Multi-Scale Modeling and Simulation of Intensified Reactive-Separation Processes for Hydrogen Production and CO2 Capture Via the Water-Gas Shift Reaction (WGSR) PDF Download
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Author: Secgin Karagoz Publisher: ISBN: Category : Languages : en Pages : 190
Book Description
As a result of fossil fuels-based energy production, reducing atmospheric carbon dioxide emissions has become an urgent issue. Especially, carbon capture and storage (CCS) technology, being one of the leading processes to reduce total carbon emissions, has become increasingly important. Hydrogen is an important energy carrier, and hydrogen-based technologies have increased in importance recently due to the worldwide focus on green processes. The Integrated Gasification Combined Cycle (IGCC) is a promising technology supplying clean energy at affordable prices. The IGCC process is currently being coupled with CCS technologies. However, using CCS technologies in power generation processes is a great challenge, necessitating the intensification of the coupled IGCC-CCS process. Process intensification (PI), leads to substantially smaller, cleaner, and more energy efficient processes, and is a prominent topic, receiving significant attention in recent years. As part of intensifying a process, integration of multiple operations (e.g., reaction and separation) in a single unit is often carried out, to improve the existing process efficiency, and to reduce energy consumption, and unwanted output/by-product generation. The objective of this work is to demonstrate the process intensification potential of a technology, containing one or more water gas shift (WGS) reactor components seamlessly integrated with other plant components. We investigate the applicability of various (alternative to the conventional process) novel and efficient reactor configurations that include self-standing adsorptive reactor (AR)/membrane reactor (MR), and the combination of a MR-LTSR-AR-adsorptive separator (AS)-membrane separation (MS) units (herein after referred to as the LTSR-MS/LTSR-AS/AS-LTSR-AS/MR-AS/AS-MR-AS/MR-AR systems). The proposed WGS reactor technologies have the potential to generate highly efficient and ultra-compact processes, by producing H2 for use in IGCC with simultaneous CO2 capture. Innovative designs of the proposed processes are determined based on the comprehensive modeling and design of the selected IGCC plant's section. Comprehensive, multi-scale, multi-phase, computational fluid dynamics (CFD) models are developed for reaction/separation processes. Developed models quantify the many complex physicochemical phenomena occurring within the process, thus providing the basis to better understand, and intensify the overall system. Model predictions are generated for a broad range of operating conditions and design parameters, thus enabling a comparative performance assessment of the proposed process versus a conventional process for the proposed IGCC application.
Author: Secgin Karagoz Publisher: ISBN: Category : Languages : en Pages : 190
Book Description
As a result of fossil fuels-based energy production, reducing atmospheric carbon dioxide emissions has become an urgent issue. Especially, carbon capture and storage (CCS) technology, being one of the leading processes to reduce total carbon emissions, has become increasingly important. Hydrogen is an important energy carrier, and hydrogen-based technologies have increased in importance recently due to the worldwide focus on green processes. The Integrated Gasification Combined Cycle (IGCC) is a promising technology supplying clean energy at affordable prices. The IGCC process is currently being coupled with CCS technologies. However, using CCS technologies in power generation processes is a great challenge, necessitating the intensification of the coupled IGCC-CCS process. Process intensification (PI), leads to substantially smaller, cleaner, and more energy efficient processes, and is a prominent topic, receiving significant attention in recent years. As part of intensifying a process, integration of multiple operations (e.g., reaction and separation) in a single unit is often carried out, to improve the existing process efficiency, and to reduce energy consumption, and unwanted output/by-product generation. The objective of this work is to demonstrate the process intensification potential of a technology, containing one or more water gas shift (WGS) reactor components seamlessly integrated with other plant components. We investigate the applicability of various (alternative to the conventional process) novel and efficient reactor configurations that include self-standing adsorptive reactor (AR)/membrane reactor (MR), and the combination of a MR-LTSR-AR-adsorptive separator (AS)-membrane separation (MS) units (herein after referred to as the LTSR-MS/LTSR-AS/AS-LTSR-AS/MR-AS/AS-MR-AS/MR-AR systems). The proposed WGS reactor technologies have the potential to generate highly efficient and ultra-compact processes, by producing H2 for use in IGCC with simultaneous CO2 capture. Innovative designs of the proposed processes are determined based on the comprehensive modeling and design of the selected IGCC plant's section. Comprehensive, multi-scale, multi-phase, computational fluid dynamics (CFD) models are developed for reaction/separation processes. Developed models quantify the many complex physicochemical phenomena occurring within the process, thus providing the basis to better understand, and intensify the overall system. Model predictions are generated for a broad range of operating conditions and design parameters, thus enabling a comparative performance assessment of the proposed process versus a conventional process for the proposed IGCC application.
Author: Panagiotis Smirniotis Publisher: Elsevier ISBN: 0444633537 Category : Technology & Engineering Languages : en Pages : 280
Book Description
Water Gas Shift Reaction: Research Developments and Applications outlines the importance of hydrogen as a future fuel, along with the various hydrogen production methods. The book explains the development of catalysts for Water Gas Shift (WGS) reaction at different temperatures and steam/CO ratios, and also discussing the effect of different dopants on the WGS activity of iron oxide and the promotion and inhibition roles of the dopants on the WGS activity of iron oxide are explained. In addition, the book describes extensive characterization of modified ferrite catalysts, especially with Mossbauer spectroscopy and its advantage in understanding properties of metal doped ferrite catalysts, the exact dopant location, and its effect on electron hopping capability and WGS activity of Fe redox couple. Outlines the importance of the Water Gas Shift Reaction and its application for hydrogen production Provides detailed information on potential catalysts, their development, and their pros and cons, giving the reader insights on how modified ferrite catalysts work at different temperatures and different steam to CO ratios Reviews hydrogen technology, its current importance, and production methods Presents a clear presentation of the topics with many graphics and tables Offers basic and advanced knowledge of catalysts characterization instrumental techniques
Author: Publisher: ISBN: Category : Languages : en Pages : 18
Book Description
Optimization of the water-gas shift (WGS) reaction system for hydrogen production for fuel cells is of particular interest to the energy industry. To this end, it is desirable to couple the WGS reaction to hydrogen separation using a semi-permeable membrane, with both processes carried out at high temperatures to improve reaction kinetics and permeation. Reduced equilibrium conversion of the WGS reaction at high temperatures is overcome by product H2 removal via the membrane. This project involves fundamental research and development of novel cerium oxide-based catalysts for the water-gas-shift reaction and the integration of these catalysts with Pd-alloy H2-separation membranes supplying high purity hydrogen for fuel cell use. Conditions matching the requirements of coal gasifier-exit gas streams will be examined in the project. The first-year screening studies of WGS catalysts identified Cu-ceria as the most promising high-temperature shift catalyst for integration with H2-selective membranes. Formulations containing iron oxide were found to deactivate in the presence of CO2, and were thus eliminated from further consideration. Cu-containing ceria catalysts, on the other hand, showed high stability in CO2-rich gases. This type gas will be present over much of the catalyst, as the membrane removes the hydrogen produced from the shift reaction. Several catalyst formulations were prepared, characterized and tested in the first year of study. Details from the catalyst development and testing work were given in our first annual technical report. Hydrogen permeation through Pd and Pd-alloy foils was investigated in a small membrane reactor constructed during the first year of the project. The effect of temperature on the hydrogen flux through pure Pd, Pd60Cu40 and Pd--5Ag25 alloy membranes, each 25 [mu]m thick, was evaluated in the temperature range from 250 C to 500 C at upstream pressure of 4.4 atm and permeate hydrogen pressure of 1 atm. Flux decay was observed for the Pd-Cu membrane above 500 C. From 350-450 C, an average hydrogen flux value of 0.2 mol H2/m2/s was measured over this Pd-alloy membrane. These results are in good agreement with literature data. In this year's report, we discuss reaction rate measurements, optimization of catalyst kinetics by proper choice of dopant oxide (lanthana) in ceria, long-term stability studies, and H2 permeation data collected with unsupported flat, 10 [mu]m-thick Pd-Cu membranes over a wide temperature window and in various gas mixtures. The high-temperature shift catalyst composition was further improved, by proper selection of dopant type and amount. The formulation 10 at%Cu-Ce(30 at%La)Ox was the best; this was selected for further kinetic studies. WGS reaction rates were measured in a simulated coal-gas mixture. The stability of catalyst performance was examined in 40-hr long tests. A series of hydrogen permeation tests were conducted in a small flat-membrane reactor using the 10 m[mu]-thick Pd-Cu membranes. Small inhibitory effects of CO and CO2 were found at temperatures above 350 C, while H2O vapor had no effect on hydrogen permeation. No carbon deposition took place during many hours of membrane operation. The reaction extent on the blank (catalyst-free) membrane was also negligible. A larger flat-membrane reactor will be used next year with the catalyst wash coated on screens close coupled with the Pd-Cu membrane.
Author: Publisher: ISBN: Category : Languages : en Pages : 23
Book Description
Hydrogen production by the water gas shift reaction (WGSR) is equilibrium limited due to thermodynamic constrains. However, this can be overcome by continuously removing the product CO2, thereby driving the WGSR in the forward direction to enhance hydrogen production. This project aims at using a high reactivity, mesoporous calcium based sorbent (PCC-CaO) for removing CO2 using reactive separation scheme. Preliminary results have shown that PCC-CaO dominates in its performance over naturally occurring limestone towards enhanced hydrogen production. However, maintenance of high reactivity of the sorbent over several reaction-regeneration cycles warrants effective regeneration methods. We have identified sub-atmospheric calcination (vacuum) as vital regeneration technique that helps preserve the sorbent morphology. Sub-atmospheric calcination studies reveal the significance of vacuum level, diluent gas flow rate, thermal properties of diluent gas, and sorbent loading on the kinetics of calcination and the morphology of the resultant CaO sorbent. Steam, which can be easily separated from CO2, has been envisioned as a potential diluent gas due to its better thermal properties resulting in effective heat transfer. A novel multi-fixed bed reactor was designed which isolates the catalyst bed from the sorbent bed during the calcination step. This should prevent any potential catalyst deactivation due to oxidation by CO2 during the regeneration phase.
Author: Publisher: ISBN: Category : Languages : en Pages : 19
Book Description
Optimization of the water-gas shift (WGS) reaction system for hydrogen production for fuel cells is of particular interest to the energy industry. To this end, it is desirable to couple the WGS reaction to hydrogen separation using a semi-permeable membrane, with both processes carried out at high temperature to improve reaction kinetics. Reduced equilibrium conversion of the WGS reaction at high temperatures is overcome by product H2 removal via the membrane. This project involves fundamental research and development of novel cerium oxide-based catalysts for the water-gas-shift reaction and the integration of these catalysts with Pd-alloy H2-separation membranes supplying high purity hydrogen for fuel cell use. Conditions matching the requirements of coal gasifier-exit gas streams will be examined in the project. In the first year of the project, we prepared a series of nanostructured Cu- and Fe-containing ceria catalysts by a special gelation/precipitation technique followed by air calcination at 650 C. Each sample was characterized by ICP for elemental composition analysis, BET-N2 desorption for surface area measurement, and by temperature-programmed reduction in H2 to evaluate catalyst reducibility. Screening WGS tests with catalyst powders were conducted in a flow microreactor at temperatures in the range of 200-550 C. On the basis of both activity and stability of catalysts in simulated coal gas, and in CO2-rich gases, a Cu-CeO2 catalyst formulation was selected for further study in this project. Details from the catalyst development and testing work are given in this report. Also in this report, we present H2 permeation data collected with unsupported flat membranes of pure Pd and Pd-alloys over a wide temperature window.
Author: Mohammad Hassan Murad Chowdhury Publisher: ISBN: Category : Languages : en Pages : 382
Book Description
Coal-fired power plants are the largest anthropogenic point sources of CO2 emissions worldwide. About 40% of the world's electricity comes from coal. Approximately 49% of the US electricity in 2008 and 23% of the total electricity generation of Canada in 2000 came from coal-fired power plant (World Coal Association, and Statistic Canada). It is likely that in the near future there might be some form of CO2 regulation. Therefore, it is highly probable that CO2 capture will need to be implemented at many US and Canadian coal fired power plants at some point. Several technologies are available for CO2 capture from coal-fired power plants. One option is to separate CO2 from the combustion products using conventional approach such as chemical absorption/stripping with amine solvents, which is commercially available. Another potential alternative, membrane gas separation, involves no moving parts, is compact and modular with a small footprint, is gaining more and more attention. Both technologies can be retrofitted to existing power plants, but they demands significant energy requirement to capture, purify and compress the CO2 for transporting to the sequestration sites. This thesis is a techno-economical evaluation of the two approaches mentioned above along with another approach known as hybrid. This evaluation is based on the recent advancement in membrane materials and properties, and the adoption of systemic design procedures and optimization approach with the help of a commercial process simulator. Comparison of the process performance is developed in AspenPlus process simulation environment with a detailed multicomponent gas separation membrane model, and several rigorous rate-based absorption/stripping models. Fifteen various single and multi-stage membrane process configurations with or without recycle streams are examined through simulation and design study for industrial scale post-combustion CO2 capture. It is found that only two process configurations are capable to satisfy the process specifications i.e., 85% CO2 recovery and 98% CO2 purity for EOR. The power and membrane area requirement can be saved by up to 13% and 8% respectively by the optimizing the base design. A post-optimality sensitivity analysis reveals that any changes in any of the factors such as feed flow rate, feed concentration (CO2), permeate vacuum and compression condition have great impact on plant performance especially on power consumption and product recovery. Two different absorption/stripping process configurations (conventional and Fluor concept) with monoethanolamine (30 wt% MEA) solvent were simulated and designed using same design basis as above with tray columns. Both the rate-based and the equilibrium-stage based modeling approaches were adopted. Two kinetic models for modeling reactive absorption/stripping reactions of CO2 with aqueous MEA solution were evaluated. Depending on the options to account for mass transfer, the chemical reactions in the liquid film/phase, film resistance and film non-ideality, eight different absorber/stripper models were categorized and investigated. From a parametric design study, the optimum CO2 lean solvent loading was determined with respect to minimum reboiler energy requirement by varying the lean solvent flow rate in a closed-loop simulation environment for each model. It was realized that the success of modeling CO2 capture with MEA depends upon how the film discretization is carried out. It revealed that most of the CO2 was reacted in the film not in the bulk liquid. This insight could not be recognized with the traditional equilibrium-stage modeling. It was found that the optimum/or minimum lean solvent loading ranges from 0.29 to 0.40 and the reboiler energy ranges from 3.3 to 5.1 (GJ/ton captured CO2) depending on the model considered. Between the two process alternatives, the Fluor concept process performs well in terms of plant operating (i.e., 8.5% less energy) and capital cost (i.e., 50% less number of strippers). The potentiality of hybrid processes which combines membrane permeation and conventional gas absorption/stripping using MEA were also examined for post-combustion CO2 capture in AspenPlus®. It was found that the hybrid process may not be a promising alternative for post-combustion CO2 capture in terms of energy requirement for capture and compression. On the other hand, a stand-alone membrane gas separation process showed the lowest energy demand for CO2 capture and compression, and could save up to 15 to 35% energy compare to the MEA capture process depending on the absorption/stripping model used.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
This factsheet describes a research project whose objective is to develop hydrogen-selective membranes for an innovative gas-separation process based on a water-gas-shift membrane reactor (WGS-MR) for the production of hydrogen.
Author: Liang-Shih Fan Publisher: ISBN: Category : Languages : en Pages :
Book Description
Enhancement in the production of high purity hydrogen from fuel gas, obtained from coal gasification, is limited by thermodynamics of the Water Gas Shift Reaction. However, this constraint can be overcome by concurrent water-gas shift (WGS) and carbonation reactions to enhance H{sub 2} production by incessantly driving the equilibrium-limited WGS reaction forward and in-situ removing the CO2 product from the gas mixture. The spent sorbent is then regenerated by calcining it to produce a pure stream of CO{sub 2} and CaO which can be reused. However while performing the cyclic carbonation and calcination it was observed that the CO{sub 2} released during the in-situ calcination causes the deactivation of the iron oxide WGS catalyst. Detailed understanding of the iron oxide phase diagram helped in developing a catalyst pretreatment procedure using a H{sub 2}/H{sub 2}O system to convert the deactivated catalyst back to its active magnetite (Fe{sub 3}O{sub 4}) form. The water gas shift reaction was studied at different temperatures, different steam to carbon monoxide ratios (S/C) 3:1, 2:1, 1:1 and different total pressures ranging from 0-300 psig. The combined water gas shift and carbonation reaction was investigated at temperatures ranging from 600-700C, S/C ratio of 3:1 to 1:1 and at different pressures of 0-300 psig and the calcium looping process was found to produce high purity hydrogen with in-situ CO{sub 2} capture.
Author: Secgin Karagoz
Author: Secgin Karagoz
Author: Panagiotis Smirniotis
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Author: Chun Han
Author: Mohammad Hassan Murad Chowdhury
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Author: Liang-Shih Fan