Investigation on Pyrolysis of Shivee-Ovoo Coal from Mongolia

Abstract

Our present investigation on Shivee-Ovoo coal focused on characterization of the initial coal and it’s hard and liquid products after pyrolysis. First of all on the basis of proximate and ultimate analysis of Shivee-Ovoo coal have been confirmed that the Shivee-Ovoo coal is oxidized brown coal of lignite type with B2 mark. The thermal degradation process of Shivee-Ovoo coal was investigated by thermogravimetric analyzer and first time determined the thermal stability of the coal sample by determination of thermal indices such as T5% -71,85°C; T15% -321,18°C; T25% -490,64°C from the TG curve, which are the characteristics of lower thermal stability. The pyrolysis of Shivee-Ovoo coal carried out at different heating temperatures and determined the yields of obtained hard, liquid and gas products. A most suitable heating temperature was chosen 500°C, in which the yield of condensed liquid product-6,28% (tar) was higher. The yield of all liquid (tar and pyrolysis water) and gas products (44%) shows that there was an intensive thermal decomposition of the coal organic mass with higher degree of conversion. This results also confirm the above mentioned and determined lower thermal stability characteristics of Shivee-Ovoo coal and it is more suitable for gasification and liquefaction. Also the yield of hard product (semicoke) is 56,48% at 500°C, which is also important product of the pyrolysis of Shivee-Ovoo coal and it’s proximate analysis results show that the volatile matter content decreased 3 times and increased caloric value by 1000 kcal in comparison with the initial coal sample indicating that it can be used as a smokeless fuel. The determined chemical composition of pyrolysis tar in group organic compounds by chemical analysis show that the tar consists mostly neutral oils with highest content-81,9%, asphalteines-13,6%, free carbons-3,93% and organic bases, organic acids, phenolic compounds are less than 1,0%. The tar also was distilled at room temperature and obtained several fractions with different boiling temperature ranges including yellow colored light fraction-15,93% (18-1800С ), brown colored middle fraction-15,44% (180-3300С ) and black colored heavy fraction-44,53% (330 >0С ). The images of scanning electron microscopes (SEM) of prepared activated carbon from pyrolyzed hard residue in comparison with initial coal sample are different. The SEM image of initial coal sample has compact solid pieces. The SEM image of carbonized and activated coal sample shows a porosity structure with meso and macro pores in comparison with that of initial coal sample. The solubility and chemical composition of neutral oil isolated from the pyrolysis tar of Shivee-Ovoo coal investigated by GC/MS analysis and registered totally 68 peaks (signals) for the soluble in hexane , 100 peaks for the soluble in toluene and 100 peaks for the soluble in a mixed solvent of methylenchloride and methanol (1:1 volume ratio) fractions. Have been determined and identified 22 organic compounds soluble in hexane, 45 organic compounds soluble in toluene and 21 organic compounds soluble in a mixed solvent of methylenchloride and methanol fractions from each related totally registered peaks.