NationMaster - Encyclopedia: Mill (grinding)

A grinding mill is a unit operation designed to break a solid material into smaller pieces. There are many different types of grinding mills and many types of materials processed in them. Historically mills were powered by hand (mortar and pestle), working animal, wind (windmill) or water (watermill). Today they are also powered by electricity. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Middle Chinese (中古漢語, pinyin: zhōnggǔ Hànyǔ), or Ancient Chinese as used by linguist Bernhard Karlgren, refers to the Chinese language spoken during Northern and Southern Dynasties and the Sui, Tang, and Song dynasties (6th century - 10th century). ... A tomb is a small building (or vault) for the remains of the dead, with walls, a roof, and (if it is to be used for more than one corpse) a door. ... The Han Dynasty (Traditional Chinese characters: 漢朝, Simplified Chinese characters: 汉朝, pinyin Hàncháo 202 BC - AD 220) followed the Qin Dynasty and preceded the Three Kingdoms in China. ... The entrance to the Freer Gallery. ... Ore Extraction unit operations at Quincy Mine, Hancock, MI ca. ... Mortar and pestle Mortar used to pulverise plant material with liquid nitrogen A mortar and pestle are a pair of tools used in conjunction with each other to grind and mix substances. ... A working animal is an animal that doesnt live in the wild but is kept by humans, and often trained, to perform various tasks, regardless whether they are also used for consumption of meat and milk or for other produce such as leather etc. ... A Dutch windmill surrounded by tulips Spanish windmills at La Mancha Original seventeenth century wooden windmill, Gettlinge, Oland, Sweden. ... Watermill of Braine-le-ChÃ¢teau, Belgium (12th century) A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour or lumber production, or metal shaping (rolling, grinding or wire drawing). ... Lightning strikes during a night-time thunderstorm. ...

The grinding of solid matters occurs under exposure of mechanical forces that trench the structure by overcoming of the interior bonding forces. After the grinding the state of the solid is changed: the grain size, the grain size disposition and the grain shape.

With following aims is grinding very important for the process engineering:

magnification of the surface area of the solid ,
manufacturing of solid with wanted grain size,
making pulping of resources possible.

1 Grinding laws
2 Grinding degree
3 Grinding machines
4 Types of grinding mills
5 See also
6 External links

Grinding laws

In spite of a great number of studies in the field of fracture schemes there is no formula known, which connects the technical grinding work with grinding results. To calculate the needed grinding work against the grain size changing three half-empirical models are used:

KICK for d > 50 mm

$W_K=c_k*(ln (d_A) - ln (d_E)),$

BOND for 50 mm > d > 0.05 mm

$W_B= c_B*left(sqrtfrac{1}{d_A} - sqrtfrac{1}{d_E}right),$

RITTINGER for d < 0.05 mm

$W_R=c_R*left(frac{1}{d_A} - frac{1}{d_E}right),$

with W as grinding work in kJ/kg, c as grinding coefficient, d_A as grain size of the source material and d_E as grain size of the ground material.

A reliable value for the grain sizes d_A and d_E is d₈₀. This value signifies that 80% (mass) of the solid matter has a smaller grain size. The BOND's grinding coefficient for different materials can be found in various literature. To calculate the KICK's and RITTINGER's coefficients following formulas can be used

$c_K=1.151*c_B*(d_{BU})^{-0.5},$

$c_R=0.5*c_B*(d_{BL})^{0.5},$

with the limits of BOND's range: upper d_BU = 50 mm and lower d_BL = 0.05 mm.

Grinding degree

To evaluate the grinding results the grain size disposition of the source material (1) and of the ground material (2) is needed. Grinding degree is the ratio of the sizes from the grain disposition. There are several definitions for this characteristic value:

Grinding degree referring to grain size d₈₀

$Z_d=frac{d_{80,1}}{d_{80,2}},$

Instead of the value of d₈₀ also d₅₀ or other grain diameter can be used.

Grinding degree referring to specific surface

$Z_S=frac{S_{v,2}}{S_{v,1}}=frac{S_{m,2}}{S_{m,1}},$

The specific surface area referring to volume S_v and the specific surface area referring to mass S_m can be found out through experiments.

Pretended grinding degree

$Z_a=frac{d_1}{a},$

The discharge die gap a of the grinding machine is used for the ground solid matter in this formula.

Grinding machines

In materials processing a grinder is a machine for producing fine particle size reduction through attrition and compressive forces at the grain size level. See also crusher for mechanisms producing larger particles. Attrition means wearing down by friction or grinding and may refer to the following. ... Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ... In physics, force is an influence that may cause a body to accelerate. ... A crusher is a machine designed to reduce large solid chunks of raw material into smaller chunks. ...

Image File history File links No higher resolution available. ...

Ball mill

A typical type of fine grinder is the ball mill. A slightly inclined or horizontal rotating cylinder is partially filled with balls, usually stone or steel, which grinds material to the necessary fineness by friction and impact with the tumbling balls. The feed is at one end of the cylinder and the discharge is at the other. Ball mills are commonly used in the manufacture of Portland cement. A ball mill, a type of crusher, is a cylindrical device used to grind (or mix) materials like ores, chemicals, ceramics and paints. ... A sphere is a perfectly symmetrical geometrical object. ... The rocky side of a mountain creek near OrosÃ, Costa Rica. ... The steel cable of a colliery winding tower. ... Friction is the force that opposes the relative motion or tendency toward such motion of two surfaces in contact. ... Sampling fast set Portland cement Portland cement is the most common type of cement in general usage, as it is a basic ingredient of concrete, mortar and plaster. ...

Rod mill

A rotating drum causes friction and attrition between steel rods and ore particles. A right circular cylinder An elliptic cylinder In mathematics, a cylinder is a quadric surface, with the following equation in Cartesian coordinates: This equation is for an elliptic cylinder, a generalization of the ordinary, circular cylinder (a = b). ...

SAG mill

A rotating drum throws large rocks and steel balls in a cataracting motion which causes impact breakage of larger rocks and compressive grinding of finer particles. Attrition in the charge causes grinding of finer particles. SAG is an acronym for Semi Autogenous Grinding, and applies to mills that utilize steel balls in addition to large rocks for grinding.

Autogenous mill

A rotating drum throws large rocks in a cataracting motion which causes impact breakage of larger rocks and compressive grinding of finer particles. Attrition in the charge causes grinding of finer particles. Also known as ROM or "Run Of Mine" grinding.

Pebble mill

A rotating drum causes friction and attrition between rock pebbles and ore particles. May be used where product contamination by iron from steel balls must be avoided. Pebbles A pebble is a rock with a size of 4 to 75 millimeters (some say 64 millimeters). ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... The steel cable of a colliery winding tower. ...

High pressure grinding rolls

The ore is fed between two rollers which are pushed firmly together while their rotating motion pushes the ore through a small gap between them. Extreme pressure causes the rocks to fracture into finer particles and also causes microfracturing at the grain size level. The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... For fractures in geologic formations, see Rock fracture. ...

It consists of a pair of vertical cylindrical rollers through which material is passed. The two rollers rotate in opposite directions, "nipping" and crushing material between them. A similar type of intermediate crusher is the edge runner, which consists of a circular pan with two or more heavy wheels known as mullers rotating within it; material to be crushed is shoved underneath the wheels using attached plow blades. The force bearing on the axle has an eccentricity e with the point of contact to the rolling surface and exerts a moment about the contact point A wheel is a circular device capable of rotating on its axis, facilitating movement or transportation or performing labour in machines. ... For the constellation known as The Plough see Ursa Major. ...

Buhrstone mill

Another type of fine grinder commonly used is the buhrstone mill, which is similar to old-fashioned flour mills. The flour mill or grist mill is a kind of mill which is fed grain and makes flour. ...

Types of grinding mills

Ball mill
Colloid mill
Disk mill
Grist mill, also called Flour mill or corn mill
Hammer mill
Jet mill
Mortar and pestle
Oil mill
Wiley mill
Windmill

A ball mill, a type of crusher, is a cylindrical device used to grind (or mix) materials like ores, chemicals, ceramics and paints. ... A colloid mill is a machine that is used to reduce the particle size of a solid in suspension in a liquid, or to reduce the droplet size of a liquid suspended in another liquid. ... A disc mill, is a type of crusher that can be used to grind, cut, shear, shred, fiberize, pulverize, granulate, crack, rub, curl, fluff, twist, hull, blend, or refine. ... A grist mill is a place where grains are ground into flour. ... A hammer mill is a machine, which purpose is to shred material into fine particles. ... Mortar and pestle Mortar used to pulverise plant material with liquid nitrogen A mortar and pestle are a pair of tools used in conjunction with each other to grind and mix substances. ... The Wiley mill is a laboratory-scale machine for grinding materials to a powder. ... A Dutch windmill surrounded by tulips Spanish windmills at La Mancha Original seventeenth century wooden windmill, Gettlinge, Oland, Sweden. ...

External links

Animation of Horizontal Grinder

Categories: Mills | Tools | Mining equipment

Results from FactBites:

Grinding Mill - China Grinding Mill,Grinding Mills,Mill in Crushing & Culling Machine (231 words)
	Grinding Mill is newest high efficiency and lower consumption mill, which is studied by our engineers for solving the difficulty--high energy consumptionof ball mill.
	Grinding Millis no necessary to screening for it can be reach the mesh you want for one time...
	Compared with traditional grinding mill, This series Grinding Mill are of taking up small area, lower power consumption, longer service life, economical wearing parts, and higher performance cost ratio.

Historic Mills of Waterford, Virginia Mills (1304 words)
	During the milling, or grinding, phase, the wheat is reduced to flour.
	Mahlon's new mill was a custom mill, grinding not only wheat grown on his own land but also providing services for other farmers settling around "Janney's Mill." A sawmill operated adjacent to the large grist mill at various times during the 19th century, providing lumber for buildings.
	The mill operated from the late 1790s to the 1850s and is significant for its use as a woolen mill and manufactory.

More results at FactBites »

COMMENTARY

There are 1 more (non-authoritative) comments on this page

Share your thoughts, questions and commentary here

Want to know more?
Search encyclopedia, statistics and forums:

Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms.

Contents

Grinding laws GA_googleFillSlot("encyclopedia_square");