| We have undertaken for clients a number of
process and control-system design and performance studies requiring the dynamic simulation of site-wide steam systems, such as for
Natural Gas Processing, LNG production and Co-Generation and oil Refinery
Projects. Project working arrangements have included both studies carried out entirely at our premises, and studies carried out entirely at client's premises - with the dynamic simulation studies and the results an integral part of the ongoing process and control-system design and development.
 The modelling, simulation engineering and control-system performance studies were undertaken ourselves, or working with our associates to combine the necessary modelling and engineering skills according
to scope.
Simulation engineering was carried out in Simulink®. Documented test-case results and completed simulations with KHACE Embedded Technology technology were delivered to the client under license for archive, for reference and for continued use and development by the client. Extracts from typical models and plots appear alongside.
Scope of the modelling and dynamic simulation engineering has typically included: steam boilers and heat-recovery steam generators (HRSGs) together with their condensate and feed-water systems, site-wide steam distribution headers and let-down stations, and steam consumers - especially steam-turbines for motive power and electrical generation.
 There is a need with site-wide steam systems to ensure that process and control-system dynamic responses to major disturbances are maintained within acceptable operational limits for steam users. A temporary excess of steam production over consumption is not usually a problem; because it can be disposed of (at a cost). However a transient shortage of steam, such as might be caused by a boiler trip, is much more serious. Steam consumers introduce a positive-feedback mechanism into the system. As steam pressure falls, so does the energy that can be extracted from every unit mass. Consumers
such as steam-turbine controls therefore call quickly for higher steam flows, which exacerbates the shortage. The trip of a gas turbine feeding an HRSG can be doubly troublesome: not only is steam production lost from the HRSG, but there may be a rapid demand for extra steam from steam-turbine driven generators. It is essential that the right combination of steam-system reservoir capacity, speed of response of steam producers and re-allocation of consumer loads is achieved, to prevent an unrecoverable fall in steam pressure and a complete system shut down.
 Test case studies for the dynamic simulation typically included examining worst-case steam system and power generation responses to trips of major steam producers and consumers. For some locations the worst-case conditions vary significantly between
summer and winter - with gas-turbine efficiencies and process loads varying significantly with ambient temperature.
Steady-state solutions from the dynamic simulation were matched to those from steady-state simulations, where appropriate. Since a dynamic simulation typically contains more plant detail, such as geographic representation of pipe runs with details of head losses for bends and pipe fittings, the steady-state solution from the dynamic simulation often leads the steady-state simulation in accuracy.
Training courses covering the modelling basis, use and extension of the simulation models for end-users were also supplied on request. | 
