Separation of salt and alkali from waste salt and alkali residue in production of hydrazine hydrate and technique of cyclic utilization

Abstract

This invention describes a process for the recovery and recycle of industrial waste solids, especially the salt-alkali separation and recycle of the waste salt-alkali solids from the manufacturing of hydrated nitriles. This invention uses water, mother liquid and sodium bicarbonate to wash the waste salt-alkali solids from the manufacturing of hydrated nitriles, so that Na2CO3 and NaOH in the waste salt-alkali solids are washed into the solution. The washing solution is then cooled to 0-5deg.C, and filtrated and separated to obtain solid sodium carbonate decahydrate, which can be commercialized after washing. The mother liquid, after separating the solid alkali, is directed to the next process for washing the waste salt-alkali solids without discharge. During the circulatory washing of the waste salt-alkali solids, the table salt keeps in the solid state. After centrifugal separation, the table salt containing 3% of alkali can be obtained and used for sodium carbonate industry. The said table salt NaCl, after washing and separation to remove a small amount of hydrazine and amine, can be used for chlorine-alkali industry. Chlorine Cl2 and sodium hydroxide NaOH are raw materials for sodium hypochlorite NaClO, which is a raw material for producing hydrazine hydrate. In addition, sodium hydroxide is directly involved in the reaction for producing hydrazine hydrate N2H4íñH2O, thus constituting an internal recycling system of a manufacturing plant without discharging, which not only is environmentally friendly but also reduces transportation load and production cost. This invention describes a rational process for large-scale hydrazine hydrate manufacturing plants.

Description

Technical field [0001] The invention relates to a technology for recycling industrial waste residues, in particular to a technology for the separation and recycling of waste salt and alkali residues in the production of hydrazine hydrate. Background technique [0002] At present, domestic hydrazine hydrate manufacturers treat the waste salt-alkali residue produced in the production process (its composition is sodium chloride NaCl 70%, sodium carbonate Na 2 CO 3 10-15%, sodium hydroxide NaOH 2%, 0.5-0.6% hydrazine and amine) has not been effectively used, but directly discharged into rivers and lakes, causing serious water pollution. Summary of the invention [0003] The purpose of the present invention is to provide a technology for the separation and recycling of the waste salt and alkali residue in the production of hydrazine hydrate. [0004] The purpose of the present invention is achieved through the following ways: a technology for the separation and recycling of waste sal...

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Problems solved by technology

[0002] At present, domestic hydrazine hydrate manufacturers are concerned about the waste saline-alkali slag (its composition is sodium chloride NaCl 70%, sodium carbonate Na 2 CO 3 10-15%, sodium hydroxide (NaOH 2%, 0.5-0.6% hydrazine and amine) has not been effectively utilized, but directly discharged into rivers and lakes, resulting in serious water pollution

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