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Sodium chromate alkali solution impurity removal method and preparation method of chromic oxide

A technology of alkaline solution and sodium chromate, which is applied in the direction of chromium trioxide, chromium oxide/hydrate, chromate/dichromate, etc., can solve the problems of trivalent chromium loss and difficult elution of chromium, and achieve High conversion rate, low cost and stable operation

Active Publication Date: 2012-07-18
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

The problem is that the aluminum hydroxide of the second-stage carbon absorbs a large amount of hexavalent chromium in the solution, which is used as a seed crystal, and the chromium in the aluminum hydroxide is difficult to elute
The patent proposes that the filter cake is directly calcined without washing. The problem is that at high temperature, the carbonate in the chromium hydroxide reacts with the chromium oxide generated during the calcination process to generate hexavalent chromium again, resulting in trivalent chromium. loss of chromium

Method used

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  • Sodium chromate alkali solution impurity removal method and preparation method of chromic oxide
  • Sodium chromate alkali solution impurity removal method and preparation method of chromic oxide
  • Sodium chromate alkali solution impurity removal method and preparation method of chromic oxide

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Experimental program
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Effect test

Embodiment 1

[0039] Select sodium chromate alkaline solution from a chromium salt factory

[0040]

[0041] The alkaline solution obtained by calcium-free roasting is pumped into the first tank of the continuous carbon separation tank, and the temperature of the first tank is controlled to be 80°C. into CO 2 (high purity CO 2 Mix with air, volume fraction 55%), add aluminum hydroxide seed crystal, seed crystal coefficient is 0.3, carry out continuous carbonization, fully increase CO 2 utilization rate. The carbon final tank is separately fed into CO 2 , to fully precipitate the silicon in the solution. The cumulative decomposition time is 2h. The removal rate of carbon and aluminum is 99.9%, and the removal rate of silicon is 98.5%.

[0042] The aluminum slime obtained after carbon separation was countercurrently washed 4 times at a temperature of 80°C for 15 minutes. After carbon separation, the filtrate obtained by filtering is mixed with potato starch and pumped into continuou...

Embodiment 2

[0045] Select sodium chromate alkaline solution from a chromium salt factory

[0046]

[0047] The alkaline solution obtained by calcium-free roasting is pumped into the first tank of the continuous carbon separation tank, and the temperature of the first tank is controlled to be 90°C. into CO 2 (lime kiln gas, purification, compression, volume fraction 38%), add aluminum hydroxide seed crystals, the seed crystal coefficient is 0.2, carry out continuous carbonization, fully increase CO 2 utilization rate. The carbon final tank is separately fed into CO 2 , to fully precipitate the silicon in the solution. The cumulative decomposition time is 3h. The removal rate of carbon and aluminum is 99.9%, and the removal rate of silicon is 99.1%.

[0048] The aluminum slime obtained after carbon separation was countercurrently washed 4 times at a temperature of 80°C for 15 minutes. After carbon separation, the filtrate obtained by filtering is mixed with pregelatinized starch an...

Embodiment 3

[0051] Select sodium chromate alkaline solution from a chromium salt factory

[0052]

[0053] The alkaline solution obtained by calcium-free roasting is pumped into the first tank of the continuous carbon separation tank, and the temperature of the first tank is controlled to be 85°C. into CO 2 (calcination kiln gas, purification, compression, volume fraction 38%), adding aluminum hydroxide seed crystals, the seed crystal coefficient is 0.4, continuous carbon content, fully increase CO 2 utilization rate. The carbon final tank is separately fed into CO 2 , to fully precipitate the silicon in the solution. The cumulative decomposition time is 3.5h. The removal rate of carbon and aluminum is 99.9%, and the removal rate of silicon is 99.4%.

[0054] The aluminum slime obtained after carbon separation was countercurrently washed 4 times at a temperature of 80°C for 15 minutes. After carbon separation, the filtrate obtained by filtering is mixed with dextrin and pumped in...

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Abstract

The invention discloses a sodium chromate alkali solution impurity removal method and a preparation method of chromic oxide. According to sodium chromate alkali solution impurity removal, CO2 with rich resources and low cost serves as acidulant, aluminium and silicon are removed by continuous carbonating decomposition, and the removal rates of the aluminium and the silicon are high; new impurities are not introduced; and aluminium mud after sedimentation has thick and large particles, is low in chromium belt loss, and can be used in alumina industries after being filtered and washed, thus having a high added value. Impurities and sodium chromate solution are separated to obtain solution, cheap and rich starch and derivatives of the starch serve as reductants, and hydrated chromium hemitrioxide is prepared under a hydrothermal reducing condition, and then pigment-level chromium hemitrioxide is generated after dehydration and calcination. The reducing condition is mild, the conversion rate is higher than 90%, slurry easy to filter and wash, and final filtrate and alkaline rinse in production process can be returned to mix with chromite to enter a calcination process, thereby recycling sodium carbonate. According to the invention, the process adopted for generating the chromium hemitrioxide is simple and environment-friendly, the cost is low, and industrialization is easy to realize.

Description

technical field [0001] The invention relates to the field of chromium salt production, in particular to a method for removing impurities from sodium chromate alkaline liquid produced from chromium salt production soda and roasted chromite and chromium oxide. Background technique [0002] At present, my country's chromium salt industry mainly adopts two methods: calcium roasting and calcium-free roasting. Calcium roasting has a large amount of slag discharge and contains acid-soluble hexavalent chromium in solid solution, causing serious environmental pollution. And calcium-free roasting has a small amount of slag discharge, which is easy to handle. During the roasting process, some aluminum and silicon compounds react with sodium carbonate and enter the leaching solution, becoming the main impurities in the alkaline leaching solution. If the aluminum and silicon impurities in the alkaline solution are not removed, the performance of the product chromium oxide will be great...

Claims

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Application Information

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IPC IPC(8): C01G37/14C01G37/033
Inventor 曲景奎齐涛魏广叶郭强韩冰冰
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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