The aim of the project is to determine the reaction paths of common tar surrogates with metal oxide particles. More specifically, the reactions will be studied under reducing atmospheres and with variable oxidations state of the metal. Indirect dual fluidized bed gasification (DFBG) of biomass is a proven method for efficiently converting biomass to syngas, which can be used as feedstock for renewable liquid transportation fuels, a prioritized political goal in Sweden. Since the erection of the Chalmers 2-4 MW dual bed gasifier in 2007, significant advances in the technology have been made, leading up to the recent commissioning of the 32-MW GoBiGas indirect gasifier in Gothenburg. In spite of the progress made, the technology is burdened with costly gas cleaning steps downstream of the gasifier, with tar formation the most severe problem to solve. However, the DFBG-technique offers a unique potential to oxidize the tars inherently in the process. This is due to use of interconnected fluidized beds, where the gasification takes place in one bed, and the combustion in another. Commonly, the bed material is sand or olivine sand, but it could also be possible to replace all or part of the bed material with Fe- and Mn metal oxides from minerals, or steel industry waste products. These are known oxygen carriers and could potentially enhance tar conversion though partial oxidation, but could also provide sites for catalytic decomposition at lower oxidation states of the metal. It is expected that conditions in the gasifier are such that both catatytic and non-catalytic processes are occurring simulataneously. The project will use a unique methodology for studying the reaction between important tar surrogates, C6H6, C6H7 and C2H4, with Fe- and Mn-based metal oxides in a controlled environment. By using small batch fluidized bed reactors with rapid measurement of relevant tar species, the reaction rate and selectivity can be determined as a function of the oxidation state of the metal oxide. In this way both the catalytic and non-catalytic (partial oxidation) effects can be determined, and reaction mechanisms established. Stringent and detailed experiment evaluation of different active materials will provide better data for establishing the reaction pathways of tar compounds, and lead to a better fundamental understanding of the underlying mechanisms. This research will likely result in knowledge which can be used for further development and optimization of the indirect gasification technology.
Docent vid Chalmers, Physics, Theoretical Physics
Funding Chalmers participation during 2016–2019