Fluid Dynamic of Pressurized Coal Gasifiers.

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Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we have conducted a study of the fluid dynamics of ... continued below

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33 p.; Other: FDE: PDF; PL:

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Louge, M.T. November 1, 1997.

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Description

Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we have conducted a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea was to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employed a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, experiments employing plastic and glass powders fluidized with mixtures of sulfur hexafluoride, carbon dioxide, helium and air at ambient temperature and pressure achieved hydrodynamic similarity with generic high-temperature risers of variable scale operating at 1 and 8 atm. We interpreted our results in the upper riser using steady, fully developed momentum balances for the gas and solid phases. This analysis showed that, for a wide range of experiments, two parameters capture the dependence of the pressure gradients upon the ratio of the mean gas and solid mass flow rates. The first is the ratio of the mean particle slip and superficial gas velocities. The second represents spatial correlations between the radial profiles of interstitial gas velocity and voidage. Variations of the first with dimensionless parameters indicated that our `atmospheric` and `pressurized` experiments conformed to distinct viscous and inertial regimes. In this study, we established also that the descending velocity of particles clusters at the wall of a riser scales exclusively with the square root of the particle diameter and the gravitational acceleration. This observation showed that the dynamics of wall clusters is chiefly determined by inter-particle contacts. Because these clusters govern heat transfer at the wall, this conclusion has important consequences for modeling. These activities were conducted with Air Products & Chemicals, Inc., which was a member of a consortium that included Foster Wheeler and Deutsche Babcock Energie-und Umwelttechnik AG. At the completion of this work, the results have exceeded the expectations outlined in the original proposal. The present report summarizes these accomplishments, which have led to four publications, 13 presentations, several quarterly reports, and the support of three graduate students.

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33 p.; Other: FDE: PDF; PL:

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OSTI as DE98051812

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  • Other Information: PBD: Nov 1997

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  • Other: DE98051812
  • Report No.: DOE/PC/93216--T14
  • Grant Number: FG22-93PC93216
  • DOI: 10.2172/643546 | External Link
  • Office of Scientific & Technical Information Report Number: 643546
  • Archival Resource Key: ark:/67531/metadc696266

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  • November 1, 1997

Added to The UNT Digital Library

  • Aug. 14, 2015, 8:43 a.m.

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  • Nov. 10, 2015, 8:57 p.m.

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Louge, M.T. Fluid Dynamic of Pressurized Coal Gasifiers., report, November 1, 1997; United States. (digital.library.unt.edu/ark:/67531/metadc696266/: accessed September 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.