Mercury is a hazardous chemical that is present in a variety of gas streams
. This work focuses on the removal of mercury from waste-incineration and s
oil thermal treatment off-gas, natural gas and the glycol-overhead in a nat
ural gas dryer by oxidative membrane gas absorption (oxi-MGA). The mercury
in these gas streams is merely present in the metallic form.
Suitable oxidisers were selected and the stability of several oxidiser-memb
rane combinations was tested by a static immersion method and by monitoring
the temporal development of mass transfer for SO2. It was concluded that P
TFE membranes are needed for this application.
Furthermore, the mercury mass transfer was studied. It was found that mass
transfer is limited by diffusion in the liquid phase for relatively weak ox
idisers and by reaction kinetics or diffusion through the membrane for stro
ng oxidisers. With the generated mass transfer data, the required membrane
area and investment costs were estimated.
Finally, the precipitation of mercury sulphide turned out to be the most su
itable method for regeneration of the absorption liquid. It was calculated
that in the case of glycol-overhead treatment, the costs for regeneration o
f the absorption liquid are negligible compared to the costs of the absorpt
ion process. (C) 2001 Elsevier Science B.V. All rights reserved.