Upgrading of Low Rank Coals and Development of Coal Slurrification Technology.

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The most representative upgrading process of low rank coals is the hot water drying process, which has been extensively investigated in USA,Australia and Japan. The upgrading effect of this process is remarkable, but the cost of upgrading by the hot water drying process is very high. Thus the object of this research was to reduce the cost of upgrading as possible. After several try and error for the different upgrading process, we found that the combined process of vacuum drying and tar coating was the most effective to reduce the cost of upgrading of low rank coals. The usual hot water drying process employs the following temperature and pressure conditions ; T=350ﾟC and P=150atm. On the other hand, the temperature and pressure conditions of the combined process developed in this study were T=300ﾟC and P=5atm, respectively. This means that the cost of upgrading was very much reduced. The slurrification of upgraded coals was successfully done. The apparent viscosity of 60 wt% slurry was less than 1 Pa・s, which means that the coal water slurry prepared by this upgrading process can be used as a feed of coal gasification or direct slurry burning process. The process developed in this study is promising as a coal utilizing process. Feasibility study of this process for the commercial plant is needed to confirm the usefullness of this process.