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Method for pollution-free production of sodium chromate by pressure leaching of chromite

A technology of pressurized leaching and clean production, applied in the direction of chromate/dichromate, can solve the problems of complex extraction process, industrialization constraints, and difficult to remove, and achieves lower reaction temperature, easy comprehensive utilization, and slag discharge. small amount of effect

Active Publication Date: 2012-05-30
HUBEI ZHENHUA CHEMICAL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

But the disadvantage of this process is the introduction of NaNO 3 , so that Na 2 CrO 4 The crystal extraction process is complex and difficult; and during the reaction process, sodium nitrate is easily decomposed into sodium nitrite, which is difficult to remove, which greatly restricts the industrialization of this process

Method used

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  • Method for pollution-free production of sodium chromate by pressure leaching of chromite
  • Method for pollution-free production of sodium chromate by pressure leaching of chromite
  • Method for pollution-free production of sodium chromate by pressure leaching of chromite

Examples

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Effect test

Embodiment 1

[0040]In the autoclave, add chromite and 30% NaOH solution, the ratio of alkali ore is 10:1, heat to 300 ° C, then pass air into the solution, and stir evenly, so that the chromite ore can fully contact with oxygen , the total pressure of the control system is 8MPa, and the temperature is kept for 10 hours, so that the chromite ore can fully react with oxygen. Finally get NaOH and Na 2 CrO 4 and other solutions, sodium chromate crystals and iron-rich tailings, the conversion rate of the main element chromium in chromite is above 99%. Add water to dilute the reaction mixture, and then separate the solid and liquid to obtain iron-rich tailings and Na-containing 2 CrO 4 , NaOH and other solutions. Add appropriate amount of calcium oxide to the solution to remove impurities, evaporate and crystallize to obtain sodium chromate crystals. After the sodium chromate crystals are rinsed with a saturated sodium chromate solution and dried, a sodium chromate product with a purity of ...

Embodiment 2

[0042] In the high-pressure reactor, add chromite and 50wt% NaOH solution, the ratio of alkali ore is 6:1, heat to 280 ° C, then feed oxygen into the solution, and stir evenly, so that the chromite is fully in contact with oxygen , control the total pressure of the system to 6MPa, and keep it warm for 8 hours, so that the chromite ore can fully react with oxygen. Finally get NaOH and Na 2 CrO 4 and other solutions, sodium chromate crystals and iron-rich tailings, the conversion rate of the main element chromium in chromite is above 99%. Add water to dilute the reaction mixture, and then separate the solid and liquid to obtain iron-rich tailings and Na-containing 2 CrO 4 , NaOH etc., the follow-up process is the same as in Example 1.

Embodiment 3

[0044] In the high-pressure reactor, add chromite and 80wt% NaOH solution, the ratio of alkali ore is 2:1, heat to 200 ° C, then pass ozone into the solution, and stir evenly, so that the chromite and ozone are fully contacted , the total pressure of the control system is 0.5MPa, and the temperature is kept for 0.5 hours, so that the chromite ore can fully react with ozone. Finally get NaOH and Na 2 CrO 4 and other solutions, sodium chromate crystals and iron-rich tailings, the conversion rate of the main element chromium in chromite is above 99%. Add the iron-rich tailings washing solution obtained in Example 2 to dilute the reaction mixture, then separate the solid and liquid to obtain iron-rich tailings and Na2CrO-containing 4 , NaOH etc., the follow-up process is the same as in Example 1.

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Abstract

The invention belongs to the field of chromite hydrometallurgy and chromium chemical industry, and in particular relates to a method for the pollution-free production of sodium chromate by pressure leaching of chromite. The method comprises the following steps of: 1) reacting the chromite with oxidizing gas in solution of NaOH; 2) diluting the product obtained by the step 1) and making subcrystalline sodium chromate to fully enter a liquid phase; 3) performing solid-liquid separation on the solid-liquid mixed slurry obtained by the step 2); 4) adding calcium oxide into the obtained diluent for removing impurities; and 5) evaporating and crystallizing the obtained solution without the impurities to obtain a sodium chromate crystal and crystallization mother solution; after the solid-liquidseparation, rinsing the sodium chromate crystal by using saturated solution of sodium chromate; and drying to obtain a qualified sodium chromate product. The method has the advantages of simple reaction system component, no difficultly separated phase introduced in the system, contribution to high-efficiency separation of the sodium chromate, great reduction in reaction temperature, low energy consumption, effective reduction in production cost of the sodium chromate, and high chromium leaching yield.

Description

technical field [0001] The invention belongs to the fields of chromite hydrometallurgy and chromium chemical industry, and in particular relates to a method for producing sodium chromate through pressure leaching and clean production of chromite. Background technique [0002] Sodium chromate is an important industrial chemical product and is necessary for the production of other chromium compounds. Chromite is the direct source for the production of sodium chromate. [0003] During the mineralization process of chromite, chromium and other metal elements form a chromite spinel structure ((Mg, Fe)(Cr, Al) 2 o 4 ). This makes it difficult to separate chromium by mechanical grinding and beneficiation. The current methods of producing sodium chromate from chromite in my country mainly include calcium roasting method and calcium-free roasting method. When chromite ore is smelted using the traditional calcium roasting process, the conversion rate of chromium is low, only abou...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01G37/14
Inventor 徐红彬石义朗张懿蔡再华李佐虎程西川张小飞陈小红张洋刘静文
Owner HUBEI ZHENHUA CHEMICAL CO LTD
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