Gypsum

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            [post_content] => Mikro ACM® Air Classifying Mills were invented by HMPS in the late 1960’s and are one of the most versatile types of size reduction equipment available in the market. These units while being capable of producing fine, medium and coarse grinds for a wide variety of materials for Food, Pharmaceutical, Chemical and Mineral industries, require very little maintenance over their life span. The basic design of these mills is the impact size reduction that is coupled with an internal dynamic classifier which controls the outlet (product) particle size via recirculating the coarse particles back into the grinding zone.

There are seven main factors which determine particle size distribution for the Mikro ACM® Air Classifying Mill. When varied, the rotor type and speed combined with the liner and hammer count affects the production of fines. The separator type and speed affects the top size of the product. And lastly, the airflow governs the throughput as well as top size and fines generation. With the endless available options a machine can be configured to process just about any material that is below MOH’s hardness of 5.
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            [post_content] => The Mikro Pulverizer® consists of a high speed rotor assembly fitted with hammers. The grinding chamber is fitted with a cover containing a multiple deflector liner and a retaining screen at the point of mill discharge.

A screw mechanism is often used to introduce feed material into the grinding chamber. The grinding process is affected by three basic variables: the type of hammers, the rotor speed, and the size and shape of the screen opening.

There are two types of hammers: the “stirrup,” recommended where a fine particle size is desired; and the “bar,” which generates a coarser grind with a minimum of fines. Both types are tipped at the wearing edge with various abrasion resistant alloys. Rotor speed affects the fineness of the grind as follows: low speeds result in a coarse grind and high speeds produce a fine grind. Size and shape of the retaining screen openings also affect the product. In general, a finer screen opening will result in a finer grind. The retaining screen does not function as a sifting screen, except in coarse granulations.
Controlled Particle Size
Optimum particle size reduction can greatly affect chemical reaction speeds, solubility, weight, color, volume, appearance and strength of ground products. Mikro-Pulverizers® provide accuracy in particle size control because the grinding action is entirely mechanical. Once a mill is set to deliver a certain product, it will continue to produce exactly the same result without adjustment.
Grind, Blend and Disperse
Mikro Pulverizers® grind, blend and disperse in a single operation. Intensive action thoroughly mixes dissimilar ingredients into a finished product. Heat sensitive materials are handled by adjustment of mill speed, hammers, screen and discharge air relief, as well as with pneumatic conveying. Conditioned air may be bled into a grinding chamber, or the feed may be pre-conditioned or chilled. The Mikro Pulverizers® comes in many model sizes from small pilot scale to massive production models.
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Gypsum Milling & Grinding Solutions

Gypsum is Calcium Sulfate Dihydrate (CaSO4-2xH20). It is a mineral that forms from the evaporation of lakes / sea and is found in evaporite beds. It is also formed during flue gas desulfurization process in power stations.

Gypsum is used in construction, especially in sheet-rock and wall finishing. When heated, it loses its water of hydration, forming plaster, which can be used as a cement when adding water. Gypsum is also used extensively for agricultural for fertilizing and soil conditioning.

Pure calcium carbonate is a relatively soft mineral/compound, with a Mohs hardness of 2 (defining mineral). However, mined gypsum may have a minor portion of abrasive impurities such as quartz / sand.

One of the standard methods of milling Gypsum is with the Hosokawa Mikro ACM Air Classifying Mill. The ACM has a rotating rotor disc with hammers which rotates with speeds up to 23,000 feet per minute. The particle size is controlled by the internal air classifier, to provide sharp particle size distributions. Various classifier designs are available, to produce from coarse (100 mesh) product down to a fineness of 400 mesh product or a D50 of less than 10 microns. Abrasion Resistant options are available, including tungsten carbide tipping, Ni-Hard or Ceramic liners to assist with abrasive impurities and to assist with long life of mill components. Warm air can also be used to dry the product while milling.

An alternate to the Hosokawa Mikro ACM for coarser grade Gypsum is the Hosokawa Mikro-Pulverizer. The Mikro-Pulverizer uses swing-hammers with interchangeable screen liners to produce a variety of products from 50 mesh to 150 mesh products. The Mikro-Pulverizer needs less air (less ancillary equipment) than the Mikro-ACM and is a lower cost options for the coarser grind Gypsum products.

Contact Hosokawa’s mineral applications department to learn more about Gypsum Milling.

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Mikro ACM^® Air Classifying Mill

Mikro Pulverizer^® Hammer & Screen Mill

Controlled Particle Size

Grind, Blend and Disperse

Gypsum

Gypsum Milling & Grinding Solutions

Mikro ACM® Air Classifying Mill

Mikro Pulverizer® Hammer & Screen Mill

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