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MINERAL_KINETICS

Specifies coefficients for kinetic mineral precipitation-dissolution reactions. The rate law is defined through transition state theory, as detailed in section Mineral Precipitation and Dissolution of the theory guide.

\[I_m = -a_m\left(\sum_l k_{ml}(T) {\mathcal P}_{ml}\right) \Big|1-\big(K_m Q_m\big)^{1/\sigma_m}\Big|^{\beta_m} {\rm sign}(1-K_mQ_m),\]

where

\(a_m\) = mineral surface area

\({\mathcal P}\) = prefactor (a sum of prefactor rates; if activation energy is provided the Arrhenius equation is applyied to calculate rates at different temperatures)

\(K_m\) = equilibrium constant

\(Q_m\) = ion activity product

\(\sigma_m\) = Temkin constant (default is 1)

\(\beta_m\) = affinity power (default is 1)

\(k_{ml}\) = rate constant

Note that prefactor calculations have not yet been verified.

Required Cards:

MINERAL_KINETICS
Opens the block.

Optional Cards:

<string>
Gives the mineral name.
RATE_CONSTANT <float>
Kinetic rate constant [mol/m2-sec].
ACTIVATION_ENERGY <float>
If specified, used in the prefactor calculations for temperature specific rates (Arrhenius)
AFFINITY_THRESHOLD <float>
If specified, rate is only calculated if Q/K >= threshold and sign < 0.
RATE_LIMITER <float>
If specified, \(R=-\frac{\Omega}{1+\frac{1-\Omega}{R_{lim}}}\), where \(R_{lim}\) is the rate limiter, \(\Omega=Q/K\), and \(R\) denotes the reaction rate.
IRREVERSIBLE
Flag indicating the reaction is irreversible
SURFACE_AREA_POROSITY_POWER <float>
Exponent in equation for transient mineral surface area calculated as a function of porosity, \(\phi\). A = \(\phi\)SURFACE_AREA_POROSITY_POWER
SURFACE_AREA_VOL_FRAC_POWER <float>
Exponent in equation for transient mineral surface area calculated as a function of change in mineral volume fraction. A = (VF/VF0)SURFACE_AREA_VOL_FRAC_POWER
PREFACTOR
Parameters for reaction rate prefactors

Examples

CHEMISTRY
  ...
  MINERAL_KINETICS
    Calcite
      RATE_CONSTANT 1.d-13 mol/cm^2-sec
    /
  /
  ...
END