Water Utilization Network Optimization Design With Multiple-contaminant Based On Reliability Analysis

Study of the water saving and emissions reduction in chemical industry began with the1980s for a large amount of freshwater consumption and waste water emission of it. Up to now, the research of single contaminant water utilization network (WUN) is quite mature, but the multiple-contaminant problem is still on the way. Here, we do a further study about this problem. High reliability will not only reduce the maintenance cost largely but also keep the production safety. It is easily found that the current studies of reliability analysis and reliability improvement are mainly for heat exchange networks. While, there is no corresponding work for the water allocation networks which play an important role in chemical industries. From the analysis above, this paper analyzed the reliability of a given water utilization network and applied the multi-objective optimization method to deal with water utilization network design with multiple-contaminant involving reliability analysis. The water utilization network which satisfied reliability specification and minimum fresh water consumption of is the goal. The main research of this paper is as follows:(1) A further study about multiple-contaminant water utilization network design is carried on. The abilities of providing reuse water and accepting reuse water of the water unit operations are determined by analyzing the limiting data of them. Then order the abilities with numbers and plot two lines, respectively to the two abilities from which the units that serve as reuse water resources is determined. The superstructure will be simplified and the non-linear programming is easy to resolve. GAMS can be used to obtain the minimum freshwater consumption and the optimum structure of the water utilization network. Two illustrations demonstrate the feasibility of this method.(2) This paper adopts the failure mode effects and criticality analysis (FMECA) to analyze the reliability of a given WUN. First, Subsystems of the network can be recognized according to the matrix that formats based on the initial network. The subsystem is regarded as a series system and its reliability is calculated from "product rule". Then the overall reliability of the given WUN can be evaluated in terms of the network subsystems. If the system fails to meet the process reliability specification, simplification measures to the network structure is imperative. One is that reusing water streams are only replaced with the freshwater streams to undertake the mass transfer mission. The other is considering the re-optimization of the new subsystems. Two examples show that the second is better for water conversation.(3) This paper studied WUN design with multiple-contaminant involving reliability analysis based on the reliability analysis of a given WUN. The constraint method of the multi-objective optimization is applied to solve this two objectives problem. The reliability objective of the system is first concerned by enumerating systems which have different kinds of subsystems. Then it was taken as a constraint when designing the WUN. Non-linear programming (NLP) is established and solved by GAMS. The instances proved that the method is feasible for WUN design with freshwater consumption and reliability specification.