High solids firing in an operating recovery boiler - comparison of CFD predictions to practical observations in the furnace

Three-dimensional flow simulation was applied to analyze the high solids firing processes in a 3 150 tds/d recovery boiler. The flow field, combustion, heat transfer, and the concentration of nitric oxide (NO) were modeled with the commercial Fluent/UNS code using strong local refinement of the computational grid. For prediction of nitric oxide (NO) emissions a postprocessing technique was used. Different simplified ammonia oxidation mechanisms available were tested. The study shows that this kind of modeling can be successfully applied to a 3 150 tds/d recovery boiler. In addition, the possibilities to reduce the NOx emission by odorous gas firing (reburning) in the recovery boiler furnace are discussed based on one-dimensional calculations