Basics:

The following diagram shows the input of materials like coal, air and steam in a gasifier and the outputs are producer gas, ashes, tar and soot.

Basis: 1000 Kg coal

a) Amount of producer gas

Carbon balance
C from coal = C in ashes + C in tar + C in soot + C in producer gas

b) To calculate amount of steam decomposed

Decomposition of steam produces H₂.
Moisture of coal directly enters into PG without being decomposed.
Moisture of air and steam decompose to H₂ and is included in CH₄, H₂ and other hydrocarbons.

               
H balance

       H from coal+ H from Moisture of coal + H from steam + H from moist air = H in tar + H in PG
       (producer gas)

c) Water in producer gas = Moisture from coal + undecomposed steam

d) Nitrogen balance for amount of air

Oxygen balance if required to check the results of calculation.

e) Ash balance to know amount of ashes, if not given.