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

本提案基于莱布尼茨等离子体科学与技术研究所(INP Greifswald)和柏林理工大学--可再生能源过程工程和转换技术教席(EVUR-TUB)之间的密切合作。通过将两个小组在基于激光的光谱技术和热化学转化过程中的专业知识结合在一起，从创新的角度解决了一个众所周知的问题--缺乏对热解机制的了解，这在任何热化学转化过程中都是至关重要的。在现已结束的项目中，在不同地点处理相同的反应堆而不需要将两种分析方法转让给各自的另一个合作伙伴的战略已被证明是成功的。评估了两个实验的可比性，来自IRLAS和LIF的结果可以合并。正是它们的结合，使我们能够在表征和理解热解过程方面取得进展，并获得新的发现，如山毛榉和松木热解行为的差异，在永久气体组成、多环芳烃(PAH)的演化和放热方面可以观察到。这不仅与两种木材的结构和组成不同有关，还与无机物含量不同及其对热解转化的影响有关。然而，本项目也表明，光谱技术(IRLAS和LIF)需要更高的灵敏度才能检测到更多的挥发性物质，以便更好和更详细地了解热解机理，以及提高量化能力。与此同时，热解界最近强调需要：(1)在动力学模型中考虑非均相二次反应的存在，(2)确定无机物种对产物分布和二次反应的影响，(3)改进气相模型，不仅考虑气体物种的进一步形成，而且考虑BTX、多环芳烃和碳烟的形成，以及(4)改进对实验过程的表征，特别是关于释放的挥发物和反应热。我们自己的发现与热解社区确定的知识差距相结合，激励我们继续这一研究方向，并设计一个24个月的延长项目。这里的主要结果是将非均相二次反应纳入热解动力学机制，即不仅确定这些反应对挥发分组成的影响，而且还确定这些反应对反应热和过程动力学的影响。为了实现这一目标，还需要实现其他目标，如提高光谱系统的灵敏度和量化能力，以及改善对反应堆中发生的物理现象的表征。

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.