High-speed camera observation of a bituminous coal combustion in air and O2/CO2 mixtures and particle velocity measurement

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Abstract

An advanced high-speed camera with a spatial resolution of ~20 μm and time scale of 1~2 ms was employed to observe coal particle combustion in a lab-scale drop-tube furnace. Combustion of a bituminous coal of 106~153 μm at the furnace temperature of 1000°C in air and O2/CO2 mixtures was photographed. Apart from the transient phenomena captured in each stage, dynamic information regarding burning coal particle velocity and its residence time was also obtained through analysis of multiple exposures. Combustion of coal char (attained from pyrolysis in N2) was also recorded. The results indicate the obvious variation of particle motion with reactor height and gas atmosphere. Volatiles released at the initial stage of coal combustion could be dominated by the heavy tarry hydrocarbons that preferentially combusted in the vicinity of particles, which in turn yielded a large buoyant force around particles and greatly reduced their falling velocities. Such a phenomenon was not observed during char combustion. The consumption/combustion rate of the released volatiles from bituminous coal further played an important role in char particle motion in the late stages. Replacement of air with 21% O2 + 79% CO2 increased the duration of volatile consumption on char surface, thus slowing particle motion over a relatively long period. Increasing the O2 fraction in CO 2 fastened the volatile consumption rate. Particle velocity was improved consequently. These findings were not predicted by a conventional non-reacting particle motion model, bearing significance for understanding the kinetics of pulverized coal combustion as well as retrofitting of existing power generation plants with an oxy-fuel combustion technology that burns coal in O2/CO2 mixture.

Original languageEnglish
Title of host publication26th Annual International Pittsburgh Coal Conference 2009, PCC 2009
Pages659-669
Number of pages11
Volume1
Publication statusPublished - 2009
Event26th Annual International Pittsburgh Coal Conference 2009 - Pittsburgh, United States of America
Duration: 20 Sep 200923 Sep 2009
Conference number: 26

Conference

Conference26th Annual International Pittsburgh Coal Conference 2009
CountryUnited States of America
CityPittsburgh
Period20/09/0923/09/09

Keywords

  • Buoyant force
  • High-speed camera
  • In-situ diagnostics
  • Oxy-fuel combustion
  • Volatiles cloud

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