Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-14KINETICS OF THE CONVERSION OF METHANE−OXYGEN−STEAMMIXTURES IN FILTRATION REACTORAnna А. Karnaukh, Avigeya N. Ivanova, Svetlana S. KostenkoThe Institute of Problems of Chemical Physics RAS, 1. Acad. Semenov prosp.Chernogolovka city, 142432, Moscow reg., RUSSIA, e-mail: karnau@icp.ac.ruWe consider the inclusion of detailed kinetics in a model of the conversion of methaneoxygen-steammixtures to syngas proceeding in the regime of filtration combustion (FC) in aninert porous medium. The study is motivated by the energy-saving effect, which might beachieved due to super adiabatic regime (SA) of FC. A number of previous FC studies showedthat it is primarily kinetics that determines both conditions for materialization of SA andparameters of the combustion wave. A number of questions arose in development of a kineticscheme adequate to formation of stationary FC wave. For example, to what extent theconcepts of gas-phase kinetics can be applied to gas mixture conversion in a very small (sizeof a solid pore) stream reactor? In particular, how to describe, in this case, the surfacekinetics? If the FC wave is not kinetically uniform, that the using standard programs (such asCHEMKIN, GRI-Mech, etc.) may appear most simple in order to descript it? Those programsare supplied usually with extensive databases, which must be reduced anyway. But shouldperform the reduction similar to [1-3], i.e. using the stationary concentrations method?To answer all those questions, we used the approach developed [4] for investigation of theproperties of kinetic models describing primarily ignition, particularly, in methane oxygenmixtures – in absence [5, 6] and presence [7, 8] of water. This approach allows one to selectso-called critical fragments of the reaction scheme and is applicable not only to ignition but toeach significant stage along the FC wave. On other hand, we may take into account that theinitial and following stages mechanisms rule the further processes.This is illustrated by two figures bellow, which present the solution for undistributedkinetic problem for initial stage of conversion of the studied mixture under the atmosphericpressure in a reactor with d=0.6 cm. Compared are two variants of low-temperature linearperoxide model (LTLPM) of ignition. Both models also incorporate primary sources ofhydrogen, including non-linear ones. In the first case, two reactions of СН 3 О 2 radicals withactive intermediates СН 2 О and СН 3 ОН, accelerating the accumulation of branching peroxide,were added to the model, while in the second case – two more quadratic reactions of СН 3 О 2 ,decelerating the process. One can see that both kinetics have two rising stages. During thefirst of ones the oxygen is consumed and heat is accumulated, faster and slower, respectively.52