抄録
The use of supercritical carbon dioxide with entrainers as chelating agents has been tested for extracting metals from low rank coal. The metals interested of this study are Fe and Ca. A flow-type apparatus was used. The experiment conditions were 313.2 K and 15.0 MPa. In the case of extraction by pure supercritical carbon dioxide, the recoveries of Fe and Ca were very small. Addition of acetyl acetone and water enhanced the recovery of Fe. On the other hand, addition of acetic acid enhanced the recovery of Ca though addition of water was not effective. Addition of alcohols shows almost no effect on the recovery rate of metals. Furthermore, the effects of particle size of the low rank coal and flow rate of carbon dioxide on the recovery rate of Fe were examined. The recovery rate increased with increasing the flow rate of carbon dioxide and decreasing the particle size of the low rank coal. For comparison with supercritical carbon dioxide extraction, the aqueous solution extractions of Fe and Ca by acetic acid and acetyl acetone aqueous solutions were also performed. In the extraction by acetic acid aqueous solution, the recovery of Ca was very high.
