The document discusses the stoichiometry of combustion reactions, focusing on both volumetric and gravimetric analysis, particularly in the context of fossil fuels like hydrocarbons. It outlines combustion equations for solid and gaseous fuels while providing examples of how to calculate the theoretical air requirement for complete combustion. Various oxidizers used in combustion processes are also mentioned, along with their implications in chemical reactions.

1. Stoichiometry of combustion
Problems on volumetric and
gravimetric analysis
By
Dr. S. PUGALENDHI, Dr. D. RAMESH, Er. T. AYISHA NAZIBA

2. Combustion reaction
• Stoichiometry of chemical reactions means that balanced
species reactions
• Fossil fuels are mainly compounds of carbon and hydrogen
(hydrocarbons - C m H n).
• The reaction of its oxidation can by written by the equation of
stoichiometry
• C m H n + (m + n/4)O 2 → mCO2 + n/2H2O
• 1 mol + (m + n/4)moles → (m +n/2)moles

3. Oxidizers
• In combustion processes the oxidizer could be:
1. Oxygen (O 2 )
2. Air (21%O 2 + 79%N 2 )
3. Air enriched with oxygen (O 2 > 21%)
4. Some compounds containing oxygen, like nitrogen
oxides: N 2 O

4. Combustion equations of solid fuels
• C + O2  CO2
• 1 mol + 1mol  1mol
• 12 kg + 32kg  44 kg
• 1 kg +8/3 kg 11/3 kg
• 2C + O2  2CO
• 2 mol + 1mol  2mol
• 24 kg + 32kg  56 kg
• 1 kg +4/3 kg 7/3 kg
• 2CO + O2  2CO2
• 2 mol + 1mol  2mol
• 56 kg + 32kg  88 kg
• 1 kg +4/7 kg 11/7 kg
• S + O2  SO2
• 1 mol + 1mol  1mol
• 32kg + 32kg  64kg
• 1 kg +1 kg 2 kg

5. Combustion equations of gaseous fuels
2H2 + O2  2H2O
2 vol + 1 vol  2 vol
4 kg + 32kg  36 kg
1 kg +8 kg 9 kg
CH4 + 2O2  CO2+2H2O
1 vol + 2 vol  1vol+2 vol
16 kg + 64kg 44kg+36kg
1 kg +4 kg 11/4kg+9/4kg
2CO + O2  2CO2
2 vol + 1 vol  2 vol
56 kg + 32kg  88 kg
1 kg +4/7 kg 11/7 kg
C2H4 + 3O2  2CO2+2H2O
1 vol + 3 vol  2vol+2 vol
28 kg + 96kg 88 kg+36kg
1 kg +24/7 kg 22/7kg+9/4kg

6. Theoretical air requirement
= 100/23 [(8/3C + 8H2 + S)-O2 ] kg
= 100/21 [(0.5CO+ 0.5H2 +2CH4 + 3C2H4)-O2 ]m3

7. Volumetric to Mass analysis

8. Mass to Volumetric analysis