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Free fatty acid measurement

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article image The Applikon online titrator.

THE measurement of free fatty acid concentration is important in the refining of edible oils (vegetable oils) and in the manufacture of biodiesel.

Free fatty acids are present in vegetable oils and are removed in the refining process. Removing the free fatty acids is performed by conditioning the oil with phosphoric acid to optimise precipitation of gums and trace elements.

Caustic soda solution is mixed with the conditioned oil which neutralises the acid as well as reacting with the free fatty acids in the oil and forming soap. The soap and precipitated materials agglomerate and are separated out from the neutralised oil.

As such the level of free fatty acids is an important parameter in the processing of vegetable oils. By on-line measurement, the refining process can be optimised by reducing the chemical costs which, in turn, provides improved product quality.

Biodiesel Production

The biodiesel reaction requires caustic (NaOH or KOH) as a catalyst as the methanol and vegetable oil raw materials will not react on their own to make biodiesel.

The oil feed stock for biodiesel plants varies from vegetable oils to tallow and waste oils and each contains different levels of free fatty acids (FFA).

Similarly to the edible oil refining process the free fatty acids will react with caustic to make soap before the caustic has a chance to participate in the reaction to form the biodiesel end product.

Again, it is important to know the level of free fatty acid present in the feed stock so the appropriate amount of caustic can be added to react with the FFA and still provide enough concentration to catalyse the reaction between the oil and methanol to produce the maximum amount of the desired biodiesel final product.

How is FFA measured?

The measurement of FFA can be performed by the Applikon online titrator, available from B-R Controls . The Applikon titrator uses a classical lab methodology to determine the concentration of FFA in a range of oils.

The titration involves reacting the sample with 50mL of an ethanol/ether mixture that also contains a phenolphthalein indicator. The sample is then titrated with a 0.05N solution of potassium hydroxide to the inflection point which is indicated by a change of colour of the phenolphthalein from yellow to red and is detected by a photometer at a wavelength of 560nm.

For increased accuracy, a blank titration is performed prior to each measurement.

Sample specification:

Temperature: Up to 90°C

Pressure: Max 10 bar

Measurement range: 0.03 - 3% (standard), other ranges are possible by changing concentrations of reagents.

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