Bubble dynamics and its effect on the performance of a jet fluidised bed gasifier simulated using CFD

Gao, Kun; Wu, Jinhu; Zhang, Dongke

doi:10.1016/j.fuel.2005.11.013

Cited by 15 publications

(6 citation statements)

References 11 publications

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“…Unfortunately, the cloud phase behaviors and the bubble phase porosity have been exceptionally discussed in the bubbling and turbulent fluidized bed experimental literature. The same deficiency is usually observed in the rising fluidized bed numerical literature started by Ding and Gidaspow,19 whether the formalism is eulerian,20–24 or lagrangian 25–27. Visualization is often the major way to describe the hydrodynamics of the bubbles.…”

Section: Introductionmentioning

confidence: 86%

Behaviors of the bubble, cloud, and emulsion phases in a fluidized bed

Andreux

Chaouki

2007

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).An intrusive bioptical probe provides radial profiles of the PDF (probability density function) of the bubble, the cloud, and the emulsion phases behaviors in a fluidized bed of Geldart-A particles. The fluidizing velocity ranges between 0.20 and 0.80 m/s. The bed porosity, the overall averaged bubble chords and velocities are well-predicted by correlations of the literature. The cloud thickness is closely related to the bubble chord. The amount of gas traveling through the bubble phase never exceeds 15-20% of the total gas flow rate. The averaged porosity of the bubble, the cloud and the emulsion phases is of 88-92%, 65-70%, and 50-55%, respectively. The reduced bubble porosity distribution obeys a constant normal law over the fluidizing velocity range. Each distribution of the reduced bubble chord and velocity, and of the reduced cloud thickness obey a constant log normal law over the fluidizing velocity range.

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Section: Introductionmentioning

confidence: 86%

Behaviors of the bubble, cloud, and emulsion phases in a fluidized bed

Andreux

Chaouki

2007

AIChE Journal

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“…Based on hydrodynamics calculation of the previous AFB, the gasifier was divided into three parts, the jet zone, the annulus dense‐phase zone and the freeboard zone, and the combined equivalent reactor is illustrated in Figure a. In the jet zone, where the gas and solid are well mixed, a perfectly stirred reactor (PSR) is used to simulate this zone.…”

Section: Equivalent Reactor Model Setupmentioning

confidence: 99%

“…The calculation results cannot be obtained due to a rapid growth of the number of Navier‐Stokes differential equations. In another words, the CFD simulation can obtain results for the kilogram scale but not for the kiloton scale because of the corresponding mesh count for the commercial‐scale reactor will be appreciably larger than that for the smaller‐scale reactors, especially for coal gasification processes . During the coal gasification process, not only the hydrodynamics but also the coal particle size, density, and shape, change with the coal gasification reactions, making the gasification process much more complex than the CFD calculations.…”

Section: Introductionmentioning

confidence: 99%

Influence of ash agglomerating fluidized bed reactor scale‐up on coal gasification characteristics

et al. 2014

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To study the influence of fluidized-bed reactor scale-up on coal gasification characteristics, a model of the ash agglomerating fluidized-bed reactor has been developed using an equivalent reactor network method. With the reactor network model, the scale-up effects of a gasifier were studied in terms of the characteristics of the chemical reactions in the jet zone, the annulus dense-phase zone and the freeboard zone. Results showed that the changes occurred in the inequality proportion of the volume of the jet zone during the reactor scale-up. Taking into consideration the utilization of a portion of the backflow gas, the expansion of the jet zone volume and the coal particle residence time, the temperature of the jet zone was increased from 1592 to 1662 K. Also, both the annulus dense-phase zone temperature and the freeboard zone temperature decreased, causing subsequent decrease in the carbon conversion efficiency.

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“…Fluidized-bed coal gasification is regarded as one of the most effective means to use coal, especially high ash and high ash-melting point coals . It has been developed in pilot scale known as the U-gas process, the Westinghouse (now KRW) process in the U.S.A., and the institute of coal conversion (ICC) process in China .…”

Section: Introductionmentioning

confidence: 99%

“…Currently, literature on the scale-up of jetting bed reactors , has mainly concentrated on the discussion of cold-state flow behavior changes in the scaling process. , Because of the efficient mixing of gases and particles in the gasifier, it is very difficult to test either the temperature profile of the specific region or the jetting zone range at the same time during coal gasification. Researchers generally make measurements and predictions on the temperature profile by means of thermocouple measurements and numerical simulation [computational fluid dynamics (CFD) models], for example, bubble fluidized bed, , one-dimensional hydrodynamics, district, − particle track, and more dimensional model . However, these methods make it difficult to record the jetting bed temperature of any spot and are unable to demonstrate the impact of temperature changes on a specific region.…”

Section: Introductionmentioning

confidence: 99%

Thermochemical Process Study on a Jet-Fluidized-Bed Gasifier Reaction System by an Equivalent Chemical Reactor Network

et al. 2011

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To study the effects of operational parameters on gasifying characteristics in the jet-fluidized-bed reactor and illustrate the scaling relationships of jet-fluidized-bed coal gasifier in a scale-up process, we established an equivalent reactor network model for the gasifier using CHEMKIN 4.1 software. The model is based on hydrodynamic properties in the gasifier and knowledge of the burning zone and gasifying zone of the reactor. It involves two-phase flow between materials, heat and mass transfer, as well as the coal gasification process in the presence of mixed gases, most notably H 2 O, O 2 , N 2 , etc. The model was validated by comparing it to the experimental data of outlet gas compositions. To optimize characteristics of the jet-fluidized-bed coal gasifier, the influence of the oxygen feed rate into the center nozzle and the coal feed rate on the gasification process and gas composition were studied by the equivalent established reactor network. Within the calculation range, with the increase of the oxygen feed rate into the center nozzle, the jet region nearly doubled, the temperature increased by 306 K, carbon conversion efficiency rose from 68 to 97%; however, the temperature of the jetting region should be controlled within the coal ash-softening temperature, and in generated gases, the CO and H 2 contents had clearly changed. With the increase of the coal processing capacity, the jet region temperature decreased by 252 K, the gasifier overall temperature decreased, and carbon conversion reduced from 98 to 74%.

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Bubble dynamics and its effect on the performance of a jet fluidised bed gasifier simulated using CFD

Cited by 15 publications

References 11 publications

Behaviors of the bubble, cloud, and emulsion phases in a fluidized bed

Behaviors of the bubble, cloud, and emulsion phases in a fluidized bed

Influence of ash agglomerating fluidized bed reactor scale‐up on coal gasification characteristics

Thermochemical Process Study on a Jet-Fluidized-Bed Gasifier Reaction System by an Equivalent Chemical Reactor Network

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