Method for treating ammonium sulfate-containing process wastewater by magnesium process and recycling magnesium sulfate

Abstract

The invention discloses a method for treating ammonium sulfate-containing process wastewater by a magnesium process and recycling magnesium sulfate. According to the method, a decomposing agent is added into the ammonium sulfate-containing wastewater, and under a certain condition, a double decomposition reaction is performed on magnesium oxide in the decomposing agent and ammonium sulfate in the wastewater to produce ammonia and magnesium sulfate; under a heating condition, the ammonia escapes along with steam and is condensed and absorbed to obtain low-concentration ammonia water (with the concentration of 7-10%), and through steam stripping, the ammonia water can also be further concentrated till the concentration is 20-28%; after the ammonium decomposition reaction is completed, an ammonium decomposition slurry is filtered to obtain a magnesium sulfate solution, and under the non-evaporative condition, the magnesium sulfate solution is sent into a multifunctional magnesium sulfate heptahydrate crystallizer and is crystallized and separated to obtain a magnesium sulfate heptahydrate product. By the method, the goals of low consumption, low cost, harmlessness and high benefit of ammonium sulfate wastewater treatment are achieved.

Description

technical field [0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for treating process wastewater containing ammonium sulfate by a magnesium method to recover ammonia water and producing magnesium sulfate without steam consumption. Background technique [0002] Ammonium nitrogen wastewater refers to process wastewater containing ammonium salts, such as ammonium sulfate and ammonium chloride, produced in the production process of magnesium salt, metallurgy, inorganic pigments, electronics and other industries. If it is discharged, it will not only cause serious pollution to the environment, but also cause the loss of ammonium resources. [0003] In the prior art, the treatment methods of ammonium nitrogen wastewater mainly contain the following types at present: the one is to concentrate the ammonium nitrogen wastewater and crystallize to obtain ammonium salt; The reaction decomposes the ammonium salt to genera...

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Problems solved by technology

[0004] In the above process, although ammonium salt products can be obtained by concentrating and crystallizing ammonium nitrogen wastewater to obtain ammonium salt products, the energy consumption in the treatment process is high, the cost is difficult to control, and the added value of ammonium salt products is low, so it is difficult to obtain economical benefit

The calcium process is a mature ammonium nitrogen wastewater treatment process, but the problem is that when the ammonium salt in the ammonium nitrogen wastewater is ammonium sulfate, a large amount of by-product gypsum is produced, and the sales and environmental burden are heavy.

The cost of treating ammonium nitrogen wastewater by sodium hydroxide method is relatively high, and a large amount of ammonium solution containing sodium salt is discharged, which has an impact on the environment

The treatment of ammonium nitrogen wastewater with magnesia (light-burned magnesia), that is, the magnesium process, has been reported in recent years. Its advantage is that there is no secondary residue in the treatment process, and the ammonium solution residue can be comprehensively utilized, but the disadvantage is that the treatment process Relatively high steam consumption

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