(709a) Hydraulics and Operation Performance of Gas Dispersed Liquid-Liquid Extraction in a Multiphase Taylor-Couette Disc Contactor

Industrial separation and reaction steps often require more than one phase. Distinct phase contact of solids (S), liquids (L), and gases (G) forms the physical backbone of state of the art process intensification and optimization. Novel reactor and contactor design for liquid-liquid operations serve in optimizing the contact of two phases as for example in bubble columns or liquid-liquid extraction columns [1].

The novel and simple Taylor-Couette Disc Contactor (TCDC) design is based on the rotating disc contactor but without stator discs and with an increased rotor shaft diameter. The optimized TCDC design avoids any formation of hydraulic deadzones [2,3]. Previous investigations showed that stable continuous three phase flow (LLS) in the TCDC offers access to combinations of heterogeneously catalyzed chemical reactions with phase transfer of products in one single apparatus. Adding a fourth gaseous phase to the TCDC column opens a completely new fields of application. Continuous four phase contact (GLLS) enables to perform heterogeneously catalyzed carbonylation reactions with simultaneous phase transfer of the reaction product in one single column. The Taylor-Couette Disc Contactor perfectly complies with this requirement and provides access to continuously contact various combinations of solid, liquid and gaseous phases.

First investigation of an additional gas phase showed that the gas dispersed liquid-liquid extraction column allows to overcome the operation limits given by the flooding point of the column. Overcoming this operation limit comes with a with improved mixing and mass transfer in the TCDC column. This work is focused on the gas phase behavior in the Taylor-Couette Disc Contactor. Perforated discs allow the gas phase to continuously rise up in the column. A gaseous phase can be used as inert auxiliary power input to improve column performance or even as reactive component in the multiphase flow system. The Adjustable rotational speed, and airflow rate provide defined and uniform volumetric gas holdup up to 23% along the column height. The simple TCDC design allows easy scale up in height and diameter to ensure the required throughput and defined residence time. The influence of different perforation pattern regarding the gas phase holdup was observed in a TCDC column with 50mm inner diameter and 700mm active height. For the hydrodynamic test system air was used as gaseous phase, deionized water as continuous liquid phase, ShellSol-T as dispersed liquid phase and Amberlyst 15 as solid phase. In addition, the hydraulics of continuous GLS and GLL and even GLLS flow in terms of droplet size distribution, residence time and holdup of the gas phase, the dispersed liquid phase and the solid phase were investigated in reliance to the interaction of rotational, speed and specific phase flow rates. Flow regime maps for the gas phase show the changing flow pattern according to changing flowrates and rotational speeds. The first results of this investigations impressively show the unique and flexible field of application for industrial use of the TCDC column.

[1] Aloisiyus Y. Widianto, et al., Catalysis Today, https://doi.org/10.1016/j.cattod.2019.02.064

[2] E. Aksamija, C. Weinländer, R. Sarzio, M. Siebenhofer, Sep. Sci. Technol. 2015, 50 (18), 2844–2852. DOI: 10.1080/01496395.2015.1085406

[3] A. Grafschafter, G. Rudelsdorfer, M. Siebenhofer,(2018). Hydraulics and Operation Performance of TCDC‐Extractors. Chemie Ingenieur Technik. 90. 10.1002/cite.201800031.