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Diepenbeek, Belgium

Stals M.,Hasselt University | Thijssen E.,Hasselt University | Vangronsveld J.,Hasselt University | Carleer R.,Hasselt University | And 2 more authors.
Journal of Analytical and Applied Pyrolysis | Year: 2010

Phytoremediation crop disposal is a problem inhibiting the widespread use of the remediation technique. Flash pyrolysis as processing method for metal contaminated biomass is investigated: the rather low pyrolysis temperature prevents metal compounds from volatilisation while valuable pyrolysis oil is produced. Both plant stems and leaves are pyrolysed in a lab-scale semi-continuous reactor. Parameters under investigation are pyrolysis temperature (623, 723 and 823 K), the use of hot-gas filtration to prevent entrained flow and the blended pyrolysis of willow stems and leaves in their natural weight ratio. Biomass and pyrolysis products are analysed with the focus on the metal distribution; target elements include Zn, Cd, Pb and Cu. Knowledge of the metal distribution is of prime importance concerning the applications of the pyrolysis product streams. ICP-AES measurements confirm very low levels of metals in pyrolysis oil produced at 623 K (Cu and Zn <5 ppm; Cd and Pb <1 ppm) with almost all of the metals accumulated in the char/ash residue. Pyrolysis mass and energy balances are determined providing information in view of future valorisation purposes. Flash pyrolysis can likely offer a valuable processing method for heavy metal contaminated biomass, thus limiting the waste disposal problem associated with phytoremediation. © 2009 Elsevier B.V. All rights reserved. Source

Stals M.,Hasselt University | Carleer R.,Hasselt University | Reggers G.,Hasselt University | Schreurs S.,NuTeC | Yperman J.,Hasselt University
Journal of Analytical and Applied Pyrolysis | Year: 2010

Flash pyrolysis of heavy metal contaminated hardwoods originating from phytoremediation is studied. Different kinds of hardwoods, i.e. Salix fragilis (crack willow), Salix jorunn ("Jorunn" willow) and Populus grimminge (Grimminge poplar) are compared in a preliminary phase. Salix fragilis scores the best on both remediation capabilities and pyrolysis characteristics. Therefore, this cultivar is chosen for in-depth research. S. fragilis stems, leaves and stems mixed with leaves are pyrolysed. The effect of the pyrolysis temperature (623, 723 and 823 K) and the use of a hot-gas filter on the yield and properties of pyrolysis oil and char/ash residue are studied. Pyrolysis of stems at 723 K yields the most pyrolysis oil; while highest char production is obtained when pyrolysing leaves at 623 K. Pyrolysis of mixed stems and leaves at 723 K yields more gas than the pyrolysis of stems or leaves at 723 K. The use of a hot-gas filter does not influence the composition of the pyrolysis oil significantly. In all the experiments performed, the pyrolysis oil main constituents are phenolics. Pyrolysis of stems at 623 and 723 K yields a pyrolysis oil which does not contain considerable amounts of heavy metals. © 2010 Elsevier B.V. All rights reserved. Source

Smets K.,Hasselt University | Adriaensens P.,Hasselt University | Reggers G.,Hasselt University | Schreurs S.,NuTeC | And 2 more authors.
Journal of Analytical and Applied Pyrolysis | Year: 2011

Biomass waste is a promising source of renewable fuels and value-added chemicals. Rapeseed cake, the solid waste after pressing of rapeseed, is a biomass with such a potential. In this study, the possibilities of flash pyrolysis to convert rapeseed cake into a liquid form are investigated. Flash pyrolysis experiments are performed at four constant temperatures (350, 400, 450 and 550 °C) using a home-built lab-scale semi-continuous reactor. It is found that higher pyrolysis temperature results in a higher yield of pyrolysis liquid, while the yield of char (solid residue) decreases. At each investigated temperature, the pyrolysis liquid separates spontaneously into an oil and a water fraction. At 550 °C, the oil fraction reaches a maximum yield of 42.1 wt%, contains only 6.7 wt% water and has a high calorific value of 32.8 MJ/kg. All oil fractions are characterized with complementary analytical techniques. GC/MS analysis shows compounds related to triglycerides in the rapeseed cake as the major compounds at all temperatures, together with a minor amount of oxygenated compounds. GPC and HPLC analyses indicate that the increased yield of the oil fraction at higher pyrolysis temperature is mainly caused by enhanced flash distillation of the triglycerides with only a small degree of degradation into fatty acids. This is confirmed by FTIR and 1H NMR spectroscopy. © 2010 Elsevier B.V. All rights reserved. Source

Smets K.,Hasselt University | Adriaensens P.,Hasselt University | Vandewijngaarden J.,Hasselt University | Stals M.,Hasselt University | And 4 more authors.
Journal of Analytical and Applied Pyrolysis | Year: 2011

Pyrolysis converts biomass waste mainly into pyrolysis oil, which is a possible source of renewable energy and/or value-added chemicals. A very important characteristic of pyrolysis oil is its water content. Karl Fischer titration and azeotropic distillation by the Dean-Stark method are two common techniques for water determination. In this study, the water content is determined for several pyrolysis oil samples with a wide range in water content and/or originating from different types of biomass. The results of the conventional techniques are compared with these of a new proposed technique based on 1H NMR spectroscopy. Azeotropic distillation turns out to be very sensitive for overestimation of the water content in case of pyrolysis oils with high amount of water soluble volatile organic compounds. Therefore, a GC/MS-correction is applied to these results. After correction, the results of the azeotropic distillation are in good agreement with these of the Karl Fischer titration. This strongly indicates that Karl Fischer titration and GC/MS corrected azeotropic distillation are free of interferences for the investigated pyrolysis oil samples, since similar results are obtained by two independent methods. The results of the 1H NMR spectroscopy are very comparable with these of the conventional techniques for the oil samples with low and intermediate water content (<50 wt%). Only for samples with very high water content, 1H NMR gives an underestimation in comparison with the conventional techniques. Hence, 1H NMR spectroscopy is a possible alternative water determination technique for most pyrolysis oils. © 2010 Elsevier B.V. All rights reserved. Source

Velghe I.,NuTeC | Velghe I.,Hasselt University | Carleer R.,Hasselt University | Yperman J.,Hasselt University | Schreurs S.,NuTeC
Journal of Analytical and Applied Pyrolysis | Year: 2011

To obtain information on the potential of thermal conversion (pyrolysis) of municipal solid waste (MSW), a thermogravimetric study (TGA) is performed in a stream of nitrogen. Based on TGA results, pyrolysis experiments are carried out in a semi-batch reactor under inert nitrogen atmosphere. Slow pyrolysis is performed up to 550 °C (heating rate of 4 °C/min). Fast pyrolysis is performed at 450, 480, 510 and 550 °C and different input transfer rates (12 or 24 g material/min). The pyrolysis products are studied on composition and yield/distribution and investigated for their use as valuable product. The liquid obtained by slow pyrolysis separates spontaneously in a water rich product and an oily product. For all fast pyrolysis conditions, a viscous, brown oil which contains a poly(ethylene-co-propylene) wax is obtained. Composition analyses by GC/MS of the oil products (slow/fast pyrolysis) show that aliphatic hydrocarbons are the major compounds. The pyrolysis oils have high calorific value (between 35 and 44 MJ/kg), low wt% of water (around 6 wt%) and a low O/C value (between 0.2 and 0.3). The presence of waxy material is probably due to incomplete breakdown of poly(ethylene-co-propylene) present in MSW under study. The optimal pyrolysis conditions, regarding to oil yield, fuel properties, and wax yield is fast pyrolysis at 510 °C with 24 g material/min input transfer rate. The fast pyrolysis gases contain mainly hydrocarbons and have an averaged LHV around 20 MJ/Nm3. ICP-AES analyses of pyrolysis products reveal that almost none of the metals present in MSW are distributed within the liquid fractions. © 2011 Elsevier B.V. All rights reserved. Source

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