Effect of the pressure of a gas mixture on the ignition, combustion, and spontaneous extinction of cokes of coals of different polymorphisms

The dependence of the diameter of a porous carbon particle on stationary temperature at various pressures of the gas mixture is analyzed. Cases of self-ignition of a particle in a heated nitrogen-oxygen mixture and forced ignition in a cold nitrogen-oxygen mixture leading 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 that qualitatively describes this dynamics is obtained. The greatest growth falls on a pressure interval of 0.1–0.3 MPa. A similar analysis for particles of various coals is presented. The dependence of the critical oxygen concentrations corresponding to ignition and extinction on the diameter of a carbon particle was obtained analytically taking into account the internal reaction. It is shown that an increase in the pressure in the mixture leads to a decrease in the critical concentrations of oxygen.