Nucleation Kinetics of Freeze Crystallization with Various Aqueous Solutions

The nucleation kinetics of ice were investigated with four different types of aqueous solutions. The studied aqueous solutions, i.e., sucrose solution, ionic liquid (IL) solution, pyrolysis oil extract (PO) solution, and acetone-1-butanol-ethanol (ABE) solution, were concentrated by batch suspension freeze crystallization. The nucleation kinetics were investigated using a temperature response method which results in data on nucleation rate per crystal. The obtained nucleation rate per crystal value can be used when dimensioning continuous crystallization processes: the nucleation rate per crystal is inversely proportional to the residence time in continuous crystallization. The subcooling degrees for different solutions were in the range of 0.33 °C to 1.89 °C. Aqueous sucrose solutions had the fastest nucleation kinetics. Ice crystallization from non-ideal aqueous [DBNH][OAc] ionic liquid solutions required higher subcooling degrees and the nucleation rates per crystal were higher as well. Nucleation of ice formed from aqueous pyrolysis oil extract and aqueous ABE solutions occurred at a lower subcooling degree and the obtained nucleation rate per crystal values were lower.