Dewatering coal with supercritical Carbon Dioxide
Sujit Banerjee a, Bhima Sastrib, Salonika Aggarwalc, and Marko Hakovirtac
aSchool of Chemical & Biomolecular Engineering, Georgia Tech, Atlanta, Georgia, USA;
bCrosscutting R&D and Systems Integration, US Department of Energy, Germantown, Maryland, USA;
cDepartment of Forest Biomaterials, North Carolina State University, Raleigh, North Carolina, USA
ABSTRACT
Supercritical CO2 (sCO2) dewaters coal through two mechanisms. For bituminous coal of 9.5% average moisture content the water is dissolved out of the coal and the concentration of water in the bulk sCO2 approximates its solubility limit. For lignite (54% average moisture content) the water extracted by the sCO2 exceeds its solubility limit in sCO2, which implies that a part of the water is displaced from, rather than dissolved out of the coal. Thus, there is a clear distinction between wet coals where most of the water is displaced, as compared to drier coals where the water is dissolved out. Hence, sCO2 dewatering will be especially efficient for high-moisture coals where there is significant free water available for displacement. Precedent for this process is available from the dewatering of wood flakes.
超臨界CO2(sCO2)通過兩種機理使煤脫水。對于平均水分含量為9.5%的煙煤，水從煤中溶解出來，并且散裝sCO2中水的濃度接近其溶解度極限。對于褐煤(平均水分含量為54%)，由sCO2提取的水超過了其在sCO2中的溶解度極限，這意味著一部分水從煤中遷移而不是溶解出來。因此，與大部分溶解了水的干煤相比，驅替了大部分水的濕煤之間存在明顯的區別。因此，sCO2對于有大量自由水可置換的高水分煤，脫水將特別有效。可以通過對木片進行脫水來獲得此過程的先例。
KEYWORDS: Supercritical carbon dioxide, coal, lignite, bituminous, dewatering, solubility
關鍵詞：超臨界二氧化碳， 煤， 褐煤， 煙煤， 脫水， 溶解度
