Abstract: A method and apparatus for the preparation of coaldust for use with a preheater and a cement calcination apparatus. Exhaust gas from the preheater is mixed with a source of coal and input to a pulverizing mill. The output of the pulverizing mill passes through an air current separator and a cyclone separator. The output of the air-current-separator, a stream of coal gravel, is supplied as a fuel at a calcination point in the calcination apparatus. The exhaust output from the separator provides an input to the cyclone separator which separates coaldust from the gas. The exhaust from the cyclone separator is in part fed-back to a calcination point in the calcination apparatus and is also a part of the stream of gravel. The entire process is closed so that no burnable coaldust is lost to the atmosphere.

Abstract: A drying-grinding apparatus including two types of grinding means, one being arranged to produce a relatively coarse ground product, and the other being arranged to produce a relatively finely ground product. A drying gas is introduced into each of the grinding means, and a common conduit delivers the ground products from both of the two grinding means into a sifting means. The sifting means discharges relatively coarse particles into a metering means which receives the output from the sifting means and separates the same into two fractions one of which is returned to the coarse grinding means, and the other of which goes to the fine grinding means.