关键词: 减压蒸馏, 降膜结晶, 高纯硫酸

Abstract: The existing production processes of highly pure sulfuric acid are complicated，high energy wasting，and high cost. Falling film crystallization process has advantages of environmentally friendly，energy-saving，and simple flow.Vacuum distillation and repeated falling film crystallization processes were applied to purify industrial sulfuric acid，and then the highly pure sulfuric acid reaching BV-Ⅲ level was achieved.The optimal process conditions were acquired：1） most of the impurities in industrial sulfuric acid were moved off by vacuum distillation；2） to obtain coarse crystals by falling film crystallization， crystallization conditions were the initial crystallization temperature of -5 ℃，the cooling step of 0.6 ℃ per 10 min，crystallization time of 80 min，and feed flow rate of 20 mL/min；3） to purify the crude crystals，sweating conditions were the final sweating temperature of 6 ℃，the heating rate of 3 ℃/h，and heating temperature of 0.5 ℃ per 10 min.Therefore，falling film crystallization process  has a wide application prospect to produce high purity sulfuric acid.

Key words: vacuum distillation, falling film crystallization, highly pure sulfuric acid