Performance of an auger reactor for bio-oil production from heavy metals contaminated biomass

CERESiS (ContaminatEd land Remediation through Energy crops for Soil improvement to liquid biofuel Strategies) project, granted under EU Horizon2020 research and innovation programme, intends to promote land decontamination through phytoremediation by growing energy crops to produce clean biofuels. In this context, the project aims to demonstrate the potential of two thermochemical processes, i.e. Supercritical Water Gasification (SCWG) and Fast Pyrolysis (FP) for the production of key bio-fuel precursors suitable for further upgrading from contaminated biomass. The aim of our research activity is to design a FP system which allows to obtain at the same time high yields and low levels of contaminants in the bio-oil. The auger reactor configuration was chosen. The advantages of using an auger reactor are summarized as follows: oProven technology. oWide range of particle sizes that can be processed. oGood control of residence time and temperature. oGood mixing characteristics. In contrast, the main disadvantage is the high cost of maintenance required, given the presence of moving parts and possible tar condensation on the shaft when an auger reactor heated only indirectly through the external wall is used. To deal with tar condensation problems the reactor is heated by three independent induction heaters that allow reaching high heating rates of the shaft with great efficiency. A two-stages fractionated condenser, a cyclone and an electrostatic precipitator are used to selectively capture solids and condensable products. The auger reactor was designed to valorize contaminated biomass coming from phytoremediation adapting the plant and operational parameters to the presence of inorganic contaminants. Both pelletized and ground contaminated biomass can be used as feedstock for bio-oil production. Further investigations are needed to assess the possible effect of feedstock size on pyrolysis products yields and heavy metals speciation and distribution.