Technique for efficiently removing iron from kaolin

Abstract

The invention relates to a technique for efficiently removing iron from kaolin by magnetic separation, which is characterized by comprising the following steps: (1) purifying kaolin raw ore to obtain a magnetic separation raw material; (2) adding water to the magnetic separation raw material obtained in the step (1) to prepare a mixed slurry with the solid content of 10-20 wt%, adding sodium hexametaphosphate accounting for 0.2-0.6 wt% of the magnetic separation raw material, slurrying, stirring for 20 minutes, and passing through a 325-mesh wet sieve; (3) carrying out high-gradient magnetic separation on the undersize slurry of the 325-mesh sieve in the step (2): while controlling the magnetic field intensity of the high-gradient magnetic separator at 1.0-1.8T and the slurry flow rate at 0.8-1.8cm / s, the slurry is subjected to magnetic separation by the high-gradient magnetic separator to obtain a concentrate slurry; (4) adding alum accounting for 1-6 wt% of the concentrate slurry into the concentrate slurry obtained in the step (3), flocculating, carrying out pressure filtration, drying, and packaging to obtain a magnetic concentrate; and (5) calcining the magnetic concentrate obtained in the step (4) to obtain the calcined kaolin. The technique has the advantages of high iron removal efficiency and obvious whitening effect.

Description

Technical field [0001] The invention involves an efficient magnetic selection of kaolin, which belongs to the field of non -metalline mining and mining. Background technique [0002] As a good industrial mineral with excellent performance, it is widely used in ceramics, paper, rubber, plastic, petrochemical and other fields.Kaolin is mainly composed of kaolin stone ethnic minerals. It is a typical 1: 1 layer -like structured silicate. The chemical composition is mainly SIO 2 And Al 2 O 3 , Also contain a small amount of MGO, K 2 O, Fe 2 O 3 , TIO 2 wait.The existence of FE, TI and other chromosome elements seriously affects the whiteness of kaolin.Impurities often exist in the form of iron minerals, such as magnetite, titanium magnet ore, red iron ore, brown iron ore, diamond iron ore, yellow iron ore, magnetic yellow iron ore, etc.Gray, brown, pink, etc., while the whiteness is reduced.The dyeing effect of titanium is strong, which often makes the surface of Kaolin stone yellow....

AI Technical Summary

Problems solved by technology

[0004] Chemical iron removal methods are widely used, and chemical reagents such as bleaching agents are mostly used, but there are disadvantages such as high production costs, corrosive equipment, polluting the environment, and complicated operating processes.

Chinese patent CN101445249A provides a high-concentration pulp bleaching method for kaolin, that is, adding a hydrosulfate aqueous solution composed of an alkaline agent and hydrosulfite to the kaolin pulp with a concentration of 25-30%, to achieve the effect of kaolin bleaching, but corrosion equipment

Patent CN102583412A discloses a method of acid leaching kaolin with sulfuric acid as an acid leaching agent, and then using organic reducing agents such as formaldehyde and acetaldehyde instead of sodium hydrochloride as a whitening agent to reduce and remove iron from kaolin, but the process cost is high

Chinese patent CN101987480A relates to a method for preparing raw ore of kaolin without pickling, that is, using a strong reducing agent instead of sodium hydrosulfite to improve the whiteness of kaolin, and the iron removal effect is better than that of traditional hydrosulfite for iron removal and whitening, but this method produces High cost, polluting environment, complicated operation process

However, the method of adding brighteners has disadvantages such as high energy consumption, incomplete removal of impurities, serious environmental pollution, corrosion of equipment, and air pollution.

Selective flocculation method: Patent CN1101592A proposes a selective dispersion-flocculation iron removal process to remove fine iron impurities in kaolin, which can make the Fe content of kaolin ore 2 o 3 The content is reduced from about 1.83% to 1.13~1.24%, the iron removal rate is 33.99~42.80%, and the iron removal efficiency is low

Magnetic separation method: It is a kind of mineral processing method to realize the magnetic separation of minerals, and it is a traditional method of iron removal. However, the magnetic separation and iron removal effect of kaolin in the existing literature and patent reports is not ideal.

In Chinese patent CN1613818A, the kaolin is first rammed, graded by a three-stage cyclone, classified by a horizontal screw, high-gradient magnetic separation, chemical bleaching, surface activation treatment, centrifugal dehydration, dehydration by pressure filtration, ultrafine grinding, drying, ultrafine grinding, Drying, ultra-fine grinding, adding dispersant and water to the filter cake and breaking it into a slurry with a solid content of 55-60%, adjusting the pH value of the slurry to 5.5-6.0, and sending it to a peeling machine for ultra-fine grinding. After a series of iron removal and grinding processes, the whiteness of kaolin products reaches 87.4%, but the process is complicated, the production cost is high, and the iron removal rate is low; Chinese patent CN102092724A provides a production method of modified kaolin, which uses a magnet machine to remove iron, so that Slurry Fe 2 o 3 The content of iron is reduced from about 1.10% to 0.7~0.8%, the removal rate of iron is 36.36%, the efficiency of iron removal is low, and the energy consumption is large

Zhu Yongjie et al. (China Non-metallic Mineral Industry Guide, 2007 (4), 27-29) used North Sea kaolin as raw material to remove iron by superconducting magnetic separation. The iron removal rate was about 30%, and the whiteness of firing increased by 2~4. %; Mo Changlu et al. (Nonmetallic Minerals, 2009, 32 (Supplement), 9-10) took the North Sea kaolin as the research object for superconducting magnetic separation, and found that the treatment effect at a high magnetic field intensity of 5T is obvious, Fe 2 o 3 The highest content is reduced from 0.83% to 0.61%, and the iron removal rate is 26.5%. The magnetic field strength is high but the iron removal efficiency is low; Fe content of high iron kaolin in Donggong Cave mining 2 o 3 The content is reduced from 0.71% before magnetic separation to 0.23~0.28%, and the whiteness of firing (calcination at 1280°C) is increased from 82.5% to 93.2%. The iron removal effect is very good, and the iron removal rate is 60~67.6%. Magnetic separation parameters are not specified in detail, and for Donggong Cave mining kaolin (I grade kaolin Fe 2 o 3 content 2 o 3 content>1.10%) poor applicability

[0006] To sum up, there are certain deficiencies in the iron removal process of kaolin at present, such as high production cost, complicated operation, low iron removal efficiency, serious environmental pollution and equipment corrosion in industrial engineering.

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