COCO - CAPE-OPEN to CAPE-OPEN simulation environment
 Help

Reactions

Before configuring reactions, make sure the reaction compounds have been added to your reaction package configuration.

To create a reaction, click the Create button on the Reactions page. To remove a reaction, select the reaction and click Delete. You can rename a reaction by selecting the reaction and click Rename.

All compounds that are present in the reaction list will appear in the stoichiometry list. You can make a compound take part in the reaction as product (for the forward reaction) by changing the stoichiometry for that compound to a positive value. Similarly, changing the stoichiometry to a negative number makes that a compound takes part in the (forward) reaction as a reactant. Expressions are accepted. The mass and element balances should match for each reaction.

A reaction can either be kinetic, or equilibrium. Check the Equilibrium Reaction check box to make the selected reaction be an equilibrium reaction. For a kinetic reaction, the nett rate should be specified (forward minus backward rate). For an equilibrium reaction, the equilibrium constant should be specified. The basis of equilibrium constant is in moles. The rate is in mol / m3 / s if the reaction is homogeneous, or in mol / kg catalyst / s if the reaction is heterogeneous. Check the Heterogeneous check box for heterogeneous reactions.

The basis for an equilibrium constant determines which of the physical properties is used. The equilibrium constant should match the calculated

where νi is the stoichiometry coefficient of component i in the reaction, and ai is the property value for compound i in the reaction phase, depending on the basis:

BasisDescription of propertyUnit of measure
ActivityActivity-
FugacityFugacityPa
ConcentrationMass concentrationkg/m3
MassFractionMass fractionkg/kg
MolarityMolar concentrationmol/m3
MoleFractionMole fractionmol/mol

Warning: whereas version 1.0 of the reactions interface specification uses units of kg / h for reaction rates, COCO uses SI units of mol / s!!!

The heat of reaction can be specified as a formula as well. Its unit is J / mol of reaction, and must be at the reference state of the Property Package that is used with the reactor!

Finally a phase identifier needs to be specified for which phase the reaction takes place in.

Reaction rates, equilibrium constants and heats of reaction can be specified in formulas. See formula syntax.

Reaction rate wizard

To quickly put together a formula for reaction rate based upon power law and Langmuir-like inhibition, click the button to the left of the reaction rate edit box. This will open a wizard window. Here, choose the base in which the formula will be set up (activity, mole fraction or concentration). Enable the forward and backward rate if you need those (at least one of the two requires to be enabled). Enter the corresponding rate constants. Expressions are accepted. If you want the rate constants to behave like an Arrhenius acceleration, enable this option and specify the activation energy. Expressions are accepted. If you need a reference temperature, you can type it in the box below the reaction rate specification. Expressions are accepted. The power-exponent for each of the compounds is assumed equal to the absolute value of the stoichiometry; you can however change this in the edit box after closing the wizard. Expressions are accepted.

You can add an inhibition term by making the inhibition constant in the list non-zero for at least one compound. Expressions are accepted. The total inhibition term will be the reciprocal of the product of the specified constants times the reactants specified, increased by one and raised to the specified power.

INDEX
CONTENT