Computationally inexpensive CFD modeling of sewage sludge and waste additive combustion experiments in an entrained flow reactor

A computationally inexpensive, mixture-fraction-based CFD model was applied to investigate the combustion characteristics of two types of sewage sludge powder. These were mixed with meat and bone meal (MBM) and cement bypass dust (BPD) as additives. Experiments on a semi-industrial furnace were performed to obtain validation data. A wide range of operating conditions across eight different scenarios, varying by sludge type, additive combinations, and combustion settings, including over- and substoichiometric conditions as well as slight oxygen-enhancement were tested. All fuel-additive mixtures were adjusted to a basicity ( B 1 = C a O / S i O 2 ) of one. Numerical simulations of entrained flow combustion were performed, and the CFD model’s predictions were validated against the experimental measurements and observations. Results showed that MBM had a significant impact on combustion behavior. When MBM was used to adjust the basicity, it increased the heat release in the furnace by up to 57% for sewage sludge with a lower initial basicity. This effect was attributed to the higher heating value of MBM. However, the MBM also displayed a slower burnout rate compared to sewage sludge powder with BPD, indicated by spatial trends in the gas phase measurements. This was likely due to the larger particle size of the MBM. In contrast, BPD had a negligible impact on combustion behavior. Overall, the CFD model demonstrated very good agreement with the experimental data, confirming its effectiveness as a tool for research, development, and process up-scaling. • Insights into waste-based combustion with additives in an entrained flow reactor. • The effect of additives used to adjust the basicity ( B 1 = C a O / S i O 2 ≈ 1 ) is discussed. • Novel, computationally inexpensive CFD model proves useful for up-scaling. • Very good match between experimental and simulated results. • Meat and bone meal significantly affects combustion behavior and heat release.