CHAPTER III. 

 COMBUSTION OF COAL 



When coal is exposed to heat in a furnace, a por- 

 tion of the carbon and hydrogen, associated in 

 various chemical unions as hydrocarbons, are vola- 

 tilized and passed off. At a low temperature, 

 naphthaline, resins and fluids with high boiling points 

 are disengaged; at a higher temperature, volatile 

 fluids are disengaged; and at still higher, olefiant 

 gas, followed by common gas, light carburetted 

 hydrogen, which continues to be given off after the 

 coal has reached a low red heat. What remains after 

 the distillatory process is over, is coke, which is the 

 fixed or solid carbon of coal, with earthy matter, the 

 ash of the coal. 



TABLE NO. I. 



Taking the fixed carbon, or coke remaining in the 

 furnace after the volatile elements are distilled off, 

 at 60 per cent., in round numbers, the following is 

 an approximate summary of the condition of the 

 elements of average coal, after having been decom- 

 posed, and prior to entering into combustion : 



ioo POUNDS OF AVERAGE COAL IN THE FURNACE 

 Composition. Lbs. Decomposition. Lbs. 



Carbon Fixed 60 Fixed Carbon 60 



Carbon Volatilized 20 Hydrocarbons 24 



Hydrogen 5 Sulphur 1 1/4 



Sulphur 1 1/4 Water or Steam 9 



Oxygen 8 Nitrogen 1 1/5 



Nitrogen 1 1/5 Ash 4 



Ash 4 



100 

 About 100 



9 1 



