A feed passage 5 extends through one of the trunnions and suitable means such as screw conveyor 6 are provided for conveying the material to be ground through such passage and into the grinding chamber 7. A discharge passage 8 extends through the other trunnion and communicates with discharge spouts 9 and 10 for the ground material.bcone crusher spares for in South Africa A screen or perforated member 11 of suitable mesh may be provided for permitting only the iiner material to enter the discharge spout 19 hts.40min.any coarse material being discharged separately through spout 10. The mill as so far described is similar to several well known types of tube mills now in use, andthe specific construction thereof forms no part of my invention.In order to maintain inow and outflow of air or other gas through such a tube mill, the screw conveyor 6 maybe provided with a hollow shaft 13 connected through suitable stuif- -ing box 14 toinlet pipe 15, while outlet pipe 16 may be connected to the housing 17 at the discharge end of the mill, said outlet pipe leading to a fan or other means for causing gas to be drawn outwardly therethrough.

Any suitable means may be employed for lowering the relative humidity of the air or gas to be introduced into the tube mill. For example such gas may be passed over any suitable drying agent such as quick lime so as to remove a portion of the water vapor therefrom. For practical purposes, however, Iprefer to simply heat or warm the air or gas before entering the tube mill.Asphalt and asphalt concrete crusher For this purv pose a small heater 19 may be provided, as shown in Fig. 2, including burner means 20 and a heating coil 21 in position to be heated by the'flame from said burner. Air or other gas may be introduced or drawn in through pipe 22 to said heating coil, which is in turn connectedto inlet pipe such as 15 to the above described means for introducing the same into the tube mill.' A fan 24 is also shown in the outlet pipe 16, said fan being of relatively small size so as to cause only a, slow flow of gas through the tube mill. It will of course be understood that where a plurality of tube mills are in operation, a single heater and a single fan may be connected to all of said mills.

In carrying out the grinding operation in the apparatus above described, it will be understood that the usual charge of balls or A other grinding media is placed within the temperature above atmospheric temperature,I in any suitable manner before entering the tube mill, for example by mixing therewith a certain proportion of hot clinker as discharged from the kilns.Barite processing (crushing/grinding) plant The mixing of the hot clinker with the rest of the clinker and the drying and heating thereof may be satis factorily accomplished in the preliminary grinder which usually precedes the tube neoaeai mill 'in the grinding of Portland cement clinker. By thus heating the material fed into the tube mill the gaseous medium may be prevented from cooling materially while in said tube mill and may therefore be maintained at a low relative humidity.