Authors: R. Laubscher, P. Rousseau
Year: 2020
Industry: Fossil Fuel Power Generation
Keywords: Use FSE, Steady state, Dynamic, Boiler, Validation, Comparison
ABSTRACT
The paper presents a coupled modelling methodology that employs a three-dimensional finite volume method computational fluid dynamics model to solve the boiler flue gas side, and a 1D FVM network approach to model the steam side flow and heat transfer of a final-stage radiant superheater. The CFD model includes the necessary upstream components that affect the thermal performance of the superheater, including combustion and heat transfer in the furnace and platen superheater. The methodology is applied to a 620MWe drum-type boiler of which the superheater was instrumented with thermocouples measuring the outlet steam temperatures on the different elements. This was augmented with boiler process data that was extracted from the distributed control system (DCS) for steady-state operation at 99% and 65% boiler loads.
The results show that the approach can capture the details of the temperature maldistribution between legs in the same heat exchanger, between elements in the same leg and between the inner and outer loops of the same element for different load cases. It also captures the steam flow maldistribution between the inner and outer loops. On the flue gas side, the results show that for the part-load case, the high gas temperature and velocity zones are less uniformly distributed compared to the full load case and also less symmetric than in the full load case.
The calculated total heat transfer rates for the evaporator, platen superheater and final superheater compare well with the experimental values for both the 99% and 65% maximum continuous rating load cases. This shows that the coupled simulation models can capture the overall thermal performance of the three heat exchangers modelled here with good accuracy.