Mill Operations
Abraham Rodriguez
Kevin Santiago
March 24, 2014

A grinding mill is a machine used to break down solid material to smaller items. There are different styles of mills that are used and lots of different materials used during the process. Before big industries the most popular mills were hand mills such as a mortar and pestle. There was also the horse mill. Now we have wind mills and watermills. Most are now driven by electricity and vary in size depending on the item being made.
Ball mill
A ball mill is inclined or horizontal it is partially filled with balls of stone or metal and it grinds material to the manufacturing specifications. The material is feed into one end of the cylinder and the discharge is at the opposite end. Ball mills range in size depending on what is being made. They can be as small as a coffee machine to as big as 28 feet in diameter. The smaller versions of ball mills are common in laboratories that grind up material for quality assurance or sampling purposes.

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Rod mill
A Rod mill consists of a drum that causes friction between rods and particles. Rod mills are also equivalent to slitting mills. This type of mill makes rods of iron or different metal. They are less common than ball mills.

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Autogenous mill
Autogenous or autogenic mills are questionable because of the self-grinding of the ore: a rotating drum throws larger rocks of ore in a cascading motion that causes impact breakage of larger rocks and compressive grinding of finer particles. Its similar operating to a SAG mill as represented below however doesn't use steel balls within the mill.

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SAG Mills
SAG mills are primarily self-generated mills, but utilize grinding balls to help in grinding like in an exceedingly ball mill. A SAG mill is generally used as a primary or initial stage grinding resolution. SAG mills use a ball charge of eight to twenty first. the biggest SAG mill is 42' in diameter, supercharged by a twenty eight MW (38,000 HP) motor. A SAG mill with a diameter 44' in diameter has been designed with Associate in Nursing influence of thirty five MW (47,000 HP) (Z, Gl.)

Attrition between grinding balls and ore particles causes grinding of finer particles. SAG mills square measure characterized by their big diameter and short length as compared to ball mills. The mill is lined with raising plates to lift the material within the mill, where it then falls off the plates onto the rest of the ore charge. SAG mills are primarily used at gold, copper and platinum mines with applications in addition within the lead, zinc, silver, aluminum oxide and nickel industries (Pruftechnik)
Pebble mill
A rotating drum causes friction and attrition between rock pebbles and ore particles. Might even be used wherever product contamination by iron from steel balls should be avoided. Quartz or silicon oxide is usually used as a results of it's cheap to get.
High pressure grinding rolls
The high grinding rolls generally cited as HPGRs or roller press consists out of two rollers with identical dimensions that are rotating against each other with identical circumferential speed. The special feeding of bulk material through a hopper winds up in a material bed between the two rollers. The bearing units of one roller can move linearly and are ironed against the material bed by springs or hydraulic cylinders. The pressures inside the material bed are larger than fifty MPa. ordinarily they accomplish 100 to a few hundred MPa. By this the material bed is compacted to a solid volume portion of over eightieth. The roller press incorporates a particular similarity to roller crushers and roller presses