A TG–FTIR investigation to the co-pyrolysis of oil shale with coal

•Co-pyrolysis of oil shale, bitumite and lignite was experimentally assessed.•Synergic effect existed in the blends of low caloric value fuels, oil shale with lignite.•Organic and mineralogical compositions was quantitative analyzed.•Mixed fossil fuels could accelerate the aromatization of the evolved gas.

Thermal characteristics and gas compositions during co-pyrolysis of oil shale with two types of coal, bitumite and lignite, at various blend ratios were investigated using the TG–FTIR coupling technique. The samples were pyrolyzed within the temperature range of 100–950 °C at 30 °C/min heating rate. The thermal characteristics of oil shale was similar to that of bitumite at the devolatilization stage. The synergetic effect observed during the co-pyrolysis of oil shale with lignite could be attributed to lignite’s high-volatile feature. The optimum proportion of oil shale in the mixture was 50% which led to 1.4% increase in the gas/liquid yield and in the ratio of aromatic C-H/aliphatic C-H in the gaseous products identified by FTIR. Bitumite inhibited the pyrolysis process at the early stage of temperature range from 130 °C to 400 °C during the co-pyrolysis with lignite. This suppression of bitumite existed in the whole pyrolysis process in the co-pyrolysis with oil shale.