基于自组织Petri Net的间歇过程换热网络优化设计

根据热级联分析法的基本思想,在优化设计连续过程换热网络的自组织PetriNet模型中,引入时间库所表示间歇过程时间,使其适合于优化设计间歇过程换热网络,拓展了PetriNet对时间的表示形式,有利于对系统可达性进行研究。另外,根据垂直匹配原则,对换热网络夹点匹配的分流问题进行了研究,建立了综合考虑夹点规则的数学公式,有利于快速准确地进行夹点处流股的分流匹配。通过实例计算说明了提出方法的可行性和有效性。     

带有热储罐的间歇过程换热网络综合

间歇过程流股对时间的依赖性增加了其换热网络综合的难度。提出了一种采用间接换热进行换热网络综合的方法,且考虑了直接换热,同时提出了合并热储罐的方法,并利用热储罐的特点合并间接换热中的换热器,用以减少设备费用,以热储罐中介质的温度为变量以年度总费用最小为目标函数建立非线性规划数学模型,确定热储罐内介质温度,最后将该方法应用于实例中证明此方法的有效性。     

换热网络的新设计方法—双温差法

本文从热力学原理、设计准则及优化方法等几方面介绍了换热网络的一种新设计法——双温差法的最新发展状况。由于该法采取了EMAT≤HRAT的设计准则,较传统的单温差法设计的网络具有较少的分枝、旁路及混合等物流数,这不仅减少了网络的单元数,降低了其复杂性,而且换热面积也可能随之降低。这是目前换热网络设计的一种较理想的方法。     

间歇过程的热集成

用某啤酒厂啤酒酿造生产流程作为间歇过程的一个实例, 利用夹点分析方法对该过程的用能状况进行分析、诊断, 探讨了在间歇过程中利用热集成原理进行节能改造的方法     

用虚拟温度法进行优化间歇过程换热网络

间歇过程在生产中高度灵活,使其在化工生产中所占的比重越来越大。研究了用虚拟温度法得到的间歇过程换热网络,寻找各时间间隔的子换热器网络内的热负荷回路,以一定的规则断开回路,对总换热器网络进行结构优化,使得到的总换热网络的换热单元数目减少。     

换热网络集成与优化研究进展

首先回顾了上世纪80年代初期提出的以夹点技术和数学规划法为代表的经典换热网络集成优化方法,进而分别论述了近期换热网络集成优化的主要进展,包括考虑压降、结垢和换热器详细设计等实际问题的换热网络集成优化方法;针对不断升级的环境问题,考虑全生命周期分析、二氧化碳捕集和水系统的换热器网络集成优化方法;以及为进一步提升能量利用效率,将换热网络的边界扩展至多个装置,甚至工业园区的能量系统优化方法。最后展望了今后换热网络集成优化的发展趋势与方向。     

苯乙烯装置换热网络的集成与分析

采用夹点技术对已采用蒸汽凝液余热部分回收的苯乙烯装置进行了能量利用分析,分析表明:现行换热网络需加热公用工程22024.8 kW,通过对换热网络的夹点分析和计算,可得该装置的最小加热公用工程为21489.89 kW,最小冷却公用工程为27064.85 kW.在充分考虑了现行换热网络已有的结构和特点后,提出了最大限度的回收能量的换热网络改造方案.     

夹点技术在换热网络优化中的应用

换热网络的优化设计是石化行业生产过程中经常遇到的问题,夹点技术在换热网络优化中有着重要的地位。本文简要阐述了换热网络的基本思想以及夹点技术在换热网络中的应用,用一个简单例子说明了如何运用问题表格法来确定换热网络的夹点,并介绍了夹点技术存在的局限性。     

考虑压降的换热网络研究

在换热网络综合设计中,压降是一重要影响因素。安装泵、压缩机等设备可克服流体流动过程中的阻力损失,这些动力设备的投资费用和能耗费用(简称动力费用)是换热网络总投资的重要部分,所以年总费用目标函数中应包括公用工程费用、换热器投资费用和动力费用,这三者应作权衡处理来决定最优夹点温差ΔTmin,以得到年总费用最小、结构更优化的换热网络。     

基于换热网络集成的二甲苯分离精馏塔参数优化

精馏是化工过程中重要的耗能设备,其产品温度的改变将影响换热网络的集成.针对二甲苯分离吸附的实际生产过程,利用复合曲线系统分析精馏塔DA604塔压增大至170kPa及230kPa后塔顶和塔底产品流股温度改变对换热网络的集成和公用工程消耗量的影响,可实现精馏塔操作与换热网络的同步集成,相较与之前只考虑流股温位对换热网络的影响更加全面.结果表明,该精馏塔的塔压由110kPa增至170kPa时,系统的冷却公用工程用量增大1765.0kW,加热公用工程量减少1948.5kW,无需消耗加热公用工程;压力由110kPa增加至230kPa时,系统冷却公用工程用量增大4964.1kW,加热公用工程用量节省共计8172.4kW,此时加热公用工程用量减小为0且可在高温段向外界供给6223.9kW热量.该分析结果与夹点法的计算结果相同,由该结果可得普适性结论,当精馏塔塔顶塔底出口物流均为源时,增大塔压,系统加热公用工程减小,冷却公用工程增加,整体上有利于系统的节能.     

间歇化工过程热集成研究进展

间歇化工过程热集成问题的研究能够促进过程系统的可持续发展并且提高产业经济性和技术竞争力,顺应了化工发展大环境。本文介绍了以系统综合优化为目标的间歇化工过程热集成研究的发展现状,整理了早期研究的三大通用图解模型,并讨论和比较了在建模求解过程中常见算法。总结了当前研究的重点在换热网络设计优化、热储罐系统和考虑调度的热集成三个方面,并评述了与之相关的进展、瓶颈和研究意义。指出了热集成问题已成为当前间歇化工过程的研究热点,其中热集成和生产调度的协同优化十分必要,能够从系统全局的角度上给出优化方案。但由于间歇化工过程中存在较多的不确定性和约束条件,增加了热集成的研究难度,因此对间歇化工过程优化设计提出了更高的要求。     

多管程换热器网络的最小温差分析与夹点设计

在实际生产过程中,多管程换热器广泛应用,其中既存在逆流换热也存在并流换热。针对多管程换热器网络中并流换热与逆流换热时换热温差对夹点特性尤其是换热网络综合的影响,定量分析最小温差的选择与夹点特性及其总费用的关系。兼顾管程数目的选择以及换热网络总费用两方面因素,以年度化总费用最低为目标,优化求解多管程换热器网络的最小温差。然后,将求得的最小温差作为夹点温差,遵循夹点设计原则综合换热网络。同时,计算得出多管程换热器网络的F_T修正因子,并对结果进行分析。最后,结合示例对比分析求解结果,证明方法的有效性。     

A computerized and integrated approach for heat exchanger network design in multipurpose batch plants

Significant savings in the utility cost of batch plants can be obtained by heat integration. In this study, an integrated mathematical programming approach is developed for the determination of the cost optimal heat exchanger network for multipurpose batch chemical plants. A single step, interactive computer program (BatcHEN) which is developed for the determination of the campaigns (i.e. the set of products which can be produced simultaneously), the heat exchange areas of all possible heat exchangers in the campaigns and finally the heat exchanger network are all discussed. A matrix search algorithm is used for the determination of the campaigns. Heat exchange areas for the possible heat exchangers are found by solving a nonlinear optimization model with a grid search algorithm. Finally the heat exchanger network optimization is modeled as a mixed integer linear programming problem and then solved by the modeling and optimization software GAMS/XA.     

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     

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     

考虑管壳式换热器传热强化的换热网络综合研究进展

换热器传热强化在换热网络中的应用可以解决现有换热网络改造中的瓶颈问题,在热回收系统配置没有过多结构改造的条件下,可以达到明显的节能及降低成本的目的;同时,在换热网络设计中,换热器传热强化技术的应用可以降低设备投资,实现更好的经济效果。本文首先通过文献检索数据说明了在换热网络改造和设计中考虑传热强化技术的研究在近5年得到了研究者的关注。然后概述了管壳式换热器传热强化的基本原理及主要方式,分析了传热强化技术的应用对换热器传热性能的影响,系统总结了管壳式换热器传热强化技术的分类和强化效果。进一步从设计和改造两个方面,对换热网络优化中考虑管壳式换热器传热强化的应用研究进行了综述,展示了传热强化对换热网络设计和改造的效果和优势。最后对下一步的研究进行了展望,指出可进一步探究换热器传热强化设备几何尺寸和换热网络同步优化、传热强化和换热器详细设计同步优化等。     

基于热损失的换热网络夹点设计法

现行的换热网络目标方法,在进行换热网络价格估算时,未考虑热物流的热损失。在真实的设计中,换热器壳体保温后仍与环境温度相差较大,则其热损失不可忽略。文章提出了一个新的基于热损失的换热网络夹点设计法,该方法首先以综合费用最小为目标确定出最小温差,然后建立问题表格确定出夹点位置及最小公用工程消耗,最后再进行换热网络设计。文中采用某石油常减压换热网络系统为典型算例对该方法的前两步进行了分析研究,论证了该方法的必要性及可行性。结果表明:该方法与基本Linnhoff夹点技术法估算的投资费用有较大的差距之外,在一定的最小温差下,其与基本Linnhoff夹点技术法确定的夹点位置不同,公用工程消耗也有较大的差距。     

A new approach for scheduling of multipurpose batch processes with unlimited intermediate storage policy

The increasing demand of goods, the high competitiveness in the global marketplace as well as the need to minimize the ecological footprint lead multipurpose batch process industries to seek ways to maximize their productivity with a simultaneous reduction of raw materials and utility consumption and efficient use of processing units. Optimal scheduling of their processes can lead facilities towards this direction. Although a great number of mathematical models have been developed for such scheduling, they may still lead to large model sizes and computational time. In this work, we develop two novel mathematical models using the unit-specific event-based modelling approach in which consumption and production tasks related to the same states are allowed to take place at the same event points. The computational results demonstrate that both proposed mathematical models reduce the number of event points required. The proposed unit-specific event-based model is the most efficient since it both requires a smaller number of event points and significantly less computational time in most cases especially for those examples which are computationally expensive from existing models.