Course: BFM 202 Biodiesel Production

Lecture

Ion Exchange Technology
Credits
BFM 202 Biodiesel Production Unit 5 Lecture has been adapted from "ENGY 131 Unit 5 Commentary Catalysis" by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Ion Exchange Technology

What is Ion Exchange (resin) and how does it work?

Within the crude biodiesel, undesirable contaminants and water exist as
positively or negatively charged ions. By flowing the biodiesel through
a water-free, methanol-treated resin bed, known as an Ion Exchanger, the
oppositely-charged resin beads absorb those ions. For more information, read:

Ion Exchange Resins for Cleaning Biodiesel: How do they work?

published by the Department of Biological and Agricultural Engineering
at the University of Idaho

These resin beads are located in a column and have a high capacity for
removing soaps and salts without significant pressure drop across the
resin bed. A pressure drop can occur if soap enters the column,
precipitates, then forms an emulsion layer and inhibits flow.
Ensuring there is not pressure drop results in ensuring the process
doesn't reverse and minimizes the energy needed for the process as a whole.

Ion exchange beds can be regenerated which means the unwanted ions are
washed away. This reversible exchange virtually eliminates resin disposal.
Amphoteric ion exchanges are when both positive and negative ions are
exchanged simultaneously. The resin beads used for ionic exchanges is
determined by the ion's size, charge, and/or structure.

The use of dry wash systems, like Ion Exchangers, are based upon plant
economics and demonstrate cost-effective processing. For a continuous-process
biodiesel plant, two columns are recommended. One column is operational,
while the second has spent resin replaced.

Magnesium silicate

Magnesium silicate is a waterless wash method that uses an absorbent
filter to remove contaminants. This filter attracts polar compounds and
absorbs: methanol, free glycerol, mono- and di-glycerides, metals, FFA,
and soap.

This process can increase the oxidative stability of biodiesel in
conjunction with or replacing the water wash. Also the liquid separation
and drying steps can be eliminated. It can also replace alternative
methods of removing chlorophyll, metals, and color from biodiesel.

After glycerol separation and methanol removal, magnesium silicate (a
fine white powder) is mixed with unwashed biodiesel for 5-10 minutes to
remove residual methanol.

The slurry of biodiesel/magnesium silicate passes through a filter press
to remove solid silicate particles and all that's left is a solid filter
cake for disposal.