Choice of the Kinetic Scheme of Oxidation Reactions of the Gaseous Products of Coal Pyrolysis during Induction Period at Ignition of the Water–Coal Fuel Particles

Abstract

A theoretical analysis of the conditions and ignition of a drop of water−carbon fuel has been carried out. A mathematical model of the ignition process has been developed, which is characterized by well-known descriptions of the processes of interaction of gaseous combustible (volatile) and oxidative (air) components near the surface of the drop (and after the particle drying). The analysis of the influence of the kinetic scheme of the process of thermochemical reaction and oxidation on the main characteristics of the ignition of drops of water−carbon fuel (ignition delay timet ign ) has been carried out. The comparison of the experimental and theoretical values has shown their good correspondence. The experiments have been carried out on the facility that provides the conditions adequate to the characteristic zones of the steam and hot water boilers. According to the results of mathematical modeling, the prognostic potential of two significantly different kinetic models of oxidation of the main gaseous combustible components of pyrolysis products (carbon monoxide CO, hydrogen H 2 , and methane CH 4 ) has been analyzed. It has been established that the one-stage model of volatile ignition describes the ignition process quite well in the induction period. The deviations in the ignition delay times obtained in the framework of two different kinetic models do not exceed 5% over the entire range of variations in the heating conditions possible in practice. The results of numerical simulation show that taking into account the multistage nature of gas-phase ignition reactions of water−coal fuel particles (oxidation of hydrogen, methane, and carbon monoxide with air oxygen) does not lead to significant (in the practice of fuel combustion processes) changes in ignition delay times.