Study On The Swelling Characteristics And The Molecular Weight Of Two Kinds Of Low Rank Bituminous Coals

At present, coal occupies the largest proportion in China’s energy structure, so the clean utilization of coal is particularly important, which can be reliazed by many ways, including coal liquefaction, coal gasification, and poly-generation technology, etc., however fully understanding the structure information of coal is the foundation of coal utilization. The swelling equilibrium method and the dilute solution viscosity method in polymer physics may be used to study coal structure.In this paper, two low rank bituminons coals were chosen, named710and712. Raw coal712was washed, and removed the mineral matter, the influence of the mineral matter on coal swelling ratio was analyzed, and then the influence of different solvents, solvent alkaline, the solubility parameter of solvents, metal inorganic salt, pretreatment, oxidation on the swelling ratio of raw coal710,712and washed coal712were analyzed, their swelling kinetics processes were further studied. The results showed that:Acid-washing made coal swelling ratio increase; The swelling ratio of three coals in polar solvent was greater than that in nonpolar solvent, the swelling ratio in the mixed solvent was greater than a single solvent; If coal’s solubility parameters was very close to solvent’s solubility parameter, the swelling effect of coal was better; Drying reduced moisture in coal, the swelling ratio decreased, acid washing, alkaline washing, preliminary swelling, the swelling ratio increased; Oxidation reduced the macromolecular crosslinking density of coal, the swelling ratio increased.Then, the structure of raw coal, oxidized coal and swelling coal were analyzed by the infrared spectrum, the results showed that:The macromolecular structure of two kinds of raw coals were similar; Compared with raw coal, oxidiation increased the amount of oxygen-containing functional groups and hydroxyl, reduced the amount of aliphatic and aromatic; Compared with raw coal, the body structure of swelling coal had not changed, just became loose, different kinds of metal inorganic salt differently promoted coal swelling.Next, the swelling dynamics of two kinds of raw coals in THN and pyridine solvents were analyzed, we found that their swelling process followed the first-order kinetics equation; With the increase of temperature, the swelling ratio increased gradually; Their n values were not larger than0.3; Their activation energy value were within20kJ·mol-1, and the activation energy value of two kinds of coals in THN were larger than that in pyridine, the activation energy value of710coal was larger than712coal in the same solvent.Finally, the viscosity average molecular weight of small molecular compounds in coal were measured by the method of dilute solution viscosity, and we found that the viscosity average molecular weight of small molecular compounds of these two kinds of low rank bituminous coals were about30000-50000, but which were just relative, and remains to be further researched.