Transfer dynamics and reaction control mechanisms over methanation catalyst particles in transport bed
(2.University of Chinese Academy of Sciences, Beijing, China 100049)
(3.Shenyang University of Chemical Technology, Shenyang, Liaoning Province, China 110142)
【Abstract】The numerical simulation based on COMSOL Multiphysics was conducted to understand the dynamics of heat transfer and mechanism of reaction control over methanation catalyst particles in the size of about 100 μm under conditions of a transport bed. The high heat transfer efficiency in a transport bed makes the catalyst particle into the bed quickly approach its steady state in about 0.1 s, a very short transient period. For the catalyst particle in a steady state, there are temperatures sharing little difference among the particle center, particle surface, and gas flow bulk. However, it is clear that the temperature is still gradually lower from the center to the surface of the particle, and on the particle surface, its temperature is higher than that in fluid. This clarifies that the exothermic heat of methanation reaction first heats the catalyst particle, and the temperature-raised particle then reaches a balance of heat transfer with its surrounding gas. The calculation of the radial profiles of the temperature, gas components, and reaction rate inside the catalyst particle clarifies that for methanation at higher fluid temperature and elevated pressure (2 MPa here), the mass transfer into particles is quicker, and the CO consumption rate becomes gradually lower from the center to the surface of the particle. On the contrary, for atmospheric methanation at lower gas velocity, the reaction rate is conversely lower at the particle center. It demonstrates that the methanation reaction is subject to kinetic control for the former but to mass transfer for the latter.
【Keywords】 transport bed; methanation; coal-to-SNG; numerical simulation; heat transfer; dynamic behavior; reaction mechanism;
(Translated by HAN R)
 Rönsch S, Schneider J, Matthischke S, et al. Review on methanation–from fundamentals to current projects [J]. Fuel, 2016, 166: 276–296.
 Yan X, Liu Y, Wang Z, et al. Methanation over Ni/SiO2: effect of the catalyst preparation methodologies [J]. International Journal of Hydrogen Energy, 2013, 38 (5): 2283–2291.
 Cai M, Wen J, Chu W, et al. Methanation of carbon dioxide on Ni/ZrO2–Al2O3 catalysts: effects of ZrO2 promoter and preparation method of novel ZrO2–Al2O3 carrier [J]. Journal of Natural Gas Chemistry, 2011, 20 (3): 318–324.
 Ang M L, Oemar U, Kathiraser Y, et al. High-temperature water–gas shift reaction over Ni/xK/CeO2 catalysts: suppression of methanation via formation of bridging carbonyls [J]. Journal of Catalysis, 2015, 329: 130–143.
 Saw E T, Oemar U, Tan X R, et al. Bimetallic Ni–Cu catalyst supported on CeO2 for high-temperature water–gas shift reaction: Methane suppression via enhanced CO adsorption [J]. Journal of Catalysis, 2014, 314: 32–46.
 Liu H, Zou X, Lu X, et al. Effect of CeO2 addition on Ni/Al2O3 catalysts for methanation of carbon dioxide with hydrogen [J]. Journal of Natural Gas Chemistry, 2012, 21 (6): 703–707.
 Hu D C, Gao J J, Ping Y, et al. Enhanced investigation of CO methanation over Ni/Al2O3 catalysts for synthetic natural gas production [J]. Industrial & Engineering Chemistry Research, 2012, 51 (13): 4875–4886.
 Gao J J, Jia C M, Li J, et al. Nickel catalysts supported on barium hexaaluminate for enhanced CO methanation [J]. Industrial & Engineering Chemistry Research, 2012, 51 (31): 10345–10353.
 Xu G W, Liu J, Cui D M, et al. Method and device for catalytic methanation of synthesis gas: US 9758440 [P]. 2017-9-12.
 Liu J, Cui D M, Yao C B, et al. Syngas methanation in fluidized bed for an advanced two-stage process of SNG production [J]. Fuel Processing Technology, 2016, 141: 130–137.
 Liu J, Dui D M, Yu J, et al. Performance characteristics of fluidized bed syngas methanation over Ni–Mg/Al2O3 catalyst [J]. Chinese Journal of Chemical Engineering, 2015, 23 (1): 86–92.
 Cui D M, Liu J, Yu J, et al. Attrition-resistant Ni–Mg/Al2O3 catalyst for fluidized bed syngas methanation [J]. Catalysis Science & Technology, 2015, 5 (6): 3119–3129.
 Cui D M, Liu J, Yu J, et al. Attrition-resistant Ni–Mg/SiO2–Al2O3 catalysts with different silica sources for fluidized bed syngas methanation [J]. International Journal of Hydrogen Energy, 2017, 42 (8): 4987–4997.
 Liu J, Cui D M, Yu J, et al. Syngas methanation over spray granulated Ni/Al2O3 catalyst in a laboratory transport-bed reactor [J]. Chemical Engineering & Technology, 2019, 42 (1): 129–136.
 Liu J, Shen W L, Cui D M, et al. Syngas methanation for substitute natural gas over Ni–Mg/Al2O3 catalyst in fixed and fluidized bed reactors [J]. Catalysis Communications, 2013, 38: 35–39.
 Shin M S, Park N, Park M J, et al. Modeling a channel-type reactor with a plate heat exchanger for cobalt-based Fischer–Tropsch synthesis [J]. Fuel Processing Technology, 2014, 118: 235–243.
 Shin M S, Park N, Park M J, et al. Computational fluid dynamics model of a modular multichannel reactor for Fischer–Tropsch synthesis: maximum utilization of catalytic bed by microchannel heat exchangers [J]. Chemical Engineering Journal, 2013, 234: 23–32.
 Karim A, Bravo J, Gorm D, et al. Comparison of wall-coated and packed-bed reactors for steam reforming of methanol [J]. Catalysis Today, 2005, 110 (1): 86–91.
 Sutkar V S, Gogate P R, Csoka L. Theoretical prediction of cavitational activity distribution in sonochemical reactors [J]. Chemical Engineering Journal, 2010, 158 (2): 290–295.
 Barrientos J, González N, Lualdi M, et al. The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation [J]. Applied Catalysis A: General, 2016, 514: 91–102.
 Chein R Y, Yu C T, Wang C C. Numerical simulation on the effect of operating conditions and syngas compositions for synthetic natural gas production via methanation reaction [J]. Fuel, 2016, 185: 394–409.
 Ducamp J, Bengaouer A, Baurens A. Modelling and experimental validation of a CO2 methanation annular cooled fixed-bed reactor exchanger [J]. The Canadian Journal of Chemical Engineering, 2017, 95 (2): 241–252.
 Liu Y, Hinrichsen O. CFD Simulation of hydrodynamics and methanation reactions in a fluidized-bed reactor for the production of synthetic natural gas [J]. Industrial & Engineering Chemistry Research, 2014, 53 (22): 9348–9356.
 Engelbrecht N, Chiuta S, Everson R C, et al. Experimentation and CFD modelling of a microchannel reactor for carbon dioxide methanation [J]. Chemical Engineering Journal, 2017, 313: 847–857.
 Grace J R, Li T. Complementarity of CFD, experimentation and reactor models for solving challenging fluidization problems [J]. Particuology, 2010, 8 (6): 498–500.
 Chen X M, Xiao J, Zhu Y P, et al. Intraparticle mass and heat transfer modeling of methanol to olefins process on SAPO-34: a single particle model [J]. Industrial & Engineering Chemistry Research, 2013, 52 (10): 3693–3707.
 Solsvik J, Jakobsen H A. Modeling of multicomponent mass diffusion in porous spherical pellets: application to steam methane reforming and methanol synthesis [J]. Chemical Engineering Science, 2011, 66 (9): 1986–2000.
 Solsvik J, Jakobsen H A. A numerical study of a two property catalyst/sorbent pellet design for the sorption-enhanced steam methane reforming process: modeling complexity and parameter sensitivity study [J]. Chemical Engineering Journal, 2011, 178: 407–422.
 Solsvik J, Tangen S, Jakobsen H A. On the consistent modeling of porous catalyst pellets: mass and molar formulations [J]. Industrial & Engineering Chemistry Research, 2012, 51 (24): 8222–8236.
 Behnam M, Dixon A G, Nijemeisland M, et al. Catalyst deactivation in 3D CFD resolved particle simulations of propane dehydrogenation [J]. Industrial & Engineering Chemistry Research, 2010, 49 (21): 10641–10650.
 Solsvik J, Jakobsen H A. Multicomponent mass diffusion in porous pellets: effects of flux models on the pellet level and impacts on the reactor level. Application to methanol synthesis [J]. The Canadian Journal of Chemical Engineering, 2013, 91 (1): 66–76.
 Voss B, Schjødt N C, Grunwaldt J D, et al. Kinetics of acetic acid synthesis from ethanol over a Cu/SiO2 catalyst [J]. Applied Catalysis A: General, 2011, 402 (1): 69–79.
 Zhang X, Sui Z J, Zhou X G, et al. Modeling and simulation of coke combustion regeneration for coked Cr2O3/Al2O3 propane dehydrogenation catalyst [J]. Chinese Journal of Chemical Engineering, 2010, 18 (4): 618–625.
 Maroufi S, Khoshandam B, Kumar R V. Mathematical modelling of fluidized-bed reactors for non-catalytic gas–solid reactions [J]. The Canadian Journal of Chemical Engineering, 2010, 88 (6): 1034–1043.
 Novák V, KočíP, Marek M, et al. Multi-scale modelling and measurements of diffusion through porous catalytic coatings: an application to exhaust gas oxidation [J]. Catalysis Today, 2012, 188 (1): 62–69.
 Zhang J, Li T. Application of CFD to improve the calculated process of methanation over plum-shaped catalyst [J]. CIESC Journal, 2018, 69 (7): 2985–2992.
 Lim J Y, Dennis J S. Modeling reaction and diffusion in a spherical catalyst pellet using multicomponent flux models [J]. Industrial & Engineering Chemistry Research, 2012, 51 (49): 15901–15911.
 Xu J, Froment G. Methane steam reforming, methanation and water–gas shift (I): Intrinsic kinetics [J]. AIChE Journal, 1989, 35 (1): 88–96.
 Mihet M, Cristea V M, Agachi A M, et al. CFD simulations, experimental validation and parametric studies for the catalytic reduction of NO by hydrogen in a fixed bed reactor [J]. RSC Advances, 2016, 6 (92): 89259–89273.
 Wind T L, Falsig H, Sehested J, et al. Comparison of mechanistic understanding and experiments for CO methanation over nickel [J]. Journal of Catalysis, 2016, 342: 105–116.
 Mears D. Tests for transport limitations in experimental catalytic reactors [J]. Industrial & Engineering Chemistry Process Design and Development, 1972, 11: 320–320.