hi everybody,
first off all i apologize for my bad english..
i'm a student on chemical engineriing at politecnic of tourin and i make part of project of production of biodiesel and glycerol recovery.. the question is:
we've to purify a feed of 86% (in mass) of glycerol, 0,3% methanol, 9% water, 3% NaCl and the rest is fatty acid. We have to purify glycerol from methanol and NaCl, we have to hold much water as we can becouse we need it for the reactor(is biological process with bacters).. separate methanol from the rest of feed by give heat is immpossible 'couse of to low concentration of methanol make very similar boiling point with water also at low pressure; i've think to separate both water and methanol and then separate them by distillation but is difficult too becouse when we try to separate wather-methanol from the rest of feed also at 0,1 atm and giving heat only all the water become vapour but almost the 50% in mass of 0,3% of the methanol remain in the liquid fraction with glycerol and the other component..
Please give me some idea is really important for me..
thanks!!!
regards from italy!!

what about acidulating the glycern?
mix the glycern(raw) with dilute HCL. this will break down the mix into FFA, glycerin( more pure) and salts. the FFA can be mix with incoming oil to make biodiesel. glycerin(purer) should be fine for the biological processes. the salts. might be usable for fertilizers.

H2S04 could also be used instead of HCL. phosheric as well..DON'T USE nitric acid..

-dkenny

I believe the current commercial process would be to distill the Glycerol off of the salt after removal of the water methanol at a lower temperature. Unfortunatly there appears to be no other physical or chemical process to remove the salts. You would end up with a purer glycerol and a salt rich glycerol.