Complex sentence: When the requirement is to concentrate a liquid phase, fractional freezing can be useful due to its simplicity, for example when it is used to increase the alcohol concentration in fermented alcoholic beverages, a process sometimes called freeze distillation.
Split into simpler sentences: When the requirement is to concentrate a liquid phase, fractional freezing can be useful due to its simplicity. Fractional freezing can be used as a simple method to increase the alcohol concentration in fermented alcoholic beverages, a process sometimes called freeze distillation.