Newsletter 2010, February - Issue 2
2010, February - Steam System Simulation Service
S.A.T.E. is completing the investigation of the transient behaviour of the steam system integrated in a large chemical plant (coming to be operating next year).
The system is composed of two trains in parallel with an auxiliary steam generators group, which balances the global steam production and consumption during the operating point variations.
The high pressure steam is generated and superheated by the process waste heat from the chemical section of the plant (not simulated) and feeds the steam turbines driving electrical power generators and process compressors.
The steam system model includes four base pressure levels (corresponding to 4 different headers) and the following equipment:
- 11 steam turbines with steam extraction and injection;
- 6 waste heat boilers;
- 3 auxiliary boilers;
- 6 superheaters;
- 14 attemperators;
- 10 controlled blow off valves;
- 12 control valves;
- over 20 Safety valves;
The implemented control system has more than 50 control loops, which include:
- Speed and extraction controllers of the single and double extraction turbines;
- Speed controllers of the single stage turbines;
- Let down controllers of the steam turbines;
- Temperature controllers;
- Pressure controllers;
- Levels controllers.
The system dynamics was analysed by some significant operational scenarios selected by the Client, including the shut-downs of single equipment or of extended plant sections.
The simulation study allowed the verification of the operational behaviour of the envisaged control scheme.
The figure above represents the operating point of a controlled single extraction turbine during a plant transient, showing the correct behaviour of a single extraction turbine controller, which maintains the operating point near the nominal one against the transient induced by a trip event in another turbine in same train.
