Study of thermoplastic properties of coal under pressure

The pressure dependence of fluidity of four kinds of coals was measured under various atmosphere; (Ar, He, N/sub 2/ and CO/sub 2/) by means of pressurized Gieseler plastometer. Taiheiyo coal is non caking at ambient conditions, but it showed fluidities of 2 to about 4 DDPM at higher than 20 kg/cm/sup 2/G. Maximum fluidity of Horonai coal, that is called slightly caking, increased from 3 to 100 DDPM as the pressure rose from 0 to 50 kg/cm/sup 2/G, and this tendency was common with every gas used for this experiment. Two kinds of Akabira coal whose maximum fluidities are 130 and 430 DDPM at O kg/cm/sup 2/G were also tested. When the lower fluid one was pressurized with Ar, the maximum fluidity--pressure curve showed a peak at 10 kg/cm/sup 2/G and the peak height was 6000 DDPM. Such a peak was observed for other gases except He; the height and the position of these peaks were as follow: 6000 DDPM at 40 kg/cm/sup 2/G for N/sub 2/ and 3200 DDPM at 20 kg/cm/sup 2/G for CO/sub 2/. Under He atmosphere, maximum fluidity increased smoothly with pressure and attained to 7000 DDPM at 50 kg/cm/sup 2/G. In the case of higher fluid one, the peak in curve appeared for all the gas, used and each height and position were as follow: 45000 DDPM at 10 kg/cm/sup 2/G for Ar, N/sub 2/ and CO/sub 2/, and 47000 DDPM at 20 kg/cm/sup 2/G for He.