具有最简结构水回用网络的优化

当前对水回用网络的研究主要集中在如何构造新鲜水量最小的水网络, 却忽视了该水网络的不唯一性.为了降低水回用网络的费用,应考虑水网络的最简结构.今用连接数的概念来描述用水网络的结构复杂性.连接数就是新鲜水道与过程、过程与过程、过程与废水道之间连接个数的总和.今以最小新鲜水量和网络连接数为目标,在网络超结构的基础上,建立了多杂质水回用网络优化的数学模型.用该模型确定的用水网络,具有最小新鲜水用量和最简结构,因而具有很好的经济性.最后通过实例说明了本方法的有效性.     

基于最大水回用规则的遗传算法用水网络优化

超结构用水网络规模大、结构复杂、求解比较困难。本文提出了基于最大水回用规则的遗传算法用水网络优化设计方法,该方法按出口浓度的单调性进行排列,使进口浓度或出口浓度达最大值以确定用水量,简化了用水网络超结构及数学模型。以最小新鲜水量为目标,以过程之间回用水量和废水量为基因,对简化后的用水网络运用遗传算法进行了优化设计。遗传算法采用浮点数编码方法,运用了算术交叉技术和种群间交叉技术。计算实例表明,本文所提方法可行,能利用最大水回用规则简化用水网络,并快速求出其最优解。     

考虑环境及处理单元流股回用的多性质用水网络集成

水资源的日益匮乏和更为严格的废水排放法律法规促使过程工业必须重视节水减排问题,而传统的用水网络综合仅将杂质浓度作为约束物料回用的限制因素,忽略流股的性质或功能对流股回用的影响,不足以反映实际的工业生产要求。因此,开展用水网络的多性质集成问题研究具有重要的现实意义。本文在考虑环境问题的多性质用水集成超结构模型基础上,增加了对废水流股性质处理中部分流股依次回用给阱单元使用的过程。该方法以最小年度总费用为目标函数,建立了考虑环境和过程流股性质的直接回用及经过处理单元后流股回用的混合整数非线性规划(MINLP)模型,并将其用于实例计算,结果表明本文方法在降低年度总费用的同时还减少了新鲜水使用量及废水排放量,验证了本文方法的有效性及优越性。     

水夹点分析与数学规划法相结合的用水网络优化设计

提出了水夹点分析和数学规划法相结合的用水网络最优设计法。水夹点分析基于对过程用水的理解,获得新鲜水用量目标并给出用水网络设计的基本规则。在此基础上建立过程使用新鲜水、排放废水和回用的各种可能匹配方案的用水网络超结构及其MINLP模型。既避免了用水夹点综合设计用水网络得不到真正意义上的最优解,又在一定程度上防止超结构规模过大,MINLP维数太高,求解困难。采用通用代数建模系统GAMS得到用水网络最优设计方案。文献中的应用实例表明,本文所提方法可充分发挥水夹点分析确定新鲜水用量或回用结构的简洁实用性和超结构MINLP寻求最佳方案的优点。     

污水回用网络优化设计的研究

在工业生产的各个用水过程中会产生大量污水，使污水最小化的一个有效的方法就是设计污水回用网络，以便使污水得到最大程度的回用，这样在满足用水要求的同时使新鲜水消耗最少，利用自适应模拟退火遗传算法对用水网络进行最优设计。     

生物燃料乙醇生产成本优化之中水回用的研究

在燃料乙醇产业上应用中水回用措施可节水、节能,减少对环境的影响,同时又可降低生产成本,具有良好的经济及社会效益。本文通过影响生产成本因素分析,以创新的思维寻求降低生产成本的新途径,深入研究中水回用在燃料乙醇生产中应用的可行性。     

简捷法确定提纯回用氢网络目标值

与只考虑直接回用的氢网络相比,具有提纯单元的氢网络能显著减少新鲜氢气的消耗量,但其设计及求解提纯目标值过程均更为复杂。对于单杂质、提纯单元采用固定浓度模型的提纯回用氢网络,结合此类网络的特点,提出了一种简捷法确定网络目标值。首先假设提纯后氢物流量足够大,由此得出初始提纯夹点。当初始夹点估算正确时,由夹点之下的需求物流和源物流的流量与杂质质量衡算即可得出提纯回用氢网络的目标值;当初始夹点估算不正确时,可以第一次计算结果为基础判断得出正确夹点,再增加一步简单计算,也可得到提纯回用目标值。计算实例表明本文方法计算简单且有效。     

多污染因子水配合回用网络分析

综合利用水资源、优化相应网络、降低用水量与废水量排放量是当前我国各行业的迫切需求。在回用水网络设计与分析中,多污染因子水系统的优化向来是其中的关键。在用水污染物传质模型的基础上,提出了适用于单或多污染因子水系统,根据各用水操作进出口极限条件进行水流股配合回用的水网络优化方法,并以此方法对某石化企业炼油事业部含油水系统用排水网络进行优化设计,达到考虑单污染因子节水24.29%~33.30%,多污染因子节水17.76%的效果。该方法大大简化了水网络设计的计算,为石化行业水资源利用的优化提供了重要的依据。     

化工厂排放水的出水与回用

采用水解酸化-接触氧化-超滤处理化工厂排放水.结果表明,水解酸化、接触氧化和超滤能有效去除污水中的有机物、NH3-N、SS和Cl^-等.处理出水能够达到《再生水用作冷却用水的水质标准》中的循环冷却水标准、《国家污水综合排放标准》GB8978-1996中的一级排放标准并在生产中得到回用,从而节省了大量的自来水,产生了良好的经济效益和环境效益.     

水系统集成优化方案的博弈分析与评价方法

对水系统集成优化方案的分析和决策需要考虑新鲜水用量、用水系统的柔性和用水网络结构的复杂程度等方面。水网络优化设计方案的确定一般需要在这三者之间进行折中和协调,属于多目标优化问题。为了综合考虑新鲜水消耗量和网络结构复杂程度等指标,并定量分析和确定水网络的优化设计方案,本文提出一种基于博弈分析的水网络优化方案的定量分析方法。以具有中间水道水网络优化设计方案的决策为例,采用本文方法进行了优化设计方案的分析与评价。研究表明：该定量分析和评价用水网络的方法可以合理地评价用水网络的设计方案,该方法可用于定量确定水系统优化问题中的多目标优化方案,可为水系统优化集成方案的确定提供分析依据和指导。     

多组分用水网络的整体优化设计策略

针对较复杂的多组分用水过程,提出了基于序贯操作模型的整体优化设计策略对于一个给定的操作序列,假定排在操作i之前的所有操作的出口水流都是操作i的水源,在此前提下建立了多组分用水过程的序贯操作模型.这样,多组分用水网络的设计问题可表达为一个双层优化的非线性规划,内层用来寻找给定操作序列情况下的最优解,外层则是在所有可能的操作序列中搜索最优序列.通过对一个例子进行求解,说明了所提出的新方法.     

分阶段线性规划法快速设计含有多种污染物的用水网络

针对含有多种污染物用水网络的设计问题,提出了一种新方法.该方法先基于各个用水过程的污染物最大出口浓度对过程排序,然后采用GAMS(general algebraic modeling system)语言建立线性规划模型,依次对序列中的每个过程的废水回用方案进行优化计算,以确定出其最小新鲜水用量和来自前驱的废水回用量.该方法虽然不能保证所得解的全局最优性,但它能快速地找到最优或近似最优解,而且方法简单.     

多杂质体系间歇过程用水网络优化

对多杂质体系完全间歇过程用水网络优化进行了研究,建立了用水网络超结构和非线性规划数学模型,利用中间储罐跨越时间约束,设置用水过程流量上下限以加速收敛。首先确定关键杂质,并将关键杂质浓度最大的水源直接排往废水,获得简化的用水网络超结构;其次,运用GAMS求解,得到最小新鲜水量、废水量、中间储罐数目及优化的用水网络结构。实例研究证明本文提出的方法可行,并能以较少周期获得优化的网络结构,同时可以减少中间储罐数目。     

A heuristic design method for batch water-using networks of multiple contaminants with regeneration unit

This work develops a heuristic method for the design of batch water-using networks of multiple contaminants with regeneration unit based on the concepts of concentration potential. A water-using network involving regeneration unit can be formed by adding the regenerated stream(s) into the network involving reuse only. In the design procedure of the network operated in a single batch mode, time is taken as the primary factor and concentration potentials as the secondary one. For the networks operated in a repeated mode, the design procedure is similar to that for continuous processes, besides designing the storage tanks with the rules proposed. Continuous regeneration unit is selected in this work. With the proposed method, the network structure corresponding to the minimum freshwater consumption can be obtained. It is shown that the method proposed in this article is simple, effective and has clear engineering meaning.     

MILP-based initialization strategies for the optimal design of water-using networks

The optimal design of water-using systems involves necessarily the exploitation of all possible water reuse and recycling alternatives. The general problem can be formulated as a non-convex nonlinear program (NLP), but due to the presence of bilinear terms, it may be difficult for local optimization solvers to attain global optimal solutions. To overcome this difficulty, this paper presents two mixed integer linear programming (MILP)-based procedures to generate a few structurally different starting points for the NLP. In both, the problem is decomposed into calculation stages by assuming that the water streams progress in series through the water-using units, with the binary variables selecting which unit belongs to a certain stage. Their main difference concerns the way fixed flowrate units are handled, either separately or in conjunction with a fixed load operation, since the former comprise a linear subsystem. The two algorithms are compared to a closely related LP-based method taken from the literature and to the one employed by the global optimization solver BARON. The results from a large set of example problems confirm their effectiveness in avoiding local solutions despite the small number of starting points. In contrast to the previous method they are easily scalable and, for some of the larger problems, could find better solutions than BARON with significantly fewer computational resources. The results have also shown that the option of tackling one unit at a time is the most favorable.     

间歇用水系统中废水回用与集中再生处理的调度优化设计方法

针对间歇用水系统建立了废水回用与废水集中再生处理协调运行和调度优化的数学规划设计模型。在多周期运行条件下,以保证循环周期中水系统最优运行为目标,提出了消除不同操作周期下储罐中水量和浓度波动的多周期反算求解策略,并确定了多周期操作下优化的用水网络。通过单杂质间歇用水系统实例阐明了所提出方法的有效性,为具有废水集中再生处理的间歇用水系统从启动到稳定的多周期操作和设计提供依据。     

Comparison of global optimization algorithms for the design of water-using networks

We address a special class of bilinear process network problems with global optimization algorithms iterating between a lower bound provided by a mixed-integer linear programming (MILP) formulation and an upper bound given by the solution of the original nonlinear problem (NLP) with a local solver. Two conceptually different relaxation approaches are tested, piecewise McCormick envelopes and multiparametric disaggregation, each considered in two variants according to the choice of variables to partition/parameterize. The four complete MILP formulations are derived from disjunctive programming models followed by convex hull reformulations. The results on a set of test problems from the literature show that the algorithm relying on multiparametric disaggregation with parameterization of the concentrations is the best performer, primarily due to a logarithmic as opposed to linear increase in problem size with the number of partitions. The algorithms are also compared to the commercial solvers BARON and GloMIQO through performance profiles.     

A graphical technique for the design of water-using networks in batch processes

This paper presents a graphical technique for the design of water-using networks in batch plants. Water integration is achieved by exploiting all possibilities of water reuse/recycle to minimize not only freshwater consumption, but also wastewater generation. Since time limitation for unmatched operating periods may be the primary barrier to the integration in batch processes, the installation of storage facilities is quite common to enhance the water recovery. For that reason, the cost in terms of storage facilities becomes another issue to be considered. This work is focused on network design, like the second stage of conventional pinch analyses. Some useful concepts and principles addressed in literatures are adopted to help the design of batch water network and to ensure the maximum recovery, thus the utility usage, the network structure and the storage policy can be obtained through the analysis. Once the freshwater expenditure is determined, workable ways are sought to cut the number of storage tanks and they also reduce the network complexity. In the context of this paper, a hybrid system that includes different type of water-using operations with distinct operating modes is taken into account to display the versatility of proposed approach. Furthermore, considering the fact that sometimes water reuse/recycle between certain operations is not allowed to prevent operational problems, the action of network design should be more deliberate owing to additional restraints. Therefore, the potential for water integration may be diminished, which means a less amount of water recovery. Finally, an illustrative example is provided to amplify the application of proposed approach. Like most graphical techniques, the presented work is restricted to a single key contaminant.     

Heuristic evolution strategies for simplifying water-using networks with multiple contaminants

In designing a realistic water-using network with more than one contaminant, it is often desirable to obtain a simple structure so as to achieve high levels of controllability, operability, and safety. Based on any given preliminary design, the proposed heuristic evolution procedure can be systematically applied to produce an improved network with fewer interconnections, less total throughput and near minimum freshwater usage. Specifically, the minimum interconnection number is first targeted on the basis of graph theory and, then, three basic evolution strategies, i.e., loop breakage, two-source shift and path relaxation, can be utilized to strive for the number target. The required calculations in this procedure can be easily realized with Microsoft Office Excel or a hand calculator. Two examples are presented in this paper to illustrate the implementation steps and to demonstrate the effectiveness of the proposed approach.     

Water network design with stochastic optimization approach

Water network (called also water allocation) problem has been addressed in more than 200 papers to date – see recent reviews by Je?owski (2010) and Foo (2009). Though various solution methods have been developed they all have some limitations. This paper addresses water usage network with regeneration processes. Multiple contaminants and two types of water using processes are taken into regard. Simultaneous one stage optimization method was developed to synthesize the network. In order to solve complex MINLP formulation we propose to apply meta-heuristic optimization – adaptive random search method.The paper contains detailed solution algorithm. Several examples with specific features are solved to show efficiency and flexibility of the approach.