Exploring Strategies for Syngas Generation Using Calcium-iron Based Oxygen Carriers in Chemical Looping Systems PDF Download

Author: Vedant Shah
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 0

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Book Description
Historically, fossil fuels have dominated the energy generation domain and it is projected that they will continue to remain a dominant source of energy for the foreseeable future. Although essential, the usage of fossil fuels has deemed to be deleterious for both human health and the surrounding environment as the release of anthropogenic CO2 because of burning fossil fuels has been asserted as one of the leading causes of global warming and climate change. It is important to understand that fossil fuels are not only used for energy generation, but they also contribute significantly towards the production of various industrially important chemicals and derivatives. Syngas and hydrogen, two of the petrochemical industry’s most sought-after commodities are typically generated using fossil fuels, wherein both gaseous and solid fossil fuels can be employed for syngas and hydrogen generation. Naturally occurring carbonaceous sources (fossil fuels) such as natural gas, shale gas, coal, etc. are reformed/gasified in the presence of steam/CO2/molecular O2 to generate syngas, which is processed further for generating hydrogen. These processes however collectively suffer from certain limitations including high endothermic heat requirement, placement of amine-based units for capturing CO2 generated across various operations in the process, catalyst deactivation due to coking, and the requirement of a highly energy and cost-intensive cryogenic air separation unit.

Author: Sourabh Gangadhar Nadgouda
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages :

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Book Description
The importance of syngas and hydrogen (H2) along with the abundance of natural gas underlines the need for an energy efficiency and economical means of syngas and H2 production from natural gas. The conventional processes for syngas and H2 production consist of several unit operations and are very energy intensive. Additionally, these processes have a lot of CO2 emissions which is a major drawback considering the concern for global warming cause by greenhouse effect. Chemical looping process is an attractive alternative to the conventional processes. It has better exergy efficiency and reduces the downstream processing steps by inherent separation of the products. The reducing and oxidizing gases are either spatially or temporally separation which minimizes the safety hazard of forming a flammable mixture at high temperature. Despite several research efforts in application of chemical looping for syngas and H2 production there still exists scope for improvement in terms of syngas yield and overall process efficiency. In this thesis, the three major aspects of chemical looping process: oxygen carriers, reactor configuration and process configuration, are explored for strategies to enhance syngas and H2 yield. A co-current moving bed reactor configuration is simulated experimentally and theoretically for copper-iron oxygen carriers in addition to testing 5 different process configurations for the overall system. CH4 conversion and dry syngas purity of 99.5% and 97.5%, respectively, is observed in a U-tube fixed bed reactor where a co-current moving bed reactor solids profile is mimicked using copper oxide (20 wt%) - iron oxide (60 wt%) - aluminium oxide (20 wt%) oxygen carrier. The net H2 production is higher by 28% and effective thermal efficiency is 10% more than that of autothermal reforming process for the best performing process configuration. A different process configuration is also shown to have higher syngas yield than the conventional two reactor chemical looping reforming system with iron oxide-magnesium aluminate as the oxygen carrier. Process simulations in ASPEN Plus software are performed under different heat transfer, pressure and co-injection conditions to understand the benefit offered by the improved process configuration. Finally, an improvement in H2 production and, subsequently, cold gas efficiency for a chemical looping combustion system is observed using a staged H2 separation approach in the oxidizer reactor. H2 separation module was simulated in ASPEN Plus software and several combinations of separation modules and oxidizer reactor were screened for highest H2 production. A maximum cold gas efficiency of about 79%, which is 7% and 1.5% higher than the steam methane reforming process (Department of Energy baseline case) and traditional chemical looping combustion system, respectively.

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: Liang-Shih Fan
Publisher: John Wiley & Sons
ISBN: 1118063139
Category : Technology & Engineering
Languages : en
Pages : 353

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Book Description
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: Calin-Cristian Cormos
Publisher: Elsevier Inc. Chapters
ISBN: 0128085320
Category : Science
Languages : en
Pages : 18

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Book Description
Reducing greenhouse gas emissions generated from energy sector in the following years is a compulsory step to the transition to low carbon resource efficient economy. Among various methods to reduce CO2 emissions, Carbon Capture and Storage (CCS) technologies have a special importance. A promising carbon capture method to be applied in energy conversion processes for reducing the energy penalty associated with carbon capture is based on chemical looping systems. This paper investigates CO2 capture based on chemical looping systems suitable to be applied in an IGCC plant for energy vectors poly-generation with emphasis on hydrogen and power co-generation case. The coal-based IGCC cases produce about 400 – 600 MW net electricity and a flexible hydrogen output from zero up to 150 MW hydrogen (based on hydrogen lower heating value) with almost total carbon capture rate of the used fossil fuel. A particular accent is put in the paper on the assessment of process integration issues of gasifier island and syngas conditioning line with the chemical looping unit, mathematical modeling and simulation of whole plant, thermal and power integration of chemical looping unit in the whole IGCC plant (using pinch analysis) and discussing quality specifications for captured CO2 stream considering storage in geological formations or using for EOR.

Author: Dikai Xu
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 155

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Book Description
The chemical looping partial oxidation process is developed for the efficient conversion of gaseous and solid fuels into syngas via partial oxidation. The chemical looping partial oxidation process converts the fuels into high purity syngas with flexible H2:CO ratio that is suitable for downstream fuel or chemical synthesis. In the chemical looping partial oxidation process, the fuels are partially oxidized in the reducer reactor by the oxygen carrier to generate high purity syngas. The reduced oxygen carrier is regenerated in a fluidized bed combustor via the oxidation reaction with air. Compared to the conventional syngas generation processes, the chemical looping partial oxidation process eliminates the need for additional steam or molecular oxygen from an air separation unit (ASU), resulting in an increased cold gas efficiency and decreased fuel consumption. The chemical looping partial oxidation process features the combination of an iron-titanium composite metal oxide (ITCMO) oxygen carrier and a co-current gas-solid moving bed reducer reactor. The ITCMO oxygen carrier is selected for the chemical looping partial oxidation process due to its desired thermodynamic and kinetic properties. Theoretical analysis aided by a modified Ellingham Diagram illustrates that syngas production is thermodynamically favored in the presence of ITCMO oxygen carrier. The co-current moving bed reducer design provides a desirable gas-solid contacting pattern that minimizes carbon deposition while maximizing the syngas yield. Experimental studies in a fixed bed reactor and a bench scale reactor successfully demonstrate the production of high purity syngas from methane and biomass with the combination of moving bed reducer and ITCMO oxygen carrier. Further scale-up of the chemical looping partial oxidation process is demonstrated in an integrated sub-pilot scale reactor system using non-mechanical gas sealing and solid circulation devices. A dynamic modeling scheme is developed for studying the transient behavior and the control of the chemical looping system. A hierarchical control system based on sliding mode control concept is developed for the chemical looping technologies to simplify process operation.

Author: Mandar V. Kathe
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
The following study entails process simulations and techno-economic analysis based investigations of novel chemical looping partial oxidation processes. The moving bed reactor system analyzed in this dissertation provides chemical looping technologies several intrinsic advantages over conventional energy processing schemes. Chapter 2 focusses on optimizing the counter-current moving bed chemical looping system for H2 production from natural gas. The chemical looping process for H2 production from natural gas is optimized based on isothermal thermodynamic limits of an iron-based counter-current moving bed reactor system. The iso-thermal analysis is followed by a parametric sensitivity for energy balance for satisfying the auto-thermal heat balance. This is completed by computing temperature swings based on a net heat duty calculation for individual chemical looping reactors. Overall the chemical looping process is shown to have a cold gas efficiency of 77.6% (HHV basis) and an effective thermal efficiency of 75.1% (HHV basis), both of which are significantly higher than the baseline case. Chapter 3 discusses the Shale gas to Syngas process for integration into a Gas to Liquid fuel (GTL) plant. Following the methodology for an isothermal and an adiabatic analysis from Chapter 2, Chapter 3 identifies a suitable auto-thermal operating condition for the chemical looping reactors. The process simulation model is used to derive cost estimates based on standard engineering assumptions and completes a sensitivity analysis for several important economic parameters. The STS process is shown to require significantly lower natural gas feedstock than the conventional process baseline for producing the same amount of liquid fuels. The STS process lowers the capital cost investment for the syngas production section of a GTL plant by over 50% and if commercialized can be disruptive to liquid fuel production markets. Chapter 4 discusses the Coal to syngas (CTS) process for its technical and economic performance when integrated into a 10,000 tpd methanol plant. This chapter details the equipment sizing philosophy and cost methodology used in this dissertation for calculating economic performance of the novel processes developed. Further, sensitivity studies which analyze effect of economic parameters like the capital charge factor, natural gas price are considered to identify the critical technology parameters necessary to be de-risked for pilot scale and commercial scale operation of the CTS technology. The CTS process reduced the coal consumption by 14% for the same amount of methanol production. The CTS process also reduced the methanol required selling price by 21% over the corresponding baseline case with greater than 90% carbon capture. Chapter 5 discusses the two reducer chemical looping configurations and the fixed bed chemical looping configurations. The two reducer chemical looping configurations provide the flexibility for designing two different reducer reactors, each optimized to a specific fuel feedstock. The two reducer chemical looping configurations can improve over thermodynamic performance of a single reducer chemical looping configuration by providing the flexibility to get high solids conversion with high fuel conversions. The fixed bed operating strategy opens up ways to operate iron-based chemical looping system without solids circulation for high-efficiency production of syngas.

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: Ankita Majumder
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 204

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Book Description
Chemical looping is an efficient, economic and sustainable means for electricity and/or chemicals production with inherent CO2 sequestration ability. Oxygen carriers play a crucial role in the successful operation of a chemical looping system as their physical and chemical properties dictate the fuel conversion efficiency of the system. They are expected to undergo multiple redox cycles while maintaining their reactivity and mechanical strength in order to improve the overall process economics for commercial viability. This research investigates the behavior of oxygen carriers under different reactive conditions and evaluates their feasibility for biomass chemical looping systems. The reduction kinetics of OSU’s iron titanium complex metal oxide (ITCMO) oxygen carrier particles are investigated at elevated pressures with H2 and CH4 for application in OSU’s Shale gas-to-Syngas process. Under CH4, there is almost a 5-fold increase in the reduction rate with an increase in pressure from 1 to 10 atm. Solid characterization revealed increased porosity and surface area at elevated pressures. Faster reaction kinetics at higher pressures can translate into increased processing capacity, reduced reactor sizing, and decreased capital costs. The steam to H4 conversion efficiency of Fe2O3 based oxygen carriers using Al2O3, MgAl2O4 and TiO2 as support materials is investigated in a fixed bed for chemical looping H2 generation. All supported-Fe2O3 based oxygen carriers exhibited >70% steam conversion, close to thermodynamic predictions. Due to its ability to not form complexes with the active material, MgAl2O4 -supported Fe2O3 was selected for further investigation. Thermogravimetric studies with steam oxidation exhibited excellent recyclability and no significant drop in reactivity. MgAl2O4 -supported Fe2O3 also exhibited enhanced steam oxidation kinetics at elevated pressures. Tar derived from biomass pyrolysis is a major concern for biomass thermochemical conversion processes. For biomass fueled chemical looping processes, it is important to evaluate effects of tars on the oxygen carriers. Fixed bed experiments demonstrated that OSU’s ITCMO oxygen carriers have reasonable reactivity for cracking most biomass-derived tar components. To further enhance the tar cracking ability of Fe2O3 -based oxygen carriers, they are combined with traditional tar cracking catalysts. Based on thermogravimetric reactivity and fixed bed tar cracking experiments, NiO is selected as an additive for Fe2O3 -based oxygen carriers for biomass chemical looping systems. The outcomes from this research will help in the development of economic and efficient oxygen carriers for the commercialization of the various chemical looping applications.

Author: Cheng Lung Chung
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages :

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Book Description
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.