Stages of thermal transformation of oil shales organic-mineral substance of the Middle Volga region during combustion

Abstract

© Published under licence by IOP Publishing Ltd. The study of the staging of the thermal conversion of oil shale, common in the Middle Volga region, was carried out. It is established that the organic matter of rocks due to the polycomponent composition undergoes multi-stage pyrolysis in the temperature range 200-600°C. The most favorable temperature of pyrolysis, when up to 80% of the potential heat of shale is released, falls within the interval of 460-480°C. The main thermal transformations of the ash component are carried out at temperatures above 480°C. They are due to the release from the structure of clay minerals of the OH group, the oxidation of pyrite, the decomposition of calcite and the formation of spinels. Summing up the obtained results, we can draw to the following conclusions: 1. Oil shale of the Middle Volga region is characterized by significant variations in the content of organic matter from 9 to 40%. The light isotopes C12 predominance in the composition of organic carbon indicates the predominantly biochemical origin of the organic matter. 2. The configuration of the DSC curve in the temperature range of 200-600°C indicates both the multicomponent composition of the organic compounds of oil shale and their multi-stage pyrolysis. 3. The most favorable pyrolysis temperature, when up to 80% of the potential heat of shale is released, is in the range of 460-480°C. 4. In the process of burning oil shale, the ash component of the rock also subjected to thermal transformation. The composition of rock-forming minerals determined the main temperature ranges of transformation in the areas of 480-600°C (extraction of hydroxyl water from clays, oxidation of pyrite with the formation of hematite), 680-800°C (destruction of calcite), 880-900°C (formation of spinels).