A. Fontijn et al., GAS-PHASE OXIDATION-KINETICS OF TOXIC METALS AT INCINERATOR TEMPERATURES - THE REACTIONS OF CHROMIUM ATOMS WITH HCL, N2O, CL-2, AND O-2, Combustion science and technology, 101(1-6), 1994, pp. 59-73
The need for kinetic data on individual reactions to develop combustio
n control strategies for alleviation of toxic metal species production
is discussed. In this work such data are obtained at realistic incine
rator temperatures. Measurements on the Cr + HCl reaction, made by bot
h the High-Temperature Fast-Flow Reactor(HTFFR), and Metals High-Tempe
rature Photochemistry (Metals-HTP) techniques, are found to be in good
agreement. The other reactions were studied by the Metals-HTP techniq
ue only. These techniques are briefly described. The N2O and Cl-2 resu
lts are compatible with O and Cl abstraction, respectively, while the
HCl mechanism needs further study. These three reactions are independe
nt of pressure. The previously studied O-2 reaction involves a pressur
e-independent abstraction, and a pressure-dependent addition component
. The following rate coefficient expressions in cm(3) molecule(-1)s(-1
) were obtained: Cr + HCl k(811-1449 K) = 1.6 x 10(-12) (T/K)(0.74) ex
p(- 5802 K/T); Cr + Cl2 k(277-344 K) = 2.1 x 10(-11) (T/K)(0.69) exp(-
396 K/T); Cr + N2O k(278-1150 K) = 2.2 x 10(-12) (T/K)(0.55) exp(-2851
K/T). The data from the latter reaction agree well with measurements
elsewhere at the temperature extremes to yield an overall recommendati
on of k(278-2570 K)= 3.2 x 10(-12) T-0.50 exp(-2605 K/T)cm(3) molecule
(-1)s(-1); this temperature dependence is shown to be in good agreemen
t with that predicted by a recently developed semi-empirical theoretic
al method.