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.