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Comparison of Two Modeling Methods for a Gas Cleanup System

THERMOFLEX's many components allows for great flexibility when modeling complex systems while providing predictable performance and consistent results. In the following example, we will examine two similar IGCC plants with pre-combustion CO2 capture. The IGCC plants consist of two GE 7FB GT/gasifier trains, two 3-pressure reheat HRSG's, and one single reheat steam turbine arranged as shown in the screenshot below. Each gasifier train includes a Type 1 gasifier (a one-stage, slurry-fed, oxygen-blown unit) with a radiant syngas cooler, an air separation unit, and a gas cleanup system (GCS). CO2 capture is included in the GCS. Ninety percent (90%) of CO2 is removed from the syngas using a dual-stage Selexol process in which H2S is removed in the first stage and CO2 is removed in the second stage. The separated CO2 is then compressed to 2215 psia (153 bar) for delivery. One plant will be modeled using a THERMOFLEX macro component to model the GCS, while the other will utilize several simpler "micro" THERMOFLEX components to build the GCS model.

IGCC Plant - Macro GCS

The single reheat steam turbine used in both of these files has HP conditions of 1815 psia/1050°F (125 bar/566°C), reheat conditions of 420 psia/1050°F (29 bar/566°C), and a condenser pressure of 0.7 psia (48 mbar). With these parameters, the plants have gross outputs of 784 MWe, net outputs of 594 MWe, and net LHV efficiencies of 36%.

GCS Macro Component

GCS Micro Components

The two sample files use identical plant parameters and return identical results but utilize two different methods of modeling the GCS. The identical results given by the two files show that the two approaches are equivalent, thus allowing the user to choose a modeling method based on personal preference.