Experimental study of gas-liquid mass transfer coupled with chemical reactions by digital holographic interferometry C. Wylock, S. Dehaeck, T. Cartage, P. Colinet, B. Haut 10 th Conference on Gas-Liquid and Gas-Liquid- Solid Reactor Engineering Braga, Portugal June, 26-29, 2011 Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles

Introduction  Gas-liquid absorbers Importance of interfacial phenomena Classical modelling approaches: two-films, penetration, surface renewal… Well validated by numerous experimental works … at the reactor scale ! Few works validating at the diffusion layer scale  Development of experimental tool and procedure enabling the study of gas-liquid absorption coupled with reaction at the interface scale Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 2

Experimental setup  Gas-liquid absorption performed in a Hele-Shaw cell and observed using a Mach-Zehnder interferometer  Test case: CO 2 absorption in NaHCO 3 /Na 2 CO 3 solution Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 3  coupled with chemical reactions in the liquid phase

Experimental setup  Mach-Zehnder interferometer Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 4

Experimental setup  Interferograms processing (see Chem. Eng. Sc. 66, pp.3400) Refractive index variations field Horizontal averaging  profiles Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 5 n

Mathematical modelling Schematic view of the gas-liquid absorption Page 6 Interface Gaseous phase NaHCO 3 /Na 2 CO 3 aqueous solution x=0 Gas - liquid equilibrium Diffusion Chemical reactions X Depth in the liquid phase CO 2 + CO 3 = + H 2 O ⇄ 2 HCO 3 -

Mathematical modelling  Mass transfer coupled with chemical reaction  Physico-chemical parameters  literature correlations  Numerical solving  concentration profiles Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 7 with

Procedure overview Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 8 ExperimentsMass transfer model Refractive index variations profiles Species concentration variations profiles How to compare ?  They have to be converted into a comparable variable  Density variations  Calibration to find correlations

Procedure overview Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 9 ExperimentsMass transfer model Refractive index variations profiles Species concentration variations profiles Calibration (refractometry) Experimental density variations profiles Simulated density variations profiles

Procedure overview Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 10 ExperimentsMass transfer model Refractive index variations profiles Species concentration variations profiles Calibration (refractometry) Experimental density variations profiles Simulated density variations profiles Comparison They match ?

Experiments – model comparison  Experiments compared with simulated profiles Simulated profiles computed with physico-chemical parameters estimated by literature correlations No match  some parameters are not well estimated, especially parameters towards which the model is very sensitive Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 11

Procedure overview Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 12 ExperimentsMass transfer model Refractive index variations profiles Species concentration variations profiles Calibration (refractometry) Experimental density variations profiles Simulated density variations profiles Comparison They match ?Physico-chemical parameter fitting

Procedure overview Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 13 ExperimentsMass transfer model Refractive index variations profiles Species concentration variations profiles Calibration (refractometry) Experimental density variations profiles Simulated density variations profiles Comparison They match ?Physico-chemical parameter fitting

Procedure overview Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 14 ExperimentsMass transfer model Refractive index variations profiles Species concentration variations profiles Calibration (refractometry) Experimental density variations profiles Simulated density variations profiles Comparison They matchPhysico-chemical parameter fitted

Experiments – model comparison  Parameters fitted least-square fitting  Parameters : Correlations OK for h, k 11, K 2 New values for and,corrections for and  Matched results Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 15

Conclusions  Interferometry and procedure OK for the study of gas- liquid mass absorption coupled with reactions at interface scale  Results comparable to mass transfer model provided that some physico-chemical parameters are well estimated  Perspectives  Study of other systems: CO 2 in amines (scrubbing) Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 16

Thanks for your kind attention.

Experimental setup  Gas-liquid absorption performed in a Hele-Shaw cell and observed using a Mach-Zehnder interferometer  Test case: CO 2 absorption in NaHCO 3 /Na 2 CO 3 solution Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 18  coupled with chemical reactions in the liquid phase

Experimental setup  Mach-Zehnder interferometer Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 19

Calibration  Link between refractive index and density Proposed correlation: Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 20, ↳

Calibration  Link between species concentrations and density Proposed correlation: Transfers, Interfaces and Processes Applied Science Faculty, Université Libre de Bruxelles Page 21 ↳↳