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Study On Process Integration For Wastewater Minimization

Posted on:2004-04-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y LiFull Text:PDF
GTID:1101360092480324Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
The scarcity of water resource year after year and the severity of environmental pollution day after day call for process industries to actualize wastewater minimization. Process industry not only consumes large amount of fresh water but also discharges a great deal of wastewater. So it becomes the emphasis of industrial water saving and water pollution prevention. Process integration techniques provide technical support and a systematic approach for wastewater minimization research. On the basis of analyzing roundly the actual status and development trend of wastewater minimization we lucubrate the process integration techniques of wastewater minimization in detail to direct the water saving and pollution reducing of process industries in theory. The main contents of this paper are as follows:1. Wastewater minimization can be achieved through the following step: first, the generated wastewater capacity is reduced by the water utilization network design considering wastewater reuse, then the content of contaminants in wastewater is decreased by the distributed wastewater treatment network design. The process integration techniques of water pinch technology and mathematical programming applied to the stepwise design are mature, but they have advantages and disadvantages individually. As the foundation of academic research and satisfying the comprehensive practical application, the approach is proposed to combine the water pinch analysis and mathematical programming. Which not only deepens the understanding for process but also reduces the dimension of superstructure. And it avoids network evolution and operation splitting. Case studies illustrate the design results are close to global optimum.2. Design of water utilization network and wastewater treatment network simultaneously can further reduce the fresh water consumption and wastewater generation capacity, and decrease the cost of treatment units. Mathematical programming is a powerful tool to perform simultaneous design because it has the advantage of simultaneous optimization and dealing with multiple objectives together. As the research hot spot and difficult point, water network of simultaneous design is studied. The superstructure of water network with stream split and considering reuse, regeneration reuse as well as regeneration recycle is built. Which is convenient to separate the overall water network into two subsystems, waterutilization network and wastewater treatment network for different demands or change into water network without stream split through simple constraints. On the basis of these, a comprehensive nonlinear programming model (NLP) is formed. Because the bilinear terms of which flow rate times contaminant concentration in mass balance lead to that the NLP problem is non-convex. An adaptive simulated annealing genetic algorithm is adopted to solve the problem according to its feature. The contrast of case study with stepwise design and literature result indicates the proposed simultaneous design approach is efficient.3. The performance of environmental impact optimization begins to integrate into the system design because of the importance of environmental issue. Meanwhile, in order to deal with the matter that some contaminants with trace concentration will produce great environmental impact, the environmental impact is selected as objective function and balanced with economic objective. Zero liquid discharge is put forward for wastewater minimization design with remarkable environmental impact according as the multi-objective optimization results. The hybrid approach for zero liquid discharge is as follows. The recycle water capacity in closed loop can be decided through wastewater capacity minimization. Furthermore, wastewater are treated to attain contaminants concentration which satisfy the influent demand of deep treatment technologies. Finally, the corresponding deep treatment units are selected to treat the specific contaminants so as to attain the needs of closed loop. Case s...
Keywords/Search Tags:Wastewater minimization, Process integration techniques, Water pinch technology, Mathematical programming, Superstructure modeling, Adaptive simulated annealing genetic algorithm, Multi-objective optimization, Zero liquid discharge
PDF Full Text Request
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