Modeling of Wet Scrubber with Heat Recovery in Biomass Combustion Plants

Sammanfattning: During combustion of biomass, particulate matter is emitted, which has severe health impacts on humans. The company ITK Envifront has developed a scrubber technology that cleans the flue gas while also recovering the flue gas energy, increasing the efficiency of the combustion plant. In this thesis, a simulation model was built in MATLAB according to the Finite Element Method. Validation of the model against 3 different facilities showed reasonable accuracy with a tendency to overestimate the scrubber heat recovery and a mean prediction deviation of approximately 7 %. The model was then used to make suggestions for process optimization. An increase of funnel height, and number of spray nozzles could increase the scrubbers heat recovery with up to 7 % and 8 %, respectively. Addition of moisture to the flue gas through evaporation of water droplets had the potential to increase scrubber efficiency with 10 %, and usage of the highest setting of the adjustable nozzle bank showed the potential to increase the efficiency with up to 5 % compared to the mid-setting. Furthermore, the process parameters of a scrubber with optimized running conditions, was compared to a scrubber with the current running conditions, through running of the developed model. The optimized running conditions showed an increase in scrubber efficiency with up to 14 %, resulting in an increase in scrubber heat recovery of approx. 90 kW at a boiler load of 3 MW. As a final conclusion, the developed model shows great potential to be used to as a toolbox to further investigate and optimize the scrubber design and operation. As a future work, it would be interesting to further model its performance regarding particle removal.