05. Harjoitustyöt ja kurssitutkielmat / Coursework and Term papers, Final projects

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Yliopistossa suoritettujen opintojen harjoitus- ja lopputöitä / Coursework, term papers and final projects completed at the university

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Browsing 05. Harjoitustyöt ja kurssitutkielmat / Coursework and Term papers, Final projects by Department "Biotekniikan ja kemian tekniikan laitos"

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    Alkaline pre-extraction of birch wood prior to alkaline pulping
    (2013) Costabel Cabrera, Luciana; Ruuttunen, Kyösti; Biotekniikan ja kemian tekniikan laitos; Kemian tekniikan korkeakoulu; School of Chemical Engineering; Sixta, Herbert
    The existing chemical pulp mills offer a unique starting point for the implementation of future multi-product biorefineries. For the pulp industry, the biorefining process may be envisaged as the removal and use of material that does not contribute to paper and cellulose products, particularly the material which is normally dissolved in the black liquor and combusted in the recovery boiler. In that sense, the recovery of dissolved hemicelluloses in a separate stage prior to pulping for the production of added-value products may potentially improve the overall economy of a chemical pulp mill. The alkaline extraction of hemicelluloses prior to alkaline pulping provides an additional possibility to isolate carbohydrates from wood in reasonably high yields, besides the currently widely investigated acid- and auto-catalyzed prehydrolysis. Furthermore, the use of aqueous sodium hydroxide solution in a pre-extraction process is compatible with kraft or soda-anthraquinone pulping processes, and particularly for the production of paper grade pulp, this process is more likely to preserve fibre strength properties than prehydrolysis followed by alkaline pulping. The objective of this work was the recovery of high molecular weight hemicelluloses, mainly xylan, through alkaline extraction. At the same time, the amount of co-extracted lignin was to be minimized. Birch wood chips were used for the optimization of the pre-extraction conditions. In addition to temperature and sodium hydroxide concentration, the effect of chip thickness was studied. The optimized extraction conditions were found to be NaOH concentration of 2.5 M at 95 °C. Lignin and carbohydrate mass balances were calculated for pre-extraction trials performed at these conditions. Approximately 6% of the original dry wood material was measured in the extracted liquor as polymeric xylan and 1% as co-extracted lignin. The selectively precipitated xylan revealed a weight average molecular weight (Mw) of 20 kDa as determined by size exclusion chromatography. For further purifying the extracted xylan, the diluted solution was concentrated by a factor of 8 by means of pressure-driven membrane filtration. This separation process allows the recovery of a large part of the sodium hydroxide in the permeate stream and makes a subsequent xylan precipitation via acidification more economical. The permeate stream containing the recovered sodium hydroxide may be recycled to the cooking liquor preparation. Preliminary tests confirmed that xylan can be isolated in higher purity when the pH is maintained at a higher level during the precipitation step since lignin remains more soluble under these conditions.
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    Catalytic wet oxidation of black liquor
    (2013) Viader Riera, Gerard; Melin, Kristian; Sarwar, Golam; Biotekniikan ja kemian tekniikan laitos; Kemian tekniikan korkeakoulu; School of Chemical Engineering; Koskinen, Jukka
    Aspects of wet air oxidation and catalytic wet air oxidation have been reviewed in this work paying special attention to the reaction mechanisms, kinetics and the industrial process. In the experimental section a set of heterogeneous catalysts have been tested in the wet oxidation of non-wood black liquor. The oxidation runs were performed batch wise in a laboratory-scale mechanically stirred slurry reactor for 1 h at a temperature of 170°C and total pressure of 12 bar. Pure oxygen was used as oxidant agent. Results showed that Fe/AC, AC and CuO promote the formation of acids, whereas CeO2 was found to be effective for the complete oxidation of black liquor. It was also observed that highly concentrated streams cause catalyst deactivation due to active sites blockage.
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    Desulfurization of heavy fuel oil for power generation
    (2013) Gamero Rodriguez, Maria del Carmen; Koskinen, Jukka; Sundell, Juha-Pekka; Biotekniikan ja kemian tekniikan laitos; Kemian tekniikan korkeakoulu; School of Chemical Engineering; Lehtonen, Juha
    Gasification is a technologically advanced, environmentally friendly and proven technology for disposing high sulphur heavy fuel oils by converting them into clean combustible gas products, avoiding corrosion problems and environmental emissions. Due to the high sulphur content of heavy fuel oil, it is essential to find efficient technologies to remove H2S from synthesis gas prior to its utilization within gas engines for power generation, since their absolute H2S limit is 500 ppm. This thesis intends to provide realistic solutions for clean power generation and simultaneously for the problems of heavy residues in refineries. For this purpose different approaches were adopted and presented. In the literature part, several technologies to remove H2S from synthesis gas were reviewed, such as absorption, adsorption and catalytic hydro treatment. In the experimental part a complete process of gasification, syngas purification by means of absorption and power generation was modeled and simulated with ASPEN plus. Moreover, the overall performance was studied and an economic study based on CAPEX/OPEX was performed in order to evaluate the feasibility of the process and provide reliable results.
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    Methanol steam reforming for polymeric electrolyte membrane fuel cells applications
    (2013) Vidal Vázquez, Francisco de Sáles; Lehtonen, Juha; Simell, Pekka; Biotekniikan ja kemian tekniikan laitos; Kemian tekniikan korkeakoulu; School of Chemical Engineering; Koskinen, Jukka
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    Simulation and study of asphaltene precipitation using flowbat
    (2009) Fontquerni Freixa, Jordi; Aittamaa, Juhani; Biotekniikan ja kemian tekniikan laitos; Teknillinen korkeakoulu; Helsinki University of Technology; Alopaeus, Ville
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    Thermal decomposition of sodium acid salts from black liquor
    (2013) Guxens Valero, Montserrat; Sarwar, Golam; Melin, Kristian; Biotekniikan ja kemian tekniikan laitos; Kemian tekniikan korkeakoulu; School of Chemical Engineering; Koskinen, Jukka
    Biofuels production seems the better alternative to fuels consumption realized from non-renewable sources. Black liquor obtained during the pulping is a good resource, because contain a large amount of organic matter. Black liquor can be pre-treated in a partial wet oxidation process to obtain carboxylic salts. These salts can be treated to produce biofuels, such as syngas and methane. This final project is a research of different ways to obtain carboxylic salts, for example from black liquor treatment. Subsequent conversion process of carboxylic acid salts is focus in thermal decomposition process and the kinetic solid reaction study, from an experimental thermo gravimetric curve. Results comparison with literature is done to validate the methods used in this study. Kinetic triplet has been further used to predict the residence time needed in a reactor to obtain 40% conversion of the sample at 450°C and 1 bar. Thermal decomposition process has been simulated in Aspen Plus to study the energy requirements and production in the process.