An air classifier mill applies impact grinding and air classification in one step. The mill uses airflow to convey feed
material to the mill’s grinding chamber, classifies the material into fine and coarse fractions, recirculates the coarse
fraction for further grinding, and conveys fine particles out of the mill, all in one continuous operation. or conditioned to
control temperature and humidity for
handling heat-sensitive or hygroscopic materials. The mill can be operated in a closed-loop system to allow the
conditioned air to be recycled or so that nitrogen or another inert gas can be substituted for air when handling a poten-
tially explosive material.
can be equipped with wear-protected internal components to handle materials with a Mohs
hardness up to 4; such construction is standard for largecapacity mills of 200 or more horsepower that handle min-
erals or other abrasive materials. Sanitary construction allows the mill to handle pharmaceutical and food-grade
products and applications with special cleaning requirements. When it’s not economical to replace the air with an
inert gas for handling a potentially explosive material, the mill and other equipment in the system can be designed to
withstand a 150-psi overpressure.
Unlike size reduction equipment for producing coarser particles, in which screens of various sizes control the final
particle size, the air classifier mill has an internal classifier wheel that can be easily adjusted during operation to rotate
at higher or lower speed, controlling the particles’final top size. Because classification takes place inside the mill
rather than in a separate machine or external operation, the mill is not only relatively compact but provides an eco-
nomic advantage over grinding mills that discharge to a downstream classification step.