The dissertation is devoted to the study of heat and mass transfer processes in dense dispersed layers using the energy of the microwave field. On the basis of scientific works, in which the results of theoretical and practical studies of the effects of the interaction of the microwave field with dielectric materials, methods of research and development of energy-efficient heat treatment technologies are presented, an analysis of innovative directions for the use of microwave heating in modern technologies of heat treatment of dispersed materials is carried out. Processes based on MX heating of materials characterized by sufficiently high dielectric coefficients or containing substances with properties of polar molecules or ionic conductivity have a great potential for energy efficiency. Microwave energy has proven itself as a factor in the intensification of heat and mass transfer, however, in order to obtain investments and implement microwave heating technology, full-scale studies of transfer processes and determination of ways to overcome difficulties associated with scaling up laboratory installations to industrial capacities and obtaining recommendations on the technological process are required.
In the work, mathematical modeling of the non-stationary process of heat conduction in the material layer under the conditions of action of internal energy sources, which is a microwave electromagnetic field, is carried out. The obtained dependence allows you to calculate the temperature for three periods of drying of the zeolite layer: zero (heating period), first (period of constant drying rate) and second (period of decreasing drying rate). During the processing of experimental data, the regularities of changes in average integral moisture contents and temperatures, drying speed, and energy consumption per 1 kg of evaporated moisture were determined. The calculation of the heating temperature of the layer of various types of zeolites (NaX, NaA1, NaA2, EST-10, clinoptilolite) under the conditions of the microwave field proved that NaX is characterized by a maximum heating rate of 0.35 K/s, and the heating rate of clinoptilolite was 0.03 K /s.
Experimental studies of the drying process of type 4A and 13X zeolites were carried out, with the aim of establishing which method of energy supply (microwave, microwave cyclic, microwave-convective, convective) and which mode characteristics ensure high intensity with minimal energy consumption.
Comparison of thermal characteristics of drying, such as specific energy consumption per kilogram of moisture removed, drying speed allowed to determine the optimal mode: simultaneous MX-convective energy supply method, which achieves the maximum drying speed of N=2.97•10-4 kg/(kg•c) and specific energy consumption Qpyt=4,87 MJ/kg. . The analysis of the change in the efficiency of the working chamber depending on the processing time, the mass of the samples and the type of zeolite was carried out. The next series of studies was aimed at evaluating the effectiveness of soil heating when using microwave technology. Two types of soil were chosen for research: clay soil ρ=1360 kg/m3 and black earth soil ρ=1150 kg/m3 with the same initial moisture content (20%), which was formed by adding water calculated from the amount of the equilibrium volume. On the basis of experimental data, an assessment of the energy efficiency of microwave heating of the soil was carried out, taking into account the part of microwave energy that turned into thermal energy , which consists of the share for heating the material itself and evaporation of moisture , as well as the loss to the environment due to radiant , convective heat exchange and the loss for heating the dielectric cell It was found that the efficiency of the microwave chamber when loading a layer of soil with a thickness of 0.02 m and a mass of 0.4 kg is 82%, but the overall efficiency, taking into account the efficiency of the magnetron, is η=0.63%. The electric field strength in the layer of soil material was determined by the theoretical-experimental method for the conditions of the optimal processing efficiency: E=33908 V/m, for the purpose of scaling and moving from experimental data, it is advisable to focus on the obtained value of the electric field strength. The results of the work on increasing the energy efficiency of microwave heating were implemented at the company LLC "Zont" (a factory of science-intensive technologies) to carry out design calculations of a microwave chamber of the resonance type with the aim of further designing a microwave plant for industrial purposes.
