scholarly journals Performance of Pd-Based Membranes and Effects of Various Gas Mixtures on H2 Permeation

Environments ◽  
2018 ◽  
Vol 5 (12) ◽  
pp. 128 ◽  
Author(s):  
Kourosh Kian ◽  
Caleb Woodall ◽  
Jennifer Wilcox ◽  
Simona Liguori
Keyword(s):  
Composite Membranes ◽  
Space Velocity ◽  
Operating Conditions ◽  
X Ray Diffraction ◽  
Initial Value ◽  
Exponential Factor ◽  
Steam Methane Reforming ◽  
Steam Methane ◽  
Pd Membrane ◽  
The Ideal

H2 permeation and separation properties of two Pd-based composite membranes were evaluated and compared at 400 °C and at a pressure range of 150 kPa to 600 kPa. One membrane was characterized by an approximately 8 μm-thick palladium (Pd)-gold (Au) layer deposited on an asymmetric microporous Al2O3 substrate; the other membrane consisted of an approximately 11 μm-thick pure palladium layer deposited on a yttria-stabilized zirconia (YSZ) support. At 400 °C and with a trans-membrane pressure of 50 kPa, the membranes showed a H2 permeance of 8.42 × 10−4 mol/m2·s·Pa0.5 and 2.54 × 10−5 mol/m2·s·Pa0.7 for Pd-Au and Pd membranes, respectively. Pd-Au membrane showed infinite ideal selectivity to H2 with respect to He and Ar at 400 °C and a trans-membrane pressure of 50 kPa, while the ideal selectivities for the Pd membrane under the same operating conditions were much lower. Furthermore, the permeation tests for ternary and quaternary mixtures of H2, CO, CO2, CH4, and H2O were conducted on the Pd/YSZ membrane. The H2 permeating flux decreased at the conclusion of the permeation tests for all mixtures. This decline however, was not permanent, i.e., H2 permeation was restored to its initial value after treating the membrane with H2 for a maximum of 7 h. The effects of gas hourly space velocity (GHSV) and the steam-to-carbon (S/C) ratio on H2 permeation were also investigated using simulated steam methane reforming mixtures. It was found that H2 permeation is highest at the greatest GHSV, due to a decline in the concentration polarization effect. Variations in S/C ratio however, showed no significant effect on the H2 permeation. The permeation characteristics for the Pd/YSZ membrane were also investigated at temperatures ranging from 350 to 400 °C. The pre-exponential factor and apparent activation energy were found to be 5.66 × 10−4 mol/m2·s·Pa0.7 and 12.8 kJ/mol, respectively. Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) analyses were performed on both pristine and used membranes, and no strong evidence of the formation of Pd-O or any other undesirable phases was observed.

Modeling of a Nickel-based Fluidized Bed Membrane Reactor for Steam Methane Reforming Process

2019 ◽  
Vol 41 (2) ◽  
pp. 219-219
Author(s):  
Mustafa Kamal Pasha Mustafa Kamal Pasha ◽  
Iftikhar Ahmad Iftikhar Ahmad ◽  
Jawad Mustafa Jawad Mustafa ◽  
Manabu Kano Manabu Kano
Keyword(s):  
Fluidized Bed ◽  
Membrane Reactor ◽  
Operating Conditions ◽  
Methane Reforming ◽  
Hydrogen Yield ◽  
Reactor Model ◽  
Membrane Area ◽  
Steam Methane Reforming ◽  
Steam Methane ◽  
Process Simulator

Hydrogen being a green fuel is rapidly gaining importance in the energy sector. Steam methane reforming is one of the most industrially important chemical reaction and a key step in the production of high purity hydrogen. Due to inherent deficiencies of conventional reforming reactors, a new concept based on fluidized bed membrane reactor is getting the focus of researchers. In this work, a nickel-based fluidized bed membrane reactor model is developed in the Aspen PLUSand#174; process simulator. A user-defined membrane module is embedded in the Aspen PLUSand#174; through its interface with Microsoftand#174; Excel. Then, a series combination of Gibbs reactors and membrane modules are used to develop a nickel-based fluidized bed membrane reactor. The model developed for nickel-based fluidized bed membrane reactor is compared with palladium-based membrane reactor in terms of methane conversion and hydrogen yield for a given panel of major operating parameters. The simulation results indicated that the model can accurately predict the behavior of a membrane reactor under different operating conditions. In addition, the model can be used to estimate the effective membrane area required for a given rate of hydrogen production.

scholarly journals Thermodynamic analysis of carbon formation conditions in a steam methane reforming process

2020 ◽  
pp. 136-136
Author(s):  
Dmitry Pashchenko ◽  
Maria Gnutikova
Keyword(s):  
Thermodynamic Analysis ◽  
Chemical Reactions ◽  
Operating Conditions ◽  
Mass Action ◽  
Equilibrium Analysis ◽  
Methane Reforming ◽  
Carbon Formation ◽  
Operational Conditions ◽  
Steam Methane Reforming ◽  
Steam Methane

Thermodynamic equilibrium analysis of the steam methane reforming process to synthesis gas was studied. For this purpose, the system of chemical reactions for carbon production and consumation as well as other side reaction in the steam methane reforming process were analysed. The material balance and the equations of law mass action were obtained for various chemical reactions. The system of those equations were solved by dichotomy method. The investigation was performed for a wide range of operational conditions such as a temperature, pressure, and inlet steam-to-methane ratio. The results obtained, with the help of developed algorithms, were compared with the results obtained via different commercial and open-source programs. All results are in excellent agreement. The operational conditions for the probable formation of carbon were determined. It was established that for the temperature range above 1100K the probability of carbon formation is absent for steam-to-methane ratio above units. The presented algorithm of thermodynamic analysis gives an appearance of the dependence of the product composition and the amount of required heat from operating conditions such as the temperature, pressure and steam-to-methane ratio.

scholarly journals Model Development and Exergy Analysis of a Microreactor for the Steam Methane Reforming Process in a CFD Environment

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 399
Author(s):  
Rahman ◽  
Ahmad ◽  
Kano ◽  
Mustafa
Keyword(s):  
Conversion Efficiency ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Operating Conditions ◽  
Methane Reforming ◽  
Cfd Model ◽  
Field Function ◽  
Efficient Operation ◽  
Steam Methane Reforming ◽  
Steam Methane

Steam methane reforming (SMR) is a dominant technology for hydrogen production. For the highly energy-efficient operation, robust energy analysis is crucial. In particular, exergy analysis has received the attention of researchers due to its advantage over the conventional energy analysis. In this work, an exergy analysis based on the computational fluid dynamics (CFD)-based method was applied to a monolith microreactor of SMR. Initially, a CFD model of SMR was developed using literature data. Then, the design and operating conditions of the microreactor were optimized based on the developed CFD model to achieve higher conversion efficiency and shorter length. Exergy analysis of the optimized microreactor was performed using the custom field function (CFF) integrated with the CFD environment. The optimized catalytic monolith microreactor of SMR achieved higher conversion efficiency at a smaller consumption of energy, catalyst, and material of construction than the reactor reported in the literature. The exergy analysis algorithm helped in evaluating length-wise profiles of all three types of exergy, namely, physical exergy, chemical exergy, and mixing exergy, in the microreactor.

Numerical Evaluation and Comparison of Different Reduced Mechanisms for Predicting the Performance of a SOFC Operating on Coal Syngas

2008 ◽  
Author(s):  
Francisco Elizalde-Blancas ◽  
Suryanarayana R. Pakalapati ◽  
Jose A. Escobar-Vargas ◽  
Ismail B. Celik
Keyword(s):  
A Priori ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Methane Reforming ◽  
Coal Syngas ◽  
Steam Methane Reforming ◽  
Steam Methane ◽  
Catalyzed Reactions ◽  
Shift Reaction ◽  
Water Gas

Three-dimensional numerical simulations of an anode supported button solid oxide fuel cell were performed using the code developed in house DREAM SOFC. The cell operates on coal syngas at atmospheric pressure and 1073 K. A gas phase mechanism and a heterogeneous mechanism are studied in this work to assess their influence on the performance of the button cell. Both mechanisms take into account the steam methane reforming reaction and water gas shift reaction. The implemented electrochemistry model allows the cell to simultaneously electrochemically oxidize H2 and CO. Results show that methane reforming from the bulk reactions is negligible compared to the catalyzed reactions. Also with a higher reformation the power delivered by the cell is improved. A small temperature difference of one degree is observed when both mechanisms are compared. The electrochemistry model does not require the ratio between current produced from H2 and CO to be prescribed a priori as an input. Under the operating conditions used in this study the model predicts the ratio to be around 4 for both mechanisms.

3D CFD Simulations of Local Carbon Formation in Steam Methane Reforming Catalyst Particles

2017 ◽  
Vol 15 (6) ◽  
Author(s):  
Mohsen Behnam ◽  
Anthony G. Dixon
Keyword(s):  
Hot Spots ◽  
Tube Wall ◽  
Particle Diameter ◽  
Catalyst Particle ◽  
Operating Conditions ◽  
Methane Reforming ◽  
Carbon Formation ◽  
Cfd Simulations ◽  
Steam Methane Reforming ◽  
Steam Methane

Abstract The deactivation of catalysts is an important problem in the strongly endothermic steam methane reforming reaction. The local carbon laydown on the catalyst surface may lead to local hot spots, breakage of catalyst particles, and blockage of the reactor tube. Local carbon formation was studied at different operating conditions using particle-scale 3D CFD models of full and hollow cylindrical particles. The results showed that a low steam-to-carbon ratio may cause local carbon formation at high temperature (\gt900K) on the surface of the catalyst particle. The risk of carbon formation was highest at the surface hot spots and inside the catalyst particles where the methane cracking reaction rate exceeded those of the gasification reactions. The internal surface in the 1-hole catalyst particle showed favorable conditions for carbon formation and deposition, similarly to the external surface of the particle. 3D CFD simulations of a 0.76 m length of a full tube of spherical catalyst particles with tube-to-particle diameter ratio 5.96 showed that the rate of carbon formation was much higher next to the heated tube wall and decreased significantly from the tube wall to the tube center.

scholarly journals Scenario-Based Techno-Economic Analysis of Steam Methane Reforming Process for Hydrogen Production

2021 ◽  
Vol 11 (13) ◽  
pp. 6021
Author(s):  
Shinje Lee ◽  
Hyun Seung Kim ◽  
Junhyung Park ◽  
Boo Min Kang ◽  
Churl-Hee Cho ◽  
...  
Keyword(s):  
Co2 Capture ◽  
H2 Production ◽  
Economic Feasibility ◽  
Operating Conditions ◽  
Methane Reforming ◽  
Steam Methane Reforming ◽  
Steam Methane ◽  
Process Configuration ◽  
Wide Range ◽  
Production Of Hydrogen

Steam methane reforming (SMR) process is regarded as a viable option to satisfy the growing demand for hydrogen, mainly because of its capability for the mass production of hydrogen and the maturity of the technology. In this study, an economically optimal process configuration of SMR is proposed by investigating six scenarios with different design and operating conditions, including CO2 emission permits and CO2 capture and sale. Of the six scenarios, the process configuration involving CO2 capture and sale is the most economical, with an H2 production cost of $1.80/kg-H2. A wide range of economic analyses is performed to identify the tradeoffs and cost drivers of the SMR process in the economically optimal scenario. Depending on the CO2 selling price and the CO2 capture cost, the economic feasibility of the SMR-based H2 production process can be further improved.

scholarly journals Multi-Scale Studies of 3D Printed Mn–Na–W/SiO2 Catalyst for Oxidative Coupling of Methane

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 290
Author(s):  
Tim Karsten ◽  
Vesna Middelkoop ◽  
Dorota Matras ◽  
Antonis Vamvakeros ◽  
Stephen Poulston ◽  
...  
Keyword(s):  
Oxidative Coupling ◽  
Oxidative Coupling Of Methane ◽  
Operating Conditions ◽  
Homogeneous Distribution ◽  
Silica Support ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Multi Scale ◽  
3D Printed

This work presents multi-scale approaches to investigate 3D printed structured Mn–Na–W/SiO2 catalysts used for the oxidative coupling of methane (OCM) reaction. The performance of the 3D printed catalysts has been compared to their conventional analogues, packed beds of pellets and powder. The physicochemical properties of the 3D printed catalysts were investigated using scanning electron microscopy, nitrogen adsorption and X-ray diffraction (XRD). Performance and durability tests of the 3D printed catalysts were conducted in the laboratory and in a miniplant under real reaction conditions. In addition, synchrotron-based X-ray diffraction computed tomography technique (XRD-CT) was employed to obtain cross sectional maps at three different positions selected within the 3D printed catalyst body during the OCM reaction. The maps revealed the evolution of catalyst active phases and silica support on spatial and temporal scales within the interiors of the 3D printed catalyst under operating conditions. These results were accompanied with SEM-EDS analysis that indicated a homogeneous distribution of the active catalyst particles across the silica support.

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