Scrubber liquid recovery in small and medium scale biomass gasification sysyems

Scrubbing is widely used in biomass gasification plants for tar removal. However, the cost of the scrubber liquid and its disposal once used can represent a non-negligible part of the plant operating cost. It is possible to lower this cost by regenerating and reusing the scrubber liquid by removing ash and heavy tars with the help of a centrifuge. Data from the two biomass gasification plants Hortlax (Sweden) and Oberwart (Austria) was used for preliminary centrifuge evaluations and a techno-economic study. The results show that installing a centrifuge for scrubber liquid regeneration would be of great benefit in Hortlax but not in Oberwart. A techno-economic study made for two different centrifuges with different capacities (7 m³/h and 20 m³/h respectively) combined with variations in investment cost and scrubber liquid prices showed that the scrubber liquid consumption in Hortlax could be lowered from 85 to 15.7-40.7 l/MWhelectricity for the 7 m³/h centrifuge and 6.2-20.5 l/MWh_electricityfor the 20 m³/h centrifuge. This corresponds to annual savings of 2.3-6 MSEK and 4.5-6.5 MSEK respectively. The payback time for the smaller centrifuge was estimated to 0.5-1.6 years and 0.7-1.3 years for the larger centrifuge.