(CiRmisierapy || Technology of Gypsum. Oe) 
Fie. 18. Gypsum Backet Elevator. 
is used at the Chicago mill of 
the Western Plaster Works and 
in a number of the mills in 
Michigan. The capacity of a 
fifty-inch disintegrator is sixty 
to seventy-five tons in ten 
hours. 
After the gypsum is ground 
to flour it passes into another 
chain elevator and is carried to 
the top of the second story into 
the storage bin located just 
over the kettle. Figure 18 rep- 
resents the ordinary type of 
bucket elevator used in the gyp- 
sum mills. Some of the new 
mills are using a blower and 
air blast to drive the gypsum 
to the upper portion of the mill. 
This is anew method, and there 
seems to be some opposition to 
its use on the part of certain 
operators. 
The ground gypsum is run 
slowly from the storage bin 
into the calcining kettle, which 
is kept at a temperature of 212° 
F., or over, taking about one 
hour and a half to fill it to a 
depth of five feet. These ket- 
tles, as shown in Figures 19 
and 20, are constructed of boiler 
steel three-eighths of an inch 
thick, and are usually eight feet 
in diameter and six to eight feet 
deep. ‘They are set like a boiler upon a stone or brick base, and 
surrounded by a wall of stone about two feet thick with an air 
