What are the available methods for Polishing?
Free glycerol may remain either as suspended droplets or as the very small amount that does dissolve in the biodiesel. Alcohols can act as cosolvents to increase the solubility of glycerol in the biodiesel. Most glycerol should be removed from the biodiesel product during the water washing process. Water-washed fuel is generally very low in free glyc-erol, especially if hot water is used for washing. However, additional equipment to separate and dry the biodiesel are required and a the waste water needs to be treated for either re-use or for disposal. The other method is to polish the biodiesel through a resin bed. These specially designed resin will absord free glyerin, soap and water. Waterless polishing of the fuel has two other positive rewards: a) the fuel has a longer storage life, and b) the fuel is not saturated with water (biodiesel will hold more water than regular diesel. When using the waterless process, it is very important to control the quality biodiesel it is treating.
