Application of the Hyper-coal process for low rank coals upgrading

摘要

The low rank coals, such as sub-bituminous and brown coals, are characterized byrnthe abundant reserves and the worldwide distribution. In spite of those, the marketrnvalue of the low rank coal is generally small due to low heat value and highrnpropensity of spontaneous combustion. In addition, brown coal contains a largernamount of moisture (20-60 %). It causes the high transportation. Therefore, utilizationrnof the low rank coal is limited in the present situation, such as a feedstock for the localrnpower plant. On the other hand, the low rank coal contains a small amount of ashrnand/or sulfur. Therefore, the increasing in the low rank coal utilization will be anrneffective way to promote the clean coal diffusion.rnHyper-coal process, which has been developed since 1999, is an ash free coalrnmanufacturing process by using the solvent de-ashing technology. Coal is extractedrninto the coal-derivative two ring aromatics at 350-380 ℃. The solution is separatedrnfrom the insoluble residue by the gravity settling and/or the filtration. Solvent isrnrecovered and recycled in the process. Ash-free extracted coal (Hyper-coal, HPC)rnand ash-concentrated insoluble coal (RC) are obtained in this process. Usually, somernbituminous coals are found out to get a high yield of Hyper-coal (>60%) [1].rnThis study concerns with applying the Hyper-coal process for the low rank coalrnupgrading. Several kinds of low rank coals were used in this study. As a result of therncoal extraction test, HPC yield from Mulia coal (Indonesian brown coal, 29 % ofrnwater, 2 % of ash and 0.2 % of sulfur) was only 38 % on daf, and the insoluble coalrnyield was 55 % on daf. Usually, such a yield structure cannot be accepted inrneconomy, since the insoluble coal usually has lower value than the raw coal. On thernother hand, in this case, the obtained insoluble coal contains only 5 % of ash, and thernheat value was increased from 4700 kcal/kg to 7300 kcal/kg. Those improvementsrnwere produced not only by the effect of dewatering, but also by the effect ofrnremoving the oxygen-containing functional groups. It can be said that the Hyper-coalrnprocess will be an effective way to upgrade the low rank coals, which produces notrnonly the ash-free coal, but also the high value coal from a low rank coal.