Development and Characterisation of Oxygen-carrier Materials for Chemical-looping Combustion PDF Download
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Author: Paul Cho
Publisher:
ISBN: 9789172916050
Category :
Languages : en
Pages : 61
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Book Description
Author: Paul Cho
Publisher:
ISBN: 9789172916050
Category :
Languages : en
Pages : 61
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Book Description
Author: Wenting Hu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Mohammad Rezwanul Quddus
Publisher:
ISBN:
Category :
Languages : en
Pages : 326
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Book Description
In last decades, significant concerns have been raised regarding the global warming effects. To date, about one - third of the total anthropogenic CO2 emission results from power generation using fossil based fuel and CO2 is regarded as the main contributor to global warming. Therefore, technologies for efficient capture of CO2 are becoming of great value. In this respect, Chemical-Looping Combustion (CLC) has received significant attention as a promising technology facilitating concurrent CO2 capture and power generation. This non - conventional technique employs a solid carrier, known as oxygen carrier, to supply oxygen and it facilitates the combustion process in absence of N2 diluted air. Therefore, the combustion products (CO2 and water) are easily separable without any extra downstream processing cost involved in other available alternatives. However, the non- vailability of suitable oxygen carriers still hinders the commercialization of CLC. This study, thus, deals with the development of a new mixed metallic oxygen carrier, Ni-Co/La-?-Al2O3. Several characterization techniques are used to evaluate the reactivity and stability of the prepared oxygen carriers under the industrial-scale conditions of a CLC processes. Apart from the beneficia l effects of La and Co, the reducibility and the structural properties of the prepared oxygen carriers are found to be influenced significantly by the different preparation methods used. N2 adsorption isotherms show that?-Al2O3 retains its structural int egrity under some specific preparation conditions. Reducibility as determined by consecutive temperature programmed techniques resembles the chemical properties of? - and?-Al2O3 for the other preparation techniques. However, no bulk phase change is detected for all the oxygen carriers studied using XRD. The SEM/EDX and H2 chemisorption analyses show the absence of metal agglomeration and suggest that the prepared oxygen carriers are highly stable under CLC operating conditions. The prepared oxygen carriers are also tested for reactivity, stability and fluidizability in the CREC Riser Simulator using multiple reduction/oxidation cycles with CLC fuel. Results obtained show expected reducibility, oxygen carrying capacity and stability. The solid-state kinetics of the reduction processes are developed using nucleation and nuclei growth model (NNGM) and unreacted shrinking core model (USCM). The NNGM model shows better adequacy over USCM in describing the mechanism of reduction process.
Author: Liang-Shih Fan
Publisher: John Wiley & Sons
ISBN: 1118063139
Category : Technology & Engineering
Languages : en
Pages : 353
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This book presents the current carbonaceous fuel conversion technologies based on chemical looping concepts in the context of traditional or conventional technologies. The key features of the chemical looping processes, their ability to generate a sequestration-ready CO2 stream, are thoroughly discussed. Chapter 2 is devoted entirely to the performance of particles in chemical looping technology and covers the subjects of solid particle design, synthesis, properties, and reactive characteristics. The looping processes can be applied for combustion and/or gasification of carbon-based material such as coal, natural gas, petroleum coke, and biomass directly or indirectly for steam, syngas, hydrogen, chemicals, electricity, and liquid fuels production. Details of the energy conversion efficiency and the economics of these looping processes for combustion and gasification applications in contrast to those of the conventional processes are given in Chapters 3, 4, and 5.Finally, Chapter 6 presents additional chemical looping applications that are potentially beneficial, including those for H2 storage and onboard H2 production, CO2 capture in combustion flue gas, power generation using fuel cell, steam-methane reforming, tar sand digestion, and chemicals and liquid fuel production. A CD is appended to this book that contains the chemical looping simulation files and the simulation results based on the ASPEN Plus software for such reactors as gasifier, reducer, oxidizer and combustor, and for such processes as conventional gasification processes, Syngas Chemical Looping Process, Calcium Looping Process, and Carbonation-Calcination Reaction (CCR) Process. Note: CD-ROM/DVD and other supplementary materials are not included as part of eBook file.
Author: Cheng Lung Chung
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages :
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This dissertation presents investigations of chemical looping technology as a transformative process for combustion of fossil fuels for power generation with CO2 capture. Specifically, the dissertation seeks to synthesize and characterize a low-cost iron-based oxygen carrier that can be employed in a commercial chemical looping combustion system with realistic material lifetime and adequate resistance to toxicity from pollutants from fossil fuels such as coal. Two secondary metal oxides (Al2O3 and TiO2) as support materials for Fe2O3 and their respective reaction-induced morphological changes are presented. A novel iron-based oxygen carrier was consequently identified to be sustainable over 3000 redox cycles in high temperatures (1000 °C) at the lab scale without chemical and physical degradation. Oxygen carrier of the same design also exhibited high resistance toward attrition from circulation and fluidization in two pilot-scale demonstration units under representative conditions. Tolerance of the active ingredients of the iron-based oxygen carriers against common toxic elements in the fossil fuel feedstock, such as alkaline and sulfur compounds from conversion of coal, through multiple fixed bed experiments under conditions representative of the counter-current moving bed reducer and thermogravimetric experiments up to 9000 ppm of H2S. The likelihood of agglomeration and interaction of alkaline metals (Na, K) with the iron-based oxygen carriers were found to be extremely low under normal operating conditions. Instead, proper distribution of coal was more crucial to avoid agglomeration caused by melting of SiO2. Sulfur deposition on iron-based oxygen carriers, although observed, was reversible through regeneration with air and did not result in degradation in the recyclability of the oxygen carriers. A potential pathway for sulfur emission via the combustor spent air was also identified. The sulfur emission and distribution of the Coal-Direct Chemical Looping (CDCL) 25 kWth sub-pilot unit which utilized the iron-based oxygen carriers was determined with a custom heat-traced gas sampling system. More than 69% of the total amount of atomic sulfur from high sulfur coal was converted to SO2 and H2S in the reducer flue gas stream while less than 5% was released as SO2 in the combustor spent air. The missing atomic sulfur in the balance was attributed to sulfur retained in coal ash as inorganic sulfur compounds. A flue gas clean-up system targeting both H2S and SO2 is therefore recommended to meet the quality of CO2-rich stream for transportation and sequestration in a commercial CDCL system. The projected sulfur emission in the combustor spent air was under the US EPA sulfur emission regulation safe to be released to the atmosphere without a costly acid removal system. The findings demonstrate the robustness of the CDCL system, together with the iron-based oxygen carriers, to handle high sulfur coal without severe performance and economic penalties.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Chemical Looping Combustion (CLC) is one promising fuel-combustion technology, which can facilitate economic CO2 capture in coal-fired power plants. It employs the oxidation/reduction characteristics of a metal, or oxygen carrier, and its oxide, the oxidizing gas (typically air) and the fuel source may be kept separate. This topical report discusses the results of four complementary efforts: (5.1) the development of process and economic models to optimize important design considerations, such as oxygen carrier circulation rate, temperature, residence time; (5.2) the development of high-performance simulation capabilities for fluidized beds and the collection, parameter identification, and preliminary verification/uncertainty quantification; (5.3) the exploration of operating characteristics in the laboratoryscale bubbling bed reactor, with a focus on the oxygen carrier performance, including reactivity, oxygen carrying capacity, attrition resistance, resistance to deactivation, cost and availability; and (5.4) the identification of kinetic data for copper-based oxygen carriers as well as the development and analysis of supported copper oxygen carrier material. Subtask 5.1 focused on the development of kinetic expressions for the Chemical Looping with Oxygen Uncoupling (CLOU) process and validating them with reported literature data. The kinetic expressions were incorporated into a process model for determination of reactor size and oxygen carrier circulation for the CLOU process using ASPEN PLUS. An ASPEN PLUS process model was also developed using literature data for the CLC process employing an iron-based oxygen carrier, and the results of the process model have been utilized to perform a relative economic comparison. In Subtask 5.2, the investigators studied the trade-off between modeling approaches and available simulations tools. They quantified uncertainty in the high-performance computing (HPC) simulation tools for CLC bed applications. Furthermore, they performed a sensitivity analysis for velocity, height and polydispersity and compared results against literature data for experimental studies of CLC beds with no reaction. Finally, they present an optimization space using simple non-reactive configurations. In Subtask 5.3, through a series of experimental studies, behavior of a variety of oxygen carriers with different loadings and manufacturing techniques was evaluated under both oxidizing and reducing conditions. The influences of temperature, degree of carrier conversion and thermodynamic driving force resulting from the difference between equilibrium and system O2 partial pressures were evaluated through several experimental campaigns, and generalized models accounting for these influences were developed to describe oxidation and oxygen release. Conversion of three solid fuels with widely ranging reactivities was studied in a small fluidized bed system, and all but the least reactive fuel (petcoke) were rapidly converted by oxygen liberated from the CLOU carrier. Attrition propensity of a variety of carriers was also studied, and the carriers produced by freeze granulation or impregnation of preformed substrates displayed the lowest rates of attrition. Subtask 5.4 focused on gathering kinetic data for a copper-based oxygen carrier to assist with modeling of a functioning chemical looping reactor. The kinetics team was also responsible for the development and analysis of supported copper oxygen carrier material.
Author: Chern Yean Sim
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
It is well known that carbon dioxide (CO2) is a greenhouse gas that contributes to global warming. Nowadays, a third of the worldwide anthropogenic CO2 emissions arise from fossil fuel fired power production. Meanwhile, fossil fuels continue to be the main source of energy for the foreseeable future. The increasing threat posed by enhanced global warming, as well as the requirement for sustainable energy supplies around the world, have led to the development of several novel technologies to produce clean energy from fuels. Among these new technologies is chemical looping combustion (CLC) that uses a solid metal oxide (oxygen carrier) to react with fuels. This technology has the potential advantage that it produces a pure stream of CO2 that can then be sequestrated. In a CLC process, the oxygen carrier is reduced by fuels in one reactor while being oxidised by air in a separate reactor. As the oxygen carrier circulates through the system, it is subjected to morphological and compositional changes such as sintering, attrition and reactions between various metal oxides and fuels. These changes tend to cause the reactivity of the oxygen carrier to decrease over time. The main objective of this PhD study was to investigate and characterise the morphological and compositional changes of the oxygen carrier particles after they have undergone multiple reduction oxidation cycles in a CLC system. A single fluidised bed system was used in this study. Fuel was fed into a bed of oxygen carrier consisting of mechanically mixed iron oxide or wet impregnated copper oxide supported on alumina. The bed was fluidised by a stream of CO2 and/or steam. Pyrolysis gases from the fuel gasification process reduced the oxygen carrier while forming char in the bed. Thus char was oxidised and the oxygen carrier was regenerated when the fluidising gas was switched to air. Five different types of fuels were initially used in the tests. They were lignite coal, lignite char, activated carbon, US bituminous coal and Taldinski bituminous coal. The rates of gasification of the bituminous coal and activated carbon were much slower than those of the lignite coal and lignite char, resulting in an unfavourably large accumulation of char during the reduction stage. Subsequent experiments were conducted with UK bituminous coal to determine the effect of ash on the oxygen carrier particles over a long operational period. The series of analytical tests included; stereo microscopy, porosimetry analysis, X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy with an energy dispersive system (SEM/EDS) and Page ii X-ray photoelectron spectroscopy (XPS). Tests were performed on both the fresh and reacted oxygen carriers. Analytical results showed that when the pyrolysis gases react with the oxygen carrier, mineral matter left behind from the gasification process will deposit on the surface of the particles and diffuse into the core of the particles. This is due to the fact that mineral matter has a higher melting point compared to iron oxide and copper oxide. Iron oxide and copper oxide diffusing to the surface of the particles will replace those that are lost via attrition. As a result, the composition of the surface of these particles remains relatively unchanged. As more mineral matter diffuses into the core of the oxygen carrier particles, they can segregate metal oxide molecules located at the surfaces from those located at the core of the particles. When this occurs, there is a possibility that the segregated material formed will reduce the ability of oxygen to diffuse to the surface of the oxygen carrier particles. Hence this will reduce the conversion of the pyrolysis gases. This will thus lead to the reduction in the conversion of the pyrolysis gas and possibly in the deactivation of the oxygen carrier. It was found that the support structure played a key role in maintaining the structural integrity of the metal oxide particles during repeated reduction and oxidation cycles. Experimental results showed that the rate of attrition initially increases with time indicating that the oxygen carrier structure weakens as it interacts with the mineral matter in ash. Results from this research study have shown that the semi-batch chemical looping combustion of solid fuels is feasible provided reactive fuels that produce a large quantity of pyrolysis gases are used. Less reactive fuels will lead to the accumulation of a large inventory of char in the bed. The slow rate of gasification of char will then result in a lower carbon capture efficiency. In order to operate a semi-batch chemical looping combustion system with solid fuel, temperatures of above 1000°C are most likely required. However, this would exclude metal oxides with low melting points to act as potential oxygen carriers and may cause other problems such as ash fusion. A possible solution is to gasify the solid fuels in a separate reactor and channel the resulting pyrolysis gases into the chemical looping combustion system.
Author: Ronald W. Breault
Publisher: John Wiley & Sons
ISBN: 3527342028
Category : Business & Economics
Languages : en
Pages : 488
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Book Description
This comprehensive and up-to-date handbook on this highly topical field, covering everything from new process concepts to commercial applications. Describing novel developments as well as established methods, the authors start with the evaluation of different oxygen carriers and subsequently illuminate various technological concepts for the energy conversion process. They then go on to discuss the potential for commercial applications in gaseous, coal, and fuel combustion processes in industry. The result is an invaluable source for every scientist in the field, from inorganic chemists in academia to chemical engineers in industry.
Author: Paul Fennell
Publisher: Elsevier
ISBN: 0857097601
Category : Technology & Engineering
Languages : en
Pages : 467
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Book Description
Calcium and Chemical Looping Technology for Power Generation and Carbon Dioxide (CO2) Capture reviews the fundamental principles, systems, oxygen carriers, and carbon dioxide carriers relevant to chemical looping and combustion. Chapters review the market development, economics, and deployment of these systems, also providing detailed information on the variety of materials and processes that will help to shape the future of CO2 capture ready power plants. - Reviews the fundamental principles, systems, oxygen carriers, and carbon dioxide carriers relevant to calcium and chemical looping - Provides a lucid explanation of advanced concepts and developments in calcium and chemical looping, high pressure systems, and alternative CO2 carriers - Presents information on the market development, economics, and deployment of these systems
Author: Viktor Hacker
Publisher: Elsevier
ISBN: 0128115378
Category : Technology & Engineering
Languages : en
Pages : 298
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Book Description
Fuel Cells and Hydrogen: From Fundamentals to Applied Research provides an overview of the basic principles of fuel cell and hydrogen technology, which subsequently allows the reader to delve more deeply into applied research. In addition to covering the basic principles of fuel cells and hydrogen technologies, the book examines the principles and methods to develop and test fuel cells, the evaluation of the performance and lifetime of fuel cells and the concepts of hydrogen production. Fuel Cells and Hydrogen: From Fundamentals to Applied Research acts as an invaluable reference book for fuel cell developers and students, researchers in industry entering the area of fuel cells and lecturers teaching fuel cells and hydrogen technology. - Includes laboratory methods for fuel cell characterization and manufacture - Outlines approaches in modelling components, cells and stacks - Covers practical and theoretical methods for hydrogen production and storage
