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Clean method for preparing low-sulfur chromium oxide green

A technology of chromium oxide green and chromium oxide sulfur, applied in the directions of chromium trioxide, chromium oxide/hydrate, etc., can solve the problems of high energy consumption, high reaction temperature, complex reaction equipment, etc., and achieve the effect of zero emission

Inactive Publication Date: 2011-03-30
INST OF PROCESS ENG CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the reaction temperature of this method is too high, so that the energy consumption is very large; moreover, it is necessary to feed gas that can form salts with the reaction by-products, and the reaction equipment is complex

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0016] The reduction of 1000g of sodium chromate is carried out in a box-type reduction furnace, using hydrogen as the reducing gas, the reduction temperature is 450°C, the reduction time is 2h, and the hydrogen flow rate during the reduction process is 0.6L / min.

[0017] After the reduction product is cooled, it is washed with cold water. During the washing process, the liquid-solid volume ratio is 1.00-1.05, and the washing temperature is 20°C. Wash, filter, and dry to obtain an intermediate product, and the filtered liquid is a chromium-free NaOH solution for recycling.

[0018] The intermediate product was dry-milled in a ball mill according to a ball-to-material ratio of 20:1, a rotational speed of 300 rpm / min, and a ball milling time of 30 minutes to obtain a ground product. The lining material of the ball mill is ZrO 2 , the ball is ZrO 2 ball.

[0019] The ground product was subjected to hydrothermal leaching in an autoclave, the leaching temperature was 200° C., th...

Embodiment 2

[0023] The reduction of 1000g of sodium chromate is carried out in a box-type reduction furnace, using hydrogen as the reducing gas, the reduction temperature is 500°C, the reduction time is 2h, and the hydrogen flow rate during the reduction process is 0.6L / min.

[0024] After the reduction product is cooled, it is washed with cold water. During the washing process, the liquid-solid volume ratio is 1.00-1.05, and the washing temperature is 20°C. Wash, filter, and dry to obtain an intermediate product, and the filtered liquid is a chromium-free NaOH solution for recycling.

[0025] The intermediate product was dry-milled in a ball mill according to a ball-to-material ratio of 10:1, a rotational speed of 300 rpm / min, and a ball milling time of 60 minutes to obtain a ground product. The lining material of the ball mill is ZrO 2 , the ball is ZrO 2 ball.

[0026] The ground product is subjected to hydrothermal leaching in an autoclave, the leaching temperature is 220° C., the ...

Embodiment 3

[0030] The reduction of 1000g of sodium dichromate is carried out in a box-type reduction furnace, using hydrogen as the reducing gas, the reduction temperature is 550°C, the reduction time is 2h, and the hydrogen flow rate during the reduction process is 0.6L / min.

[0031] After the reduction product is cooled, it is washed with cold water. During the washing process, the liquid-solid volume ratio is 1.00-1.05, and the washing temperature is 20°C. Wash, filter, and dry to obtain an intermediate product, and the filtered liquid is a chromium-free NaOH solution for recycling.

[0032] The intermediate product was dry-milled in a ball mill according to a ball-to-material ratio of 5:1, a rotating speed of 300 rpm / min, and a ball milling time of 2 hours to obtain a milled product. The lining material of the ball mill is ZrO 2 , the ball is ZrO 2 ball.

[0033] The ground product is subjected to hydrothermal leaching in an autoclave, the leaching temperature is 180° C., the leac...

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Abstract

The invention discloses a clean method for preparing low-sulfur chromium oxide green. The chromium salt is taken as a raw material and a reducing gas is taken as a reducing agent; and the method comprises the following steps of: performing reaction on the chromium salt and the reducing gas at the temperature of between 300 and 800 DEG C for 0.5 to 5 hours; cooling, washing the reaction mixture with water, filtering, and drying to obtain an intermediate product; performing ball milling on the intermediate product at a rotating speed of 0 to 500rpm / min for 0 to 5 hours; hydrothermally leaching the ball milling product at the temperature of between 100 and 250 DEG C for 0 to 30 hours, washing, filtering and drying to obtain a leacheate; and calcining the leacheate at the temperature of between 600 and 1,300 DEG C in protective atmosphere to obtain the low-sulfur chromium oxide green and a byproduct of chromium-free sodium hydroxide. The chromium salt is sodium dichromate or sodium dichromate; and the reducing gas is hydrogen, natural gas, ammonia gas, coal gas or a mixture thereof.

Description

technical field [0001] The invention relates to a preparation method of calcined metal oxide, in particular to a clean preparation method of low-sulfur chromium oxide green by gas reducing agent low-temperature reduction of chromium salt Background technique [0002] Chromium oxide green is mainly used in metallurgy, pigments, abrasives, refractory materials, melt-blown materials, etc. It has the characteristics of corrosion resistance, light resistance, wear resistance, acid and alkali resistance. [0003] The production of chromium oxide green mainly adopts the thermal decomposition method of ammonium sulfate-sodium red alum (US4,040,860) and the thermal decomposition method of chromic anhydride. The production of chromium oxide green by thermal decomposition of ammonium sulfate-red alum sodium is the production method with the largest output and the most complete varieties. The advantage of this method is that it is suitable for large-scale production of rotary kilns, a...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01G37/033
Inventor 徐红彬李平张懿李佐虎
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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