The move from fossil fuels is getting more relevant throughout the globe, mainly for it getting more costly to emit CO$_2$. The steel industry is one of the biggest contributor of the CO$_2$ emissions, and is therefore very motivated to reduce their emissions. One way to reduce the emissions is to go from coal to bio-char as a reducing agent. BEST(Bio-energy and sustainable technologies) is a research institute in Austria, and have been tasked to do research on bio-char and what problems that may occur with changing from coal to bio-char. One problem with bio-char is that it is prone to self ignition. This project aims is to develop a numerical model that can simulate self heating within bio-char stockpiles. The tool will be for a one-dimensional case using Cartesian coordinates. The calculations are based on the SIMPLE algorithm for Navier-Stokes equations, which is widely used within CFD calculations. This tool has been used to do sensitivity analysis for multiple variables and parameter studies for kinetic parameters related to the oxidation that occurs when bio-char is exposed to oxygen. Results show that oxygen concentration is the limiting factor to how much heat is released within the bag during simulations. Results also show that the accurate descriptions of reaction schemes and their rate expressions is very important to get results that is in line with real world scenarios.

This investigation provides a comprehensive experimental dataset and kinetic model for biomass gasification, over a wide temperature range (1150-1350 °Ï¹) in CO2, H2O and the combination of these two reactant gases over the mole fraction ranges of 0 to 0.5 for H2O and 0 to 0.9 for CO2. The data come from a unique experimental facility that tracks continuous mass loss rates for poplar wood, corn stover and switchgrass over the size range of 6-12.5 mm. In addition, the data include char size, shape, surface and internal temperature and discrete measurements of porosity, total surface area, pore size distribution and composition. This investigation also includes several first-ever observations regarding char gasification that probably extend to char reactivity of all types and that are quantified in the model. These include: the effect of ash accumulation on the char surface slowing the apparent reaction rate, changes in particle size, porosity and density as functions of burnout, and reaction kinetics that account for all of these changes. Nonlinear least-squares regression produces optimized power-law model parameters that describe gasification with respect to both CO2 and H2O separately and in combination. A single set of parameters reasonably describes rates for all three chars. Model simulations agree with measured data at all stages of char conversion. This investigation details how ash affects biomass char reactivity, specifically the late-stage burnout. The ash contents ratios in the raw fuels in these experiments are as high as 40:1, providing a clear indication of the ash effect on the char reactivity. The experimental results definitively indicate a decrease in char reaction rate with increasing initial fuel ash content and with increasing char burnout -- most pronounced at high burnout. This investigation postulates that an increase in the fraction of the surface covered by refractory material associated with either higher initial ash contents or increased burnout decreases the surface area available for reaction and thus the observed reaction rate. A quantitative model that includes this effect predicts the observed data at any one condition within the data uncertainty and over a broad range of fuel types, particle sizes, temperatures, and reactant concentrations slightly less accurately than the experimental uncertainty. Surface area, porosity, diameter, and density predictions from standard models do not adequately describe the experimental trends. Total surface area increases slightly with conversion, with most of the increase in the largest pores or channels/vascules not measurable by standard surface area techniques but most of the surface area is in the small pores. Porosity also increases with char conversion except for abrupt changes associated with char and ash collapse at the end of char conversion. Char particle diameters decrease during these kinetically controlled reactions, in part because the reaction is endothermic and therefore proceeds more rapidly at the comparatively warmer char surface. SEM images qualitatively confirm the quantitative measurements and imply that the biomass microstructure does not appreciably change during conversion except for the large pore diameters. Extant char porosity, diameter, surface area, and related models do not predict these trends. This investigation suggests alternative models based on these measurements.

This investigation provides a comprehensive experimental dataset and kinetic model for biomass gasification, over a wide temperature range (1150-1350 °Ï¹) in CO2, H2O and the combination of these two reactant gases over the mole fraction ranges of 0 to 0.5 for H2O and 0 to 0.9 for CO2. The data come from a unique experimental facility that tracks continuous mass loss rates for poplar wood, corn stover and switchgrass over the size range of 6-12.5 mm. In addition, the data include char size, shape, surface and internal temperature and discrete measurements of porosity, total surface area, pore size distribution and composition. This investigation also includes several first-ever observations regarding char gasification that probably extend to char reactivity of all types and that are quantified in the model. These include: the effect of ash accumulation on the char surface slowing the apparent reaction rate, changes in particle size, porosity and density as functions of burnout, and reaction kinetics that account for all of these changes. Nonlinear least-squares regression produces optimized power-law model parameters that describe gasification with respect to both CO2 and H2O separately and in combination. A single set of parameters reasonably describes rates for all three chars. Model simulations agree with measured data at all stages of char conversion. This investigation details how ash affects biomass char reactivity, specifically the late-stage burnout. The ash contents ratios in the raw fuels in these experiments are as high as 40:1, providing a clear indication of the ash effect on the char reactivity. The experimental results definitively indicate a decrease in char reaction rate with increasing initial fuel ash content and with increasing char burnout -- most pronounced at high burnout. This investigation postulates that an increase in the fraction of the surface covered by refractory material associated with either higher initial ash contents or increased burnout decreases the surface area available for reaction and thus the observed reaction rate. A quantitative model that includes this effect predicts the observed data at any one condition within the data uncertainty and over a broad range of fuel types, particle sizes, temperatures, and reactant concentrations slightly less accurately than the experimental uncertainty. Surface area, porosity, diameter, and density predictions from standard models do not adequately describe the experimental trends. Total surface area increases slightly with conversion, with most of the increase in the largest pores or channels/vascules not measurable by standard surface area techniques but most of the surface area is in the small pores. Porosity also increases with char conversion except for abrupt changes associated with char and ash collapse at the end of char conversion. Char particle diameters decrease during these kinetically controlled reactions, in part because the reaction is endothermic and therefore proceeds more rapidly at the comparatively warmer char surface. SEM images qualitatively confirm the quantitative measurements and imply that the biomass microstructure does not appreciably change during conversion except for the large pore diameters. Extant char porosity, diameter, surface area, and related models do not predict these trends. This investigation suggests alternative models based on these measurements.

Bio-oil created from biomass sources do not have desirable fuel qualities. Due to their petroleum origins, plastics and micronized rubber powder (MRP) improve oil quality when co-pyrolyzed with biomass. Southern yellow pine, a food grade polymer (FGP) and micronized rubber powder (MRP) were co-pyrolyzed at various ratios in an auger reactor to improve the bio-oil. MRP proved to be the best additive, reducing acids, creating aromatic hydrocarbons, reducing water content, and increasing heating values in created bio-oil, while the FGP led to a formation of a liquid product containing a high concentration of phenolic compounds. To improve these qualities further, nickel oxide and sodium carbonate were added in-vivo to the coeeds. Nickel oxide influenced higher aromatic hydrocarbon production and reduced oxygen formation. Sodium carbonate greatly reduced the concentration of acids and water. Both catalysts improved the creation of unsaturated hydrocarbons, phenol compounds, and enhanced heating values with nickel oxide performing better than sodium carbonate.

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No description available.

Clean coal technologies are now becoming popular because of their high efficiencies and minimal environmental impact. Higher operating pressures have been applied to clean coal technologies. The effect of pressure on coal pyrolysis and char combustion has been extensively studied but still remains to be further explored. The objective of this project was to characterize high pressure, high heating rate coal pyrolysis and char combustion, with emphasis on improving coal/char high pressure combustion models. A flat-flame burner was used in a high pressure laminar flow facility to conduct high temperature, high heating rate pyrolysis and combustion experiments for four coals. The high-heating-rate (10000 K/s), high-temperature atmosphere can better simulate industrial conditions than the conventional drop tube facility. Pressure and heating rate have a significant impact on the total volatiles, char physical structure including morphology, and char internal surface areas. The high heating rate decreases the swelling ratios of chars at pressures from 2.5 to 15 atm. TGA char oxidation reactivities were measured at the same total pressure as the char preparation pressure. The general trend was that the TGA reactivity on a gram per gram available basis decreased with increasing char formation pressure. When the reactivity was normalized by either the N2 or CO2 surface area, the normalized reactivity was found to be relatively constant with increasing pressure. Char burnout was measured at different pressures and O2 concentrations at high temperature in the pressurized flat flame burner facility. For a given pressure, the particle diameter ratio based on coal (d/dcoal,0) decreased with increasing O2 concentration. Two char kinetic models (CBK 8 and CBK/E) were used to fit the char burnout data, and the modeling results showed that the intrinsic char oxidation rate increased with increasing total pressure at constant oxygen partial pressure.

Coal plays a significant role in electricity production worldwide and will into the foreseeable future. Technologies that improve efficiency and lower emissions are becoming more popular. High pressure reactors and oxyfuel combustion can offer these benefits. Designing new reactors effectively requires accurate single particle modeling. This work models a high-pressure, high-temperature, high-heating rate, entrained-flow, char oxidation data set to generate kinetic parameters. Different modeling methods were explored and a sensitivity analysis on char burnout was performed by varying parameters such as total pressure, O2 partial pressure, O2 and CO2 mole fractions, gas temperature, diameter, and pre-exponential factor. Pressure effects on char burnout modeling were found to be dependent on the set of kinetic parameters chosen. Using kinetic parameters from Hurt-Calo (2001) as opposed to values obtained from Niksa-Hurt (2003) yielded a trend seen in real data sets, that reaction order changes with temperature. Varying O2 mole fraction and partial pressure showed the most significant changes in char burnout. Varying diameter, total pressure, the pre-exponential factor, CO2 environment, and gas temperature all changed the char burnout extent as well. The effect of changing those parameters decreases in the order they are listed. Increasing any of these parameters resulted in an increase in char burnout except for particle diameter and CO2 mole fraction which led to a decrease. Char formation pressure affects reactivity, and a peak in reactivity is shown in this work at the 6 atm condition.

The activation energy of Douglas fir wood char gasified in carbon dioxide was determined. Activation energies were found for chars that had been pyrolyzed in nitrogen at 600, 750, and 900°C. A thermogravimetric analyzer provided the weight versus temperature data used to obtain the activation energies. The Coats-Redfern integral method of kinetic analysis was used to extract the activation energies from the data. This method can be used to obtain an activation energy from a single weight versus temperature trace for a constant heating rate. An overall apparent activation energy of 723 ± 60 kl/mole and a natural log of the pre exponential factor of 68.8 ± 6.2 was determined from the data collected for all three chars. The different char preparation temperatures did not appear to affect the activation energy. / Master of Science

Das Anliegen der Arbeit besteht darin, zu zeigen, dass der französische Dichter René Char (1907-1988) ausgehend von den ästhetischen Konzepten, die in der Schrift von Friedrich Nietzsche „Die Geburt der Tragödie aus dem Geiste der Musik“ formuliert sind, ein künstlerisches Selbstverständnis begründet, das auf einer tragischen Ästhetik ruht, und dass diese Ästhetik Chars Dichtung in hohem Maße prägt. In einem ersten Schritt wird das Konzept der tragischen Ästhetik entfaltet. Diese ist als Verschränkung der Prinzipien des Apollinischen und des Dionysischen zu verstehen. Das Konzept eines Zusammenspiels zweier gegensätzlicher Prinzipien,- des Apollinischen und des Dionysischen-, die nach Nietzsche das Phänomen der Kunst überhaupt möglich machen, ist der Höhepunkt einer langen europäischen Tradition ästhetischer Reflexion, welche die Ästhetik im Sinne einer doppelten Ästhetik denkt, als Zusammenspiel zwischen dem Schönen und dem Erhabenen. In einem zweiten Schritt wird untersucht, inwieweit diese doppelte Ästhetik als Tiefenstruktur die Lyrik Chars durchzieht. Es wird zunächst das apollinische Prinzip in der Lyrik Chars herausgearbeitet, z.B. die Bedeutung des Traums in seinen Gedichten und die daraus folgende Nähe Chars zu dem Surrealismus. In einem dritten Schritt wird das ästhetische Zusammenspiel zwischen Apollinischem und Dionysischem in Chars Dichtung analysiert. Dieses Zusammenspiel ist als dichterische Transfiguration der Negativität zu denken. Transfiguration der Negativität bedeutet in diesem Zusammenhang vor allem die poetische Umsetzung derjenigen Negativität, die vom Nationalsozialismus ausging, und die Char als Widerstandskämpfer erfahren hat. Bei der Untersuchung stellte sich heraus, dass Chars Lyrik eine ethische Dimension enthält, die in einer tragischen Ästhetik wurzelt, sodass man von einer im Ästhetischen begründeten Ethik sprechen kann, deren Kern die Gerechtigkeit ist. / The purpose of this work is to show that the french poet René Char (1907-1988) develops his esthetic comprehension of poetry through the concepts of Nietzsches early work „The birth of tragedy“ and that Chars poetry is essentially tragic. I first analyse the concept of tragic esthetic. Tragic esthetic consists in two principles, the apollinian and the dionysian. These principles constitute the dynamic of tragic esthetic. These principles are other forms of what the european esthetic tradition calls the beautiful and the sublime, and Nietzsches concepts result from this tradition. In a second step I analyse how these principles constitute the basics of Chars poetry. First I analyse the apollinian dimension of his poems, particularly the importance of dream and the surrealistic aspect of Chars poems. Then I analyse deeper the working of the dynamic of these two principles. This esthetic dynamic has to be understood as a transformation of negativity. Transformation of negativity means in Chars poetry first of all a poetic transformation of the nationalsocialist negativity, against which Char fought. By analysing this context, it appeared that Chars poetry contains an ethical dimension, which result from the tragic esthetic. And the heart of this ethical tragic esthetic is justice.