Lattice Boltzmann Study Of Multicomponent Flow And Heterogeneous Reactive Transport In Porous Media

The multicomponent flow and heterogeneous reactive transport in porous media arise in a variety of energy, environment engineering, industrial, and engineering processes, such as enhanced oil recovery, geologic sequestration of carbon dioxide, the spreading of pollutants in groundwater reservoirs, bioremediation and processes in the chemical industry. Accord-ing to a large number literature published previously, it is found that, although problems related have been studied penetratingly, owing to the complexities of this problem, for ex-ample, it usually involves multiple scales (microscopic, macroscopic, and field) and multiple processes (advection, diffusion, and chemical reaction), besides that, the pore geometry will be changed due to chemical reactions, then, the physics mechanics behind this problem is not understood clearly. Because of the complexity of such problem, the traditional numerical methods will encounter difficulties such as complexity in dealing with complex boundary, hardness in implementing moving boundary and low performance in parallel computing. In recent years, the lattice Boltzmann method (LBM) originated from kinetic theory, is suitable to study the multicomponent flow and heterogeneous reactive transport in porous media due to its microscopic nature and mesoscopic characteristic.However, studies of the reactive transport in porous media using LBM are still insuffi-ciencies, including the research of the LB models, the boundary conditions and the practical applications. In the present thesis, we aim to develop some new LB models and boundary conditions for convection diffusion equation, and then apply them to study the multicompo-nent flow and heterogeneous reactive transport in porous media.Theory of the LB models:(1) We present an incompressible axisymmetric LB model for convection diffusion equation. Unlike other existing axisymmetric LBMs, the present LB model can eliminate the compressible effects only with the small Mach number limit. Furthermore the source terms of the model are simple and contain no velocity gradients.(2) A general bounce-back scheme is proposed to implement concentration boundary conditions of convection-diffusion equation. Using this scheme, the general concentration boundary conditions, i.e., mixed boundary conditions, can be easily implemented at bound-aries with complex geometry structure like that in porous media.Applications of the models to simulate flow and reactive transport in porous media:(1) Miscible displacements in three-dimensional pipe, homogeneous and heteroge-neous porous media are studied in this thesis. The effects of the Peclet number, viscosity ratio and the geometry structures of porous media on the average concentration, displace-ment efficiency and the fraction of the displaced fluid left behind in the porous media are discussed. The numerical results show that the increase in the Peclet number and viscosi-ty ratio will enhance further growth of the finger, which will increase the remainder of the displaced fluids and the displacement efficiency will be reduced.(2) The bounce-back scheme for concentration boundary conditions proposed above is used to simulate the carbonation of porous CaO with CO2, and the effects of the influencing factors such as Damkohler number, the molar volume ratio between CaCO3and CaO, the radius of CaO grain, on the carbonation conversion rate of CaO are studied. Furthermore, we study the fluid flow, dissolution and precipitation in porous media. The numerical results show that for gas-solid reactions, the particle size of CaO on the reactant conversion rate is the most obvious; while for the dissolution and precipitation, we found that the Damkohler number is the largest impact on the structure of porous media.In summary, the multicomponent flow and heterogeneous reactive transport in porous media are investigated using LBM, and many valuable efforts are made in porous flow. A novel LBM and boundary conditions treatment are proposed to study the convection and diffusion of the axisymmetric flow and the porous flow, respectively. Besides, a large number of numerical simulations are conducted to study the multicomponent flow and heterogeneous reactive transport in porous media, and a series of significant phenomena are obtained, the physics mechanics behind these phenomenon are also analyzed. These works are a necessary basis for future studies.