GEK Wiki / Stoichiometric Combustion Ratios
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Stoichiometric Combustion Ratios

Page history last edited by jim mason 12 years, 6 months ago



Stoichiometric air-fuel ratios of common fuels

Fuel By mass By volume [1] Percent fuel by mass
Gasoline 14.7 : 1 6.8%
Natural gas 17.2 : 1 9.7  : 1 5.8%
Propane (LP) 15.5 : 1 23.9 : 1 6.45%
Ethanol 9 : 1 11.1%
Methanol 6.4 : 1 15.6%
Hydrogen 34 : 1 2.39 : 1 2.9%
Diesel 14.6 : 1 6.8%
Wood (0%mc) 6.1:1    

source: wikipedia,




Wood stoich ratio

Figure 4 Stoichiometric combustion equation for dry wood.
note: that this is commonly rounded to C H(1.4) O(0.6)

The ultimate analysis of dry wood (that is, the ratio of carbon, hydrogen, oxygen and other elements) varies slightly from one species to another, but for most practical purposes the above equation is adequate. Table 3 shows the air requirements for the complete combustion of wood.



Table 3 Oxygen and air requirements for stoichiometric combustion of wood.



(Note: I am pretty sure that "STP" in the above graphic means 0 degrees C and 101.325kPa; but do be warned that there are quite a few conditions of "standard temperature and pressure" floating around.  Standards sure are great, especially when you have so many to choose from....! ;-)




Yet another take on the stoich number for wood combustion, this from the Encyclopedia of Biomass Thermal Conversion, article R. Desrosiers in "Thermodynamics of gas-char reactions"


molar 02/dry wood = 1.055:1

weight O2/dry wood = 1.476

weight air/dry wood = 6.364





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