The goal of this thesis was to understand what parameters would be most impactful when delivering dry, pulverized coal in a dilute-phase, with a high-pressure feed-system to a pressurized oxy-combustion (POC) reactor. Many studies have conveyed materials in dense-phase plugs at high-pressure or in dilute-phase flows at atmospheric pressure. Very few studies have fluidized and conveyed materials in dilute-phase flows at high pressure, as we needed to. Additionally, studies which might have been applicable based upon system -pressure and -phase delivered findings that were empirically based and therefore not specifically applicable to non-similar systems. 220 different tests were ran using a bench-scale apparatus consisting of a hopper, connecting conveying pipes, and a filter point (representing the future reactor). The system was pressurized to 300 psi using CO2. Dry, pulverized coal with an average diameter of 50 microns and a bulk density of 800.9 kg/m3 was fluidized and conveyed with different combinations of fluidization inlet and fluidization outlet flowrates. Each specific flowrate combination was tested 3 to 5 times. The resulting coal flowrates were recorded and analyzed to see which flowrate combination delivered 13.6 kgs coal/hr and had the least variability between tests. The fluidization inlet and outlet flowrates, coal moisture content, and system geometry were key parameters. In a 2-inch diameter hopper the fluidization inlet flowrate should be kept at 0.119 m/s or below to keep the fluidization regime within the hopper below the transition point to the bubbling fluidization regime. This was beneficial since less CO2 was needed by the system and smaller perturbations within the bed didn't disrupt flow leaving the hopper. The fluidization outlet flowrate could still advance the fluidization regime within the hopper even if the fluidization inlet flowrate is kept at 0.119 m/s. For a ¼ inch diameter the outlet should be kept at 0.005 m/s or above. Additionally, the standard deviation in the measured coal flowrate decreased dramatically when flow of gas was allowed to exit through the top of the coal column (fluidization outlet). The standard deviation was 8.2 kg/hr with the fluidization outlet closed and 3.5 kg/hr with the fluidization outlet flowing to provide 0.005 m/s in the bed above the coal outlet. Coal should have a moisture content between 3% and 6% to ensure that electrostatic interactions between coal particles is kept to a minimum. Finally, these results were found for specific hopper and fluidization inlet and outlet diameters. If these diameters are changed then some calculation must be done for these results to be applicable to systems that are not like the one described later in this thesis.

<p> An optimization study of an intermittent-flow multistage fluidized ion exchange column was performed using a stochastic approximation method. A new type of downcomer, a fluid diode, was designed and employed to alleviate liquid bypassing through the downcomer. The well known ion exchange system, H⁺/Na⁺ exchange on Dowex 50W resin, was used in this work. </p> <p> The volumetric efficiency of the system was optimized with regard to certain column and diode parameters. A maximum volumetric efficiency of 71.8 hr⁻¹ was obtained for the following conditions: </p> <p> average liquid flowrate = 3661 ml/min ; </p> <p> resin flowrate = 56.1 gm/min ; </p> <p> plate spacing 11.43 cm ; </p> <p> lateral diode displacement= 0.794 cm. </p> <p> Experiments have shown that a 78.2% increase in volumetric efficiency was achieved by use of the fluidic diode downcomers. </p> / Thesis / Master of Engineering (ME)

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The behavior of using oxygen carriers as bed material in a fluidized bed combustion was investigated in this work when methane, air and carbon monoxide, air are used as fluidizing gases. More specifically, conversion rate, unsteadiness and gas composition was investigated and it was found that the conversion rate of carbon monoxide and methane are higher when oxygen carriers are used as bed material compared to silica sand and that the highest conversion rate was for oxygen carriers with high oxygen transport capacity and high reactivity towards the gaseous fuel. And it was also found that unsteady concentration profiles were present for all oxygen carries when methane was used but only for manganese when carbon monoxide was used which indicates that low reactivity towards a gaseous fuel triggers unsteadiness. In addition to this ilmenite and F6MZ1100 was defluidized when carbon monoxide was used and no decrease in reactivity between oxygen carrier and oxygen was observed. The experiment was performed in a laboratory scale fluidized bed reactor were 4 different bed materials was used, manganese ore, ilmenite, F6MZ1100, silica sand and each batch used 15g of particles, a particle size of 125-180µm, a total flowrate of 900ml/min and a changing Air-fuel equivalence ratio to simulate a fuel lean and a fuel rich mixture. And in addition to this the particles were exposed to an alternating reducing and oxidizing condition to test reactivity between oxygen carrier and the used gaseous fuels. / Beteendet av syrebärare som bäddmaterial i en fluidiserad bäddförbränning har undersökts när en blandning av kolmonoxid,luft och metan,luft har använts som fluidiseringsgaser genom att utvärdera bränsle omvandlingsgraden, ostadigheter i rökgassammansättningen, rökgassammansättningen och arbetet visar att omvandlingsgraden av kolmonoxid och metan är högre när syrebärare används som bäddmaterial jämfört med när kiselsand används. Och högsta omvandlingsgraden var för syrebärare med hög syretransport kapacitet och hög reaktivitet med det gasformiga bränslet och det observerades även att ostadighet i rökgassammansättning är beroende av bränsletyp. När metangas användes fanns ostadigheter för samtliga bäddmaterial men endast för Mangan när kolmonoxid användes vilket indikerar att låg reaktivitet mellan flyktgaser och syrebärare utlöser ostadighet i rökgassammansättningen. Utöver detta uppstod fluidiseringsproblem för Ilmenit och F6MZ1100 när kolmonoxid användes vilket resulterade i partiell passering av fluidiseringsgaser genom reaktorn och utöver detta observerades inte någon minskad reaktivitet mellan syrebärarna och syre under experimentet. Experimentet utfördes i en fluidiserad bädd reaktor i laboratorieskala där 4 olika bäddmaterial testades, Manganmalm, Ilmenit, F6MZ1100 och Kiselsand och i varje experiment användes 15g partiklar med partikelstorleken 125-180μm och med ett total flödet på 900 ml/min. Och för att testa effekten vid olika blandningar av bränsle och luft ändrades luft-bränsle förhållandet så att bäddmaterialet exponerades för syreöverskott och syreunderskott och utöver detta exponerades även syrebärarna för omväxlande oxidation och reduktion för att utvärdera reaktiviteten mellan syrebärare och det gasformiga bränslet.

Biomass is considered a biorenewable alternative energy resource that can potentially reduce the use of natural gas and provide low cost power production or process heating needs. Biomass hydrodynamics in a fluidized bed are extremely important to industries that are using biomass material in gasfication processes to yield high quality producer gas. However, biomass particles are typically difficult to fluidize due to their peculiar shape and a second inert material, such as sand, is typically added to the bed. The large differences in size and density between the biomass and inert particles lead to nonuniform distribution of the biomass within the fluidized bed, and particle interactions and mixing become major issues. The main goal of this research was to use CFD as a tool for modeling and analyzing the hydrodynamic behavior of biomassas a single material or as part of a mixture in a fluidized bed. The first part of this research focused on the characterization of biomass particles in a fluidized bed and validation of a numerical model with experimental results obtained from pressure measurements and CT and X-ray radiograph images. For a 2D fluidized bed of glass beads, the pressure drop, void fraction and mean bed height expansion were in quantitative agreement between the experiments and simulations using Syamlal-O'Brien and Gidaspow drag models. It was encouraging that the Gidaspow model predictions were in close agreement because the model does not require knowing the minimum fluidization as an input. Ground walnut shells were used to represent biomass because the material fluidizes uniformly and is classified as a Geldart type B particle. Two-dimensional simulations of ground walnut shells were analyzed to determine parameters that cannot easily be measured experimentally. The parametric study for ground walnut shell indicated that the material can be characterized with a medium sphericity (~0.6) and a relatively large coefficient of restitution (~0.85). In the second part of this work numerical simulations of a ground walnut shell fluidizing bed with side air injection were compared to CT data for the gas-solid distribution to demonstrate the quantitative agreement for bed fluidization. The findings showed that 2D simulations overpredicted the fluidized bed expansion and the results did not demonstrate a uniformly fluidizing bed. The 3D simulations compared well for all cases. This study demonstrates the importance of using a 3D model for a truly 3D flow in order to capture the hydrodynamics of the fluidized bed for a complicated flow and geometry. Finally, CFD modeling of pressure fluctuations was performed on sand and cotton-sand fluidized beds operating at inlet velocities ranging from 1.0-9.0Umf with the objective of predicting characteristic features of bubbling, slugging, and turbulent fluidization regimes. It was determined that the fluidized bed can be modeled using MUSCL discretization and the Ahmadi turbulence model. Three-dimensional sand fluidized beds were simulated for different fluidization regimes. Fluidized beds for all the regimes behaved as second-order dynamic systems. Bubbling fluidized beds showed one broad peak with a maximum at 2.6 Hz while slugging and turbulent showed two distinct peaks. It was observed that the peak at low frequency increased in magnitude as the flow transitioned from a slugging to a turbulent fluidization regime. CFD simulations of fluidized beds with the purpose of studying pressure fluctuations have demonstrated to be a useful tool to obtain hydrodynamic information that will help determine the fluidization regime. Prediction of slugging and turbulent fluidization regimes using CFD have not been reported to date. The work presented here is the first of its kind and can be an important advantage when designing a reactor and evaluating different operation conditions without the need to test them in a pilot plant or a prototype. / Ph. D.

Fluidized bed reactor technology has been widely adopted within the industry as vital component for numerous manufacturing, power generation and gasification processes due to its enhanced mixing characteristics. Computational modeling of fluidized bed hydrodynamics is a significant challenge that has to be tackled for increasing predictive accuracy. The distributor plate of a fluidized bed is typically modeled using a uniform inlet condition, when in reality the inlet is non-uniform inlet. The regions of bed mass that do not fluidize because of the non-uniform inlet conditions form deadzones and remain static between the jets. A new model based on the mass that contributes to the pressure drop is proposed to model a fluidized bed, and has been investigated for a cylindrical reactor for glass beads, ceramic single solids particles, and glass-ceramic, and ceramic-ceramic binary mixtures. The adjusted mass model was shown to accurately predict fluidization characteristics such as pressure drop and minimum fluidization velocity. The effectiveness of the adjusted mass model was further illustrated by applying it to fluidized beds containing coal, switchgrass, poplar wood, and cornstover biomass particles and coal-biomass binary mixtures. The adjusted mass model was further analyzed for bed expansion heights of different mixtures, and for solids distribution by analyzing the solids volume fraction. The effect of increasing the percent biomass in the mixture was also investigated. To further model the non-uniform inlet condition, two different distributor configurations with 5 and 9 jets was considered for a quasi-2D bed, and simulations were performed in both 2D and 3D. Fluidization characteristics and mixing of the bed were analyzed for the simulation. Furthermore, the deadzones formed due to multiple jet configurations of the distributor are quantified and their distributions over the plate were analyzed. / Ph. D.

A cold-flow vibated-bed microreactor system, operating at the room temperature and atmospheric pressure, was built and tested. The purpose of this microreactor was to simulate gas- and solid-mixing in a hot-flow microreactor system. The latter is being developed to study carbon deposition rates for continuous Fischer-Tropsch synthesis from a low H₂:CO gas with rapid switching of catalyst between gas atmospheres. The cold-flow microreactor consisted of three chambers with vertical sliding baffles that shift catalyst between the smaller, center reaction chamber and two outer chambers. The results show that the solid mixing within each chamber is essentially complete within one second after transfer of catalyst. The solid mixing was independent of gas flow and gas flow rate. Results of gas-mixing studies show that gas transfer between chambers of the microreactor was due to the transfer of gas within the interstices of transferred catalyst particles. During rapid baffle-switching intervals, complete gas mixing within each chamber occurred. The amount of gas transferred from the center chamber to each outer chamber was nearly constant and increased only slightly with feed gas rate to the center chamber. For the gas feed rates tested, the percentage of gas fed to the center chamber that transferred to each outer chamber was low, ranging from 1.2 to 4.9 percent. The results of this study are significant to the further development of the "sliding-baffle" microreactor for continuous Fischer-Tropsch synthesis, from a low H₂:CO gas. The microreactor will give important information on the rate of carbon deposition in a system that switches catalyst between two gas atmospheres. / M.S.

Reclaimed surface mined soils in Appalachia are typically infertile and must be amended for optimum vegetative growth. Fluidized bed combustion residue (FBCR), a by-product of coal-fired power plants, has high levels of Ca, S, Zn, Fe, and Al, and 50% of the neutralizing capacity of limestone. Three treatments were applied to three replicated .81 ha reclaimed mine pastures: control (no amendment), 6760 kg FBCR/ha, and 3380 kg limestone/ha. Based on forage availability, six steers were rotationally grazed on pastures receiving each treatment. Steers were weighed and blood samples collected at 14-d intervals and all animals were sacrificed for tissue sampling at the end of the 114-d trial. Amendment with FBCR or limestone increased soil pH (P < .05) above control levels. Forage yield and steer gain were not significantly affected by treatment. Forage samples collected during the trial indicated that FBCR and limestone amendments elevated forage ash, Ca, Mg, S, Cu and Ca:P ratio (P < .05). Cellulose and NDF were depressed in forage grab samples collected from FBCR- and limestone-amended pastures. The forage sampled the following spring was lower in hemicellulose, Zn, un and Ni; and higher in ash, Ca, S, the Ca: P ratio in the FBCR- and limestone-amended pastures. Mean serum mineral levels of steers were not affected by pasture treatment. The blood packed cell volume was higher in cattle grazing FBCR-amended pastures. Liver levels of Fe, H, Hi and Na were lower in cattle on pastures amended with FBCR or limestone. Bile levels of Mn were depressed in cattle grazing FBCR~ and limestone-amended pastures. The level of Cu in the liver and serum was at deficiency levels and was not detectable in bile, regardless of treatment. Higher kidney levels of Ca, Hg and P were recorded for steers grazing FBCR- and limestone-amended pastures. Hair Zn was higher in cattle grazing the FBCR- and limestone- treated pastures. Rib Cr and long bone Cd levels were lower in animals grazing the limestone- and FBCR-treated pastures. This study suggests that FBCR amendment enhances nutrient quality of forage and mineral status of animals at least as well as limestone application to acidic reclaimed mine pastures. / Ph. D. / incomplete_metadata

Yes / The biomass gasification process is widely accepted as a popular technology to produce fuel for the application in gas turbines and Organic Rankine Cycle (ORC). Chemical reactions of this process can be separated into three reaction zones: pyrolysis, combustion, and reduction. In this study, sensitivity analysis with respect to three input parameters (gasification temperature, equivalence ratio, and steam-to-biomass ratio) has been carried out to achieve energy self-sufficient conditions in a steam gasification process under the criteria that the carbon conversion efficiency must be more than 70%, and carbon dioxide gas is lower than 20%. Simulation models of the steam gasification process have been carried out by ASPEN Plus and validated with both experimental data and simulation results from Nikoo & Mahinpey (2008). Gasification temperature of 911 °C, equivalence ratio of 0.18, and a steam-to-biomass ratio of 1.78, are considered as an optimal operation point to achieve energy self-sufficient condition. This operating point gives the maximum of carbon conversion efficiency at 91.03%, and carbon dioxide gas at 15.18 volumetric percentages. In this study, life cycle assessment (LCA) is included to compare the environmental performance of conventional and energy self-sufficient gasification for steam biomass gasification. / Financing of this research was supported by the Thailand Research Fund (TRF) under Grant Number PHD57I0054 and the Institutional Research Grant by the Thailand Research Fund (TRF) under Grant Number IRG 5780014 and Chulalongkorn University, Contact No. RES_57_411_21_076.

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