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  • 1.
    Leijen, Sebastian
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Semi-kontinuerlig samrötning av ensilerat våtmarksgräs och matavfall: En studie av metan utbyte2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The worlds increasing need for energy and the desire to minimize the consequences of climate change have led to several environmental goals at both national and international levels. Many resources are spent on developing the current renewable energy sources and to find new alternatives. One of the renewable energy resources is biogas. Biogas is formed when organic matter is decomposed which forms carbon dioxide and energy rich methane gas.

     

    This master's thesis has focused on two areas, the first to examine methane production in a co- digestion process with silage of wetlands grass and food waste from Mosserud biogas plant. Mosserud is located a couple of kilometers west of Karlskoga city. Today the plant mainly uses food waste, manure and ley crops. The wetland grass originates from an area outside of Säffle called Brosjö. In 2010-2014 the Brosjö area was a part of an EU project that promotes bio diversity and threaten animal species, which . Due to this project the harvesting of grass has been made easier and has no use today, but could fit in an anaerobic digestion process.

     

    The second area was to compare the results with earlier reports on anaerobic digestion and the use of wetland grass. Neldorin (2015),vconducted a study of the substrate mix at Mosserud, whihc lays as a basis for biogas production from Mosserud today compared to the results of this study. The second report studied wetland grass as an additive in pellets. Where Henriksson (2016) had focus on energy consumptions during production of pellets when using wetland grass from Brosjö.

     

    The laboratory study was made at Karlstad University, the study was a semi continuous wet anaerobic process with mesophilic conditions. Feeding and

    withdrawal of gas was made once a day, using the same lab line up as Neldorin (2015) did. The experiment lasted 10 weeks and 2 different substrate mixtures were used; one with 30% grass 70% food waste and one with 15% grass 85% food waste. The result showed that digestion with 30 % grass mix was preferred. The specific methane production was 0.300 and 0.350 Nm3 / kg VS / day, which was less than those obtained from Mosserud at 0,352 Nm3 / kg VS / day. The total production of methane gas could be increased between 1.5 - 2.6% as there was access to more substrates.

     

    Wetland grass was better used for digestion than pelleting as it could increase the total methane production, while the pellets produced did not meet the requirements of strength, bulk density and fractional fineness. The problems associated with using grass in digestion are sludge formation in the reactor tank and process stability for a long time, when the pH value fell by the accumulation of VFA.

  • 2.
    Olofsson, Jonny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Sojaprotein, oxiderad majsstärkelse, vetestärkelse & ärtstärkelse som additiv i träpellets: Effekter på pelletsens kvalitet, CO2ekv utsläpp & energianvändning2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Currently, only 2.8% of total energy use in the world is renewable energy. As a climate target in 2020, the European Union has set a goal of increasing the renewable energy to 20%. Renewable energy includes biofuel such as pellets.

     

    Pellets use has already increased significantly and several large production units have been built in recent years. To achieve a competitive pellet, production must be improved in terms of quality, environmental impact, and electricity consumption. Adding additives can improve pellets strength, reduce CO2eq emissions and reduce energy consumption.

     

    The purpose is to investigate how different percentages of additive affect pellets to achieve a more sustainable and competitive biofuel.

     

    In the quality analysis where sustainability and hardness were investigated, oxidized corn starch showed the best result where sustainability increased from 94.8% to 97.86%. The hardness varied greatly from pellets to pellets from the same sample. Since the hardness varied so widely, it was impossible to say which sample who had the highest hardness. On the other hand, it is concluded that the oxidized cornstarch samples received higher hardness than the zero sample.

     

    In the environmental section, CO2equivalents for pellet production were investigated in Sweden, OECD member countries and non-OECD member countries in Europe. In Sweden and in OECD member countries, pellets production did not reduce the CO2eq emissions with any added additive. In non-OECD member countries, wheat starch was the best additive and reduced CO2eq emissions by 2.4%.

     

    The energy consumption in the pellet press was also analyzed and the results showed that all additives reduced energy consumption. The best additive in this study was wheat starch, which reduced electricity consumption by 3.9%.

  • 3.
    Pogosean, Ararat
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Framställning av syntetiska bio-drivmedel från förgasad biomassa: En studie i potentiell värmeintegration2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fossil fuels have since their discovery replaced biomass as the main source of energy. Especially in the transportation sector, fuels derived from fossil oil have been the dominant source of energy, mainly due to their advantages compared to biomass such as availability, price, energy density and easiness of use in an internal combustion engine. Unfortunately these fuels contain carbon atoms that no longer are part of the natural cycle and combustion leads to net addition of carbon dioxide to the atmosphere. Carbon dioxide has the largest anthropogenic impact on the accelerated greenhouse effect that the world is experiencing, which will lead to devastating climate changes. In this context it is necessary to instead produce fuel from a renewable source, which means a carbon neutral combustion, namely biomass. At the same time it is necessary to also take into account the type of biomass used, the production of biofuels should not compete with food production. Therefore it is important that “woody” biomass is being used as the raw material, which poses no competition.

    A promising way to convert biomass into fuels is with gasification where biomass is heated until a gas is obtained, mainly consisting of carbon monoxide, hydrogen, methane and various trace elements. This gas then undergoes purification and processing, where particles, tars, alkali metals and trace elements are purged until only a gas consisting of carbon monoxide and hydrogen remains, called syngas (synthesis gas). The syngas can then be converted into a variety of fuels such as petrol and methane.

    When the gas is being purified and processed large amounts of excess thermal energy are released. If it is a stand-alone plant, excess energy cannot be utilized, which leads to relatively low efficiencies. But if the plant is integrated with, for example, a pulp and paper mill, the excess energy can be utilized, thus resulting in higher overall efficiencies.

    This work presents a compilation of purification and processing methods. This compilation was used as the basis for the modelling of eight process solutions that were simulated in the flow-sheeting program CHEMCAD. The eight cases included in the study aim to produce gasoline, diesel, methanol and methane, all with purification at relatively low temperatures (cold gas cleaning) or at relative high temperatures (hot gas cleaning).

    Based on simulation results, a so-called Pinch analysis has been carried out where it is possible to graphically read off the potential for heat integration with a typical pulp and paper mill. Finally, overall assessments of the eight cases have been made based on different efficiency calculations.

    The results clearly show that the potential for process integration is great, with useful temperature levels, and amounts in up to almost 40 MW when the biomass input is 100 MWth.

    The efficiencies are defined in four different ways allowing for deeper interpretation and evaluation of the results, but require a certain amount of caution from the reader. However, it is evident from the results of efficiency calculations that overall efficiency of the process can be increased by 10's of percentage points if surplus heat is utilized. The results emphasize the importance of heat integration and simultaneously indicate the possibility of increased efficiency in production of biofuels. Which most likely also means a more economically sound alternative, which in turn increases the interest from investors in renewable fuels. Investments of this type are an absolute necessity for sustainable fuel consumption in the future.

  • 4.
    Sönefors, Adam
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Kylningens inverkan på pelletskvalitén: En studie om kylning av träpellets med olika kylningsmetoder2018Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [sv]

    Det blir allt viktigare med fler hållbara och miljövänliga lösningar för att kunna ta itu med dagens miljökris och för att kunna ersätta de fossila bränslena. Pelletseldning är en lösning som anses vara koldioxid neutralt och går att elda året runt. För att pelleten ska vara lätthanterlig och tålig så är de b.la. viktigt med en bra bulkdensitet och hållfasthet. Där spelar kylning av pellets roll och därför skall detta examensarbete undersöka hur olika kylningsmetoder påverkar pelletsen kvalité.

     

    Ett antal prover av pellets tillverkades på Karlstad universitetet med en pelletsmaskin under två olika labbsessioner. Tre av dessa prover kyldes sedan på olika effekt på en fläkt i en mindre kylanläggning. Två andra prover kyldes i en hink och utspridda i en stor låda/plåt. Dessa stod under natten och kyldes till omgivningstemperaturen. Efter att proverna hade kylts så gjordes olika kvalitétstester på varje kylt prov; bulkdensitet, hållfasthet, hårdhet, fukthalt och andel fabriksmul mättes. En analys av insamlad data gjordes, efter det så kunde en slutsats dras.

     

    En fältundersökning gjordes även för att utröna hur olika pelletsföretag går tillväga med deras kylningsprocess och hur tekniken på deras kylning ser ut.

     

    Den kylningsmetod från första sessionen som hade bäst resultat i alla kvalitétstester var pelletsen som kyldes naturligt och utspridda i en låda, med en bulkdensitet på 646 kg/m3 och en hållfasthet på 96,6% samt minimalt fabrikssmul. Pelletsen som kyldes på lägsta effekt på kylanläggningen visade också bra resultat på testerna. De mindre bra kylningsmetoderna var pellets som kyldes i hink under natten samt pellets som kyldes på maxeffekt på kylanläggningen. Från andra sessionen så fick pelletsen som kyldes med 30Hz bäst hållfasthet på 98,6%  men lägst bulkvikt på 693 kg/m3. Pelletsen som kyldes med max effekt fick sämre hållfasthet och lägst hårdhet. Högst bulkvikt på 737 kg/m3 fick det provet som var utspritt på en plåt och kyldes naturligt. Inget tydligt samband kunde ses mellan resultaten från de olika labsessionerna.

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