Effect of the yield of liquid products on microwave pyrolysis duration

Relevance. The need to improve the efficiency of energy use of fossil fuels and renewable biomass resources through their thermal upgrading. Aim. To establish the relationship between the yield of liquid products of microwave pyrolysis of organic raw materials with different degrees of metamorphism and the process duration. Methods. Certified SS methods for determining the thermal characteristics and elemental composition of the organic and mineral parts of organic raw materials, the “transmission–reflection” method for measuring the imaginary (ε'') and real (ε') components of the complex dielectric constant, physical experiment, gas analysis, high-speed video filming. Results. Based on the analysis of the material balance and duration of the microwave pyrolysis of various types of organic raw materials, the authors have supposed that the destruction of complex organic compounds leads to the formation of carbon new formation on the surface of the sample. This formation has high electrically conductive properties relative to the original raw materials. In the presence of a large number of such new formations in the microwave field, interparticle electrical discharges can occur, spreading along the sample, resulting in an increase in the heating rate. For raw materials with a higher yield of liquid products, the number of carbon new formations also increases. This leads to an increase in the number of discharges between such centers and a proportionate acceleration of material heating. It was experimentally shown and theoretically substantiated that the duration of the microwave pyrolysis of organic raw materials directly depends on material heating rate: due to an increase in the yield of liquid products and a subsequent increase in the concentration of carbon centers, the duration of the microwave pyrolysis process decreases. The results obtained can be used to evaluate the efficiency of microwave pyrolysis of organic raw materials or fuel compositions consisting of materials with different yields of liquid products.