No description available.

No description available.

Industrial flaring can have negative impacts on regional air quality and recent studies have shown that flares are often operated at low combustion efficiency, which exacerbates these air quality impacts. This thesis examines industrial flaring with the objectives of (1) assessing the air quality impacts of flares operating at a variety of conditions, (2) examining the extent to which improvements in flare operations could reduce emissions, (3) identifying opportunities for recycling flared gases in fuel gas networks, and (4) identifying opportunities for reducing the generation of flared gases, using the improved control of catalytic cracking operations as a case study. The work presented in this thesis demonstrates that flares operating at low combustion efficiency can increase localized ambient ozone concentrations by more than 15 ppb under some conditions. The impact of flares on air quality depends most strongly on combustion efficiency, the flow rates to the flares and the chemical composition (photochemical reactivity) of the emissions. Products of incomplete combustion and nitrogen oxides emissions from flaring generally had a smaller impact on air quality than unburned flare gases. The combustion efficiency at which a flare can operate can be constrained by the flare’s design. In a case study of an air-assisted flare, it was demonstrated that choices in blower configurations could lead to emissions that were orders of magnitude greater or less than those predicted using an assumed combustion efficiency of 98%. Designing flares with air-assist rates that can be finely tuned can significantly reduce emissions. Similarly, flaring can be reduced by integrating sources of waste gases into fuel gas networks. Analyses for a petroleum refinery indicated that this integration can often be accomplished with little net cost by expanding boiler capacities. Finally, flared gases can be reduced at their source. A case study of a fluid catalytic cracking indicated that using better temperature control could significantly minimize flared gases. / text

Finite volume method was employed for analyzing the three-dimensional turbulent flow structures, species distributions, and mixing behaviors of combustion flows in a rotary kiln under various operation conditions. The modified £e-£`turbulence model together with wall functions was adopted. Devolatilization of solid wastes were simulated by gaseous methane (CH4) non-uniformly distributed along the kiln bed. Combustion process was considered as a two-step reaction when primary air entered and mixed with methane gas in the first combustion chamber. Mixing-controlled eddy-dissipation model was employed for predicting the reaction rates of CH4, O2, CO2, CO and H2O. Effects of inleakage air, kiln rotation speed and methane distribution along the kiln bed were also examined. Results show that 128% excess air will get the best combustion efficiency, above which the combustion efficiency will decrease. The temperature and species are not uniformly distributed and are vertically stratified on cross-sectional plane. The combustion efficiency will also be lowered if there is inleakage airflow. Results also show rotation speed and methane distributions have little effect on combustion efficiency.

Co-firing is a combustion process in which more than one type of fuel is used. In many cases, co-firing reduces fuel costs and/or reduces the environmental impact. The objective of this research was to test the hypothesis that adding biogas to be co-fired with biomass in a traditional cookstove reduces indoor air pollution and increases the combustion efficiency. The impact of co-firing on indoor air pollution is assessed by comparing the concentrations of carbon monoxide and particulate matter in the exhaust stream of a co-fired cookstove to a cookstove fueled with biomass alone. The concentrations of each of these pollutants were measured using a portable emissions monitoring system. Combustion efficiency is defined as the ratio of energy released by combustion to energy in the fuel. Instead of combustion efficiency, the impact of co-firing was assessed on the modified combustion efficiency, which is defined as CO2/(CO2+CO) on a molar basis. This is because CO and CO2 concentrations can be measured. In addition, the impact of cofiring on other parameters such as thermal efficiency, specific fuel consumption rate, and specific emission of CO, CO2, and PM were assessed. Previous investigation of biomass combustion in traditional cookstoves indicates that power harvested using a thermoelectric generator can be used to drive a fan and increase the amount of air flowing into the combustion zone. The impact of using a fan on indoor air pollution and combustion efficiency was also assessed. It was found that co-firing biomass with optimum amount of biogas reduced the emission of CO by 32 % and PM by 33 % and increased the modified combustion efficiency by 1.3 %. It was found that using a fan reduced the emission of CO by 35 % and PM by 39 % and increased the modified combustion efficiency by 1.1 %. Finally, the combination of co-firing and use of a fan reduced the emission of CO by 58 % and PM by 71 % and increased the modified combustion efficiency by 2.8 %.

The aim of this diploma thesis is to experimentally measure the Golem 1.1 fireplace insert for heating with and without a deflector in the Steko s.r.o. company’s test room. Following this measurement, the emissions of CO, CO2, oxygen content in the flue gases and the temperature in the flue duct are listed here and the efficiency is calculated for different modes of primary air sucked in the insert and for different numbers of fuel pieces.

No description available.

<p>Постоји потреба за развојем котлова који сагоревају ефикасно биомасу и који<br />задовољавају све строжије еколошке прописе. Да би се ови циљеви постигли<br />поред експерименталног метода и класичних прорачуна веома корисна је<br />примена савремених софтвера из области Прорачунске динамике флуида<br />(CFD). Једна од битних карактеристика квалитетног сагоревањa је време<br />задржавања гасова у ложишту. Ова величина се не може израчунати, а њено<br />експериментално одређивање је упитно. У овом раду је развијен метод<br />прорачуна времена задржавања гасова помоћу CFD. Посматрано је изотермно<br />струјање, при чему је у нумеричким експериментима разматран утицај<br />геометријских и погонских карактеристика на време задржавања гасова.<br />Установљено је да угао млазница секундарног ваздуха као и брзина<br />секундарног ваздуха доводе до 20 процентне релативне разлике средњег<br />времена задржавања између најбољег и најлошијег случаја. По питању<br />положаја и димензија преграда овај распон је 30 процената.</p> / <p>Postoji potreba za razvojem kotlova koji sagorevaju efikasno biomasu i koji<br />zadovoljavaju sve strožije ekološke propise. Da bi se ovi ciljevi postigli<br />pored eksperimentalnog metoda i klasičnih proračuna veoma korisna je<br />primena savremenih softvera iz oblasti Proračunske dinamike fluida<br />(CFD). Jedna od bitnih karakteristika kvalitetnog sagorevanja je vreme<br />zadržavanja gasova u ložištu. Ova veličina se ne može izračunati, a njeno<br />eksperimentalno određivanje je upitno. U ovom radu je razvijen metod<br />proračuna vremena zadržavanja gasova pomoću CFD. Posmatrano je izotermno<br />strujanje, pri čemu je u numeričkim eksperimentima razmatran uticaj<br />geometrijskih i pogonskih karakteristika na vreme zadržavanja gasova.<br />Ustanovljeno je da ugao mlaznica sekundarnog vazduha kao i brzina<br />sekundarnog vazduha dovode do 20 procentne relativne razlike srednjeg<br />vremena zadržavanja između najboljeg i najlošijeg slučaja. Po pitanju<br />položaja i dimenzija pregrada ovaj raspon je 30 procenata.</p> / <p>There is a need for development of boilers for burning biomass, that are energy<br />efficient, and additionally satisfying increasingly stringent ecological regulations. In<br />order to reach these goals beside usage of classic approaches, experiments and<br />standard calculations, it would be very useful to use contemporary softwares from<br />the field of Computational fluid dynamics. One of the important characteristics of<br />proper combustion is residence time of gases in the boilers furnace. This parameter<br />can not be calcluated, and its measurement is very difficult. In this work method for<br />its detemination has been developed using CFD. Problem analysed included<br />isothermal flow, and variations in the geometric and plant parameteres. Results of<br />numeric experiments are: angle of the secondary air jets as also velocity of the<br />secondary air results in 20 percent in difference expressed as relative average gas<br />residence time between best and worst case. With baffles, its position and length this<br />difference was 30 percents.</p>

No description available.

Trapped Vortex Combustor (TVC) is a relatively new concept for potential use in gas turbine engines addressing ever increasing demands of high efficiency, low emissions, low pressure drop, and improved pattern factor. This concept holds promise for future because of its inherent advantages over conventional swirl-stabilized combustors. The main difference between TVC and a conventional gas turbine combustor is in the way combustion is stabilized. In conventional combustors, flame is stabilized because of formation of toroidal flow pattern in the primary zone due to interaction between incoming swirling air and fuel flow. On the other hand, in TVC, there is a physical cavity in the wall of combustor with continuous injection of air and fuel leading to stable and sustained combustion. Past work related to TVC has focussed on use of two cavities in the combustor liner. In the present study, a single cavity combustor concept is evaluated through simulation and experiments for applications requiring compact combustors such as Unmanned Aerial Vehicles (UAVs) and cruise missiles. In the present work, numerical simulations were initially performed on a planar, rectangular single-cavity geometry to assess sensitivity of various parameters and to design a single-cavity TVC test rig. A water-cooled, modular, atmospheric pressure TVC test rig is designed and fabricated for reacting and non-reacting flow experiments. The unique features of this rig consist of a continuously variable length-to-depth ratio (L/D) of the cavity and optical access through quartz plates provided on three sides for visualization. Flame stabilization in the single cavity TVC was successfully achieved with methane as fuel, and the range of flow conditions for stable operation were identified. From these, a few cases were selected for detailed experimentation. Reacting flow experiments for the selected cases indicated that reducing L/D ratio and increasing cavity-air velocity favour stable combustion. The pressure drop across the single-cavity TVC is observed to be lower as compared to conventional combustors. Temperatures are measured at the exit using thermocouples and corrected for radiative losses. Species concentrations are measured at the exit using an exhaust gas analyzer. The combustion efficiency is observed to be around 98-99% and the pattern factor is observed to be in the range of 0.08 to 0.13. High-speed imaging made possible by the optical access indicates that the overall combustion is fairly steady, and there is no major vortex shedding downstream. This enabled steady-state simulations to be performed for the selected cases. Insight from simulations has highlighted the importance of air and fuel injection strategies in the cavity. From a mixing and combustion efficiency standpoint, it is desirable to have a cavity vortex that is anti-clockwise. However, the natural tendency for flow over a cavity is to form a vortex that is clockwise. The tendency to blow-out at higher inlet flow velocities is thought to be because of these two opposing effects. This interaction helps improve mixing, however leads to poor flame stability unless cavity-air velocity is strong enough to support a strong anti-clockwise vortex in the cavity. This basic understating of cavity flow dynamics can be used for further design improvements in future to improve flame stability at higher inlet flow velocities and eventually lead to the development of a practical combustor.