Coal Calculation

Air Fuel ratio is defined from stochiometry theory after we find Boiler capacity, coal specification and excess air set for perfect combustion.

One of the most important items is that the correct amount oxygen must be supplied per unit weight of fuel burned to provide complete combustion. In addition to the correct “air-fuel” mixture, time must be allowed for complete mixing and burning, and the furnace temperature must be such as to support combustion.



















For example boiler capacity as calculation on http://idpowerstation.blogspot.com/2011/03/boiler-capacity.html got 1738MW.
If HHV use coal type A which has 25.155 x 10^3 J/kg so total coal that needed is 248.72 T/h


Combustion in a furnace is best studied in connection with the ultimate analysis of the fuel used and certain simple chemical reaction.

for coal assumed:
Weight of air require for theoretical perfect combustion.
Weight of gas formed per pound of coal fired with theoretical perfect combustion.
Cubic feet of gas at boiler exit (600F) per pound of fuel fire with theoretically perfect combustion.

Percentage CO2 in exit gas on both dry and wet basis.
Air is mechanically mixture in various gases, but principally of oxygen and nitrogen being 23.3 percent oxygen and 76.8 percent nitrogen by weight.
At 760 mmHg pressure (14.7psia) and 32F, 1 mole of any gas occupies 359 cu ft.



















Picture above describe how much ratio (Fuel : Air) needed if we have coal type A which has its ultimate analysis, so that calculation result 1kg (or 1 lb) need 11.671 kg of air (or 11.671 lb).

Picture below describe how much coal actual burn after inside Pulverize process. That is from total coal calculation 248.72T minus the coal proximity analysis likes moisture and ash content. From the calculation get 168.13 T/h of coal. And from Fuel : Air ratio (1/11.671) get (168.13/....). Total air consumption need get 1962.24 T/h.



















Ash fusion Temperature




















Chemical Composition
These are proposing to find how much slagging and fouling inside boiler. Because of limitation information, we get only coal type A & B which has chemical composition. From the index RS & RF calculation, get coal B has more fouling if we burn into the boiler.

Catogorize Bituminous Coal if Fe2O3 > CaO + MgO











































Next Calculation http://idpowerstation.blogspot.com/2012/01/p-i-control-for-boiler.html

More info see coal Theory.
Gustaf Gafert STEAM POWER STATION McGraw-Hill Book Company New York 1952.