Numerical simulation of the biomass combustion in the fired pulverized fuel boiler.

A computational fluid dynamic (CFD) model was applied for a 200 Mwe pulverized fuel boiler in Uppsala (Sweden). Peat, demolition wood and wood residuals were used as fuel. The purpose of this work was to investigate the influence of installed burners on the combustion process for biomass fuel and provide the information how to optimize combustion process with different set-up of the used burners. The modelling provided the knowledge of the temperature distribution over the flue gas side of the boiler for different operational conditions and helped to identify the furnace walls with high propensity to slagging. The CFD computer code FLUENT was used for the 3D modelling of the combustion process inside the boiler. Operational data were used to model the furnace, installed burners and the first flue gas path of the boiler for several possible configurations of the burners and fuel load. The RNG k-? turbulence model together with wall functions was adapted for characterization of the flue gas behaviour. Reaction between fuel and oxidizer was modelled using the mixture-fraction/PDF approach. This modelling approach considers all physical processes as turbulence, radiation, combustion etc. The CFD calculations were compared with the acoustic pyrometry measurements, process data and a physical model of the steam water cycle. The comparisons of predicted results obtained with measured data indicate good agreement. On the basis of verified cases, some theoretical settings of the burners have been investigated. The purpose of it was to find limits for a usable range of swirling angles of the burner turbulators. The simulations have pointed out that a proper burner set-up could change behaviour of the combustion process inside the furnace in a positive way.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi