Effect of Heavy Medium Separation on the Chemical Structure and Pyrolysis Characteristics of Shenfu Coal

Abstract

Although the processing of coal preparation is an increasingly important direction for clean coal technology, the effect of the heavy media separation on the structure, pyrolysis characteristics and products distribution have been less investigated. The raw, clean and tailing coal from dense medium coal preparation plants in Yulin zone was used as the research object, auxiliary by acid washing samples. Combined with the FT-IR, XRD and TG-DTG, the changes of chemical structure and pyrolysis products distribution were studied. Results showed that heavy media separation is an effective method for coal ash-reduction and desulfurization. In terms of coal sample mentioned in the article, the desulphurization ratio and the deash ratio could be reached 63.54% and 72.33% in clean coal. This is consistent with the change of peaks intensity of minerals in infrared spectrum. The further infrared structural parameters indicate that the heavy media separation leads to the increase of polycyclic aromatic hydrocarbon and heavy components in tailing coal to a certain degree. Together with the high ash content reduces the heat and mass transfer processes, which result in the decrease of pyrolysis reactivity. However, the dry and ash free yield of the total volatile matter during pyrolysis process from high to low is in the order: TC>RC>CC>DC. This order is consistent to that of dry and ash free weight loss in TG. A possible mechanism model to explain the pyrolysis products distribution was proposed. Although more oil and gas resources can be generated during the pyrolysis process of tailing coal, it also needs much more energy. This is also another crux of the problem, and to find an equilibrium point for the optimal inorganic mineral content is feasible, which balance the yield of oil-gas products and the energy input.

Keywords: Heavy media separation, physical preparation, Pyrolysis Characteristics, chemical structure