Description The application of evaporative crystallization skid in wastewater treatment of natural gas purification plant needs to be analyzed in combination with the phase diagram of Na2SO4-NaCl-H2O. Evaporative crystallization is not only the process of separating salt and water, but also can combine the solubility characteristics of each inorganic salt to separate the inorganic salt effectively by step in the evaporative crystallization system. Supported by phase equilibrium, the technology can be used not only in waste water treatment of purification plants, but also in gas field water, underground brine, salt lake water and wastewater containing various inorganic salts. On the premise of salt water separation, salt salt separation can be further achieved. The separated inorganic salts can be reused according to the quality of separation, or used as chemical raw materials, Or as animal husbandry salt, which can not only realize zero discharge of terminal wastewater, but also realize the rational recycling of a variety of valuable resources. The waste water from the purification plant first enters the RO membrane treatment unit. After two-stage membrane concentration, fresh water is reused. The concentrated water enters the concentrated pool and enters the evaporative crystallization system through the feed pump. In the evaporative crystallization system, due to the different solubility of Na2SO4 and NaCI, with the evaporation of water, the material liquid is further concentrated, and Na2SO4 is preferentially crystallized and precipitated to form nitrate slurry. The nitrate slurry enters the centrifugal dehydration system through slurry pump. After solid-liquid separation, the centrifugal mother liquor returns to the evaporative crystallization system, and the solid salt is sold as industrial salt. With the evaporation, the COD in the raw water is enriched with the decrease of water content, which leads to the increase of the viscosity of the feed liquid in the evaporation tank and seriously affects the crystallization of salt in the evaporation process. The feed material of the evaporative crystallization skid is brine from the upstream electrodialysis device, and the processing capacity of the skid is 300m3/d. The annual production time is 8000 hour. Main equipment: Process integration skid, compressor skid, mixed hydrocarbon storage skid, instrument and control device. Brine conditions Flow: 300m3/d pressure: 0.4 ~ 0.45mpa (g) Temperature: 20 ~ 50 ℃ Brine source: concentrated brine produced by electrodialysis treatment, and standard sewage after biochemical treatment. Conditions for the production device Flow 300m3/d pressure 0.25 ~ 0.27mpa (g) Temperature ~ 40 ℃ Solid  0.25 t/h Maximum overall size 30x 18x 26 (m)