CHAPTER XXXVI. 

 CLINKER COOLING, GRINDING, AND STORAGE. USE OF GYPSUM. 



THE clinker, issuing hot from the rotary kilns, must be very finely 

 ground in order to convert it into cement. This involves cooling the 

 clinker previous to grinding; otherwise the hot clinker would be 

 difficult to handle both in transportation and in the pulverizing ma- 

 chinery. A third requisite of the process is that either the clinker or 

 the ground cement must be seasoned,- in some way, in order to slake 

 any free lime that may be present. Modern clinker invariably contains 

 some free lime, and while its effects may be masked by the free use of 

 gypsum, it is advisable to give it as much opportunity as possible to 

 slake and become inert. 



In the present chapter, therefore, the subjects of clinker-cooling, 

 clinker-grinding, the use of gypsum and cement storage will be taken 

 up. 



Clinker-cooling. 



General methods of clinker-cooling. Methods of clinker-cooling vary 

 exceedingly in their processes and effectiveness. At one extreme might 

 be placed the device, used at one plant only, of receiving the clinker 

 from each kiln in a shute which passes through the wall of the kiln build- 

 ing and deposits the clinker in a heap on the ground outside. This is, 

 of course, a remarkably simple process, mechanically, but as it involves 

 hand-labor to an alarming extent it is hardly probable that any other 

 American plants will take it up. At the other extreme is, decidedly, 

 the Atlas two-stage cooling system. 



Omitting the crude device first mentioned above, clinker-cooling 

 systems may be roughly grouped as follows: 



(1) Pan conveyors, rolls, and sprinkling. 



(2) Stationary tower coolers. 



(3) One-stage rotary coolers. 



(4) Two-stage (Atlas) rotary coolers. 



These methods will be briefly discussed in the order named. 



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