Van Tongeren developed three models of air classifier in 1958, using knowledge of air flow gained through the earlier development of cyclones. The equipment is used to classify particles into different size ranges (as opposed to a cyclone, which is designed to collect particles of all sizes).
The three models were the gravitational, the gravitational inertial, and the centrifugal. The appropriate air classifier for a given application will depend on the properties of the particles to be separated.
Van Tongeren air classifiers keep the material dry, as opposed to wet classification methods which require additional drying, so the product may be used directly.
These air classifier designs contain no moving parts and require less maintenance than “whizzer” type equipment, which can require a significant amount of maintenance – particularly in the dusty environments where this equipment is typically used.
Van Tongeren has developed a mobile classification system which is employed on manufactured sand projects where multiple sites may be involved. The whole plant fits onto a standard truck base and utilizes a set of Van Tongeren high-efficiency multicell cyclones for exhaust gas clean-up.
Each of the above air classifiers can be used in series to split feed into various products. They are generally followed up by a cyclone or bank of cyclones for additional fine particulate removal. A final piece of particulate removal equipment – such as a bag house or cartridge filter – is added to meet pollution control requirements.