scholarly journals Thermodynamic Insight in Design of Methanation Reactor with Water Removal Considering Nexus between CO2 Conversion and Irreversibilities

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7861
Author(s):  
Sayed Ebrahim Hashemi ◽  
Kristian M. Lien ◽  
Magne Hillestad ◽  
Sondre K. Schnell ◽  
Bjørn Austbø
Keyword(s):  
Energy Use ◽  
Homogeneous Model ◽  
Fixed Bed ◽  
Energy Systems ◽  
Fixed Bed Reactor ◽  
Water Removal ◽  
Intermediate Water ◽  
Co2 Conversion ◽  
Co2 Methanation ◽  
In Series

The inevitable nexus between energy use and CO2 emission necessitates the development of sustainable energy systems. The conversion of CO2 to CH4 using green H2 in power-to-gas applications in such energy systems has attracted much interest. In this context, the present study provides a thermodynamic insight into the effect of water removal on CO2 conversion and irreversibility within a CO2 methanation reactor. A fixed-bed reactor with one intermediate water removal point, representing two reactors in series, was modeled by a one-dimensional pseudo-homogeneous model. Pure CO2 or a mixture of CO2 and methane, representing a typical biogas mixture, were used as feed. For short reactors, both the maximum conversion and the largest irreversibilities were observed when the water removal point was located in the middle of the reactor. However, as the length of the reactor increased, the water removal point with the highest conversion was shifted towards the end of the reactor, accompanied by a smaller thermodynamic penalty. The largest irreversibilities in long reactors were obtained when water removal took place closer to the inlet of the reactor. The study discusses the potential benefit of partial water removal and reactant feeding for energy-efficient reactor design.

Dynamic modeling and simulations of the behavior of a fixed-bed reactor-exchanger used for CO2 methanation

AIChE Journal ◽  
2017 ◽  
Vol 64 (2) ◽  
pp. 468-480 ◽  
Author(s):  
Rasmey Try ◽  
Alain Bengaouer ◽  
Pierre Baurens ◽  
Christian Jallut
Keyword(s):  
Dynamic Modeling ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Modeling And Simulations ◽  
Co2 Methanation

Novel bifunctional catalysts based on crystalline multi-oxide matrices containing iron ions for CO2 hydrogenation to liquid fuels and chemicals

2016 ◽  
Vol 188 ◽  
pp. 545-563 ◽  
Author(s):  
N. Utsis ◽  
R. Vidruk-Nehemya ◽  
M. V. Landau ◽  
M. Herskowitz
Keyword(s):  
Active Sites ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Liquid Fuels ◽  
Metallic Oxide ◽  
Fe Oxide ◽  
Carbide Phases ◽  
Rwgs Reaction ◽  
In Series ◽  
Water Inhibition

Seven solid mono-, bi- and tri-metallic oxide matrices where Fe(2+,3+) ions are distributed in different chemical/spatial environments were synthesized and characterized by XRD, N2-adsorption and EDAX methods. After basification with potassium, all matrices were activated by carburization or reduction–carburization under conditions selected based on the TPC/TPR spectra, tailoring the carburization extent of iron. The performances of the activated Fe-based catalysts with respect to CO2 conversion and C5+ selectivity were measured in a fixed-bed reactor under standard conditions in transient and continuous operation modes in units containing one or three reactors in series with water separations between the reactors. The catalysts were characterized by XRD, N2-adsorption, HRTEM-EELS and XPS before and after steady-state operation in the reactors. It was found that the rate of CO2 conversion is not limited by thermodynamic equilibrium but is strongly restricted by water inhibition and it depends on the nature of the Fe-oxide precursor. The ratio between the FTS and RWGS rates, which determines the C5+ hydrocarbons productivity, is strongly affected by the nature of the Fe-oxide matrix. The catalysts derived from the Fe–Al–O spinel and Fe–Ba–hexaaluminate precursors displayed the best balance of the two functions RFTS/RRWGS = 0.77–0.78. They were followed by magnetite, CuFe–delafossite, K–ferrite, Fe–La–hexaaluminate and LaFe–perovskite with a gradual lowering of RFTS/RRWGS from 0.60 to 0.15 and a gradual decrease in the C5+ productivity. The active sites that enhance the RWGS reaction are located on the surface of the Fe-oxide phases, while the FTS and methanation reactions occur on the surface of the Fe-carbide phases.

Dynamic simulation of the CO2 methanation in a micro-structured fixed-bed reactor

2019 ◽  
Vol 195 ◽  
pp. 541-552 ◽  
Author(s):  
Bjarne Kreitz ◽  
Gregor D. Wehinger ◽  
Thomas Turek
Keyword(s):  
Dynamic Simulation ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Co2 Methanation

scholarly journals High Selectivity and Stability of Nickel Catalysts for CO2 Methanation: Support Effects

Catalysts ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 24 ◽  
Author(s):  
Jeremías Martínez ◽  
Edgar Hernández ◽  
Salvador Alfaro ◽  
Ricardo López Medina ◽  
Guadalupe Valverde Aguilar ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Fixed Bed ◽  
Tetragonal Zirconia ◽  
Nickel Catalysts ◽  
Fixed Bed Reactor ◽  
Molar Ratio ◽  
Methane Formation ◽  
Co2 Methanation ◽  
X Ray

In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and sol-gel, while Ni was incorporated by impregnation (10–20 wt %). X-ray diffraction, nitrogen physisorption, temperature-programmed reduction, H2 pulse chemisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were the main characterization techniques employed. A laboratory fixed-bed reactor operated at atmospheric pressure, a temperature range of 350–500 °C, and a stoichiometric H2/CO2 molar ratio was used for catalyst evaluation. The most outstanding results were obtained with nickel catalysts supported on ZrO2 with CO2 conversions of close to 60%, and selectivity to methane formation was 100% on a dry basis, with high stability after 250 h of reaction time. The majority presence of tetragonal zirconia, as well as the strong Ni–ZrO2 interaction, were responsible for the high catalytic performance of the Ni/ZrO2 catalysts.

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 Effect of hydraulic retention time on hydrodynamic behavior of anaerobic-aerobic fixed bed reactor treating cattle slaughterhouse effluent

2017 ◽  
Vol 39 (4) ◽  
pp. 469 ◽  
Author(s):  
Daiane Cristina de Freitas ◽  
Fernando Hermes Passig ◽  
Cristiane Kreutz ◽  
Karina Querne de Carvalho ◽  
Eudes José Arantes ◽  
...  
Keyword(s):  
Flow Regime ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Fixed Bed ◽  
Theoretical Models ◽  
Fixed Bed Reactor ◽  
Bromophenol Blue ◽  
Eosin Y ◽  
Hydrodynamic Behavior ◽  
In Series

The study of the hydrodynamic behavior in reactors provides characteristics of the flow regime and its anomalies that can reduce biological processes efficiency due to the decrease of the useful volume and the hydraulic retention time required for the performance of microbial activity. In this study, the hydrodynamic behavior of an anaerobic-aerobic fixed bed reactor, operated with HRT (hydraulic retention time) of 24, 18 and 12 hours, was evaluated in the treatment of raw cattle slaughterhouse wastewater. Polyurethane foam and expanded clay were used as support media for biomass immobilization. Experimental data of pulse type stimulus-response assays were performed with eosin Y and bromophenol blue, and adjusted to the single-parameter theoretical models of dispersion and N-continuous stirred tank reactors in series (N-CSTR). N-CSTR model presented the best adjustment for the HRT and tracers evaluated. RDT (residence time distribution) curves obtained with N-CSTR model in the assays with bromophenol blue resulted in better adjustment compared to the eosin Y. The predominant flow regime in AAFBR (anaerobic aerobic fixed bed reactor) is the N-CSTR in series, as well as the existence of preferential paths and hydraulic short-circuiting. 

Design and Optimization of a Fixed Bed Reactor for Direct Dimethyl Ether Production from Syngas Using Differential Evolution Algorithm

2013 ◽  
Vol 11 (1) ◽  
pp. 147-158 ◽  
Author(s):  
Reza Vakili ◽  
Reza Eslamloueyan
Keyword(s):  
Differential Evolution ◽  
Dimethyl Ether ◽  
Large Scale ◽  
Homogeneous Model ◽  
Fixed Bed ◽  
Differential Evolution Algorithm ◽  
Operating Conditions ◽  
Fixed Bed Reactor ◽  
Scale Production ◽  
Design And Optimization

Abstract Dimethyl ether (DME) is traditionally produced by methanol dehydration in an adiabatic reactor. Recently, a more economical method has been proposed to produce DME in a reactor in which methanol production and dehydration take place simultaneously on a bi-functional catalyst. In the present study, the design and optimization of an industrial scale fixed bed reactor for the direct synthesis of DME from syngas are investigated. A steady state, pseudo-homogeneous model has been applied to simulate the proposed reactor. At first, the preliminary design of the reactor is done based on the reactor design heuristics for industrial reactors. Then, using differential evolution (DE) algorithm as a fast and efficient optimization method, the tentative reactor operating conditions and its internal configuration are optimized. The objective of the optimization is to maximize DME production in each tube of the reactor. The number of tubes, feed inlet and coolant water temperatures are considered as decision variables of the optimization algorithm. At the optimum conditions, the reactor size decreases due to increase of CO conversion and DME productivity in each tube. The results show that the proposed optimum reactor is more economical for large-scale production of DME in comparison to the conventional industrial DME reactor.

scholarly journals A Microwave-Assisted Boudouard Reaction: A Highly Effective Reduction of the Greenhouse Gas CO2 to Useful CO Feedstock with Semi-Coke

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1507
Author(s):  
Huan Dai ◽  
Hong Zhao ◽  
Siyuan Chen ◽  
Biao Jiang
Keyword(s):  
Carbon Dioxide ◽  
Microwave Heating ◽  
Barium Carbonate ◽  
Fixed Bed ◽  
Potential Method ◽  
Fixed Bed Reactor ◽  
Conventional Heating ◽  
Boudouard Reaction ◽  
Co2 Conversion ◽  
Microwave Assisted

The conversion of CO2 into more synthetically flexible CO is an effective and potential method for CO2 remediation, utilization and carbon emission reduction. In this paper, the reaction of carbon-carbon dioxide (the Boudouard reaction) was performed in a microwave fixed bed reactor using semi-coke (SC) as both the microwave absorber and reactant and was systematically compared with that heated in a conventional thermal field. The effects of the heating source, SC particle size, CO2 flow rate and additives on CO2 conversion and CO output were investigated. By microwave heating (MWH), CO2 conversion reached more than 99% while by conventional heating (CH), the maximum conversion of CO2 was approximately 29% at 900 °C. Meanwhile, for the reaction with 5 wt% barium carbonate added as a promoter, the reaction temperature was significantly reduced to 750 °C with an almost quantitative conversion of CO2. Further kinetic calculations showed that the apparent activation energy of the reaction under microwave heating was 46.3 kJ/mol, which was only one-third of that observed under conventional heating. The microwave-assisted Boudouard reaction with catalytic barium carbonate is a promising method for carbon dioxide utilization.

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