METHOD FOR RECYCLING AMMONIA FROM LOW-CONCENTRATION AMMONIUM CHLORIDE WASTEWATER

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The invention relates to a method for comprehensively treating low-concentration ammonia-nitrogen wastewater by completely recycling, wherein the low-concentration ammonia-nitrogen wastewater and carbide slag or quick lime are mixed and reacted to obtain a mixed solution containing ammonia water and ammonium chloride. The mixed solution is transferred into an ammonia-water evaporative concentration tower to separate the ammonia water and thus obtain an ammonia vapor and a calcium chloride waste solution. The ammonia vapor is transferred into an ammonia-water cooler so as to be cooled and absorbed, and the calcium chloride waste solution is introduced into an aging pool for aging, and then filtered to obtain a purified calcium chloride solution; and the purified calcium chloride solution is introduced into a MVR triple-effect evaporator for evaporation, so as to obtain distilled water and a concentrated calcium chloride solution with a concentration by weight of 35%-40%. Then the concentrated calcium chloride solution is introduced into a fluidized bed for spray granulation, so as to obtain an anhydrous calcium chloride product. The advantages of the invention are : it only can separate and recycle ammonia from the low-concentration ammonium chloride wastewater until the industrial concentration of the ammonia meets the requirements for continual use in rare-earth separation, but also can convert a carbide slag into calcium chloride so as to recycle distilled water and anhydrous calcium chloride products.