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Title: Influence of phase transformations and heat and mass exchange on the course of the processes of pyrolysis of single high-ash-coal particles at elevated pressures

Abstract

A comparative analysis of equilibrium and nonequilibrium models for calculation of the rates of phase transitions (evaporation and condensation) of pyrolysis products and the influence of convective heat and mass exchange with inert ash particles and the gas flow in pyrolysis of single particles of high-ash bituminous coals in the operation of technological units with a circulating fluidized bed under pressure is made.

Authors:
 [1]
  1. National Academy of Sciences and Ministry of Fuel and Power of Ukraine, Kiev (Ukraine). Institute of Coal Power Technologies
Publication Date:
OSTI Identifier:
21240333
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Engineering Physics and Thermophysics (English Translation of Inzhenerno-Fizicheskii Zhurnal); Journal Volume: 80; Journal Issue: 2; Other Information: TN: Translation of Inzhenerno-Fizicheski Zhurnal; 80(1); 127-138 (Mar-Apr 2007); Related Information: Translation of Inzhenerno-Fizicheski Zhurnal; 80(1); 127-138 (Mar-Apr 2007)
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; ASHES; BITUMINOUS COAL; PHASE TRANSFORMATIONS; PYROLYSIS; GAS FLOW; ASH CONTENT; FLUIDIZED BEDS; CIRCULATING SYSTEMS; PYROLYSIS PRODUCTS; PRESSURIZATION; CALCULATION METHODS; HEAT TRANSFER; MASS TRANSFER; EQUILIBRIUM; MATHEMATICAL MODELS; EVAPORATION; VAPOR CONDENSATION

Citation Formats

V.P. Patskov. Influence of phase transformations and heat and mass exchange on the course of the processes of pyrolysis of single high-ash-coal particles at elevated pressures. United States: N. p., 2007. Web. doi:10.1007/s10891-007-0045-5.
V.P. Patskov. Influence of phase transformations and heat and mass exchange on the course of the processes of pyrolysis of single high-ash-coal particles at elevated pressures. United States. doi:10.1007/s10891-007-0045-5.
V.P. Patskov. Thu . "Influence of phase transformations and heat and mass exchange on the course of the processes of pyrolysis of single high-ash-coal particles at elevated pressures". United States. doi:10.1007/s10891-007-0045-5.
@article{osti_21240333,
title = {Influence of phase transformations and heat and mass exchange on the course of the processes of pyrolysis of single high-ash-coal particles at elevated pressures},
author = {V.P. Patskov},
abstractNote = {A comparative analysis of equilibrium and nonequilibrium models for calculation of the rates of phase transitions (evaporation and condensation) of pyrolysis products and the influence of convective heat and mass exchange with inert ash particles and the gas flow in pyrolysis of single particles of high-ash bituminous coals in the operation of technological units with a circulating fluidized bed under pressure is made.},
doi = {10.1007/s10891-007-0045-5},
journal = {Journal of Engineering Physics and Thermophysics (English Translation of Inzhenerno-Fizicheskii Zhurnal)},
number = 2,
volume = 80,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • A two-dimensional stationary model of motion, heat and mass exchange, and chemical reaction of polydisperse coke and ash particles in ascending gas-suspension flow has been constructed with allowance for the turbulent and pseudo turbulent mechanisms of transfer in the dispersed phase. The system of equations that describes motion and heat transfer in the solid phase has been closed at the level of the equations for the second moments of velocity and temperature pulsations, whereas the momentum equations of the carrying medium have been closed using the equation for turbulent gas energy, which allows for the influence of the particles andmore » heterogeneous reactions.« less
  • Investigation of liquid-phase hydrogenation of acetylene at approx. 20 atm in laboratory apparatus and in pilot unit in the presence of suspended palladium catalyst showed that no losses of ethylene or propylene occur in the process. The amount of catalyst required for liquid-phase hydrogenation in the presence of the suspended catalyst is smaller by a factor of 20-25 than the amount required for the gas-phase process.
  • For pyrolysis of n-tetradecane at 450 C under elevated pressures (about 2--9 MPa) for 6--480 min, the major products in the early stage are n-alkanes in the carbon number range of C[sub 1]-C[sub 11] and 1-alkenes in the carbon number range of C[sub 2]-C[sub 14]. Formation of the olefinic product with 13 carbon atoms is very limited, but 1-C[sub 12]H[sub 24] is as abundant as the 1-alkenes in the range of C[sub 2]-C[sub 11]. As compared to the well-known gas-phase pyrolysis, the molar ratios of alkenes to alkanes are much smaller ([le]1), except the ratio for the group with 12more » carbon atoms where the 1-C[sub 12]H[sub 24]/n-C[sub 12]H[sub 26] ratio can be as high as 9 in the early stage. This is because 1-C[sub 12]H[sub 24] is produced from [beta]-scission of a secondary 4-C[sub 14]H[sub 29] radical, whereas n-C[sub 12]H[sub 26] is formed from a primary 1-C[sub 14]H[sub 29] radical, whose population is much less than the secondary radical due to both higher activation energy and the competing isomerization reaction. There appeared a preferential formation of 1-C[sub 6]H[sub 12] and 1-C[sub 5]H[sub 10] among the 1-alkenes formed after 12 min. This may be attributed to the 1,5-shift and 1,4-shift isomerization of primary radicals formed during tetradecane pyrolysis. The peak of carbon number distribution shifts toward 2 for paraffinic products and toward 3 for olefinic products, and the ratios of alkenes to alkanes decrease with increasing residence time up to 60 min. The general reaction mechanism is characterized by the one-step decomposition of secondary radicals and the 1,5 and 1,4-shift isomerization of primary radicals to secondary radicals. The substrate alkane molecules are the source for hydrogen abstraction in the early stage, but in the later stages the olefinic products also undergo the H-abstraction reactions, which lead to the formation of cyclic alkenes/alkanes and alkylaromatics.« less
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