A kind of method for preparing sodium dichromate

A sodium dichromate and sodium hydroxide technology, which is applied in the preparation of chromate/dichromate, sulfate/bisulfate, etc., can solve the problems of high energy consumption, difficult treatment of chromium-containing slag, and high production cost , to achieve the effects of low energy consumption, avoiding the discharge of chromium-containing water, and low cost

Active Publication Date: 2017-08-25
格润过程(北京)科技有限责任公司
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  • Claims
  • Application Information

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Problems solved by technology

[0008] In the prior art, there are still defects such as difficult handling of chromium-containing slag, high production cost, and high energy consumption that need to be overcome. It is still necessary to optimize the production process of sodium chromate and sodium dichromate

Method used

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  • A kind of method for preparing sodium dichromate

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Embodiment 1

[0045] Chromite and sodium hydroxide solution are subjected to liquid-phase oxidation reaction, and the slurry is separated from solid and liquid after the reaction to obtain liquid phase A and solid phase B. Liquid phase A contains 60wt% sodium hydroxide and 8wt% sodium chromate, which is used for returning In the liquid phase oxidation reaction of chromite. The solid phase B is washed with circulating lye, the liquid-solid ratio of washing is 1.0, the washing temperature is 120°C, and the holding time is 1h. After washing, the slurry was separated into solid and liquid to obtain liquid phase C and solid phase D, and the concentration of sodium hydroxide in liquid phase C was about 42 wt%. Part of the liquid phase C is evaporated and concentrated to a sodium hydroxide concentration of 50 wt%, and used as a returned lye for liquid-phase oxidation reaction. The solid phase D uses water-dissolved crystals to obtain crystal-dissolving liquid and iron slag. An appropriate amount ...

Embodiment 2

[0047] The chromite is subjected to a liquid-phase oxidation reaction with the mixed solution of the returned lye and the liquid phase A, and the slurry is separated from the solid and liquid after the reaction to obtain the liquid phase A and the solid phase B. The liquid phase A contains 75 wt% of sodium hydroxide, chromic acid Sodium 5wt%, returned for chromite liquid phase oxidation reaction. The solid phase B is washed with circulating lye, the liquid-solid ratio of washing is 0.5, the washing temperature is 70°C, and the holding time is 3h. After washing, the slurry was separated into solid and liquid to obtain liquid phase C and solid phase D, and the concentration of sodium hydroxide in liquid phase C was about 51 wt%. Part of the liquid phase C is evaporated and concentrated until the concentration of sodium hydroxide is 70wt%, and used as the return lye for liquid phase oxidation reaction. Solid phase D uses water-dissolved crystals to obtain crystal-dissolving liqu...

Embodiment 3

[0049] The chromite is subjected to a liquid-phase oxidation reaction with the mixed solution of the returned lye and the liquid phase A, and the slurry is separated from the solid and liquid after the reaction to obtain the liquid phase A and the solid phase B. The liquid phase A contains 70 wt% of sodium hydroxide, chromic acid Sodium 7wt%, returned for chromite liquid phase oxidation reaction. The solid phase B is washed with circulating lye, the liquid-solid ratio of the washing is 1.5, the washing temperature is 50°C, and the holding time is 5h. After washing, the slurry is separated into solid and liquid to obtain liquid phase C and solid phase D, and the concentration of sodium hydroxide in liquid phase C is about 45 wt%. Part of the liquid phase C was evaporated and concentrated to a sodium hydroxide concentration of 62 wt%, and used as a returned lye for liquid-phase oxidation. The solid phase D adopts water-dissolving crystal to obtain crystal-dissolving liquid and ...

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Abstract

The invention discloses a method of preparing sodium dichromate, comprising the steps of (1), subjecting chromite and alkali solution to liquid oxidation, subjecting slurry to solid-liquid separation after reacting to obtain liquid phase A and solid phase B; (2), washing the solid phase B with circulatory alkali liquid, subjecting post-washing slurry to solid-liquid separation to obtain liquid phase C and solid phase D; (3), crystal-dissolving the solid phase D with sodium chromate crystal with water and iron residue washing liquid, carrying out solid-liquid separation to obtain crystal-dissolved liquid and iron residue, washing the iron residue with water, and returning the washing liquid to crystal dissolution; (4), preparing circulatory alkali liquid with the liquid phase C and crystal-dissolved liquid, adding an acid solution to the remaining crystal-dissolved liquid to adjust pH, and carrying out aluminum-silicon removal, acidifying, crystallizing and separating to obtain sodium dichromate and sodium sulfate; preparing. The process of the invention is simple, the flow is short, and the method is highly operable, low in cost and free of wastewater and is an effective way of chromium salt industry to make recycle use and reduce pollution.

Description

technical field [0001] The invention relates to the field of chromium salt production, in particular to a method for preparing sodium dichromate. Background technique [0002] The output of chromium salts in my country has accounted for 40% of the world's total. The overall scale of chromium salt factories is relatively large, and the production capacity has generally increased compared with before. The main methods of chromium salt production include calcium roasting method, calcium-free roasting method, sub-molten salt liquid phase oxidation method, carbon ferrochrome-sodium chromate combined method, sodium chromate-carbon ferrochrome combined method and molten salt method. But at present, the production technology adopted by my country's chromium salt industry is mainly a calcium roasting process, and the chromium conversion rate is only 75%. Every ton of red alum sodium produced discharges 2.5-3.0 tons of highly toxic chromium slag containing calcium chromate. Calcium-f...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01G37/14C01D5/02
CPCC01D5/02C01G37/14
Inventor 魏广叶曲景奎齐涛余志辉
Owner 格润过程(北京)科技有限责任公司
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