Effect of Gas Mixture Pressure on the Ignition, Combustion, and Spontaneous Extinction of Chars of Coals of Different Polymorphisms

Abstract

The dependence of the diameter of a porous carbon particle on stationary temperature at various gas mixture pressures is analyzed. The cases of particle self-ignition in a heated nitrogen–oxygen mixture and forced ignition in a cold nitrogen–oxygen mixture that lead to quasi-stationary combustion, followed by spontaneous extinction, are considered. It is shown that the combustion temperature of small particles with a diameter $$d<200$$ $$\mu$$ m, which are characterized by a transient regime of chemical reactions, increases with increasing pressure of the gas mixture. An analytical dependence qualitatively describing this dynamics is obtained. The greatest increase is observed in the pressure range 0.1–0.3 MPa. A similar analysis is performed for particles of various coals. The dependence of the critical oxygen concentrations corresponding to ignition and extinction on carbon particle diameter was obtained analytically taking into account the internal reaction. It is shown that increasing the mixture pressure leads to a decrease in the critical oxygen concentrations.