Clean production method for preparing sodium chromate from chromite

A technology of sodium chromate and chromite, which is applied in the direction of chromate/dichromate, etc., can solve the problems of equipment corrosion and high reaction temperature, and achieve the effect of reducing the amount of slag discharge

Inactive Publication Date: 2010-03-03
INST OF PROCESS ENG CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This technology can achieve a conversion rate of chromium greater than 99% under the condition that the mass ratio of sodium hydroxide to ore is 3:1-6:1, and the reaction

Method used

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  • Clean production method for preparing sodium chromate from chromite

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Experimental program
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Effect test

Embodiment 1

[0023] NaOH-NaNO recycled back to the reactor 3 Medium, after NaOH was added, the temperature was raised to 280°C, chromite was added, oxygen was introduced, and the reaction was carried out under complete mixing conditions for 6 hours, wherein the weight ratio of NaOH to ore was 4:1, and NaNO 3 The weight ratio with ore is 1:1. Finally get NaOH-NaNO 3 The mixed reaction product of medium, chromium salt and iron slag, the conversion rate of chromium is 99%. The mixed reaction product is leached with the iron slag washing solution, the lye is separated from the leaching slurry first, and then the iron slag is separated from the sodium chromate leaching solution; the sodium chromate solution is evaporated and crystallized, and the crystal is rinsed with water, The purity of sodium chromate crystals obtained after drying is 99.5%. After washing and drying the iron slag, it was determined that the total chromium content was 0.4%.

Embodiment 2

[0025] NaOH-NaNO recycled back to the reactor 3 Medium, after NaOH was added, the temperature was raised to 350°C, chromite ore was added, air was introduced, and the reaction was carried out under complete mixing conditions for 4 hours, wherein the weight ratio of NaOH to ore was 2:1, and NaNO 3 The weight ratio with ore is 0.6:1. Finally get NaOH-NaNO 3 The mixed reaction product of medium, chromium salt and iron slag, the conversion rate of chromium is 99.5%. The mixed reaction product is leached with the iron slag washing solution, the lye is separated from the leaching slurry first, and then the iron slag is separated from the sodium chromate leaching solution; the sodium chromate solution is evaporated and crystallized, and the crystal is rinsed with water, The purity of sodium chromate crystals obtained after drying was 99.0%. After the iron slag was washed and dried, it was determined that its total chromium content was 0.15%.

Embodiment 3

[0027] NaOH-NaNO recycled back to the reactor 3 Medium, after NaOH is added, the temperature is raised to 400°C, chromite is added, a mixed gas of air and oxygen with an oxygen volume content of 50% is introduced, and the reaction is carried out for 1 hour under complete mixing conditions, wherein the weight ratio of NaOH to ore is 1.5:1, NaNO 3 The weight ratio with ore is 0.2:1. Finally get NaOH-NaNO 3 The mixed reaction product of medium, chromium salt and iron slag, the conversion rate of chromium is 99.5%. The mixed reaction product is leached with the iron slag washing solution, the lye is separated from the leaching slurry first, and then the iron slag is separated from the sodium chromate leaching solution; the sodium chromate solution is evaporated and crystallized, and the crystal is rinsed with water, The purity of sodium chromate crystals obtained after drying was 98.8%. After the iron slag was washed and dried, it was determined that its total chromium content...

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Abstract

The invention relates to a clean production method for preparing sodium chromate from chromite, which comprises the following steps of: reacting the chromite with an oxidizing gas in a medium of NaOH-NaNO3-H2O, wherein sodium nitrate serves as a catalytic medium and is not consumed in the reaction; obtaining a mixed reaction product of an alkali liquor, the sodium chromate and iron slag after thereaction; leaching the mixed reaction product, performing liquid-solid separation of the alkali liquor and a crystal slag mixture (a mixture of a sodium chromate crystal and the iron slag), dissolvingthe mixture of the iron slag and the sodium chromate crystal, performing liquid-solid separation of the solution of the iron slag and the sodium chromate crystal, performing evaporative crystallization of the sodium chromate solution, rinsing and drying the obtained sodium chromate solution, obtaining qualified sodium chromate products; and circulating the crystallized mother liquor and the alkali liquor together to decompose the chromite. In the method, the chromium conversion ratio is above 99 percent and the chromium content ratio in the slag is less than 0.5 percent.

Description

technical field [0001] The invention belongs to the field of production methods of chromium salts, in particular to a clean production method of sodium chromate. Background technique [0002] Sodium chromate is an important industrial chemical, mainly used in the preparation of other chromium compounds, and also in the preparation process of ink, metal corrosion inhibitor and organic synthesis oxidant. [0003] Chromite is the most important raw material for the production of sodium chromate. The current method of producing sodium chromate from chromite in my country is mainly the calcium roasting method, which is characterized by using limestone, dolomite and part of the returned slag as fillers, and reacting at 1100-1200 ° C. After the reaction The clinker is obtained by leaching to obtain sodium chromate alkaline solution. The chromium conversion rate of this method is only 75%; the amount of slag discharged in the process is large, and 2.5 to 3 tons of chromium-containi...

Claims

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Application Information

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IPC IPC(8): C01G37/14
Inventor 郑诗礼张洋徐红彬王少娜张懿
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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