Unique properties of 30‐μm particles as the catalyst of fluidized‐bed reactors

Yang, Guoqiang; Wei, Fei; Ye, Jin; Yu, Z.M.; Wang, Yao

doi:10.1002/aic.690430509

Cited by 6 publications

(7 citation statements)

References 3 publications

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“…The collapsing curve has a sharp falling curve followed by a slower decline. The observed behavior was similar to that of the settling 3.18 curve of Yang, et al (1997) The critical velocity is 0.7 m/sec at a solid volume fraction of 0.02. It is similar to the Ding's experimental values (Gidaspow, et al 1986) in which the typical critical velocity value of the particulate phase was one meter per second.…”

Section: Pressure Drop and Minimumsupporting

confidence: 64%

University/NETL Student Partnership Program

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2003

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2 methane on the coal surfaces that may otherwise stay adsorbed in the coal matrix by decreasing the partial pressure of methane in the gas mixture. In addition, experimental work conducted on enhanced coalbed methane recovery by CO 2 injection [Reznik et al, 1984] shows that CO 2 is more adsorbing on coal than methane thereby giving it the potential to efficiently displace CBM and remain sequestered in the coal-seam. Thus coal-seams are considered to offer a very attractive option for CO 2 sequestration.In this work, focus is on the final part of the sequestration process -storage. The effects of various coal properties as well as operational scenarios on the injection and storage of CO 2 into a given coal-seam are analyzed. The analyses are based on results obtained from PSU-COALCOMP, a compositional coalbed methane numerical reservoir simulator capable of modeling the primary and enhanced recovery of coalbed methane.The operational design parameters considered in this study include the type, length and orientation of the injectors/producers while the coal-seam properties studied include coal porosity, coal permeability, cleat spacing, sorption capacity, and the initial conditions of the coal-seam -the reservoir pressure, adsorbed gas composition, amount of CO 2 initially adsorbed, water saturation and free-gas composition.Based on the data, results and analyses obtained, a CO 2 sequestration performance predictor tool is developed using artificial neural network (ANN) technology. The developed network will be able to predict the values of the performance indicators of the CO 2 sequestration process for a wide range of coal-seams and various production schemes. The developed ANN would also enhance our understanding of CO 2 sequestration process. 3 CHAPTER 2 LITERATURE REVIEW Carbon Dioxide SequestrationThe amount of carbon dioxide (CO 2 ) in the atmosphere has risen from preindustrial levels and most of this increase has been in recent years as shown in the data presented graphically in Figure 2-1. The corresponding increase in temperature as CO 2 levels increase raises environmental concerns such as global warming and its effects.This increase in CO 2 levels is attributed widely to the burning of fossil fuels, and if current trends in resource utilization continue, anthropogenic CO 2 emissions will increase rapidly during the 21 st century. Figure 2-2 shows the sharp increase in global CO 2 emissions over the last 100 years.The term "CO 2 sequestration" refers to the removal of CO 2 from either manmade emissions or the atmosphere and the safe, essentially permanent storage of this CO 2 .There are two main types of sequestration: direct sequestration, where CO 2 is removed from energy systems, and indirect sequestration, where CO 2 is removed from the ambient atmosphe re by enhanced natural processes. Sequestration is one of the three options for stabilizing CO 2 concentrations in the atmosphere and until the late 1990's, was not yet in the scientific lexicon. It is less familiar to the public at large than...

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Section: Pressure Drop and Minimumsupporting

confidence: 64%

University/NETL Student Partnership Program

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2003

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“…al. 1988 andYang et al 1997 observed that this happens so quickly that little useful data can be obtained. There is very little published data quantifying the rate of collapse of Geldart Group B particles.…”

Section: Geldart Groups and The Collapsing Fluidized-bed Experimentsmentioning

confidence: 99%

“…The collapse time for the bed containing Geldart Group C particles, as shown in Figure 12, is significantly longer than that of Geldart Groups A or B. Ž . As disucssed by Yang et al 1997 the faster collapse of fluidized beds containing Geldart Group C particles is due to the strong tendency for aggregation. This particle᎐particle attraction causes cracks or channels to form, allowing the gas to escape quickly.…”

Section: Simulation Of the Collapsing Fluidized Bedmentioning

confidence: 99%

“…The collapsing fluidized-bed experiment, first described by Ž . Rietema 1967 , has been used to understand the dense-phase regime of fluidization, and is still commonly used today ŽGeldart et al, 1984;Grace, 1992;Barreto et al, 1988;Tianxiong et al, 1982;Yang et al, 1997; . Formisani et al, 2002, for example .…”

Section: Introdutionmentioning

confidence: 99%

“…stages. Barreto et al 1988 andYang et al 1997 report entire collapse-rate curve data instead of only collapse-velocity values. These curves show a much faster bed collapse, followed by a slow consolidation curve.…”

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CFD Simulations of bubbling/collapsing fluidized beds for three Geldart Groups

2003

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IntrodutionThe collapsing fluidized-bed experiment, first described by Ž . Rietema 1967 , has been used to understand the dense-phase regime of fluidization, and is still commonly used today ŽGeldart et al., 1984;Grace, 1992;Barreto et al., 1988;Tianxiong et al., 1982;Yang et al., 1997; . Formisani et al., 2002, for example . This experiment consists of fluidizing a bed to the quasi-steady-state condition and then suddenly stopping the gas flow. Observations of the bed are made as the gas escapes and the particulate phase settles and consolidates. This technique gives general properties of the dense-phase regime, including the average void fraction and Ž . superficial gas velocity Weimer and Quarderer, 1984 . This technique has also been used to gain insight as to the effects of other variables such as high pressure andror high temper-Ž . ature Weimer and Quarderer, 1984;Lettieri, 1999 . ApplicaCorrespondence concerning this article should be addressed to R. W. Lyczkowski. tion of this technique is not limited to predicting the behavior of fluidized beds, but is also valuable in the understanding and design of the standpipes and hoppers.This investigation originated from an industry need to better understand the current computational fluid dynamics Ž . CFD hydrodynamics of fluidization capabilities. The collapsing fluidized-bed experiment is a small, well-defined experiment that involves many different hydrodynamic phenomena. The bed expansion, bubbling, sedimentation, and consolidation all play important roles in the collapsing fluidized-bed experiment. The capability of CFD to correctly model this experiment would increase the confidence of industrial users. The modeling of the collapsing fluidized-bed experiment can also serve to verify key particle characteristics and refine the hydrodynamic model before attempting to simulate more complex reacting systems. The following section gives an overview of the experiment.

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