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A brief introduction to Air Classifying Mill

Views:0     Author:Site Editor     Publish Time: 2021-11-05      Origin:Site

The Air Classifying Mill is a vertical grinding mill, short for ACM, with an internal air classifying wheel and independent drive. It is typically used for milling heat sensitive materials and provides precise control of the "particle cutting point".

l Air Classifying Mills

l Models and range of options

l The Next Process

l Applications

Air Classifying Mills

These units require minimal maintenance and are capable of producing fine, medium and coarse grinding for a variety of materials in the food, pharmaceutical, chemical and mineral industries. The basic design incorporates impact size reduction in combination with an internal dynamic classifying that controls the exit (product) size by recirculating the coarse particles back into the grinding zone.

Seven factors determine the particle size distribution of the air classifying mill: Rotor type and speed as well as the number of liners and hammers affect the production of fines when changes occur. Separator type and speed affect the top size of the product. Finally, the airflow controls the throughput as well as the top size and fines production. With a range of options, the machine can be configured to process virtually any material below MOH hardness 5. In order to grind and reduce the size of the material, the product is fed into the grinding chamber by a feed screw or pneumatic conveying system through a rotary feed valve.

The material is processed through the high-speed grinding media, which causes the product to break up and be thrown by centrifugal force against the grinding chamber walls. This in turn causes further breakage of the product.

Models and range of options

Our air classifying mills are available in 15 model sizes from 1 HP to 600 HP for small batches and large production systems. They are available in narrow particle size distributions and wear-resistant options, including stainless steel, ceramic or tungsten. Due to the plant's air-to-material ratio requirements, heat-sensitive materials can be processed without compromising product quality. When grinding hygroscopic materials, conditioned inlet air can be used to reduce moisture in the system. In high temperature drying applications, the bearing housing can be insulated and air purged to protect the bearings. The mill can also be operated with cool air for heat sensitive materials to prevent build up and improve grinding efficiency.

The Next Process

The particles are routed through an induced air flow around the outer wall of the internal baffle assembly, which is equipped with an air baffle to laminarize the air flow. The laminar airflow and particles are passed to the internal classifying wheel, which rotates in the same direction as the rotor disc. Any oversized particles rejected by the classifying wheel are moved into the inner wall of the baffle and pushed downward by gravity and the pressure generated by the classifying mill. These oversized particles are then reworked into the grinding media where further impact occurs.

This cyclic action continues until all particles have passed through the classifying wheel.


Air Classifying Mills can be used for batch processing or continuous processing. All systems are designed to handle inert and explosive applications. Venting or sealing is required in such applications.

Typical Applications

Food Industry

Powdered sugar 12X and 14X grades


Very fine flours


Fine grinding of active pharmaceutical ingredients

Chemical industry

Dry adsorption powder


clay powder

Dye powder

Carbon powder


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