Optimization-based method for calculating water networks with user specified characteristics

This paper addresses problem of designing water usage network that consists of fixed flow rate water using processes. A design method is founded on the solution of mixed-integer linear programming (MILP) model of network superstructure. The application of optimization to solve basic formulation of network synthesis has been reported in some works. However, this approach applies certain extensions of the standard formulation that allow accounting for several industrial scenarios. In particular, it is possible to apply various performance indices and imposing conditions on continuous variables as well as on network topology. Multiple contaminant case is easily accounted for. At least but not at last, the method is able to generate several solutions of identical values of major performance indices but of different structure and other features. All these possibilities are available within single optimization framework. Several examples are given to illustrate advantages of the approach.     

Optimal design of batch mass exchange networks with multipurpose exchange units

A novel mathematical model for simultaneous optimization of batch mass exchange networks with multipurpose mass exchange units that can be shared by more than one match in different periods is presented in this work. It can be shown that both utility cost and capital investment can be reduced simultaneously with the use of multipurpose mass exchangers and mass storage tanks. Specifically, state-space superstructure that does not contain any structural simplification is proposed to capture the entire characteristics of the network configuration and a mixed-integer nonlinear optimization model is then formulated accordingly to generate the optimal batch operating policies and the corresponding flowsheet. Two examples are presented in this paper to demonstrate the validity and advantages of the proposed approach.     

Simultaneous synthesis of heat-integrated water networks by a nonlinear program: Considering the wastewater regeneration reuse

Heat-integrated water network synthesis (HIWNS) has received considerable attention for the advantages of reducing water and energy consumptions. HIWNS is effective in water and energy sustainability. Mixed integer non-linear programming (MINLP) is usually applied in HIWNS. In this work, a novel nonlinear programming (NLP) was proposed for HIWNS by considering wastewater reuse and wastewater regeneration reuse. Integer variables are changed to non-linear equation by the methods for identifying stream roles and denoting the existence of process matches. The model is tested by examples with single and multiple regeneration unit problems. The testing results showed that the NLP is an alternative method for HIWNS with wastewater reuse and regeneration reuse.     

过程工业水分配网络的研究进展

回顾了水分配网络的发展历程,介绍了水分配网络的用水网络和废水处理网络2个子系统的研究进展,阐述了图解方法、数学优化法等用水网络综合方法的发展状况,并对水分配网络设计中多杂质和热集成等方面的问题进行了展望。     

Improvements in surrogate models for process synthesis. Application to water network system design

High accuracy models can be obtained by using different types of surrogate models that accurately approximate equipment phenomenological models and can be used in synthesis problems, leading to faster and more precise solutions. Two types of surrogate models are used to approximate equipment phenomenological models: polynomial and neural network-based. In some cases, these surrogate models are not able to represent more complex equipment. An original methodology to reformulate these models using equations from shortcut equipment design is proposed. A medium-size case study involving fifteen units is presented. The synthesis problem is solved in a short computational time, leading many local solutions. Since several local optima objective function values are very close to each other, the choice of the best configuration among those found should be done qualitatively, because the differences among the objective function values are not significant if compared to the accuracy of equipment cost correlations in the literature.     

The P-graph approach for systematic synthesis of wastewater treatment networks

Wastewater treatment consists of three or four sequential stages: preliminary, primary, secondary, and tertiary. Each stage can comprise multiple alternative technologies that can perform the same tasks with different efficiencies, operating times, and costs. Thus, we propose a systematic approach for designing wastewater treatment networks by utilizing principles of mathematical modeling and generating an exhaustive enumeration of all the possible technologies and their connections during the early stages of designing a treatment facility. Some of these structures are nonintuitive and include recycling, reprocessing, bypasses, and multiple technologies in parallel or series to remove the same contaminant. The nonintuitive structures with multiple technologies may provide a measure of resilience compared to typical heuristic designs. Thus, the combination of P-graph methodology and the sequence of treatment technologies predicted via the optimization algorithm from the maximal structure is based on holistic considerations and does not lead to suboptimal solutions.     

An innovative design of septic tank for wastewater treatment and its performance evaluation: An applicable model for developing countries

A study was carried out to evaluate the treatment efficiency of modified model of septic tank(ST)for the treatment of domestic wastewater.The objective was to explore the possibility of increasing the removal efficiency,at household level,thereby reducing cost and treatment burden on city level treatment plants.For this purpose,a bench scale model of ST was prepared and operated continuously for 78 days at different detention times i.e.,48,24 and 12 h and at two reactor temperatures viz.15°C and 25°C.Domestic wastewater was fed to the bench scale ST without pre-settling.Research was conducted under two different arrangements.Firstly,by installing baffles in the bench scale ST(called Run-1 setup),and secondly by installing perforated plates between the baffles(called Run-2 setup).Results demonstrated that Run-2 setup is better than Run-1 setup.Temperature significantly affects the efficiency.Detention time of 24 h was found feasible.Run-2 setup demonstrated a percentage BOD removal of 45%with effluent BOD of 113 mg·L~(-1)at 15°C and 85%removal with effluent BOD of 31 mg·L~(-1)at 25°C.It is concluded that if a modified design of ST using Run-2 setup is provided at household level,the effluent coming out of the house will meet the National Environmental Quality Standards(NEQS)when reactor temperature is close to 25°C.Development authorities are suggested to change their by-laws and make modified ST mandatory for all households.This may significantly reduce the cost and footprint of city level wastewater treatment plants being planned.     

Optimal synthesis of Fenton reactor networks for phenol degradation

There is an increasing need to treat effluents contaminated with phenol with advanced oxidation processes (AOPs) to minimize their impact on the environment as well as on bacteriological populations of other wastewater treatment systems. One of the most promising AOPs is the Fenton process that relies on the Fenton reaction. Nevertheless, there are no systematic studies on Fenton reactor networks. The objective of this paper is to develop a strategy for the optimal synthesis of Fenton reactor networks. The strategy is based on a superstructure optimization approach that is represented as a mixed integer non-linear programming (MINLP) model. Network superstructures with multiple Fenton reactors are optimized with the objective of minimizing the sum of capital, operation and depreciation costs of the effluent treatment system. The optimal solutions obtained provide the reactor volumes and network configuration, as well as the quantities of the reactants used in the Fenton process. Examples based on a case study show that multi-reactor networks yield decrease of up to 45% in overall costs for the treatment plant.     

Graphene-enhanced visible-light photocatalysis of large-sized CdS particles for wastewater treatment

The hybrid composites of graphene decorated by large-sized CdS particles (G/M-CdS) were prepared by a one-pot solvothermal route in which the reduction of graphite oxide into graphene was accompanied by the generation of microsized CdS particles. The structure and composition of the obtained nanocomposites were studied by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The CdS particles with the average sizes of approximately 640 nm were formed on graphene sheets. The as-prepared composite was used as adsorbent to remove dye from wastewater using the organic dye Rhodamine B as the adsorbate. The G/M-CdS composite reveals a high photodegradation rate under visible light irradiation. Our results demonstrate that the G/M-CdS is very promising for removing organic dyes from wastewater.     

超声波在废水处理中的应用

介绍了超声波在废水处理中的应用,它能使废水中的污染物得有效降解,而展示其应用前景。     

Systematic methods and tools for design of sustainable chemical processes for CO2 utilization

A systematic computer-aided framework for sustainable process design is presented together with its application to the synthesis and generation of processing networks for dimethyl carbonate (DMC) production with CO₂ utilization. The framework integrated with various methods, tools, algorithms and databases is based on a combined process synthesis–design–intensification method. The method consists of three stages. The synthesis-stage involves superstructure based optimization to identify promising networks that convert a given set of raw materials to a desired set of products. The design-stage involves selection and analysis of the identified networks as a base case design in terms of operational feasibility, economics, life cycle assessment factors and sustainability measures, which are employed to establish targets for improvement in the next-stage. The innovation-stage involves generation and screening of the more sustainable alternatives through a phenomena-based process intensification method. Applications of the framework are highlighted for the DMC production process.     

数学规划与图形方法相结合设计热集成用水网络

将数学规划法与图形方法相结合探究单杂质用水网络与换热网络的集成问题。首先构建混合整数非线性规划模型（MINLP）,在最小公用工程消耗下优化流股参数未知情况下的分离系统组合曲线面积,得到了最为节能、换热面积最小的用水网络结构。在此基础上,提出了新的分离系统组合曲线演化步骤和规则,可以得到换热单元数目较小的换热网络结构。算例表明,与现有的基于分离系统的热集成用水网络设计方法相比,在最小化公用工程用量的同时可以进一步降低换热器数目与总换热面积。     

Optimal design of single‐contaminant regeneration reuse water networks with process decomposition

Water network with regeneration schemes (e.g., regeneration reuse, regeneration recycling) can reduce freshwater consumption further than water network merely with direct reuse. Regeneration reuse, compared with regeneration recycling, can additionally avoid unexpected accumulation of contaminants. Owing to these features, process decomposition can help to reduce freshwater usage and wastewater discharge of regeneration reuse water systems and achieve the results, which graphical method delivers. In this article, the effect of decomposition on water‐using process and further on regeneration reuse water system is briefly analyzed on the concentration‐mass load diagram. Then a superstructure and three sequential mathematical models, which take process decomposition into account, are in turn developed to optimize single contaminant regeneration reuse water systems. By several examples, the reliability of the models is verified. Moreover, several decomposition strategies are summarized to realize the regeneration reuse water network, which attains the targets from graphical method. The results indicate that postregeneration concentration has a major impact on the scheme of process decomposition. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Investigation of microfiltration for treatment of emulsified oily wastewater from the processing of petroleum products

This research has investigated the possibility of using polyvinylidene fluoride (PVDF) membrane to treat the emulsified oily wastewater. Experimental results showed that the microfiltration could effectively treat the laboratory prepared emulsified oily wastewater and the fouled membrane could be recovered by using conventional cleaning methods. Similar promising results were obtained to treat factory emulsified oily wastewater by using microfiltration. In addition, different cleaning methods were investigated to recover the fouled membrane flux. Results showed that suitable interval operation of filtration and aeration could eliminate the membrane fouling under relative lower transmembrane pressure. Experimental results provided the basis for further investigation of its application in factory emulsified oily wastewater treatment.     

Fenton法及类Fenton法在污水处理方面的研究与应用

Fenton试剂通过H2O2和Fe2+作用产生.OH,因而具有极强的氧化能力,在治理环境污染方面得到了广泛的应用。为了改善Fenton法中H2O2利用率低等缺点,越来越多的研究者将Fenton法与其它方法联/并用,极大提高了Fenton的催化效率。作者主要介绍了Fenton法及类Fenton法催化原理及其在污水及污染物处理方面的应用。     

二氧化氯处理农药厂含硫化物废水的研究

进行了二氧化氯处理农药厂含硫化物废水的研究,考察了废水pH值,处理温度和时间等因素对硫化物去除率的影响.结果表明,废水pH值在3-10内对硫化物的去除率无影响,低温下处理2h后也有较高的去除率.同时,实验得到了适宜的二氧化氯加入量和处理条件.     

Superstructure-based design and operation for biomass utilization networks

This paper is providing a design and evaluation methodology for biomass utilization networks (B-NETs) planning in local areas. The methodology is an effort to integrate various exertions of many researchers as well as stakeholders in the biomass field including process technologies, local area classification and renewable energy mechanisms to design and evaluate B-NETs. The proposed design methodology has three steps: classification, problem formulation and suggesting solution methods. The core part of planning the B-NETs utilization methodology is the superstructure that is a super class model for the processes of biomass utilization networks that has to be built for the local area. The biomass utilization superstructure (BUSS) relates the biomass resources to their products, available processes, and possible future processes of utilization in static manner. Although the local area BUSS is static in nature, it shows the decision makers what kinds of B-NETs are, or can be, available in their area. It is important to note that for each super class process there exists a number of elemental technologies, or what we call unit process (UP), that can perform the job under the same condition with different processing constraint. To support the design and operation process a technological information infrastructure (TII) needs to be built to work as an information pool and simulation tool. With the support of TII and the BUSS different scenarios can be synthesized, analyzed and compared. Scenarios development enables the designer to check processing alternatives as well as biomass promotion mechanisms that fit the concerns of various stakeholders. The results of the methodology application can be given in the form of suggestions of a specific network class(es) or scenarios that can be applied in a class of localities with the same characteristics. Following to methodology configuration, a proposal for optimization methods is discussed and a case study for comparing biomass network scenarios in mountainous city is introduced.     

Optimal storage design for a multi-product plant: A non-convex MINLP formulation

We discuss a tank design problem for a multi product plant, in which the optimal cycle time and the optimal campaign size are unknown. A mixed-integer nonlinear programming (MINLP) formulation is presented, where non-convexities are due to the tank investment cost, storage cost, campaign setup cost and variable production rates. The objective of the optimization model is to minimize the sum of the production cost per ton per product produced. A continuous-time mathematical programming formulation is proposed and several extensions are discussed. The model is implemented in GAMS and computational results are reported for the two global MINLP solver BARON and LINDOGlobal as well as several nonlinear solvers available in GAMS.     

电镀废水处理站总体设计要点

通过改进清洗方式，进行电镀工艺改革，降低电镀废水量和有毒物质浓度。对电镀废水处理站的总体设计依据及其内容进行了详细描述。     

Design of continuous ion exchange process for the wastewater treatment

A generic design procedure for the continuous ion exchange process is proposed. The procedure is based on the optimized arrangement of parallel batch columns. The continuity of the process is achieved by proper shifting of the inlet conditions. The method for the optimization of the process variables is presented.The concept is demonstrated on the example of ammonia removal from wastewaters. Two flowsheet schemes are considered utilizing fresh or recycled regenerating agent.The superiority of the optimized process over the periodic operation is demonstrated.