Characteristics of a two-stage counter-current rotating packed bed for continuous distillation

A novel two-stage counter-current rotating packed bed (TSCC-RPB) was specially designed for and applied in continuous distillation. The hydrodynamic characteristics of the TSCC-RPB including gas pressure drop and flooding performance were studied with air–water system and air–glycerin solution system. The effects of rotational speed, gas flow rate, liquid flow rate and liquid viscosity on the pressure drop and flooding were examined. Continuous distillation experiments were carried out in the TSCC-RPB with an acetone–water system at atmospheric pressure. The separation efficiency is presented in terms of the number of theoretical plates (NT) and the effects of the operating parameters, such as rotational speed, feedstock temperature, feedstock concentration, and reflux ratio on the separation efficiency were investigated. Experimental results showed that the TSCC-RPB is an efficient gas–liquid contactor having a NT of 4.94–11.57 with a packing thickness of 200 mm.

In fine chemical, biochemical, food and pharmaceutical industries, large amounts of organic solvents are often used to extract or purify the end products. These solvents are generally recycled by distillation to save raw materials and protect the environment. However, most of these off-solvents are batch or semi-continuously collected and recovered. Generally speaking, plants are more likely to deal with these off-solvents as flows to avoid intermediate large volume storage. If a column is employed to deal with these batch or semi-continuous effluents in a continuous distillation, it may need a long time to achieve the steady state for the continuous distillation but a short time for the distillation itself. It also needs a long time for shut-down and cleaning before the next operation. RPBs are supposed to be suitable devices to treat these effluents in this situation due to their easy operation and intensification in mass transfer.Figure optionsDownload as PowerPoint slideHighlights
► TSCC-RPB was specially designed for continuous distillation with novel rotors.
► Hydrodynamics of TSCC-RPB were studied with air–glycerin solution system.
► The optimum rotational speed of TSCC-RPB was determined at about 700 rpm.
► The results showed that TSCC-RPB has a potential for continuous distillation.