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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Process integration to increase woody biomass utilization for energy purposes

Mesfun, Sennai January 2016 (has links)
Woody biomass is an abundant renewable energy resource in Sweden, and the Swedish government has been promoting research and development programs for the exploitation of this resource as a mean to meet the targets on the reduction of the carbon dioxide emissions from the industrial, energy and transportation sectors. This thesis aims at expanding the knowledge on the efficient utilization of the available woody biomass, so that a larger amount of this renewable resource can be used for energy purposes. The thesis presents a collection of studies following the main two policies that have been identified for the reduction of carbon dioxide emission, i.e. the implementation of measures improving energy conservation and efficiency and a deep decarbonization of the energy sector. Process integration and optimization techniques are applied to forest industry sites in order to improve the resource and energy efficiency, the benefits of the integrated design configurations being evaluated by both technical and economic analyses. The integration of woody biomass with intermittent renewable energy sources is also studied in order to enable a large share of non-fossil sources in the energy mix.The results of the investigations show a significant potential for improving biomass resource utilization in the forest industry sites strictly from the energetic point of view. Optimizing the process integration in sites including Kraft pulp and paper mills and/or sawmills and a dedicated common CHP system can lead to a much greater power generation for the same input biomass and for the same production volume, or to large amounts of excess heat to be used in nearby processes or district heating, or even to the re-routing of part of the input biomass to other conversion processes (e.g. lignin separation and hemicellulose fermentation to produce biofuels). The operational profit of the site is consequently increased, but, when the investment costs are considered, some form of subsidies to the “green” byproducts are usually still required to make the integrated design configurations economically viable. The integration of woody biomass with intermittent renewable energy sources can result in an increased efficiency of hybrid power generation plants (e.g. with concentrated solar thermal collectors), and on a large scale it could facilitate the decarbonization of the energy sector with the fundamental contribution from power-to-X technologies in order to produce chemical fuels from the excess intermittent electricity. These technologies would be clearly incentivized by a carbon tax, but the benefit deriving from the large volumes of captured CO2 that are required for the synthesis of chemical fuels through co-electrolysis should also be taken into account. Keywords: Forest industry, process integration, pinch analysis, HEATSEP method, optimization, CHP system, techno-economic, biorefinery, intermittent renewables. / <p>Godkänd; 2016; 20160412 (senmes); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Sennai Mesfun Ämne: Energiteknik /Energy Engineering Avhandling: Process Integration to Increase Woody Biomass Utilization for Energy Purposes Opponent: Associate professor Francesco Fantozzi, Department of Engineering &amp; Biomass Research Center, University of Perugia, Perugia, Italien. Ordförande: Professor Andrea Toffolo, Avd för energivetenskap, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå. Tid: Torsdag 9 juni, 2016 kl 14.00 Plats: E632, Luleå tekniska universitet</p>
72

Open absorption system for drying of moist air

Westerlund, Lars January 1995 (has links)
Godkänd; 1995; 20070313 (ysko)
73

CO2 separation with ionic liquids - from properties to process simulation

Xie, Yujiao January 2016 (has links)
No description available.
74

Experiments and simulations of lean methane combustion

Lindberg, Jenny January 2004 (has links)
Computational fluid dynamics of methane combustion using chemical kinetics for description of the chemistry is studied. Linear least squares data fit to measured concentrations and temperatures is used to modify reaction rate parameters in the Arrhenius rate equation for combustion of methane. The modification of reaction rate parameters influences the result of CFD-simulations to predict combustion at experimental conditions where the Fluent rate equation failed. This first test show promising results but to further develop a global reaction model for combustion of methane and more complex fuels, a more extensive experimental study is required.The reaction rate for combustion of methane is rapid making ordinary sampling techniques for measuring to crude to collect sufficient amount of data for modification. Numerical simulation of fast chemistry using the Arrhenius theory often suffer from convergence difficulties as a result of the stiffness in the chemistry formulation. An alternative method for assessing the space discretization error is proposed. Richardson extrapolation is the most common model used for assessment of solution accuracy but the rigidity of the method allow little variation in the results. For engineering purposes qualitative methods can be sufficient for error assessment. The space discretization error of a two-dimensional axisymmetric simulation of combustion of methane in turbulent flow is studied. Profiles of temperature and carbon dioxide concentration is investigated and a second order polynomial fit is compared to the Richardson extrapolation. The profiles indicate grid independency of the solution but the Richardson method do not. The second order polynomial fit gives a better goodness of fit than obtained using Richardson, and by studying the first and second order term of the solution an estimation of the reaction order can be obtained and used to evaluate the accuracy of solution where the rigidity of the Richardson method provide unrealistic results. / Godkänd; 2004; 20070131 (ysko)
75

Övervakning av elproduktion i ö-nät

Hedin, Tobias January 2017 (has links)
No description available.
76

Biooljeprojekt för Umeå Energi AB

Olsson, Björn January 2012 (has links)
No description available.
77

NOx-reducerande åtgärder vid låg last av en fastbränslepanna med ureabaserat SNCR-system : Inverkan av körsätt och praktiska åtgärder / Nox-recducing measures at low steam production by a solid fuel boiler with urea-based SNCR-system : Effects of operation and practical measures

Larsson, Albin January 2017 (has links)
SCA Obbola AB is a kraft pulp mill that produces and sells packaging paper. The steam demand is covered by a recovery boiler and a solid fuel boiler (consists of two parallel solid fuel furnaces and a boiler). Adjustments in steam production are foremost made by the solid fuel boiler. Previously made energy-reducing measures at the mill has lowered the steam demand which forces the solid fuel boiler to low steam production. The solid fuel boiler produces over 25 GWH/year and is therefor bound by the Swedish nitrous oxide charge, but is also restricted to a monthly mean value of 70 mg/MJ. This mean value was exceeded in July 2016, which is thought to be a result of forced limitation in steam production. NOx emissions are reduced secondarily by an urea-based SNCR-system where its efficiency depends on several parameters, foremost sufficiently high flue gas temperatures. This work has identified parameters that effects foremost hydrogen-based combustion emission from the solid fuel boiler. This was achieved by evaluating historical data and by conducting tests during operation of the solid fuel boiler, which was planned and evaluated using a software called MODDE. Emission reducing measures and recommended ways to operate the boiler was then presented from the collected data. Practical measures including down-winding supply machinery of secondary air and replacement of urea injection showed no tendencies in reducing NOx emissions. However, complete shut down of one the furnaces produced at least 100 °C higher flue gas temperatures produced from the active furnace. Low NOx emissions was noted when secondary air was supplied from machinery with original speed. therefor, during stretched periods with low steam production, it's recommended that: Only one furnace should be active as steam producer, urea should be injected at its original placement in the flue gas chamber close the furnace and that secondary air should be supplied by machinery with original speed. Comparison test made in this work showed that this way of operating the solid fuel boiler could reduce NOx emissions with 45 % compared to mean NOx emissions at low steam production in July 2016.
78

Energieffektivisering av Saltsjöbaden Grand Hotell / Energy efficiency of Saltsjöbaden Grand Hotel

Alm, Tobias January 2017 (has links)
In a hotel building there are many processes which consume energy, such as lightning and drive fan motor in the ventilation system. These processes needs supplied with electricity. The building is a big consumer of heat. The heating system is supplied with heat pumps and oil. The consumption of electricity is about 1700 MWh and 350 MWh of oil. This thesis affects an energy saving investigation for a hotel and the purpose is to find measures to reduce the energy consumption for this building. The method for the investigation consisted of three steps. First step was to establish how much energy the building consumes today. Second step was to find measures which could be implemented and the third was to calculate the energy saving potential for each measure. If all investigated measures will be implemented the Hotel could save up to 40 % energy. If only the economical and easy measures would be implemented the hotel could save 30 % energy. The easiest measure was to change some parameters in the control system so the oil burners did not go at all times. With that change and a change in the control system for ventilation to reduce the hours the ventilation are on gave reduced energy consumption with 20 %. The economical investments were converting one of the oil burners to an extra heat pump and to change all old lighting to a new LED-Lighting.
79

Miljövärdering av energianvändning : Utvärdering av Karlstads kommuns kravformulering vid nybyggnation

Lindgren, Carl January 2013 (has links)
No description available.
80

Solcellers påverkan på landsbygdsnät

Thomas, Lisa January 2017 (has links)
Elnätets utformning står mitt i en stor förändring i och med decentraliseringen där allt fler upptäcker fördelarna med att producera egen el. Antalet nätanslutna solceller ökar och detta förväntas även gälla fortsättningsvis. Om solcellsanläggningar som nätansluts har hög effekt eller om elnätet är svagt kan förstärkande åtgärder vara nödvändiga. Detta projekt syftade till att utreda vilka problem solceller kan orsaka på svaga delar av nätet samt åtgärder för att minska problematiken. Projektet klargör även vad som bör beaktas vid dimensionering av elnät nät solceller ansluts. För att uppnå syftet inleddes projektet med informationsletande och producerande av en litteraturrapport. Därefter dimensionerades en framtida solcellsanläggning och nätet kring en befintlig anläggning utvärderades. Dimensioneringen och utvärderingen utfördes med hjälp av simuleringar i dpPower. Vid utvärderingen av den befintliga anläggningen genomfördes även en analys av elkvalitetsmätningar samt mätning av förimpedans på två olika lågspänningsnät. Den ekonomiska aspekten analyserades också i form av jämförelse av effektförluster i olika kablar. Nätet kring den framtida solcellsanläggningen undersöktes med avseende på spänningsändringar vid inkoppling av solcellsanläggningen och långsamma spänningsändringar. Resultatet från simuleringar visar att en anläggning på 21 kW kan anslutas till nätet utan behov av förstärkning. Enligt grovuppskattningskurvor för nödvändig nätstyrka vid anslutning av mikroproduktion som finns tillgängliga i handboken MIKRO blir resultatet 23 kW. Utvärderingen av nätet kring den befintliga solcellsanläggningen innefattade undersökning av spänningsvariationer, mätning och beräkning av förimpedans samt analys av elkvalitetsmätningar. Resultatet visar att den omdimensionering som utfördes i samband med att anläggningen nätanslöts var nödvändig och att nätet förmodligen kommer behöva förstärkas ytterligare med en större transformator om fler solcellsanläggningar ansluts i framtiden. Elkvalitetsmätningarna visar på höga flimmernivåer men det kan dock inte fastställas om dessa härrör från solcellsanläggningen. Genom mätning och beräkning av förimpedans drogs slutsatsen att mätinstrumentet påverkas vid mätning i närheten av en solcellsanläggning. De uppmätta värdena i närheten av solcellsanläggningen stämmer inte med de simulerade och beräknade värdena. Nyare versioner av mätinstrumentet finns tillgängliga hos leverantören och bör testas på samma nät för att se om mätvärdena stämmer bättre. Vid beräkning av effektförluster jämfördes olika kabelalternativ. Resultatet visar att det ofta lönar sig ekonomiskt att välja en grövre kabel med högre inköpspris och lägre förluster per meter kabel än tvärtom. De minskade förlustkostnaderna mellan en grövre och en klenare kabel är alltså större än skillnaden i inköpspris under kablarnas livslängd. Förutom de slutsatser för de specifika anläggningarna som projektet utmynnade i drogs även några mer generella. De vanligaste problemen som uppstår vid anslutning av solceller på nätets svaga delar är elkvalitetsproblem, oftast i form av spänningsvariationer. För att minska problematiken kan nätet behöva förstärkas, exempelvis i form av kabeldimensionering. Då bör spänningsändringar vid in- och urkoppling av solcellsanläggningen, långsamma spänningsändringar, effektförluster och möjlig utbyggnation av området beaktas.

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