KIKAMA
Modelling of CFB boilers (KIertoleijuKAttilaMallinnus)
Principal Investigator at ASE: Yrjö Majanne
Duration of the project: 1.3.2010-31.12.2011 (KIKAMA and KIKAMA II)
Project description:
A modern steam power plant is a complex system comprised of numerous process components. The search for the optimal performance of the complex process under different operating conditions is not simple, because there are several variables that affect the dynamic behaviour of a system.
Simulation is an efficiency method to analyze the behaviour. The main goal of the project is to develop dynamic process models of circulating fluidized bed (CFB) boilers. The developed models can be used to analyse and study the dynamic behaviour of processes. The dynamic models are also useful for process development, control design and training purposes.
In this project, a dynamic process model of a supercritical CFB Benson type once-through utility (OTU) boiler has been developed. In this type boiler a certain part of the boiler can act as an evaporator or superheater depending on the boiler load. This set challenges to the modelling work, because heat transfer and pressure drop correlations are phase-specific. Moreover, the model must also be able to represent the behaviour of the supercritical water. Figure 1 illustrates the simplified structure diagram of the CFB OTU boiler model.
Figure 1. The simplified diagram of the process model.
The water side of the CFB OTU boiler is modelled using a developed generalized water model block. The model block is able to handle thermodynamics of water, saturated water-steam mixture, and superheated steam under sub- and supercritical pressures. A general model block can be used to represent different process components such as the parts of an evaporator, superheaters and economizers. The generalized structure of the model block makes possible the use of the block for the modelling of different type boilers such as the natural circulation and OTU boilers.
The general model type makes it easier to build the process model and keeps the maintenance easy. The one subject of the project is also found ways to optimize simulation speed. The simulation speed of the dynamic simulator is, especially from the point of view of the usability, a factor which is significant.
A dynamic process model of a CFB natural circulation drum boiler also is a subject of the project. The both, the OTU and drum boiler models are based on an earlier CFB drum boiler model from a previous project. The process models consist of the water and the air-flue gas sides.
In addition to the process models, a general model library has been developed. The model library contains model blocks of special process components, as pumps, valves, turbines, fans, etc. The process models and the library were built using Simulink and Matlab by The MathWorks.
Publications:
Yli-Fossi, T., Köykkä, P. and Majanne, Y. (2011). Bensonläpivirtauskattilan vesi-höyrypuolen yleinen dynaaminen malli, Automaatio XIX seminaari 2011, 15-16.3.2011, Finnish Society of Automation, Helsinki, Finland, (In Finnish).
Yli-Fossi, T., Köykkä, P. and Majanne, Y. (2011). A Generalized Dynamic Water Side Model for a Once-Through Benson Boiler, Proceedings of the 18th IFAC World Congress, 28.8.-2.9.2011, IFAC, Milano, Italy.
Funding:
Tekes, Metso Power Oy
Personnel:
Timo Yli-Fossi