Absorption of toluene in silicone oil: Effect of the solvent viscosity on hydrodynamics and mass transfer

The purpose of this study was to compare toluene absorption performances using two PDMS of different viscosities (eta = 5 and 50 mPa s, respectively) in terms of hydrodynamics and mass transfer. Three types of packing were tested in a counter-current packed gas-liquid contactor, Raschig rings, IMTP (R), and Flexipac (R). Hydrodynamic results showed that the viscosity of PDMS 50 is not a hurdle to be used with IMTP (R) or Flexipac (R); the pressure drop being around 288 Pa m(-1) for Flexipac (R) at the flooding point (F-G = 0.99 Pa-1/2; L'= 4.95 kg m(-2) s(-1)), which corresponds to an acceptable value for an industrial application. The determination of the loading zones showed that Raschig rings were not suitable for solvents having a high viscosity, such as PDMS 50; they resulted in high pressure drops if compared to IMTP (R) and Flexipac (R). The mass transfer study showed that 100% removal efficiency can be reached for both PDMS using Flexipac (R). For IMTP (R), the removal efficiency is limited to 88% in the presence of PDMS 50. As a result, PDMS 50 should be a relevant absorbing liquid for the removal of toluene in the absorption-biodegradation process, and Flexipac (R) packing should be preferred to IMTP (R). (c) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.