Browsing by Author "Paasikallio, Ville"

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    Bio-oil production via catalytic fast pyrolysis of woody biomass
    (Aalto University, 2016) Paasikallio, Ville; Lehto, Jani, Dr., VTT Technical Research Centre of Finland Ltd, Finland; Lehtonen, Juha, Dr., VTT Technical Research Centre of Finland Ltd, Finland; Biotekniikan ja kemian tekniikan laitos; Department of Biotechnology and Chemical Technology; Industrial Chemistry; Kemian tekniikan korkeakoulu; School of Chemical Technology; Seppälä, Jukka, Prof., Aalto University, Department of Biotechnology and Chemical Technology, Finland
    Fast pyrolysis of biomass is a thermochemical conversion process where solid biomass such as wood is thermally converted under a non-oxidative atmosphere at a temperature of approx-imately 500°C. The main product from this process is bio-oil, a highly oxygenated liquid with very challenging fuel properties. The quality of the bio-oil can be improved using a variety of catalytic processes. One such technology is catalytic fast pyrolysis (CFP), which integrates a catalytic vapor-phase upgrading step directly into a fast pyrolysis process itself. The overall purpose of this is to improve the quality of the bio-oil that is produced in the fast pyrolysis process. This, in turn, can facilitate easier utilization of the bio-oil in demanding applications such as upgrading to transportation fuels. CFP is most often carried out using acidic zeolite catalysts, which are capable of removing oxygen from the pyrolysis vapors in the form of carbon oxides and water. Because both carbon and hydrogen are lost together with the oxygen, the quality of bio-oil improves at the expense of the yield. Acidic catalysts and highly oxygenated pyrolysis vapors are a combination which results in rapid catalyst deactivation due to coke formation. In order to maintain an adequate level of catalyst activity, the catalyst must be regenerated on a frequent basis. From the perspective of continuous operation, this sets certain requirements on the reactor technology for CFP. The results of this thesis show that bubbling fluidized bed reactors, which are commonly used for research purposes and do not normally include the possibility of continuous catalyst addition and removal, have clear operational limitations for CFP. Such reactors can, nevertheless, be used for catalyst testing and parametric studies as long as the effect of short-term catalyst deactivation is taken into account. Circulating fluidized bed reactors with continuous catalyst regeneration provide a much more convenient technological platform for CFP. The effect of coke-induced reversible deactivation is effectively negated, and the focus can be shifted to process performance and catalyst long-term stability. The latter factor is considered to be one of the key questions for CFP. It was shown in this thesis that the combination of biomass-derived inorganic contaminants and severe reaction/regeneration conditions cause irreversible changes in the catalyst structure and properties, which in turn reflects in the quality of the bio-oil. The results of this thesis also highlight the diverse overall character of the CFP products. The partially upgraded bio-oil product is accompanied by a separate aqueous liquid with varying amounts of dissolved organics. Thus, efficient utilization of the CFP products would very likely entail more than one valorization approach.
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    Dieselin valmistaminen Fischer-Tropsch-prosessilla
    (2009) Paasikallio, Ville; Kurkijärvi, Antti; Kemian ja materiaalitieteiden tiedekunta; Linnekoski, Juha
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    Hydrogen production via reforming of pyrolysis oil aqueous fraction
    (2014-08-19) Azhari, Ajimufti; Paasikallio, Ville; Kemian tekniikan korkeakoulu; Lehtonen, Juha
    Increase in energy demands and the need of new and renewable energy sources pushes the development of biomass utilization. One of the new emerging interests is hydrogen production from pyrolysis oil aqueous fraction using catalytic steam reforming. Although it is known firstly as a source of valuable chemicals and sugars, hydrogen production via reforming is indicated to be the most cost-effective way for utilizing pyrolysis oil aqueous fraction. The literature review revealed that wide range of catalysts and process conditions have been tested and main challenges revolved around catalyst stability, feeding system and reactor design. Based on the stability issue, oxidative steam reforming and testing of different types and combinations of reforming catalysts was chosen as a topic of the experimental part master’s thesis. In the experimental part, oxidative steam reforming of pyrolysis oil aqueous fraction from condenser unit in fast pyrolysis of forest thinning was tested using three different catalysts and catalyst combination and four different oxygen concentrations —represented by different O/C ratios. The experiments were carried out in a fixed bed steel reactor with process conditions set up as reaction temperature of 650oC, atmospheric pressure and S/C of 3.84. It was found that combination of zirconia monolith as pre-reformer and commercial nickel catalyst (Reformax) to be the best catalyst combination that enhanced the stability of carbon-to-gas conversions and hydrogen production. With this combination, the carbon-to-gas conversions remained above 80% for 4 hours and hydrogen productions above 70% in any O/C ratio used. This catalyst combination also showed role in suppressing the rate of C2 formation side reactions. It was also found that increase of oxygen fed into in the system benefited to create more stable carbon-to-gas conversions and hydrogen production profiles. The observed main problem with the experiments was carbon coking at the top of the reactor as a result of feed depolymerisation and decomposition during the spraying process.
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    Improving pyrolysis oil quality with catalytic pyrolysis
    (2012) Paasikallio, Ville; Lindfors, Christian; Linnekoski, Juha; Kemian laitos; Kemian tekniikan korkeakoulu; School of Chemical Engineering; Lehtonen, Juha
    Fast pyrolysis is a thermochemical conversion process used for producing pyrolysis oil from solid biomass with yields of up to 75 wt-%. Due to its high oxygen content, pyrolysis oil has many adverse properties that severely limit its use as a liquid fuel. Catalytic pyrolysis with zeolite-type cracking catalysts can be used to remove oxygen in situ in the form of CO, CO2 and H2O through decarboxylation, decarboxylation and dehydration reactions. The intermediate oxygenate molecules formed in these reactions can then react further to form more useful products such as aromatic hydrocarbons. In this work, catalytic fast pyrolysis of spruce sawdust was carried out in a bubbling fluidized bed reactor using HZSM-5 catalysts. Two catalysts with Si/Al ratios of 40 and 140 were used. The catalyst with the Si/Al ratio of 140 was also used in experiments where the amount of the catalyst was increased to 1.5 and 2 times compared to the original amount. The use of catalysts decreased the yield of organic liquids and increased the yields of pyrolytic water and non-condensable gases (primarily CO). At most, the use of catalysts decreased the oxygen content of the organic fraction of pyrolysis oil to 30.6 wt-% (dry basis), which was a 6.0 wt-% decrease compared to the non-catalytic reference experiment. The catalysts were most effective in eliminating sugar-type compounds. Another significant change in the overall chemical composition of the liquid products was the increase in the amount of water. The overall concentration of carbonyl compounds also decreased, which should increase the stability of the liquid products.
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    Purification of bio-oil
    (2017-11-07) Räsänen, Jussi; Paasikallio, Ville; Kemian tekniikan korkeakoulu; Alopaeus, Ville
    The increasing concerns on climate change drives to discover new feedstock alternatives and pathway routes to produce transportation fuels from renewable and sustainable raw materials. Fast pyrolysis process enable the conversion of lignocellulosic biomass into aliquid product - bio-oil. Bio-oil can be upgraded into transportation fuels via hydroprocessing and/or catalytic cracking. The upgrading efficiency of bio-oil, however, decreases due to the deactivation of catalyst material and reactor blockings. Contaminants and solid particles that are present in the bio-oil are one of the factors for causing deactivation of catalyst material and reactor blockings. Bio-oil purification from contaminants and solid particles is therefore necessary process step to produce transportation fuels from bio-oil sustainably and efficiently. The aim of this thesis was to study experimentally the purification of bio-oil from contaminants and solid particles. Centrifugation, surface filtration, filtration with filter additives and ion exchange separation technique were the purification techniques that were applied in this thesis. Two different bio-oil liquids were used as a feed in the laboratory experiment. The solid and contaminant content of bio-oil feeds varied between 0.01 to 0.45 wt% and 183 to 3750 ppm. The purification process that consisted of filtration with filter additive E and cation exchange was evaluated as the most efficient purification method. The body feed proportion of 0.5 wt% was applied at 80 °C. With filter additive filtration, the solid and contaminant content could be reduced below to 0.09 wt% and 687.5 ppm. Secondly, with the cation exchange resin concentration of 3 and 5 wt%, the cation removal efficiency of 45 and 89.2 % and total contaminant concentrations of 132.7 and 263.2 ppm was achieved.