Mance: Quarry Industry of Southern Indiana 



81 



The following formula is given for the determination of the 

 heating value of a coal from its ultimate analysis: 



Heating value in B.T.U. equals 14,500 C plus 62,100 (H - — ) plus 4,000 S 



8 



In this formula the letters C, H, 0, and S represent the weight 

 of carbon, hydrogen, oxygen, and sulphur in a pound of fuel. 

 It will be readily seen that the weight of the carbon has been 

 multiplied by the heating value of one pound of carbon burned 

 into carbon dioxide, plus the weight of the sulphur, multiplied 

 by the heating value of one pound of sulphur burned into sulphur 

 dioxide; and to this is added the amount of heat generated by 

 the combustion of the hydrogen not already united with the 

 oxygen present. The amount of this hydrogen is determined by 

 subtracting one-eighth of the amount of the oxygen present from 

 the hydrogen present. This is done because the hydrogen and 

 oxygen unite by weight in the ratio of 8 parts of oxygen to 1 part 

 of hydrogen. Therefore for every 8 parts of oxygen present 1 

 part of hydrogen is made useless for heating. For example, take 

 a coal of the following composition: moisture 17 per cent, sulphur 

 2 per cent, hydrogen 6 per cent, fixed carbon 55 per cent, and 

 oxygen 20 per cent. The computation would be as follows: 



.20 



(62,100 times (.06- — )) + (14,500 times .55) + (.02 times 4,000) 

 ^ =10,242.5 B.T.U. 



This heating value is only realized when enough oxygen 

 is furnished to the fire to completely burn the carbon into carbon 

 dioxide. Whenever the supply is insufficient the carbon passes 

 off in the form of carbon monoxide, and only about one-third of 

 the theoretical heat of the carbon is realized. This is the strong- 

 est reason for good draft and good draft equipment. In 

 fact, the analysis of the flue gases from any boiler plant will show 

 the presence of carbon monoxide, and the amount present will 

 be a direct measure of the heat that is being derived from the 

 coal burned. 



The air required for the combustion of a pound of coal can be 

 figured from the example given above as follows: 



Twelve parts by weight of carbon unite with 32 parts of oxy- 

 gen; 8 parts by weight of oxygen unite with 1 part of hydrogen; 

 and 1 part of sulphur by weight unites with 1 part of oxygen. 



Therefore the coal of the analysis used in the other problem 

 would need 



