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Research Papers

Investigation of the Coal Gasification Process Under Various Operating Conditions Inside a Two-Stage Entrained Flow Gasifier

[+] Author and Article Information
Armin Silaen

Energy Conversion & Conservation Center,  University of New Orleans, New Orleans, LA 70148-2220

Ting Wang1

Energy Conversion & Conservation Center,  University of New Orleans, New Orleans, LA 70148-2220twang@uno.edu

1

Corresponding author.

J. Thermal Sci. Eng. Appl 4(2), 021006 (Apr 20, 2012) (11 pages) doi:10.1115/1.4005603 History: Received July 13, 2011; Revised October 17, 2011; Published April 17, 2012; Online April 20, 2012

Numerical simulations of the coal gasification process inside a generic 2-stage entrained-flow gasifier fed with Indonesian coal at approximately 2000 metric ton/day are carried out. The 3D Navier–Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and two-step thermal cracking equation of volatiles. The chemical percolation devolatilization (CPD) model is used for the devolatilization process. This study is conducted to investigate the effects of different operation parameters on the gasification process including coal mixture (dry versus slurry), oxidant (oxygen-blown versus air-blown), and different coal distribution between two stages. In the two-stage coal-slurry feed operation, the dominant reactions are intense char combustion in the first stage and enhanced gasification reactions in the second stage. The gas temperature in the first stage for the dry-fed case is about 800 K higher than the slurry-fed case. This calls for attention of additional refractory maintenance in the dry-fed case. One-stage operation yields higher H2 , CO and CH4 combined than if a two-stage operation is used, but with a lower syngas heating value. The higher heating value (HHV) of syngas for the one-stage operation is 7.68 MJ/kg, compared with 8.24 MJ/kg for two-stage operation with 75%–25% fuel distribution and 9.03 MJ/kg for two-stage operation with 50%–50% fuel distribution. Carbon conversion efficiency of the air-blown case is 77.3%, which is much lower than that of the oxygen-blown case (99.4%). The syngas heating value for the air-blown case is 4.40 MJ/kg, which is almost half of the heating value of the oxygen-blown case (8.24 MJ/kg).

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 6

Gas temperature and species mole fraction distributions for case 2 (2-stage, 75%–25%, dry coal, oxygen-blown)

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Figure 7

Mass-weighted averages of gas temperature and species mole fraction distributions along gasifier height for case 2 (2-stage, 75%–25%, dry coal, oxygen-blown)

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Figure 8

Mass-weighted averages of gas temperature and species mole fraction distributions along gasifier height for cases 1, 3, and 4

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Figure 9

Velocity vectors and temperature field on the center vertical plane and injection planes for case 3 (50%–50%)

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Figure 10

Mass-weighted averages of gas temperature and species mole fraction distributions along gasifier height for case 5 (2-stage, 75%–25%, coal slurry, air-blown)

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Figure 1

Schematic and inlet and boundary conditions for the two-stage entrained-flow gasifier

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Figure 2

Gas temperature and species mole fraction distributions for case 1 (2-stage, 75%–25%, coal slurry, oxygen-blown)

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Figure 3

Mass-weighted averages of gas temperature and species mole fraction distributions along gasifier height for case 1 (2-stage, 75%–25%, coal slurry, oxygen-blown)

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Figure 4

(a) Flow pathline colored by the residence time temperature and (b) particle distribution for case 1

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Figure 5

Velocity vectors and temperature field on the center vertical plane and injection planes for case 1

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