Skip to main content

Simulation and control of fast transients in process and utility systems

Objective

To develop dynamic models which simulate fast transients in process and utility plants, including controls. The models are integrated into a flow sheeting package of a form compatible with simulation packages such as SPEEDUP and CHEDYN. These are evaluated on case studies from the process industry.
The present work deals with the development of a computer simulation tool for a class of process and utility plants undergoing fast transients including controls. The primary intent is to develop a prototype dynamic for compressors, turbines, valves, piping, etc.

The present test case study is that of a motor driven compressor system. Its function is to furnish a framework for establishing a controller design methodology, and prepare for a subsequent study on a real test case: a cogeneration plant.

A dynamic simulator code has been developed for fluid transformations involving compression, expansion, heat generation and heat transfer. Controller design procedures were embedded in the computer code. This allowed easy transfer of information between simulation, used to sample the process response to various perturbations, and optimization of controller design and tuning.

Equations were developed for equipment models, based on 1-dimensional flow approximation. The architecture of a simulation package based on the object paradigm is described. The program has been validated on test cases. In particular, compression systems have been evaluated for different strategies. Simulation of an existing gas turbine and control of a cogeneration plant are under way.

A model was presented which allowed dynamic simulation of processes involving compression, expansion, heat generation and mass transfer in fluids. Equations were developed for various equipment models, based on 1-dimensional flow approximation. Proposed solution methods for differential algebraic equation (DAE) systems were compared on the basis of accuracy and computer usage.

The architecture of a simulation package bsaed on the object paradigm is described. This program has been validated with experimental data; surge onset in compression systems was predicted satisfactorily.
An integrated dynamic model is developed, for use on process and utility plants where the interaction of fast acting and slow acting transients are important. The following tasks are carried out:

1) Extension of typical and existing models of fluid dynamic processes and process plant elements.

2) Simulation of process and utility networks incorporating many components (compressors, valves, pipeline network).

3) Control algorithms and schematics of system operation.

Developments in each of these areas are carried out, initially as expansions to existing modules, then integrated together to form a pre-competitive software package for dynamic simulation of general process systems. The interface between the modules is defined by input and output of boundary conditions to process subsystems. This modular approach, relying on specification of input and output conditions for each module provides a form which is compatible with or easily adaptable to process dynamic simulation packages such as the Imperial College SPEEDUP or the University of Liege CHEDYN.

The applicability of the methods is evaluated by carrying out two case studies in the utilities industry. The test cases undertaken provided by the associated industrial partner (Thomassen international of the Netherlands) and are selected to test the individual element models developed. The first case study is a gas turbine combined heat and power plant. Requirements are to simulate gas-turbine drivers, with their controls and to implement a simple model for the heat recovery boiler. The time history of the steam and power output is simulated during transients caused by trip or change in power requirements. The second case study deals with an ethylene production plant where the steam turbines driving the process gas compressors are simulated; the effect of changes in gas composition on the compressors, optimal control strategies and refrigeration elements are considered in this test case.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Cranfield University
Address
Silsoe Campus Wharley End
MK45 4DT Cranfield
United Kingdom

Participants (3)

ASSOCIATION POUR LA RECHERCHE ET LE DEVELOPPEMENT DES METHODES ET PROCESSUS INDUSTRIELS
France
Address
Boulevard Saint-michel 60
75272 Paris
Thomassen International BV
Netherlands
Address

6990 AB Rheden
UNIVERSITE DE LIEGE*ULG
Belgium
Address
Place Du 20 Aout 7
4000 Liege