GB2139242A

GB2139242A - Process and apparatus for the deodorisation and deacidification of fats and oils

Info

Publication number: GB2139242A
Application number: GB08411398A
Authority: GB
Inventors: Hans-Martin Stover; Gerhard Plonis
Original assignee: Fried Krupp AG
Current assignee: Fried Krupp AG
Priority date: 1983-05-06
Filing date: 1984-05-03
Publication date: 1984-11-07
Also published as: DE3316523C2; GB8411398D0; DE3316523A1; GB2139242B; BE899513A

Abstract

In a process for the deodorisation and deacidification of fats and oils the fats and oils are mixed with 0.1 to 10% wt. of water, treated for 2 to 10 minutes at 180 to 280 DEG C. and 1 to 3 bars, then freed of excess water at 50 to 500 mbars and finally subjected at 180 to 280 DEG C. and 1 to 20 mbars to a multi-stage water vapour distillation with 0.2 to 1% wt. of water vapour. An apparatus for carrying out the process consists of a liquid mixer 1, a column 2 provided with static miter elements, a vacuum vessel 3 with following vapour condenser 4 and at least two vacuum counter-current columns 5, 6 equipped with unheated trickle elements. <IMAGE>

Description

SPECIFICATION Process and apparatus for the deodorisation and deacidification of fats and oils The invention relates to a process for the deodorisation and deacidification of fats and oils, and to an apparatus for carrying out the process.

The aim of deacidification is the removal of the free fatty acids contained in the fats and oils, which disadvantageously influence the taste and odour of the fats and oils. Fatty acids can be distilled off at elevated temperature with water vapour. The aim of deodorisation is the removal of the troublesome odorous and flavour substances which are present in free or bound form. The odorous and flavour substances, which are predominantly bound to the glycerides, are liberated by hydrolysis and conducted away by the water vapour. However in the deacidification and deodorisation, undesired side reactions also proceed (saponification, thermal decomposi tion, interesterification polymerisation) which must be suppressed.

With specific edible oils and fats, especially coconut oil and palm oil, it can be advantageous to combine the distillative deacidification and the deodorisation by means of water vapour, for in the treatment of the fats and oils with water vapour not only a dissociation of the substances which are volatile under the process conditions, but also a hydrolytic splitting of impurities of the fats and oils take place. The discontinuous or continuous steaming of the fats and oils is carried out in general at 180 to 2704 C. and 5 to 20 millibars for 0.5 to 5 hours, the narrowest possible retention time spectrum, good intermixing and rapid conducting away of the volatile constituents being sought. Especially in continuously working steaming plants the counter-current principle is used, and sieve tray columns or falling-film evaporators come into utilisation.The conducting of the process in the individual case is very greatly dependent upon the nature of the starting material and the demands made of the end product.

The known process has the disadvantage that it requires too long a time ofretention of the fats and oils and that a narrow retention time spectrum cannot always be retained, which leads to undesired side reactions. Moreover the process requires, for the conducting away of the fatty acids and for the hydrolysis of the impurities, a relatively large quantity of water vapour, since the carrier function of the water vapour is utilised only incompletely and the water vapour has only a slight solubility in the oil under reduced pressure.

Furthermore from Fed. German P.S. No.

2,548,487 a process for the deodorisation and deacidification of fats and oils is known in which the fats and oils are firstly treated at app. 246 C. and 50 bars for app. 4 minutes with water and then relaxed to 1 to 40 mbars,while at the same time a counter-current treatment with water vapour can take place at app. 210 C. and 1 to 40 mbars.

Although in this process a short retention time is provided and the fats and oils possess good water solubility on account of the high pressure, on account of the requisite high pressure the known process requires much compression energy and a high energy consumption for the vacuum system, since a great quantity of water of reaction must be drawn off..

The invention is therefore based upon the problem of producing a process and an apparatus for the deodorisation and deacidification of fats and oils which on the one hand have a good separation rate and deliver a high product quality and on the other hand require small quantities of energy and make small process equipment suffice.

The problem upon which the invention is based is solved in that the fats and oils are mixed with 0.1 to 10 % wt., preferably 0.5 to 2 % wt. of water, then treated for 2 to 10 minutes at 180 to 280 C., preferably 250 to 270 C., and 1 to 3 bars, then freed of the excess water at 50 to 500 mbars and finally subjected at 180 to 280 C. and 1 to 20 mbars to a multi-stage water vapour distillation with 0.2 to 1 % wt. water vapour in relation to the fats and oils. This process is distinguished from the two known processes especially in that the fats and oils have a short retention time in the hydrolysis stage and that nevertheless it is not necessary to work under high pressure.It is surprising to the person acquainted with the art that the hydrolytic liberation of the bound odorous and flavour substances takes place nearly quantitatively at only 1 to 3 bars within 2 to 10 minutes without the occurrence of a reduction of the quality of the deodorised and deacidified fats and oils. By the multi-stage water vapour distillation provided according to the invention the free fatty acids and the odorous and flavour substances can be separated off almost quantitatively.

It is further provided according to the invention that in the water vapour distillation the inter-ffacial area amounts to 1,500 to 10,000 sq.m./cu.m. ffats and oils, preferably 2,500 to 5,000 sq.m./cu.m. ffats and oils. A water vapour distillation carried out with this interfacial area renders possible a nearly quantitative separating out of the free fatty acids and of the odorous and flavour substances with a low energy expenditure. The interfacial area provided according to the invention can advantageously be accommodated in trickle-film columns.

The process according to the invention can be used with particular success if the water vapour distillation is carried out in two stages, the first stage working at 230 to 260 C. and 2 to 8 mbars and the second stage at 240 to 270 C. and 3 to 10 mbars. This makes possible a rapid and nearly quantitative separating out of the undesired fat content substances.

Finally according to the invention for carrying out the process an apparatus is proposed which consists of a liquid mixer, a column equipped with static mixer elements, a vacuum vessel with following vapour condenser and at least two vacuum counter-current columns equipped with unheated trickle elements. The individual apparatuses of the process have a comparatively small overall size on account of the short retention time and the column intended for the execution of the hydrolysis reaction can be of a material-saving design on account of its nearly pressureless manner of working.The vacuum countercurrent columns provided to carry out the water vapour distillation can be arranged either side by side or one above the other, so that various possibilities occur in relation to the apparatus arrangement, in the planning of the installation The object of the invention will be explained in greater detail below by reference to the drawing which shows a flow diagram of the process according to the invention.

The deslimed and bleached oil is conveyed out of the tank 1 1 through the conduit 15 into the heat exchanger 16, where the temperature of the oil to be treated is adjusted to app. 50 C. Thc heated oil passes through the conduit 17 into the mixerl,to which water is supplied through the conduit 18 from the tank 19. The fresh water flowing through the conduit 27 into the tank 19 is degasified and demineralised. An intimate mixing of the oil and water takes place in the liquid mixer 1.

The oil-water mixture passes by way of the conduit 8 into the heat exchanger 9 where the adjustment of the hydrolysis temperature, preferably 250 to 270 C., takes place. The heating up of the oil-water mixture must take place slowly and without overheating, since otherwise an uncontrolled hydrolysis would lead to the splitting of a major part of the neutral fat. An uncontrolled hydrolysis is avoided in a counter-current heat exchanger with large specific heat exchange area. Before entry into the heat exchanger 9 the oil-water mixture conducted in the conduit 8 can be pre-warmed with the product flowing in the conduit 20.

The heated oil-water mixture passes through the conduit 10 into the column 2 equipped with static mixer elements, where the hydrolysis reactions proceed which liberate the bound odorous and flavour substances. A padding column serves as static mixer element . The column 2 is so dimensioned that the retention time of the fats and oils lie; at 2 to 10 minutes. The oil-water mixture passes by way of the conduit 12, the pressure valve 1 3 and the conduit 14 into the vacuum vessel 3, the pressure valve 13 having the task of keeping the pressure in the column 2 at 1 to 3 bars.

In the vacuum vessel 3, acting as drier, the major part of the unused water is separated from the oil, while the water vapour phase already conducts away a part of the fatty acids and of the odorous and flavour substances. The charged water vapour phase passes by way of the conduit 21 into the vapour condenser 4, where the charged water vapour phase is liquefied. A pressure of app.

120 mbars, which is maintained by the vacuum pump 22, is established in the vacuum vessel 3 and in the vapour condenser 4. A trouble4ree progress of the multi-stage water vapour distillation is achieved due to the extensive separation of the water in the vacuum vessel 3. The liquid aqueous phase formed in the vapour condenser 4 and containing fat impurities and entrained oil droplets passes by way of the conduit 23 into the separating vessel 24, where an oil phase separates out, leaving the separating vessel 24 by way of the conduit 25. The water collecting in the separating vessel 24 is conveyed by way of the conduit 26 into the tank 19 and fed afresh to the liquid mixer 1. Fresh demineralised and degassed water passes through the conduit 27 into the tank 19.Since the water used for the hydrolysis is conducted in a cycle, the consumption of fresh degassed and demineralised water is very low. The liquid aqueous phase collecting in the vapour condenser 4 can be used also for the pre-warming of the oil in the heat exchanger 16..

The hydrolysed oil collecting in the vacuum vessel 3 is conveyed through the conduit 28 to the top of the vacuum counter-current column 5, to the foot of which water vapour, which is the vapour from the column 6, is fed through the conduit 29. The oil issuing from the vacuum counter-current column 5. still has a fatty acid content of 0.1 to 0.5 % and passes through the conduit 30 at the top into the vacuum counter-current column 6, to which water vapour is fed at the column foot through the conduit 31 to act as stripper gas.

The deacidified and deodorised oil flows away through the conduit 20 and is cooled with exclusion of oxygen. The two vacuum countercurrent columns 5 and 6 are equipped with trickle elements which can be formed as heaps of filler bodies or as plates. The heaps of filler bodies have a pressure loss of less than 0.2 mbar per metre of heap height, and the plates generate a thin oil film which acts as a large interfacial area. In order to avoid thermal decomposition reactions during the water vapour distillation, the trickle elements are not heated. Although the evaporation heat required in the vacuum counter-current columns 5 and 6 is taken from the hot fats and oils and/or the supplied water vapour, in some cases it can be necessary to arrange intermediate heating in the conduit 30. It is possible to arrange the vacuum distillation columns either side by side or one above the other, whereby the overall height of the installation is variable.

The water vapour charged with fatty acids and odorous and flavour substances, issuing from the vacuum counter-current column 5 is conveyed by way of the conduit 32, the vacuum pump 34 and the conduit 33 into the vapour washer 7, where the substances, especially the fatty acids, contained in the water vapour are separated out. The product flowing from the conduit 25 is fed to a suitable reprocessing system.

Claims

1. Process for the deodorisation and deacidification of fats and oils, characterised in that the fats and oils are mixed with 0.1 to 10 % wt., preferably 0.5 to 2 % wt. of water, then treated for 2 to 10 minutes at 180 to 280 C., preferably 250 to 270 C., and 1 to 3 bars, then freed of excess water at 50 to 500 mbars and finally subjected at 180 to 280 C.

and 1 to 20 mbars to a multi-stage water vapour distillation with 0.2 to 1 % wt. of water vapour, in relation to the fats and oils.

2. Process according to Claim 1, characterised in that in the water vapour distillation the inter-ffacial area amounts to 1,500 to 10,000 sq.m. per cu.m. of fats and oils, preferably 2,500 to 5,000 sq.m. per cu.m. of fats and oils.

3. Process according to Claims 1 to 2, characterised in that the water vapour distillation is carried out in two stages with the first stage working at 230 to 260 C. and 2 to 8 mbars and the second stage at 240 to 270 C. and 3 to 10 mbars.

4. Apparatus for carrying out the process according to Claims 1 to 3, characterised in that it consists of a liquid mixer (1), a column (2) provided with static mixer elements, a vacuum vessel (3) with following vapour condenser (4) and at least two vacuum countercurrent columns (5, 6) equipped with unheated trickle elements.