The majority of deaths and injuries in compartment fires result from inhalation of the toxic gas, carbon monoxide (CO), especially in locations remote from the burning compartment. This causes the transport and oxidation of CO in burning buildings to become an important topic. Studies have been conducted to determine the toxic environments produced inside, and in locations remote from, a burning compartment; however, no studies have investigated the composition of the exhaust gases during transport to remote locations. The goal of this study was to investigate fire exhaust gas transport through a hallway to determine the important parameters affecting the efficiency of sustained external burning in oxidizing toxic gases, including the hydrodynamic effects of different hallway configurations. Underventilated compartment fire experiments were performed with a compartment exhausting along the axis of a hallway. The design of the compartment allowed direct measurement of the global equivalence ratio which was used as a main correlating parameter. Characteristic global equivalence ratios and an ignition index concept were investigated to determine when sustained external burning would occur. Gas sampling was performed downstream of the hallway to determine the overall efficiency of sustained external burning, and in the hallway to provide detailed data on the processes occurring in the hallway. The oxidation of the exhaust gases traveling through the hallway was determined to vary among different species, and also to be very sensitive to the hydrodynamic mixing between the rich exhaust plume and the cooler ambient air in the hallway. In general, the overall oxidation of hydrocarbons was much more complete than for CO or soot. The gas temperatures in the hallway and fuel vaporization rate were also determined to affect oxidation in the hallway. Variations in the hallway inlet and exit soffits affected the hydrodynamic structure of the exhaust plume and oxidation efficiencies, with the inlet soffit exhibiting the strongest effect. / Master of Science

The performance of dry, low NOx gas turbines, which employ lean premixed (or partially premixed) combustors, is often limited by combustor stability. To overcome this issue, a novel design, referred to as a Stagnation Point Reverse Flow (SPRF) combustor, has been recently demonstrated. The SPRF combustor has been shown to produce low NOx emissions with both gaseous and liquid fuels. The objective of this thesis is to elucidate the interactions between the flowfield and combustion processes in this combustor for gas- and liquid-fueled operation. This is achieved with experimental measurements employing various optical diagnostic techniques. These include Particle Image Velocimetry (PIV), chemiluminescence imaging, Planar Laser-Induced Fluorescence (PLIF) of OH radicals and laser scattering from liquid droplets. Velocity measurements in gas-fueled operation show that both nonreacting and reacting flows exhibit a stagnation region with low mean velocity and high turbulence intensities. The high shear between the forward and reverse flows causes significant recirculation resulting in enhanced entrainment and mixing of the returning product gases into the incoming reactant jet for the reacting flow cases, which enables stable operation of the combustor at very lean equivalence ratios. Nonpremixed operation produces a flowfield similar to premixed case except in the near-field region where high turbulence intensities result in significant fuel-air mixing before combustion occurs. Operation of the SPRF combustor with liquid Jet-A is also investigated experimentally. The results indicate that while the overall flow features are similar to the gas-fueled SPRF combustor, the combustion characteristics and NOx performance in liquid operation are strongly controlled by fuel dispersion and evaporation. Injecting the liquid at the exit of the air annulus results in a highly lifted flame, similar to nonpremixed gaseous operation. On the other hand, retracting the fuel injector well inside the air annulus produces a well-dispersed fuel pattern at the reactant inlet leading to a reduction of the equivalence ratio in the fuel consuming reaction zones. Since the effective Dahmkohler number increases with global equivalence ratio, the difference in NOx emissions is more pronounced at higher fuel-air ratios as the retracted injector lowers the relative mixing time compared to the flush case.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

<p><strong>Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).</strong></p><p>Sumporni oksidi najče&scaron;će prisutni polutanti u atmosferi direktno utiču na zdravlje Ijudi i stvaranje kiselih ki&scaron;a ugrožavajući ekosistem. Razvijen je veliki proj postupaka odsumporavanja otpadnih gasova, dok je u naj&scaron;iroj upotrebi mokri neregenerativni postupak apsorpcije koji koristi jeftine hemikalije, kreč ili krečnjak. Zbog toga se posebna pažnja posvečuje i ispitivanju regenerativnih postupaka kod kojih se apsorpciono sredstvo delimično ili u potpunosti regeneri&scaron;e, a pri čemu su gubici apsorpcionog fluida zanemarljivi. Postupak sa limunskom kiselinom upravo ispunjava poslednji zahtev. Ostale prednosti ovog postupka su fleksibilnost, bez prisustva koplikovanih procesnih postupaka, mali oksidacioni gubici sumpor dioksida i netoksičnost reagensa.<br />Pri projektovanju kolone za odsumporavanje otpadnih gasova neophodno je poznavanje ravnotežnih podatka para-tečnost, hidrodinamičkih parametara (pad pritiska i količina zadržane tečnosti) i prenosa mase kao jednog od direktnih pokazatelja brzine apsorpcije ili ukupne brzine reakcije.<br />Izveden je matematički model ravnoteže za predvidjanje ravnotežnog parcijalnog pritiska sumpor dioksida iznad vodenog rastvora natrijum citrata za ceo opseg pH vrednosti pufera i temperature na osnovu eksperimentalnih vrednosti. Zaustavnom metodom je odredjena količina zadržane tečnosti u koloni. Analizirane su jednačine date u literaturi za predvidjanje pada pritiska i zapreminskih koeficijenata prenosa mase i odabrane one koje se mogu primeniti na odabrani sistem sumpor dioksid/citratni pufer.<br />Na osnovu eksperimentalnih podataka para-tečnost, hidrodinamičkih parametara i odabranih jednačina za prenos mase, izvr&scaron;en je proračun visine apsorpcione kolone sa Raschigovim prstenovima za izdvajanje sumpor dioksida iz otpadnog gasa i pokazano je da pad pritiska za eksperimentalno primenjene protoke gasa i tečnosti odgovara literaturno predloženom opsegu.</p> / <p><strong>Abstract was processed by technology for Optical character recognition (OCR).</strong></p><p>Control of sulfur dioxide emission has a relatively long history, especially in major industrial countries due to its common occurence and harmful effects. A number of dry and wet process comprising regenerable and throw-away process were investigated, but the wet throw-away process become the most widely accepted. The use of the flue gas desulphurization process with sodium citrate solution is recommended, as it is found that sodium citrate meets the specific needs of reversible sulphur dioxide absorption to buffer range as well as its capacity, chemical and physical stability.<br />Packed columns are widely used in the chemical industry for gas/liquid mass and heat transfer operations and they have found special use in small fractionating towers. Their use has also been found to be advantageous where corrosion control is essential. Fundamental steps necessary for design of absorption column for sulfur dioxide removal are:<br />- determination of vapor-liguid eguiiibrium data for the citrate buffer,<br />- determination of hydrodynamic parameters, i.e. holdup and pressure drop,<br />- determination gas-liquid mass transfer coefficients.<br />On the basis of the experimentally determined vapour pressures data, a model of the gas- equilibria was formulated. Holdups were measured for air/sodium citrate solution using the draining method. Also, literature-proposed eguations for determination of pressure drop, volumetric liquid-phase and gas-phase mass transfer coefficient in packed column were presented and chosen those that could be applied to flue gas/citrate puffer system. Therefore, on the base of obtained results the preposition for the design of packed column is presented.</p>

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

La valorisation des effluents gazeux à faible pouvoir calorifique, sous-produits de différents procédés industriels (gazéification du charbon ou de la biomasse, rejets industriels) apparait aujourd’hui comme une solution alternative pour accroître l’efficacité globale des systèmes de combustion par réduction des coûts énergétiques et contrôle des rejets dans l’environnement. Dans ce contexte, une étude expérimentale d'oxyflammes d'un gaz à très bas pouvoir calorifique, le gaz de haut fourneau (BFG), est réalisée pour évaluer l'effet conjoint de l'oxycombustion et du préchauffage des réactifs pour la stabilisation des flammes turbulentes. La configuration du brûleur consiste en un jet annulaire de gaz de haut fourneau (BFG), entouré de deux injections d’oxygène (interne ‘O2i’ et externe ‘O2e’). Son dimensionnement s’appuie sur une méthodologie originale basée sur la détermination d’une vitesse de convection critique UC* à l’extinction de flamme, dérivée d’une valeur expérimentale d'un nombre de Damköhler critique Dac*. Les structures de flammes sont caractérisées par imagerie de chimiluminescence OH* et les propriétés thermiques et chimiques sont évaluées par mesures de température et flux thermique à la paroi et de la composition des fumées. Les champs aérodynamiques 2D des écoulements réactifs sont mesurés par PIV. Quatre principales topologies de flamme sont observées avec cette configuration de brûleur et classées suivant leur mode de combustion. Sans préchauffage, les deux flammes concentriques, interne ‘O2i-BFG’ et externe ‘BFG-O2e’, sont attachées au brûleur à basse puissance (Type A) ; la flamme BFG-O2e peut présenter une stabilité intermittente (Type B), ou se décrocher du brûleur (Type C) à la puissance nominale de dimensionnement. Avec préchauffage des réactifs, la flamme annulaire BFG-O2e reste toujours accrochée au brûleur et la flamme centrale O2i-BFG présente une zone d’extinction locale pour des fortes valeurs de vitesse d’O2i (Type D). L’ensemble des résultats a permis de mettre en avant un bon accord entre les prédictions théoriques et les valeurs expérimentales de UC* avec un élargissement des domaines de stabilité de flamme avec le préchauffage. L'analyse aérodynamique permet de caractériser les transitions entre les structures de flammes. Une validation du critère de dimensionnement de l’oxy-brûleur est aussi effectuée par changement d’échelle, grâce à des mesures réalisées sur une installation semi-industrielle de 180 kW. / The effective utilisation of low calorific value fuel, as gaseous by-products of coal/biomass or industrial residual gases, provides not only excellent opportunities for low cost power generation but also for the reduction of environmental impact of combustion. The present work aims to consider the combination of oxyfuel combustion with fuel and/or oxygen preheating in order to increase thermal efficiency by heat recovery and enhance oxyfuel flame stabilization of blast furnace gas (BFG). This experimental study is performed with a burner consisting in an annular jet of BFG surrounded by two injections of oxygen (internal 'O2i' and external 'O2e'). Its dimensions are determined from an original design strategy based on an experimentally critical Damköhler number Dac*, which represents the theoretical limit of stabilisation of a turbulent diffusion BFG-O2 flame with preheated reactants. Flames structures are characterized by OH* chemiluminescence imaging. Thermal and chemical flame properties are evaluated by temperature and radiative flux analysis and pollutant emissions measurements. The 2D aerodynamic fields of reactive flows are determined by velocity measurements by PIV. Four LCV flames structures are resulting from this burner configuration. Without preheating, two concentric flames, internal 'O2i-BFG' and external 'BFG-O2e', are anchored at the burner (Type A) at low thermal power. When increasing the latter, the external flame BFG-O2e manifests some local fluctuations (Type B) or is lifted-off (Type C). With reactants preheating, the BFG-O2e flame is always anchored at the burner tip and the O2i-BFG flame could have local extinction zone for very high values of internal oxygen velocity (Type D). The results highlight a good agreement between theoretical and experimental critical velocity UC* which significantly increases with preheating. The aerodynamics study points out the transitions between the different flames structures. At semi-industrial scale, flames show similar structures to those obtained at laboratory scale. This validates the burner design strategy of preheated oxyfuel combustion adapted to LCV fuels, as well as the scale up criteria used.