Effect of scale-up on the performance of a fluidized-bed reactor for the oxidative coupling of methane

Pannek, U.; Mleczko, Lesław

doi:10.1016/s0009-2509(97)00001-8

Cited by 13 publications

(13 citation statements)

References 11 publications

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“…This explanation is also supported by high COICO, ratios and selectivities to hydrogen measured in these reactors (not shown), since CO and H2 are primary products of the homogenous oxidation of methane (Zanthoff and Baerns, 1990;Do et al, 1995). Simulations of the oxidative coupling of methane in a fluidized-bed reactor (Pannek and Mleczko, 1997) showed that gas-phase reactions are initiated mainly by the C,+ hydrocarbons. This effect reduces the light-off temperature and the induction period.…”

Section: Factors Influencing C2 Selectivity and Yield In Various Reacmentioning

confidence: 65%

“…Up to the present, only results of reaction engineering modeling and simulations can be used to assess the performance of industrial-scale bubbling-bed and riser reactors. The simulations of a commercial bubbling-bed reactor indi-CH, + 0, cated that scale-up of this reactor type is associated with a significant drop of C2+ selectivity and yield (Pannek and Mleczko, 1997). The large bubbles in the industrial reactor caused intensification of backmixing of gas in the emulsion phase and suppressed interphase gas exchange.…”

Section: Optimal Reactor Type For Large-scale Applicationmentioning

confidence: 99%

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Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Mleczko

Marschall

1997

Can J Chem Eng

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The oxidative coupling of methane to C2-hydrocarbons (OCM) over a La2031Ca0 catalyst (27 at.%) was investigated in an internally circulating fluidized-bed (ICFB) reactor (IDe,).= 1.9 cm, H,.isl,r = 20.5 cm). The experiments were performed in the following range of conditions: T = 8O0-90O0C, pcH4:po2:pN2 = 57.144: 1&22.9:20 kPa. The obtained C, selectivities and C, yields were compared with the corresponding data from a spouted-fluid-bed reactor (ID = 5 cm) and a bubbling fluidized-bed (FIB) reactor (ID = 5 cm). The maximum C, yield in the internally circulating fluidized-bed (ICFB) reactor amounted to 12.2% ( T = 860"C, 38.7% C, selectivity, 3 1.5% methane conversion), whereas in the FIB reactor a maximum C2 yield of 13.8% ( T = 840°C, 40.4% C, selectivity, 34.2% methane conversion) was obtained. The lowest Cz yield was achieved in the spouted-bed (SFB) reactor (&? = 1 1.6%, T = 84OoC, 36.2% C, selectivity, 32.0% methane conversion). The highest space-time yield of 24.0 mol/kg,,;h was obtained in the ICFB reactor, whereas in a FIB reactor only a space-time yield of 9.6 mol/kg,,,~h could be obtained. Keywords: internally circulating fluidized-bed reactor, oxidative coupling, methane.xidative coupling of methane (OCM) to higher hydro-0 carbons is a possible route to convert natural gas into chemical or petrochemical feedstocks. However, further improvement of the catalytic performance by developing more selective catalysts and also by reaction engineering methods is necessary to make this process commercially viable (Mleczko and Baerns, 1995). The main engineering challenge is given by the temperature control and the management of the large amounts of heat generated in the reaction. From this point of view, a fluidized bed seems to be the most suitable reactor type to perform this reaction in a controlled manner. In laboratory-scale fluidized beds for several catalysts, e.g. a La2031Ca0 catalyst (Mleczko et al., 1996a), a LilSnlMgO catalyst (Santos et al., 1995) or a (Sro 125Mgo.,,5)C03 catalyst (Do et al., 1994), C2+ yields above 15% or even slightly higher have been reported. C2+ selectivities and yields obtained in fluidized-bed reactors were comparable and under certain conditions even better than in fixed beds (Follmer et al., 1988;Do et al., 1995;Mleczko et al., 1996a). However, lower selectivities and yields have also been reported (e.g. Mleczko et al., 1996b).In order to explain these contradictory results, the complex interaction between the bed hydrodynamics and kinetics of chemical reactions on the product distribution has to be taken into account, i.e. when performing oxidative coupling *Author to whom correspondence should be addressed. E-mail address: L.Mleczko@risc.techem.ruhr-uni-bochurn.de of methane in fluidized-bed reactors, Cz+ selectivity was influenced by mass transport limitation between bubbles and the emulsion as well as by the backmixing of gas in the emulsion. At high temperatures and partial pressures of oxygen, the mass transport restrictions and backmixing of gas suppressed high s...

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Section: Factors Influencing C2 Selectivity and Yield In Various Reacmentioning

confidence: 65%

Section: Optimal Reactor Type For Large-scale Applicationmentioning

confidence: 99%

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Mleczko

Marschall

1997

Can J Chem Eng

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“…Pannek and Mleczko modeled and simulated OCM in a fluidized‐bed reactor, and observed C 2 yields up to 17% which is slightly higher than those obtained in packed‐beds. The same authors also concluded that, in an industrial fluidized‐bed reactor, C 2 yields will be lower when compared with a lab‐scale reactor, due to larger contact times . Kruglov et al .…”

Section: Introductionmentioning

confidence: 95%

“…Control of temperature, residence time and its distribution depends strongly on the structure and geometry of the catalytic reactor. Even though many studies have been carried out for formulating catalysts to achieve high methane conversion together with improved product selectivity and ethylene yield, the number of studies addressing the effect of reactor type and structure is scarce . The very first reactors used to test OCM were packed‐bed type, which led to the formation of axial and radial temperature gradients in the reactor due to the high exothermicity .…”

Section: Introductionmentioning

confidence: 99%

Parametric investigation of oxidative coupling of methane in a heat‐exchange integrated microchannel reactor

Tezcan

Avcı

2014

J of Chemical Tech & Biotech

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BACKGROUND Oxidative coupling of methane (OCM) to C2 hydrocarbons is strongly exothermic and requires careful management of the dissipated heat. Running OCM in microchannel reactors offers fast heat transfer rates that enable controlled distribution of reaction temperature and product composition. This study involves modeling and simulation of OCM in a heat exchange integrated microchannel reactor involving parallel reaction and cooling channels separated by solid walls. RESULTS Using separating wall with high thermal conductivity and thickness above 5 × 10‐4 m regulates temperature distribution along the reaction channel and improves C2 yield. Increasing the methane‐to‐oxygen ratio decreases the reaction temperature and conversion immediately. Coolant inlet temperature affects the trade‐off between methane conversion and selective production of ethane and ethylene. Exothermic heat release and C2 hydrocarbon loss by oxidation are pronounced at higher reactant mass flow rates, whereas C2 yield is improved at higher coolant mass flow rates that dampen the reaction temperature. CONCLUSION Effective heat transfer and improved temperature control can be obtained in the microchannel geometry. The results provide insight into the potential use of microreactors, novel units known to have robust heat transfer properties, in controlling the temperature of the OCM process, which is one of the key design targets affecting product selectivity. © 2014 Society of Chemical Industry

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“…Due to the mass transport limitation between bubbles and emulsion phase and the backmixing of gas in the emulsion C 2+ selectivities and yields obtained in laboratoryscale fluidized-bed reactors operated in the bubbling regime were often lower than in fixed beds [6±7]. Since these effects are enhanced in an industrial reactor, a scale-up of bubbling beds to an industrial unit can result in a further significant drop of the C 2+ yield, e.g., in the simulations performed for a La 2 O 3 / CaO catalyst a drop of the C 2+ yield from 18% to 12% was predicted when scaling up from a laboratory reactor (ID = 5 cm) to an industrial unit (ID = 4 m, [8]). Against this background a circulating fluidized bed (CFB, see Fig.…”

Section: Introductionmentioning

confidence: 99%

Reaction Engineering Simulations of Oxidative Coupling of Methane in a Circulating Fluidized-Bed Reactor

Pannek

Mleczko

1998

Chem. Eng. Technol.

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Oxidative coupling of methane in a circulating fluidized bed (ID = 1 m, H = 20 m) was investigated by means of reaction engineering modeling and simulations. The hydrodynamics of the catalytic bed was described applying a two-phase (core and annulus) and two-zone (acceleration and fully developed flow) model. Chemical reactions were described by two separate networks for the heterogeneous and homogeneous reactions. The one for the heterogeneous steps was developed for a La 2 O 3 / CaO catalyst. Concentration profiles revealed that due to the high activity of the catalyst, almost complete conversion of oxygen was already obtained in the acceleration zone. Reactor performance was found to be strongly influenced by mass transport limitation between the core and annulus and by gas-phase reactions. The maximum C 2+ yield of 13% (T = 800 C, X CH4 = 34.5%, S C2+ = 37.5%) was obtained at a high solids circulation rate (G s = 800 kg/m 2 s) and a low methane-to-oxygen ratio (CH 4 /O 2 = 3).The C 2+ yields in the CFB are comparable to the ones predicted for an industrial-scale bubbling-bed reactor.

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Effect of scale-up on the performance of a fluidized-bed reactor for the oxidative coupling of methane

Cited by 13 publications

References 11 publications

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Performance of an internally circulating fluidized‐bed reactor for the catalytic oxidative coupling of methane

Parametric investigation of oxidative coupling of methane in a heat‐exchange integrated microchannel reactor

Reaction Engineering Simulations of Oxidative Coupling of Methane in a Circulating Fluidized-Bed Reactor

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