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Study on the Design of Water-Using Networks with Multi-Contaminant Involving Regeneration Reuse/Recy

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Tutor: LiuZhiYong
School: Hebei University of Technology
Course: Chemical processes
Keywords: Water-using network,Process design,Process synthesis,Overall concentration poten
CLC: X703
Type: Master's thesis
Year:  2011
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Abstract:
With the scarcity and stricter environmental regulations on industrial effluents underlie the growing emphasis on freshwater minimization, water system integration becomes the research focus, which are mainly embodied in three aspects: wastewater reuse, regeneration reuse and regeneration recycle. The water-using networks involving regeneration reuse/recycling can reduce the freshwater consumption and wastewater discharge significantly. Besides, the zero wastewater discharge can be achieved if the regeneration concentration is low enough. Therefore, it is very important to research the design of the water-using networks involving regeneration reuse/recycling. In this paper, water system integration is investigated. The main contents are listed as follows:In chapter 1, this thesis presents a brief review for the synthesis approaches of water-using networks.In chapter 2, a new method for design of water-using networks is proposed, which includes the determination of the process-performing order and allocation of the process streams. Based on the concentration potential concepts proposed by Liu et al. (AIChE J, 2009; 55: 374-382), a new concept, overall concentration potential of demand (OCPD) for the process stream is proposed. The OCPD of a stream reflects the concentration order of the stream compared to all the other streams (including both demand streams and source streams). In the design, the process performing order is determined by the values of OCPDs of the demand streams. The process with the lowest inlet OCPD is performed first. When satisfying a demand stream of the process being performed, the source with the largest quasi-allocation amount, which is defined in this paper, is used first. A few literature examples are investigated. The results show that the amounts of freshwater consumptions are very close to the minimum freshwater targets, the structures of the designs obtained in this work are not complex compared to that obtained in the literature, and the calculation of the proposed method is very simple.In chapter 3, an iterative method is proposed for the design of water-using networks with single contaminant involving regeneration reuse/recycling, which can be used for the regeneration models with the given regeneration concentration and that with the given removal Ratio (RR). For the models with the given Removal Ratio (RR), the initial concentration(s) of the Sreg should be estimated first, and the flowrate of the Sreg are unknown. The final design of the network involving regeneration reuse/recycling can be obtained after several iterations by using the design method proposed for the network involving reuse only(Liu et al.,CIESC J, 2009; 17(3): 445-453). For the networks with the given regeneration concentration, the final design can be obtained with one iteration. This paper considers the targets of the freshwater consumption, regenerated water flowrate, and the mass load for regeneration, which can reflect the total cost of the network. The structures of the designs obtained in this work are not complex compared to that obtained in the literature, and the calculation of the proposed method is very simple.In chapter 4, an iterative method is proposed for the design of water-using networks with multiple contaminants involving regeneration recycling. The regeneration models can be classified into the given regeneration concentration and that with the given removal Ratio (RR). For the networks with the models of Removal Ratio (RR), the concentration(s) of the Sreg should be estimated first, and the flowrate of the Sreg are unknown. Then the design of the network involving regeneration recycling can be obtained after several iterations by using the design method proposed for the network involving reuse only (Liu et al., AIChE J, 2009; 55: 374-382). For the networks with the models of given regeneration concentration, the final design can be obtained with one iteration. This paper considers the targets of the freshwater consumption, regenerated water flowrate, and the mass load for regeneration, all of them can reflect the total cost of the network. The structures of the designs obtained in this work are not complex compared to that obtained in the literature, and the calculation of the proposed method is very simple.In chapter 5, an iterative method to design the networks involving regeneration reuse/recycling based on the methodology proposed by Liu et al. (AIChE J, 2009; 55: 374-382) is proposed. For the network involving regeneration reuse only, to determine the concentration(s) of the regenerated source, the whole network is divided into two parts: PNCRs(the process non-connected with the regenerated water) and PCRs (the process connected with the regenerated water), and it is assumed that the PNCRs include FEPs(Freshwater essential process)only. The flowrate of the regenerated stream is unknown. After the regenerated concentrations are determined, the water network involving regeneration reuse can be designed by using a modified method of Liu et al. (AIChE J, 2009; 55: 374-382). The final designs can be obtained in one iteration for the networks with known regenerated concentrations, and in a few iterations for the networks with removal ratios of the contaminants. The method proposed can reduce the following parameters simultaneously: the consumptions of freshwater and the regenerated water, and the concentrations of the before-regeneration stream, which reflect the quality of the design of the network involving regeneration recycling. The results of a few literature examples show that the designs obtained in this work are comparable to that obtained in the literature, and the proposed method is simple and effective.
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