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ANNUAL REPORT: 
CHAPTER VIII. 
THE BURNING OF PORTLAND CEMENT—THE GRINDING 
OF THE CLINKER AND GENERAL ARRANGEMENT 
OF PLANTS. 
The raw mixture, fine ground, is now ready for burning, which is 
done, in American practice, almost exclusively in the rotary kiln, since 
this is by far the most economical and efficient apparatus for this purpose, 
in spite of its high fuel consumption. It consists essentially of a long 
tube of sheet steel, about 7-16 inch thick, usually 60 feet long and six feet 
in diameter, which is lined with fire brick forming a layer decreasing from 
g down to 4 inches 1n thickness. The tube is provided with two flanges 5 
inches wide, one 9 feet from the lower end, the other about 11 feet from 
the upper end, each running on two pairs of cast steel wheels, 22 inches 
in diameter and 6 inches face, which are apart a distance of 46 inches from 
center to center. 
The kiln is rotated by means of a cast iron or steel gearing about 24 
feet from the upper end, which is provided with expansion leaves, is 74 
inches in diameter, has a 6 inch face, 3 inch pitch and 75 teeth and consists 
of two parts. At the lower end 1s located a heavily bricked head supported 
by four cast iron wheels which vary from 1 to 2 feet in diameter and 
which enable the head to be moved away from the kiln. The shell is 
riveted flat on the inside, the rivets being 34 inch and spaced 4 inches from 
center to center. ‘The lining consists of the best grade of firebricks in 
the hottest zone of the kiln and the so-called blast furnace grade in the 
cooler portion. The stack is from 60 to 80 feet high, and 3 to 4 feet in 
diameter ; the lower forty feet consist of 3-16 inch sheet steel, the remain- 
ing part of 4% inch sheet steel with 7-16 inch rivets. 
According to the different requirements of different plants, the kiln 
is revolved slower or faster, the average velocity being about one revolu- 
tion per minute. The slope of the kiln is about 3 feet in 60 feet. By 
means of a single pipe, powdered coal dust is blown into the kiln, the blast 
being furnished by a fan blower. The ground mixture is introduced 
either through a pipe, if slurry, or by means of a screw conveyor, if dry. 
The kilns are sometimes arranged with a tapered receiving end 
for dry materials. The kiln is also provided with a speed Reg iallaicor. of 
which there are several types on the market. 
