:: Russian Technology for Ultrafine Grinding Applications

Cyclotec, a St. Petersburg, Russia-based engineering firm that specializes in fine grinding technology, reports significant interest in its Planetary Centrifugal Mill (PCM). Cyclotec has advanced the project from the development stage to an industrial scale and has produced a prototype. Powered by a 37-kW motor, the prototype PCM has a production capacity of 1.5 mt/hr (continuous) and 100 kg/hr (periodic for nano grinding applications). In continuous grinding operations, milled material measured <5 microns with 30% as small as 1 micron.

The technology has potential for processing hard materials such as diamonds, slag, and cement, and would be well-suited for mobile applications. The developers claim that it offers extended run times and is designed to significantly reduce energy consumption. From a scientific perspective, Cyclotec claims an improvement for ground materials properties by reducing particle size to a molecular level and by making the substance mechanically active.

According to the developer, the PCM operates on a principle similar to a ball mill. In addition to rotation around a longitudinal axis, the drum also rotates around an axis of the motion of transport (e.g. planets rotating around the sun). The motion of transport "replaces" gravity acceleration (G) acting upon the balls in the ball mill, with a centripetal acceleration of the motion of transport, acting upon the balls in the PCM - and exceeding gravity acceleration by 10 to 300 Gs.

Cyclotecs PCM has four drums, each 164 mm in diameter x 250 mm long, capable of grinding wet or dry materials, with a centrifugal load factor of 30 Gs.

Initial size fraction is <5 mm. The unit can process 1.5 mt/hr of quartz sand and materials with a Mohs hardness of 10. Overall dimensions are 1.2-x 2- x 1.6-in, with a weight of 1,200 kg. The ball load for one drum is 9 kg.

Problems that have so far hindered emergence of a commercial PCM include the failure of standard roller bearings for the drums to operate at significant (>12 Gs) centrifugal loads; complexity of design for continuous loading and discharging of material; removal of excessive heat from the drums and bearings; and provisions for dust removal.

Following idle-state tests (without ball load) lasting 100 hr, disassembly of Cyclotec's unit showed no indication of bearing wear. A series of grinding operations with quartz sand and metallurgical slag was then carried out, and a consistent content of fine fractions (<5 microns) was observed in the first stage of grinding - up to 50% irrespective of the output and size of the initial material.

Cyclotec is currently working on the next test phase, involving continuous grinding of granulated slag.