532 CEMENTS, LIMES, AND PLASTERS. 



The following description of the clinker-grinding side of the plant 

 of the Hudson Portland Cement Co. has recently appeared in Engineer- 

 ing News. The layout of this plant is shown in Fig. 85, p. 407 : 



"The kilns are 60 feet long and 6 feet in diameter, and each is driven 

 by a 7^-H.P. electric motor. Fig. 4 is a view of the under side of the 

 kilns showing the rolls on which they run. The immense size of these 

 modern cement burners is excellently indicated by this illustration. 

 From the kilns the clinker is run into rotary coolers. There are five 

 of these, one for each pair of kilns. In these coolers the clinker is cooled 

 by a current of air which is blown in at the forward ends and passes 

 out of the rear ends into the trunk mains whence the air-pipes to the kilns 

 branch off. The coal is thus blown into the kilns by heated air. From 

 each cooler the clinker drops into a clinker pit and from these pits the 

 elevators G hoist it to the bins of the five Krupp ball mills. 



"From the ball mills the underground screw conveyor 14 and the 

 elevator H take the powder to the double hopper where the final adjust- 

 ment of proportions is made if necessary, and thence the conveyor 15, 

 the elevator HH, and the conveyor 16 take the powder to the feed-bins 

 of the seven tube mills, for final grinding. The discharge from the 

 tube mills is taken by the conveyor 16J to conveyor 26, which leads 

 to the storage-bins. 



"The course of the coal through the drier and grinders in the coal- 

 grinding room and thence by conveyor 24, elevator L, and conveyor 

 26 to the powdered coal-bins for the kilns can be readily traced from 

 the drawings, and need not be explained further here." 



Actual practice. The following data relate to the machinery 

 actually used on the clinker-grinding side of a number of American 

 plants and will serve to give a good idea of present practice in that 

 line: 



Plant No. 1. Dry process : 3 kilns, about 450 barrels per day. 



1 small jaw-crusher; 



2 ball mills; 

 2 tube mills. 



Plant No. 2. Dry process: 4 kilns, about 700 bbls. per day. 



1 rotary cooler; 



2 Smidth ball mills to 8 mesh; 

 1 Bonnot ball mill to 30 mesh; 

 4 tube mills. 



