530 



CEMENTS, LIMES, AND PLASTERS. 



cylinder. These lumps being built up of small pieces loosely stuck 

 together differ entirely from the tough hard masses formed in a fixed 

 kiln fed with blocks or bricks of raw material, and are readily broken 

 up to the size of a hazelnut. The warm moist clinker passes down a 

 third rotating cylinder 60 feet long by 5 feet in diameter, lined with 

 hard cast-iron plates provided with shelves so as to toss and tumble 

 the pieces as they creep down. Air is drawn in through this cylinder 

 by means of a chimney which also carries off the water vapor from 

 the housing of the rolls. It is intended that the clinker shall emerge 



Ted Conveyor^- 



ELEVATI.ON 



FIG. 132. Atlas rotary two-stage coolers. (Engineering News.) 



from the end of the last cooling cylinder, in a slightly moist condition, 

 and to ensure this, regulation of the water at the rolls is supplemented 

 by a small jet at the end of the last cooler." 



This system is shown in Fig. 132, taken from the paper * below cited. 



Clinker-grinding. 



After cooling sufficiently to be workable, the clinker passes to the 

 clinker-grinding department of the mill. The problem before this 

 department is to reduce large quantities of an intensely hard and semi- 

 vitrified material to finely ground cement at the lowest cost possible. 

 This reduction is now usually accomplished in two or three stages. 



* Stanger, W. H., and Blount, B. The rotary process of cement-manufacture. 

 Proc. Inst. Civil Engineers, vol. 145, pp. 57-68. 1901. See especially p. 62 for 

 coolers. 



