Upgrading and Slurrification of Low Rank Coals

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The utilization of low rank coal has benefit for the strategy of safe and stable energy supply and for the reduction of energy cost. However, the use of low rank coal is at mining site is limited. The development of cheaper and safer handling and transportation technology is necessary to increase the utilization of low rank coal. Among the low rank coals, some kinds of Brown coals or Lignite have good quality i.e. low ash content, high volatile matter content and low sulftu' content. However, they contain quite a large amount of water, and once the low rank coal is dried, the spontaneous burning becomes a severe problem. Thus the development of effective upgrading technology is a key point for the utilization of low rank coals.The most effective upgrading method seems to be consisted of the combined process of the drying, surface modification by heating up to 300*400* and tar coating. In this joint research. Kobe University and Yatnaguchi University have developed the combined upgradin … More g process of vacuum drying and tar coating. and it was shown that the upgraded coal obtained in this process was good quality with reduced cost. ITB(Institute of Technology. Bandung. Indonesia) has developed the combined upgrading process of Super-heated steam drying and tar coating. The upgraded coal thus obtained was also proved to have a good quality. However, we don't have any certification that such upgraded coals are free from the spontaneous burning during the storage and transportation. The evaluation of the spontaneous burning of the upgraded coals is the key echnology for the future study of upgrading the low rank coats.The other chose the upgrading process is to employ the wet upgrading process. The representative wet process is the Hydro-Thernat Dewate.ring Process (HTD Process). This process is consist of the heating process of coal-water mixture up to 300*400* and the coat water preparation process. The surface characteristics of low rank coal is modified under high temperature and high pressure. Kogoshima University has revealed out the upgrading effect on the low rank coal under HTh process. Monash University employed the combined process of HTh and the mechanical expression processes. The resulting coal waler slurries showed a good quality for the direct burning in the slurry combusting boilers. The rheotogical characteristics of coal water slurries was investigated at University of Melbourne and University of Newcastle. Also, both Yamaguchi University and Kobe University gave the index for the selection of effective additives for the preparation of upgraded coal water slurries. Less