University of Twente Student Theses


Torrefaction gradients in biomass

Bos, Frans (2011) Torrefaction gradients in biomass.

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Abstract:Torrefaction is a thermal pre-treatment of biomass in order to (co)-fire biomass in a power plant. Research is done to the differences in torrefaction within a biomass particle. This chapter will briefly describe how this is done. Literature study First a literature study is done about torrefaction. From this study the most commonly used conditions for torrefaction where determined. This turned out to be 1 Hour at 250°C in a Nitrogen (N2) environment. For the experiments a batch reactor with a fixed bed is used. Experiments For the actual experiments two types of wood are used: ‘pallet wood’ and ‘poplar wood’. From the pallet wood four pieces are torrefied in aforementioned conditions. Three pieces of poplar wood where torrefied at 250°C in a Nitrogen environment but for different residence times (60, 45 and 30 minutes). After the torrefaction the blocks are split. Material from the centre and edge of the block is prepared for analysis by grinding it to fine powders. Analysis The two samples of each block are analysed and the results are compared to see if there are any differences in the degree of torrefaction. The samples are analysed in three ways: Heat value, Thermographic Analysis (TGA) and Element Analysis. Results For the pallet wood blocks (all with a residence time of 1 hour) no significant difference can be found between the centre and edge material. Heat values are similar, TGA graphs match (except for what looks like a contamination which gives a different final weight percentage) and Element Analysis show that both samples consist of the same elements and the ratio of the different elements is the same. When the poplar wood is torrefied for 1 hour, again the heat values are the same for the centre and edge samples. But when the poplar wood is only torrefied for 45 or 30 minutes differences appear in the heat values. The heating values of the centre material are higher than the edge material whereas the opposite was expected. This conclusion should be validated by performing more experiments.
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Subject:58 process technology
Programme:Sustainable Energy Technology MSc (60443)
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