Combined CFD, material and system level analyses Case Naantali power plant

Transcription

1 Combined CFD, material and system level analyses Case Naantali power plant MULTISCALE DESING ANNUAL SEMINAR 2013 Jari Lappalainen VTT Technical Research Centre of Finland

2 2 Introduction Computational tools are in every day use in R&D and engineering Process simulation (steady-state, dynamic) Computational Fluid Dynamics (CFD) Specific equipment dimensioning tools, e.g. heat exchangers Material selection and optimization Traditionally tools are developed independently, strictly focused Targeting to excellence for a particular need A practical problem typically fails to hit this focus Mr Customer, did our tool help you with your issue? Yes, partly. Level of details Tool 1 Tool 3 Problem Tool 2 Tool 5 Tool 4 Application domain

3 3 Case Naantali / starting point 135 MWe pulverized coal unit of Fortum, in Naantali Damages in evaporator tubes What happened? Why it happened? What is wrong? Has something changed? Are there local thermal stresses? Can it happen again? References: Lappalainen J., Lilja, R., 2010, Naantalin 3-kattilan höyrystinputkien lämpötilojen analyysi Apros-ohjelmistolla, Tutkimusraportti VTT-R , pp. Lappalainen, J., Blom, H, Juslin, K., Dynamic process simulation as an engineering tool A case of analysing a coal plant evaporator, VGB Powertech, 1/2 2012, pp

4 4 Case Naantali / studies at VTT Material analysis (TK2023) Microstructure of the low alloy tubes suggests locally high wall temperature, resulting in creep damage to limit tube life Possible reasons: Adjustment of operational details Reduced circulation in transients Combined with age Simulation analysis (TK8083) Due to difficult conditions for experimental study Modelling with Apros Simulation of basic operations and exceptional conditions Questions: Are there meaningful differences between the individual tubes? Does the recent change in control strategy causehigher risk than the old one?

5 5 Case Naantali / the Apros platform Commercial software developed since 1986 by VTT and Fortum For modelling and dynamic simulation of industrial processes, including elecrical and automation systems

6 6 Case Naantali / modelling Minimum effort into the modelling Water-steam side with Apros components No flue gas side, combustion power as boundary condition One control loop ONE OF THE 16 EVAPORATOR TUBES MODEL ENDS MODEL BEGINS

7 7 Case Naantali / modelling Information sources Original engineering drawings Printouts of control displays in different operation conditions Other plant documents

8 8 Case Naantali / CFD First Apros results revealed a problem: the original idea to use a constant heat flux to the evaporator tubes gave non-realistic results Recent CFD study (TK5025) helped to estimate local values A kw/m2 A kw/m2 A kw/m2 A kw/m2 0.3 A kw/m2 0.6 A kw/m2 0.9 A kw/m2 1.0 A kw/m2 A kw/m2 0.7 A kw/m2 A kw/m2 0.3 A kw/m2

9 9 Case Naantali / simulation example Comparison of two control (operational) strategies: Dotted line: Level control of separation bottle Solid line: Superheating state control Profiles of the fluid, tube wall inner and outer temperatures when throttling one of the 16 tubes Situation captured when steady state reached (caused 21% reduction in mass flow)

10 10 Case Naantali / conclusions Simulation study of the evaporator tubes Increased understanding what in plant operation affects and how much on the tube wall temperatures Showed no meaningful design-based differences in the individual tube lines Showed the new control strategy rises temperatures in the end of the tube But does not cause meaningful risk Does not explain the tube damages The interpretation of the simulated results (tube wall temperatures) needed material expertise

11 11 Conclusions and future prospects Computational engineering tools were used in solving an engineering problem at the power plant Dynamic simulation to understand the effect of different operational practises CFD study to give insight to the distribution of the combustion heat Material analysis and calculations to understand the practical root cause of the damages and interpret the simulation results Computational tools complete each other The most efficient use of tools depends on the case Supported combination (linking) of tools would enable More multi-tool studies /time unit Better consideration of limitations due to the tool boundaries Freedom to use each tool only at its specific (natural) domain Higher quality results due to tackling problems with a wider view Common platform to share and discuss the problem

12 12 VTT creates business from technology