;又针对现有精馏塔的优化操作与控制的需求,论述了智能优化算法的特点以及在化工优化问题中的应用,为后续研究工作奠定了基础。2.建立了低温精馏非平衡级模型并确定求解策略。考虑低温精馏过程具备一定的特殊性,以规整填料上塔为研究对象,对低温精馏氧、氮、氩三元物系建立了非平衡级模型。随后,利用分离效率函数,将模型分割化简,采用Thomas算法快速求解,避免了求解庞大的非线性方程所带来的内存和存储空间问题,给出了一种有效的求解策略。3.验证了模型及求解策略有效性并对现有传质关联式开展可靠性评估工作。通过Fortran语言对非平衡级模型实现编程求解,将模拟结果与测量数据以及成熟商业软件Aspen plus中Rate-based模块的模拟结果对比,分析表明,本模型的组分浓度、流量以及温度等参数均吻合良好,说明整个模型和求解策略有效。随后,在此精馏计算程序的基础上,对现有常温下获得的6组传热传质经验关联式开展了评估工作,验证了它们在低温精馏模型中的可靠性。4.提出了一种改进的粒子群优化算法(MI-PSO),开展了低温精馏塔优化设计工作。首先探究了上塔的稳态特性,对各进、出物料流量和位置等参量完成灵敏度分析,总结出它们对奇点位置和强弱变化以及(火用)损和冷凝蒸发器热负荷的影响规律。随后,在已有的精馏计算程序基础上,结合MI-PSO智能优化算法,以整塔(火用)损最小和冷凝蒸发器热负荷最小为多目标函数,对17000 Nm3/h的低温精馏规整填料上塔完成了结构与操作参数优化工作,整塔(火用)损和冷凝蒸发器热负荷分别下降了36.3%和5.4%,为低温精馏塔的优化设计提供了一种快捷省力的解决方法。更多还原

【Abstract】 With the rapid development of science and technology,electronics,metallurgy,petroleum refining,aerospace and other industries have increasing demand for industrial gases such as pure nitrogen and pure oxygen.Large-scale cryogenic air separation units(ASU)have become the main source for large quantities of high-purity gas products.At present,energy saving and consumption reduction have become important considerations in the design and operation of the ASU.The distillation columns,key to the cryogenic air separation system,have the largest energy consumption.Modeling of the distillation process mechanism is the important part for realizing the optimization and real-time control of the distillation system.In order to develop a process mechanism model that is both accurate and fast,the following research work is carried out around the non-equilibrium model(NEM):1.The Through reading and collating a large number of literatures,the research progress at home and abroad related to the modeling of cryogenic distillation process mechanism and the optimal design of distillation column were discussed in detail.Firstly,the main technologies and development trends of the air separation process were summarized,and the significance of the mechanism modeling for the cryogenic ASU was clarified.Then,the research status of mechanism modeling by domestic and foreign scholars in the past 20 years was systematically summarized.At the same time,the dynamic prediction models for cryogenic air separation system were reviewed in combination with the requirements of dynamic control.Aiming at the requirements of the optimization operation and control,the characteristics of the intelligent optimization algorithm and its application in chemical optimization problems were discussed,which laid the foundation for subsequent research work.2.The NEM for cryogenic distillation was established and the solution strategy was determined.Considering the particularity of the cryogenic distillation process,the NEM was established under the low temperature conditions with the structured packing column(SPC)as the research object.Subsequently,the separation efficiency function was used to simplify the model,and the Thomas algorithm was used,which avoided the memory and storage space problems caused by solving large nonlinear equations.3.The validity of the model and solution strategy was verified,and the reliability evaluation of different kinds of mass transfer correlation was carried out.The NEM was programmed by Fortran language.The simulation results were compared with those from the Rate-based module of Aspen plus and limited measured data,which confirmed the effectiveness of the model and solution strategy.Then,based on the program,the feasibility of the reported mass transfer correlations on the cryogenic distillation calculation was investigated.4.Combined with the modified particle swarm optimization algorithm(MI-PSO),the optimal design of the cryogenic distillation column was carried out.Firstly,the steady state characteristics of the upper SPC were summarized,which revealed the influence of varied feed locations and rates on the exergy loss and main condenser heat load.Then,combing MI-PSO with the distillation calculation program,the structure parameters of the upper SPC for 17000 Nm3/h were optimized,and the exergy loss of total column and main condenser heat load were reduced by 36.3% and 5.4%,respectively,which provided a simple and effortless solution for the optimal design of the cryogenic distillation column.更多还原