Evaluation of stage efficiency and mass transfer performance in a spray falling film extractor

Abstract

Higher separation requirements and stricter environmental protection regulations have put forward the development and optimization of efficient extraction equipment. Herein, a novel spray falling film extractor was designed for extraction processes with organic phase being dispersed in droplet and aqueous phase in falling film flow patterns. Tributyl phosphate (in kerosene)-acetic acid-water was used as the extraction system. The extraction performance was characterized by the stage efficiency (SE) and overall volumetric mass transfer coefficient (K_La). The SE and K_La could reach up to 98.8% and 0.288 s⁻¹, respectively, when the resin falling film tube was utilized at the optimal operating conditions. Moreover, the falling film tube with a screw surface structure exhibited superior extraction performance compared to the falling film tube with a smooth surface. Based on the experimental results, a dimensionless equation was provided to correlate K_La with deviations less than ±20%. Further comparison results showed that the spray falling film extractor could provide a higher K_La than traditional extraction columns, which demonstrated application potential as a novel liquid-liquid extraction equipment.