Computing multi-species chemical equilibrium with an algorithm based on the reaction extents

Abstract

-Maroto, J. M. (2013). Computing multi-species chemical equilibrium with an algorithm based on the reaction extents. Computers and Chemical Engineering, 58, 135-143. https://doi.org/10.1016/j.compchemeng.2013 AbstractA mathematical model for the solution of a set of chemical equilibrium equations in a multi-species and multiphase chemical system is described. The computer-aid solution of model is achieved by means of a Newton-Raphson method enhanced with a line-search scheme, which deals with the non-negative constrains. The residual function, representing the distance to the equilibrium, is defined from the chemical potential (or Gibbs energy) of the chemical system. Local minimums are potentially avoided by the prioritization of the aqueous reactions with respect to the heterogeneous reactions. The formation and release of gas bubbles is taken into account in the model, limiting the concentration of volatile aqueous species to a maximum value, given by the gas solubility constant.The reaction extents are used as state variables for the numerical method. As a result, the accepted solution satisfies the charge and mass balance equations and the model is fully compatible with general reactive transport models.

Electrochemical desalination of bricks – Experimental and modeling

“…The numerical solution is split in a set of equations describing the transport process (without chemical effects) and a set of algebraic equations describing the chemical equilibrium. These coupled modules are solved one after each other in each time increment in the numerical integration efficiently simulating the reactive-transport process [26,27]. Including chemical reactions is essential for a realistic modeling of the process.…”

Comparison of existing chloride ingress models within concretes exposed to seawater

“…Another important phenomena to be taken into account for modeling is the dissolutionprecipitation reactions of the different compounds of the solid matrix (portlandite denoted CH, AFm / AFt phases, etc.). These reactions are introduced in the predicting models based on geochemical approaches [8,21,23,32]. As these models are not easy-to-use from an engineer point of view (many input data, difficult numerical implementation, etc.…”

Modeling of Electric Double-Layers Including Chemical Reaction Effects

“…In any time step of the numerical integration of the NPP system, the chemical equilibrium model reestablishes the chemical equilibrium condition in the electrolyte. For a more detailed description of the mathematical and numerical model for the multi-species chemical equilibrium, the reader is referred to [25].…”

“…Therefore, the term G i is not included in the transport equations. Instead, a set of nonlinear algebraic equations, given by the mass balances (stoichiometric reactions) and the action mass (equilibrium reaction) equations, is used to describe the multi-species chemical equilibrium system [23][24][25].…”