Heterogeneous reaction properties

Property package for the reaction of CH4 with an iron-based OC. More details of this reaction scheme can be found in reference [1]. The gas components modeled are CH4, CO2, H2O. The solid components modeled are Fe2O3, Fe3O4, Al2O3. Reaction scheme modeled is CH4 + 12Fe2O3 => 8Fe3O4 + CO2 + 2H2O

Rate basis: Molar

Units: SI units

Lists:

  • Component list - [CH4, CO2, H2O, Fe2O3, Fe3O4, Al2O3]

  • Reaction list - [R1]

Parameters:

Parameter Name

Symbol

Description

Units

Reference

dh_rxn

\(H_{rxn}\)

Heat of reaction

kJ/mol

grain_radius

\(r_{g}\)

Representative particle grain radius within oxygen carrier particle

m

[1]

dens_mol_sol

\(\rho_{sol,mol}\)

Molar density of oxygen carrier particle

mol/m3

[1]

a_vol

\(a_{vol}\)

Available reaction volume per volume of oxygen carrier

None

[1]

k0_rxn

\(k_{0}\)

Pre-exponential factor

\(\frac{mol^{1-n_{i}} m^{3n_{i}-2}}{s}\)

[1]

energy_activation

\(E_{A}\)

‘Activation energy

kJ/mol

[1]

rxn_order

\(n_{i}\)

Reaction order indexed by reaction list

None

[1]

gas_const

\(R\)

Gas constant

kJ/mol.K

rate_reaction_stoichiometry

\(b_{i,j}\)

Reaction Stoichiometry indexed by reaction list and component list

kJ/mol.K

[1]

mw_comp

\(mw_{j}\)

Molecular weights of components indexed by component list

kg/mol

[1]

Variables:

Variable Name

Symbol

Description

Units

k_rxn

\(k\)

Rate constant

\(\frac{mol^{1-n_{i}} m^{3n_{i}-2}}{s}\)

OC_conv

\(X\)

Fraction of oxygen carrier converted

None

reaction_rate

\(rate_{rxn}\)

Reaction rate

mol_rxn/m3.s

temperature

\(T\)

Temperature

K

dens_mol_comp

\(C_{g,j}\)

Component molar concentration indexed by component list

mol/m3

mass_frac_comp

\(x_{j}\)

Component mass fractions indexed by component list

None

particle_porosity

\(\phi\)

Porosity of oxygen carrier

None

dens_mass_skeletal

\(\rho_{skeletal}\)

Skeletal density of oxygen carrier

kg/m3

Methods:

Rate constant:

\[k = k_{0}exp{\left( \frac{-E}{R T} \right)}\]

Reaction rate:

\[rate_{rxn} = x_{Fe2O3}{\left( 1 - \phi \right)}\rho_{skeletal} \frac{a_{vol}}{mw_{Fe2O3}} \frac{{3} {k} b_{i,Fe2O3} {C_{g, CH4}}^{n_{i}}}{\rho_{sol,mol} r_{g}} {\left(1 - X\right)}^{\frac{2}{3}}\]

References:

    1. Abad, J. Adánez, F. García-Labiano, L.F. de Diego, P. Gayán, J. Celaya, Mapping of the range of operational conditions for Cu-, Fe-, and Ni-based oxygen carriers in chemical-looping combustion, Chem. Eng. Sci. 62 (2007) 533–549.