June 02, 2020

Kaolin comprehensive utilization technology (5)

It can be seen from the reaction formula that the crystal water is removed between 500 and 700 ° C to form metakaolin, which remains in a sheet form. 925 °C The silicon spinel phase is then produced. 1100 °C It produces a mullite phase. 1400 °C Produce mullite.

The choice of kaolin calcination temperature depends on the application. As cable filler, chemical products, temperature should be selected 700 °C about. For the production of paper coatings, 800 should be selected . 900 °C At this time, the metakaolin formed still maintains a sheet form. When producing mullite, the temperature should be greater than 1400 °C . Produces high whiteness and high brightness fillers with temperature options 1000 °C about.

In order to increase the whiteness of the calcined kaolin, a calcining additive may be added. There are many varieties of additives, and it is necessary to rationally select additives according to the nature of the ore.

10 , surface modification

Kaolin is used for the filler of plastics, rubber, paint and cable. In order to make it easy to uniformly disperse with various organic polymer materials and to form a stronger bond, it is necessary to coat an organic coupling agent on the surface of kaolin. For surface modification. The coupling of the coupling agent to the kaolin is chemical reaction, physical adsorption or both. Commonly used coupling agents are silanes, titanates , aluminates , stearic acid and soaps thereof.

The modification method has a dry method and a wet method, and the dry method has a better effect than the wet method. Commonly used equipment is a high speed kneader. In the modified production, the kaolin is directly blended with the organic material at a certain temperature, and is carried out in a single-screw or twin-screw kneader.

The detection of the modification effect can accurately measure the coating area of ​​the coupling agent by infrared spectroscopy. A convenient method is to use a hydrophobic method. Take a little modified product, put it into a beaker containing water, stir it with a glass rod for one or two minutes, and observe the turbidity in the water after standing still. The kaolin with good modification effect is hydrophobic, which floats on the surface of the water without sinking.

(2) The process flow of comprehensive utilization of kaolin is shown in Table 5 .

Table 5   Kaolin mineral processing process

Ore type

Mineral processing principle process

Hard kaolin

1. Raw ore → crushing → slurry → cyclone → centrifuge → peeling → bleaching → paper coating grade

2. Raw ore → crushing → roasting → slurry → cyclone → peeling → centrifuge → paper coating grade → Packing level

Soft kaolin

1 . Raw ore→crushing→slurry→cyclone→selective flocculation→bleaching→quality papermaking, ceramic grade

2 . Raw ore → crushing → slurry → cyclone → centrifuge → stripping → magnetic separation → paper coating grade

Sandy kaolin

1. Raw ore → slurry → spiral classifier → sedimentation tank → centrifuge classification → stripping → bleaching → paper coating grade → packing grade

2 . Raw ore → slurry → re-selection sand removal → adjustment   with   Tank → Flotation → High-quality papermaking, ceramic grade

 

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