Air Classifiers are designed to separate a stream of particles into a COARSE and FINE fraction. The accuracy of this method of powder classification is high, but the efficiency can vary considerably.
The fine stream is generally constant in cut-point accuracy when process conditions are steady but the percentage of fine particles separated, compared to the population of fine particles in the feed, is rarely over 85%. This figure, known as the efficiency, can be much lower with some materials and also depends on the population of fine material – at the nominated cut-point – in the feed.
Generally the higher the population of particles to be separated, the higher the yield and the better the efficiency. The efficiency of separation is also product dependent: glass is relatively well behaved - i.e. separates cleanly, whereas products like cement or titanium dioxide have inter-particle attractions which negatively affect separation efficiency.