Biodiesel
59
standard methods and limits are described with reference to ASTM/EN/
IS standards.
3.4.1 Flash Point
Flash point is defined as the lowest temperature corrected to a barometric
pressure of 101.3 kPa (760 mm Hg), at which application of an ignition source
causes the vapors of a specimen to ignite under specified conditions of a test.
Flash point of the fuel is evaluated as per ASTM D93 test method.
Flash point of biodiesel is higher than that of diesel (>130ºC), which makes
biodiesel safer than diesel in handling and the storage point of view. A
minimum flash point for biodiesel is specified in restricting the alcohol content. Flash point of biodiesel will reduce drastically if the alcohol used in
production of biodiesel was not completely removed. Moreover, it reduces
the combustion quality of fuel. Excess methanol in the fuel may also affect
engine seals and elastomers and corrode metal components.
3.4.2 Water Sediment
Water and sediment is a test that determines the volume of free water and
sediment in middle distillate fuels having viscosities at 40°C in the range
1.0–4.1 mm 2 /s and densities in the range of 700–900 kg/m 3 . ASTM D 2709
test method evaluates the water content in the biodiesel. If any water is present in biodiesel, water can react with the biodiesel making FFAs and can
support microbial growth in storage tanks.
The water and sediment content did not change in most cases with
increased triglycerides content. While biodiesel is generally considered to be
insoluble in water, it actually takes up considerably more water than diesel
fuel. However, water is deliberately added during the washing process to
remove contaminants from the biodiesel. This washing process should be
followed by a drying process to ensure the final product will meet ASTM D
2709. Sediments may plug fuel filters and may contribute to the formation of
deposits on fuel injectors and other engine damage. Sediment levels in biodiesel may increase over time as the fuel degrades during extended storage.
3.4.3 Kinematic Viscosity
Kinematic viscosity is the resistance to flow of a fluid under gravity. It is the
time taken for a fixed volume of fuel to flow under gravity through the capillary tube viscometer immersed in a thermostatically controlled bath at 40ºC.
It is the product of measured time flow and calibration constant of viscometer. The kinematic viscosity is a basic design parameter for the fuel injectors used in diesel engines. Fuel viscosity has influence on fuel droplet size
and spray characteristics. Viscosity is inversely proportional to temperature.
Viscosity of biodiesel increases with chain length and degree of saturation.
59
standard methods and limits are described with reference to ASTM/EN/
IS standards.
3.4.1 Flash Point
Flash point is defined as the lowest temperature corrected to a barometric
pressure of 101.3 kPa (760 mm Hg), at which application of an ignition source
causes the vapors of a specimen to ignite under specified conditions of a test.
Flash point of the fuel is evaluated as per ASTM D93 test method.
Flash point of biodiesel is higher than that of diesel (>130ºC), which makes
biodiesel safer than diesel in handling and the storage point of view. A
minimum flash point for biodiesel is specified in restricting the alcohol content. Flash point of biodiesel will reduce drastically if the alcohol used in
production of biodiesel was not completely removed. Moreover, it reduces
the combustion quality of fuel. Excess methanol in the fuel may also affect
engine seals and elastomers and corrode metal components.
3.4.2 Water Sediment
Water and sediment is a test that determines the volume of free water and
sediment in middle distillate fuels having viscosities at 40°C in the range
1.0–4.1 mm 2 /s and densities in the range of 700–900 kg/m 3 . ASTM D 2709
test method evaluates the water content in the biodiesel. If any water is present in biodiesel, water can react with the biodiesel making FFAs and can
support microbial growth in storage tanks.
The water and sediment content did not change in most cases with
increased triglycerides content. While biodiesel is generally considered to be
insoluble in water, it actually takes up considerably more water than diesel
fuel. However, water is deliberately added during the washing process to
remove contaminants from the biodiesel. This washing process should be
followed by a drying process to ensure the final product will meet ASTM D
2709. Sediments may plug fuel filters and may contribute to the formation of
deposits on fuel injectors and other engine damage. Sediment levels in biodiesel may increase over time as the fuel degrades during extended storage.
3.4.3 Kinematic Viscosity
Kinematic viscosity is the resistance to flow of a fluid under gravity. It is the
time taken for a fixed volume of fuel to flow under gravity through the capillary tube viscometer immersed in a thermostatically controlled bath at 40ºC.
It is the product of measured time flow and calibration constant of viscometer. The kinematic viscosity is a basic design parameter for the fuel injectors used in diesel engines. Fuel viscosity has influence on fuel droplet size
and spray characteristics. Viscosity is inversely proportional to temperature.
Viscosity of biodiesel increases with chain length and degree of saturation.