A Chemical Kinetics Computer Program for Homogeneous and Free-Radical Systems of Reactions

Abstract

A computer program was developed to compute the product distribution in any homogeneous reaction mechanism. The program includes a numerical method to apply the steady-state assumption when a mechanism involves intermediates present in low concentrations. Under this condition standard computation methods fail, but the steadystate' assumption is valid. During an induction period the program compares direct integration with the steady-state method, and when they agree it switches to the steadystate method. The program includes a regression procedure to fit rate constants to experimental product distributions. Sample calculations were done for the hydrogen-bromine reaction and for ethane pyrolysis. The results agreed with data from the literature.

Analysis of Kinetic Reaction Mechanisms

“…The history of the application of the QSSA can be divided into three periods (Turányi et al 1993b). By applying the QSSA, the stiff systems of ODEs could be converted to non-stiff ones (Snow 1966;Blouza et al 2000), and numerical solutions to these ODEs could be obtained using traditional ODE solvers. Due to the limited availability of computer power during this time, the kinetic ODEs had to be solved analytically and using the QSSA helped to convert the systems into an analytically solvable form.…”

Multivariable optimization of thermal cracking severity

“…It is important to note that a stationary profile of the so-called QSSA species along the reactor coil is not necessary for application of this simplification. Extensive arguments on the applicability range of QSSA may be found in Snow (1966), Côme (1977), Turányi et al (1993), Tomlin et al (1995), and Aribike et al (2006).…”

Derivation of a quantitative minimal model from a detailed elementary-step mechanism supported by mathematical coupling analysis

“…In particular, for spatially nonhomogeneous systems, numerical treatment of the underlying large scale and mostly stiff partial differential equations is still a challenge. Therefore, many automatic numerical methods have been developed for the purpose of model reduction in chemical kinetics, among them the classical quasi-steady-state and partial-equilibrium approximations, [9][10][11][12][13] lumping techniques, 14,15 and sensitivity analysis. 6,7 The aim is to construct a reduced model which can be treated much easier numerically and if small enough may allow even an analytic investigation of phase-space topology, bifurcation behavior, attractor geometry, and generally, in-corporation into numerically expensive simulation of spatially extended reaction-diffusion systems.…”