Air Heater Performance
Air Heater Performance
Air Heater Performance
PMI Revision 00
Therefore..
PMI Revision 00
Data required
O2 & CO2 in FG at APH Inlet O2 & CO2 in FG at APH Outlet Temperature of air entering air heater Temperature of air leaving air heater Diff. Prsr. Across APH on air & gas side
PMI Revision 00
PMI Revision 00 Sampling Point for Flue Gas Temperature & Composition
Thermocouples
Traverse Ports
Ports
PMI Revision 00
Datascan Boxes
PMI Revision 00
11 1 11 1 Temp C 11 1 11 1 11 1 A B C Probes D E
PMI Revision 00
S1 S1 S1
11 1
%
1 1
S1 S1 S1
May 24, 2012
11 11 11 11 10
1 A B C D
PMI Revision 00
Probe
Average Oxygen values in Test x from the fourteen 11 I . probe grid in Flue Gas D uct at Air H eater Inlet
11 . J
D 11 . C B A
May 24, 2012
11 .
E 11 .
F 11 .
11 .
G 11 . 11 . H
11 . 11 . 11 . 11 . 11 PMI Revision 00 11 . . 11 .
Average Oxygen values in Test xx from the fourteen 11 I . probe grid in Flue Gas D uct at Air H eater Inlet
11 . J
11
Air Leakage
Weight of air passing from air side to gas side. This leakage is assumed to occur entirely between air inlet and gas outlet. Almost 65% leakage is from radial seals, 30 % from circumference bypass seals and rest from axial, rotor post seals Hot End / Cold End / Entrained Leakage Empirical relationship using the change in concentration of O2 or CO2 in the flue gas = CO2in - CO2out * 0.9 * 100 CO2out O2out - O2in * 0.9 * 100 (21- O2out)
Calculation
% AL
Calculation using CO2 values is preferred because of higher absolute values and lower errors. The method of determination of O2 or CO2 should be the same at inlet and outlet - wet or dry (Orsat).
May 24, 2012 PMI Revision 00 12
PMI Revision 00
14
X Ratio
Ratio of heat capacity of air passing through the air heater to the heat capacity of flue gas passing through the air heater. = = Wair out * Cpa Wgas in * Cpg Tgas in - Tgas out (no leakage) Tair out - Tair in
PMI Revision 00
15
4) Air In / Air Out Temperatures For air inlet and outlet temperatures, weighted averages of primary and secondary air temperatures are used as below. Fraction of PA flow = F1 = PA flow / Total Air Flow Fraction of SA flow = F2 = SA flow / Total Air Flow Weighted Air Temp In = F1 * PA Temp In + F2 * SA Temp In Wghted Air Temp Out = F1 * PA Temp Out + F2 * SA Temp out
PMI Revision 00
16
5) The specific heat of the air is calculated at the average air temperature in the AH (Inlet Temperature + Outlet Temperature) / 2. This is done by using ASMEs PTC 4.1 Steam Generating Units, Figure 3. = CpAIR (kcal/kg/K) Formula: Cp_air = 9.798958E-19 * X5 2.76786E15 * X4 7.42842E-12 * X3 +0.00000002654212 * X2 +.000006479326 * X +0.2389161 Where X = Average air temperature in AH. 6) If a CO2 analyser is not available, the amount of CO2 in the flue gas can be calculated by subtracting the O2 percentage from the constant for (O2 + CO2). CO2 (%) = (O2 + CO2) - O2 = BO2CO2 - O2
May 24, 2012 PMI Revision 00 17
7) The specific heat of the flue gas is calculated using average gas temperature (Gas inlet and no-leakage gas outlet), carbon content of fuel, hydrogen content of fuel, and amount of CO2 in the flue gas. See ASMEs PTC 4.1 Steam Generating Units, Figure 7. = CpGAS (kcal/kg/K) 8) Air Heater Leakage (%) is defined as 100*the mass of wet air leaking to the gas side divided by the mass of wet gas entering the air heater. However, it is usually approximated by one of the two equations using measurements of gas analysis, by volume, on the gas side: % Leakage = 90* (%CO2 entering - %CO2 leaving) / %CO2 leaving % Leakage = 90* (%O2 leaving - %O2 entering) / (21%O2 leaving)PMI Revision 00 May 24, 2012
18
9)
AH Gas Side Efficiency is calculated as below. AHE = 100 * (Gas Temp In NL Gas Temp Out) / (Gas Temp In Air Temp In) Or AHE = 100 * (AHGIT - EGTCorTNL) / (AHGIT AirT)
PMI Revision 00
19
THANK YOU
PMI Revision 00
20