The boiler flue gas furnace exit temperature (FET) is a key operating parameter of coal fired steam boilers. From the design perspective, the FET is vital for materials selection and sizing of heat transfer surfaces. From an operating perspective, it is a major indicator of the rate of combustion and heat transfer that is occurring within the furnace. Downstream of the furnace, the FET has a significant impact on both the performance and reliability of the boiler heat exchangers, which ultimately impacts on both boiler efficiency and availability. Monitoring of the FET can advise operating and engineering corrective actions which will ultimately result in better efficiency, reliability and availability together with the associated economic benefits. Therefore, methods of determining FET are investigated. Two methods are focused on for this study, one indirect and one direct. The indirect method studied is a mass and energy balance method which begins with a global boiler mass and energy balance to calculate the major boiler flow rates of coal, air and flue gas which are difficult to measure online. These parameters are then used as inputs into a furnace or backpass mass and energy balance to calculate the furnace exit temperature. The method is applied to a case study, and is evaluated in terms of the measurement uncertainties which are propagated on the intermediate parameters calculated, as well as on the final calculated FET. The main conclusions are that this indirect method contains various uncertainties, due to parameters which have to be assumed such as (i) the distribution of ingress air (also called tramp air) in the different sections of the boiler and (ii) the estimation of the share of water evaporation heat transfer occurring in the water walls of the furnace part of the boiler. The method is however still useful and can be easily applied to any boiler layout and can be used as a reference tool to verify other measurements. The direct method studied is acoustic pyrometry. The work specifically focuses on the sources of error in determining the temperature from the measurement of the time of flight of sound, the impact of particle concentration on the speed of sound through a gas-particle mixture, and the temperature profile reconstruction from acoustic time of flight measurements. A limited set of physical testing was also carried out using one acoustic generator and receiver to take measurements on a real coal power plant. As part of this physical testing, the detection of time of flight from acoustic signals was explored. Already installed radiation pyrometers were also used as a reference for interpreting the acoustic measurements. The indications are that the acoustic pyrometer provides a more representative temperature measurement than the radiation pyrometers. The uncertainty of the acoustic measurement for the same case study as the indirect method was determined and compared with the calculated result. While many aspects still need to be researched further, this initial study and experimental testing produced very promising results for future application of acoustic pyrometry for better monitoring of the coal combustion processes in power plant boilers.

After the extension of the boiler 6 at Högdalenverket during 2010, there has been some problems in the form of increased carbon monoxide levels. There may be several explanations for this problem, which means that complete combustion doesent take place. There have also been problems with the ash-handling system and the sand returning systemt, this results in higher operating costs because it requires a higher consumption of inert material.The project was first divided into two phases, the first phase was to develop material and energy balances for the boiler but also introduce the parameters that we wanted to investigate further in order to possibly identify the causes of the problems that the boiler had. In the second phase experiments were going to be designed in consultation with the contact staff at Fortum to explore these parameters.During the project changes have been made in the project description, as it will require more time and more accurate planning to perform  the desired tests on the boiler. Three proposals on parameters that could be the cause of carbon monoxide problem was presented at the end of phase one and it was found that two of the proposals was not possible to carry out during the project because it would have affected economically and the availibility of the boilier.The third parameter, the bed quality effect on combustion experiment was designed in consultation with those responsible at Fortum.This experiment could also not be performed as there was some operational difficulties with the boiler during the project time. Instead, a description of the design for the experiment has been added to this project, which may at a later stage be used to investigate the bed quality impact on the carbon monoxide issues.Recent changes to the project description meant that purpose instead was to further develop the computational program created during the project's first phase and at the end of the project shall be submitted to the operators at Fortum. This calculation program takes into account the significant parameters that the boiler regulator is governed by today. The simulation program is developed using Microsoft Excel and is based on material and energy balances. This program can be used internally by Fortum to get an idea of ​​how the different mass flow rates would vary at different operating conditions and how the energy balance for the boiler would look like during the changes.When compared with materials and energy made by the boiler supplier revealed that the deviations are very small compared to what the program come up with and is caused mainly due to the assumptions made. These assumptions can be eliminated by performing experiments and collecting more data.The results gained by the calculation program has been compared with the results that was presented by the supplier during their boiler mapping, comparisons have been made regarding flue gas flows, fuel flows, combustion air flow, ash production and energy balances. It has apperad that the deviations are relatively small and the presented scheme provides a theoretical overall perspective of the boiler in line with reality.Although discussions have taken into consideration for the problem of elevated levels of carbon monoxide, and whether the measurement program can be developed further in the future. / Efter ombyggnationen av panna 6 vid Högdalenverket under år 2010, har det uppkommit en del problem i form av förhöjd kolmonoxid halt. Det kan finnas ett flertal förklaringar till problemet som innebär att fullständig förbränning inte sker. Det har även varit problem med askhanteringssystemet och sandåterföringen som inte fungerat som den ska, detta medför högre driftkostnader då det kräver en högre förbrukning av inertmaterial.   Projektet var indelat i två faser, där den första fasen var att ta fram material- och energibalanser på pannan men också presentera de parametrar som man ville undersöka vidare för att möjligen identifiera orsakerna till de problem som pannan haft.  I den andra fasen skulle experiment utformas i samråd med ansvariga från Fortum för att undersöka dessa parametrar. Under projektets gång har ändringar fått göras på projektbeskrivningen, då det krävs mer tid och noggrannare planering för att utföra test på pannan. Tre förslag på parametrar som kunde vara orsaken för CO problemen presenterades i slutet av fas ett och det konstaterades att två av förslagen inte gick att utföra under projektets gång på grund av både ekonomiska och driftrelaterade orsaker. Den tredje parametern bädd kvaliténs påverkan på förbränningen bestämdes i samråd med ansvariga i Fortum att utföras. Detta experiment kunde dock inte utföras då det uppstod vissa driftrelaterade svårigheter med pannan under projektets gång. Istället har en beskrivning av utförandet av experimentet lagts till detta projekt, som kan vid ett senare skede användas för att undersöka bädd kvaliténs påverkan på CO-halten. Nya ändringar av projektbeskrivningen innebar att syftet istället blev att vidareutveckla det beräkningsprogram som skapats under projektets första fas och som vid projektets slut ska överlämnas till de driftansvariga på Fortum. Detta beräkningsprogram tar hänsyn till de betydande parametrar som pannan regleras genom idag. Beräkningsprogrammet är framtaget med hjälp av Microsoft Excel och är grundat på material- och energibalanser. Detta program kan användas internt inom Fortum för att få en fingervisning på hur de olika massflödena skulle variera vid olika driftfall samt hur energibalansen för pannan då skulle se ut.   Vid jämförelse med material- och energibalans som gjorts av pannleverantören framgick det att avvikelserna är väldigt små jämfört med det vi framtagit, samt att det beror främst på de antaganden som gjorts. Dessa antaganden kan elimineras genom att utföra experiment och få in mer data. Resultatet som fåtts av beräkningsprogrammet har jämförts med det resultat pannleverantören fick vid sin pannkartering med hänsyn till rökgasflöde, bränsleflöden, förbränningsluft flöde, askproduktion och energibalanser. Det har framkommit att avvikelserna är relativt små och det framtagna programmet ger ett teoretiskt helhetsperspektiv av pannan som överensstämmer med verkligheten. Även diskussioner har förts till åtgärder för problemet med förhöjda halter av kolmonoxid, samt huruvida beräkningsprogrammet kan vidareutvecklas i framtiden.

Darbo tikslas – įvertinti biodujų gamybos energetinį efektyvumą keičiant proceso temperatūrą. Šio darbo tyrimo objektas yra biodujų gamybos technologinis procesas. Darbe įvertinti svarbiausi anaerobinio proceso veiksniai ir jų įtaka gamybos procesui. Remiantis matematiniu modeliu, sukurta biodujų jėgainės energinio efektyvumo įvertinimo metodika. Teoriniuose tyrimuose nustatytos etanolio gamybos šalutinių produktų (žlaugtų) ir daugiamečių žolių siloso (paprastųjų šunažolių) mišinio perdirbimo į biodujas energijos sąnaudos prie šešių skirtingų temperatūrų. Eksperimentinių tyrimų metu nustatyta biodujų energinė vertė reaktoriui dirbant skirtingomis sąlygomis. Proceso temperatūrų režimai termofilinėje terpėje buvo nagrinėjami nuo 52 °C iki 57 °C, išlaikant kitus parametrus pastovius (sausųjų medžiagų koncentracija, organinės apkrovos ir įkrovos pH). Didžiausia biodujų išeiga iš etanolio gamybos šalutinių produktų (žlaugtų) ir daugiamečių žolių siloso (paprastųjų šunažolių) mišinio buvo gauta reaktoriuje palaikant 52 oC, su vidutine biodujų išeiga 674,4 l kg-1•SOM-1, su energetinė verte 14,19 MJ kg-1•SOM-1. Mažiausia biodujų išeiga ir energetinė vertė buvo gauta reaktoriuje palaikant 57 oC ir atitinkamai 512,3 l kg-1•SOM-1 ir 10,18 MJ kg-1•SOM-1. Bendrosios energijos sąnaudos priklausomai nuo temperatūros svyravo nuo 1562,6 MJ∙t-1 iki 1665,3 MJ∙t-1. Energetinis efektyvumas kito nuo 3,2 iki 4,9. / The energy balance of biogas production from industrial wastes and energy plants has been investigated during this research. Conversion efficiency of digestion of industrial wastes and energy plants to biogas by using different temperatures in range from 52 to 57 oC has been evaluated. Ratio, composition and pre-treatment technologies of mixtures of industrial by-products and energy plants were analyzed. The influence of temperature on the performance of anaerobic digestion of industrial wastes and energy plants has been investigated. The variation of temperatures ranges from 52 oC to 57 oC while keeping other parameters constant such as total solid concentration, organic load and pH. The highest biogas yield from industrial wastes and energy plants was found at 52 oC with average yield of 674,4 l kg-1•VS-1 and energy value of 14,19 MJ kg-1•VS-1. By rising temperature to 57oC there was a rapid initial drop in biogas yield rate averaging yield 512,32 l kg-1•VS-1 and energy value of 10,18 MJ kg-1•VS-1.In addition, the temperature fluctuations resulted variations of biogas production significantly. Total energy input ranged from 1563 MJ∙t-1 at 52 oC to 1666 MJ∙t-1 at 57 oC. Energy conversion ratio varied from 3,2 to 4,9.

No description available.

Les missions spatiales habitées de longue durée nécessitent des systèmes de support-vie efficaces recyclant l’air, l’eau et la nourriture avec un apport extérieur minimum en matière et énergie. L’air et l’eau peuvent être recyclés par des méthodes purement physico-chimiques, tandis que la production de nourriture ne peut être faite sans la présence d’organismes vivants. Le projet Micro-Ecological Life Support System Alternative (MELiSSA, alternative de système de support-vie micro-écologique) de l’Agence Spatiale Européenne inclut des plantes supérieures cultivées dans une chambre close contrôlée, associée à d’autres compartiments microbiens. Le contrôle à long terme de la chambre de culture et du système de support-vie entier requiert des modèles prédictifs efficaces. Le bouclage du bilan massique et la prédiction de la réponse de la plante dans un environnement extraterrestre inhabituel mettent en avant l’importance de modèles mécanistes basés sur le principe des bilans de matière et d’énergie.Une étude bibliographique poussée a été réalisée afin de lister et analyser les modèles de croissance de plantes supérieures existants. De nombreux modèles existent, ils simulent la plupart des processus de la plante. Cependant aucun des modèles structurés globaux n’est suffisamment mécaniste ni équilibré en terme d’échange de masse pour une application dans un système de support-vie clos. Ainsi, une nouvelle structure est proposée afin de simuler tous les termes du bilan massique au niveau de la plante, en incluant les différentes échelles de l’étude : les processus généraux, l’échelle de l’organe et l’échelle de la molécule. Les résultats d’une première approche utilisant des lois physiques mécanistes simples pour les échanges de matière et d’énergie, une stoechiométrie unique pour la production de biomasse et quelques lois empiriques pour la prédiction des paramètres architecturaux sont illustrés et comparés avec des résultats expérimentaux obtenus dans un environnement contrôlé. Une analyse mathématique du modèle est réalisée et tous ces résultats sont discutés afin de proposer les prochaines étapes de développement. Ceci est décrit en détail pour l’inclusion de modèles de processus plus complexes dans les futures versions du modèle ; les expériences qui devraient être réalisées ainsi que les mesures nécessaires sont proposées. Ceci conduit à la description d’une nouvelle conception de chambre de culture expérimentale. / For long-term manned space missions, it is necessary to develop efficient life support systems recycling air, water and food with a minimum supply of matter and energy. Air and water can be recycled from purely physico-chemical systems; however food requires se presence of living organisms. The Micro-Ecological Life Support System Alternative (MELiSSA) project of the European Space Agency includes higher plants grown in a closed and controlled chamber associated with other microbial compartments. The long-term control of the growth chamber and entire life support system requires efficient predictive models. The mass balance closure and the prediction in uncommon extraterrestrial environments highlight the importance of mechanistic models based on the mass and energy balances principles.An extensive bibliographic study has been performed in order to list and analyse the existing models of higher plant growth. Many models already exist, simulating most of the plant processes. However none of the global, structured models is sufficiently mechanistic and balanced in terms of matter exchange for an application in closed life support systems. Then a new structure is proposed in order to simulate all the terms of the mass balance at the plant level, including the different scales of study: general processes, organ scale and molecular scale. The results of the first approach using simple mechanistic physical laws for mass and energy exchange, a unique stoichiometry for biomass production and few empirical laws for the prediction of architectural parameters are illustrated and compared with experimental results obtained in a controlled environment. A mathematical analysis of the model is performed and all these results are discussed in order to propose further developments. This is described in detail for the implementation of more complex models of processes in the future model versions; the experiments that should be performed including the main measurements are proposed. This leads to the description of a new design of experimental growth chamber.

Face au changement climatique global, il est de plus en plus important de prêter attention à la performance thermique-hydro-mécanique des constructions géotechniques sous l'effet des conditions atmosphériques. L'objectif principal de cette étude est d'étudier le comportement hydro-thermique des sols soumis au effets du changement climatique par la modélisation numérique.Un modèle hydro-thermique couplé est tout d'abord développé pour décrire le comportement du sol hydro-thermique. La théorie utilisée pour décrire l'interaction sol-atmosphère est présentée sous forme des bilans de masse et d'énergie. Ensuite, une approche numérique pour analyser le comportement hydro-thermique du sol est proposée en combinant le modèle hydro-thermique couplé avec un modèle d'interaction sol-atmosphère. La validation de cette approche est réalisée par la comparaison entre les résultats numériques obtenus en utilisant le code FreeFem++ et les données des essais de la colonne de séchage qui sont trouvées dans la littérature. Cette approche est d'abord utilisée pour la modélisation numérique des essais à la chambre environnementale, réalisés par Song en 2014. Des résultats de simulation satisfaisants sont obtenus en termes de variations de la température et de la teneur en eau volumétrique du sol. Ensuite, cette approche est appliquée à deux remblais, à Héricourt et à Rouen. Pour le remblai d’Héricourt, une étude numérique a été menée pour une durée de 20 jours. La bonne concordance obtenue entre les résultats de simulation et les mesures montre que l'approche proposée est pertinente pour l'analyse du comportement hydro-thermique du sol dans le cas de remblais bidimensionnels. Elle prouve également que les conditions aux limites et les paramètres du sol adoptés sont appropriés. Dans le cas du remblai de Rouen, deux périodes différentes, 187 jours et 387 jours, sont prises en considération. On vérifie également la bonne performance de l'approche proposée pour estimer le comportement hydro-thermique du remblai sous l'effet du climat. La comparaison entre les calculs et les mesures révèle également l'importance d'adopter correctement les conditions aux limites thermiques et hydrauliques ainsi que les paramètres du sol. De plus, à partir des simulations numériques, plusieurs suggestions sont faites pour collecter des données d'entrée dans l'application de cette approche pour prédire les variations de la température et de la teneur en eau du sol à plus long terme / Facing the global climate change, it is more and more important to pay attention to the thermal-hydro-mechanical performance of geotechnical constructions under the effect of atmospheric conditions. The main objective of this study is to investigate the hydro-thermal behavior of soil subjected to climate change through numerical modelling.A coupled hydro-thermal model is developed for describing the coupled hydro-thermal soil behavior. The soil-atmosphere interaction is studied through the mass and energy balances. Afterwards, a numerical approach to estimate soil hydro-thermal behavior by integrating the coupled hydro-thermal model with a soil-atmosphere interaction model is proposed. The validation of this approach is performed through the comparison between the numerical results using FreeFem++ code and the experimental data available from column drying tests reported in literature. This approach is firstly used for the numerical modelling of the environmental chamber tests carried out by Song in 2014. Satisfactory simulation results are obtained in terms of variations of soil temperature and soil volumetric water content. Afterwards, this approach is further applied to two cases of embankments, in Héricourt and in Rouen respectively. For Héricourt embankment, a numerical investigation was conducted for 20 days, and a good agreement between simulation results and filed measurements is obtained, showing that the proposed approach is suitable for analyzing the soil hydro-thermal behavior in the case of two-dimensional embankments. It proves also that the boundary conditions and the soil parameters adopted are appropriate. In the case of Rouen embankment, two different periods, 187 days and 387 days, are considered. The good performance of the proposed approach in estimating the embankment hydro-thermal behavior under the climate effect is also verified. The comparison between calculations and measurements also reveals the importance of appropriately adopting the thermal and hydraulic boundary conditions as well as the soil parameters. Based on the numerical simulations, several suggestions are made in terms of collection of input data for the application of this approach to predict soil temperature and volumetric water content variations in longer term