DE-ACIDIFICATION OF FATS AND OILS

Abstract

The present invention relates to a method for treating vegetable oils and/or animal fats comprising a vacuum steam stripping operation, condensing the neutral oils from vapour phase at an elevated temperature, retaining and sending back to the stripping column, allowing steam, volatile fatty acids, micronutrients together with other volatiles to pass to a cold condensation zone, and condensing the volatile fatty acids, micronutrients together with other volatiles in the cold condensation zone, producing a condensate and a stream of steam, non-condensable gases along with traces of fatty acids and other lighter hydrocarbons vapours. The invention may include a distillation step, either between the high and low temperature condensation zones or following the cold condensation zone.

Claims

1. A method for treating vegetable oils and/or animal fats comprising: (i) feeding an oily feed stream to a vacuum steam stripping column operating at a vacuum level of at least 1 mbar, said oily feed stream comprising (a) volatiles, said volatiles comprising volatile fatty acids and other volatiles, (b) micronutrients and (c) neutral oils, and stripping off components comprising volatiles, micronutrients and neutral oils; and recovering non-volatilized neutral oils as a product neutral oil stream; (ii) feeding the stripped off components to a high temperature condensing zone, condensing the neutral oils from vapour phase at an elevated temperature of at least 150 C., obtaining condensed neutral oils, retaining and returning some portion of the condensed neutral oils present in the high temperature condensing zone directly or indirectly to the feed point of the vacuum steam stripping column, and allowing steam, volatile fatty acids, other volatiles, and micronutrients to pass to a cold condensation zone in step (iii) or allowing steam, volatile fatty acids, other volatiles and micronutrients to be fed to a distillation column in a distilling step before the cold condensation zone in step (iii); (iii) condensing the volatile fatty acids, other volatiles and micronutrients in the cold condensation zone at a temperature of at least 25 C., obtaining a condensate comprising volatile fatty acids, other volatiles and micronutrients and a stream comprising steam, non-condensable gases, traces of fatty acids and other lighter hydrocarbons vapours, and allowing said stream to continue to vacuum system; and (iv) distilling comprising step (a) or (b): (a) feeding the condensate from the cold condensation zone to a distilling column and distilling in vacuum of at least 0.001 mbar, and obtaining a fatty acid product stream and a micronutrients product stream; or (b) feeding the steam, volatile fatty acids, other volatiles, and micronutrients into the distillation column prior to the cold condensation zone, and feeding the condensate comprising volatile fatty acids and micronutrients obtained from the cold condensation zone to the same distillation column and conducting a reflux of condensate to obtain a micronutrients product stream from the distillation column and to obtain a fatty acid product stream from the cold condensation zone.

2. The method according to claim 1, wherein the distilling column is selected from the group consisting of short-path distillation, wiped-film evaporators, one or more subsequent vacuum flash operations, and counter-current multistage distillation columns.

3. The method according to claim 1, wherein the vacuum distillation operation in step (iv) is operated within a range from about 1 to about 10 mbar.

4. The method according to claim 1, wherein the vacuum steam stripping column in step (i) is operated within a range from about 1 to about 10 mbar.

5. The method according to claim 1, wherein the high temperature condensing zone in step (ii) is operated at a temperature within the range from about 150 to about 230 C.

6. The method according to claim 1, wherein the cold temperature condensing zone in step (iii) is operated at a temperature within the range of from about 25 to about 80 C.

7. The method according to claim 1, wherein the cold condensation zone in step (iii) provides a cold reflux stream which is sent to the distillation column.

8. The method according to claim 1, wherein said volatile fatty acids comprise free fatty acids.

9. The method according to claim 1, wherein said neutral oils comprise one or more of tri-, di- and mono-acylglycerides.

10. The method according to claim 1, wherein some portion of the condensed neutral oils are indirectly returned to the vacuum stream stripping column after being subjected to one or more of a bleaching operation, a degumming operation or a neutralisation operation.

11. A method for treating vegetable oils and/or animal fats comprising: (i) feeding an oily feed stream to a vacuum steam stripping column operating at a vacuum level of at least 1 mbar, said oily feed stream comprising volatile fatty acids, micronutrients and neutral oils, and stripping off a first stream comprising volatile fatty acids, micronutrients and neutral oils; (ii) feeding the first stream to a high temperature condensing zone, and condensing the neutral oils from vapour phase at an elevated temperature of at least 150 C. to obtain a first condensate comprising neutral oils, and obtaining a second stream comprising steam, volatile fatty acids, and micronutrients; and (iii) feeding the second stream into a cold condensation zone that is operated at a temperature of at least 25 C., and obtaining a second condensate comprising volatile fatty acids and micronutrients and a third stream comprising steam, non-condensable gases, traces of fatty acids and other lighter hydrocarbons vapours, wherein the second stream is optionally fed into a distillation column prior to the cold condensation zone; and (iv) distilling comprising step (a) or (b): (a) feeding the second condensate comprising volatile fatty acids and micronutrients obtained from the cold condensation zone to a distilling column, distilling in a vacuum of at least 0.001 mbar and obtaining a fatty acid product stream and a micronutrients product stream from said distilling column; or (b) feeding the second stream comprising steam, volatile fatty acids, and micronutrients into a distillation column prior to the cold condensation zone, and feeding the second condensate comprising volatile fatty acids and micronutrients obtained from the cold condensation zone to the same distillation column and conducting a reflux of condensate to obtain a micronutrients product stream from the distillation column and to obtain a fatty acid product stream from the cold condensation zone; feeding a portion of said first condensate comprising neutral oils obtained from the high temperature condensing zone into the feed point of the vacuum steam stripping column, and collecting a neutral oils product stream from said vacuum steam stripping column.

12. The method according to claim 11, further comprising feeding the second stream comprising steam, volatile fatty acids, and micronutrients obtained from the high temperature condensate zone to the cold temperature zone, and obtaining the micronutrients product stream from the cold temperature zone.

13. The method according to claim 11, further comprising feeding the third stream obtained from the cold condensation zone to a vacuum system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 discloses a simplified diagram of the prior art method according to U.S. Pat. No. 6,750,359 for treating vegetable oils and/or animal fats.

[0030] FIG. 2 discloses a method for treating vegetable oils and/or animal fats according to one embodiment of the invention.

[0031] FIG. 3 discloses a method for treating vegetable oils and/or animal fats according to an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 illustrates one embodiment of prior art wherein an oily feed stream 1 is feed to a vacuum steam stripping column together with stripping steam 2 and in-leakage of air 3. Fatty acids, micronutrients together with other volatiles, and neutral oils are stripped off and transferred to a high temperature condensing zone. At the high temperature condensing zone a stream enriched in micronutrients 6 is condensed and separated off from the feed. The separated feed is further transferred to a cold condensation zone, producing a fatty acid product stream 5 which is condensed, and a stream 4 of steam, non-condensable gases along with traces of fatty acids and other lighter hydrocarbons vapours, allowing stream 4 to continue to vacuum system. From the vacuum steam stripping column is a product neutral oil stream 7 recovered.

[0033] FIG. 2 is showing a method according to one embodiment of the invention. An oily, pretreated feed stream 1 is fed to a vacuum steam stripping column together with stripping steam 2 and in-leakage of air 3. In the vacuum steam stripping column fatty acids, micronutrients together with other volatiles and neutral oils are stripped off and transferred to a high temperature condensing zone in step (ii). At the high temperature condensing zone the neutral oils are condensed from the vapour phase. The condensed neutral oils are retained and sent back to the stripping column either directly, or indirectly via upstream operations, such as to a bleaching operation and/or to degumming/neutralisation operation. Optionally a purge stream of the condensate from the high temperature condensation loop can be taken out as indicated with the dashed line. From the vacuum steam stripping column a neutral oil stream 7 recovered as product

[0034] The stripping steam, volatile fatty acids, micronutrients together with other volatiles are allowed to pass to a cold condensation zone. At the cold condensation zone the volatile fatty acids, micronutrients together with other volatiles are condensed. A stream 4 of steam, non-condensable gases along with traces of fatty acids and other lighter hydrocarbons vapours are allowed to continue to the vacuum system.

[0035] The condensate of volatile fatty acids, micronutrients together with other volatiles is transferred to a distilling section in step (iv) to separate the condensate into a fatty acid product stream 5, a residual stream 4 of steam, non-condensable gases along with traces of fatty acids and other lighter hydrocarbons vapours, and a stream enriched in micronutrients 6. Residual stream 4 of steam, non-condensable gases along with traces of fatty acids and other lighter hydrocarbons vapours are allowed to continue to the vacuum system. The vacuum distillation operation is selected from the group consisting of short-path distillation, wiped-film evaporators, vacuum flash operations, counter-current multistage distillation columns.

[0036] FIG. 3 is showing an alternative embodiment of the invention. According to this embodiment a distillation operation is placed between the high temperature condensation zone in step (ii) and the low temperature condensation zone in step (iii). A pretreated feed of oil stream 1 is fed to a vacuum steam stripping column together with stripping steam 2 and in-leakage of air 3. Fatty acids, micronutrients together with other volatiles, and neutral oils are stripped off in the stripper column, and transferred to the high temperature condensing zone. At the high temperature condensing zone the neutral oils are condensed from the vapour phase. The condensed neutral oils are retained and sent back to the stripping column either directly, or indirectly via upstream operations, such as to bleaching operation and/or to degumming/neutralisation operation. Optionally a purge stream of the condensate from the high temperature condensation loop can be taken out as indicated with the dashed line. From the vacuum steam stripping column a neutral oil stream 7 is recovered as product.

[0037] The stripping steam, volatile fatty acids, micronutrients together with other volatiles from the high temperature condensate zone in step (ii) is fed to the distillation column. In the distillation column this stream of volatile components meets a distillate stream being returned from the cold temperature condensation step, leading to formation of a reflux of condensate. The distilling column together with the cold condensation stage will thus separate the stripping steam and volatiles from the high temperature condensation zone into a fatty acid product stream 5 together with a stream 4 of steam, on-condensable gases along with traces of fatty acids and other lighter hydrocarbons vapours, and a stream enriched in micronutrients 6. The stream enriched in micronutrients 6 is collected from the vacuum distilling column. The vacuum distillation operation is selected from the group consisting of short-path distillation, wiped-film evaporators, vacuum flash operations, counter-current multistage distillation columns. The overhead condenser for the distillation column and cold condensation step (iii) may thus be combined in a single operation in this embodiment. According to this embodiment the stripping steam may be forced through an upper rectification section in a counter-current distillation column, and this can lead to added pressure drop and requirement for increased diameters in the stripping, rectification and condensation sections to compensate for this, and/or requirement for a more expensive vacuum system providing a deeper suction pressure. Therefore, the choice between the embodiments of the invention, will depend on the circumstances in a specific design case such as type of oil to be treated, whether a new installation of retrofit to an existing installation.

EXAMPLES

Comparative Example

[0038] In this comparative test were the oils fed to the stripper column at 260 C. and 1% steam is applied for stripping, according to the method shown in FIG. 1. The high temperature condensation is taking place at 170 C. and the low temperature condensation at 55 C., in both cases simulated by scrubbing the vapours with a condensate at those temperature levels. The vacuum level at the top of the cold condensation stage was 2.3 mbar. The mass balance was established using a process simulator (PRO/II from SimSci-Esscor) combined with a proprietary Alfa Laval property database for lipids. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Stream 1 2 3 4 5 6 7 Flow [kg/hr] 41666.7 437.0 10.0 467.1 272.4 128.1 41260.0 Composition [wt %] TAG 96.7625 0.0011 11.9955 97.7122 DAG 1.8000 0.2169 25.4838 1.7378 MAG 0.0500 0.0001 4.9954 3.9431 0.0053 FFA 0.6000 0.0381 89.0850 5.3519 0.0006 Tocopherols 0.1350 2.4985 20.1158 0.0574 Sterols 0.6000 2.9684 32.9213 0.4843 Squalene 0.0025 0.0955 0.1851 0.0013 Water 0.0500 100.00 97.8210 0.1392 0.0036 0.0012 Air 100.00 2.1408 100.00 100.00 100.00 100.00 100.00 100.00 100.00

[0039] The mass balance deviation was 0.011 kg/hr.

Example of the Invention

[0040] In this example was the high temperature condensation stage operating at 185 C., according to the method shown in FIG. 2. A multistage distillation column was used to produce the enriched micronutrient stream 6. The distillation column has 3 equilibrium stages, a reboiler and a condenser was simulated with a condenser pressure of 2 mbar. Reboiler temperature was 204 C. and the condenser operated at the bubble point of 42 C. The target purity of the micronutrient product was set at 20 wt % tocopherol in this example.

[0041] All other conditions was kept as in the example above of the background art, except the steam stripping columns were adjusted slightly to target the same concentration of tocopherol in the product oil stream 7.

[0042] It is apparent from the example the virtual absence of tri-acylglycerides, i.e. TAG, and the very low content of di-acylglycerides, i.e. DAG, in the micronutrient product 6. The FFA product had complete absence of TAG and DAG and only traces of mono-acylglycerides, i.e. MAG. The effect of the new configuration of the hot condensation stage has reduced the neutral oil loss from 67 kg/hr to only 23 kg/hr.

[0043] The new configuration shows virtually no loss of tocopherols or other micronutrients to the FFA product stream, the loss of tocopherols being less than 0.03 wt % of the tocopherols in the feed stream, which is about 16 grams per hour. The overall test results are shown in Table 2

TABLE-US-00002 TABLE 2 Stream 1 2 3 4 5 6 7 Flow [kg/hr] 41666.7 437.0 10.0 467.1 194.8 162. 41289.1 Composition [wt %] TAG 96.7625 0.0088 97.6473 DAG 1.8000 1.8527 1.8092 MAG 0.0500 0.1247 12.1728 0.0019 FFA 0.6000 0.0320 99.6104 34.2555 0.0002 Tocopherols 0.1350 0.0081 20.0000 0.0574 Sterols 0.6000 0.0063 31.3615 0.4819 Squalene 0.0025 0.0005 0.3487 0.0011 Water 0.0500 100.00 97.8268 0.2499 0.0011 Air 100.00 2.1411 100.00 100.00 100.00 100.00 100.00 100.00 100.00

[0044] The mass balance deviation was 0.002 kg/hr.

[0045] Recalculated to annual losses (at 330 operating days per year) this corresponds to a loss of 126 kg/of tocopherols and 183 ton/yr of neutral oil. In monetary terms these losses therefore translates to 4300 $/yr tocopherol value and 0.22 mill $/yr neutral oil losses, total of about 0.22 mill $ lost per year. Compared to the loss of 2.5 mill $/year applying the prior art we find that the invention recovers about 90% of the value of those losses.