Investigation on pyrolysis characteristic of natural coke using thermogravimetric and Fourier-transform infrared method

Natural coke is a kind of fossil fuel with calorific value of 18-28 MJ kg−1. There are abundant natural coke reserves in the world, but at present it is abandoned and needs research and development for its utilization. The morphology comparison between the natural coke from Peicheng Mine, Xuzhou, Jiangsu, China and the bituminous coal from Hanqiao Mine, Xuzhou, Jiangsu, China was made with scanning electron microscopy (SEM). Thermogravimetric analysis (TG) and Fourier-transform ifrared (FT-IR) coupled technology was used to investigate pyrolysis characteristics of the natural coke and the bituminous coal. The pyrolysis products were analyzed with the VECTOR 22 infrared analyzer. The effects of the heating rate, the final pyrolysis temperature, the particle diameter, and the operating pressure on the pyrolysis process of natural coke were examined with the Thermax500 pressurized thermogravimetry. The pyrolysis process of the natural coke can be divided into two different degasification stages, different from that of coal, which includes three stages-drying, semi-char forming and degasification. The results show that TG curve shifts to the higher temperature region as the heating rate increases. The heating rate has almost no effect on the ultimate volatile release. The final pyrolysis temperature has a strong impact on the ultimate volatile release. The higher the final pyrolysis temperature is, the more the ultimate volatile yield is. SEM pictures show that the natural coke at higher temperature has better porous structure, which is beneficial to volatilization, and a better reduction activity. Decrease in the particle size leads to more volatile release. The pressure has less effect on pyrolysis under lower temperature, while the effect becomes stronger when the temperature is higher than a given point.