The Swelling Properties Of Three Kinds Of Low Rank Bituminous Coals

Low rank bituminous coals including long-flame coal, non-caking coal,1/2caking coal and weakly caking coal, accounted for42.4%in China’s coal reserves. These coals are good raw materials for direct liquefaction. The complex coal structure is an important aspect for high temperature rapid liquefaction process and product, but for these coals, the study of molecular structure is relatively weak. To coal liquefaction process and product, Swelling pretreatment is an important aspect. It can predict the effects of different coal liquefaction and impact of different solvents on the liquefaction.Swelling pretreatment characteristics of three coals were studied in this paper. First, kovac-Peppas method was used to measure the cross-link density of raw coal,and the coal after pyridine extraction coal and cyclohexanone extraction coal. The results showed that the decreased of cross-link density was observed by both pyridine and cyclohexanone of raw coal. And IR and TG were adopted to analyze the raw coal and after extraction coals. The results showed that the pyridine and cyclohexanone extraction played a role in the side chains and bridge bonds of the two coals, and did not influence the basic structural units of aromatic-nuclei.Influential factors such as different kinds of coals, different solvents, different ratio of solvents to coal, different temperature and different time were tested on the swelling characteristic of raw coals. And IR and TG were adopted to analyze the raw coal and swelling coals. We draw the conclusion:in the polar solvent with the increase of the C mass fraction of the coal the swelling degree of the coal reduced, but in the nopolar solvents, the coal changed little. And swelling degree in polar solvents was generally greater than the non-polar solvents. The swelling degree in pyridine and NMP was maximum. With the increase of the ratio of solvent to coal, the swelling degree increased and reached to a certain value swelling degree is not change. With temperature increase the swelling degree increases and in the polar solvent was more obvious than that in non-polar solvent. As time increased, the swelling degree increased, up to reach the swelling equilibrium. By IR and TG analysis it can be seen that the swelling does not change the structure of coal, only the coal structure becomes loose, making the cross-link density reduces.Swelling kinetics behaviors of these three kinds coals were studied in the last part of the paper. Coals swelling in polar solvent dimethyl formamide was much higher than that in non-plar solvent tetralin; The swelling behavior of three coals were consonant with1st grade reaction kinetics. And the activation energy of these coals in two solvents are all less than lOkJ/mol. The swelling activation energy in the cyclohexanone was greater than that in THN. Because the ability of the polar solvents of destructing non-covalent bonds between the coal macromolecules was larger than that in no-polar solvents. Three kinds of coals n values were between0.2-0.4in the two solvents.