Reliability of TGA data for characterization of alternative biomass feedstocks
Creators: name: Retschitzegger, Stefan
name: Kienzl, Norbert
name: Anca-Couce, Andres
name: Tsekos, Christos
name: Banks, Scott
name: Kraia, Tzouliana
name: Zimbardi, Francesco
name: Funke, Axel
name: Marques, Paula
Publisher: name: Zenodo
Year: 2020

description: With fossil fuels continuing to shrink, but the need for energy growing every day, alternative energy sources have continually to be sought. The impact for biomass is that new feedstocks are getting more and more relevant. However, the application of new feedstocks in thermochemical processes is prone to cause problems due to a different conversion behaviour compared to classic woody biomass. For this purpose different feedstock characterisation methods have been developed. One commonly used method is Thermogravimetric Analysis (TGA), which allows determining relevant chemical reactions and their respective kinetics. Although TGA is widely used, the concordance of results originating from analyses with different TGA systems, often obtained by following individual protocols, is not well studied. Hence, results may differ substantially depending on the institution performing the analyses. This issue is being studied in the Horizon 2020 project BRISK II, which is dedicated to uniting leading European research infrastructures dealing with biofuels. Within the project a TGA round robin has been started currently involving seven partners across Europe. The aim of the round robin is to evaluate pyrolysis, torrefaction and char oxidation/gasification of new biomass feedstocks and to compare results with more known feedstocks like wood. In order to validate the TGA results against literature and to minimise potential inhomogeneity in biomass feedstocks, also Avicel Cellulose PH-105 as a well-defined reference material has been included in the round robin. In the first stage of the TGA round robin pyrolysis of Avicel Cellulose PH-105 and beech wood (homogenised in an ISO certified lab and distributed to all partners) were investigated. For this purpose an experimental procedure was formulated, which was followed by each partner. The evaluation of the first stage of experiments is completed and a main result is presented with the temperature of the maximum reaction rate (peak temperature) at a heating rate of 5 K/min. The mean peak temperature for Avicel Cellulose PH-105 was determined with 325°C, which is in good agreement with literature (327°C - Grønli et al. []). However, the values of the peak temperature within the round robin were ranging from 314°C – 338°C. A comparable range of the peak temperature was found for the beech experiments (335°C – 364°C). The deviation did only depend on the instrument and not on the material investigated. (e.g. minimum temperature for Avicel Cellulose and beech obtained by the same partner). These first data show that the instruments used do have an influence on the results. The ongoing evaluation will help with the determination of the characteristics of the instruments and methods employed by each partner, providing a benchmark for the experiments to follow. By identifying the differences between the various instruments and procedures, it will be possible to obtain meaningful final measurement protocols and results. In future tests within the round robin new biomass feedstocks and different atmospheres will be investigated. Furthermore, additional partner from the European Energy Research Alliance (EERA) are planned to be included in the round robin in order to extend the range of TGA systems considered. The final results will allow a thorough evaluation of the comparability of TGA tests and the factors causing differences. [] Grønli, M., M.J. Antal, and G. Várhegyi, <em>A Round-Robin Study of Cellulose Pyrolysis Kinetics by Thermogravimetry.</em> Industrial &amp; Engineering Chemistry Research, 1999. <strong>38</strong>(6): p. 2238-2244.