GB2189233A

GB2189233A - Reviving of spent earth from edible oil refining

Info

Publication number: GB2189233A
Application number: GB08609114A
Authority: GB
Inventors: Sin Lian Kheoh
Original assignee: KHEOH AIK LAW ENTERPRISES Pte
Current assignee: KHEOH AIK LAW ENTERPRISES Pte
Priority date: 1986-04-15
Filing date: 1986-04-15
Publication date: 1987-10-21
Also published as: GB8609114D0

Abstract

Spent earth from the bleaching of edible oils is revived by removing fats, coloured bodies and organic impurities by washing the spent earth with an organic solvent, preferably acetone or methylethyl ketone, and then separating the solvent from the earth.

Description

SPECIFICATION Reviving of spent earth from edible oil refining This invention relates to spent earth from bleaching of edible oil and is particularly concerned with the reviving of such spent earth.

During bleaching of edible oil to reduce the colour intensity thereof, bleaching earth or clay which is of montmorillonite type is added to remove coloured material, phospholipids and trace metals such as copper and iron. The residue after the bleaching process is called spent earth.

Spent earth is usually considered to be a waste product, although attempts have been made to extract the oil in the earth before disposing of the latter. Attempts have also been made to revive spent earth for reuse in bleaching. Such attempts involve the complete removal of remnants of fats and like organic compounds by treating spent earth with superheated steam or heating it in kilns to fairly high temperatures.

According to the present invention, there is provided an alternative method for reviving spent earth which comprises washing it with an organic solvent for fatty components thereof to remove fats, coloured bodies and organic impurities in the spent earth and separating the earth from the solvent. The solvents which have been found to be most effective in removing remnants of fats and similar organic compounds are ketones, in particular acetone and methylethyl ketone.

The preferred procedure embodying this invention comprises the steps of: 1. Washing the spent earth with the solvent for a period of at least 15 minutes to extract fats and like organic impurities from the earth; 2. Separating the solvent medium from the spent earth by filtration; and 3. Removing traces of solvent left in the spent earth by heating above 60"C for at least one hour.

The spent earth then obtained can be used for the bleaching of edible oil to produce an extent of bleaching almost as good as that obtained with fresh bleaching earth. Particularly good results have been obtained in the bleaching of palm oil.

The following examples illustrates this invention: EXAMPLE 1 10 g of spent earth from edible oil refining were washed with 20 g of acetone for five hours.

The solution of fats and other organic impurities in acetone thereby obtained was then separated from the spent earth by filtration. The spent earth was then dried at 70"C to evaporate off any traces of acetone, leaving behind 6.8 g of revived spent earth.

Bleaching tests were then conducted to assess the adsorptive power of the revived spent earth and for comparative purposes, unused bleaching earth of the same origin as the spent earth which had been revived was also tested. The tests were conducted by heating 200 g of crude palm oil to 115"C. 4 g of the original bleaching clay or the revived spent earth were added. The temperature of the oil was then increased to 1200C for 15 minutes while working under a vacuum of 25 to 30 mm Hg. Throughout the test the oil was stirred continuously. The bleached oil obtained was then separated from the earth by filtration and its colour intensity was determined as a measure of the extent of bleaching which had taken place.

Colour of oil measured on l-inch (2.54) Lovibond cell Crude palm oil Bleached by original Bleached by acetone bleaching clay revived spent earth 28 Red 9.5 Red 13 Red EXAMPLE 2 10 g of spent earth were washed with 20 g of methylethyl ketone for five hours. The solution of fats and organic impurities in the methylethyl ketone thereby obtained were separated from the spent earth by filtration. The spent earth was then dried at 90"C to evaporate any traces of the solvent, leaving behind 7.1 g of spent earth. Bleaching tests were then conducted in similar manner to the procedures described in Example 1 and the colours of the bleached oils were determined.

Crude palm oil Bleached by original Bleached by methyl bleaching clay ethyl ketone re vived spent earth 28 Red 9.5 Red 15 Red

Claims

1. A method for reviving spent earth from the bleaching of edible oil which comprises washing it with an organic solvent for fatty components thereof to remove fats, coloured bodies and organic impurities in the spent earth and separating the earth from the solvent.

2. A method as claimed in claim 1, wherein the solvent is acetone or methylethyl ketone.

3. A method as claimed in claim 1 or 2, wherein the spent earth is montmorillonite clay.

4. A method as claimed in any preceding claim, which comprises the steps of

1. Washing the spent earth with the solvent for a period of at least 15 minutes to extract fats and like organic impurities from the earth;

2. Separating the solvent medium from the spent earth by filtration; and

3. Removing traces of solvent left in the spent earth by heating above 60"C for at least one hour.

5. A method for reviving spent earth from the bleaching of edible oil, substantially as described in either of the foregoing Examples.

6. Revived spent earth for edible oil bleaching which has been obtained by the method claimed in any preceding claim.