Sequential methodology for integrated optimization of energy and water use during batch process scheduling

Though commonly encountered in practice, energy and water minimization simultaneously during batch process scheduling has been largely neglected in literature. In this paper, we present a novel framework for incorporating simultaneous energy and water minimization in batch process scheduling. The overall problem is decomposed into three parts - scheduling, heat integration, and water reuse optimization - and solved sequentially. Our approach is based on the precept that in any production plant, utilities (energy and water) consumption is subordinate to the production target. Hence, batch scheduling is solved first to meet an economic objective function. Next, alternate schedules are generated through a stochastic search-based integer cut procedure. For each resulting schedule, minimum energy and water reuse targets are established and networks identified. As illustrated using two well-known case studies, a key feature of this approach is its ability to handle problems that are too complex to be solved using simultaneous methods.     

A stepwise optimal design of water network☆

In order to take full advantage of regeneration process to reduce fresh water consumption and avoid the accumu-lation of trace contaminants, regeneration reuse and regeneration recycle should be distinctive. A stepwise opti-mal design for water network is developed to simplify solution procedures for the formulated MINLP problem. In this paper, a feasible water reuse network framework is generated. Some heuristic rules from water reuse net-work are used to guide the placement of regeneration process. Then the outlet stream of regeneration process is considered as new water source. Regeneration reuse network structure is obtained through an iterative optimal procedure by taking the insights from reuse water network structure. Furthermore, regeneration recycle is only utilized to eliminate fresh water usage for processes in which regeneration reuse is impossible. Compared with the results obtained by relevant researches for the same example, the present method not only provides an appro-priate regeneration reuse water network with minimum fresh water and regenerated water flow rate but also sug-gests a water network involving regeneration recycle with minimum recycle water flow rate. The design can utilize reuse, regeneration reuse and regeneration recycle step by step with minor water network structure change to achieve better flexibility. It can satisfy different demands for new plants and modernization of existing plants. ? 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.     

具有中水道的过程工业水网络设计方法

提出了一种具有中水道的过程工业水网络设计方法,该方法强调合理地确定第一中水道位置的重要性,运用一种确定某一中水道回用到它的后续过程的优先顺序的新方法精确地完成了从任意一个中水道到它的后续过程的水分配,并在设计步骤中给出了一些可能出现情况的处理方法.实例求解结果表明,具有中水道的水网络能明显减少新鲜水的消费,设计方法简便易行.     

Synthesis of robust water reuse networks for single-component retrofit problems using symmetric fuzzy linear programming

Water integration techniques can be used to minimize the utility water consumption and effluent generation of process plants through the implementation of reuse or recycle networks. There are a number of graphical and mathematical programming techniques available for the synthesis of such water reuse networks. However, effective use of these methods requires the availability of reliable process data, which in reality might be difficult to acquire. This paper describes a procedure for the synthesis of robust water reuse networks from imprecise data using symmetric fuzzy linear programming (SFLP). Two model variants, one based on mass exchange units and the other on source/sink allocation, are presented. Each variant is illustrated with a numerical example.     

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。     

Optimal interplant water networks for industrial zones: Addressing interconnectivity options through pipeline merging

To date, alternative design options that exist for interconnecting transmission and distribution networks have not been considered in water reuse network synthesis. Existing approaches that do incorporate piping expenses in the design of interplant water networks assign a separate pipeline for every water allocation. However, merging together common pipeline regions for the transmission of water from, or to nearby but different processing facility destinations may improve the overall water network performance not only in terms of cost efficiency but also in terms of complexity. A novel approach that is capable of accounting for pipeline merging scenarios that could exist within a water reuse network is introduced in this article. Two different pipeline branching possibilities have been introduced in this work, for the purpose of merging: (1) forward branching and (2) backward branching. The approach is implemented for the design of interplant water networks considering direct water reuse amongst several coexisting processing facilities within an industrial zone. A case study is presented to illustrate the application of the approach and its benefits. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2853–2874, 2014     

Optimal design of integrated agricultural water networks

This paper presents a mathematical programming model for the optimal design of water networks in the agriculture. The proposed model is based on a new superstructure that includes all configurations in terms of use, reuse and regeneration of water in a field constituted by a number of croplands. The model also includes the allocation of pipelines, pumps and storage tanks in different irrigation periods. The objective function consists in maximizing the annual profit that is formed by the economic incomes owing to the crop sell minus the costs for fresh water, fertilizer, storage tanks, treatment units, piping and pumping. The proposed multi-period optimization problem is formulated as a mixed integer non-linear programming formulation, which was applied to a case study to demonstrate the economic, environmental and social benefits that can be obtained.     

Economic optimization of the water reuse network in batch process industries

Water reuse has proved to be an efficient way to reduce freshwater demand and wastewater generation in process industries. In this paper, a methodology for minimizing the costs associated to water management in batch process industries is presented. This work is based on a previous methodology for freshwater demand minimization, which has been extended to the economical aspects of water management: cost associated to freshwater supply and conditioning, wastewater treatment and disposal, as well as water reuse network investment and operation costs. Water reuse network design is optimized from the economical point of view, minimizing the operation and investment costs associated to the water use.     

考虑非等温混合的能量集成多杂质水网络优化设计

提出了一种分步综合多杂质体系水网络和换热网络的新方法。对于水网络,考虑进入操作单元的新鲜水与回用水之间的非等温混合,确保流股间的直接热回收;对于换热网络,可以只考虑水网络中的新鲜水和回用水流股之间的换热匹配。采用无进化次数的改进粒子群算法对本文建立的多杂质体系水网络非线性模型和换热网络混合整数非线性模型进行求解。实例表明,与不考虑非等温混合时比较,考虑非等温混合时的最优网络结构更简单,且年度总费用要节省2.4%。因此,本文提出的方法在实际生产中有较好的可行性和有效性。     

Synthesis of water networks for industrial parks considering inter-plant allocation

Since an industrial park is a cluster of multiple company individuals, there is requirement to develop specific reuse strategies so as to improve the utilization of resources across plants. This article presents a ‘plant-based’ mode respecting to the water allocation problem within industrial parks. In the mode, mixers and splitters are involved to present the mixing, conveying and splitting operations for reusing streams across plants. Such that, the mixing possibilities can also be investigated and many redundant solutions can be avoided by considering the number limit of inter-plant stream connections at the building stage of network superstructures. On base of this mode, both direct and mixed (direct–indirect) integration scenarios are studied in this study. Superstructures are established and mathematically formulated aiming to minimum fresh water consumption as well as the total annualized cost. At last, three integration cases are explored based on an example from literature for illustration.     

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。     

Optimal design of water pipeline networks for the development of shale gas resources

One of the major concerns in shale gas production is water management. Millions of gallons of water are injected to fracture each well and a significant amount returns to the surface as flowback. Operators are increasingly reusing flowback to reduce freshwater consumption and impaired water disposal. Because of this, networks of water pipelines in U.S. shales are growing fast. This work is aimed at addressing the optimal planning of shale gas operations in multiple wellpads together with the design of water distribution networks (WDN). We propose a multiperiod mixed-integer linear programming model to solve the challenging stay-or-mobilize trade-off. The proposed model permits to schedule operations at a detailed level, accounting for the WDN required to maximize the reuse of impaired water. We present illustrative examples involving up to 20 pads, 4 frac-crews, and 100 wells developed over 1 year, showing that the design of the WDN can be effectively optimized.     

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.     

Simulation of mass exchange networks using modified genetic algorithms

The optimum water usage network leads to both a minimum of freshwater consumption and a minimum of generated wastewater. This work is to develop a mass-exchange networks (MENs) module for a minimum freshwater usage target. This module works as an interface to retrieve supplemental data of chemical processes from a process simulator and to communicate this to the genetic algorithm optimizer. A reuse system and a regeneration/recyclingsystem with a single contaminant are considered as approaches for freshwater minimization. In the formulated model, as mixed integer nonlinear programming (MINLP), all of the variables are divided into independent and dependent variables. The values of independent variables come from randomization, whereas the values of dependent variables come from simultaneous solutions of a set of equality constraints after assigning the values of independent variables. This method is applied to the steps of initialization, crossover and mutation. The MENs module is validated with a tricresylphosphate process consisting of five unit operations. Water is used to remove a fixed content of cresol. From the result, the module gives a reliable solution for freshwater minimization, which can satisfy mass balance and constraints. The results show that reuse and regeneration/recycling strategies can reduce freshwater consumption, including wastewater generated. Reuse cannot decrease the mass load of the contaminant, while regeneration/recycling can. In addition, regeneration requires less freshwater than the reuse process.     

Emerging R&D on membranes and systems for water reuse and desalination

Sustainable production of clean water is a global challenge. While we firmly believe that membrane technologies are one of the most promising solutions to tackle the global water challenges, one must reduce their energy consumption and fouling propensity for broad sustainable applications. In addition, different membranes face various challenges in their specific applications during long-term operations. In this short review,we will summarize the recent progresses in emerging membrane technologies and system integration to advance and sustain water reuse and desalination with discussion on their challenges and perspectives.     

Studies on simultaneous energy and water minimisation—Part I: Systems with no water re-use

This paper addresses the simultaneous management of energy and water. A new systematic methodology has been developed for targeting and design that simultaneously minimises the requirements of energy and water. Using this new approach, the design of a water system for maximum energy recovery can be achieved, taking into account the mixing opportunities offered by water networks, while maintaining the water quality to processes in terms of contamination. Direct and indirect energy recovery are analysed and a strategy developed to decrease the number of heat transfer units based on the generation of separate systems and non-isothermal stream mixing. Initially, the analysis is restricted to no water re-use.     

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.     

采用迭代方法设计具有再生再利用/循环的单杂质用水系统

具有再生再利用/循环利用的水网络与只有再利用的水网络不同之处在于前者增加了再生水流。如能确定再生水流的浓度和流量并将之加到只考虑再利用的水网络中,即可构成具有再生再利用/循环利用的水网络。在上述思想基础上提出一种迭代法设计具有再生再利用/循环利用的水网络。该方法既可以解决给定移除率（removal ratio,RR）问题,又可以解决固定再生浓度问题。对RR问题,根据水网络及再生过程的特点估算出初始再生水流浓度,再生水流的量待定。将所得再生水流加到只考虑再利用的网络中构成具有再生过程的水网络。设计上述水网络,可以得出新的再生水流的量及浓度。当相邻两次再生浓度之差小于给定值时迭代结束。对RR问题,通常只需几次迭代即可得出最终设计;对于固定再生浓度问题,只需一次迭代即可得出最终设计。设计中考虑了影响水网络设计总费用的新鲜水用量、再生水用量和杂质再生负荷3个主要参数。对文献中几个实例的研究表明,本文方法得到的设计与文献中的设计相当,而设计步骤比文献中的简单。     

Integrated concepts in water reuse: managing global water needs

Communities across the world face water supply challenges due to increasing demand, drought, depletion and contamination of groundwater, and dependence on single sources of supply. Water reclamation, recycling, and reuse address these challenges by resolving water resource issues and creating new sources of high-quality water supplies. The future potential for reclaimed treated effluent is enormous. Although water reclamation and reuse is practiced in many countries around the world, current levels of reuse constitute a small fraction of the total volume of municipal and industrial effluent generated. In addition, to meet their growing water supply needs, communities are considering other non-traditional sources of water such as agricultural return flows, concentrate and other wastewater streams, storm water, co-produced water resulting from energy and mining industries, as well as the desalination of seawater and brackish groundwater. Water reuse provides a wide range of benefits for communities, which translates into creating immense value for the public and the environment. The benefits of water reuse, however, can be difficult to quantify and often go unrecognized. One of the most significant benefits of water reuse is the value created by the inclusion of water reuse in integrated water resources planning and other aspects of water policy and the implementation of water projects resulting in the long-term sustainability of our water supplies. These integrated concepts, which involve the convergence of diverse areas such as governance, health risks, regulation, and public perception, also present a significant challenge to water reuse. These complex connections can assert equal influences on both the benefits and challenges associated with water reuse. In addressing these complex integrated issues, a number of significant barriers and impediments to the widespread implementation of water reuse projects arise. Numerous examples exist of barriers experienced by current water reuse projects around the world, including: the need for innovative technologies, technology transfer, and novel applications; the need for public education and increased public acceptance; better documentation of the benefits of water reuse; the lack of available funding for water reuse projects; working with the media; and the need for support by regulators and politicians. Integrated concepts can also be factors in a number of trends affecting water reuse globally. Current trends include addressing emerging pollutants of concern, the use of advanced wastewater treatments including membranes, indirect potable reuse, public perception, understanding the economics of water reuse, groundwater recharge and aquifer storage and recovery, salinity management (including concentrate disposal), increase in the use of “alternative sources”, environmental or natural system restoration, innovative uses of nonpotable water reuse, and decentralized and satellite systems. Since these trends are emerging developments in the field of water reclamation and reuse, there are a number of research needs associated with these topics. Research is needed to better understand the issues, to develop innovative technologies, and to develop tools and other assistance for communities and water agencies to implement successful water reclamation and reuse projects.     

Reverse osmosis, a key technology in combating water scarcity in Spain

Water is becoming day by day a more precious and even scarce natural resource. In Europe, water shortage or water stress is notable in countries such as Spain, Turkey, Italy, Greece, etc., where rainfalls are few, irregular and inconsistent. In order to improve the use of the Spanish hydrologic resources and to satisfy the higher water demand due to, not only tourism but also agriculture and increased population, the Spanish Government has been promoting over the last years different strategies. In July 2005, a new Act (National Hydrologic Plan) was passed, which included more than one hundred immediate points of action to improve the existing water-related infrastructures and to construct new desalination plants. In addition, in December 2007, a Royal Decree was approved in order to regulate and to promote water reuse applications in the country.Reverse Osmosis is currently taking a fundamental role in seawater and brackish water desalination as well as in water reuse installations. In this paper, the current situation of Spain in terms of water resources is reviewed, the performance of some Reverse Osmosis plants already in operation is documented and the latest key innovations of Reverse Osmosis such as recently developed modules, new configurations and modules with larger diameter are described.