Numerical modeling of the cavity phenomenon and its elimination way in rectangular radial moving bed reactor

He, Yi-Jun; Xiao, Fu; Luo, Zheng‐Hong

doi:10.1016/j.powtec.2015.01.014

Cited by 9 publications

(8 citation statements)

References 15 publications

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“…(1) The dust collector can sustain the high temperature of >400 C, and can resist the equipment corrosion by tar steam, H 2 S, and NH 3 in the volatiles. (2) In order to avoid the system failure, the temperature of the dust collector should not be lower than the pyrolysis temperature. Otherwise, the condensation of high viscosity tar together with dust will form tar residue and block the piping system.…”

Section: -10mentioning

confidence: 99%

“…1 The moving-bed coal pyrolysis technology has been paid much attention by researchers because of its stable operation, uniform heating and easier reactor amplication. [2][3][4] Moreover, the circulating uidized bed (CFB) combustion technology which is characterized by wide fuel exibility, high processing load and low pollution has been developed greatly. 5 This lays a foundation for the industrialization process of the poly-generation technology which combines CFB combustion with coal pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

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Studies of granular bed filter for dust removal in the process of coal pyrolysis by solid heat carrier

Zhang

Liang

et al. 2017

RSC Adv.

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Aiming at the optimization of the dust removal process in the poly-generation system of circulating fluidized bed (CFB) combustion/coal pyrolysis, a granular bed filter (GBF) is applied to the coal pyrolysis by solid heat carrier. By carrying out lab-scale experiments with a moving-bed pyrolyzer, the GBF model proposed by C. Tien et al. was used to describe the dust removal process of the dust-contained volatiles which has high temperature and high viscosity. The model applicability for real pyrolysis volatiles was verified. The results show that, the particle size distribution of the dust uncollected by the GBF is relatively concentrated. The majority particle size of uncollected dust is less than 20 mm, the mass fraction is $80%. The GBF is in a state of unsteady operation in the process of dust filtration. With the increase of operating time, the dust is gradually deposited in the GBF, then resulting in an increase of bed pressure drop. In the examined range, the calculational value of GBF efficiency is slightly lower than the experimental value. On the one hand, the filter media particles have a certain specific surface area, so that part of the dust-contained tar can be adsorbed on the filter media surface to achieve a better interception effect. On the other hand, the dust particle deposited in the GBF also plays an important role in dust capture. The C. Tien model results of the initial filtration efficiency can be used as the selection reference of the medium species and the physical properties of the GBF. The higher filter height, slower superficial gas velocity, and smaller size of medium are conducive to decrease the dust content in the pyrolysis products. This study can provide basic data for the dust removal process in the poly-generation system of CFB combustion/coal pyrolysis.

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Section: -10mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Studies of granular bed filter for dust removal in the process of coal pyrolysis by solid heat carrier

Zhang

Liang

et al. 2017

RSC Adv.

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“…6 In the feed influence zone, for instance, the so-called "solid seal" should be high enough in the case of gas short circuit. 19,21 In this sense, the gas flow pattern is not exactly the plug flow as part of the gas phase flows toward the ends of the bed. As a result, the radial pressure drop reduces gradually at the ends of the bed, 9,17 which indicates the appearance of the gas axial dispersion behavior.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, the flow pattern in the radial flow bed is investigated by many researchers, including some undesirable phenomena (e.g., cavity, ,− pinning, ,− air lock, , gas nonuniformity distribution ,− ), the simulation methods (e.g., single phase, ,,, Eulerian–Eulerian, ,, Eulerian–Lagrangian methods), the structural optimization (e.g., trapezoidal/conical bed, , baffles/Johnson-net/louvers ,, ), and the reaction process simulation (the flow pattern is usually assumed to be plug flow).…”

Section: Introductionmentioning

confidence: 99%

Gas Axial Dispersion Behavior and Gas Residence Time in the Radial Flow Bed

Wang

Fan

2017

Ind. Eng. Chem. Res.

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The gas flow pattern in the radial flow bed is simulated by porous and transport models combined with a 6-lump kinetic reaction model (C4 hydrocarbon catalytic pyrolysis), which are verified by the published experimental results. Aside from the simulation method, the gas axial dispersion behavior is well explained by introducing the “common pressure pool” (CPP) and the “constant pressure drop lines” (CPDL) methods. The most severe gas axial dispersion behavior occurs at the turning point of (r – r 1)/(r 2 – r 1) = 0.62. However, the gas flow pattern can still be roughly seen as a plug flow in whole bed for the small influences of the gas axial dispersion behavior. The appropriate gas residence time can then be determined by the plug flow model and the simulation method to achieve different production targets.

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“…Among them, the moving-bed reactor is particularly valued because of its stable operation, uniform heating and large range changes of gas-solid contact time. 2 In the whole pyrolysis system, the moving-bed pyrolyzer plays a critical role. 3 Its investigation of the heating process and reaction control factors has great significance to improve the utilization level of high-volatile coal in western China.…”

Section: Introductionmentioning

confidence: 99%

Simulation Study of Shenmu Coal Pyrolysis by Gas Heat Carrier Based on a Moving Bed

et al. 2015

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Coats-Redfern integral method combined with TG-MS technology was applied to study the evolution of the main pyrolysis products for Shenmu bituminous coal. And a heat transfer, reaction, numerical model of coal pyrolysis by gas heat carrier in a moving-bed reactor is developed. The model can predict the internal temperature profile and pyrolysis volatiles evolution of different coal species as well as the temperature distribution of gas heat carrier versus bed height. The results show that, when the temperature of gas heat carrier increases from 700°C to 900°C, the theoretical bed height of pyrolysis drops from 0.26 m to 0.14 m, and the maximum of devolatilization rate increases from 0.954 %·s -1 to 1.382 %·s -1 . The coal species have significant influence on their temperature-rise pyrolysis process in a gas heat carrier moving-bed reactor. Higher initial temperature or velocity of gas heat carrier, smaller particle size or moving velocity of coal tends to accelerate the devolatilization rate and shorten the pyrolysis time. This work may provide a theoretic foundation for the reactor amplification and different industrial condition prediction of high-volatile coal pyrolysis in a moving-bed reactor.

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Numerical modeling of the cavity phenomenon and its elimination way in rectangular radial moving bed reactor

Cited by 9 publications

References 15 publications

Studies of granular bed filter for dust removal in the process of coal pyrolysis by solid heat carrier

Studies of granular bed filter for dust removal in the process of coal pyrolysis by solid heat carrier

Gas Axial Dispersion Behavior and Gas Residence Time in the Radial Flow Bed

Simulation Study of Shenmu Coal Pyrolysis by Gas Heat Carrier Based on a Moving Bed

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