The influence of long-term storage on thermal behaviour of lower rank coal on the example of Polish coal. Part 1. The influence of long-term storage (LTS) of a lower rank coal on changes in volume of carbonized charge and changes in structural chemical pa

•LTS reduces thermal diffusivity of carbonized charge of lower rank coal.•LTS doubles growth in charge volume at the stage of grain swelling.•LTS increases contribution of unsaturated hydrocarbons in volatile matter.•LTS increases contribution of CO2 in volatile matter emitted during re-solidification.

The pyrolysis process of a lower rank coal as a fresh coal (FC) and a long-term stored coal (LTSC) was analyzed in a laboratory coking unit using X-raying and thermobalance. The changes in temperature of the charge of coals were determined along with the changes in volume of their carbonized charges, the mass loss of coals, and the mass loss rate. It was stated that LTSC has a lower thermal diffusivity at the stage of coal grain swelling and shows an almost twofold growth in charge volume at this stage. The samples of carbonized coals that correspond to the plasticity stage were investigated using the FT-IR and SEM methods. The pyrolysis products of coals were analyzed by the TG/FT-IR method. It is suggested that the formation of nano-size films and spherical objects in the pores of the plastic mass of LTSC results from an increase in content of non-saturated hydrocarbons, aldehydes, phenols, and alcohols in volatile products of pyrolysis of this coal.

Graphical abstractDownload high-res image (96KB)Download full-size image