The conversion of long flame coal to caking coal via hydro-modification can not only efficiently utilize the long flame coal but also expand the coking coal resources. In this paper

Indonesia long flame coal was hydromodified in subcritical H_2O-CO systems and the pyrolysis characteristics of different modified coals at different tempratures were investigated. Moreover

soxhlet extraction technology coupled with thermogravimetric(TG-DTG)and Fourier transform infrared spectroscopy(FTIR) analysis methods were used to investigate the effect of structural evolution of modified coal on the distribution of pyrolysis products. The results indicate that

the caking property of the long flame coal was significantly improved after modification in the subcritical H_2O-CO system

and the caking index(GRI) of the modified coal increased with the reaction temperature and reached the maximum at 340 ℃.The increase in the hydrogen content of the modified coal and the yield of soxhlet extraction soluble components increased the yield of modified coal pyrolysis tar while the yield of pyrolysis gas decreased. At the same time

the modification reduced the oxygen content of the modified coal

which led to a decrease of the yield of pyrolysis water. In addition

the increase of the asphaltene component in the modified coal would inhibit its rapid pyrolysis weight loss. After modification

stretching vibration absorption peaks of the aliphatic-CH

-CH_2 and-CH_3 increased

resulting in higher volume fraction of CH_4 and H_2 in the pyrolysis gas of modified coal than that of the raw coal.