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Gewählte Master / Diploma Thesis:

Franziska Meier (2014): Pellet off-gassing during storage: The impact of storage conditions and type of source material.
Master / Diploma Thesis - Abteilung für Chemie nachwachsender Rohstoffe, BOKU-Universität für Bodenkultur, pp 90. UB BOKU obvsg FullText

Data Source: ZID Abstracts
In the past decade nine fatal accidents in pellet storages have occurred, which were related to off-gassing. Investigations showed that dangerous levels of CO and increased concentrations of CO2, VOC and CH4 can arise, while O2 is consumed. As there is still unclarity about the causative mechanisms further investigations are needed. In this master thesis the influences of the raw material base and of O2 availability on off-gassing was investigated and the emission behaviour in the first seven days of storage was characterized. In the first experiment twelve different pellet samples, consisting of spruce or pine wood or mixtures thereof, were stored for seven days. Second, identical pellet samples were investigated over at least eleven days at 34%, 20% and <1% O2 at trial start. The emission rates of CO, CO2, VOC and CH4 were compared. A new experimental set-up was established including a lab-scale pellet tank and a GC-FID/TCD allowing a highly controlled process. Pellet screening showed that pine wood pellets caused higher emission rates of CO, CO2, VOC and CH4, whereas pine ratio was not related directly with the emission rates. Apart from the influence of the raw material, a clear positive relation between the single emission gases was indicated. The second experiment demonstrated the higher O2 concentration to stimulate CO, CO2 and CH4 generation, whereas VOC was not affected significantly. However, comparing the rates at 34% O2 and <1% O2, it was revealed that emission rates were affected less than expected. CO generation was suppressed by a half and CO2 by a quarter. It was obvious that gaseous O2 was not the exclusive source for the generation of O2-containing emission gases. In the trial with 20% O2 this trend was confirmed. Moreover it was shown that emission rates of CO and CO2 decreased with falling O2 concentration, which was present upon sealed storages as consequence of oxidative processes.

Beurteilende(r): Rosenau Thomas
1.Mitwirkender: Liebner Falk

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