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Union Process “Q” and “QL” Attritors Achieve Ultra-Fine,

Uniform Dispersions Quickly and Consistently

© 2017, Union Process, Inc.


From a revolutionary idea proposed and developed by Dr.

Andrew Szegvari in 1945, Attritor technology grew to become

the basis for Union Process, Inc., an independent family-owned

American company founded in Akron, Ohio. Today, Attritors

are considered to be the most efficient grinding/dispersing

systems and are used in hundreds of industries and research

laboratories worldwide.

How Attritors Work

The Attritor is often referred to generically as an “internally

agitated high energy media mill.” The operation of an Attritor

is simple and effective. The material to be ground is placed

in a stationary tank with the grinding media. The materials

and media are then agitated by a shaft with arms, rotating at

high speed. This causes the media to exert both shearing and

impact forces on the material. The final result of this remarkably

efficient process is extremely fine material, measured in microns

or fractions of microns, distributed on a very narrow curve.

The Circulation Attritor

The circulation grinding Attritor (“Q” machine) is a

combination of an Attritor and a large holding tank which is

generally about ten times the size of the Attritor. The Attritor is

filled with media and contains grids which restrain the media

while the slurry is allowed to pass through.

The unique principle of the “Q” Attritor is the high circulating

(pumping) rate. The entire contents of the holding tank are

passed through the Attritor at least once every 7-1/2 minutes, or

about 8 times per hour.

This high pumping rate results in a faster grind and a

narrower particle size distribution. This phenomenon is explained

by the principle of preferential grinding (See Figure 1). The fast

pumping stream through the agitated media bed makes the

“Q” machine grinding chamber act as a dynamic sieve or filter,

allowing the fine particles to pass and move quickly through,

while the coarser particles follow a more tortuous path through

the media bed.

With the circulation process, unlike a continuous machine

with the slurry making a single pass, the material makes many

passes through the grinding chamber until the desired particle

size is obtained.

Grinding media used in circulation Attritors range in size from

3/32" to 1/4" in diameter. Chrome, steel, steatite, and zirconium

oxide are commonly used media.

Figure 1:

Passage Of A Small & Large Particle Through

A Layer Of Agitated Media

Retaining Grids





Holding Tank

The Union Process Advantage

From years of experience in designing and building thousands

of Attritors for use all over the world, Union Process has

developed the “know-how” to custom-design units for specific

requirements, whether for production or laboratory use,

employing either a dry or wet grinding process. Union Process

maintains a well-equipped laboratory and pilot plant where

actual production conditions can be simulated to assure that the

Attritor we build for you will satisfy your requirements. Skilled

technical service representatives are available for consultation.

They can arrange visits to customer and prospective customer

facilities to answer questions and provide solutions.

Advantages of Using a Circulation Attritor


Faster grinding with narrower particle size distribution


Uninterrupted, large-scale production


Excellent temperature control


Simple and safe to operate


Low maintenance and power consumption

Common Applications for Attritors


Paints, toners, inks




Agricultural flowables


Food products


Chocolate, confectionery


Paper coatings, calcium carbonate, clay






Metal oxides


Minerals, ores, coal


Sulphur dispersions

Retaining Grids