Developing an operating instruction to attenuate pressure stress during fuel shortage events of a power boiler based on dynamic modelling

•An operating instruction is proposed to compensate lack of pressure controller.•The boiler superheater stress is reduced 84.5% utilizing the optimized instruction.•Sensitivity analysis shows instruction performance despite imprecise implement.•A ninth-order nonlinear state space model is developed...

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Bibliographic Details
Published in:Applied thermal engineering 2022-01, Vol.200, p.117565, Article 117565
Main Authors: Mahmoudi, Farhad, Najafabadi, Tooraj Abbasian, Moarefianpour, Ali
Format: Article
Language:English
Subjects:
Boilers
Combustion control
Control equipment
Control oriented model
Cyclic stress reduction
Dual-fuel boiler
Dynamic models
Forced circulation subcritical power boiler
Fuel shortage event
Fuels
Interpolation
Manual control
Mathematical models
Measurement
Model accuracy
Monte Carlo simulation
Nonlinear state space model
Operators (mathematics)
Optimization
Parameter sensitivity
Power plants
Sensitivity analysis
Shortages
Shutdowns
State space models
Tubes
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Summary:•An operating instruction is proposed to compensate lack of pressure controller.•The boiler superheater stress is reduced 84.5% utilizing the optimized instruction.•Sensitivity analysis shows instruction performance despite imprecise implement.•A ninth-order nonlinear state space model is developed to predict boiler dynamics.•A gray box identification procedure is introduced using only steady state data. Stress control of boilers is a major concern in the aged power plants. The studied forced circulation boiler suffers from a malfunction of the combustion control system. In order to reduce cyclic stress on boiler equipment and prevent undesirable shutdowns of power unit during fuel shortage events, an operating instruction is proposed. In order to predict dynamic behavior of the boiler, a nonlinear state space model is developed using mathematical modelling approach. A gray box identification procedure is introduced using only steady state measurements of plant. The dynamic model is verified compared to actual plant data and accuracy of model parameters is evaluated by sigma-normalized sensitivity analysis. Considering aim of steam pressure regulation, a three-step optimization approach is proposed based on golden section search, parabolic interpolation and interior-point methods to optimize arbitrary parameters of the proposed manual control scheme. Simulation results for different loads and various fuel limitation scenarios show that proposed instruction improves the cyclic stress in superheater tubes at least 84.5%. In addition, Monte Carlo experiments illustrate despite a 10% operators’ error in implement of the instruction, the stress is still reduced by an average of 78.1% for a given case.
ISSN:1359-4311
1873-5606
DOI:10.1016/j.applthermaleng.2021.117565