Abstract:
The modern needs of the chemical industry for small-tonnage processing of methane and other light hydrocarbons have renewed interest in laser thermochemistry. Mathematical modeling is highly relevant for it. In particular, it aims to study chemical processes of radical reactions of hydrocarbons in internal gas flows with catalytic nanoparticles under laser radiation exposure. Numerical models require solving non-stationary systems of equations for the physicochemical dynamics of a multicomponent gas-dust medium. These equations account for radical heterogeneous-homogeneous reactions, radiation absorption and transfer in the medium, the presence of catalytically active nanoparticles, thermal conductivity and diffusion of numerous components of the reaction medium, heat exchange with walls, as well as a number of other nonlinear processes localized in space.
An extended system of Navier-Stokes equations at low Mach numbers, incorporating the aforementioned processes, is presented. This mathematical model features multiple strongly differing temporal and spatial scales. The density variation of the medium depends on changes in volume and internal energy due to chemical reactions and radiation absorption. The computational algorithm is based on a splitting scheme by physical processes. A parallel algorithm was developed using MPI technology. Algorithm testing was performed by comparison with analytical solutions, experimental data on ethane pyrolysis, and computational mathematics tools. A series of calculations for unsteady axisymmetric flows of a two-phase chemically active gas-dust medium were conducted. Computational experiments examined potential technological solutions for non-oxidative conversion of methane into valuable hydrocarbons and hydrogen. The influence of several physical model parameters on product yields was determined. The obtained results are used in designing laboratory-scale reactors for methane conversion using laser catalysis approaches.
|
