heterogeneous reactions

[Abderraouf A]

I am working on biomass pyrolysis at the Euler-Euler scale. I am performing heterogeneous reactions and would like to validate them with Cantera. I am wondering if it is possible to carry out a reaction between solid and gas without going through surface reactions. Can this be done using an Arrhenius law (avoiding surface reactions)?

[Ray Speth]

Hi,

You can define heterogeneous reactions without needing to have specific surface species, but conceptually, such a reaction is still taking place at a surface, and the rate of reaction should be proportional to the area of that surface. For the purpose of modeling in Cantera, it is still necessary to define the surface, although some properties can simply be filled with dummy values that will not influence any rate calculations. Here's a simple example of a YAML input file to set up such a surface:

phases:

- name: surf

thermo: ideal-surface

adjacent-phases:

- gri30.yaml/phases: [gri30]

- graphite.yaml/phases: [graphite]

species: [C(S)]

kinetics: surface

reactions: all

state:

T: 900.0

coverages: {C(S): 1.0}

site-density: 4.7063e-09

species:

- name: C(S)

composition: {C: 1}

thermo:

model: constant-cp

reactions:

- equation: C(gr) + O2 => CO2

rate-constant: {A: 4e5, b: 0.5, Ea: 2000 K}

The characteristics of the placeholder species C(S) do not matter, and the site-density does not end up affecting the rate of progress for the reaction. The only property of the surface that is used is its temperature (which should presumably be equal to that of the adjacent gas and bulk, assuming continuity).

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Regards,

Ray