Striving for Operational Excellence: A Holistic Approach through Dynamic Study & Performance Test
A case study of an integrated steam and power system at Iggesund Paperboard, Sweden.
This paper details a case study of the project at Iggesund Paperboard, Sweden, where an innovative holistic methodology was used to carry out dynamic simulation studies and comprehensive testing of an Integrated Steam and Power System network. The primary objective was to identify and address system bottlenecks, leading to improved productivity and increased reliability with a short return on investment.
Introduction
Iggesund Paperboard, a top-quality board producer situated on the east coast of Sweden, places strong importance on steam network pressures because of their impact on product quality.
Solvina was asked to design and tune the steam-network control before the installation of a new boiler and turbine.
The plant modification included a new recovery boiler, a new 110 bar steam header, a new back-pressure turbine with several extractions replacing two existing turbines, and steam reduction valves.
Control Design Scope
Solvina was asked to design and tune the steam-network control for demanding operating conditions and transients.
- Large steam-load transients
- Turbine trip
- Start and stop of large electric motors during island operation
Purpose
The purpose was to assure efficient and safe commissioning, a well-functioning plant and trained operators for operational transients associated with the installation of the new recovery boiler and turbine.
Scope of Work
- Design of steam-network control for three boilers, a turbine with six valves and 35 bypass valves.
- Simulation of transients using models describing thermodynamics and the electrical power system.
- Training of operators using a training simulator for different emergency situations.
- Testing of island-operation capability.
Method
The boilers, turbine with several extractions, steam accumulator, six steam headers with different pressure levels, pressure-reducing valves and the electrical power system were modelled.
A control strategy for maintaining pressure in the different steam networks was developed and tested through multiple simulation scenarios in both grid-connected and island operation.
Switching from grid operation to island operation was also included among the scenarios, and the control system was tuned before commissioning.
Results
The design and tuning of the control strategy required extensive simulations to meet the steam consumers' requirements for steam conditions under different scenarios.
Commissioning tests showed that the resulting control design and tuning was functioning effectively, contributing to a smooth and efficient startup.
Board Machine Stop & Restart in Island Operation
One of the simulated scenarios involved a board-machine stop followed by a restart while operating in island mode.
At approximately 800 seconds, the board machine stopped, producing a large instantaneous steam-load reduction. The bark boiler responded gradually while the steam accumulator was charged.
The steam flow through the turbine was redistributed during the transient. The control system handled both the changed steam-load condition and the electrical disturbances.
At approximately 2000 seconds, the board machine restarted and steam loads returned towards normal. The bark boiler increased its output while the steam accumulator was discharged.
Conclusion
Through dynamic modelling and simulation, the control system could be effectively designed before commissioning, allowing startup to be fast and efficient.
The resulting control strategy proved robust during different transients. The turbine trip, identified as the biggest concern, was handled effectively while steam pressures remained stable and within acceptable limits.
What you'll learn
Through dynamic modelling and simulation, the control system could be effectively designed before commissioning, allowing startup to be fast and efficient. The resulting control strategy proved robust during different transients. The turbine trip, identified as the biggest concern, was handled effectively while steam pressures remained stable and within acceptable limits.