CS216818B2 - Method of separating the grease substances on the components presenting different thawing temperatures - Google Patents

Abstract

Verbesserung des in DE-PS 23 17 563 beanspruchten Umnetzverfahrens zur Auftrennung von Fettgemischen in Komponenten unterschiedlicher Schmelzpunkte.

Das Trennverfahren wird in zwei hintereinander geschalteten Trennstufen durchgeführt, wobei die in der letzten Trennstufe erhaltene wäßrige Dispersion der höher schmelzenden Fettstoffanteile in die Vakuumverdampfungsstufe der aufgeschmolzenen Fettstoffgemische zurückgeführt wird und dort mit dem wärmeren, noch nicht auf die gewünschte Trenntemperatur abgekühlten Ausgangsmaterial vereinigt wird.

Der Vakuumverdampfung in der ersten Trennstufe kann eine Kühlvorrichtung, insbesondere eine Kühlstufe mit Kratzkühlern vorgeschaltet sein, in der 10 - 40 % der insgesamt auszukristallisierenden höherschmelzenden Fettstoffanteile vorkristallisiert werden.

Description

The invention relates to a process for separating fatty substance mixtures into components having different melting points.

Subject of MS. No. 188,917 is a process for separating fatty material mixtures into components of different melting points by a process consisting of

a) partially or totally melting the mixture of fatty substances, b) cooling to crystallize the protruding fractions of fatty substances, the heat dissipation required to cool and crystallize these sub-elements being achieved by vacuum evaporation of the aqueous phase in direct contact with the mixture c) in the preparation of a dispersion of separated liquid and solid particles of fat substances, d) in the separation of this dispersion by centrifuges into an oily phase containing non-fat fractions and an aqueous phase containing crystallized fractions of fat substances in dispersed form and e ) in the separation of the recovering proportions of fatty substances from the aqueous phase by filtration or melting and subsequent centrifugation or settling, the method being characterized by the following measures:

Adding an aqueous, non-surfactant electrolyte solution to the molten fat mixture and evaporating a portion of the water of the electrolyte solution under vacuum while vigorously stirring to partially or completely crystallize the above portion in step b), and adding a wetting solution to disperse the liquid and solid fat, preferably while maintaining a vacuum and continuing to evaporate water until the separation temperature in step c) is reached.

The process according to the patent can be carried out in several separating stages by subjecting the oily phase obtained in step d), which contains lower amounts of fatty substances, to the same separating procedure once again at a lower temperature level. If necessary, further separation steps may follow. The aqueous dispersion of crystallized, protruding fatty substances obtained in step d) except for the oily phase is then further processed according to step e).

In this multi-stage process, the final separation temperature is only reached in the last separation stage. The consequent stepwise crystallization and separation of the proportion of the rising fat substances can, in particular, result in a purely oily phase having a low melting point.

However, the process of said patent is still. still has some drawbacks, especially when hardly crystallizable fatty substances are to be separated. Delayed crystal formation in the vacuum firing stage can then occur up to 161818, resulting in a lower throughput or lowering of the crystals. to inferior quality of end products. This delayed crystal formation is the reason why the process of the present patent cannot in many cases be used in practice or with insufficient results.

Another disadvantage of this process is that the aqueous dispersions of crystallized, protruding fat fractions obtained in the multi-stage process of step e) must be processed by themselves, requiring separate production facilities and processing steps, in particular higher consumption. energy for melting the solid fatty substances present in the dispersion. Co-processing of the dispersions obtained is generally not possible because of the different fat fractions obtained.

It is an object of the present invention to provide an improved process for separating a mixture of fatty substances into components having different melting points, wherein the improvement consists in the process and the quality of the products obtained.

Accordingly, the present invention provides a process for separating fatty material mixtures into components having different melting points by a process consisting of

(a) in the partial or total melting of the mixture of fatty substances,

b) cooling down to crystallization of the above-mentioned fat fractions, the heat removal necessary for cooling and crystallization of these fractions being achieved by vacuum evaporation of the aqueous phase which is in direct contact with the fatty substance mixture,

c) forming a dispersion of separated liquid and solid particles of fatty substances,

(d) separating the dispersion by means of centrifuges into an oily phase containing fat-bearing portions and an aqueous phase containing crystallized fat-containing portions in dispersed form; and

(e) separating the fat-containing extracts from the aqueous phase by filtration or melting and then centrifuging or settling, the method being characterized in that the separation process is carried out in several successive cutting stages, the aqueous dispersion of the fat-extracting extracts obtained in The separation step dj of the subsequent separation step, carried out by means of centrifuges, in which, in addition to the aqueous dispersion containing the protruding fat fractions in dispersed form, an oily phase containing the reducing proportions of fat substances is returned to the vacuum evaporation operation b) of the previous separation step. there it is combined with a warmer starting mixture not yet cooled to the desired separation temperature of this stage.

The back-dispersed dispersion serves immediately to cool and disperse the used fatty substance mixture.

In this way, it is possible to increase the throughput of the existing plant and to avoid further costly or difficult measures to improve the tendency to crystallize mixtures of fatty substances to be separated, such as removal of impurities, or by special measures related to the production plant and dispersion treatment process. containing investigative proportions.

The process according to the invention is therefore carried out as follows:

Dividing stage I

(a) Partial or complete melting of the fatty substance mixture:

b) adding an aqueous phase containing crystallized proportions of the fatty substances in dispersed form, as well as wetting agents and electrolyte, from operation d) of the separating stage II to the molten fatty substance mixture and evaporating some of the water under vacuum while vigorously stirring until partial or complete crystallization investigating shares;

c) further adding an aqueous solution containing wetting agents and an electrolyte from step

e) separating stage I (dilution with the return solution), optionally with the addition of fresh surfactant, electrolyte and water, dispersing liquid and solid fatty substances, preferably while maintaining vacuum and continuing to evaporate water until the separating temperature is reached;

(d) separating the dispersion by means of centrifuges into an oily phase containing non-volatile proportions of fatty substances and an aqueous phase containing crystallized proportions of fatty substances in dispersed form; and

(e) separating the recovered fractions of the fatty substances from the aqueous phase (return solution) by filtration or melting, followed by centrifugation or settling.

Dividing stage II:

The oily phase obtained in step (d) and containing a lower proportion of fatty substances is subjected to a further substantially identical separation at a lower temperature level up to and including step (d). Crystallization and dispersions [steps b) and c) are carried out by dilution with the return solution of step e) of step I, optionally with the addition of fresh wetting agent, electrolyte and water.

However, the aqueous phase obtained in step (d), which contains crystallized proportions of fatty substances in dispersed form, is not further processed as in step (e), but is returned to step (b) of separation stage I. the separation temperature or may lie above this, whereupon the final separation temperature is only reached after further, substantially identical separation stages. In this case, the fat substance suspension obtained in step (d) in each case is then recirculated - as described - to step (b) of the previous separation step.

The process according to the invention can be carried out batchwise or - preferably - continuously. Further details of the separation process, as well as details of the surfactants, electrolytes, etc. used, are given in the art. In particular, the surfactant solution obtained in step e) of separation step I is returned to the separation process as a so-called dilution with the returned solution. However, it is necessary to continuously remove a portion of this solution from the circulation in order to prevent the accumulation of mucilaginous impurities from the used fatty substances which could affect crystallization as well as the quality of the rising fat content. Losses on the wetting agent and the electrolyte that occur are to be compensated by adding fresh wetting agent and the electrolyte. Sodium dodecyl sulfate, such as magnesium sulfate electrolyte, is preferably used as wetting agent. The process must furthermore be controlled so that the water losses that occur during evaporative cooling or removal of the surfactant solution are replaced by the supplied electrolyte solution or the fresh surfactant solution.

The process according to the invention is suitable for separating various mixtures of fatty substances; in particular, mixtures consisting of fatty acids, fatty acid esters or fatty alcohols may be separated when the melting points of the components to be separated are sufficiently far apart.

Of particular technical importance is the separation of fatty acid mixtures into olein and stearin, or mixtures of fatty alcohols into oleyl alcohol and stearyl alcohol. Similarly, mixtures of fatty acid triglycerides, solid at room temperature, can be separated into the incoming and outgoing fractions. Such fatty acid triglyceride fractions are used to produce edible fats. It is not necessary that one of the components to be separated be in the form of an oil liquid at room temperature. The process according to the invention can also be successfully applied even if the two proportions are solid and only sufficiently differ in their melting points.

The process according to the invention can also be altered so that a conventional, indirectly acting cooling device, in particular a cooling step with scraped coolers, is preceded by the vacuum evaporation stage b) of the separation stage I. As a result, a further improvement of the process according to the invention is achieved, in particular with respect to the throughput of the individual devices, since a partially crystallized starting mixture of fat substances is now introduced into the vacuum evaporation stage b) of the separating stage I. Suitably, the proportion of the protruding fractions of the fatty substances pre-crystallized in the scraped coolers is 10 to 40% of the protruding fractions to be totally crystallized.

Particular advantages of the process according to the invention are that the returned aqueous dispersion of the protruding fat constituents greatly improves the tendency of the used fat mixture to crystallize, which appears to be a substantial acceleration of the separation process or a corresponding increase in throughput in the plant. for 1 dividing stage. In addition, it is an important energy advantage that the cold aqueous suspensions of the protruding fractions of the fatty substances from the downstream separation stages are used immediately for cooling the previously downstream stage. Separate processing of this dispersion by melting the fatty matter particles and separating them would require a significant amount of energy, among other equipment.

The return of the aqueous dispersion of the protruding fatty matter fractions from the downstream separation stage to the downstream separation stage in the multi-stage separation process is already the subject of German patent publication DOS 21 00 022. However, in the process according to this publication cooling and returning slurry serve only to disperse the partially crystallized mixture of fatty substances and to simultaneously cool to the separation temperature. The improvement of the tendency to crystallize the fat blends under vacuum evaporative cooling cannot be deduced from the process described in this publication.

The process according to the invention is illustrated by the following examples.

Examples

The procedure is as described in Example 1, no. No. 188,917, but in a two-stage separation apparatus. Crude tallow-type acid at 46 ° C (iodine number 58, cloud point 39 ° C) was charged to the separating stage I vacuum evaporator. This tallow fat acid is mixed with the total amount of the suspension at 26 [deg.] C. obtained in separation stage II with vigorous stirring. A mixed temperature of 36 ° C was established, whereby crystallization of the tallow fat (stearic acid) was started. Further cooling down to 20 ° C is achieved by evacuating the crystallization vessel using a steam ejector.

Addition of a dilution return solution to step (e) of separation stage I, containing 0.2% by weight of dodecyl sulfate as a wetting agent, and optionally additional amounts of wetting agents, electrolyte and water, to compensate for losses, in particular by removing a portion of the dilution return solution which is distributed in a solid-coated centrifuge. The stearin suspension obtained is heated to a temperature in the range from 90 to 95 ° C and the stearin is separated from the dilution return solution in a separator.

The dilution return solution, as mentioned above, is recycled after removal of approximately 20%.

The oily phase obtained in separation stage I (essentially oleic acid, iodine number 82.6, turbidity temperature 21 ° C) is subjected to further separation in separation stage II, also using a dilution return solution of separation stage I as the wetting solution. Cooling to a temperature in the range of 3 to 5 ° C is also carried out by vacuum evaporation. After obtaining the dispersion, separation into a stearin suspension and an oil-like phase as in separation step I is carried out. An olein having an iodine value in the range of 86 to 93 and a turbidity temperature in the range of 1 to 5 ° C is obtained. The stearin slurry containing wetting agents and electrolytes is returned to a vacuum evaporating crystallizer of separation stage I after heating to 26 ° C.

To increase the throughput in the device, it is advisable to use a pre-scratched cooler. The molten fatty acid enters a scraped cooler at a temperature of 46 ° C. After cooling to a temperature of 30 ° C and after a partial fatty acid, it is transferred to a vacuum evaporating crystallizer and further processed as above.

Claims (4)

Process for separating fatty substance mixtures into components of different melting points by a process consisting in partial or complete melting of the fatty substance mixture by cooling down to crystallization of the protruding parts of the fatty substances, the heat dissipation required to cool and crystallize these parts being achieved by vacuum evaporating the aqueous phase which is in direct contact with the fat blend to form a dispersion of the separated liquid and solid fatty matter particles, separating the dispersion by centrifuges into an oily phase containing no lower fractions of fat, and an aqueous phase containing crystallized proportions of fatty substances in dispersed form - and in the separation of the rising proportions of fatty substances from the aqueous phase by filtration or melting and subsequent centrifugation or settling, characterized in that the separation process is carried out in several successive steps the aqueous dispersion of the fatty fat extracts obtained in the separation operation of the subsequent separation stage by means of centrifuges, SUMMARY OF THE INVENTION, in addition to the aqueous dispersion containing the protruding fatty fractions in dispersed form, an oily phase containing the non-aspirating fatty fractions is recycled to the vacuum evaporation operation of the previous separation stage and combined therein with a warmer feed mixture not yet cooled the desired separation temperature in this stage. 2. Method according to claim 1, characterized in that the cutting is carried out in two successive cutting stages. ( 3. A process according to claim 1 or 2, characterized in that it is used for separating mixtures of fatty acids, fatty alcohols or fatty acid glycerides. 4. A method according to any one of claims 1 to 3, characterized in that a cooling operation in the scraped cooling zone is used, which operation is preceded by a vacuum evaporation operation of the separating stage 1, in which the pre-cooling operation is brought to crystallize 10 to 40% the proportion of fatty substances to be totally crystallized.