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MINERAL_KINETICS Card

Specifies coefficients for kinetic mineral precipitation-dissolution reactions. The form in which the rate law is implemented:

rate = A*sgn*P*Aff^Ap

where

A = mineral surface area

sgn = sign of Affinity Factor (+1 or -1)

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

Aff = Affinity Factor = abs(1-(Q/K)^1/Tc)

where

K = equilibrium constant

Q = ion activity product

Tc = Temkin constant (currently always set to 1)

Ap = affinity power (currently always set to 1)

Note that prefactor calculations have not yet been verified.

Required Cards:

MINERAL_KINETICS: Opens the block

Optional Cards:

<string>: 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) [J/mol]
AFFINITY_THRESHOLD <float>: If specified, rate is only calculated if Q/K >= threshold and sign < 0
RATE_LIMITER <float>: If specified, Affinity Factor = Affinity Factor/(1+(1-Affinity Factor)/rate_limiter))
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. A = porosity^{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