Modelling of Effects of Process Inputs on Conditions in a BFB Furnace

The goals of the presented study are 1) a better understanding of effects of process inputs on bubbling fluidized bed combustion and 2) a simplified numerical description of furnace behaviour that can be linked to dynamic 1D power plant simulation.Ways to utilize results of computational fluid dynamic (CFD) simulations of the furnace as the basis of 1D modelling are considered.In the study, a bubbling fluidized bed furnace is simulated with a CFD model in a wide range of conditions.The main variables altered in the simulations are boiler load, fuel moisture, air ratio and air distribution.The main effects of the studied variables on the conditions inside the furnace and on heat transfer rates on evaporator and super heater surfaces are analysed.The analysis shows that load is the main factor determining temperature and concentration distributions in the furnace.Fuel moisture has also a significant effect.Air ratio and air distribution have, as expected, significant effects on concentration distributions but also effects on temperature distribution.Heat transfer rates to different heat transfer surfaces are dependent on the temperature distribution and thus the effects are similar.In the paper, the possibilities to use the generated data as basis for a simplified furnace model are discussed.Examples of correlations that can be derived based on the simulation data are presented and the general approach to link the results to 1D modelling is outlined.