| The action plan for prevention and control of water pollution points out that by2020,the national water environment quality will be gradually improved,the number of seriously polluted water bodies will be significantly reduced,and sewage discharge will be prohibited in some key areas.On June 1,2017,the Ministry of ecological environment of the people’s Republic of China issued the feasible technical guide for pollution prevention and control of thermal power plants,which clarified the water pollution prevention and control technology in the process of thermal power plants,and proposed the technical means of multi-purpose and cascade utilization of various types of wastewater.More strict requirements are put forward for industrial water and drainage.The coal-fired power plant has the characteristics of large amount of circulating cooling water drainage.In consideration of water conservation,it is very important to save water and zero discharge.In this paper,a coal-fired power plant is taken as the object.Firstly,the water balance test of the whole plant is carried out to find out the problems of water consumption,drainage,water quality and operation of each system of the power plant through the test.Then,the problems are diagnosed and different water saving optimization schemes are put forward according to different systems.Next,the circulating water added with the optimal scale inhibitor is determined by the simulated continuous operation test Whether there is scaling and corrosion tendency;finally,the water quality and quantity of the terminal wastewater of the power plant are analyzed,and the terminal wastewater treatment process is discussed.The main conclusions are as follows:To find out the drainage situation of power plant,water balance test was carried out in winter and summer.The water balance test results showed that the water intake of the whole plant in winter was 816.8 m3/h,the water intake per unit power generation was 1.81 m3/(MW·h),the total wastewater discharge was 175.7 m3/(MW·h),and the reuse rate was 97.3%.In summer,the water intake of the whole plant was 1179.7 m3/h,the water intake per unit power generation was 2.69 m3/(MW·h),the total wastewater discharge was 276.9m3/h,and the reuse water rate was 97.8%.The water intake per unit power generation and reuse water rate meet the relevant requirements.According to the operation status of the power plant,practical wastewater recycling methods are developed,and the water quality characteristics of the drainage system are fully utilized,so as to achieve cascade utilization and multiple use of one water.Aiming at the problem of low concentration ratio of circulating cooling water,the change of circulating sewage quantity and water saving ratio under different concentration ratio was discussed.The scale inhibitor and corrosion inhibitor of circulating water were screened and simulated field test was carried out for 528 h.The results show that the No.1 scale inhibitor and slow release agent is the best one.The corrosion rates of 316 L stainless steel and 20 G carbon steel were 0.00034 mm/a and0.00098 mm/a,respectively,which met the requirements.After the transformation of the cooling system of the circulating water part,the concentration ratio of the circulating water can be increased from 2.0~3.0 times to more than 4.0 times.After the concentration ratio of the circulating water was increased,only 210 m3/h of the circulating sewage can be treated,which can realize that the circulating sewage can not be discharged.Through the analysis of the water quality and quantity of the terminal waste water composed of desulfuration waste water and resin regeneration acid-base water,the total amount of the terminal waste water is determined.In view of the high content of suspended solids,calcium and magnesium ions,heavy metal ions,chloride ions and sulfate ions in desulfurization wastewater,the zero discharge treatment process of wastewater was discussed.The conclusion is as follows: the total amount of waste water at the end is about 21.5 m3/h,which is reduced to 5 m3/h by low-temperature multieffect evaporation,and the reduced waste water is finally evaporated and crystallized in the bypass flue to the dust collector to realize zero discharge of waste water. |
PDF Full Text Request