Kaolin comprehensive utilization technology (1)

(1) List the comprehensive utilization of technical methods and processes using the following methods to process kaolin

1. Dispersion of mud

In the kaolin wet-sorting process, the raw ore is firstly made into a slurry, so that the minerals are dissociated in water in the form of granular monomers, and the particle size is in micrometers or even smaller. In order to kaolinite minerals and mineral impurities (such as quartz, feldspar, mica, pyrite, titanium, iron, etc.) separation, it is necessary that the clay particles into fine, medium, coarse grain three stages. The kaolin particles have opposite charges at the interface, and the particles attract each other to cause flocculation and flocculation. Therefore, it is necessary to add a suitable dispersing agent to ionize and attach it to the surface of the charged kaolin, so that they have the same electric charge and mutual rejection, then this time the slurry has fluidity (slurry concentration is generally 5 - 14%). The mineral particles in the pulp can only be effectively classified and sorted if they are fully dispersed. Generally, the clay suspension exhibits a neutral state - alkaline (pH = 8) , which shows a stable dispersion state. Commonly used dispersants are as follows:

Adjust pH : sodium hydroxide (NaOH) , sodium carbonate (Na ₂ CO ₃ ) . Precipitated Ca ²⁺ : ammonium oxalate [ (NH ₄ ) ₂ C ₂ O ₄ · H ₂ O ]

Complex Al ³⁺ , Fe ³⁺ : sodium citrate (Na ₃ C ₆ H ₅ O ₂ · 2H ₂ O)

Complexed polyvalent metal ions: sodium silicate [Na ₂ O (1.6-4) SiO _2], sodium pyrophosphate _{(Na 4 P 2 O 4 ·} 10H 2 O), sodium hexametaphosphate [(NaPO _{3) 6} 〕

2 , sand removal

Wet sand removal, which mainly removes coarse impurities such as quartz, feldspar, mica and other detrital minerals and cuttings, and also removes some iron-titanium minerals. It is commonly used in sputum float type classifiers, spiral classifiers, hydrocyclones and vibrating screens. Small mines in China use natural sedimentation to remove sand, then enter the sedimentation tank to concentrate, and dewatering and drying after sedimentation to produce brick-like kaolin billets. This product is generally used in the ceramic industry. In mechanized beneficiation plant, the pulp was removed to tamper with uniaxial grit portion, and then into the hydrocyclone desander further or vibrating sieve. According to reports, there is a new type of equipment for sand removal in the world - industrial type turbine ( West Germany ) . After industrial appraisal, it can replace the production process of spiral classifier and vibrating screen used in existing production.

3 , classification

At present, China produces high-grade products, especially paint-grade kaolin products, mainly using a classification method. In the process of paper coating processing, the 2 μ m particle size content has always been used as the control point of the work index, and the particle size is required to be as uniform as possible, which is less than 2 μ m , and it is necessary to prevent over-grinding during grinding, so it must be classified. The so-called grading is to use the difference in the size or density of the mineral particles to separate the minerals. If the mineral granules that make up the pulp have a large difference in particle size, they are generally classified by a sieve; if they are similar, they are sorted according to their density differences. Commonly used grading equipment are water rafts, hydrocyclones, centrifuges, and the like.

The super-segmentation level of kaolin deep processing technology adopts horizontal spiral centrifuge in foreign countries. In the horizontal spiral centrifuge of general structure, the coarse and medium particles are difficult to settle due to the agitation of the spiral, and take away with the overflow. At the same time, a considerable portion of the fine particles are pushed by the screw to the slag discharge port, which makes the classification effect not good. At present, the advanced and perfect particle classification device in foreign countries is the first to launch the patented centrifuge produced in the United States.

4 , magnetic separation iron

Almost all of the raw kaolin, contain small amounts (typically 0.5 --3%) of iron minerals, mainly iron oxides, ilmenite, siderite, pyrite, mica, tourmaline. These colored impurities are usually weakly magnetic so that these harmful impurities can be removed by magnetic separation. Magnetic separation is a method of separating mineral particles in a magnetic field by utilizing the magnetic difference of minerals, and is effective for removing high magnetic minerals such as magnetite and ilmenite or iron scraps mixed during processing. For weak magnetic minerals, one method can be first calcined and then converted into ferromagnetic iron oxide before magnetic separation. Another method is to use high gradient magnetic field magnetic separation.

( 1 ) High gradient magnetic field magnetic separation method

This method has two characteristics, one has to produce a high intensity magnetic field ⁽¹⁰⁷ Gauss / cm magnitude) poly magnetic media (typically steel wool), two screw tube is advanced magnet structure, high gradient magnetic separation technique It is very effective for removing weak magnetic fine particles or even colloidal particles in useful minerals. The advantages of this method are simple process, high output, low cost and no pollution. It can adjust the operating parameters to produce different grades of products, and can control the production cost as needed. It is a good and adaptable technology. , with good social and economic benefits. As early as the 1970s , many manufacturers in the United States used this technology to replace, in whole or in part, traditional methods of purifying kaolin such as flotation and chemical bleaching. Some kaolin companies in central Georgia have used high gradient magnetic separation as the standard treatment process. The disadvantage is that the equipment investment is high and the power consumption is large. Table 1 shows the results of iron and titanium removal tests on kaolin clay with different origins using PEM-5 high gradient magnetic machine.

It can be seen from the data in the table that in the high gradient magnetic machine beneficiation, the harmful impurity titanium is easier to remove than iron.

Table 1 PEM-5 high gradient magnetic separation results for kaolin in different producing areas

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