Study On Design Of Water Utilization Network Involving Energy Integration And Flexibility

Effective utilization of water and energy is the key factor of sustainable development in process industries, it is also an important science and technology problem needed to be solved in systems engineering academic research. Now energy integration technology is more mature, and has been applied in process industries widely. Mass integration technology rises just recently, and has some improvements in theory. Water network is a kind of special mass exchanger network, and has been given more attention. But the avaible methods are only suitable to single-contaminant system, and have some simplified treatments, they can not be applied to multi-contaminant system which always exists in common reality. And only utility cost is concerned in energy integration of water network, exchanger area and setting cost are ignored, simultaneously energy integration can be done only in water network, their methods do not realize genuine simultaneous minimum of water and energy. And the flexibility analysis and design is not considered in water network. In this paper, the researches have been done as follows:(1) As to the multiple-objective optimization of water and energy in process industry, this article uses the stepwise design method which. departs the optimal problem into two stages. In stage one, the water pinch method or mathematical programming method is used to minimize the freshwater flowrate. In stage two, the energy integration is carried out under the minimum freshwater flowrate. The method is suitable both for single contaminant and multiple contaminants systems. The integration of energy can be carried through total process system beyond the water utilization network. A case on literature is validated.(2) Stepwise design method of minimum water and energy does not reach the simultaneous minimization of water and energy in reality. Mathematical programming method is a powerful tool to perform simultaneous design because it has the advantage of simultaneous optimization and dealing with multiple objectives together. As water network and energy network is alternate in process industries, and mathematical scale of water network involving energy integration is large, so simultaneous design of optimization of water and energy is difficult and important. Based on the study of the stepwise design method, the simultaneous minimum of water and energy is reached by the adaptive simulated annealing genetic algorithm. The contrast of case study with stepwise design method indicates that the simultaneous design method is efficient.(3) For the large non-convex nonlinear programming (NLP) or mixed integer nonlinear programming(MINLP) caused by optimization of water and energy, an adaptive simulated annealing genetic algorithm(ASA/GA) is developed in this paper. The strategy of adjusting step size and temperature decreasing adaptively raises the speed and the ability to find global optimum with a higher probability. And genetic algorithm embed in the inner of adaptive simulated annealing algorithm compensates the deficiency that simulated annealing is difficult to perform global optimization because of its missing for ago information. Test of functions of non-convex NLP show the hybrid algorithm has good capability in convergence speed and finding the global optimum. The combination of this algorithm and genetic algorithm and simulated annealing(GA/SA) used for energy integration makes the simultaneous optimization of water and energy in process industries comes to reality.(4) In order to make water network structure more stable, flexibility analysis and design are considered in water network, in order to make water network more reasonable in application of process industries.