Separation of Volatile Organic Compounds from Viscous Liquids with RPB Technology

Separation of volatile organic compounds (VOCs) from a highly viscous polymer solution was investigated by means of the rotating packed bed (RPB) technology with the aim of minimizing the VOC content in the product stream. The mixtures under study contained polysiloxane, which was separated from low-molecular-weight cyclic siloxane components (LMWSCs) and the VOC xylene at 140 °C. Flash evaporation experiments were performed without additional stripping gas and by varying the operational parameters such as the rotational speed, liquid throughput, and absolute pressure. Among these, the pressure in the RPB (5–20 mbar) had the strongest impact on the final VOC content, while the influence of rotational speed (300–1500 rpm) on the final VOC content was minor. Further, countercurrently flowing stripping gas was used in the RPB equipment. This enabled a strong decrease of the final VOC content compared with the separation without using stripping gas, and the final VOC content decreased with increasing rotational speed in this scenario. The same was found for LMWSCs, and separation efficiencies of up to 100% were achieved, which can be considered a breakthrough for RPB technology. To conclude, the results of this study proved that the RPB technology has the potential of being a very efficient tool for purification of highly viscous liquid mixtures because it enables countercurrent processing of viscous liquids in high-specific-surface-area packings, which is not possible in conventional equipment such as thin-film evaporators.