Experimental studies of single particle coal combustion: Ignition, sulfur retention, and the contributions of morphology
Bayless, David James
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/19001
Description
Title
Experimental studies of single particle coal combustion: Ignition, sulfur retention, and the contributions of morphology
Author(s)
Bayless, David James
Issue Date
1995
Doctoral Committee Chair(s)
Buckius, Richard O.
Peters, James E.
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical engineering
Energy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemical engineering
Mechanical engineering
Energy
Language
eng
Abstract
Single particle pulverized coal combustion experiments were conducted in a drop tube furnace facility in order to investigate various aspects of coal combustion. Included in the study were the effects of natural gas cofiring on particle ignition and sulfur capture in ash, and the effects of morphology on burning rates at diffusion-limited conditions.
Measurements of particle ignition delay indicated that cofiring 1% methane by volume reduced the ignition delay of low-volatile coal particles to the value of the ignition delay of high-volatile particles of the same size in air alone. Ignition delays were accurately predicted using two separate models--one based on energy absorption and the other on devolatilization.
Cofiring coal with natural gas was shown to increase sulfur retention in ash. This increase, known as leveraging, was affected by particle residence time and furnace temperature, while original sulfur form and coal sorbent capacity had little effect. Experimental results indicated that the primary mechanism for sulfur leveraging was the gas phase conversion of SO$\sb2$ to SO$\sb3$. These results were supported by numerical modeling of particle combustion and sulfur evolution.
A technique was developed to more accurately quantify particle burning area by including the effects of voids (pores on the particle surface that are deeper than their surface radius). Scanning electron microscopy and digital processing of images of quenched particles were used to quantify surface void area, perimeter, and reacting void wall area for voids with diameters larger than 1 $\mu$m. Burning rates determined from in situ measurements of a wide range of reacting coal particles indicated that calculated burning rates more closely matched diffusion-limited burning rates when burning area was corrected for void surface area and reacting void wall area.
Results of quantifying void area distributions indicated that mean void area increased with coal volatility, heating rate, and heterogeneous combustion, but was not significantly affected by oxygen concentration. Numerical results indicated that burning rate calculations did not strongly depend on specific void distribution shape. However, results suggested that errors in burning rate caused by assuming a void distribution were minimized by using a pore distribution model modified for the effects of void combination and assuming a mean void area of 20%.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
