82 



Indiana University Studies 



( — times .55) plus .02, plus (8 times (.06— — )) equals 1.7667 pounds of oxygen 

 12 8 



Since air contains about 23 parts of oxygen by weight, in 

 100 parts, the air required would be 1.7667 times 100 divided by 

 23, equals 7.68 pounds of air per pound of coal burned. Since 

 1 pound of air at 62 degrees Fahrenheit has a volume of 13.14 

 cubic feet it would require 7.68 times 13.14, equals 100.915 cubic 

 feet of free air per pound of coal burned. Since these ideal 

 results cannot take place in the exact amounts as given for the 

 reason that the oxj^gen cannot all be brought in contact with the 



Plot 5 is given to show the fuel cost of different types of equipment. The cost 

 of bituminous coal is taken as S3 per ton. The plot is reproduced from Roger's 



Industrial Chemistry. 



combustible material to be burned, it is customary to figure 12 

 pounds of air per pound of coal burned, or in general 160 cubic 

 feet of free air. 



^Method and care in firing are very important in realizing all 

 the heat possible from the fuel burned, for altho a plentiful suppl}^ 

 of oxygen is necessary to the proper combustion of the coal, 

 an excess of air will cool the hot gases below their ignition points, 

 and cause them to pass off without being burned. Stoking may 

 be done either by hand or by mechanical stokers. The latter are 

 much more economical in large plants, but most of the small 

 plants of the stone district employ hand-stoking. The spread- 



