An integrated study of flue gas flow and superheating process in recovery boiler using computational fluid dynamics and ID-process modelling

Superheaters are the last heat exchangers on the steam side in recovery boilers. They are typically made of expensive materials due to the high steam temperature and risks associated with ash-induced corrosion. Therefore, detailed knowledge about the steam properties and material temperature distribution is essential for improving the energy efficiency, cost efficiency and safety of recovery boilers. In this work, for the first time, a comprehensive ID-process model (1D-PM) for superheated steam cycle is developed and linked with a full-scale 3D CFD (computational fluid dynamics) model of the superheater region flue gas flow. The results indicate that first; the geometries of headers and superheater platens affect platen-wise steam distribution. Second, the CFD solution of the 3D flue gas flow field and platen heat flux distribution coupled with the 1D-PM affect the generated superheated steam properties and material temperature distribution. These new observations clearly demonstrate the value of the present integrated CFD/1D-PM modelling approach. It is advantageous for trouble shooting, optimizing the performance of superheaters and selecting their design margins for the future. The developed integrated modelling approach could also be relevant for other large-scale energy production units such as biomass-fired boilers.