Chemical Reaction In Porous Media Research Articles

Prediction of effective diffusivity tensors for bulk diffusion with chemical reactions in porous media

In this paper, the volume averaging transport equations of two reactive processes in porous media are presented. The porous media are characterized by different length scales and the information describing the mass transfer mechanisms is transferred hierarchically between scales by applying the volume averaging method. This development provides the theoretical definition of effective transport coefficients, which can be predicted through solution of the closure problems. The theoretical calculation of effective diffusion tensors of the species in the particle pores is presented. Two closure problems are deduced through mathematical formulation of two different scales: microporous (process 1) and macroporous (process 2). In order to solve these closure problems, the volume finite method is used as the numerical methodology. Good agreement is verified between the numerical solutions obtained in this study and the data found in the literature for the closure problems considered.

Mathematical model of chemical reactions in polydisperse porous media

The recursive mathematical model of the porous media is developed, in which the structure of a porous macroparticle is represented as a system of finer porous particles (microparticles), each of which in turn also consists of a next level system of porous microparticles, etc. The porous structure of microparticles of each level is described by a model of chaotically located spheres. This recursive model is used for developing a mathematical model of chemical reaction in the porous media describing speeds of reagent supply to a reactionary surface as a function of internal structure of a particle, diffusion resistance of microparticles of various levels being accounted. Calculations of a high-temperature pyrolysis process of methane in the porous carbonized samples of wood are carried out. Satisfactory agreement with experimental data is received.

Effect of cooling on the onset of thermosolutal iinstability of a fluid layer heated from below with first-order chemical reaction in porous medium

Effect of cooling on the onset of thermosolutal iinstability of a fluid layer heated from below with first-order chemical reaction in porous medium

SCALAR MIXING AND CHEMICAL REACTION SIMULATIONS USING LATTICE BOLTZMANN METHOD

We simulate scalar mixing and chemical reactions using the lattice Boltzmann method. Simulations of initially non-premixed binary mixtures yield scalar probability distribution functions that are in good agreement with direct numerical simulation (of Navier-Stokes equation) data. One-dimensional chemically-reacting flow simulation of a premixed mixture yields a flame speed that is consistent with experimentally determined value. These results serve to establish the feasibility of the lattice Boltzman method as a viable tool for computing turbulent combustion.

Dispersion and Chemical Reactions in Porous Media

The effect of chemical reactions on the process of admixture transport by a flow through a porous medium is considered. On the basis of a number of examples it is shown that the dispersion coefficient depends on the chemical reaction rate constant.

Numerical scheme for simulating multicomponent mass transport accompanied by reversible chemical reactions in porous media

A numerical scheme is presented for computer simulation of multicomponent gas transport possibly accompanied by reversible chemical reactions in a macroporous medium, based on the dusty gas model. Using analytical solutions for simple systems it is shown that the derivation of the scheme is mathematically correct and the implementation into Borland Dephi code is performed without vital programming errors. Simulations showed remarkable accuracy, robustness and efficiency. A demonstration version of the computer program is available on the internet; http://www.ct.utwente.nl/∼ims/.

The use of the dusty-gas model for the description of mass transport with chemical reaction in porous media

In the present study, mass transport accompanied by chemical reactions in porous media is studied according to the Fick model and the dusty-gas model. For mass transport accompanied by a chemical reaction in catalyst structures showing a plane, line, or point of symmetry, the approximate analytical concept of an effectiveness factor, accounting for intraparticle diffusion, was also evaluated. For a variety of reaction schemes and kinetic rate equations, a comparison was made between the results of the numerical models (Fick and dusty-gas) and the effectiveness-factor concept. From the results it was concluded that pressure in porous catalyst with a plane, line, or point of symmetry did not affect the fluxes seriously, and, therefore, the pressure-driven flow can be omitted from the flux expression without significant loss of accuracy. Furthermore, both for single and multiple reactions, the Fick model is satisfactorily accurate to estimate the transport rate in all cases, and the results deviate only slightly from the dusty-gas model. It should be noted that this latter model requires substantially more computational time. For catalytic membranes, however, transport of inert components as well as large trans-membrane pressure differences may be present, which affect the transport of the reactants and products. The calculations showed that, in contrast to the above-mentioned structures, in this case the dusty-gas model has to be used to describe the transport.

On macroscopic equations governing multiphase flow with diffusion and chemical reactions in porous media

Macroscopic balance equations for components, momentum and energy are established for a multiphase flow with diffusion, chemical reactions, heat transfer and exchanges of components between phases in a porous medium. These equations are established separately for each fluid phase, for the solid part of the medium, and for interfaces, by starting from the corresponding equations valid at the pore level and taking their mean value around each point. Then macroscopic entropy balance equations are derived. The entropy source density shows clearly the generalized fluxes and forces which appear in the problem, and suggests how to choose phenomenological equations. A simple example illustrating the method is given in the last paragraph, for a single phase flow with heat transfer in a porous medium. One obtains a generalized form of Darcy's equation. Rigorous conditions along the interfaces and contact lines in a multiphasic medium are given in Appendix.