Back to Input Deck Cards

Back to CHEMISTRY

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. The reaction rate $$I_m$$ for the $$m$$ th mineral is defined as

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

where a positive value corresponds to precipitation and a negative value to dissolution, and 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 number (default is 1)

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

$$k_{ml}$$ = rate constant

Note that prefactor calculations have not yet been verified.

MINERAL_KINETICS
Opens the block.

Optional Cards:¶

<string>
Specifies mineral name.
RATE_CONSTANT <float>
Kinetic rate constant [mol/m2-sec]. If negative, then raised to power 10 (e.g. -12.d0 is converted to $$10^{-12}$$)
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 corresponding to dissolution.
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, $$\phi$$. $$A = A_0 (\phi/\phi_0)$$SURFACE_AREA_POROSITY_POWER
SURFACE_AREA_VOL_FRAC_POWER <float>
Exponent in equation for transient mineral surface area calculated as a function of the mineral volume fraction $$\phi_m$$. $$A_m = A_m^0 (\phi_m/\phi_m^0)$$SURFACE_AREA_VOL_FRAC_POWER. Note that the volume fraction power can be applied only if $$\phi_m^0 > 0$$ corresponding to primary minerals.
PREFACTOR
Parameters for reaction rate prefactors

Examples¶

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