Design of flexible heat exchanger network for multi-period operation

Heat exchanger networks (HENs) increase heat recovery from industrial processes by matching hot and cold streams to exchange heat and reducing utility consumption. The design of HENs is a very complex task which generally involves mixed-integer non-linear programming (MINLP).This work evaluates and critically compares existing HEN design methods. It then presents a systematic methodology in the design of HENs under multiple periods of operation. The model presented in this work is a superstructure-based MINLP model which minimises the total annualised cost containing heat exchanger area cost and utility costs. The model is based on the superstructure by Yee and Grossmann [1990. Simultaneous optimisation models for heat integration—II, heat exchanger network synthesis. Computer & Chemical Engineering 14(10), 1165-1184], which was later formulated for multiple periods by Aaltola [2002. Simultaneous synthesis of flexible heat exchanger network. Applied Thermal Engineering 22, 907-918]. It includes a multi-period simultaneous MINLP model to design the HEN structure, and an NLP model to improve the solution and allow for non-isothermal mixing. Modifications to Aaltola's model include the use of maximum area per period in the area cost calculation of the MINLP objective function, and the removal of slack variables and weighed parameters from the existing NLP improvement model.The new model has been applied to one industrial case study, demonstrating that the new combined MINLP-NLP model can obtain better solutions by not relying on the average area assumption in the MINLP stage.     

MTBE合成与裂解联合装置的用能一致性

提出用能一致性原则,对ＭＴＢＥ合成与裂解联合装置全过程进行用能分析,从用能的角度上将过程系统一致起来,提高了系统的集成性;同时应用虚拟温度法及ＨＥＸＴＲＡＮ软件及自行开发的夹点分析软件对该系统进行用能分析及换热网络匹配,节能约２０％     

计算机辅助软件在化工设计课程教学中的应用

化工设计是化工类专业的一门重要专业课,具有综合性、实用性和工程性等特点。本文拟介绍将5种计算机辅助软件运用于化工设计教学中的具体应用。结果表明,此类软件增强了学生学习本课程的兴趣,教学质量得到明显改善。     

Framework for work‐heat exchange network synthesis (WHENS)

Work and heat are the two predominant forms of energy in the process industry. Considerable savings can be achieved by synergizing the work and heat requirements of process streams. A generalized framework for integrating heat and work simultaneously is proposed based on a mixed‐integer nonlinear programing model for work‐heat exchange network synthesis. Starting with a set of streams with known flows, temperatures, and pressures, a network of single‐shaft‐turbine‐compressors with motors/generators, valves, heat exchangers, and utility heaters/coolers is synthesized for minimized total annualized cost. In contrast to existing works, (1) streams are not preclassified as hot/cold or high/low pressure, (2) pressure changes are allowed for streams with no net pressure change, (3) liquid‐vapor phase changes are allowed, and (4) phase‐based property correlations are used. Successful application of our approach to C3 splitting yields a nonintuitive configuration. Another application of an offshore natural gas liquefaction process is also studied. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2472–2485, 2018     

Proposed vertical integration of prior learning to support students undertaking Chemical Engineering Design

During academic session 2008–2009, the Department of Chemical Engineering, University of Strathclyde, changed Year 4 Chemical Engineering Design project teaching to include mixed groups from Bachelors and Masters programmes; team delivery and two separate components of design. This paper presents data for 408 students studying Chemical Engineering at the University of Strathclyde pre and post change; exploring the impact of these changes and highlighting potential for supported, vertically integrated learning programmes, across the first four years of teaching, to provide a framework fostering student confidence and autonomy. The impact of course restructuring indicates that Bachelors students’ aspirations are increased, with no detriment to Masters performance. Early years performance over this period is unchanged, allowing separate investigation of the changes made in 2008–2009. Gender basis analysis shows that male students’ performance is little affected, although the whole cohort fit shows a marked change due to the improved performance of low attaining female students. Post 2009 final performance shows direct correlation with Chemical Engineering Design mark, suggesting the latter may indicate final expected grades for given students. The study reveals widely applicable benefits for increased student motivation, managing expectation, and facilitating students’ utilisation and integration of knowledge gained during their studies.     

大规模复杂过程系统能量综合方法

针对过程系统工程的一个难点－－全过程系统能量综合,提出了“过程用能一致性原则”,从用能的角度上提高系统的集成性,将全过程系统的能量综合问题为相应的虚拟换热网络综合问题;并对大规模虚拟换热网络的求解进行了研究,提出了适用的分解策略;应用自行开发的过程用能夹点分析软件进行用能分析及换热网络匹配,实例分析节能效果显著。     

基于“卓越工程师”培养目标的化工原理精品课程改革探索与实践

化工原理是培养化工类专业高级应用型工程技术人才的一门核心专业基础课。为满足"卓越计划"和国家级特色学科建设的要求,提升学生的工程实践能力和创新能力,结合我校现阶段课程教学发展中存在的问题,我院从课程内容优化与整合、教师队伍建设、搭建开放性实践平台等方面对化工原理课程体系和教学方法进行改革,提高了课程教学质量,增强了学生工程意识和创新能力。     

Integrating compressors into heat exchanger networks above ambient temperature

Heat from compression processes is normally wasted to cooling water due to its low temperature or concerns about operability. The recoverable amount of heat can be enhanced by increasing the operating temperature of compressors. However, the compression work also increases under this condition. The integration of compressors into heat exchanger networks (HENs) is complex since both heat and work are involved, and the role of streams (as hot or cold streams), the utility demand, and the location of pinch points may change. A systematic graphical design procedure for above ambient HEN design including compressors was presented. The objective is to minimize exergy consumption to balance the complex heat‐work trade‐offs involved. Four theorems are proposed as the basis of the design procedure with certain well‐defined assumptions. It is found that the compression should be performed at pinch or ambient temperatures to achieve minimum exergy consumption. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3770–3785, 2015     

Desalination with a cascade of cross‐flow hollow fiber membrane distillation devices integrated with a heat exchanger

Cost‐efficient desalination technology was developed successfully by integrating a countercurrent cascade of the novel cross‐flow direct contact membrane distillation (DCMD) devices and solid polymeric hollow fiber‐based heat exchange devices. Simulations have been carried out for the whole DCMD cascade to project values of gained output ratio (GOR) as a function of the number of DCMD stages as well as other important factors in the cascade vis‐à‐vis the temperatures and flow rates of the incoming hot brine and cold distillate streams. The simulation results were verified with experimental results from cascades consisting of two to eight stages. The numerical simulator predicts a GOR of 12 when unequal flow rates of the incoming brine and distillate streams are used. An artificial sea water was concentrated eight times successfully when a countercurrent cascade composed of four stages of the DCMD modules and a heat exchanger was used during the DCMD process. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Design of mixed energy‐integrated batch process networks by Pseudo‐direct approach

In this article, a novel framework for the design of mixed (combined direct and indirect) integration for batch process systems is presented. The framework is based on the concept of pseudo‐direct energy integration (PDEI) which reformulates indirect integration as direct integration using pseudo‐process streams. Two algorithms are presented to achieve energy integration for batch processes operating cyclically (in a campaign mode). The first algorithm targets maximization of energy recovery and overcomes the limitations of some of the existing contributions for design of mixed integrated systems. The second algorithm provides a network reduction methodology to generate a cadre of integrated designs while exploring the trade‐off between capital (number of heat exchangers and storage units) and operating costs (utility consumption). The proposed framework is illustrated using a benchmark example of two hot and two cold streams. © 2017 American Institute of Chemical Engineers AIChE J, 63: 55–67, 2018     

Integrating expanders into heat exchanger networks above ambient temperature

The integration of expanders into heat exchanger networks (HENs) is a complex task since both heat and work are involved. In addition, the role of streams (as hot or cold), the utility demand, and the location of pinch points may change. With certain well‐defined conditions, four theorems are proposed for the integration of expanders into HENs above ambient temperature with the objective of minimizing exergy consumption. A straightforward graphical methodology for above ambient HENs design including expanders is developed on the basis of Grand Composite Curves (GCCs). It is concluded that to achieve a design with minimum exergy consumption, stream splitting may be applied and expansion should be done at pinch temperatures, hot utility temperature, or ambient temperature. In the majority of cases, however, and in line with the concept of Appropriate Placement from Pinch Analysis, expansion at pinch temperatures gives the minimum exergy consumption. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3404–3422, 2015     

An area targeting algorithm for the synthesis of heat exchanger networks

A new algorithm for the prediction of area requirements in heat exchanger networks (HEN) is presented. The method uses a diverse pinch diagram as a basis, similar to the one suggested by Rev and Fonyo (Chemical Engineering Science, 46 (7), 1623). A numerical application for a problem involving streams with significant differences in their heat transfer coefficient values is included to show how the proposed algorithm provides better estimates for minimum area requirements in HEN than the widely-used Bath formula and the algorithm by Rev and Fonyo.     

浅析应用计算机软件辅助化工原理课程设计教学

化工原理课程设计对培养学生工程实践能力非常重要。本文以化工原理课程设计中的精馏塔设计计算为例,介绍了当今一些流行的计算软件或应用软件在化工原理课程设计教学中的应用情况,并对这些软件的基本功能、特点进行剖析,分析使用软件进行教学的意义和存在的问题,以促进化工原理课程设计课程体系改革。     

通过连续精馏热量平衡 剖析进料热状态的合理选择

液体精馏是化工原理课程重要的单元操作之一。精馏的进料热状态影响到精馏工程中的多个方面。进料热状态的合理选择涉及了能量的合理利用问题。从连续精馏热量平衡的角度剖析进料热状态的合理选择,不仅能使学生深刻理解精馏理论原理,而且能够引导学生树立起技术经济的概念和争取工程最优化的工程观点。     

换热网络的同步综合设计

提出了换热网络的一种新的转运模型,以并串模式和非等温混合过程描述换热网络的热力学和经济性的总要求,不使用挟点分离、最小单元数等启发式规则,并允许交叉换热和不同物流间的膜传热系数与温差合理匹配.这一模型与优化模型相结合,自动产生换热网络,确定相应的最优公用工程费用、换热面积、换热器台数与冷热流间的匹配,其可行域由一集线性约束确定,鲁棒性很好,易于求解.该方法克服了换热网络的各种分步骤综合方法的缺陷(包括挟点技术、双温差法及相关数学规划方法).与文献上其它同步优化方法比较,具有模型简单、规模小、可算性强、初始化简易、计算结果可靠的优点.通过对文献中广泛使用的例题的检验,结果优于现有的其它方法.     

浅谈在《化工原理》教学中提高学生的积极性

化工原理是化工相关专业非常重要的课程,学生学习积极性的高低直接决定了化工原理的学习效果。本文对在化工原理教学过程中如何提高学生的积极性,从案例教学、增强学生的参与意识、利用现代化的教学方式、充分利用网络课程资源四方面进行了探讨。     

Supply and target based superstructure synthesis of heat and mass exchanger networks

This paper presents new methods for the optimisation of superstructures involving heat exchanger networks (HENs) and mass exchanger networks (MENs). The techniques developed in this study explore the use of key variables (namely supply temperatures/compositions and target temperatures/compositions) in HENs and MENs to define the intervals of superstructures. Such superstructures are modeled as mixed integer non linear programmes (MINLP) with the objective of minimisation of the total annual cost (TAC) for each network. The superstructures presented in this paper are derivatives of the interval and supply based superstructures (IBMS and SBS) developed previously. Two different superstructures are developed in this paper: the first uses the supply temperature/composition of hot/rich streams and the target temperature/composition of cold/lean streams (denoted supply and target based superstructure, S&TBS), while the second superstructure uses the target temperature/composition of hot/rich streams and the supply temperature of cold/lean streams (denoted target and supply based superstructure, T&SBS). Five HEN examples and three MEN examples are presented. The results obtained compare well with those in the literature.     

化工原理课程教学及考评方式改革探索——化工原理助教工作体会

在担任化工原理助教工作过程中,笔者参与了"四川大学化工原理课程教学创新改革的研究与探讨"的教改项目,就课堂教学方式、考试方法、成绩评定方法进行了一些有益于学生能力提高的尝试,获得了一些有益经验。     

互动与对比相结合强化传热与吸收的教学

通过互动与对比相结合的教学方式,在复习课中对《化工原理》课程中传热和吸收的异同点进行比较和概括总结,大大加深了学生对传热和吸收基本概念的理解和掌握程度,并提高了学生分析和解决问题的能力和对《化工原理》课程学习的积极性和主动性,还能创造良好的教学气氛。     

Work and heat integration—A new field in process synthesis and process systems engineering

The extension from heat integration and design of heat exchanger networks (HENs) to including heating, cooling, and power effects from pressure changing equipment has been referred to as work and heat integration and design of work and heat exchange networks (WHENs). This is an emerging research area in Process Synthesis and Process Systems Engineering, and WHENs represent a considerably more complex design task than HENs. A key challenge is the fact that temperature changes and pressure changes of process streams are interacting. Changes in inlet temperature to compressors and expanders resulting from heat integration will influence work consumption and production. Likewise, pressure changes by compression and expansion will change the temperatures of process streams, thus affecting heat integration. The state-of-the-art of this new research area including insight, methodologies, tools, opportunities, challenges, and literature is presented. Key aspects are illustrated by simple examples, whereas smaller case studies indicate potentials for industrial applications. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16477 2019