Particle Reactions Reference

Components from the continuous gas or liquid phase can be used as both reactants and as products in the particle reactions within the Lagrangian phase. Therefore, these components need to be defined in the multi-component gas or liquid phase mixture in the continuous phase.

Particle Reactions

The Particle Reactions node has no properties, however, the context menu has the following options:

New Particle Reaction: Creates a particle reaction. This new object contains sub-nodes for reactants, products, and the reaction rate.

Reactants / Products

The Reactants and Products sub-nodes both have a context menu with the following options:

Add Solid Reactant
Add Fluid Reactant
Add Solid Product
Add Fluid Product: Selecting one of these options opens a submenu of all materials of the same phase in the material database. When you select a material, a [Reaction Component] sub-node is created for that material. You can add as many reactant or product components as required.

[Reaction Component]

Each [Reaction Component] node has the following Properties:

Stoich. Coeff.: Allows you to set the stoichiometric coefficient for that reaction component in the reaction definition.

Reaction Rate

The Reaction Rate node, which controls the rate of the particle devolatilization or particle combustion reaction, has the following Properties:

Method

Diffusion Limited User Reaction Rate: Activates the Diffusion Limited User Reaction Rate node.
First-Order Combined Rate: When using the Particle Reaction model, activates the First Order Combined Rate node.
Half-Order Combined Rate: When using the Particle Reaction model, activates the Half-Order Combined Rate node.
First-Order Rate: When using the Particle Devolitilization model, activates the First-Order Rate node.
User Reaction Rate: Activates the User Reaction Rate node.
If you have specified multiple solids and/or multiple gas/liquids as reactants, this is the only method that is available.

[Reaction Rate Method] Properties

The First-Order Combined Rate, Half-Order Combined Rate, and First-Order Rate sub-nodes have the following Properties:

Temperature Exponent, Beta: Sets the temperature exponent $β$ for this reaction. See Eqn. (3756), Eqn. (3760), and Eqn. (3365).
Activation Energy, Ea: Sets the temperature exponent $E_{a}$ for this reaction. See Eqn. (3756), Eqn. (3760), and Eqn. (3365).

First-Order Combined Rate

The first-order combined rate, available for the Particle Reaction model, calculates the effective particle reaction rate by accounting for both chemical kinetics at the particle surface and diffusion of gas-phase reactant species. The term first-order means that the kinetics reaction rate is first-order with respect to gas-phase reactant species concentration. The First-Order Combined Rate node uses its properties to control part of this calculation method, while its sub-nodes Pre-exponent and Diffusion Coefficient provide inputs as scalar profiles. See Eqn. (3760) and Eqn. (3761).

Half-Order Combined Rate

The half-order combined rate, available for the Particle Reaction model, calculates the effective particle reaction rate by accounting for both chemical kinetics at the particle surface and diffusion of gas-phase reactant species. The term half-order means that the kinetics reaction rate is half-order with respect to gas-phase reactant species concentration. The Half-Order Combined Rate node uses its properties to control part of this calculation method, while its sub-nodes Pre-exponent and Diffusion Coefficient provide inputs as scalar profiles. See Eqn. (3365) and Eqn. (3763).

First-Order Rate

The first-order rate, available for the Particle Devolatilization model, calculates the particle reaction rate where the chemical kinetics is first-order with respect to solid-particle reactant concentration. The First-Order Rate node uses its properties to control part of this calculation method, while its sub-node Pre-exponent provides inputs as a scalar profile. See Eqn. (3756) and Eqn. (3757).

User Reaction Rate

Use this method when you have multiple solids and/or multiple gas/liquids as reactants.

The user-reaction rate, available for both Particle Reaction and Particle Devolatilization models, allows you to specify custom reaction rates. The User Reaction Rate node functions as a scalar profile (see Eqn. (3758)).

Pre-exponent

The Pre-exponent node, which is a sub-node of reaction rate nodes other than the User Reaction Rate node, functions as a scalar profile. It lets you use the Arrhenius form. See Eqn. (3756), Eqn. (3760), and Eqn. (3365).

Diffusion Coefficient

The Diffusion Coefficient node is included in the First-Order Combined Rate and Half-Order Combined Rate nodes (Particle Reaction only). It is needed because this reaction includes a gas oxidizer, and you have to know the rate at which it diffuses. It represents $D_{m}$ in Eqn. (3762), and functions as a scalar profile.