Linear and nonlinear analyses of the effect of chemical reaction on the onset of buoyancy‐driven instability in a CO₂ absorption process in a porous medium or Hele‐Shaw cell

Abstract

To understand CO2 absorption into a basic solution saturated porous medium or a Hele‐Shaw cell, the effect of the chemical reaction between dissolved CO2 and the basic reactant in the solution on the onset of a buoyancy‐driven instability in a gas absorption process is analyzed theoretically. For the infinitely fast reaction, new linear and non‐linear stability equations are derived without the quasi‐steady state assumption (QSSA) and solved analytically. The present stability analysis without the QSSA shows that the important parameters are the dimensionless densification numbers and the reactant concentration ratio. For the physically unstable system, the chemical reaction can induce a non‐monotonic density profile and has an important effect on the onset of instability motion. The effect of the reactant concentration ratio on the stability of the system is strongly dependent on the physical situation. Here, we call the system which is physically stable when there is no chemical reaction as the physically stable system. Even for this physically stable system, the chemical reaction makes the system unstable and induces the gravitational fingering instability motion. Also, it is found that the stability of the physically stable system is relatively insensitive to the non‐monotonicity of the density profile.

Pore-scale study of dissolution-driven density instability with reaction A+B→C in porous media

“…In addition, the chemical influence intimately depends on the reactants, and existing experiments may not have covered all the scenarios. Therefore, theoretical investigations were performed to analyze dissolution-driven DI with reaction A + B → C. For example, Kim et al [12,13] studied the development of DI with chemical reaction in a porous medium using the linear stability theory. They pointed out that reaction can enhance, delay, or even introduce the fingering development.…”

“…For these reasons, numerical simulations have been conducted under the guidance of existing theoretical predictions. For instance, Kim et al [12,13] numerically classified the chemical effects on dissolution-driven DI, employing their linear analysis results as initial conditions. Budroni et al [5] numerically modeled both the stabilized and destabilized fingering phenomena and tested the effects of initial reactant concentrations.…”

Enhanced steady-state dissolution flux in reactive convective dissolution

“…When the dissolving species A reacts with a solute B initially present in the host solution following a second-order scheme A+B → C, the reaction can slow down or accelerate the development of convection compared to the nonreactive case depending on the type of density profile building up in the host phase, as shown by both experimental and numerical approaches 2,3,[13][14][15][16][17][18] . If C is less dense than B, a density profile with a minimum is observed and the 0 * Corresponding author; E-mail: adewit@ulb.ac.be 0a Université libre de Bruxelles (ULB), Faculté des Sciences, Nonlinear Physical Chemistry Unit, CP231, 1050 Brussels, Belgium.…”

Differential diffusion effects on density-driven instability of reactive flows in porous media

“…Captured experimental data have showed that different reactions can either inhibit or accelerate the development of DI with respect to the chemicals containing in the host fluid. Considering that the whole extent of DI may not be captured in the above experiments [10,12], theoretical studies were performed simultaneously to analyze DI with reaction A + B → C [13][14][15][16]. Loodts et al [16] theoretically provided a classification of four types of density profiles, with each one potentially representing a kind of DI dynamics.…”