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Hydrogen Production Enhancement And The Effect Of Passive Mixing Using Flow Disturbers In A Steam Reforming Reactor
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Book Synopsis Hydrogen Production Enhancement and the Effect of Passive Mixing Using Flow Disturbers in a Steam-reforming Reactor by : Chang-Hsien Liao
Download or read book Hydrogen Production Enhancement and the Effect of Passive Mixing Using Flow Disturbers in a Steam-reforming Reactor written by Chang-Hsien Liao and published by . This book was released on 2008 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Comparative Study of Heat Transfer Enhancement Using Flow Impingement in Steam-reforming Reactors by : Ian Kah Kidh Sit
Download or read book A Comparative Study of Heat Transfer Enhancement Using Flow Impingement in Steam-reforming Reactors written by Ian Kah Kidh Sit and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigates the enhancement of heat transfer in steam reformation reactors through the application of flow impingement in the catalyst bed. For steam reformation, it is known that the ability to convert hydrocarbons to hydrogen can be limited by heat transfer, mass transfer, and chemical kinetics. In this study, it is presented that flow impingement can be used to increase heat transfer in steam reformation through reduction of boundary layers and passive mixing. It is also presented that flow impingement could benefit mass transfer limitations through the same passive mixing, as well as increase chemical kinetics through enhanced heat transfer to reaction sites. As such, this study analyzes and compares the performance of a flow impinging catalyst, which consists of a novel structure, to that of a typical pelletized catalyst. The effects of flow impingement are experimentally investigated in conjunction with varied feedstock flow rates and reactor volumes. Their effects on reactor fuel conversion, temperature profile, heat transfer, characteristic time, and pressure drop are analyzed and studied. An empirical model for reactor performance was also developed and verified. The data collected by this study quantified the effects of flow impingement on steam reformation. Comparative test results found that utilization of flow impingement resulted in fuel conversion improvements of 1.1%-2.6%. In addition, experimental results also found improvements to the average heat transfer coefficients between reactors were 12%-21% when flow impingement was used. As such, it was determined that flow impingement could enhance heat transfer within the catalyst bed of a reactor, but this did not directly correlate with a similar improvement to fuel conversion. However, the application of flow impingement resulted in a 5%-15% decrease in characteristic conversion times, thus, confirming an overall improvement. It was concluded by this study that flow impingement could be an effective mechanism for enhancing heat transfer within steam reformation reactors; however, additional research on the efficacy of the employed flow schemes was recommended for enhancing overall performance of the process.
Book Synopsis Hydrogen Production Via Steam Reforming in a Reverse-Flow Reactor by : Frank Hershkowitz
Download or read book Hydrogen Production Via Steam Reforming in a Reverse-Flow Reactor written by Frank Hershkowitz and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Efficient Reheating Concepts for a Reverse-flow Methane Reformer by : Carlos Tellaeche Herranz
Download or read book Efficient Reheating Concepts for a Reverse-flow Methane Reformer written by Carlos Tellaeche Herranz and published by Logos Verlag Berlin. This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methane steam reforming is a well-established technology for the hydrogen production at industrial scale. For decentralized applications, the use of this energy intensive technology requires the development of novel, heat integrated reactor concepts. The adiabatic reverse-flow reformer is such a concept that enables to energetically couple the highly endothermic methane steam reforming with an exothermic combustion reaction using an asymmetric switching pattern, in which the operating conditions to run the production (reforming) and regeneration (combustion) steps alternate with every flow reversal. One of the main challenges for the technical realization of this concept is the efficient reheating of the packed bed at a high temperature level, avoiding excess temperatures that might damage the catalyst and the reactor itself. The present work tackles this aspect and describes the development of a combustion chamber to be embedded in the packed bed. The chamber is designed in order to enable its operation under the so called flameless oxidation conditions, in which flame formation during combustion is suppressed and hence, the highest temperatures attained limited. The successful realization of this concept and its potential to efficiently reheat the reverse-flow reformer under dynamic operation is experimentally demonstrated and reported. The experimental observations provide an insight into the potential, the limitations and the attainable performance of the system. These observations are supported by a series of detailed simulations. Besides enabling the analysis of alternative reactor configurations and switching patterns, the simulation results corroborate that the reverse flow-reformer studied experimentally is especially suited for the production of hydrogen in decentralized facilities.
Book Synopsis Heat and Mass Transfer Enhancement of the Packed Bed Fischer-Tropsch Reactor by : Steven Wiryadinata
Download or read book Heat and Mass Transfer Enhancement of the Packed Bed Fischer-Tropsch Reactor written by Steven Wiryadinata and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This experimental work investigates the effect of flow field alteration in the packed bed Fischer-Tropsch (FT) reactor through the use of flow disturbers (bluff body) and varying the reactor aspect ratio using packed beds of two length-to-diameter ratios. The FT process is limited by heat and mass transfer and chemical kinetics as prescribed by the reactor geometry, flow and temperature fields, and catalyst properties. Exothermicity and uneven reaction rates lead to radial temperature and concentration gradients, which may increase conversion at the expense of high short-chain HC production (defined as C7 in this work) undesirable for the production of HC liquids. The present work investigates the influence of aspect ratio, flow rate and application of passive flow disturber packages in the fixed bed FT reactor on conversion and C[subscript 7+] productivity. Additional data acquisition at elevated temperatures and higher catalyst mass loading were performed. Empirical models as functions of aspect ratio, flow and number of bluff body packages were developed to enable predictions of conversion and productivity for a range of input values with minimum required data. Experiments were carried out using two 188 cm3 reactors with 3.8 and 30.8 aspect ratios (length-to-diameter ratios) loaded with equivalent mass of 20% cobalt/Al2O3 catalyst and controlled at 200°C at the exterior wall. The feed flow at constant 2.2 H2/CO ratio was varied between 300 and 800 GHSV. Reactor pressure was maintained at 2.75 bar. The effect of increased control temperature and increased reactor catalyst load were also investigated. Results show that the bluff bodies (enhanced case) have significant positive impact on conversion and productivity across the experimental space. The individual effect of the bluff bodies, the interaction between bluff bodies and flow rate, and the interaction between aspect ratio and bluff bodies are the statistically most significant factors influencing CO conversion, C[subscript 7+] yield and total C[subscript 7+] production rate, respectively. Conversion, yield and production rate of the enhanced reactor were increased by as much as 2.5x, 2.7x, and 5.4x of the baseline case, respectively. The bluff bodies were observed to increase effective residence times by 2.3x and 2.2x compared to the baseline wide and thin reactors, respectively, due to an imposed lengthening of the reaction path length. Compared to the baseline thin reactor, the enhanced wide reactor exhibited as much as 1.1x, 2.7x and 3x better conversion, yield and productivity, respective, and demonstrates that passive flow enhancement can reduce reactor length. This reduction in reactor length, which is accompanied by an increase in diameter, improves the cost effectiveness of FT at the small scale since state-of-the-art industrial packed bed FT has always employed high aspect ratio (L/D 200, > 5 cm inner diameter) multi-tubular reactors which cannot be replicated in the small scale. Furthermore, the combination of high flow, high reactor aspect ratio and use of bluff bodies at the normal catalyst load resulted in C[subscript 7+] productivity that approached the productivity of a reactor with 1.67x the catalyst load, thus indicating that the combined bluff body and aspect ratio adjustment can significantly boost productivity without additional use of expensive catalyst materials. The combination of 1) marked improvement in single pass productivity, 2) reduction in reactor length, and 3) reduction in reactor catalyst loading suggests that the use of internal flow disturbers in the packed bed had significant influence in lowering the heat and mass transfer resistances of the FT process, and can improve the cost-competitiveness of FT liquids production in the small scale.
Book Synopsis Fluidized Bed Membrane Reactor for Steam Reforming of Higher Hydrocarbons by :
Download or read book Fluidized Bed Membrane Reactor for Steam Reforming of Higher Hydrocarbons written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With growing demand for hydrogen in the industrial and energy sectors, research on novel hydrogen production processes is gaining importance. Fluctuations in price and availability of different hydrocarbons emphasize the need to diversify feedstock options beyond natural gas, the major source for hydrogen. Traditional steam reformers for making hydrogen from hydrocarbons suffer from low catalyst effectiveness factors, poor heat transfer and limited hydrogen yield due to thermodynamic equilibrium constraints. A fluidized bed membrane reactor (FBMR) was designed, fabricated, installed with close attention to safety and operated with methane, propane and heptane as feedstocks at average bed temperatures up to 550°C and pressures up to 800 kPa. When operated without membranes, near-equilibrium conditions were achieved inside the reactor with fluidized catalyst due to the fast reforming reactions. Installation hydrogen permselective Pd----Ag23 membrane panels inside the reactor to extract pure hydrogen shifted the reaction towards complete conversion of the hydrocarbons, including methane, the key intermediate when propane and heptane were the feed hydrocarbons. Reforming of higher hydrocarbons was found to be limited by the reversibility of the steam reforming of this methane. To assess the performance due to hydrogen in situ withdrawal, experiments were conducted with one and six membrane panels along the reactor. The results demonstrated that the FBMR could produce pure hydrogen from higher hydrocarbon feedstocks at moderate operating temperatures of 475-550°C. A two-phase fluidized bed reactor model was developed, with gas assumed to be in plug flow in both the bubble and dense phases. Diffusional mass transfer, as well as bulk convective flow between the phases, was incorporated to account for concentrations changing due to reactions predominantly in the dense phase, and due to increased molar flow due to reaction. Membranes withdraw hydrogen from both the dense and b.
Book Synopsis Hydrogen Production Enhancement Using a Stratified Catalyst Bed in Reforming Systems by : Nadia Olivia Richards
Download or read book Hydrogen Production Enhancement Using a Stratified Catalyst Bed in Reforming Systems written by Nadia Olivia Richards and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation was conducted for a stratified catalyst arrangement for methanol reforming. The motivation for the stratified system is to strategically place different catalysts within the reactor so that the reaction will progress according to the catalyst selectivity. This will allow the reduction of the unwanted intermediates and serves to improve the overall hydrogen product concentration. The stratified arrangement consisted of a platinum group metal (PGM) catalyst, along with a commercially available Cu/ZnO/Al2O3 water gas shift (WGS) catalyst. The system was experimentally investigated under different test conditions by varying the flow rate, oxygen-to-methanol ratio, and the packed length of the downstream WGS section. From these experiments the effects of each variable were quantified for their influence on the conversion and hydrogen yield. The oxidation reactions were carried out on the PGM catalyst, causing internal heating of the downstream WGS packed bed. The supplied heat keeps the WGS catalyst active to reform and shift the final products into a hydrogen-rich composition. Conversion increases of 30% were possible within one added section of WGS catalyst, with two sections achieving full conversion. This behavior can be modeled as a first order response from which a characteristic WGS length can be determined and used as a descriptive parameter to compare stratified systems. Overall, this study is expected to provide a basic analysis, and contribute to the improvement of reformer design for better fuel processing system performance.
Book Synopsis Determination of Optimal Process Flowrates and Reactor Design for Autothermal Hydrogen Production in a Heat-integrated Ceramic Microchannel Network by : Shalini Damodharan
Download or read book Determination of Optimal Process Flowrates and Reactor Design for Autothermal Hydrogen Production in a Heat-integrated Ceramic Microchannel Network written by Shalini Damodharan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work aimed at designing a thermally efficient microreactor system coupling methanol steam reforming with methanol combustion for autothermal hydrogen production. A preliminary study was performed by analyzing three prototype reactor configurations to identify the optimal radial distribution pattern upon enhancing the reactor self-insulation. The annular heat integration pattern of Architecture C showed superior performance in providing efficient heat retention to the system with a 50 - 150°C decrease in maximum external-surface temperature. Detailed work was performed using Architecture C configuration to optimize the catalyst placement in the microreactor network, and optimize reforming and combustion flows, using no third coolant line. The optimized combustion and reforming catalyst configuration prevented the hot-spot migration from the reactor midpoint and enabled stable reactor operation at all process flowrates studied. Best results were obtained at high reforming flowrates (1800 sccm) with an increase in combustion flowrate (300 sccm) with the net H2 yield of 53% and thermal efficiency of>80% from methanol with minimal insulation to the heatintegrated microchannel network. The use of the third bank of channels for recuperative heat exchange by four different reactor configurations was explored to further enhance the reactor performance; the maximum overall hydrogen yield was increased to 58% by preheating the reforming stream in the outer 16 heat retention channels. An initial 3-D COMSOL model of the 25-channeled heat-exchanger microreactor was developed to predict the reactor hotspot shape, location, optimum process flowrates and substrate thermal conductivity. This study indicated that low thermal conductivity materials (e.g. ceramics, glass) provides enhanced efficiencies than high conductivity materials (e.g. silicon, stainless steel), by maintaining substantial thermal gradients in the system through minimization of axial heat conduction. Final summary of the study included the determination of system energy density; a gravimetric energy density of 169.34 Wh/kg and a volumetric energy density of 506.02 Wh/l were achieved from brass architectures for 10 hrs operation, which is higher than the energy density of Li-Ion batteries (120 Wh/kg and 350 Wh/l). Overall, this research successfully established the optimal process flowrates and reactor design to enhance the potential of a thermally-efficient heat-exchanger microchannel network for autothermal hydrogen production in portable applications.
Book Synopsis Novel Membrane Steam Reforming (MSR) Reactor for Pure Hydrogen Production by : Andreas N. Matzakos
Download or read book Novel Membrane Steam Reforming (MSR) Reactor for Pure Hydrogen Production written by Andreas N. Matzakos and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Use of Advanced Steam Reforming Technology for Hydrogen Production by : J. B. Abbishaw
Download or read book The Use of Advanced Steam Reforming Technology for Hydrogen Production written by J. B. Abbishaw and published by . This book was released on 1996 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Computational Fluid Dynamics and Machine Learning Modeling, Operation and Control of Steam Methane Reforming Reactors and Furnaces by : Anh Tuan Tran
Download or read book Computational Fluid Dynamics and Machine Learning Modeling, Operation and Control of Steam Methane Reforming Reactors and Furnaces written by Anh Tuan Tran and published by . This book was released on 2018 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogen is proposed by many to be the fuel of the future as it is the key ingredient in a transition from a fossil fuel-based economy toward a zero carbon emission and sustainable energy economy. Hydrogen can serve as an efficient energy carrier for hydrogen-based technologies (e.g., fuel cells and hydrogen internal combustion engine) and lead to substantial reduction of greenhouse gas emissions and great environmental benefits. Hydrogen can be produced by a variety of technologies (e.g., steam methane reforming (SMR), coal gasification, biomass gasification, electrolysis, partial oxidation, solar thermal cracking) from fossil (e.g., natural gas), non-fossil (e.g., biogas) and non-carbon (e.g., water) sources, which highlights the great potential and flexibility of a hydrogen-based economy. Additionally, hydrogen is a key feedstock for the petroleum refining and fine chemical manufacturing industries. With current state-of-the-art technology, hydrogen is produced almost exclusively from fossil fuels by SMR. At SMR-based hydrogen plants, the reformers are the most expensive equipment in terms of the maintenance and operating costs, and thus, even a small improvement in the reformer thermal efficiency to lower operating costs of the reformer without compromising the expected service life of the reformer is expected to allow the plants to achieve a significant profit. Motivated by these considerations, a systematic framework for creating and simulating a computational fluid dynamics (CFD) model for an industrial-scale reformer at an SMR-based hydrogen plant and, subsequently, a framework for designing and evaluating a real-time furnace balancing scheme are developed in this dissertation. Specifically, a CFD model for an industrial-scale reformer is created in ANSYS Fluent, which is used to improve our understanding of the physiochemical processes in the tube side and the furnace side of the reformer as well as their thermal interactions during the catalytic conversion of methane. Then, a furnace balancing scheme is developed to optimize the reformer input at the nominal total furnace-side feed (FSF) flow rate that minimizes the inherent variability in the outer tube wall temperature (OTWT) distributions along the reforming tube length. Subsequently, a statistical-based model identification is developed to create a computationally efficient and robust model for the OTWT distribution as a function of the FSF distribution, total FSF flow rate and interactions among neighboring reforming tubes so that the optimized reformer input can be identified in real-time. Finally, a real-time furnace-balancing scheme is developed to optimize the reformer input such that the reformer thermal efficiency is maximized without compromising the expected service life of the reformer.
Book Synopsis A Compact and Efficient Steam Methane Reformer for Hydrogen Production by : Willard Lawrence Quon
Download or read book A Compact and Efficient Steam Methane Reformer for Hydrogen Production written by Willard Lawrence Quon and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A small-scale steam-methane reforming system for localized, distributed production of hydrogen offers improved performance and lower cost by integrating the following technologies developed at the University of Houston; (1) Catalyzed steam-methane reforming on ceramic foam catalyst substrates. (2) Coupling of reformers to remote heat sources via heat pipes instead of heating by direct-fired heaters. (3) Catalytic combustion of methane with air on ceramic foam substrates as the heat source. Each of these three technologies confer benefits improving the efficiency, reliability, or cost of an integrated compact steam-methane reforming system. A prior 2-D computer model was adapted from existing FORTRAN code for a packed-bed reactor and successfully updated to better reflect heat transfer in the ceramic foam bed and at the reactor wall, then validated with experimental heat transfer and reaction data for use in designing commercial-scale ceramic foam catalytic reactors. Different configurations and sizes of both reformer and combustor reactors were studied to arrive at a best configuration for an integrated system. The radial and axial conversions and temperatures of each reactor were studied to match the heat recovery capability of the reformer to the heat generation characteristics of the combustor. The vetted computer model was used to size and specify a 500 kg/day hydrogen production unit featuring ceramic foam catalyst beds integrated into heat pipe reactors that can be used for multiple end users, ranging from small edible fats and oils hydrogenators to consumer point of sale hydrogen fueling stations. The estimated investment for this 500 kg/day system is $2,286,069 but is expected to drop to less than $1,048,000 using mass production methods. Economic analysis of the 500 kg/day hydrogen production system shows that it is not presently competitive with gasoline as a transportation fuel, but the system is still economically attractive to stationary fuel cell applications or small chemical users with a delivered hydrogen price as low as $1.49/kg, even with a 10% IRR that includes investment recovery, depreciation, taxes, etc.
Book Synopsis Alcohol Steam Reforming for Hydrogen Production by : Rick B. Watson
Download or read book Alcohol Steam Reforming for Hydrogen Production written by Rick B. Watson and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Microchannel Steam-methane Reforming Under Constant and Variable Surface Temperature Distributions by : Benn J. Eilers
Download or read book Microchannel Steam-methane Reforming Under Constant and Variable Surface Temperature Distributions written by Benn J. Eilers and published by . This book was released on 2010 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steam-methane reforming is a well understood industrial process used for generating hydrogen and synthesis gas. The reaction is generally carried out with residence times on the order of one second. By performing this reaction at microscales it is possible to take advantage of increased heat transfer rates and low diffusion times allowing equipment size and residence times to be decreased by an order of magnitude. The energy required for the steam-methane reforming reaction could be supplied by solar energy through the use of a solar collector/receiver, thus providing a "cleaner" pathway for hydrogen generation. In such reactors, it is expected that the heat flux and temperature distribution is non-uniform. This study presents a first step in characterizing reforming performance under such variable temperature conditions. The design of the channel was such that the non-uniform heat flux profile expected inside of a solar receiver could be simulated by a controllable temperature profile along the reactor surface. Experiments were conducted over four catalyst configurations and the effects of average reactor temperature, temperature distribution, residence time, steam-methane ratio, and long duration testing were all evaluated. Results demonstrated over 60% conversion of methane at 900°C and a residence time of 26 milliseconds. Methane conversion was found to be strongly dependent on reactor temperature. Ramping temperature distributions demonstrated a 46% greater hydrogen output than isothermal reactions performed at the same average temperature. This work was performed in conjunction with development of a CFD model of reacting flow through a microchannel [1]. The experiments were used to determine the pre-exponential constants of the global reaction rates.
Book Synopsis Hydrogen Production from the Steam Reforming of Methanol Over Au/Fe2O3-CeO2 Catalysts by : Wissanu Shuenka
Download or read book Hydrogen Production from the Steam Reforming of Methanol Over Au/Fe2O3-CeO2 Catalysts written by Wissanu Shuenka and published by . This book was released on 2009 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Hydrogen Production from the Steam Reforming of Methanol Over Supported Au Catalysts by : Salintip Thareejid
Download or read book Hydrogen Production from the Steam Reforming of Methanol Over Supported Au Catalysts written by Salintip Thareejid and published by . This book was released on 2008 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Steam Reforming of Oxygenated Hydrocarbons for Hydrogen Production by : Mohammad Azizan
Download or read book Steam Reforming of Oxygenated Hydrocarbons for Hydrogen Production written by Mohammad Azizan and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
