Desalination of Polyvinyl Butyral (PVB) in an Annular Rotating Flow Field

The chloride ions in the reaction system must be removed to ensure the product quality of polyvinyl butyral (PVB) particles. However, the conventional batch tank washing technology leads to excessive water consumption and poor washing efficiency. Meanwhile, the small density difference between PVB and water makes it difficult to establish a continuous liquid–solid countercurrent flow in conventional equipment. In this work, we propose annular rotating flow washing columns (ARFWCs) for the continuous desalination of PVB. Slurry condensation, washing, and discharge to the next purification step are all integrated into a single column with low energy input. The effects of rotational speed, liquid velocity, temperature, bottom thread configuration, and initial salt concentration on washing performance are systematically investigated and analyzed. The number of washing stages exceeds 2 in the single column, and the maximum space-time capacity at c NaCl,0 = 0.12 mol/L reaches 1.17 kg/(L·h). A mass transfer model based on the N -CSTR assumption is developed and validated with <15% prediction error. Based on this model, a multistage continuous countercurrent washing system is conceptually proposed based on a simulated moving bed (SMB) operation strategy, and its saving-water potential is evaluated through model-based feasibility analysis. This work demonstrates a new particle washing technology with much lower water consumption and higher efficiency.