Comparative analysis of conventional and microwave pyrolysis of raw materials with different degree of metamorphism

Abstract

The growth in anthropogenic impact on the environment caused mainly by energy activities and combustion of traditional fossil hydrocarbon sources necessitates the search for alternative energy generation technologies. Thermal processing of organic raw materials allows obtaining energy valuable products with less environmental impact. However, it strongly depends on the mechanism of thermal effect on the raw material and its characteristics. This paper compares two types of pyrolysis, including conventional one with heating of the entire reactor volume and microwave one with local impact of electromagnetic waves on the sample, for fuels with different degree of metamorphism. Comparative experiments indicate that the yield of high-calorie carbonaceous residue rises with an increase in geological age of fuels for both pyrolysis types, while the amount of solid products for conventional pyrolysis is 1.2–2.6 times higher than for microwave one. In its turn, regardless of the degree of metamorphism, microwave pyrolysis demonstrates advantages from the position of obtaining high-calorie gaseous products (from 18.6 to 28.0 MJ/m3) with low CO2 component ballast (<10 %). Such fundamental differences are due to the nature and speed of ongoing thermal reactions. The presented results can serve as a basis for choosing the method of processing of organic raw materials depending on the intended purpose of the final products.