Method for recycling ammonia from low concentration ammonium chloride wastewater

Abstract

The invention discloses a method for recovering ammonia from low-concentration ammonium chloride wastewater, which comprises the following steps that: an alkaline substance is added into the low-concentration ammonium chloride wastewater to prepare mixed slurry containing ammonia water and chloride salt; the mixed slurry is subjected to the separation and concentration of the ammonia water in an ammonia water distillation concentration tower to obtain ammonia vapor and a drained waste liquid; the ammonia vapor is conveyed to an ammonia water cooler for cooling treatment, and the ammonia water obtained by the cooling treatment is stored for standby; and the drained waste liquid is subjected to solid-liquid separation to obtain solid-phase residue and a waste liquid containing the chloride salt. The method evaporates the ammonia in the low-concentration ammonium chloride wastewater and concentrates the ammonia to an industrial grade concentration, and has the advantages of broad source of auxiliary materials, low cost, completely sealed technical process, and low energy consumption; and drained substances meet the requirement of no pollution and no nuisance.

Description

technical field [0001] The invention relates to a method for recovering ammonia, in particular to a method for recovering ammonia from low-concentration ammonium chloride wastewater. Background technique [0002] China is a big country of rare earths, with an annual output of about 150,000 tons of rare earths. Low-concentration ammonium chloride wastewater is an inevitable discharge from the non-ferrous industry, especially the wet separation of rare earths. According to statistics, the average consumption of ammonia water or ammonium bicarbonate per separation of one ton of rare earth oxide is more than 6 tons, and due to the limitation of the production process, the content of ammonium chloride in the discharged wastewater is relatively low (the concentration is mostly 0.2-2.5mol / L ), only the rare earth industry discharges more than 1 million tons of ammonium chloride every year. The synthesis of 1 million tons of ammonia requires 800 million cubic meters of natural gas ...

AI Technical Summary

Problems solved by technology

[0003] Currently, the commonly used low-concentration ammonia nitrogen wastewater recovery process is mainly direct concentration, evaporation and crystallization to recover ammonium chloride, or ammonium chloride plus circulating agent to evaporate and recover hydrochloric acid and ammonia water. The former has the following disadvantages: the recovery rate is too low and the heat energy consumption is large. In addition, the ammonium chloride market is saturated, and a large amount of ammonium chloride cannot be sold due to the accumulation of ammonium chloride. Many enterprises have to stop recycling production halfway; the concentration of ammonia water and hydrochloric acid produced by the latter is too low to be used, and the energy consumption is large, so industrial production cannot be formed.

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