Date of Award
Master of Engineering Science
Chemical and Biochemical Engineering
Dr. Franco Berruti
Dr. Cedric Briens
Fluidized bed biomass pyrolysis is a process that is becoming popular for the conversion of agricultural, municipal and forestry residues into liquid bio-oils, solid biochar and gaseous products. Bio-oil vapors leave the reactor vessel with the produced gases. Also produced however, is a low density biochar particles which accumulate in the bed. Though some fine biochar particles can be elutriated, a significant amount remains in the bed. Accumulation of biochar leads to poor process stability and defluidization of the bed. Moreover, biochar may have negative effects on the pyrolysis reactions. In the current implementation of a mobile pyrolysis unit, the biochar is removed intermittently from the fluidized bed by stopping biomass feeding, and reducing the fluidization velocity to promote segregation, allowing subsequent removal of the biochar layer with a vacuum line.
The initial of objective of this thesis was the optimization and quantification of the performance of the batch biochar removal process. The second objective was to develop a new, continuous biochar removal system.
A batch process using particle separation through density and removal with overflow ports during fluidization, was used to quantify the amount of disruption to fluidization from different loadings and sizes of biochar, therefore determining the feasibility of a batch removal. The main problem encountered with the batch removal was the inconsistent bed composition throughout the removal process, which can reduce the yield of valuable liquid product. The knowledge acquired during the optimization of the batch process was used to design a novel continuous system. The novel continuous system operated at steady state and allowed for high purity biochar removal, and was more than capable of continuously removing the biochar
generated in a practical pyrolysis process. This novel system has been included for use in a full- scale pyrolysis unit, since it will allow the unit to run continuously while controlling the concentration of biochar within the pyrolysis reactor.
Mara, Craig Charles Wilson, "An Investigation of Biochar Removal Systems for Pyrolysis Reactors" (2011). Digitized Theses. 3626.