What are the technical specifications of vegetable oils that can be used as fuel.

oilBelow is an example of specifications and properties (in RK-Qualitätsstandard) a type of vegetable oil that can be used as fuel. These elements are not necessary and unique properties for prodiorismo type of vegetable oil that can be used as fuel but only an example.

  

Quality Standard for Rapeseed Oil

Quality Standard for Rapeseed Oil as a Fuel (RK-Qualitätsstandard)

Properties /Contents

Unit

Limiting Value

Testing Method

min.

max.

Characteristic properties for Rapeseed 0il

Density (15ºC)

kg/m3

900

930

DIN EN ISO 3675
DIN EN ISO 12185

Flash Point
by P.-M.

ºC

220

-

DIN EN 22719

Calorific Value

kJ/kg

35000

-

DIN 51900-3

Kinematic Viscosity (40ºC)

mm2/S

-

38

DIN EN ISO 3104

Low Temperature Behaviour

-

-

-

Rotational Viscometer (testing conditions will be developed)

Cetane Number

-

-

-

Testing method will be reviewed

Carbon Residue

Mass-%

-

0.40

DIN EN ISO 10370

Iodine Number

g/100 g

100

120

DIN 53241-1

Sulphur Content

mg/kg

-

20

ASTM D5453-93

Variable properties

Contamination

mg/kg

-

25

DIN EN 12662

Acid Value

mg KOH/g

-

2.0

DIN EN ISO 660

Oxidation Stability (110ºC)

h

5.0

-

IS0 6886

Phosphorus Content

mg/kg

-

15

ASTM D3231-99

Ash Content

Mass-%

-

0.01

DIN EN ISO 6245

Water Content

Mass-%

-

0.075

pr EN ISO 12937

 

 

Density  

The kinds of vegetable oil do not differ too much in terms of density. On average density is about 10% higher.

Density

The kinds of vegetable oil do not differ too much in terms of density. On average density is about 10% higher.

Flash Point by P.-M.

Is much higher than with diesel fuel. Makes transportation and handling much more safe.

Calorific Value

Is nearly equal for all vegetable oils, but 10% less in comparison to diesel fuel. Because of higher density the volumetric content of heat value is about the same.

Kinematic Viscosity

For most vegetable oils higher than diesel fuel. Big differences between the different kinds of seeds. If too high, the oil can’t pass the fuel circuit. Heating is one of the measures to enable engines to run on vegetable oil.

Low temperature behaviour

No specification defined up to now. But the low temperature behaviour is of importance for engine cold start and low load. Viscosity is such an indicator for low temperature behaviour.

Cetane Number

No sufficient testing method existing, because the engines for the standardising tests are all conventional diesel engines. When measured with conventional method, Cetane number is worse, nevertheless practice shows, that ignition delay is shortened in comparison to diesel fuel.

Carbon Residue

There is a remarkable correlation to the residues in the combustion chamber, piston rings and valves, so carbon residue should be kept low.

Iodine Number

Is an indicator for double bindings in the molecular structure. It influences the long time stability of properties (important for storage).

Sulphur Content

Sulphur reduces the function of catalysts and causes SOx emissions like Diesel engines. Normally vegetable oil does not contain sulphur.

Contamination

That is the most important property. It blocks filters and nozzles and is abrasive all over the fuel circuit. Must be well controlled.

Acid Value

Shows the content of free fatty acids. Can effect the properties of lubrication oil if bigger quantities reach the oil sump.

Oxidation Stability

Describes the pre-ageing of the oil. With progressing age the viscosity is also increasing continuously. Can also influence the lubrication-oil.

Phosphorus Content

Is depending much on production method for the oil. Phosphorus is dangerous for the engine due to its abrasive function. When the oil is cold pressed or refined normally the content of phosphorus is within the limits.

Ash Content

Concerns the content of oxide- and raw-ash. Ash is abrasive.

Water Content

If emulgated, a higher water content is not disadvantageous (as long the emulgation remains stable, which is very difficult). Normally water will cause problems anywhere in the fuel system.

Practical experience

Shows that the characteristic properties can anyway not be influenced -- but the variable ones can. So a rough oil quality check should mainly be focussed on:

  • Contamination
  • Phosphorus Content
  • Water Content
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