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A process for dewatering spent ion exchange resins (gel and porous) used in nuclear power plants by supercritical CO2 (sCO2) is described. The amount of water removed by sCO2 is much higher than that expected from solubility considerations alone. Water from gel-type resins is both dissolved by and emulsified in sCO2. Emulsification also occurs in the absence of solids when water alone is contacted by sCO2. It is not a factor for microporous resins where an additional mechanism, viscous fingering, is involved. It appears that bulk water is emulsifiable but not if it is held in pores. Dewatering via viscous fingering has been previously invoked for matrices such as wood and sludge. The resins can be dewatered and dried with sequential batches of sCO2 at sub-boiling temperatures. The CO2 can then be potentially reused after expansion and separation from the entrained water. Partial decompression of the water-laden sCO2 would lead to cooling, which would drop the water solubility substantially. A reduction of temperature from 90 oC to 65oC reduces the solubility of water in sCO2 by a factor of five. The condensed water could then be separated with a hydrocyclone. The footprint of sCO2 is much smaller than the conventional drying process. The energy costs are also much lower because evaporation of water is avoided. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A process for dewatering spent ion exchange resins (gel and porous) used in nuclear power plants by supercritical CO2 (sCO2) is described. The amount of water removed by sCO2 is much higher than that expected from solubility considerations alone. Water from gel-type resins is both dissolved by and emulsified in sCO2. Emulsification also occurs in the absence of solids when water alone is contacted by sCO2. It is not a factor for microporous resins where an additional mechanism, viscous fingering, is involved. It appears that bulk water is emulsifiable but not if it is held in pores. Dewatering via viscous fingering has been previously invoked for matrices such as wood and sludge. The resins can be dewatered and dried with sequential batches of sCO2 at sub-boiling temperatures. The CO2 can then be potentially reused after expansion and separation from the entrained water. Partial decompression of the water-laden sCO2 would lead to cooling, which would drop the water solubility substantially. A reduction of temperature from 90 oC to 65oC reduces the solubility of water in sCO2 by a factor of five. The condensed water could then be separated with a hydrocyclone. The footprint of sCO2 is much smaller than the conventional drying process. The energy costs are also much lower because evaporation of water is avoided. [ABSTRACT FROM AUTHOR]

Supercritical CO 2 (sCO 2 ) removes water from brine held in pumice stone at levels well above the solubility of water in sCO 2 . The higher water removal results from a combination of passive emulsification of water in sCO 2 and viscous fingering of sCO 2 through the saturated pumice. This leads to higher levels of salt deposition than that expected from solubility considerations alone. These deposits could impact the injectivity of sCO 2 as well as its movement in the subsurface. The finding that the water concentration in sCO 2 is not necessarily capped at the solubility limit should influence the parametrization of injection models., (© 2024 National Ground Water Association.)