1 October 1997
(2) Carbon and hydrogen, when burned to completion with oxygen, unite according to
equations 3.1 and 3.2.
C + O2 = CO2 + 14,100 Btu/lb of C
2H2 + O2 = 2H2O + 61,100 Btu/lb of H2.
2.66 lb of oxygen (or 11.5 lb of air) are required to oxidize one pound of carbon and produce 3.66 lb
of carbon dioxide. Similarly, 8.0 lb of oxygen (or 34.6 lb of air) are required to oxidize one pound of
hydrogen and produce 9.0 lb of water vapor.
b. Stoichiometry. The ratio of the actual amount of oxygen supplied in the oxidation process
to the amount actually required is called the Stoichiometric Ratio (S.R.). In the examples given, the
S.R.= 1.0. The heat released (i.e., 14,100 Btu/lb when carbon is oxidized, or 61,100 Btu/lb when
hydrogen is oxidized) raises the respective products of combustion, plus other gases present, to
(1) The burning of compounds containing oxygen require less air since the compound
already contains some oxygen that will be made available during the combustion process. A typical
waste stream component like cellulose, a major constituent in paper products, is destroyed
according to equation 3.3.
C6H10O5+6O2+(19.97N2) = 6CO2+5H2O+(19.97N2)+10,036 Btu/lb
(2) Because oxygen is present in the "fuel," only 5.1 lb of air per pound of cellulose are
required to completely oxidize the cellulose. The theoretical amount of combustion air will produce
the highest temperature combustion product gas temperature (i.e., an adiabatic gas product
temperature of 3,2500F).
c. Effect of Excess Air.
(1) Since air is the usual source of the oxygen, excess amounts of air will dilute the gases
and reduce the temperature of the gases. When mass burning unprocessed municipal waste,
approximately 7.5 lb of air (S.R.1.0) are required to burn 1 lb of waste. Any processing that
improves the fuel quality (i.e., removal of non-combustibles and high-moisture-content materials)
will increase the heating value of the remaining waste and the specific air demand (i.e., pounds of
air per pound of material actually being burned).
(2) Figure 3-1 shows the relationship between calculated flame temperature, stoichiometric
ratio, and moisture content in the waste.