STATE GEOLOGIST. 319 
In grinding the clinker we require again intermediate and fine 
erinders. The intermediate grinder may be: 
Te Rolls: 
2. Kent mill. 
3. Disintegrator. 
4. Ball-mill. 
and the fine grinders: 
1. Griffin mill. 
Tube mill. 
wo 
What has been said in regard to the relative mechanical efficiencies 
under the head of raw grinding holds true also here and the economic 
values of these machines range probably in the order in which they 
are, givens One isource Of loss) inefficiency is the fact that the fine 
material produced in the intermediate grinding machines passes on to 
the fine grinding machine and hence lessens its efficiency to this 
extent. This seems to the writer one defect in the usual American 
mechanical outfit, but can be easily remedied by the insertion of a wind 
separator, of which there are many makes on the market depending 
on centrifugal action or on simple air blasting (see figure 59). In fact 
these machines are probably destined to revolutionize the present 
clinker grinding system by doing away with the fine grinding machine 
entirely. This could be done by selecting a machine which furnishes a 
high percentage of fine material, like the Kent or ball-mull, separat- 
ing out the finest by means of the wind separator and returning the 
coarse material to the grinding machine. This would undoubtedly 
cheapen the process considerably. 
The clinker grinding machines according to the present system might 
be arranged as follows: 
Rolls or Kent mill, or disintegrator, or ball-mill. 
Dust separator. 
Griffin or tube mill. 
The rolls, with two passes, have the greatest efficiency, showing 
probably the least cost of power. Their capacity is about 30 tons per 
hour with a consumption of approximately 100 horsepower. 
The. Kent mill, requiring 25 to 30 horsepower, has probably an 
output of from 22 to 28 barels per hour, preparing the clinker for the 
tube mill, depending on the hardness of the clinker. 
The disintegrator has been claimed by some manufacturers to be 
not very efficient for clinker grinding owing to the heavy expense for 
repairs, due to the direct impact of the rapidly revolving bars, which 
probably is true. The repairs for this machine in clinker grinding are 
considerably geater than in raw grinding, where it has proven very 
successful in every respect in a number of instances. 
