COMBUSTION 7 AND FUELS 79- 



in which X = calorific value of fuel, in B. T. U. per pound; 

 C = percentage of carbon, expressed as a decimal; 

 H = percentage of hydrogen, expressed as a decimal; 

 O = percentage of oxygen, expressed as a decimal; 

 5 = percentage of sulphur, expressed as a decimal. 

 EXAMPLE. A coal contains 85% of carbon, 4% of oxygen, 

 6% of hydrogen, 1% of sulphur, and 4% of ash. What is 

 the heat of combustion per pound? 



SOLUTION. Applying the formula, X = 14, 600 X. 85+62,000 



- I +4,000 X. 01 = 15,860 B. T. U. 



FUELS 



SOLID FUELS 



Fuels for Steam Making. The fuels used in the generation- 

 of steam are chiefly coal, coke, wood, petroleum, and natural 

 gas. Other fuels, such as the waste gases from blast furnaces, 

 straw, bagasse, dried tan bark, green slabs, sawdust, peat, etc., 

 are also used. All these fuels are composed either of carbon 

 alone or carbon in combination with hydrogen, oxygen, sulphur, 

 and non-combustible substances. 



Classes of Coal. Coal is the fuel most extensively used in 

 steam-plant work. Its different varieties may be classed in 

 four main groups, namely, anthracite, semianthracite, semi- 

 bituminous, and bituminous coal. 



Anthracite Coal. Anthracite coal contains from 92.31 to- 

 100% of fixed carbon and from to 7.69% of volatile hydro- 

 carbons. It is rather hard to ignite and requires a strong 

 draft to burn it. It is quite hard and shiny; in color it is a 

 grayish black. It burns with almost no smoke, and this fact 

 gives it a peculiar value in places where smoke is objectionable. 

 Anthracite coal is known to the trade by different names, 

 according to the size into which the lumps are broken. These 

 names, with the generally accepted dimensions of the screens 

 over and through which the lumps of coal will pass, are as 

 follows: Culm passes through A-in. round mesh. Rice passes 

 over Ts-in. mesh and through j-in. square mesh. Buckwheat 



