CRUSHING AND PULVERIZING MACHINERY. 435 



closeness with which the cylinders are set, it is obvious that we have here 

 a type of machine very different from the jaw crushers and cone grinders 

 previously discussed, for rolls can be used for either coarse or fine 

 grinding. 



By far the most extensive use of rolls in the cement industry is 

 made at the Edison plant at Ste warts ville, N. J., where all the crush- 

 ing and grinding on both the raw and clinker sides of the mill is accom- 

 plished in rolls. At other plants rolls are used, if at all, only for crush- 

 ing clinker, direct from the kilns, to a size that can be economically 

 handled by Griffin, Huntingdon or ball-mills. 



FIG. 90. View looking down between 5-foot rolls, Edison plant. 

 (Engineering News.) 



At the plant of the Edison Portland Cement Company the raw 

 materials are crushed and pulverized in a series of rolls of special design. 

 The elevation of this series is shown in Fig. 89, while Fig. 90 is a view 

 looking downward on one of the coarser sets of rolls. In Fig. 91 the 

 plan and elevation 'of the fine-grinding rolls of the Edison plant are 

 presented. 



With the exception of the Edison plant, however, rolls are rarely 

 or never used for fine grinding in Portland-cement practice on either 

 the raw or clinker sides of the mill. They are commonly used in coal 

 crushing, particularly when lump or run-of-mine coal is bought (see 

 pp. 514, 515) ; and in many plants they are used as a first reducer on 



