Chernenko O. Thermophysical and chemical processes’ regularities of hysteresis type in aerodisperse systems

Analytical models of heat- and mass transfer's hysteresis and combustion kinetics of gas impurities were constructed. Only one unilateral and two parallel first-order reactions were accepted. Analytical description of the area's hysteresis of heat- and mass transfer for catalyst's particles (darts) has no analogues and is based on the proposed and developed method of using partial derivatives and parametric dependences to find critical conditions. Inside the hysteresis area, catalytic ignition is observed, and outside – stationary catalytic oxidation and combustion states of gas's impurities in the air. The critical parameters of catalytic self-ignition and extinction gases, conditions them degeneracy were found taking into account thermal diffusion and heat loss by radiation. Heat loss by radiation leads to the occurrence of an additional hysteresis loop at large diameters and its degeneration with a decrease in the combustible gas's concentration and an increase in the gas mixture's temperature . The value of the diffusion-kinetic ratio at the hysteresis loop degeneracy is close to unity. The dependence of the critical value of hydrogen concentration and catalytic ignition temperature, above which the self-sustaining catalytic combustion of a cold gas-air mixture takes place, on the diameter of a platinum dart with a switched off DC source is described. The temperature dependence of the heat release rate in impurities’ ammonia catalytic combustion reactions on a platinum wire has a maximum. It is explained by the competition of reactions with formation N2 and NO taking into account mass transfer. Determined carbon particle diameter’s areas, which force ignite and burn in nitrogen-oxygen mixtures at room temperature (oxygen concentrations above a certain limit value). Heat loss by radiation, the oxygen concentration and the particle's porosity significantly affect on the this area's size. For the first time, the characteristics of large porous coal particle’s forced ignition of in cold nitrogen-oxygen mixtures were experimentally investigated and analytically substantiated. It is shown that the change's rate of the product of porous coal particle's density and the square of diameter in the process its combustion is constant and doesn't depend on the initial its diameter. A modified combustion constant of the porous particle is introduced, which takes into account the response within the pores. The empirical dependence of the particle's burning time on the initial values its diameter and density, oxidant concentration and gas mixture's temperature is theoretically substantiated. Analysis of particle combustion at low oxygen concentrations (reaction in the pores is significant) allows to evaluate the effective characteristics of coal porosity. A analytical method delay time determination at gas’s impurities catalytic forced ignition was proposed. The method is based on the preliminary finding of the critical forced ignition temperature. A new analytical method delay time determination at coal particle ignition was pro-posed. It is based on the introduction dimensionless temperature relative to the ignition temperature. It allows to take into account the course of parallel chemical reactions and mass transfer (in the transient and diffusion combustion's modes). The combustion of a pulverized coal in the tuyere area of the blast furnace and in flame gunning technology of oxygen converter was considered.