Abstract A process and apparatus are provided for the production of aggregate coated with bituminous material, including tarmacadam, bitumen macadam, fine cold asphalt and hot rolled asphalt. The process involves check weighing a batch of aggregate passing it into a rotary batch heater, where the aggregate is heated to the desired temperature which the batch is being heated the exhaust gases produced by the heater carry smaller particles of aggregate out of the heater and these are collected in a multitubular cyclone-type collector. When the batch in the heater reaches the desired temperature it is fed to a mixer along with the appropriate quantity of heated bitumen and the particle collector is arranged to automatically feed the small particles collected from the batch during the heating step into the mixer. This ensures that the resultant mix does not vary from specification.
Apparatus for the production of aggregate coated with bituminous material which comprises a rotary batch heater for heating a correctly proportioned batch of aggregate, said heater having an outlet which communicates with a particle collector, a mixer for receiving the batch of heated aggregate and bituminous material, means for feeding the batch of aggregate to the mixer after heating and means for feeding the particles collected from the batch to the mixer, said particle collector comprising at least one cyclone comprising a tube which is open at both ends and is uniform in diameter for a substantial part of its length but tapers towards its lower end, a series of holes being formed in the wall of said tube, whereby in use a stream of air is directed transversely into the tube and passes through the holes thereby creating a vortex in the tube and small particles of material carried in the stream of air are collected and fall from the tapering end of the tube.
Claim 2
Dependent Claim
25 words
Apparatus according to claim 2 in which a secondary collector is provided to collect fine dust carried in the stream of air from the cyclone.