Hybrid gPROMS-CFD Multitubular

High-fidelity modelling of multitubular fixed-bed catalytic reactors

Hybrid Multitubular .

provides unprecedented accuracy in predicting the behaviour of multitubular fixed-bed catalytic reactors
allows any level of complexity in the reactions taking place within the tubes
allows virtually any shell geometry (e.g. baffles, compartments)
combines gPROMS and Fluent^® in a unique tool that leverages the best of each of these two technologies in a seamless, easy-to-use and computationally efficient manner.

PSE's Advanced Model Library for Fixed Bed Catalytic Reactors (AML:FBCR) provides an outstanding degree of predictive accuracy for externally-cooled tubular reactors.

The Hybrid gPROMS-CFD Multitubular modelling software (Hybrid Multitubular) links gPROMS tube models to a CFD model of the shell side to provide enhanced accuracy in modelling multitubular fixed-bed catalytic reactors. This is particularly important where the fluid mechanics and heat transfer on the shell side have a major effect on the operability and safety of the reactor with respect to thermal runaway.

Multitubular reactors are very difficult to model accurately, because of their complex geometry and operation. A typical reactor contains about 20,000 tubes, each with a wall temperature profile that depends strongly on local conditions. The novel formulation of Hybrid Multitubular ensures reasonable solution times for this complex problem without sacrifice of accuracy.

Benefits .

Use high-accuracy multitubular modelling to:

identify and eliminate hotspots
ensure uniform temperature distribution
understand catalyst degradation
enhance selectivity, increase throughput and product quality
optimise economic operation.

High-accuracy modelling brings significant design and operational benefits - for example, in eliminating hotspots and ensuring a more uniform distribution of temperature through the reactor - thus enabling higher overall operating temperatures and greater selectivity, throughput and catalyst life.

How Hybrid Multitubular works

Hybrid Multitubular links a relatively small number of "representative" tubes implemented in gPROMS, to a Fluent^® model of the shell-side fluid dynamics and heat transfer. The model of an individual tube is constructed using the gPROMS Advanced Model Library for Fixed-Bed Catalytic Reactors (AML:FBCR). Any number of tubes can be used (typically 20 to 100), each representing a much larger number of neighbouring tubes within the tube bundle. The Fluent model can contain any internal shell configuration.

Hybrid Multitubular automatically maps corresponding tube-surface points, performs validity checks on supplied data, co-ordinates the execution of gPROMS and Fluent, and manages all the required information flows.

Using the Hybrid gPROMS-CFD Multitubular interface - a simple step-by-step guide

A. Prepare the CFD model of the shell side

Step 1: Create a Fluent model for the shell, representing the tube-bundle as a porous medium. Define boundaries in the geometry and declare the entire zone of the tube bank as a single thread of cells.

B. Prepare the gPROMS model of the tube side

Step 2: Using the gPROMS Advanced Model Library for Fixed Bed Catalytic Reactors (AML:FBCR), configure a single tube model within the gPROMS ModelBuilder. Use ModelBuilder's model validation facilities to determine accurate reaction kinetic parameters and bed-to-wall heat transfer coefficients from laboratory and/or pilot plant data.

C. Execute the combined simulation

Step 3: Specify the number of representative tubes and their x and y co-ordinates within a horizontal cross-section of the CFD model of the shell in a simple text file, together with other relevant information.

Step 4: Execute a Fluent simulation of the shell model. The Hybrid Multizonal automatically acts as a Fluent User Defined Function that computes a heat source and a body force acting on the heat transfer medium in the shell. View the results using Fluent's and gPROMS' results management facilities.

Licensing, supported platforms and pre-requisites

The Hybrid gPROMS-CFD Multitubular interface is available for Fluent Inc.'s Fluent^® CFD software. It is licensed as an option within gPROMS' Advanced Model Library for Fixed Bed Catalytic Reactors (AML:FBCR).

Pre-requisites are:

gPROMS ModelBuilder and AML:FBCR
Fluent^® version 6.1.22 or later

See supported platforms for the latest details on supported platforms.

Available