CFD-driven investigation on improving heat recovery in centrifugal wet scrubbers

Mitigating global warming requires a rapid transition to carbon-neutral energy sources, with biomass-based heat production being a significant contributor. Wet scrubbers equipped with heat recovery enhance fuel efficiency by utilizing waste heat while removing particulate matter from flue gas. In this study, a Computational Fluid Dynamics (CFD) model was developed to investigate heat recovery and flow dynamics in a centrifugal wet scrubber installed at a 3MW_th biomass-fired district heating facility, achieving an annual heat recovery of approximately 2 GWh. The model was validated against process data, showing a prediction error of 3.4 %, which is lower than other simulation models for similar purposes. This model, complemented by an Analysis of Variance (ANOVA), was used to explore different optimization strategies, including enlarging the contact zone opening, pre-scrubber moisture addition to the flue gas, and new compact geometries. Three scrubber designs were examined in-depth, focusing on gas flow, as well as heat and mass transfer. Increasing the contact zone opening from 100 to 150 mm yielded a 2 % boost in heat recovery. Coupling this design improvement with moisture addition can potentially elevate heat recovery by approximately 9 % over the conventional design. The new compact scrubber design can potentially increase heat recovery by 2.7 %, and further up to 9 % when combined with the moisture addition strategy. Notably, this compact geometry showed superior radial velocity and heat recovery, offering significant potential for material and space savings. This study provides valuable insights into the optimization of centrifugal wet scrubbers for improved heat recovery efficiency.