Coarse grinding

Almost all raw materials requite grinding after primary cmshing. For coarse grinding, a dry pan or occasionally a wet pan is used. The dry pan is similar to a grist mill but has a perforated bottom through which the cmshed material is continuously removed. The wet pan is similar, but has a soUd bottom. For very fine grinding, a ring-roll, ball, or impact mill is employed. 

Preliminary crushin coarse grinding Particle size fractionation (sieving) Homogenization... 

Primary molybdenum ores at a relatively coarse grind go through an initial stage of flotation. At Climax Molybdenum, for example, the first separation is made at 35% + 100 mesh. The flotation system uses vapour oil as a promoter and pine oil as frother. A sulfonated coconut oil (syntax) is added to the system to emulsify the oil. 

The San Rafael tin mine is one of the richest ore mine in the world, with a head grade of about 5% Sn. The mine actually started in the 1960s as a copper operation, and later tin was discovered and the operation started as a tin operation. The ore is coarse grained, and a portion of the tin was recovered at a relatively coarse-grind size (i.e. 8 mm size). The main gangue minerals found in this ore were silicates, pyrite, pyrrhotite, tourmaline and minor amounts of copper and silver. 

Iron media sizes are as follows for coarse grinding (+ 30----70 pm), for... 

The particle size of metallic silicon also has a noticeable effect on the chemical activity of contact mass in case of coarse grinding, the reactivity of powder is lower than required in case of fine grinding the reactivity rises sharply, and the heat has to be intensively diverted from the reaction zone. 

Crushers of different designs are large-scale machines for coarse grinding. They have throughputs of up to 35001 h-1, with a specific comminution work of 0.15-2.2 kWh H. The product particle size lies between 5 and 250 mm. 

Coarse grinding of the raw materials with crushers, pan grinders, hammer mills or cross beater mills is often carried out by the raw material suppliers. Thus in ceramic manufacture only fine grinding is required, for which wet grinding in ball mills, in which greater communition effects are realized than in dry mills, is satisfactory. 

The power required for operating Chilean mills is about five- to seven-tenths of a ton per horsepower-hour when producing a fine product. The capacity varies according to the work done. On comparatively coarse grinding, with slow-speed mills, in the neighborhood of 20 to 25 tons per hour may be reduced, while with high speeds this capacity is increased. 

FIG. 18-25 Viscosity of fine grind and coarse grind at various weight percent solids. 

FIGM NT5 must be insoluble and reasonably light-fast. They are prepared for use by grinding finely into a paste with a little water using a glass muller on a glass surfiace Of coarse, grind in a pesde and mortar first). For oil paint use oil instead oi water. 

After a coarse grinding (to a particle size of 2-10 mm) in a stainless steel mill, the material was packed in polythene lined containers and shipped to the Joint Research Centre of Ispra (Italy) for further processing. The material was then ground in a tungsten carbide mill. A fraction of the particles of 90-200 pm was sieved out this fraction was chosen in order to eliminate possible fine clay-like particles. 

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