Study On Design Methodology Of Water Utilization Network In Process Plants

Process industry not only consumes large amount of fresh water, but aslo discharges a great deal of wastewater. It has been one of the main sources of the pollutants in nature water system. Water resources are increasely scarce and environmental pollution is becoming more and more serious, which has restricted the development of socical economy. Process integration technology provided the research of wastewater reduction with both technical support and systematic approach, and circular economic thought gave the aim of the wastewater reduction research. On the basis of summarizing the research results using process integration technology, this paper analyzed roundly the actual status and the development trend of wastewater reduction in detail in order to give some academic directions to the water saving and pollution reducing of process industries. The main contents of this paper are as follows:1. To resolve the problem in designing process water networks with multiple contaminants, an algorithmic procedure is presented, which fits for designing process water networks with multiple contaminants. Based on the water-pinch technology and the necessary conditions of optimality of multiple contaminats system, this methodology presents a water-spply priority algorithm, in order to finish the designment of process water networks with multiple contaminants in a series of steps. According to the results of actual cases, the precision of this methodology, is similar with the branch and bound algorithmic procedure for multi-contaminant systems, but is simpler.2. For a large petro-chemical or chemical complex with many unit processes, the piping networks become very complicated and hard to be designed and controled, so this paper presents a design methodology for multiple-contaminant water networks with two internal water mains. In this methodology, water is collected by setting the internal water mains in the networks, and is sent to the units, which are poor request about the water quality. Because of applying the rules of water-pinch analying to set the position for the first internal water main, and providing a relative reasonable approach to complete the dividing of an internal water main to subsequent process water, therefore, compared with congeneric designing methods, the fresh water consumption in this water networks obtained by this approach will reduced to a largeextent. The structure of the water networks designed with this methodology is simple and relatively steady.3. After studying different kinds of design methodologies for water networks, it's important to examine the environmental benefit for implementing circular economic thought. What's more, because water networks are only one part of industrial water systems, the rebuilding of the water networks will impact the environmental benefits of the whole water systems. On the basis of introducing the methodology of life cycle assessment and analyzing the main effect factors of classical water systems, this paper presents the life cycle assessment framework, which fits for assessing the environmental benefit of water networks.4. A factory can improve its efficiency of water-using under the help of a high efficiency water networks, however it also depends on management, regeneration reuse and so on. To examine the condition of the factory water using, the simplest method is to compare the water-using situation in different factories applying certain index system. According to the analytic hierarchy process, the index system, which is used to assess the water-using situation is presented, and the method of determining in the index weight is presented. The method has been used in refineries, and the results are good.