COMBUSTION OF SINGLE ISOLATED CARBON PARTICLE IN A STAGNANT ENVIRONMENT

Abstract

The combustion behaviour of a spherical carbon particle in a hot oxidizing stagnant environment has been investigated in this study. The environment is considered to contain 02, CO2, CO, and the inert N2. The carbon particle is assumed to be of constant density and at uniform temperature. Both radial convective and radial diffusive transport of oxidizer and the products of combustion have been considered. Heterogeneous reactions C + JO2 = CO and C + CO2 = 2C0 have been considered to occur at the surface of the particle while the homogeneous reaction CO + JO2 = CO2 has•been considered to occur in the gas phase. The two limiting cases of a frozen and chemical equilibrium of homogeneous reaction have been considered. . In the present study the results of Libby & Blake [8] for mass loss rate of solid carbon particle have been reproduced. Klaus loss rate of carbon has been determined for various values of surface temperature corresponding to different ambient oxygen concentrations and prp (pressure x radius of the particle) values. It is found that with the increase of particle temperature, the mass loss rate increases. This increase continues till the diffusion limit is reached when the mass loss becomes constant for further increase in temperature. With the increase of ambient oxygen concentration, the mass loss rate increases. The temperature to achieve the same mass loss rate decreases with the increase of prp values. (iv) The analysis has been extended as suggestedrby Libby & Blake [8] to a porous carbon particle. The numeric'al results have been presented for mass loss rate from a porous carbon particle for various values of surface temperature corresponding to different values of porosity, core radius, ambient oxygen concentration and prp values. The mass loss rate increases with increase in the porosity and decreases with decreasing the core radius of the porous particle. It is estimated that the rate of mass loss is about twice in the case of porous carbon particle for 50 per cent porosity than that of a solid carbon particle.