R&R Consult, COWI and VODA A/S helped Danish waste handling company RenoNord I/S rebuild its waste heat incinerator by adding supplementary firing burners to the furnace. R&R Consult developed a CFD model of the boiler to optimize the location of the burners and to document that environmental requirements were met.

Figure 1: Boiler geometry

The simulation modelled the complete boiler geometry, including grate sections, secondary air nozzles, heat exchangers, wall elements and, of course, the burners. Based on actual operating conditions, we supplied the modelled boiler with combustion air, and added flu gas from the grate based on the exact thermochemical fuel composition from our grate model. The CFD model also detailed the secondary burners, which were to provide supplementary heat under adverse conditions and during start-up.

The results provided valuable information on the temperature and velocity distribution inside the boiler, as well as the combustion process and distribution of gaseous species. We mapped the information and visualized it in order to gain a comprehensive understanding of the internal process that would have been complicated and expensive to obtain through physical tests and measurements.

Temperature field
Velocity field

Figure 2: Temperature- and velocity field

The supplementary burners were optimized, numbers and positions, which increased their ability to preliminarily heat the boiler during start-up and supply additional heat during low-quality fuel scenarios. This also documented that under all conditions, the waste heat incinerator would meet environmental requirements.

Supplementary burners inactiveSupplementary burners active

Temperature field before and after rebuilding