Ammonium chloride wastewater is an organic-inorganic wastewater with different concentrations mainly containing ammonium chloride generated in the production process of fertilizers, rare earths, printing, electroplating and other products. This wastewater must be treated to meet the discharge requirements. In recent years, with the rapid development of China's social economy and the large-scale production of industries, the amount of ammonium chloride wastewater generated has been continuously increasing. At present, evaporation concentration and cooling crystallization are commonly used in China to treat ammonium chloride wastewater. According to the physical properties and evaporation rate of ammonium chloride solution, single effect falling film or multi effect falling film evaporator can be used to evaporate and concentrate the dilute solution to a saturated state, and then cool it down in the crystallizer to precipitate. Then it enters the centrifuge for solid-liquid separation to obtain ammonium chloride crystals. The falling film evaporator has the advantages of high heat transfer efficiency, small temperature difference loss, low heating temperature, and ammonium chloride is not damaged by high temperature heating.