R&R Consult and VODA A/S rebuilt a waste heat incinerator at the Danish waste handling company RenoSyd I/S. Part of the task was to redesign the secondary air supply and introduce water-cooled boiler walls. R&R Consult provided CFD simulations that mapped and visualized the combustion process before and after the rebuild and was used for optimization of the combustion process by adjusting size and position of the air nozzles. The optimization of the air supply nozzles resulted in a more efficient combustion and improved temperature distribution for the boiler.

Boiler geometry

The simulations were conducted as steady-state solutions, featuring a high-resolution structured hexahedral mesh. The fuel and primary air supply at the grate were included via a bed-model, reproducing the combustion steps:

Heating → Evaporation → Devolatilization → Char combustion → Ash

Air nozzle jets

Secondary air distribution and nozzle design provided information about jet penetration. We included heat transfer in wall materials, water cooling and the heat exchangers and calculated thermal radiation based on local gas composition. The model replicated the internal conditions and provided data as well as an overview that would have been complicated and expensive to attain through physical measurements.

Temperature- and velocity field

Our CFD analysis was also used for finding optimal locations for new temperature sensors and  finally, the model was used to document that boiler operation would meet environmental requirements in terms of a complete combustion process, residence time and minimum temperature.

Temperature field, before and after rebuild