A convenient apparatus for dispersing uniform clouds of solid particles for laboratory dust flame experiments has been tested. The combustion characteristics of premixed laminar graphite-oxygen-nitrogen flames have been studied at atmospheric pressure both with and without added hydrocarbon. The variation of particle burning time with initial oxygen partial pressure and oxygen/ fuel ratio has been described by first-order combustion kinetics with due consideration for oxygen depletion during burn-out. Flame velocity measurements indicate very slow propagation compared with hydrocarbon sprays and aluminum clouds of similar particle diameter. Added chlorine did not measurably affect graphite combustion up to concentrations of 2.5 vol. in the presence of added hydrocarbon, but less than 1.0 vol. of chlorine extinguished pure graphite-oxygen flames. The addition of 1.5 to 4.75 wt. of lead acetate visibly stabilized the graphite-oxygen flame, but the effect on the flame velocity and burning rate could not be measured.
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