The higher the value of the viscosity, the thicker
the plant oil becomes. A high viscosity of the oil
can cause low pumping speed and harder filtering
possibility. That's why it will be favourable for
the filtering process to have a rape seed oil
temperature between 20 and 35 ° C, depending on the
filtering technology.
Biodiesel
Biodiesel is a fuel that has much the same
characteristics as normal diesel oil, but as opposed
to diesel it is not derived from petroleum but from
vegetable oils or animal fat. Generally, vegetable
oils are used such as sunflower oil, soy oil, rape
oil or palm oil. Used oils may be used likewise very
well indeed. To produce biodiesel from these oils,
they are subjected to a chemical reaction, which is
called transesterification. It is a chemical
reaction that makes the glycerol present in the oil
to be substituted by methanol, using a lye as a
catalyst. Its result is a methyl ester. One of its
examples is rape methyl ester (RME). A residue forms
due to transesterification, called glycerine. This
can be applied in various ways, one can think of
such things as making soap.
Why?
Biodiesel's plus-points are obvious: It is
biodegradable, it decreases soot-emission with ±
50%, it decreases emission of hydrocarbons and it is
CO 2 -neutral. In addition to these environmental
plus-points, it is safe indeed (its flashpoint is ±
170C º) and it is easy to mix with fossil diesel.
Where?In
several European countries, including Austria,
Italy, Spain, Frace and Germany biodiesel is
seriously applied, with France and Germany as
absolute leaders. Over 150,000 cars run on biodiesel
in Germany, for instance, and scattered over the
country there are well over 1,200 service stations
with a biodiesel pump. The reason of the biodiesel
success in Germany is the fact that no excise is
levied on biodiesel, which makes its price an
average of 4-8 cents below that of normal diesel. In
the Netherlands we are hopelessly trailing behind in
the use of biodiesel. One of its reasons is the
uncompromising attitude of the Dutch government
towards biodiesel. An example is the fact that it
does not intend to lift excises on biodiesel.
Eventually they will come round in the Netherlands,
mainly due to pressure from Europe and European
legislation with regard to biofuels.
What is
transesterification?
 |
The process of converting vegetable oil into
biodiesel fuel is called transesterification,
and is fortunately much less complex than it
sounds. |
|
|
Transesterification
refers to a reaction between an ester of one
alcohol and a second alcohol to form an
ester of the second alcohol and an alcohol
from the original ester, as that of methyl
acetate and ethyl alcohol to form ethyl
acetate and methyl alcohol . Chemically,
transesterification means taking a
triglyceride molecule or a complex fatty
acid, neutralizing the free fatty acids,
removing the glycerin and creating an
alcohol ester. This is accomplished by
mixing methanol with sodium hydroxide to
make sodium methoxider . This liquid is then
mixed into vegetable oil. The entire mixture
then settles. Glycerin is left on the bottom
and methyl esters, or biodiesel, is left on
top. The glycerin can be used to make soap
(or any one of 1600 other products) and the
methyl esters is washed and filtered. |
Schematic Flowsheet for Straight Vegetable Oil [Click
here]
