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Method for improving conversion rate in the production of chromium by non-calcium roasting

A conversion rate, calcium-free roasting technology, applied in the direction of chromate/dichromate, etc., can solve the problems of high roasting temperature, high liquid phase composition, low chromium conversion rate, etc., to reduce the roasting reaction temperature and speed up roasting Reaction rate, effect of improving chromium conversion rate

Active Publication Date: 2012-08-08
GANSU JINSHI CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to provide a method for improving the conversion rate of chromium in calcium-free roasting, so as to solve the shortcomings of the traditional calcium-free roasting process, such as large amount of slag added, high roasting temperature, high liquid phase composition in the kiln, and low chromium conversion rate.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] The South African chromite (the main chemical composition is: Cr 2 o 3 42.8%, Fe 2 o 3 22.6%, MgO 8.22%, Al 2 o 3 18.62%, SiO 2 3.46%, V 2 o 5 0.33%) and self-produced slag, Jinchang soda ash (Na 2 CO 3 content: 98.62%) and chromic anhydride ground to 200 mesh with a pass rate of more than 95%, according to the mass ratio of chromite, soda ash, slag, and additives in the ratio of 20:17:62:2, mix well. Put it into a rotary kiln and feed air at a temperature of 1100°C, and the material is roasted in the kiln for a residence time of 5 hours, and the material does not form a wall. The oxidation rate of chromium in the roasted clinker increased from 75.2% without adding additives to 86.8%. The clinker is leached with water, and the leachate enters the subsequent process to produce chromium salt products. After the slag is washed, the loss of hexavalent chromium is 0.23%, and the total chromium content in the slag is 4.22%.

Embodiment 2

[0019] The South African chromite (the main chemical composition is: Cr 2 o 3 42.8%, Fe 2 o 3 22.6%, MgO 8.22%, Al 2 o 3 18.62%, SiO 2 3.46%, V 2 o 5 0.33%) and self-produced slag, Jinchang soda ash (Na 2 CO 3 content: 98.62%) and chromic anhydride ground to 200 mesh with a pass rate of more than 95%, according to the mass ratio of chromite, soda ash, slag, and additives in the ratio of 20:17:62:2, mix well. Put it into a rotary kiln and feed air at a temperature of 1150°C. The material is roasted in the kiln for a residence time of 4 hours, and the material does not form a wall. The oxidation rate of chromium in the roasted clinker increased from 76.0% without adding additives to 87.5%. The clinker is leached with water, and the leachate enters the subsequent process to produce chromium salt products. After the slag is washed, the loss of hexavalent chromium is 0.18%, and the total chromium content in the slag is 3.89%.

Embodiment 3

[0021] The South African chromite (the main chemical composition is: Cr 2 o 3 42.8%, Fe 2 o 3 22.6%, MgO 8.22%, Al 2 o 3 18.62%, SiO 2 3.46%, V 2 o 5 0.33%) and self-produced slag, Jinchang soda ash (Na 2 CO 3 content: 98.62%) and manganese ore ground to 200 mesh with a passing rate of more than 95%, according to the mass ratio of chromite, soda ash, return slag, and additives in the ratio of 20:17:62:5, mix evenly. Put it into a rotary kiln and feed air at a temperature of 1100 ° C. The material is roasted in the kiln for a residence time of 2 hours, and the material does not form a wall. The oxidation rate of chromium in the roasted clinker increased from 75.3% without adding additives to 89.2%. The clinker is leached with water, and the leachate enters the subsequent process to produce chromium salt products. After the slag is washed, the hexavalent chromium band loss is 0.21%, and the total chromium content in the slag is 3.68%.

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Abstract

The invention discloses a method for improving conversion rate in the production of chromium by non-calcium roasting to solve the disadvantages of great amount of return slag addition, high temperature of roasting, high liquid phase content in a kiln and low conversion rate of chromium in a traditional non-calcium roasting technology. An additive (chromic trioxide or manganese ore) is added in non-calcium roasting mixed material. The additive plays a role of accelerating roasting reaction, reducing reaction temperature of roasting and improving the conversion rate of chromium. Compared with a traditional roasting technology, the method provided by the invention has an unique advantage in energy saving and environmental protection, and have very obvious social, environmental, and economic benefits.

Description

technical field [0001] The invention belongs to the field of inorganic salt chromium salt production, and in particular relates to a method for improving the conversion rate of calcium-free roasted chromium. Background technique [0002] At present, there are mainly two methods of chromium salt production: calcium roasting and calcium-free roasting. Compared with the calcium roasting process, the biggest disadvantage of the calcium-free roasting process is that it does not add calcium-containing substances: 1. The conversion rate of chromium is low, generally 70-75%, while the conversion rate of calcium roasting can reach more than 90%; 2. The roasting temperature should not be too high. When the temperature is high, although the conversion rate of chromium can be increased, the liquid phase composition in the kiln will increase, which will easily form rings in the kiln and affect production. Contents of the invention [0003] The purpose of the present invention is to pr...

Claims

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Application Information

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IPC IPC(8): C01G37/14
Inventor 张忠元毛雪琴谢希智武平
Owner GANSU JINSHI CHEM