Ignition and Combustion of Large Coal Particles in Cold Nitrogen–Oxygen Mixtures

Forced ignition and subsequent combustion of large coal particles in a cold air and oxygen are investigated experimentally. The critical value of the initial temperature (ignition temperature) of a particle of charcoal and of anthracite is estimated. On preliminary heating of the particle above the ignition temperature, a quasi-stationary mode of combustion is attained after a certain interval of time. For a charcoal particle, depending on the initial density of the particle, either a substantial change in its density or its invariability in the process of combustion in a cold air flow is observed. A relation is suggested allowing one to estimate the critical temperatures of ignition in cold gaseous mixtures depending on oxygen concentration and particle diameter. The absence of ignition of a large anthracite particle in air at room temperature is attributed to the larger value of the activation energy there than in the charcoal particle.