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Landfill fires are relatively common incidents that landfill operators encounter which have great impact on landfill structure and the environment. According to a U.S. Fire Administration report in 2001, an average of 8,300 landfill fires occurs each year in the United States, most of them in the spring and summer months. Subsurface spontaneous fires are considered the most dangerous and difficult to detect and extinguish among landfill fires. Few studies have been conducted on spontaneous fires in landfills. Information regarding the thermal behavior of solid waste is not available nor have measurements been made to evaluate spontaneous ignition of solid waste. The purpose of this research was to provide information concerning the initiation of spontaneous ignition incidents in landfills, and investigate the conditions favoring their occurrence. This study enabled better understanding of the self-heating process and spontaneous combustion in landfills. Effects of parameters critical to landfill operation on spontaneous combustion were determined. Spontaneous combustion occurs when materials are heated beyond the ignition temperature. Temperature rise occurs inside the landfill due to exothermic reactions which cause self-heating of the solid waste. Oxygen introduction leading to biological waste degradation and chemical oxidation is believed to be the main cause of rising solid waste temperatures to the point of ignition. A survey was distributed to landfill operators collecting information regarding spontaneous firs incidents in their landfills. Survey results raised new questions necessitating further study of subsurface fires incidents. Subsurface spontaneous fires were not restricted to any landfill geometry or type of waste (municipal, industrial, commercial, and construction and demolition). Results showed that landfill fires occur in landfills that do and do not recirculate leachate. Although new methods have been developed to detect subsurface fires, landfill operators depend primarily on visual observation of smoke or steam to detect the subsurface fires. Also, survey results indicated that excavating and covering with soil are the most widespread methods for extinguishing subsurface fires. Methane often has been suspected for initiating spontaneous subsurface firs in the landfill. However, combustible mixture of methane and oxygen requires very high temperature to ignite. In this study it was shown that spontaneous fires are initiated by solid materials with lower ignition points. Laboratory tests were conducted evaluating the effect of moisture content, oxygen concentration and leachate on spontaneous ignition of solid waste. A new procedure for testing spontaneous ignition is described based on the crossing-point method. The procedure was used to study the spontaneous combustion of solid waste and determine the auto-ignition temperature of the solid waste components and a synthesized solid waste. Correlations have been established between auto-ignition temperature, specific weight and energy content and between self-heating temperature and specific weight. Correlations indicated that compaction can help avoid spontaneous combustion in the landfill. Dense materials require higher energy to increase in temperature and limit the accessibility of oxygen. In the experimental work, moisture was found to promote both biological and chemical self-heating. Increasing moisture content lowers the solid waste permeability and absorbs more energy as it evaporates. Dissolved solids in leachate were found to promote self-heating and ignition more than distilled water. Varying oxygen concentrations indicated that heat generation occurs due to chemical oxidation even at oxygen concentration as low as 10% by volume. However, at 10% by volume oxygen, solid waste did not exhibit thermal runaway nor flammable combustion. At 0% by volume oxygen, tests results indicated occurrence of self-heating due to slow pyrolysis. A numerical one-dimensional energy model was created to simulate temperature rise in landfill for four different scenarios. Using the results from the laboratory experiment, the model estimated the heat generation in solid waste due to chemical reactions. Results from the scenario simulations indicated that moisture evaporation is the major heat sink in the landfill. The model showed that gas flow has a cooling effect due to increasing amount of evaporated water and can control the temperature inside the landfill. The model showed that a temperature higher than the biological limit can be maintained in the landfill without initiating spontaneous fire.

<p> Levitation melting was used to study the oxidation kinetics of free falling iron droplets. Single droplets of Armco iron were deoxidized and allowed to fall through oxidizing columns of known heights and then quenched in Silicone Oil. The rate of oxygen pick up by a droplet was found to be dependent upon its initial temperature, its size, and the composition of the reacting gas. The proposed mechanism is presented with kinetic data.</p> / Thesis / Master of Engineering (MEngr)

The oxidation of three different steels used in the construction of petroleum refineryheaters was investigated by using thermogravimetric analysis technique (TGA). C-5,P-11, and P-22 steel samples were tested in two different oxidizing environments / air and CO2+N2+H2O (that simulates the combustion products of natural gas) at two different temperatures / 450oC and 500oC. In air oxidation P-22 had the best oxidation resistance among the three steels at two temperatures. In CO2+N2+H2O environment,C-5 possessed better oxidation resistance than P-22 and P-11. Analyses of oxidation products by using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out to correlate TGA results to oxide composition and morphology. Lower oxidation rate of P-22 in air was explained with reference to the formation of Cr-O phase. Analytical rate equations showed that all the steels obeyed parabolic rate equation during oxidation and no transition was observed

Orientador: Matthieu Tubino / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T05:19:24Z (GMT). No. of bitstreams: 1 Castro_AdrianoGomesde_D.pdf: 1872629 bytes, checksum: a53102e92aa91347cbcb783b0cdec7b5 (MD5) Previous issue date: 2013 / Resumo: Óleos vegetais e biodieseis são facilmente oxidados, sendo necessário a adição de anti-oxidantes. Esse trabalho mostra que a curcumina age como antioxidante nos biodieseis de soja, girassol, milho, canola e coco babaçu. No óleo de coco babaçu ela age como antioxidante e nos demais óleos estudados não apresenta efeito ou age como pró-oxidante, de acordo com a sua concentração e do tipo de óleo. A curcumina apresenta-se termicamente estável até em torno de 175°C, podendo ser usada como aditivo até essa temperatura. Ela é solúvel em até 0,10% em massa, nos óleos e nos biodieseis. A estabilidade oxidativa depende da temperatura, da concentração de antioxidante e da composição química dos biodieseis. A ordem da estabilidade oxidativa para os biodieseis estudados é: girassol < soja < canola < milho < coco babacu; e para os óleos vegetais é: girassol < coco babacu < canola < milho < soja. A cinética de retardamento da oxidação dos biodieseis pode ser considerada como de primeira ordem devido às boas correlações linear apresentadas entre logaritmo natural da concentração de aditivo versus o período de indução. As energias de ativação foram obtidas pela equação de Arrhenius e os parâmetros termodinâmicos, DH* e DS* pela equação de Eyring e o DG* pela equação fundamental da termodinâmica. O período de indução dos biodieseis e dos óleos à 25°C foi obtido pela equação que correlaciona o logaritmo natural do período de indução com a temperatura. Observou-se aumento da estabilidade oxidativa nos biodieseis de girassol e de coco babaçu de 0,98 e 149,82 meses respectivamente, com a adição de 0,05% em massa de curcumina, e para os biodieseis de soja, canola e milho, 2,41, 2,35 e 1,10 meses respectivamente, com a adição de 0,10% em massa de curcumina. Observou-se, também, que o período de indução dos biodieseis e dos óleos correlaciona linearmente com o índice de iodo dos mesmos. / Abstract: Vegetable oils and biodiesel are easily oxidized requiring the addition of antioxidants. This study shows that curcumine acts as antioxidant in biodiesel of soybean, sunflower, corn, canola and babassu coconut. In babassu coconut oil it acts as antioxidant however in the other oils studied it present no effect or act as a pro-oxidant, according to the oil and its concentration. Curcumine is thermally stable up to about 175 °C, therefore it can be used as antioxidant until this temperature. It is soluble up to 0.10% by weight in oils and biodiesel. As expected, the oxidative stability is of biodiesel is dependent of the temperature, of its chemical composition and of the concentration of the antioxidant. The order of oxidative stability for biodiesel is: sunflower<soybean<canola<corn<babassu coconut, and for vegetable oil is: sunflower<babassu coconut<canola<corn<soybeans. The kinetics of the oxidation retarding of biodiesel can be considered as a first order due to the good linear correlations displayed between in additive concentration versus the induction period. The activation energies were obtained using Arrhenius equation and the thermodynamic parameters such as DH* and DS* by Eyring equation and DG* by the equation fundamental of thermodynamic. The induction period of oils and biodiesels at 25 °C was obtained by equation that correlates the natural logarithm of the induction period with the temperature. Increase in the oxidative stability biodiesel of babassu coconut and sunflower is of 149.82 months and 0.98 respectively, with the addition of 0.05 % w/w of curcumine, and for the biodiesel of soybean, canola and corn, 2.41, 2.35 and 1.10 months, respectively, by the addition of 0.10% w/w of curcumine. It was also observed that the induction period of biodiesel and oils has a linear relationship with its respectives iodine values. / Doutorado / Quimica Analitica / Doutor em Ciências

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Irrigation of the municipal cemetery in Brigham City, Utah resulted in stained headstones in 2001 and 2002. The water used in the irrigation came from Mantua reservoir, a medium sized impoundment situated near the mouth of Box Elder Canyon. In order for Brigham City to establish a city wide secondary pressurized irrigation system using water from Mantua reservoir, the cause and the source of staining problem must be determined. Previous research (Wallace 2006) determined that the source of the staining was the reduction of iron found in Mantua Reservoir sediments that occurred when seasonal variations in the reservoir caused anaerobic conditions. The reduced iron then dissolved in the water and was used in the irrigation system, causing re-oxidation of the iron. The oxidized iron then precipitated out on the headstones causing the staining. The purpose of this investigation is to determine the iron oxidation kinetics after the re-aeration of the water which will help determine appropriate mitigation methods. A secondary purpose is to confirm the Mantua reservoir's capacity to become anaerobic, resulting in the conditions which cause staining. Using laboratory investigations and computer modeling, I determined that on re-aeration, fifty percent of the dissolved iron in the water precipitates in five hours. Using first-order kinetics to model this process, I found the rate constant of the kinetic reaction to be 0.0029 min-1. Fitting a geochemical computer model of the iron oxidation kinetics in Mantua reservoir, which uses a higher-order kinetics model to better model this process, to experimental kinetic data yielded a rate constant of 4x1013 /atm x min. I also recreated the staining process in the laboratory using concrete. This was successful and provided visual evidence that the iron precipitates out of the water and stained the concrete within a couple of hours of application. Field data collected from Mantua reservoir showed that the dissolved oxygen concentration in the reservoir drops regularly below levels consistent with equilibrium to the atmosphere. While my field measurements did not record anaerobic conditions, based on the patterns shown, this study shows that it would be possible for anaerobic conditions to occur during warmer weather.