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Method for extracting chromium salt by oxidizing and roasting chromite with rotary hearth furnace and water method

A technology of oxidative roasting and chromite, which is applied in the direction of chromate/dichromate, etc., can solve the problems of low production efficiency, chromium slag pollution, ring formation, etc., and achieve high production efficiency, improve grade and recovery rate, The effect of uniform oxidation

Active Publication Date: 2014-07-16
SHENWU TECH GRP CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0018] Returning 70% of the leaching slag to the roasting system as filler, the production efficiency is relatively low, and there is a problem of chromium slag pollution; the rotary kiln is used as the roasting device, and there are problems such as "ringing"

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  • Method for extracting chromium salt by oxidizing and roasting chromite with rotary hearth furnace and water method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0043] Using a chromite ore as raw material, the main chemical composition is: Cr 2 o 3 47.30%; Fe 2 o 3 21.24%; Al 2 o 3 10.88%; CaO 3.33%; MgO 11.01%; SiO 2 2.41%. Chromite and soda ash are crushed to -0.074mm, accounting for 95.58%, the amount of soda ash added is 85% of the mass fraction of chromite, praseodymium oxide (Pr 6 o 11 ) is added in an amount of 1% of the mass fraction of chromite, and the amount of bentonite added is 8% of the mass fraction of chromite. Mix the materials evenly in the mixer; use water spray to make pellets, the diameter of the pellets is 10-12mm, and the amount of water spray is 10% of the chromite ore.

[0044]The formed pellets were dried at 300°C for 45 minutes, put into a rotary hearth furnace at 1200°C, and oxidized with air for 25 minutes. The oxidation rate of chromium in the clinker is 96.3%. After the clinker is leached, filtered and washed with water, the hexavalent chromium content in the slag is 0.082%, and the total chr...

Embodiment 2

[0046] Raw materials, proportioning, pelletizing, and drying are the same as in Example 1, except that the oxidation temperature in the rotary hearth furnace is 1250° C., and air is oxidized for 30 minutes. The oxidation rate of chromium in the clinker is 96.8%. After the clinker is leached, filtered and washed with water, the hexavalent chromium content in the slag is 0.079%, and the total chromium content in the slag is 0.87%.

Embodiment 3

[0048] Using a chromite ore as raw material, the main chemical composition is: Cr 2 o 3 47.30%; Fe 2 o 3 21.24%; Al 2 o 3 10.88%; CaO 3.33%; MgO 11.01%; SiO 2 2.41%. Chromite and soda ash are crushed to less than 0.074mm, the dosage of soda ash is 90% of the mass fraction of chromite, zirconia (ZrO 2 ) is added in an amount of 1.5% of the mass fraction of chromite, and the amount of bentonite is added in an amount of 6% of the mass fraction of chromite. Mix the materials evenly in the mixer; use water spray to make pellets, the diameter of the pellets is 12-15mm, and the amount of water spray is 12% of the chromite ore.

[0049] The prepared pellets were dried at 300°C for 30 minutes, put into a rotary hearth furnace at 1200°C, and oxidized with air for 40 minutes. The oxidation rate of chromium in the clinker is 97.5%. After the clinker is leached, filtered and washed with water, the hexavalent chromium content in the slag is 0.073%, and the total chromium content ...

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Abstract

The invention discloses a method for extracting chromium salt by oxidizing and roasting chromite with a rotary hearth furnace and a water method, comprising the following steps: chromite, sodium carbonate and catalyst are finely grinded and mixed uniformly, and the compositions are mixed according to the ratio as follows: the addition quantity of sodium carbonate is 70-90% of the mass of chromite; rare earth elements and oxide of Zr are selected as the catalyst, and the addition quantity of the catalyst is 1-2% of the mass of chromite; the addition quantity of bentonite is 5-10% of the mass of chromite; the uniformly-mixed raw materials are pelletized by water, the grain size of pellets is controlled in the range of 9-18 mm, and the volume of water used for pelletizing is 10-15% of the mass of chromite; and the raw material pellets are dried, and distributed in the rotary hearth furnace to be oxidized and roasted, so that chromium in the chromite is sufficiently oxidized into water soluble chromium salt capable of being separated from residues, the roasting temperature is 1200-1300 DEG C, and the roasting time is 20-40 min. The oxidization conversion rate of chromium in the chromite is high, the production efficiency is high, the chromite is oxidized uniformly, and the grade and recovery rate of products are improved.

Description

technical field [0001] The invention relates to a method for extracting chromium salts, in particular to a method for extracting chromium salts by oxidizing and roasting chromite in a rotary hearth furnace-water method. Background technique [0002] Sodium chromate is an important chemical product, widely used in the national economy, mainly used in printing and dyeing, electroplating, pigment, medicine, catalyst, oxidant and metal corrosion inhibitor. [0003] At present, sodium chromate is mainly prepared by oxidizing and roasting chromite, and the process includes calcium roasting and calcium-free roasting. The traditional calcium roasting is to oxidize and roast the mixed powder of chromite, calcium filler (dolomite, limestone), sodium carbonate and slag under high temperature conditions, so that the chromium in the ore can form water-soluble sodium chromate, The chromium salt product is obtained through subsequent treatment such as leaching. Due to the addition of a l...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01G37/14
Inventor 吴道洪王欣曹志成薛逊
Owner SHENWU TECH GRP CO LTD