Measurement of combustion kinetics of a single char particle in an electrodynamic thermogravimetric analyzer

Ezra Bar-Ziv, Daniel B. Jones, R. Erik Spjut, David R. Dudek, Adel F. Sarofim, John P. Longwell

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

A new device for studying single-aerosol-particle kinetics at elevated temperatures, particularly designed for studying kinetics of gas-solid or gas-liquid combustion, is presented. The device is referred to as the electrodynamic thermogravimetric analyzer (EDTGA). An electrically charged particle is levitated by means of electrical forces. Particles of diameters of 1-250 μm can be levitated in this device. The EDTGA consists of an electrodynamic chamber with a quadrupole-type two-dimensional cross section, a heating system based on a cw CO2 laser, a temperature measurement system applying two- and three-color infrared or visible pyrometry, and a position-control system that automatically adjusts the DC voltage required to maintain the particle centered in the chamber. The EDTGA is capable of continuous or pulsed heating of the particle to temperatures exceeding 3000 K, continuous measurement of the temperature of the particle, and continuous weighing or sizing of the particle. Heating rates can exceed 106 K s-1. The time resolution of the measurement is 0.1 ms. Two weighing methods are presented in this paper: techniques based on electron loss, and methods based on the drag force. It is shown that heating by infrared radiation causes only a minor inhomogeneity in the internal temperature field of the irradiated particle. The maximum internal temperature difference is only a few degrees in particles with temperatures exceeding 1500 K. The kinetics of oxidation of synthetic char-Spherocarb particles, in the diameter range 140-200 μm, were studied in this device. The particle's diameter, density, CO2 surface area, and temperature were measured. A shrinkage effect of char was observed. Rates of heat loss and heat release were determined. The ignition temperature of a Spherocarb particle in the 150-μm diameter range, in pure oxygen, was observed to be 1500 K. No ignition was observed in air. It was found that at particle temperatures exceeding 1500 K the particle lost most of its charge. Thus it could not be levitated by electrical force. The use of the EDTGA at temperatures above 1500 K is discussed.

Original languageEnglish
Pages (from-to)81-106
Number of pages26
JournalCombustion and Flame
Volume75
Issue number1
DOIs
StatePublished - 1 Jan 1989
Externally publishedYes

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy

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