Home About us Contact
|
Home About us Contact | ||
|
|
||
Methane Steam Reforming (methane + steam_reforming)
Selected AbstractsNi Catalyst Coating on Fecralloy® Microchanneled Foils and Testing for Methane Steam ReformingCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010N. de Miguel Abstract The procedure following the washcoating of three different Ni catalyst systems (MgO, Al2O3, and CeO2/Al2O3 supported) on pretreated Fecralloy® microchanneled foils under controlled milling times and viscosities of the slurries is described. The activity of the prepared coatings is also presented. Four different series of coated foils were prepared: one per each catalyst system, keeping constant the average particle size on 5 ,m, and one extra series to study the effect of reducing the average particle size of the MgO-supported catalyst system to 3 ,m. For each coating, scanning electron microscopy pictures were taken and specific surface areas and average densities of the catalyst layers were estimated. Finally, each series of coated foils was stacked and tested in a microreactor for the methane steam reforming (MSR) reaction under different conditions. [source] Effect of Oxygen on Methane Steam Reforming in a Sliding Discharge ReactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2006F. Ouni Abstract Hydrogen-rich gas can be efficiently produced in compact plasma reformers by the conversion of a variety of hydrocarbon fuels, including natural gas and gasoline. This article describes experimental and modeling progress in plasma reforming of methane using a sliding discharge reactor (SDR). Experiments have been carried out in a compact device operating at low consumed power (1,2,kW). Previous studies of methane steam reforming using a SDR at atmospheric pressure show promising results (H2 concentration higher than 55,%). In order to study the effect of oxygen on the methane conversion and thus hydrogen production, a small amount of oxygen in the range of 7,20,% was added to the CH4 -H2O mixture. An unexpected result was that under our experimental conditions in the SDR oxygen did not have any influence on the methane conversion. Almost the totality of added oxygen is recovered intact. Moreover, part of the H2 produced was transformed into water by reaction with O2. A model describing the chemical processes based on classical thermodynamics is also proposed. The results indicate that the reactor design has to be improved in order to increase conversion and hydrogen production. [source] Methane steam reforming at microscales: Operation strategies for variable power output at millisecond contact timesAICHE JOURNAL, Issue 1 2009Georgios D. Stefanidis Abstract The potential of methane steam reforming at microscale is theoretically explored. To this end, a multifunctional catalytic plate microreactor, comprising of a propane combustion channel and a methane steam reforming channel, separated by a solid wall, is simulated with a pseudo 2-D (two-dimensional) reactor model. Newly developed lumped kinetic rate expressions for both processes, obtained from a posteriori reduction of detailed microkinetic models, are used. It is shown that the steam reforming at millisecond contact times is feasible at microscale, and in agreement with a recent experimental report. Furthermore, the attainable operating regions delimited from the materials stability limit, the breakthrough limit, and the maximum power output limit are mapped out. A simple operation strategy is presented for obtaining variable power output along the breakthrough line (a nearly iso-flow rate ratio line), while ensuring good overlap of reaction zones, and provide guidelines for reactor sizing. Finally, it is shown that the choice of the wall material depends on the targeted operating regime. Low-conductivity materials increase the methane conversion and power output at the expense of higher wall temperatures and steeper temperature gradients along the wall. For operation close to the breakthrough limit, intermediate conductivity materials, such as stainless steel, offer a good compromise between methane conversion and wall temperature. Even without recuperative heat exchange, the thermal efficiency of the multifunctional device and the reformer approaches ,65% and ,85%, respectively. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Computational study of staged membrane reactor configurations for methane steam reforming.AICHE JOURNAL, Issue 1 2010Abstract This article and Part II report a computational study carried out to analyze the performance achievable using a staged membrane reactor in the methane steam reforming process to produce high purity hydrogen. A reaction/separation unit in which reactive stages are laid out in series to permeative stages already proposed in literature (Caravella et al., J Memb Sci. 2008;321:209,221) is modified here to increase its flexibility. The improvement includes the consideration of the Pd-based membrane along the entire length. Two- and ten-staged reactors are examined in terms of methane conversion, hydrogen recovery factor and hydrogen recovery yield, considering co- and counter-current flow configurations. Individual stage lengths are obtained by maximizing either methane conversion or hydrogen recovery yield, comparing the results to the ones of an equivalent traditional reactor and a conventional membrane reactor. The analysis allows demonstrating that the counter-current configuration leads to significant improvements in the hydrogen recovery, but proves almost irrelevant with respect to methane conversion. The influence of the number of stages and the amount of catalyst is quantified in the accompanying part II article. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Computational study of staged membrane reactor configurations for methane steam reforming.AICHE JOURNAL, Issue 1 2010Abstract The present work complements part I of this article and completes a computational analysis of the performances of staged membrane reactors for methane steam reforming. The influence of the number of stages and catalyst amount is investigated by comparing the methane conversion and hydrogen recovery yield achieved by an equisized-staged reactor to those of an equivalent conventional membrane reactor for different furnace temperatures and flow configurations (co- and counter-current). The most relevant result is that the proposed configuration with a sufficiently high number of stages and a significantly smaller catalyst amount (up to 70% lower) can achieve performances very close to the ones of the conventional unit in all the operating conditions considered. This is equivalent to say that the staged configuration can compensate and in fact substitute a significant part of the catalyst mass of a conventional membrane reactor. To help the interpretation of these results, stage-by-stage temperature and flux profiles are examined in detail. Then, the quantification of the performance losses with respect to the conventional reactor is carried out by evaluating the catalyst amount possibly saved and furnace temperature reduction. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Methane steam reforming at microscales: Operation strategies for variable power output at millisecond contact timesAICHE JOURNAL, Issue 1 2009Georgios D. Stefanidis Abstract The potential of methane steam reforming at microscale is theoretically explored. To this end, a multifunctional catalytic plate microreactor, comprising of a propane combustion channel and a methane steam reforming channel, separated by a solid wall, is simulated with a pseudo 2-D (two-dimensional) reactor model. Newly developed lumped kinetic rate expressions for both processes, obtained from a posteriori reduction of detailed microkinetic models, are used. It is shown that the steam reforming at millisecond contact times is feasible at microscale, and in agreement with a recent experimental report. Furthermore, the attainable operating regions delimited from the materials stability limit, the breakthrough limit, and the maximum power output limit are mapped out. A simple operation strategy is presented for obtaining variable power output along the breakthrough line (a nearly iso-flow rate ratio line), while ensuring good overlap of reaction zones, and provide guidelines for reactor sizing. Finally, it is shown that the choice of the wall material depends on the targeted operating regime. Low-conductivity materials increase the methane conversion and power output at the expense of higher wall temperatures and steeper temperature gradients along the wall. For operation close to the breakthrough limit, intermediate conductivity materials, such as stainless steel, offer a good compromise between methane conversion and wall temperature. Even without recuperative heat exchange, the thermal efficiency of the multifunctional device and the reformer approaches ,65% and ,85%, respectively. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Novel nickel-based catalyst for low temperature hydrogen production from methane steam reforming in membrane reformerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010Yazhong Chen Abstract Hydrogen production from various hydrocarbon fuels, particularly biomass-derived fuels, has attracted worldwide attention due to its potential for application to fuel cells, a device which converts chemical energy into electricity efficiently and cleanly. However, current technology, such as natural gas steam reforming, could not meet the specific requirements of hydrogen for fuel cells. Therefore, novel processes are intensively investigated, aiming to develop economic and efficient ones for the specific purpose. An important direction is the integrated membrane reformer for one-step high-purity hydrogen production. However, for the commercial realization of this technology, there are still some difficulties to overcome. By comparison with previous investigations with a similar membrane, this work showed that catalyst also played an important role in determining membrane reformer performance. We proposed that when thickness of membrane was several micrometers, the permeance of membrane became less important than the kinetics of catalyst, due to the fact that under such conditions, hydrogen permeation rate was faster than the kinetics of steam reforming reaction when commercial catalyst was applied, but further evidence is indispensable. In this initial work, we focused on developing efficient nickel catalyst for low temperature steam reforming. Nickel-based catalyst was developed by deposition,coprecipitation and used as pre-reduced, showing high performance for methane steam reforming at low temperatures and good durability, which may find practical application for the integrated membrane reforming process. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Ni Catalyst Coating on Fecralloy® Microchanneled Foils and Testing for Methane Steam ReformingCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010N. de Miguel Abstract The procedure following the washcoating of three different Ni catalyst systems (MgO, Al2O3, and CeO2/Al2O3 supported) on pretreated Fecralloy® microchanneled foils under controlled milling times and viscosities of the slurries is described. The activity of the prepared coatings is also presented. Four different series of coated foils were prepared: one per each catalyst system, keeping constant the average particle size on 5 ,m, and one extra series to study the effect of reducing the average particle size of the MgO-supported catalyst system to 3 ,m. For each coating, scanning electron microscopy pictures were taken and specific surface areas and average densities of the catalyst layers were estimated. Finally, each series of coated foils was stacked and tested in a microreactor for the methane steam reforming (MSR) reaction under different conditions. [source] A Heat-Integrated Reverse-Flow Reactor Concept for Endothermic High-Temperature Syntheses.CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2009Part II: Development of a Reformer Prototype for Hydrogen Production Abstract In the first part of the contribution, the asymmetric operation of a reverse-flow reactor for endothermic high-temperature syntheses has been introduced and front phenomena have been discussed. The current part presents the implementation of the concept to the production of hydrogen by methane steam reforming. A key element of the developed reformer is the integration of combustion chambers for in situ heat generation during reheating of the bed. To avoid local temperature peaks, the concept of flameless combustion is used. The concept was adapted to the requirements of the unsteady operation. A proper design of the combustion chamber was developed using computational fluid dynamics calculations, tracer experiments and tests in a single combustion chamber. The concept was further tested under periodic operation in a laboratory setup. The formation of the desired, axially extended high-temperature plateau in the center of the reactor could be shown experimentally. The results prove the adequacy of the reverse-flow reformer to attain a stable periodic operation without excess temperatures. [source] Effect of Oxygen on Methane Steam Reforming in a Sliding Discharge ReactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2006F. Ouni Abstract Hydrogen-rich gas can be efficiently produced in compact plasma reformers by the conversion of a variety of hydrocarbon fuels, including natural gas and gasoline. This article describes experimental and modeling progress in plasma reforming of methane using a sliding discharge reactor (SDR). Experiments have been carried out in a compact device operating at low consumed power (1,2,kW). Previous studies of methane steam reforming using a SDR at atmospheric pressure show promising results (H2 concentration higher than 55,%). In order to study the effect of oxygen on the methane conversion and thus hydrogen production, a small amount of oxygen in the range of 7,20,% was added to the CH4 -H2O mixture. An unexpected result was that under our experimental conditions in the SDR oxygen did not have any influence on the methane conversion. Almost the totality of added oxygen is recovered intact. Moreover, part of the H2 produced was transformed into water by reaction with O2. A model describing the chemical processes based on classical thermodynamics is also proposed. The results indicate that the reactor design has to be improved in order to increase conversion and hydrogen production. [source] | ||||||||||