Reaction submodels for the CC28 example simulation

This simulation uses the following reaction submodels from the simulation-specific model library:

• SMR — Provides all necessary reaction kinetics for the steam methane reforming (SMR) reaction. We use this reaction submodel in the SMR plug flow reactor.

• HTS — Provides the reaction kinetics for the high-temperature water-gas shift (HTS) reaction. We use this reaction submodel in the HTS plug flow reactor.

• LTS — Provides the reaction kinetics for the low-temperature water-gas shift (LTS) reaction. We use this reaction submodel in the LTS plug flow reactor.

• Burner — Provides the reaction kinetics for the combustion reaction in the furnace. We use this reaction submodel in the B1 burner.

The following sections provide details on the reactions and associated reaction kinetics.

Steam Methane Reforming (SMR)

We use the kinetic rate expressions from Xu and Froment[1] for the SMR reaction. While there are many proposed mechanisms, we chose these rate expressions because they are the most generally accepted kinetic models in industry[2]. The overall rate expressions include kinetic reaction rate constants, equilibrium constants, and adsorption constants for each component. The SMR reaction submodel includes three reactions:

The corresponding reaction rate equations are:

where

ki is the reaction rate coefficient for each reaction

Ki is the equilibrium constant for each reaction

Kj is the adsorption constant for component j, in bar-1

pj is the partial of component j, in bar

ri is the reaction rate, in kmol/kgcat-h

Xu and Froment[1] give the pre-exponential factors, activation energies, and enthalpy changes for the final model. We use the equilibrium constants published by Hou and Hughes[3].

High-Temperature Water-Gas Shift (HTS)

We use the kinetic rate expressions in Hla et al.[4] for the HTS reaction. Hla et al. describes the kinetics for the HTS reaction over two commercial Fe2O3/Cr2O3/CuO catalysts. We selected Catalyst 2 (HTC2) for this simulation. The HTS reaction submodel includes the following reaction:

The corresponding reaction rate expression is:

where

T is the temperature, in K

R is the universal gas constant, in kJ/kmol-K

b is the reversibility factor

Keq is the equilibrium constant

pj is the partial of component j, in kPa

ri is the reaction rate, in kmol/kgcat-s

We use the generally accepted empirical model[5] for the equilibrium constant (Keq):

Low-Temperature Water-Gas Shift (LTS)

We use the kinetic rate expressions in Moe[5] for the LTS reaction. Moe describes the kinetics for the LTS reaction over a Cu/ZnO/Al2O3 catalyst. The LTS reaction submodel includes the following reaction:

The corresponding reaction rate equation is:

where

T is the temperature, in K

b is the reversibility factor

Keq is the equilibrium constant

pj is the partial of component j, in bar

ri is the reaction rate, in kmol/kgcat-min

We use the generally accepted empirical model[5] for the equilibrium constant (Keq):

Burner

We use a set of conversion reactions to model the combustion of natural gas with no side reactions.