Reaction and Transport within single pyrolysing wood particles - Modelling and experimental validation with in-situ measurements

点击翻译按钮获取中文摘要

The present proposal is based on the close cooperation between the Leibniz Institute for Plasma Science and Technology (INP Greifswald) and the Technische Universität Berlin – Chair for Energy Process Engineering and Conversion Technologies for Renewable Energies (EVUR-TUB). By bringing together the expertise of both groups in laser-based spectroscopic techniques and thermochemical conversion processes, a well-known problem - the lack of understanding of the pyrolysis mechanism, critical in any thermochemical conversion process - is approached from an innovative perspective. In the now-ending project the strategy to work on identical reactors at different places without the need to transfer two analytical methods to the respective other partner has been proven successful. The comparability of both experiments was assessed and results coming from IRLAS and from LIF can be combined. It is their combination what allowed us to advance in the characterization and understanding of the pyrolysis process and to achieve novel findings such as the difference in the pyrolytic behaviour between beech and pine wood, observable in the permanent gas composition, evolution of polycyclic aromatic hydrocarbons (PAH) and exothermicity. This is not only attributed to the different structure and composition of the two types of wood, but also to the different content of inorganics and their influence on the pyrolysis conversion. However, the present project has also shown that a higher sensitivity in the spectroscopic techniques (IRLAS and LIF) is required to be able to detect further volatile species for a better and more detailed understanding of the pyrolysis mechanism, as well as to improve the quantification capabilities. At the same time, the pyrolysis community has recently highlighted the need to: (1) include the presence of heterogeneous secondary reactions in kinetic models, (2) determine the influence of inorganic species on product distributions and secondary reactions, (3) improve gas-phase models accounting not only for further formation of gas species, but also for the formation of BTX, PAH and soot, and (4) improve characterization of the experimental process, specifically regarding the released volatiles and the heat of reactions. The combination of our own findings together with the knowledge gaps identified by the pyrolysis community motivate us to continue with this direction of research and to design a prolongation project for 24 months. Here the main outcome will be to include heterogeneous secondary reactions in the pyrolysis kinetic mechanism, i.e. to determine not only the influence of these reactions on the volatiles composition, but also on the reaction enthalpies and the process kinetics as well. To achieve this, other objectives such as increasing the sensitivity and quantification capabilities of the spectroscopic systems and improving the characterization of the physical phenomena taking place in the reactor need to be achieved.