Step-wise synthesis of work exchange networks involving heat integration based on the transshipment model

Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy efficiency and the influence of lower carbon development.Since work exchange network is a significant part of energy recovery system,its optima design will have dramatically significant effect on energy consumption reduction in chemical process system.With an extension of the developed transshipment model in isothermal process,a novel step-wise methodology for synthesis of direct work exchange network(WEN)in adiabatic process involving heat integration is first proposed in this paper,where a nonlinear programming(NLP)model is formulated by regarding the minimum utility consumption as objective function and optimizing the initial WEN in accordance with the presented matching rules to get the optimized WEN configuration at first.Furthermore,we focus on the work exchange network synthesis with heat integration to attain the minimal total annual cost(TAC)with the introduction of heat-exchange equipment that is achieved by the following strategies in sequence:introducing heat-exchange equipment directly,adjusting the work quantity of the adjacent utility compressors or expanders,and approximating upper/lower pressure limits consequently to obtain considerable cost savings of expanders or compressors and work utility.Finally,a case taken from the literature is studied to illustrate the feasibility and effectiveness of the proposed method.

Synthesis of indirect work exchange networks considering both isothermal and adiabatic process together with exergy analysis

In this paper, an efficient methodology for synthesizing the indirect work exchange networks(WEN) considering isothermal process and adiabatic process respectively based on transshipment model is first proposed. In contrast with superstructure method, the transshipment model is easier to obtain the minimum utility consumption taken as the objective function and more convenient for us to attain the optimal network configuration for further minimizing the number of units. Different from division of temperature intervals in heat exchange networks,different pressure intervals are gained according to the maximum compression/expansion ratio in consideration of operating principles of indirect work exchangers and the characteristics of no pressure constraints for stream matches. The presented approach for WEN synthesis is a linear programming model applied to the isothermal process, but for indirect work exchange networks with adiabatic process, a nonlinear programming model needs establishing. Additionally, temperatures should be regarded as decision variables limited to the range between inlet and outlet temperatures in each sub-network. The constructed transshipment model can be solved first to get the minimum utility consumption and further to determine the minimum number of units by merging the adjacent pressure intervals on the basis of the proposed merging methods, which is proved to be effective through exergy analysis at the level of units structures. Finally, two cases are calculated to confirm it is dramatically feasible and effective that the optimal WEN configuration can be gained by the proposed method.

考虑多编组站转场作业的铁路枢纽车流组织优化

为提升多编组站铁路枢纽车流运转效率,首先,在分析枢纽内不同类型车流作业过程的基础上,以枢纽内列车进出站走行、车流改编、列车集结和转场扰动惩罚费用最小化为目标,构建数学模型;其次,根据接入枢纽铁路方向和场站接发列车能力,生成列车-编组站-调车系统初始匹配方案,进而利用转场-解集编能力对匹配方案进行调整与检验;再次,给出列车-编组站-调车系统匹配方案的双层编码方案,并利用嵌入替换-扰动-交叉操作的异步循环更新过程,完成匹配方案的群体寻优;最后,设计仿真试验对所提模型与算法进行测试.结果表明:所提方法能够完成对多编组站的合理分工,5组试验测试分别在369、422、516、641、763 s的计算时间内得到列车-编组站-调车系统匹配方案,在优化分工后的车流组织方案中,转场货车占到解车流比例均能稳定在20%,从而达到减少转场货车数、降低车流组织成本的目的.

基于转运模型的功交换网络综合

功交换网络作为能量回收系统的重要组成部分,其设计水平的高低对过程系统的能耗将有着重要的影响,但是目前对功网络综合的研究仍处于理论研究的起步阶段。本文根据功级联分析,首次提出了一种基于转运模型进行功交换网络综合的新方法。该方法以公用工程用量最小为目标函数,建立了适用于等温过程的LP数学模型。通过提出构造低压流股压力中间值的策略,解决直接式功交换匹配过程中压力约束的限制,在每个压力间隔内寻求可行流股匹配,从而得到功交换的初始网络结构;再根据所提的合并相邻压力间隔的策略,进一步减少公用工程用量,进而达到优化网络结构的目的。最后通过实例计算,验证了本文方法的可行性及有效性。

带多编组站作业分工的铁路枢纽列流、车流组织优化

为优化多编组站铁路枢纽车流组织,均衡各调车系统解编能力的利用,首先,考虑枢纽内各场站改编作业能力和瓶颈区间线路通行能力限制,将列流、车流组织成本和调车系统能力利用率均衡偏差最小作为优化目标,构建带编组站分工的列流、车流组织优化模型。其次,根据场站接发列车能力生成初始方案,依据瓶颈区间线路通行-场站解集编能力调整检验;在此基础上,设计双层整数编码对匹配方案进行表述,给出匹配方案五步更新过程,并利用此过程完成匹配方案的群体迭代寻优。最后,设计实验场景,利用所提出的方法进行求解,并同不考虑编组站分工的列流、车流组织方案进行比对分析。结果显示,考虑编组站作业分工的列流、车流组织方案成本降低了9.5%,调车系统解编能力利用率均衡偏差降低了16.6%。