Abstract
Emissions of NO, N2O, SO2 and CO in the flue gas from 71 MW PFBC demonstration plant were measured during stationary combustion tests conducted from January to December in 1997. An index of emission gas partial pressure, {PNO/PSO2· (PCO/PNo) 2} named as ASHTR-SN, was introduced and plotted against the reverse of the average cyclone temperature (Tc). A linear correlation of Van' t Hoff law was found with high correlation factor of 90.17 % as follows:
ASHTR-SN index=N2O/SO2× (CO/NO) 2= exp (47.3×103/Tc-50.4)
Also those emissions were measured every five minutes for eight days during a combus-tion test conducted from November 19 to 26 in 1997. The same index of ASHTR-SN at the transient condition were plotted and found an identical correlation against the reverse of Tc, with high correlation factor of 98.5 % as follows:
ASHTR-SN index=N2O/SO2× (CO/NO) 2=exp (47.7×103/Tc-49.5)
This correlation indicated that emission gases were mutually influenced by the concentrations of other gases and correlated to the reaction temperature. Since CO is a reductant of CaSO4 to liberate SO2 (CaSO4+CO⇔CaCO3+SO2) and also CO is a product from the NO/NCO reaction (NO+NCO⇔N2O+CO), a temporary reaction formula is introduced as follows to express interaction among emission gases:
CaSO4+N2O+2CO⇔CaCO3+2NO+SO2+Volatile-C
Since ASHTR-SN index (=N2O/SO2× (CO/NO) 2) is an equilibrium constant for the above reaction formula, concentrations of emission gases may follow Le Chatorie principle and will be estimated at high accuracy under stationary as well as transient conditions.
A key role of CO is also discussed where (SO2/CO) and (N2O·CO/ (NO) 2) are individual-ly correlated to Tc.
