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Thesis PlanB (M.S.)--University of Wisconsin--Stout, 2009. / Includes bibliographical references.

Over the past few decades, combustion of fossil fuels has released greenhouse gases such as CO2 and NOx into the atmosphere. It has been realized that a mean temperature increase of the Earth, also known as global warming, has resulted from the increase of CO2 concentration in the air. Hence, there is a growing tendency to establish novel methods of burning fossil fuels in order to mitigate CO2 concentration. Chemical Looping Combustion (CLC) is a method of burning fuel with inherent separation of CO2 while curbing the formation of NOx, typically by circulating an oxygen carrier between an air (oxidation) reactor and a fuel (reduction) reactor. An oxygen carrier, mainly a metal oxide, circulates between the reactors providing the oxygen for conversion of fuel to CO2 and H2O. Thus, having a pure CO2 stream, CO2 sequestration becomes economically feasible. Fe2O3, due to its availability and properties, could be an apposite oxygen carrier for CLC. Reaction kinetics of reduction of Hematite with methane, in the absence of gaseous oxidant, was studied. Temperature Program Reduction (TPR) experiments were carried out in a fixed bed tubular reactor. Reduction gas was composed of 15% methane and 85% argon. Thermogravimetric Analysis (TGA) was carried out on TPR products using air as the oxidant. Iron oxide samples were analyzed through X-ray diffraction (XRD) analysis and scanning electron microscopy. Two-stage reduction of iron oxide was observed: Fe2O3 reduced to Fe3O4 and then reduced to FeO. The activation energy of each stage was calculated from Kissinger’s method. For the first and second stage of reduction the activation energies were 10.58±0.86 and 25.77±0.83 kJ/mol, respectively. In addition, different kinetic models were assumed and compared to the actual data. A random nucleation mechanism can be assigned to the first stage and a two-dimensional diffusion mechanism can be assigned to the second stage of the reduction.

Carbon capture and storage technologies are required in order to reduce greenhouse gas emissions, while continuing to utilize existing fossil-fueled power generation stations. Of the many developing post-combustion CO2 capture technologies, calcium looping appears promising due to its high thermal efficiency, technical feasibility at commercial-scale, and low sorbent cost. Calcium looping has now been performed at the larger-scale, but there is still a significant quantity of information about sorbent performance, the fate of trace pollutant emissions (specifically SO2 and HCl), dual fluidized bed operating configurations, and impact of realistic operating conditions that still needs to be determined. Based on an economic analysis of the process, three key parameters serve to have the largest potential economic impact: (1) the sorbent deactivation rate, (2) the Ca/C molar ratio, and (3) the rate of sorbent attrition. Therefore, a series of bench-scale, pilot-scale, and continuous pilot-scale testing were conducted to not only explore these parameters from an improvement standpoint, but accurately determine them under conditions expected at the commercial-scale. The presence of HCl did not have a significant impact on sorbent performance provided that steam is present during calcination, although issues with downstream corrosion could be a factor. High CO2 partial pressures during calcination, coupled with high temperatures and the presence of SO2, resulted in dramatically lower cyclic carbonation conversions and a reduced high CO2 capture efficiency regime. Continuous pilot-scale testing generated realistic, and more detrimental, values for sorbent carrying capacity, Ca/C molar ratio, sorbent make-up rates, and rate of sorbent elutriation, that can now be utilized for techno-economic evaluations and scale-up of the technology.

On May 11th, 2019, atmospheric CO2 levels reached 415 ppm, a number 40% higher than the maximum level ever reached in the 800 000 years prior to the Industrial Revolution. This rise can be directly attributed to human activity, and has been linked to global temperature increase and climate change. Net CO2 emissions continue to rise as economies grow, and in 2018 global emissions reached 37.1 Gt. In order to reach the climate targets identified in the 2015 Paris Agreement, some scientists estimate that the world will need to attain net-zero anthropogenic greenhouse gas (GHG) emissions by 2050. Achieving this goal will require deployment of multiple technologies across multiple sectors. Of particular importance will be reducing or eliminating emissions associated to energy production via combustion of fossil fuels, which account for over 80% of CO2 emissions in G20 countries. One method of achieving this is to displace fossil fuel electricity generation with renewable source generation. Canada currently has 12 GW of installed wind capacity, and although it is the country’s fastest-growing source of renewable electricity, widespread deployment is inhibited by technical challenges including the time variability and geographic dispersion of sources. A potential solution to overcome the challenges facing integration of renewables is grid-scale energy storage. Many storage technologies currently exist at various levels of maturity. Although currently low on the development scale, thermochemical energy storage (TCES) has gained significant interest due to its potential to offer low-cost, short- or long-term storage of high-temperature heat using non-toxic, abundant materials. Several recent works have focused on the potential to pair the calcium looping (CaL) process, which exploits the reversible calcination of calcium carbonate, with concentrated solar power (CSP). This would enable CSP to provide continuous power to the grid while receiving discontinuous solar input, and recent projects have predicted storage cycle efficiencies in the range of 38-46%. As an extension of the work done to date, this project proposes a novel configuration of the CSP-CaL process which may offer advantages over other proposed configurations, including a reduction in process equipment requirements, elimination of pressure differentials between vessels, and a reduction in compression duty during the energy discharge period. A process simulation of the proposed system shows that it is capable of offering comparable storage cycle efficiencies, with the overall efficiency being strongly dependent on the residual conversion of calcium oxide in the carbonator as well as on the efficiencies of the power cycles employed to discharge the stored energy. In addition to the technical challenges that may come with this type of system, social and economic barriers may arise due to the fact that it will require large-scale storage of CO2, mining of natural limestone, and potentially large and complex facilities. All of these challenges must be considered and addressed in order to achieve deployment of this technology within Canada and around the world.

Global warming and climate changing are serious problems challenging humanity, therefore important steps needed to be taking to neutralize such challenge. From the last century huge amount of carbon dioxide released to atmosphere cause huge damages to our globe. Technologies such as oxycombustion and chemical looping combustion had been discussed to capture and sequestration carbon dioxide at lower cost. Separation air from fuel using chemical looping or separation nitrogen from air using oxygen transport membrane (OTM) then combust pure oxygen with fuel are the main step to capture carbone dioxide in less expensive method. Each technology had its own drawback, therefore, to overcome these drawbacks an integrated system is proposed combined oxycombustion, chemical looping and OTM technologies into one system. This work aimed to model and simulate an integrated system in single reactor using liquid Antimony and Antimony trioxide as an oxygen carrier to pick up oxygen from the OTM and reduce fuel using natural circulation due to density difference between metal and metal oxide. Heat is being released inside the reactor due to exothermic oxidation reaction and temperature is increased. The temperature profile is studied in all reactor zones with respect to oxidation and reduction rate, operation temperature, metal viscosity and radiation effect. The result show that the system had a good potential to transfer heat generated from the oxidation and transfer to other zones, in which heat can be utilized and been used for heating water or generate steam.

Production of hydrogen from biomass steam gasification can be enhanced by using calcium oxide sorbents for CO2 capture in the gasifier. Calcium looping suffers from two main drawbacks: the need for high-purity oxygen in order to regenerate the sorbent under oxy-fuel combustion conditions and the loss of sorbent reactivity over several cycles due to sintering of pores upon calcination at high temperatures. One method of addressing the issue of oxygen supply for calcination in calcium looping is to combine the calcium looping and chemical looping processes, where the heat produced by the reduction of an oxygen-carrier by a fuel such as natural gas or gasification syngas, drives the calcination reaction. The technologies can be integrated by combining an oxygen carrier such as CuO with limestone within a composite pellet, or by cycling CuO and limestone within distinct particles. The goal of this project is thus to investigate the different sequences of solids circulation and the cyclic performance of composite limestone-CuO sorbents under varied operating conditions for this novel process configuration. Using a thermogravimetric analyzer (TGA), it was found that using composite CaO/CuO/alumina-containing cement pellets for gasification purposes required oxidation of Cu to be preceded by carbonation (Sequence 2) as opposed to the post-combustion case where the pellets are oxidized prior to carbonation (Sequence 1). Composite pellets were tested using Sequence 2 using varying carbonation conditions over multiple cycles. While the pellets exhibited relatively high carbonation conversion, the oxidation conversion underwent a decrease for all tested conditions, with the reduction in oxygen uptake particularly drastic when the pellets were pre-carbonated in the presence of steam. It appears that the production of a layer of CaCO3 fills up the pellets pores, obstructing the passage of O2 molecules to the more remote Cu sites. Limestone-based pellets and Cu-based pellets were subsequently tested in separate CaL and CLC loops respectively to assess their performance in a dual-loop process (Sequence 3). A maximum Cu content of 50% could be accommodated in a pellet with calcium aluminate cement as support with no loss in oxidation conversion and no observable agglomeration.

Amin Bagheri, for the Master of Science degree in MECHANICAL ENGINEERING AND ENERGY PROCESSES, presented on June 23, 2014, at Southern Illinois University Carbondale TITLE: STUDYING THE MAGNETIC SEPARATION OF OXYGEN CARRIER IN COAL DIRECT CHEMICAL LOOPING MAJOR PROFESSOR: Dr. Tomasz S. Wiltowski Magnetic separation of oxygen carrier from coal after combustion by-products was studied. Samples were prepared using iron metal, hematite and magnetite mixed with quartz in three different concentrations. A variable speed and magnetic field intensity separator unit was designed and constructed to prove the concept of magnetic separation. The unit went through trial and error steps to improve overall functionality and efficiency including belt material selection, electromagnet selection, feeder and collector buckets, drive drum and idler manufacturing. Prepared samples were tested in different velocities and magnetic field intensities.

The focus of this work is to investigate the feasibility of oxygen extraction from CO2 by doped ceria in chemical looping process. In order to increase the oxygen capacity and oxygen release rates, Cerium- based oxygen carriers are doped with ZrO2. Additionally, the zirconia-doped ceria is modified by iron and copper to boost the oxygen release in the fuel reactor. It should be noted that the level of doping allows the solids to maintain the cubic fluorite structure of CeO2. The redox activity of oxygen carriers is studied in order to determine the most promising material due to the oxygen transfer capacity and methane conversion. The chemical looping dry reforming in a quartz fixed-bed reactor is carried out in two steps. In the first step, the oxygen carriers are reduced by methane through the combustion reaction. In the second step, CO2 is used for oxidation of reduced metal oxides. The obtained results at different doping levels were compared to determine the optimal oxygen carrier. The results indicate that doping ceria can boost the reactivity with methane and enhance the methane conversion during combustion reaction. CeO2 modified by Fe presents a progress in both oxygen release and uptake with an increase in oxygen capacity of metal oxide. However, zirconia and copper ceria show different effect on reduction and oxidation. This means that zirconia doped ceria results in an increase in oxygen release during reduction and decrease in oxygen uptake during oxidation with CO2. In contrast, addition of copper to ceria metal oxides shows a negative effect on oxygen release, while it enhances the ability of oxygen uptake. Out of all mixed cerium oxides investigated in this study, cerium oxide containing 10% mole iron is determined as the most promising oxygen carrier for CLDR due to the methane conversion, facilitating oxygen release, increasing the level of reduction and improving the oxidation uptake of the metal oxide in the reaction with CO2.

A current educational practice in grouping students is looping. Looping involves teachers remaining with the same students for two or more years. This practice was implemented in the elementary school in this study. This is an evaluation of looping in the first and second grades. The study has both qualitative and quantitative components. An administrator, teachers, and students in four looping and four non-looping cohorts were participants. Criterion variables were attendance; achievement in English, mathematics, science, and history and social science; instructional time; relationships among students; and relationships between teachers and students. A t-test was used to test for differences between looping and non-looping cohorts for attendance and achievement. Teachers used a log to record instructional time spent reviewing previously learned skills and teaching new skills in mathematics. Observations were conducted to describe the relationships among students and between teachers and students. There were no differences between looping and non-looping cohorts in attendance, instructional time, and achievement, except in history and social science, for one of the years studied. In that year, students in the looping cohort scored higher on the Standards of Learning test in history and social science than students in the non-looping cohort. Relationships among students were better in looping cohorts, and relationships between teachers and students appeared stronger in non-looping cohorts. / Ed. D.