Exercise-2

2) A furnace heats the billet. The furnace is heated by combusting coal with air. The ultimate analysis of coal is and ash The moisture content of coal, when fired is 3%. The air is moist with the relative humidity (RH) of The barometer shows 735 mm Hg pressure and temperature. The water vapour at saturation is 17.54 mm Hg. The Orsat analysis of products of combustion (POC) is and Calculate the following on the basis of 1 kg of coal.

• Percent excess air
• Volume of air at NTP
• Total volume of POC

SOLUTION:

i)Percent excess air

Let V is volume of POC  at NTP (1 atm and 273K). Performing carbon balance as done in problem 1 gives the volume of POC.  Note that coal contains sulphur. Orsat analysis as explained in lecture 10 reports  both and Therefore carbon balance here is.

The volume of POC is  

Now we can calculate actual amount of air that is used in the combustion process by performing nitrogen balance; Let Z kg mole is the amount of nitrogen derived from air

Substituting the values we get   hence oxygen would be  0.108 kg mole