The flowsheet of a post-combustion CO2 capture (PCC) process has been developed in gPROMS Model Builder. PCC technology involves CO2 absorption/stripping with aqueous solvents such as monoethanolamine (MEA). The authors present a model simplification strategy for a detailed rate-based model of post-combustion CO2 capture with MEA solvent in order to significantly reduce the CPU time needed for the simulations.
Thermodynamic calculations involving vapour–liquid equilibrium and chemical equilibrium, as well as the physical properties of the system, are determined using the ElecNRTL model in Aspen Properties The thermodynamic model is linked with gPROMS through the CAPE-OPEN thermodynamic socket of gPROMS since Aspen Properties exports a thermodynamic model for a given mixture as a CAPE-OPEN Property Package.
While retaining use of the Aspen Properties CAPE-OPEN Property Package, the simplification method targets the non-linear algebraic equations used for determining the mass transfer coefficients since these equations involve numerous external property calls (i.e. through CAPE-OPEN interfaces). By removing the need for most property calls, a significant reduction in the CPU time required by each simulation is achieved (50%) while the results obtained with the simplified model still compare well with the ones obtained with the full model.
Repetitive calls to a CAPE-OPEN Property Package, especially property per property, may indeed consume a lot of CPU, more importantly when the thermodynamic model is complex like ElecNRT is. Being able to request the property calculations only when really needed leads quickly to a large reduction in the CPU time needed for each simulation.
CO-LaN does not interpret the need to reduce CPU as an hint that CAPE-OPEN makes simulation slow. As documented almost immediately after the end of the Global CAPE-OPEN project by the Interoperability Special Interest Group, slowness through CAPE-OPEN interfaces is first an implementation issue. Still CO-LaN is looking to improve structurally speed over CAPE-OPEN induced communications with the CAPE-OPEN Binary Interop Architecture (COBIA) which is under development.