scholarly journals Kinetics and Reactor Design Aspects of Selective Methanation of CO over a Ru/γ-Al2O3 Catalyst in CO2/H2 Rich Gases

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 469 ◽  
Author(s):  
Panagiota Garbis ◽  
Christoph Kern ◽  
Andreas Jess
Keyword(s):  
Polymer Electrolyte Membrane ◽  
Fixed Bed ◽  
Kinetic Equations ◽  
Fixed Bed Reactor ◽  
Water Gas Shift ◽  
Co2 Methanation ◽  
Co Methanation ◽  
Electrolyte Membrane ◽  
Selective Co Methanation ◽  
Water Gas

Polymer electrolyte membrane fuel cells (PEMFCs) for household applications utilize H2 produced from natural gas via steam reforming followed by a water gas shift (WGS) unit. The H2-rich gas contains CO2 and small amounts of CO, which is a poison for PEMFCs. Today, CO is mostly converted by addition of O2 and preferential oxidation, but H2 is then also partly oxidized. An alternative is selective CO methanation, studied in this work. CO2 methanation is then a highly unwanted reaction, consuming additional H2. The kinetics of CO methanation in CO2/H2 rich gases were studied with a home-made Ru catalyst in a fixed bed reactor at 1 bar and 160–240 °C. Both CO and CO2 methanation can be well described by a Langmuir Hinshelwood approach. The rate of CO2 methanation is slow compared to CO. CO2 is directly converted to methane, i.e., the indirect route via reverse water gas shift (WGS) and subsequent CO methanation could be excluded by the experimental data and in combination with kinetic considerations. Pore diffusion may affect the CO conversion (>200 °C). The kinetic equations were applied to model an adiabatic fixed bed methanation reactor of a fuel cell appliance.

scholarly journals Selective CO Methanation Over Ru Supported on Carbon Spheres: The Effect of Carbon Functionalization on the Reverse Water Gas Shift Reaction

2018 ◽  
Vol 148 (11) ◽  
pp. 3502-3513 ◽  
Author(s):  
David O. Kumi ◽  
Mbongiseni W. Dlamini ◽  
Tumelo N. Phaahlamohlaka ◽  
Sabelo D. Mhlanga ◽  
Neil J. Coville ◽  
...  
Keyword(s):  
Water Gas Shift ◽  
Water Gas Shift Reaction ◽  
Carbon Spheres ◽  
Co Methanation ◽  
Reverse Water Gas Shift ◽  
Selective Co Methanation ◽  
Shift Reaction ◽  
Water Gas

scholarly journals Selective CO Methanation in H2-Rich Gas for Household Fuel Cell Applications

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2844 ◽  
Author(s):  
Panagiota Garbis ◽  
Andreas Jess
Keyword(s):  
Fuel Cell ◽  
Natural Gas ◽  
Fixed Bed ◽  
Cell System ◽  
Operating Conditions ◽  
Attractive Alternative ◽  
Inlet Temperature ◽  
Co2 Methanation ◽  
Co Methanation ◽  
Selective Co Methanation

Polymer electrolyte membrane fuel cells (PEMFCs) are often used for household applications, utilizing hydrogen produced from natural gas from the gas grid. The hydrogen is thereby produced by steam reforming of natural gas followed by a water gas shift (WGS) unit. The H2-rich gas contains besides CO2 small amounts of CO, which deactivates the catalyst used in the PEMFCs. Preferential oxidation has so far been a reliable process to reduce this concentration but valuable H2 is also partly converted. Selective CO methanation considered as an attractive alternative. However, CO2 methanation consuming the valuable H2 has to be minimized. The modelling of selective CO methanation in a household fuel cell system is presented. The simulation was conducted for single and two-stage adiabatic fixed bed reactors (in the latter case with intermediate cooling), and the best operating conditions to achieve the required residual CO content (100 ppm) were calculated. This was done by varying the gas inlet temperature as well as the mass of the catalyst. The feed gas represented a reformate gas downstream of a typical WGS reaction unit (0.5%–1% CO, 10%–25% CO2, and 5%–20% H2O (rest H2)).

CO2 Sorption by Hydrotalcite-Like Compounds in Dry and Wet Conditions

2015 ◽  
Vol 13 (3) ◽  
pp. 335-349 ◽  
Author(s):  
Katia Gallucci ◽  
Francesca Micheli ◽  
Alessandro Poliandri ◽  
Leucio Rossi ◽  
Pier Ugo Foscolo
Keyword(s):  
Thermal Treatment ◽  
Fixed Bed ◽  
Flow Distribution ◽  
Experimental System ◽  
Xrd Analysis ◽  
Fixed Bed Reactor ◽  
Water Gas Shift ◽  
Distribution Model ◽  
Time Flow ◽  
Water Gas

Abstract A pre-combustion removal option, coupling water–gas shift and CO2 capture is the well-known sorption-enhanced water–gas shift (SEWGS): the removal of CO2 produced by WGS reaction, shifting the thermodynamic equilibrium, enhances H2 production. Among the different CO2 sorbents, hydrotalcite-like compounds work at the required intermediate temperature (T = 200–400°C). Using low supersaturation method, three different sorbents were synthesized. Sieved fractions were impregnated with 20%w/w K2CO3 and then dried and subjected to thermal treatment. Sample characterization was performed by means of FT-IR spectroscopy, XRD analysis and TG-DTA analysis. Sample analysis was carried out after synthesis, thermal treatment (calcination) and after fixed bed reactor capture tests. Sorption and desorption tests were performed in a fixed bed microreactor, under cyclic conditions, at temperature level of T = 350°C and P = 5 bar in dry and wet condition. The amount of CO2 captured by the sorbent in each test was quantified by means of a first order with dead time flow distribution model applied to the experimental system. Sorption capacity of sorbents in dry conditions increases of 30% with respect to previous atmospheric pressure results obtained in fluidized bed. These sorbents seem to be good candidates to be used as a bi-functional sorbent-catalyst for SEWGS.

Modeling and Simulation of a Packed-bed Reactor for Carrying out the Water-Gas Shift Reaction

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Yaidelin A. Manrique ◽  
Carlos V. Miguel ◽  
Diogo Mendes ◽  
Adelio Mendes ◽  
Luis M. Madeira
Keyword(s):  
Fixed Bed ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Fixed Bed Reactor ◽  
Water Gas Shift ◽  
Small Scale ◽  
Heterogeneous Model ◽  
Co Conversion ◽  
Reactor Operating ◽  
Water Gas

Abstract In this work the water-gas shift (WGS) process was addressed, with particular emphasis in the development of phenomenological models that can reproduce experimental results in a WGS reactor operating at low temperatures. It was simulated the conversion obtained in a fixed-bed reactor (PBR) packed with a Cu-based catalyst making use of a composed kinetic equation in which the Langmuir-Hinshelwood rate model was used for the lowest temperature range (up to 215 ºC), while for temperatures in the range 215 – 300 ºC a redox model was employed. Several packed-bed reactor models were then proposed, all of them without any fitting parameters. After comparing the simulations against experimental CO conversion data for different temperatures and space time values, it was concluded that the heterogeneous model comprising axial dispersion and mass transfer resistances shows the best fitting. This model revealed also good adherence to other experiments employing different feed compositions (CO and H2O contents); it predicts also the overall trend of increasing CO conversion with the total pressure. This modeling work is particularly important for small scale applications related with hydrogen production/purification for fuel cells.

Hydrogen Production via Low Temperature Water Gas Shift Reaction: Kinetic Study, Mathematical Modeling, Simulation and Optimization of Catalytic Fixed Bed Reactor using gPROMS

2017 ◽  
Vol 12 (3) ◽  
Author(s):  
Davood Mohammady Maklavany ◽  
Ahmad Shariati ◽  
Mohammad Reza Khosravi-Nikou ◽  
Behrooz Roozbehani
Keyword(s):  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Water Gas Shift ◽  
Optimal Controls ◽  
Water Gas Shift Reaction ◽  
Hydrogen Formation ◽  
Simulation And Optimization ◽  
Modeling Simulation ◽  
Shift Reaction ◽  
Water Gas

Abstract The kinetics study, modeling, simulation and optimization of water gas shift reaction were performed in a catalytic fixed bed reactor. The renowned empirical power law rate model was used as rate equation and fitted to experimental data to estimate the kinetics parameters using gPROMS. A good fit between predicted and experimental CO conversion data was obtained. The validity of the kinetic model was then checked by simulation of plug flow reactor which shows a good agreement between experimental and predicted values of the reaction rate. Subsequently, considering axial dispersion, a homogeneous model was developed for simulation of the water-gas shift reactor. The simulation results were also validated by checking the pressure drop of the reactor as well as the mass concentration at equilibrium. Finally, a multi-objective optimization was conducted for water-gas shift reaction in order to maximize hydrogen formation and carbon monoxide conversion, whereas the reactor volume to be minimized. Implementation of optimal controls leads to increase in hydrogen formation at reactor outlet up to 25.55 %.

Development of Water Gas Shift Supported Catalysts for Fuel Processor Units

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Sabina Fiorot ◽  
Camilla Galletti ◽  
Stefania Specchia ◽  
Guido Saracco ◽  
Vito Specchia
Keyword(s):  
Supported Catalysts ◽  
Polymer Electrolyte Membrane ◽  
Water Gas Shift ◽  
Small Scale ◽  
Fuel Processor ◽  
Electrolyte Membrane ◽  
Co Concentration ◽  
Equilibrium Conversion ◽  
Lower Temperature ◽  
Water Gas

Fuel Cell (FC) technology promises to be a viable alternative for small scale electric heat and power generation (combined heat and power units, CHP). Moreover, the polymer electrolyte membrane FC (PEM-FC) is currently considered the most suitable technology for vehicles, both for traction and as auxiliary power unit APU; the latter is used on boats and yachts too. The ideal fuel for the PEM-FC is pure H2 gas. However, due to the lack of H2 distribution infrastructures, the current way of producing H2 to feed PEM-FC involves the reforming of hydrocarbon feedstocks and the removing of the catalyst poison CO with a series of catalytic steps. Water Gas Shift (WGS) is an attractive option for CO conversion although, due to its exothermic nature (?H298°C = -41.1 kJ?mol-1), the equilibrium conversion is thermodynamically limited at high temperatures. In contrast, at low temperatures, the reaction rate is constrained by kinetics such that highly performing catalysts are necessary to provide adequate activity. For these reasons two WGS stages are generally employed: a high temperature stage (HT-WGS), which takes place between 400-500°C and reduces the CO concentration to about 2-5%, followed by a second shift at a lower temperature (LT-WGS), with a cooling stage in between, which is carried out over a temperature range of 200-400°C and reduces the CO concentration to about 0.5-1%. In this work, catalysts based on Pt and mixed Pt+Re on different supports were prepared and their catalytic activity was tested; moreover, a comparison with commercial catalysts was also carried out. Very promising results were obtained in the HT-WGS range as the catalytic performances of the prepared catalysts were superior to those reached by the commercial catalyst; therefore they can be considered as possible candidates for FC technology.

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