ECKEL.] METHODS OF MANUFACTURE. f)~) 
duction of a barrel of Portland cement as being that which is necessary 
for the dissociation of 150 pounds of lime carbonate. With coal of a 
thermal value of 13,500 B. T. U., burned with only the air supply 
demanded by theory, this dissociation will require 25£ pounds of coal 
per barrel of cement, a fuel consumption of only {>.() per cent. 
LOSSES OF HEAT. 
In practice, however, heat is lost in a number of ways, and the fuel 
consumption is immensely greater than is theoretically called for. 
The more important ways in which heat is lost are as follows: 
(1) The kiln gases are discharged at a temperature much above that 
3f the atmosphere, ranging from 300° to 2,000° F., according to the 
;ypc of materials used and the length of the kiln. (2) The clinker is 
discharged at a temperature varying from 300° to 2,500° F., the range 
depending, as before, on materials and the length of the kiln. (3) The 
lir supply injected into the kiln is always greater, and usually very 
iiuch greater, than that required for the perfect combustion of the 
uel, and the available heating power of the fuel is thereby reduced. 
1) II eat is lost by radiation from the ends and exposed surfaces of 
he kiln. (5) The mixture, in plants using a wet process, carries a 
ligh percentage of water, which must be driven off. 
It is evident, therefore, that the amount of fuel actually necessaiy 
or the production of a barrel of cement is much above that required 
>y theory. 
ACTUAL FUEL REQUIREMENTS AND OUTPUT. 
Rotary kilns are nominally rated at a production of 200 barrels a day 
)er kiln. Even on dry and easily clinkered materials and with good 
oal, however, such an output is not commonly attained with a 60-foot 
iln. Normally, a 60-foot kiln working on a dry mixture will produce 
rom 160 to 180 barrels of cement each day of twenty-four hours. In 
oing this, if good coal is used, its fuel consumption will commonly 
e from 120 to 110 pounds of coal per barrel of cement, though it may 
ange as high as 160 pounds, and, on the other hand, has fallen as low 
s 90 pounds. An output of 175 barrels a day, with a coal consump- 
ion of 130 pounds per barrel, may therefore be considered as repre- 
enting the results of fairly good practice on dry materials with a 
0-foot kiln. In dealing with a wet mixture, which may carry any- 
here from 30 to 70 per cent of water, the results are more variable, 
hough always worse than with dry materials. In working a 60-foot 
iln on a wet material, the daily output may range from SO to 120 
arrels, with a fuel consumption of from 150 to 250 pounds per barrel. 
Ising a longer kiln, partly drying the mixture and utilizing waste 
eat, will of course improve these figures materially. 
