1. Hydraulic classification
Hydraulic classification includes spiral classification (separation + 1mm coarse sand), sedimentation tank classification (separation + 0.053mm fine sand), hydrocyclone classification (separation of -0.053mm fine sand), centrifugal classifier or small diameter hydrocyclone classification (for 0.002 to 0.010mm ultra-fine grained classification).
Two, high gradient magnetic separation
The magnetic field intensity of more than 1 600kA/m can be produced by the magnetic medium, and the Fe2O3 and TiO2 in kaolin can be removed to produce paper coatings and advanced ceramic materials.
Three. Selective flocculation
By adding flocculants, selective separation of fine quartz, pyrite, alunite and other impurities, the production of scraper coated level kaolin. Commonly used flocculants include six sodium hypophosphite, ammonium polyacrylate and sodium silicate.
Four. Chemical bleaching
The high valent iron of limonite and hematite in kaolin is reduced to soluble ferrous in kaolin, or oxidizer is added to oxidize pyrite and dyed impurity to improve the whiteness of kaolin.
In the flaking machine, the stirring fine medium ball is used to produce grinding and stripping, and the kaolin aggregate particles are separated into thin sheet crystals, and the scraper coating grade kaolin, which has a grain size of less than 2 mu and more than 90%, is produced.
When calcined at 800~1000 C, kaolin has lost water, phase transformation, and some impurities volatilized, improving the whiteness and insulation of kaolin, producing cable and rubber plastic packing. Calcination is the necessary processing method for coal series (hard) kaolin.
Seven, surface modification
Kaolin was treated with coupling agent and so on. The addition of kaolin in plastic rubber was used to treat kaolin filler for rubber plastics.
Eight. Process flow
The processing of kaolin is divided into two processes: dry process and wet process.
The dry method usually breaks the raw ore to about 25mm by the crusher, and reduces the particle size to about 6mm in the cage crusher. The hot air blown into the cage crusher reduces the moisture content of kaolin to about 10% from 20%. The crushed ore is further grinded by the blow type Raymond mill with centrifuge and cyclone. The process can remove most of the sand and gravel, and is suitable for processing those ores with high whiteness, low sand content and suitable size distribution. Dry processing has low production cost, and products are usually used in low price filling materials such as rubber, plastics and paper industry.
Wet processing includes several stages, such as dispersion, classification, separation of impurities and product treatment. The general principles are as follows: raw ore, crushing, ramming, Desanding, cyclone classification, stripping slice, centrifuge grading, magnetic separation (or bleaching), concentrating, pressing, drying, ceramic or papermaking coatings.
The general principles for the processing of coal system (hard) kaolin are: raw ore, pulverizing, ramming, cyclone classification, stripping, centrifuge grading, concentration, pressure filtration, internal steam drying, calcining, depolymerization, packing grade or papermaking coating grade kaolin.