Als alternativer Brennstoff zu Öl und Zusammenfassung: Gas haben sich Holzpellets im Kleinfeuerungsanlagenbereich etabliert, da diese vergleichbaren Anwenderkomfort aufweisen. Mit der Nutzung von Holz als Brennstoff ist zudem eine nahezu neutrale CO 2 -Bilanz verbunden. Die bisher eingesetzten Verfahren zur Herstellung solcher Pellets basieren auf der Hochdruckverpressung relativ sortenreiner, trockener Holzspäne. In dieser Arbeit wird ein alternatives Verfahren zur Herstellung von Pellets vorgestellt, welches die Verpressung auch feuchter Reststoffe beinhaltet. Es werden die Konversion von Nebenprodukten der Braunkohlenförderung und biogenen Reststoffen zu Pellets und die erreichbaren Pelletqualitäten beschrieben. Composite Pellets out of Biogenic Residues and By-products of Brown Coal ProductionFor small heating systems wood pellets have Abstract: been established as an alternative fuel to oil and gas, because of their user comfort and their neutral CO 2 balance. Up to now, the production process for pellets is based on high pressure compaction of homogeneous and dry wood shavings. In this work, an alternative process for production of pellets is presented, that the compaction of wet material includes. The conversion of byproducts from the brown coal production together with biogenic residues to pellets and the resulting pellet qualities are described.
Xylite is a byproduct of lignite coal production in Germany and, up to now, has normally been used as an additive for potting-soil production. Another possibility to use the residual xylite, however, is to produce fuel pellets out of it. These pellets can be used like wood pellets in domestic and industrial firing systems. Using a novel process based on wet grinding, agglomeration of the wet xylite, and subsequent drying of the raw xylite pellets, it is possible to convert xylite into high-quality fuel pellets without being dependent upon the mechanics of lignin softening. An important aspect for fuel pellets is their CO 2 emissions. This is especially important for xylite, because it is ranked among the fossil fuels. In this work, xylite is mixed with CO 2 -neutral wood to produce composite pellets out of xylite and wood with reduced CO 2 emissions. The topic of this study is the production of composite pellets, which have been produced using the mentioned novel pelleting process under variation of four parameters: wood content, moisture content, material temperature, and binder content. The interaction of these four parameters has been investigated using the design of experiments (DOE) methods. Models could be derived for different pellet quality parameters (i.e., pellet abrasion resistance), which describe the effects and interactions of the four parameters. Evaluation of the significant parameters for pellet qualities was carried out with statistical tests and graphical analysis. It became evident that, in the wet-pelleting process, the moisture content of the raw material and the mass fraction of wood are of great relevance for pellet quality. In contrast, the temperature of the material has no significant effect. The addition of potato starch as a binder results in a steady increase in pellet quality across the entire study.
Der bisher wenig genutzte Reststoff Braunkohlenxylit lässt sich mittels Feuchtpelletierverfahren zu Brennstoffpellets verarbeiten, wobei dem Trocknungsprozess der Rohpellets zentrale Bedeutung zukommt. Trocknungs-und Sorptionsversuche belegen eine aus agglomerationstechnischer Sicht vorteilhafte Schrumpfung der Agglomerate im Verlauf der Trocknung bzw. bei der Wasserentbindung. Weiterhin zeigen die Agglomerate eine Trocknung in zwei Abschnitten. Dabei wird die Trocknungsgeschwindigkeit in erster Linie von der Lufttemperatur beeinflusst. Die Pelletzusammensetzung ist nur von untergeordneter Bedeutung. Schlagwörter: Braunkohle, Braunkohlenxylit, Pelletierung, TrocknungXylite, a by-product of lignite production, can be converted into fuel pellets by using a wet pelletizing process, in which the drying step of the raw pellets is of vital importance. During moisture removal, structural changes take place in the agglomerates, they become harder and investigations of the drying behavior indicate high shrinkage during drying. This effect can also be seen in hygroscopic sorption experiments. Furthermore, the pellets show two drying sections. The main factor affecting the drying speed is the temperature; the pellet composition has a subsidiary effect.
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