Ball-mill feed rate

FIG. 20-15 Ore transit through a ball mill. Feed rate is 500 lb h. Courtesy Phelps Dodge Corporation.)... 

Ball mills Feed rate, W, ton/hr 1-30 ton/hr Cp = 45,000 Includes motor and drive... 

Tonnage to classifier per 24 hr. 610 tons, dry. (This classifier working in closed circuit with a ball mill. Original rate of feeding 280 tons per 24 hr.)... 

Variation of rate function with size of feed particles and size of balls mill. [Kelsall, Reid, and Restaiick, Powder Technol., 1(5), 291 (1968).]... 

A wet-process plant maldug cement from shale and hmestoue has been described by Bergstrom [Roc/c Prod., 64—71 (June 1967)]. There are separate facilities for grinding each type of stone. The ball mill operates in closed circuit with a battery of Dutch State Mines screens. Material passing the screens is 85 percent minus 200 mesh. The entire process is extensively instrumented and controlled by computer. Automatic devices sample crushed rock, slurries, and finished product for chemical analysis by X-rav fluorescence. Mill circuit feed rates and water additions are governed by conventional controllers. 

In the grinding operation of Fig. 13.3, a ball mill is in closed circuit with a hydrocyclone classifier. The mass flow rates of the classifier feed, oversize, and undersize are denoted by the symbols A, O,... 

For an open circuit ball mill 5 liters in volume operating at a flow rate of 1 liter per hr the product is a Z1O2 suspension with a Ros-lin-Rammler size distribution with a weight mean size of 0.5 jam and a volume to surface mean diameter of 0.7 jam. Determine the feed distribution to the mill assuming the value of j3 the grinding selectivity factor is 1.0 and k is 0.5 (hr/jam) . ... 

Feeding-rate control, for smooth operation. Setting control influences mainly product size and quality, while feed control determines capacity. Flow must also be synchronized with the feed requirements of downstream processes such as ball mills, and improved crusher efficiency can reduce the load on the more costly downstream grinding. 

Machines with up to 2500-kW installed power and 1000-ton/h (900-ton/h) capacity have been installed. The largest presses can supply feed for four or five ball mills. Operating experience (Wuestner et ah, loc. cit.) has shown that roll diameters of about 1 m are preferred, as a compromise between production rate and stress on me equipment. 

The actual grinding was carried out on a laboratory ball mill, using ceramic jars with dimensions of 5-13/16 internal diameter and 5-3/8" internal height. The overall volume is 1829cc. Initial experiments employed steel balls (seventeen of 3/4" diameter, eleven of 5/8" diameter and fifty of 1" diameter). The rate of jar rotation of the mill is nominally 80 rpm. The voltage and current feeding of the ball mill are measurable and constant therefore, the grinding time is used as a measure of power input. Experiments employed 100 g of coal. 

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