Changes in thermophysical and thermotechnical characteristics of flour-milling waste in the process of slow pyrolysis

In the process of biomass pyrolysis, its composition and structure changes significantly that results in changing the thermophysical characteristics of the carbon residue. Information about the elemental composition of raw materials and their characteristics in the process of thermal processing is necessary for optimizing technological parameters and understanding the flowing processes. The work purpose is to determine the thermophysical characteristics of flour-milling wastes during slow pyrolysis process. The thermophysical characteristics were determined by the flash laser method. In the course of the study, such methods as an experiment, differential thermal analysis and scanning electron microscopy were used. It has been established that carbon residues obtained at temperatures not exceeding 300 ⁰С have a higher heat capacity than the original bran. A further increase in temperature leads to a sharp decrease in heat capacity, which is due to the decomposition of some fundamental components (hemicellulose, cellulose, lignin). The thermal conductivity of carbon residues (0.146-0.173 W/(m·K)) enhances with an increase in their production temperature. The values of the thermophysical characteristics for the initial bran and solid pyrolysis products were established that can be used to assess their effective values in relation to any fraction of wheat bran after determining the bulk density.