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)

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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.

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.

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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.

A long term large-scale power outage would have a big impact on the society, not least for the elderly and sick people. The Swedish hospitals are well prepared for a power outage. How the municipal healthcare chain would cope with a large-scale power outage is not as well investigated. The purpose with this report is to increase the knowledge about what consequences a power outage would cause at the elderly care homes and how they could prepare for a scenario like that. The goal is to produce a report to ease the planning of emergency power solutions to the elderly care homes. To re-establish the power supply in case of a power outage the most common solution today is a diesel generator. An elderly care home was chosen as a reference to be able to calculate how big efficiency that is needed to supply necessary equipment with enough power. The result showed that the diesel generator need to be able to deliver 640 kVA. A model of the elderly care home was built in the simulation software IDA ICE. A simulation was made to decide how fast the temperature inside the building is sinking in case of an interruption in the district heating system. According to the result the temperature inside the building would be 11 ºC after 48 hours with an outside temperature at almost – 20 ºC. During a day with high temperatures can the inside temperature rise to 29 ºC. A power outage could cause big problems for the elderly care homes if there are no access of diesel generators. A diesel generator which would supply an elderly care home with electricity will consume a big amount of diesel. To facilitate the distribution of diesel in case of an emergency is it important to establish a plan for how much diesel that would be consumed over a day and how to secure the delivery to the most important places.  If the power outage occurs during a period with unusually hot or cold weather the vulnerability increases because the elderly people appear to be more sensitive of overheating or hypothermia. To know which buildings that would be prioritized in case of an interruption in the district heating system ore cooling system, would it be an advantage to document the buildings time constants.

There is a steadily growing awareness for environmental issues caused by the increased energy use, mainly in the industrial world. The use of fossil fuels has reached the point where it can not be looked at as an endless source, the resources are decreasing at a pace where alternative energy sources will be a necessity for this and future generations. Global warming, due to increased concentration of greenhouse gases in the atmosphere, has become one of the most important issues on the political agenda at all levels. A widespread opinion is that energy conservation technologies are needed and a shift towards renewable energy sources is required to attain a sustainable development of our society and a progress in the developing countries. This thesis is focusing on two different energy conservation technologies in different applications. The open absorption system, a modification of an absorption heat pump is a promising technique in moist air processes, recovering the latent heat in the air and decreasing the total heat demand. The technology has been tested in two full scale pilot plants at a sawmill operating four timber dryers and another unit installed at an indoor swimming pool. The technique has had positive outcomes in both operational energy conservation respects. It has been shown that the energy demand was decreased considerably in both applications. The investment cost has proved to be relatively high, but optimization of operational parameters shows a potential to decrease the initial investment and make the technology more competitive. Pressurized entrained-flow high temperature black liquor gasification (PEHT- BLG), developed by Chemrec AB, is another novel technique presented in this thesis. Black liquor is an important by-product in the papermaking process. Chemicals and energy is recovered in the conventional recovery boiler where superheated steam is produced to generate electricity and process heat. The cooking chemicals are recovered from the smelt in the bottom of the boiler in a separate recovery cycle. By introducing PEHT-BLG, a synthesis gas is obtained that can be used to generate electricity or be reformed into alternative automotive fuels. A demonstration plant, constructed by Chemrec AB, has been running periodically since late 2005. The plant is located at the Kappa Smurfit mill in conjunction with the Energy Technology Centre in Piteå, Sweden. In this thesis CFD models of the quench and counter current condenser have been performed and presented. The long term objectives with the CFD models are to create a tool that can be an aid in future scale-ups and for optimisation purposes. Since PEHT-BLG enhances the flexibility of the black liquor recovery cycle it is a promising alternative for future industrial commercialization if the remaining issues can be overcome. / Godkänd; 2007; 20070511 (ysko)

Short term water heat storage's have been introduced in many district heating systems. The main reason for this is the possibilities opened by the storage for optimization of the generation of heat and electricity in combined heat and power plants. The basic task for the storage is then to bridge the timevise gap between the heat demand and supply of heat from a cogeneration plant. Water heat storage's can also be useful in district heating systems supplied with industrial waste heat. The water volume in the storage must be stratified to avoid degradation of the quality of the heat that has been charged. Experimental studies of phenomena that influence the stratification and cause a degradation of the quality has been made in model storage's of different sizes The studies include extensive temperature measurements and velocity measurements with different techniques. Laser Doppler Anemometry was used to measure the vertical velocities in the boundary layer at the outer walls. The gradient zone was found to have a strong impact on the velocity field. The maximum velocity in the boundary layer was increasing due to available height up to a certain level where it remained constant. Particle Image Velocimetry Technique were used for measuring the two dimensional velocity field in seeded water in a plane illuminated by a laser. These measurements showed that large scaled convection cells appeared both above and below the gradient zone. The exchange of water between the boundary layer and the core was also shown in these experiments. A video based PIV-technique was developed where a complete charging experiment could be recorded on a video tape. The pictures were analysed in an image processing program which made it possible to evaluate the whole velocity field. On basis of simulations for a case study representing the district heating system in Piteå it was found that heat quality degradation is not essential for the optimization of the storage volume. The different phenomena that influence the quality degradation are important however for optimizing the shape of a storage of a given size. The results from the measurements in the model heat storage's are useful mainly for validation of computer models for numerical prediction of velocity and temperature fields and as a basis for planning of experiments in larger storage's of commercial size. It was therefore decided to include in the study an evaluation of the importance of heat quality degradation for sizing of short term water heat storage's. / Godkänd; 1993; 20070313 (ysko)