17
NOTE: If fuel 1, 2, 3 or 4 are selected, it is important to enter all information in the FUEL DATA
MENU before selection. Failure to comply may result in reading inaccuracy. EG: CO
2
, excess air,
loss and combustion efficiency will not calculate correctly.
Fuel Data: The pre-programmed fuels all have corresponding fuel data pre-determined.
NOTE: Displays similar to the above for Wood are also available for Light Fuel Oil, Heavy Fuel Oil,
Natural Gas, Propane and Coal.
Calculation of the maximum CO
2
value: The CO
2
max. value is that proportion of CO
2
in the flue
gas, in percentage terms, that would result from the stochiometric oxidation of the fuel. In general,
for hydrocarbon fuel, the flue gas will consist of the combustion products - water and CO
2
plus the
balance of nitrogen from the combustion air. If it is assumed that efficient combustion takes place,
then any oxygen present in the flue is due to excess air being supplied to the combustion process.
Thus, a linear relationship exists between the amount of oxygen in the flue, and the amount of dilu-
tion of the theoretical maximum value.
NOTE: Where a CO
2
sensor is fitted to the instrument a direct gas measurement is made in place of
the calculated method.
CO
2
= CO
2
max X (20.9 - O
2)
20.9
where CO
2
is the calculated value in %, O
2
is the measured oxygen concentration. Ambient oxygen
concentration is assumed to be 20.9%.
For simple hydrocarbon fuels, CO
2
max. can be calculated:
For a fuel containing 'c' carbon atoms and 'h' hydrogen atoms per molecule, it will take:
c + h oxygen molecules to fully oxidize producing:
c - CO
2
molecules and h/2 water molecules.
For stochiometric conditions, the volume ratio of combustion products to inlet oxygen is thus:
VR =
c + h/2
The maximum CO
2
concentration is therefore:
CO
2
max(%) = c
*
VR*20.9
c + h/2 (VR*20.9) + 79.1
The calculated CO
2
max value is only valid for perfect conditions in the combustion process. It must
be assumed that:
— The fuel is dry. Any water present in the fuel will represent a further dilution factor on the
maximum value.
— The Oxygen measurement from which the CO
2
is calculated is a true wet measurement. i.e.
all the water produced by combustion is present as steam, and hasn't condensed out.
— There is no further dilution of the flue gas, for example from air leaks in the flue.
WOOD
EXIT
HELP
GASES
ABORT
F1
F2
F3
F4
CO2 max:
20.4%
V0 (dry) A0: 0.96%
K1 Factor: 0.74
K2 Factor: 0.000
F Factor
9670
K3 Factor: 65
4
c + h/4
