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Research Papers

Simulation of Char Dust Combustion Inside a Pyroscrubber Downstream of a Petroleum Coke Calcining Kiln

[+] Author and Article Information
Zhao Lei

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

Wang Ting1

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

1

Corresponding author.

J. Thermal Sci. Eng. Appl 4(1), 011010 (Mar 19, 2012) (9 pages) doi:10.1115/1.4005287 History: Received April 22, 2011; Revised August 25, 2011; Published March 09, 2012; Online March 19, 2012

A pyroscrubber is a furnace used in the petroleum coke calcining industry to recover energy from the carbonaceous contents, including char dust and hydrocarbon volatiles of the exhaust gas from the calcination kiln. The combusted hot gases are used to generate steam and produce electricity, so it is important to optimize the pyroscrubber performance to produce high-grade combusted gases to generate steam but with minimal emissions. A previous study employed the locally-homogeneous flow (LHF) model to study the means to improve combustion efficiency and reduce emissions. In the LHF model, the interphase exchange rates of mass, momentum and energy are assumed to be infinitely fast, so the dispersed phase (char dust) can be simplified as the gas phase, and the complex two-phase flow is then treated as a single-phase flow. In this study, LHF model is replaced with a solid particle combustion model by incorporating both finite-rate heterogeneous and homogeneous combustion processes. Results reveal that the particle combustion model generates much higher local flame temperature (2200 K) than in LHF model (1800 K). All char particles are burned before or in the high-bay area. Total energy output of the case with particle combustion model is 92% of the LHF model. Furthermore, motivated by the potential energy saving from removing the air blower power supply, this study further investigates the possible benefit of running the pyroscrubber with the ventilation doors open. Three cases with different combinations of air injections and door opening have been studied. Results show that the gas flow is stably stratified with a large amount of the entrained cold air moving at the bottom of the chamber and the hot combusted gas moving through the top. With the bottom doors completely open, sufficient air can be drawn into the pyroscrubber without the need of blowing air in, but the combustion gases will be overcooled making this practice unfavorable from the energy saving point of view.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the calcining process for petroleum coke

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Figure 2

A 3-D view of the pyroscrubber

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Figure 3

Detailed air injections and burners

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Figure 4

Temperature contour inside the pyroscrubber on different planes for coke particle combustion with 100% stoichiometric air

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Figure 5

Temperature contours inside the pyroscrubber at different planes for the LHF model case (100% stoichiometric air) from Zhao and Wang [4]

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Figure 6

Particle pathlines for coke particle combustion (100% stoichiometric air) showing particles are almost completely consumed in the high-bay area

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Figure 7

Species and temperature contour plots on X-direction planes for coke particle combustion case (100% stoichiometric air)

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Figure 8

Wall temperature contours in the pyroscrubber for three bottom doors opening case (cases 1–3)

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