Laminar entrained flow reactor (LEFR) was used to determine the effect of temperature and residence time on the distribution of carbon, sulfur and nitrogen between gaseous and condensed phase products from low temperature pyrolysis of kraft black liquor. The operating furnace temperatures were between 400��C-600��C where the effect of condensable organic and organic sulfur compounds may be important. The residence times ranged from 0.3 to 2.0 seconds. In the evolution of carbon as gases, an oxidizer was used to convert all oxidizable components in LEFR effluent gas to carbon dioxide which was detected by an infrared carbon dioxide meter. With this, measurement of total carbon in the gas phase, the fine particles, and the char residue were made. The carbon yield in the gas phase increased as residence time increased. The higher the temperature, the higher the carbon yield as gases phase at each residence time. The carbon yield in the fine particles differed very little with temperature at residence time below 1.1 seconds. At higher temperature, the carbon yield in the fine particles is about the same at 500��C and 600��C, but lower at 400��C. The carbon yield in the char residue decreased as residence time increased. The carbon yield in the char residue at 500��C and residence time above 1.1 seconds was a little lower than at temperature 600��C, due to an apparent loss of char at 500��C. The char yield at 500��C was lower than expected based on the 400��C and 600��C data because of accumulation of larger, more highly swollen char particles at the tip of collector at this temperature. The average of the sum of carbon recovered as char residue, gases, and fine particles was 96.2% at 600��C, 88.1% at 500��C, and 95.7% at 400��C. The main reason for the poorer carbon recovery at 500��C was the loss of char particles which accumulated on the tip of the collector. When the char yield at 500��C is increased so that the carbon balance closed to 96%, the char yield, carbon yield, and sulfur yield at 500��C fell between the values at 400��C and 600��C. The sulfur yield in the char residue decreased as residence time increased. The higher the temperature, the lower the sulfur yield in the char residue. The nitrogen yield in the char residue also decreased as residence time increased. / Graduation date: 1997

Thesis (M.S.)--Brigham Young University. Dept. of Chemical Engineering, 2006. / Includes bibliographical references (p. 75-78).

Catalytic combustion provides us an efficient approach for the utilization and mitigation of methane, the major component of natural gas as well as an important greenhouse gas in global warming. From the research of catalytic combustion of methane, better understandings as well as solutions to the current methane-related problems can be obtained. This study investigates lean methane combustion on palladium-based catalysts. Catalysts activities were tested through ignition and extinction experiments. Several pretreatments and their influence were studied. Instrumental neutron activation analysis (INAA) and x-ray diffraction (XRD) were used as characterization tools for the catalysts. It was found that after being reduced, catalysts had stable and excellent abilities for methane conversion. However, these abilities were strongly compromised by additional water in the feeds. XRD results, combined with other testing results, implied that reduction produced the most active samples, while INAA revealed the real Pd concentrations of these catalysts. / Chemical Engineering

The recent pollution norms have brought a strong emphasis on the reduction of diesel engine emissions. Low temperature combustion technology such as premixed compression ignition (PCI) has the capability to significantly and simultaneously reduce nitric oxides (NOx) and particulate matter (PM), thus meeting these specific pollution norms. There has been, however, observed loss in fuel conversion efficiency in some cases. This study analyzes how energy transfer and brake fuel conversion efficiency alter with (or are affected by) injection timings and exhaust gas recirculation (EGR) rate. The study is conducted for PCI combustion for four injection timings of 9°, 12°, 15° and 18° before top dead center (BTDC) and for four exhaust gas recirculation (EGR) rates of 39%, 40%, 41% and 42%. The data is collected from the experimental apparatus located in General Motors Collaborative Research Laboratory at the University of Michigan. The heat release is calculated to obtain various in-cylinder energy transfers. The brake fuel conversion efficiency decreases with an increase in EGR. The decrease in the brake fuel conversion efficiency is due to the decrease in work output. This decrease is due to an increase in the pumping work and an increase in friction and decrease in gross indicated work. The decrease in the combustion efficiency is because of the increased formation of unburnt products due to increased ignition delay caused by the application of EGR and decreasing air-fuel (A/F) ratio. A definite trend is not obtained for the contribution of heat transfer to the total energy distribution. However the total heat transfer decreases with retardation of injection timing because of decreasing combustion temperature. As the injection timing is retarded, the brake fuel conversion efficiency is found to decrease. This decrease is because of a decrease in net work output. This is because the time available for utilization of the energy released is less because of late combustion. The total heat transfer decreases with retardation of injection timing because of decreasing combustion temperature. The contribution of heat transfer to the total energy distribution decreases with increase in EGR.

Dans la chaîne de fabrication des produits plats sidérurgiques, les brames sont des produits semi-finis sortant de la coulée continue, se présentant sous la forme de parallélépipèdes d'acier de 150 à 320 mm d'épaisseur qui devront passer dans le laminoir à chaud afin de réduire leur épaisseur à quelques millimètres pour être enfin enroulées en bobines de tôle. Pour permettre les importantes déformations du laminage, les brames doivent entrer dans le laminoir à une température comprise entre 800 et 1200°C; elles sont amenées à cette température en traversant un four de réchauffage où leurs faces supérieure et inférieure sont chauffées par des brûleurs de différents types, parmi lesquels figurent des brûleurs à longueur de flamme réglable, qui doivent permettre une variation, en cours de fonctionnement, de la longueur de la flamme générée par le brûleur afin d'adapter le profil de transfert de chaleur aux caractéristiques géométriques du produit à réchauffer. Ce travail a permis de caractériser le fonctionnement et les performances d'un tel brûleur, en particulier de déterminer la réglabilité effective de la longueur de flamme en fonction des conditions opératoires, ainsi que d'établir l'utilité de la modulation de flamme pour le procédé de chauffage en mesurant les effets de cette variation sur le profil de flux de chaleur transmis à la charge. Les conséquences de ces modifications sur la stabilité de la combustion et sur les quantités de polluants émis, en l'occurrence sur les émissions d'oxydes d'azote (NOx), ont également été examinées. Les performances du brûleur à longueur de flamme variable ont été étudiées par le biais de mesures réalisées sur une unité pilote à échelle réduite, conçue et réalisée au cours de ce travail. La détermination de la longueur de flamme a été réalisée par la mesure de l'émission de chimiluminescence du radical $OH$ tandis que la mesure du profil de flux radiatif incident sur la charge a mis en évidence que les transferts de chaleur au sein du four n'étaient que faiblement modifiés par les variations de longueur de la flamme. Les résultats expérimentaux ont également montré que la forme de la flamme n'influençait pas de manière significative le niveau d'émissions de NOx à la sortie du four. Cette approche a été complétée par une démarche de simulation numérique détaillée de l'équipement à l'aide d'un code commercial de CFD (pour Computational Fluid Dynamics) permettant de résoudre les équations différentielles de l'aéro-thermochimie (écoulement, turbulence, combustion et transfert de chaleur) dans le four. La comparaison des données numériques et expérimentales a permis de valider les résultats de simulation et d'établir leur sensibilité aux hypothèses des modèles utilisés. Elle a montré que la prédiction de la forme de la flamme était principalement conditionnée par les paramètres cinétiques du modèle de combustion plutôt que par le choix des modèles de turbulence et de rayonnement; elle a en outre établi que les niveaux d'émissions d'oxydes d'azote de l'ensemble des flammes modélisées ne pouvaient être calculés correctement par des modèles simples de combustion et de production de NOx. Ce travail s'inscrit dans le contexte de recherches réalisées en collaboration avec l'Agence Internationale de l'Energie, portant sur l'étude des phénomènes liés à la combustion du gaz naturel dans des brûleurs alimentés en air préchauffé; il a bénéficié du soutien financier de la Région Wallonne pour l'acquisition des outils expérimentaux et numériques utilisés au cours de cette étude.

High temperature filtration in combustion and gasification processes is a highly interdisciplinary field. Thus, particle technology in general has to be supported by elements of physics, chemistry, thermodynamics and heat and mass transfer processes. This topic can be addressed in many ways, phenomenological, based on the up stream processes (i.e. dust/aerosol formation and characterisation) or apparatus oriented. The efficiency of the thermochemical conversion process and the subsequent emission control are major important areas in the development of environmentally sound and sustainable technology. Both are highly important for combustion and gasification plant design, operation and economy. This thesis is divided into four parts: I. High temperature cleaning in combustion processes. II. Design evaluations of the Panel Bed Filter technology. III. Biomass gasification IV. High temperature cleaning of biomass gasification product gas The first part validates the filter performance through field experiments on a full scale filter element employed to a biomass combustion process and relates the results to state of the art within comparable technologies (i.e. based on surface filtration). The derived field experience led to new incentives in the search for a simplified design featuring increased capacity. Thus, enabling both high efficiency and simplified production and maintenance. A thorough examination of design fundamentals leading to the development of a new filter geometry is presented. It is evident that the up-stream process has significant influence upon the operation conditions of a filter unit. This has lead to a detailed investigation of some selected aspects related to the thermochemical conversion. Furthermore, the influence of fuel characteristics upon conversion and product gas quality is discussed. The last part discusses the quality of biomass gasification product gas and requirements put upon the utilisation of this gas in turbines, diesel engines or other high temperature applications. Filtration experiments conducted on product gas derived from wood gasification are reported and discussed.

Variable compression engines are a mean to meet the demand on lower fuel consumption. A high compression ratio results in high engine efficiency, but also increases the knock tendency. On conventional engines with fixed compression ratio, knock is avoided by retarding the ignition angle. The variable compression engine offers an extra dimension in knock control, since both ignition angle and compression ratio can be adjusted. The central question is thus for what combination of compression ratio and ignition angle the maximum efficiency is achieved, considering the set of compression ratios and ignition angles that give a sufficiently low knock intensity. Four knock detection methods are proposed, compared and evaluated with respect to robustness for noise and choices of parameter values. Three of the knock detectors are categorised as on-line, and are designed for giving feedback about knock occurrence to the engine control unit. The methods can determine both whether or not knock is present and the crank angle at knock onset. A study of the relationship between knock oscillation properties and knock-onset is performed. It is concluded that the logarithm of the normalised knock energy depends almost linearly on the rate of knock occurrence. A new formulation of multi-zone engine models is presented. The formulation makes it easy to increase or decrease the number of zones during the simulation. One of many possible applications is the investigation of engine efficiency. An analysis of experimental data shows how the engine efficiency changes with compression ratio and ignition angle. An engine torque model is developed and validated, from which the optimal choice of compression ratio and ignition angle can be calculated with high accuracy.

QC 20100601

At present, the main cooking fuels inChinaare natural gas, coal gas, liquefied petroleum gas (LPG), coal, biogas, wood and straw. This paper reviews the characteristics, advantages, disadvantages and the current application status of these different cooking fuels. Moreover, a questionnaire survey is presented, dealing with different cooking fuels in Chinese households and the occupants’ perceived health, ventilation behaviors and general knowledge in potential health hazards. About 56% of the respondents of the questionnaire survey stated that symptoms like itching eyes, dry or irritated throat, irritated nose, running or blocked nose and headache were worse when they were cooking in their kitchens. This suggests that cooking fuel combustion has a significant influence on human health. The most evident health effect was that wood and straw as cooking fuel caused eye irritation. The present common house planning in Chinese countryside, where the kitchens are separated from the rest of the house via a courtyard, is very likely to reduce the stove contaminant exposure of all occupants.   In general, the main cooking fuels of the cities tend to be better than the cooking fuels of the countryside. Natural gas appears to be the cleanest cooking fuel among all urban cooking fuels except electricity. For the rural residents, biogas or LPG is a better choice than wood, straw and coal as cooking fuel.

For natural gas combustion, there is a large amount of experience in the gas turbine industry. However, much of the design work is based on costly combustion tests due to insufficient accuracy of existing prediction tools for data such as emissions and effects due to fuel composition. In the present work, Computational Fluid Dynamics (CFD) approach is used to study partially premixed combustion in the 3rd generation DLE (Dry Low Emission) burner that is used in SGT-700 and SGT-800 gas turbines. The fuels that are studied here are natural gas and enriched hydrogen fuel. The CFD models which are used in this work are an axisymmetric and a 3D model and the softwares are ANSYS CFX and ANSYS FLUENT. One of the main objectives of this thesis is the study of flame shape and NOx emission in hydrogen enriched combustion. In the first study of the present work, effect of adding hydrogen to non-preheated gas combustion was investigated and the results were compared with the available measurement data. Calculated laminar burning velocity with CANTERA showed a good agreement with the experimental and numerical references. Also, the accuracy of generated flamelet libraries in CFD tools to calculate adiabatic flame temperature was compared with different available tools. Results showed good agreement between available tools for the ranges of interest. In addition, flame shape and NOx prediction was studied in the gas turbine burner. Adding hydrogen to the fuel increased significantly turbulent burning velocity and OH distribution in the domain. The effect of hydrogen on the central stagnation point was studied and the simulation results did not show a significant effect on the stagnation point location. Beside the flame shape, this study showed that although the CFD NOx prediction tools in ANSYS CFX and ANSYS FLUENT predict the trend of NOx and the flame propagation in the right manner, in order to use as a reliable prediction tool in the gas turbine industry they need to be improved.