Biodiesel
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will not flow properly and affects the fuel pumps and fuel injectors. CFPP is
less conservative than the cloud point, and is considered by some to be the
true indication of low temperature operability.
3.4.8 Pour Point and Cloud Point
Cloud point is the temperature at which a cloud or haze wax crystals appears
at the bottom of the test jar when the oil is cooled under prescribed conditions. Pour point is the lowest temperature at which the oil is observed to
flow when cooled and examined under prescribed conditions. Biodiesel generally has higher cloud point and pour point than diesel. In saturated fatty
acids, the carbon is bound to two hydrogen atoms by double bonds. More
double bonds in the biodiesel indicate lower cloud point.
3.4.9 Stability
Biodiesel ages more quickly than diesel due to chemical structure of methyl
esters present in biodiesel. Saturated methyl esters in biodiesel increase its
cloud point and cetane number and improve its stability. The unsaturated
fatty acids reduce cloud point and cetane number and reduce its stability
also.
Oxidation stability of biodiesel is evaluated by EN 14214 test method.
Rancimat apparatus is used for evaluating the oxidation stability of biodiesel. Methyl esters are heated at 110ºC under a constant stream of air at the rate
of 10 l/h. The vapors released during the oxidation process, together with the
air, are passed into the jar containing 60 ml of water and electrode. When the
conductivity begins to increase rapidly, it indicates induction period. This
accelerated increase is caused by dissociation of volatile carboxylic acids produced during the oxidation process and absorbed in the water. Rancimat
induction period of 6 hours is defined for biodiesel samples as per biodiesel
specification.
Most of the biodiesel will not meet this specification unless suitable antioxidants are added at suitable treat rate. Stability of biodiesel is influenced
by factors such as presence of air, heat, traces of metal, peroxides, light, and
number of double bonds. Oxidation stability of biodiesel will decrease with
the increase of polyunsaturated methyl esters. Oxidation stability of biodiesel
depends upon the feedstock used in the production of biodiesel. Vegetable
oils such as sunflower or soybean (rich in linoleic and linolenic acids) have
poor oxidation stability.
Iodine number (ASTM D1520 or EN 14111 test method) indicates the tendency of fuel to be unstable. Iodine number refers to the amount required
to convert unsaturated oil into saturated oil. It does not refer to the amount
of iodine in the oil but the presence of unsaturated fatty acids in the fuel.
It indicates the tendency of fuel to be unstable. Unsaturated fatty acids are
prone to oxidation.
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will not flow properly and affects the fuel pumps and fuel injectors. CFPP is
less conservative than the cloud point, and is considered by some to be the
true indication of low temperature operability.
3.4.8 Pour Point and Cloud Point
Cloud point is the temperature at which a cloud or haze wax crystals appears
at the bottom of the test jar when the oil is cooled under prescribed conditions. Pour point is the lowest temperature at which the oil is observed to
flow when cooled and examined under prescribed conditions. Biodiesel generally has higher cloud point and pour point than diesel. In saturated fatty
acids, the carbon is bound to two hydrogen atoms by double bonds. More
double bonds in the biodiesel indicate lower cloud point.
3.4.9 Stability
Biodiesel ages more quickly than diesel due to chemical structure of methyl
esters present in biodiesel. Saturated methyl esters in biodiesel increase its
cloud point and cetane number and improve its stability. The unsaturated
fatty acids reduce cloud point and cetane number and reduce its stability
also.
Oxidation stability of biodiesel is evaluated by EN 14214 test method.
Rancimat apparatus is used for evaluating the oxidation stability of biodiesel. Methyl esters are heated at 110ºC under a constant stream of air at the rate
of 10 l/h. The vapors released during the oxidation process, together with the
air, are passed into the jar containing 60 ml of water and electrode. When the
conductivity begins to increase rapidly, it indicates induction period. This
accelerated increase is caused by dissociation of volatile carboxylic acids produced during the oxidation process and absorbed in the water. Rancimat
induction period of 6 hours is defined for biodiesel samples as per biodiesel
specification.
Most of the biodiesel will not meet this specification unless suitable antioxidants are added at suitable treat rate. Stability of biodiesel is influenced
by factors such as presence of air, heat, traces of metal, peroxides, light, and
number of double bonds. Oxidation stability of biodiesel will decrease with
the increase of polyunsaturated methyl esters. Oxidation stability of biodiesel
depends upon the feedstock used in the production of biodiesel. Vegetable
oils such as sunflower or soybean (rich in linoleic and linolenic acids) have
poor oxidation stability.
Iodine number (ASTM D1520 or EN 14111 test method) indicates the tendency of fuel to be unstable. Iodine number refers to the amount required
to convert unsaturated oil into saturated oil. It does not refer to the amount
of iodine in the oil but the presence of unsaturated fatty acids in the fuel.
It indicates the tendency of fuel to be unstable. Unsaturated fatty acids are
prone to oxidation.