NAMS 2002 Workshop - ICOM 2008

Membrane Contactors – 1 – Keynote
Friday July 18, 2:15 PM-3:00 PM, O’ahu/Waialua
Modelling Aroma Stripping Under Various Forms of Membrane Distillation
Processes
G. Jonsson (Speaker), Technical University of Denmark, Lyngby, Denmark - gj@kt.dtu.dk
Concentration of fruit juices by membrane distillation is an interesting process as
it can be done at low temperature giving a gentle concentration process with little
deterioration of the juices. Since the juices contains many different aroma
compounds with a wide range of chemical properties such as volatility, activity
coefficient and vapor pressure, it is important to know how these aroma
compounds will eventually pass through the membrane.
Experiments have been made on an aroma model solution and on black currant
juice in a lab scale membrane distillation set up which can be operated in various
types of MD configurations: Vacuum Membrane Distillation, Sweeping Gas
Membrane Distillation, Direct Contact Membrane Distillation and Osmotic
Membrane Distillation. The influence of feed temperature and feed flow rate on
the permeate flux and concentration factor for different types of aroma
compounds have been measured for these MD configurations.
A general transport model for the flux of water and aroma compounds have been
derived and compared with the experimental data. A reasonable agreement
between the modelling and the experiments could be obtained. From the
modelling it was possible to explain the large different in permeate flux and
concentration factor that was observed for the different MD configurations. This is
highly related to the heat and mass transfer resistances in the membrane as well
as in the boundary layers adjacent to the membrane surface and how the driving
force develops along the length of the membrane.