UEi Test Instruments C75OILKIT User Manual
Page 10
The formula for K4 is based on the gross calorific value Qgr. To obtain
the loss based on net calorific value multiply by Qgr/Qnet. Since this
loss is usually small, this conversion has been ignored. This loss is
subtracted from the efficiency.
CO AIR-FREE and Converting to mg/m
3
Certain standards (ANSI Z21.1) for Carbon Monoxide are stated in
terms of air-free. Air-free refers to the concentration of CO in combus-
tion gases undiluted with flue, or other gases containing little CO.
This value is computed using an equation that takes into account the O
2
concentration of the flue gas.
If 5% is measured (O2m) in the flue then the CO gas value will be recal-
culated as if 0% were measured. The equation for air-free is as follows:
COa = CO PPM x [(20.9) / (20.9 - O2m)]
Annual Re-Calibration
While the sensor has an expected life of more than two years in
normal use it is recommended that the analyzer is re-calibrated at
least annually, This is so that long-term drift on the sensor and
electronics can be eliminated. local regulations may require more
frequent re-calibration and users should check with appropriate
authorities to ensure the comply with relevant guidelines.
C50/C75-MAN
P. 7
Efficiency Calculation:
Known Data - Fuel: Qgr = Gross Calorific Value (kJ/kg)
Qnet = Net Calorific Value (kJ/kg)
K1 = Constant based on Gross or net Calorific Va l u e
K1g = (255 x % Carbon in fuel)/Qgr
K1n = (255 x % Carbon in fuel)/Qnet
K2 = % max theoretical CO
2
( d ry basis)
K3 = % Wet loss
H
2
= % Hydrogen
H
2
O = % Wa t e r
Measured Data:
Tf = Flue Temperature
Ti = Inlet Temperature
O
2
m = % Oxygen in flue gas
O
2
r = Oxygen reference %
Calculated Data:
Tnet = Net Temperature
% CO
2
content in flue gas
% Dry flue gas losses
% Wet losses
% Unburned carbon loss
% Efficiency
Tnet
= Flue Temperature - Inlet Temperature
(or ambient)
D ry flue gas loss % = 20.9 x K1 x (Tnet)/K2 x (20.9 - O
2
m)
Wet loss %
= 9 x H
2
+ H
2
O/Qgr x [2488 + 2.1 Tf - 4.2 Ti]
S i m p l i f i e d
= [(9 x H
2
+ H
2
O)/Qgr] x 2425 x [1 + 0.001 Tnet]
Wet loss %
= K3 (1 + 0.001 x Tnet)
Where K3
= [(9 x H
2
+ H
2
O)/Qgr] x 2425
Net efficiency %
= 100 - dry flue gas losses
= 100 - 20.9 x K1n x (Tnet)/K2 x (20.9 - O
2
m)
Gross efficiency %
= 100 - {dry flue gas losses + wet losses}
= 100 - {[20.9 x K1g x (Tnet)/K2 x (20.9 - O2m)]
+ [K3 x (1 + 0.001 x Tnett)]}
Excess Air
= [20.9/(20.9 - O
2
m) - 1] x 100
CO
2
%
= [(20.9 - O
2
m) x K2/20.9]
U n b u r n e d
= K4 x CO/(CO + CO
2
) Note: CO scaled in %
fuel loss %
Where K4
= 70 for coke
= 65 for anthracite
= 63 for Bituminous coal
= 62 for coal tar fuel
= 48 for liquid petroleum fuel
= 32 for natural gas