Dewatering of Ionic Liquids in a Falling Film Evaporator

Abstract

Dewatering of Ionic Liquids in a Falling Film EvaporatorExperimental investigations on the dewatering of ionic liquids (IL) in a single falling film evaporator were carried out.Depending on the process conditions, such as heating temperature and process pressure, a minimum water content of 0.2 wt-% (2000 ppm) was achieved using batch mode. Assuming that these water contents represent equilibrium state at constant temperatures and pressures, vapor pressure curves of different IL-water mixtures were obtained and from these the required heat for evaporation could be estimated. During the dewatering process viscosity was monitored online and proved to be a sufficient and reliable indicator for dewatering progress.

Continuous dehydration of Ionic Liquids in a falling film evaporator

“…Therefore no reference points except those for batch dehydration in a FFE and rotary evaporator could be found [5,9]. As a first benchmark the dehydration to about 0.01 g water /g total was chosen.…”

“…These settings were chosen to exert the identical thermal stress as in batch experiments [5]. Pressure drop on both sides was neglected.…”

“…Using the measured c P from Table 1 and the energy of evaporation from [5] a heat flow into the tube side was calculated exemplarily for one experiment to 4.6 kW m À2 . This heat flow includes the evaporation of the water and the heating of the pump around flow.…”

“…Investigations on batch-mode dehydration of IL in a falling film evaporator were found to be very promising, in terms of achieved water contents <1 ⁄ 10 À3 g water /g total at moderate process conditions, such as heating temperature of 120°C, total pressure of 50 mbar, specific heat flux <15 kW m À2 , and short residence time. Furthermore a dependency of viscosity to water content and temperature showed the possibility to utilize the viscosity as a parameter to monitor water content online [5]. In industrial applications continuous processes often provide great potential savings on specific energy demand against batch processes for larger capacities.…”

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

“…Gentle partial evaporation of the product medium is decisive for product quality, and falling film evaporators are used for this purpose, especially in industrial processes like food production and the evaporation of sucrose solutions [1,2], milk, and fruit juices [3][4][5][6][7][8]. Other applications include solvent separation from oligomers or polymers [9][10][11], separation of petrochemical naphtha [12], and dewatering of ionic liquids [13][14][15].…”