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.

摘要

超临界 CO ₂ (sCO ₂ ) 通过两种机制使煤脱水。对于平均水分含量为 9.5% 的烟煤，水从煤中溶解出来，并且散装 sCO ₂中的水浓度接近其溶解度极限。对于褐煤（平均水分含量为 54%），sCO 2 提取的水_{超过其在 sCO 2}中的溶解度极限，这意味着一部分水从煤中置换出来，而不是从煤中溶解出来。因此，与大部分水被溶解的干煤相比，大部分水被置换的湿煤之间存在明显的区别。因此，sCO ₂对于有大量游离水可用于置换的高水分煤，脱水将特别有效。该工艺的先例可从木片的脱水中获得。