Method for recovering ammonia from rare earth separation waste liquid

Abstract

The invention discloses a method for recovering ammonia from rare earth separation waste liquid. The method especially includes the steps of mixing and concentrating a low-concentration ammonium chloride solution to be recovered; allowing the low-concentration ammonium chloride solution to be recovered to react with calcium oxide; recovering ammonia from reaction overflow through a water-jet pumpI and a vacuum ammonia absorption tank I; recovering a solution obtained from reaction with a tube heat exchanger, an evaporation tower, an ammonia vacuum transfer tank and the like. The ammonia is recovered with the method, the recovery rate of the ammonia is greater than or equal to 99.5%, the concentration of ammonia water obtained finally reaches 8.0-10.0mol L, and efficient and thorough recovery is achieved; meanwhile, the ammonia nitrogen content in the waste liquid discharged by this method is less than or equal to 5.0ppm, far less than the national first-level discharge standard of 15.0ppm, and low discharge and low pollution are achieved; in addition, with the method, the consumption of steam is only 0.8-1.0tons / ton of ammonia water, the amount of steam needed for the operation isgreatly saved, and energy is saved.

Description

technical field [0001] The invention belongs to the field of rare earth separation resource recovery, in particular to a method for recovering ammonia from rare earth separation waste liquid. Background technique [0002] my country is a major producer of rare earths, with an annual output of more than 250,000 tons of rare earths, and a huge amount of mining and processing. In today's rare earth wet separation process, ammonia water saponification and ammonium bicarbonate precipitation are usually used in the rare earth extraction and rare earth precipitation process sections respectively. The ammonia water and ammonium bicarbonate auxiliary materials used in them cause the waste liquid after separation of rare earth elements to contain ammonium chloride, which is rare earth Separation of sources of ammonia nitrogen pollution in waste liquid. The discharge of waste liquid not only causes serious environmental pollution, but also causes a large amount of ammonia to be wasted...

AI Technical Summary

Problems solved by technology

A method for reclaiming ammonium chloride as described in the patent application document CN1224694A as the publication number, which obtains ammonium chloride by directly concentrating, evaporating and crystallizing, but this method is because the concentration of ammonium chloride in the waste liquid is low, resulting in The processing cost is high, so it has not been popularized; a kind of recovery method that is recorded in the patent application document CN1504413A as the publication number, it is to add a circulating agent in the ammonium chloride solution, and reclaim ammonia and hydrochloric acid by evaporation, but this method Because the ammoniacal liquor and hydrochloric acid concentration of recovery are too low, useless, so do not obtain industrial application; In addition, the patent document that publication number is CN101475194B also discloses a kind of method that reclaims ammonia from low-concentration ammonium chloride waste water, and this method is Alkaline substances are added to low-concentration ammonium chloride wastewater to generate ammonia water and chloride salts, and then separated and concentrated to obtain valuable ammonia water. This method has been widely used by rare earth separation companies because of its high industrial application value, but Due to the limitations of the current technological process and equipment, this method has the problems of low ammonia yield and high processing energy consumption. The recovery rate of ammonia in this method is only 70.0-80.0%, and the ammonia content in the final discharge is still relatively high. The discharge will still cause certain environmental pollution, and the concentration of ammonia water produced is only 3.0-5.0mol / L, while the steam consumption is ≥1.5 tons / ton of ammonia water

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