Process description for the S2 example simulation

This example models the complete combustion of Low Volatile Bituminous coal from the coal specifications report produced by the United States Department of Energy’s (DOE) National Energy Technology Laboratory (NETL).

The process includes two sources, one for Fuel and one for ambient Air. The combustor is a Burner model from the Process Library. It uses a configurable set of reactions to represent the complete combustion of the fuel.

A component splitter downstream of the combustor separates the fly ash from the flue gas.

The ultimate analysis combustion uses a single pseudo-component that can react with air to produce a flue gas. We maintain excess oxygen for the combustion by calculating the air flow and specifying the percent oxygen at the FlueGas Sink. You can switch these specifications to fix the air flow if desired. If you decrease the air flow below the stoichiometric ratio (shown in the B1.UA.AirFuelRatio variable), then unburnt fuel exits the Burner. In this case, the component splitter separates any unburnt fuel from the flue gas and sends it to the Ash Sink along with the fly ash.

The Burner produces simple, complete combustion products. It does not generate any intermediate compounds, such as carbon monoxide.

The temperature at the Burner corresponds to the adiabatic flame temperature. That is, this is the temperature achieved by the combustion reaction in the absence of heat transfer by either radiation or convection. The actual flame temperatures are likely less than this ideal value.

A Gibbs minimization reactor (GMR) at the end of the process models the heat transfer that would normally occur in a furnace or boiler. It calculates the final composition of the combustion byproducts. You can observe the effect that the exhaust temperature of the flue gas has on the composition of these products. For example, if you increase the temperature specified at the GMR, you can then see less produced SO3 and more remaining SO2.

The NOx concentrations predicted by this model are not accurate, because the NOx generation is not an equilibrium process and there are other factors that affect its production. You will need a more detailed model if you want an accurate prediction of the NOx contaminants.

A yellow warning badge appears on the GMR model to indicate that it does not support solid components. The component splitter ensures that no solids (ash and unburnt fuel) reach the reactor. The Ash and Fuel components are inerts in the reactor configuration. In this specific case, you can safely ignore this badge.