Feasibility Study On Water Network Optimization And Terminal Wastewater Reuse Process In Coal-Fired Power Plant

Under the background of water shortage and coal-fired power generation as the primary energy structure in China for a long time,combined with the formal implementation of the pollutant discharge permit system,the effluent and wastewater treatment of power plants have been strictly supervised.With the development of water-saving transformation in many power plants,it is difficult to reuse the terminal wastewater generated after classified collection,cascade utilization,and concentration.In this study,a coal-fired power plant as the research object,through the analysis of the characteristics of the power plant water system,the water network of the whole plant to optimize the design,the terminal wastewater reuse treatment,to achieve the power plant zero liquid discharge.Based on the survey of the whole water network and the water balance test,the improvement measures were formulated.The water consumption and wastewater discharge were initially reduced,and the improved water balance diagram was obtained.The water pinch point-mathematical programming method was selected as the optimization method of water-saving and emission reduction.The water network diagram under the condition of zero discharge process was obtained.The water consumption was reduced from 235 m~3/h to 157 m~3/h,and the wastewater discharge was decreased from 40 m~3/h to the lowest zero.To solve the problem of complicated calculation caused by unstable water quality and quantity in power plant,an algorithm program for calculating water consumption data of target power plant was written with Python as the main body,and the data of minimum water consumption and corresponding mass load concentration were obtained,which were consistent with manual calculation.Taking the terminal wastewater of the target power plant as the research object,and based on the quality and quantity of the terminal wastewater obtained from the deep water-saving,three main stages of the current mainstream process:pretreatment unit,the concentration and reduction section,and the curing unit were selected and compared with the design scheme.By comparing the process flow,the design of the central treatment unit,and the investment and operation cost of the wastewater pretreatment unit,it was recommended to adopt the process of Ca(OH)2-Na2SO4-Na2CO3 with lower operation cost,and the cost of adding agent was 20.15yuan/m~3.Terminal wastewater concentration reduction and curing period of scheme selection,respectively from the total system investment,running costs and comprehensive economic index,low-temperature flue gas evaporation and concentration+bypass flue evaporation technology for the recommendation,plans a total investment of 63 million yuan.The total running costs were84.63 yuan/m~3,save pretreatment process at the same time,the salt crystals were transferred into the fly ash.The target power plant recommends low-temperature flue gas evaporation and concentration+bypass flue evaporation drying process as the terminal wastewater treatment scheme.After concentration and evaporation,the produced water was reused,thus achieving the goal of zero discharge.Based on the data analysis and research of the target power plant,the feasibility of water network optimization and terminal wastewater reuse process engineering selection in the power plant is theoretically demonstrated in this study.Water-saving suggestions and terminal wastewater treatment process selection scheme are proposed according to the demonstration results,which also have particular reference significance for water-saving and emission reduction work of other power plants.