(444b) Deployment of a gPROMS-Based Three-Phase Reactor Unit Operation within PRO/II Flowsheets through CAPE-OPEN Interfaces

This paper describes the work done to deploy a three-phase slurry bubble column reactor model for Fischer-Tropsch synthesis within PRO/II flowsheets through the development of a CAPE-OPEN compliant unit operation using the gPROMS advanced process modeling platform.

TOTAL, S.A. (?TOTAL?) has developed a steady-state model of a slurry reactor used for gas-to-liquids synthesis in collaboration with the group of Professor Faiçal Larachi of Laval University in Canada(1). This model had been originally developed in Aspen Technology's ACM® equation-oriented environment using internally coded thermodynamic calculations based on a variety of models and correlations.

TOTAL wished to deploy the model within a flowsheet of the full gas-to-liquids process implemented in Invensys Process Systems' PRO/II® software, and approached Process Systems Enterprise (?PSE?) to study the feasibility of converting the model to a CAPE-OPEN compliant unit operation developed in PSE's gPROMS® advanced process modeling platform.

PSE developed a CAPE-OPEN compliant unit operation through the following tasks:

1. Translation of the original ACM model into gPROMS

2. Full coupling of hydrodynamics with mass and energy balances, allowing the full reactor model to be solved simultaneously

3. Reformulation of several equations to (i) ensure consistency of species holdups with gas-phase and liquid-phase concentrations calculated from the equations of state, and (ii) improve model robustness

4. Implementation of a robust initialization procedure that allows the model to be initialized without a set of initial guesses.

5. Addition of calls to the Process Modelling Environment (PME) physical property package for the calculation of thermodynamic and transport properties.

6. Export of the gPROMS model as a CAPE-OPEN compliant unit operation

7. Testing of interoperability with PRO/II flowsheets, including flowsheets with recycle loops that include the reactor unit operation.

In the course of interoperability testing, PSE identified issues that needed to be addressed in the gPROMS and PRO/II software. The issues have now been addressed, and the interoperability of the gPROMS-based unit operation within the PRO/II PME has been demonstrated.

On the gPROMS side, the following enhancements to the CAPE-OPEN interface were implemented:

1. Added the ability to explicitly control whether the gPROMS components use mass or mole basis for all calls to the PME physical property package.

2. Added the ability to map gPROMS selectors to CAPE-OPEN option parameters

3. Made usability enhancements to gPROMS ?Export to CAPE-OPEN procedure?

4. Substantially enhanced the logging capabilities of the gPROMS components, which facilitates the tracing of the root causes of interoperability issues.

On the PRO/II side, the following enhancements to the CAPE-OPEN interface were implemented:

1. Reviewed and revamped the CAPE-OPEN integration architecture to provide better lifetime management of CAPE-OPEN objects and eliminate memory leaks and errors.

2. Improved interoperability by allowing seamless use of mass/mole basis and fixing thermodynamic property calculation and access issues.

3. Added logging capability to facilitate diagnosis and troubleshooting.

In the resulting implementation, the user has the option to execute a robust initialization procedure the first time that the reactor model is used. To increase computational efficiency, the robust initialization procedure is not executed in subsequent iterations through the reactor unit operation. Detailed model results can be consulted through the gPROMS graphical reporting interface gRMS, which is launched automatically when the reactor unit operation is first solved.

A strong dialog between the end user (Total) for defining his needs and the software companies (Invensys and PSE) to identify and correct the problems has been the reason of the success of this project and is required for any CAPE-OPEN integration.

(1) Iliuta I., F. Larachi, J. Anfray, N. Dromard, and D. Schweich, ?Multicomponent multicompartment model for Fischer-Tropsch SCBR,? AIChE Journal, Vol. 53, No. 8, 2062-2083, 2007