GAS-PHASE OXIDATION-KINETICS OF TOXIC METALS AT INCINERATOR TEMPERATURES - THE REACTIONS OF CHROMIUM ATOMS WITH HCL, N2O, CL-2, AND O-2

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.