WO1992004429A1

WO1992004429A1 - Process and device for separating undesired foreign substances from fluids with low or no electrical conductivity

Info

Publication number: WO1992004429A1
Application number: PCT/DE1991/000715
Authority: WO
Inventors: Jürgen GRUNDMANN; Jürgen Lau
Original assignee: Grundmann Juergen; Lau Juergen
Priority date: 1990-09-11
Filing date: 1991-09-05
Publication date: 1992-03-19
Also published as: DE4028805A1; CA2091452A1

Abstract

A process for separating undesired foreign substances from vegetable, animal and maritime oils and fats. During refining or fractionated crystallisation, an electrostatic field is generated in the oil to be treated by means of at least one positively charged electrode. The solid particles deposited on one and/or the other electrode through crystallisation are mechanically removed at the end of the process. The clarified or depleted oil is discharged.

Description

Method and device for separating undesired substances from liquids with little or no electrical conductivity

The invention relates to a method and a device for separating undesired accompanying substances from liquids with little or no electrical conductivity, in particular from vegetable, animal and maritime oils and fats.

In the course of the refining of vegetable, animal and maritime oils and fats, pre-cleaning represents a first process step, followed by such finishing steps as deacidification, bleaching and deodorization. The purpose of the cleaning is to remove unwanted accompanying substances such as phosphatides, mucilages and other complex colloidal compounds which have a disadvantageous effect on further refining. The preliminary cleaning therefore also takes place by means of a so-called degumming. The procedure depends on the type of oil and the content of mucilages and phosphatides. For example, oils regularly have a phosphatide content of 100 to 500 mg / l, which should be reduced to a residual content of 4 to 7 mg / l before deacidification. The processes used today differ in principle by different chemical additives, the water content, the treatment temperatures and residence times. For example, hydrolysis of the mucilage is known, which requires the separation of the aqueous mucus phase from the oil - preferably via centrifuges. In this context, predominantly phosphoric acid and citric acid are used as reagents. However, there is a contaminated water content between 6% and 12%, which must be disposed of. - In combination with an alkaline neutralization, the

Ersa Mucilage into the reaction product "soap" (soapstock), the treatment with sulfuric acid (decomposition) represents an additional and considerably polluting process.

A further method is known in which, after hydrolysis has taken place, bleaching earth is added at moderate temperature and then heated to 140 to 170 ° C. under vacuum, so that the water evaporates. After cooling to approx. 100 ° C, the mixture of bleaching earth and mucilage is separated by filtration. Since the impurities still present inactivate the bleaching earth, relatively large amounts of bleaching earth must be used. This is associated with increased fat loss.

Another occasionally used method also presupposes the principle of hydrolysis. B. lecithin is added. Here too, the phases are separated using centrifuges. This process achieves residual contents of 5 to 17 mg / 1 and requires a further process step such as bleaching in order to achieve the low values mentioned at the beginning.

Many vegetable oils receive waxes as a further undesirable accompanying substance. In contrast to the glycerol esters, these are fatty acid esters with long-chain alcohols, which have a high melting point and are lipase resistant. Their share in the oil is between 0.5% and 2%. The dewaxing, also called winterization, is energy and time consuming, is associated with losses due to a high fat content in the filter cake and is problematic in terms of disposal. A centrifugal process also found a fat content in the wax phase of 20% to 70%, with additional wastewater problems due to additive

Spare sheet tive to come.

The separation of undesired accompanying substances such as fat accompanying substances also includes the removal of stearins in the course of fractional crystallization: in the oil and fat industry, crystallization processes are used to obtain liquid oils, special fats and for so-called winterization. Several stages are often carried out. The known processes regularly work in such a way that crystals of the higher-melting components, such as glycerides, which are as large as possible and therefore easily filterable or separable, are produced and are then separated off from the so-called mother liquor in a further process step. The crystal is produced in agitator tanks with suitable heating and cooling options. The separation operation is generally carried out by filters, centrifuges, sieves, decanters and filter presses. The quality of the crystals has an important influence on the separation operation. This is associated with great effort if the crystals have a broad distribution spectrum of the grain size or are of a soft consistency. In any case, the disadvantage of all crystallization processes is the dependence on the crystal form which can be obtained.

The invention is based on the object of specifying a method for separating undesired accompanying substances from liquids, in particular from vegetable, animal and maritime oils and fats, which is characterized by environmental friendliness and low energy expenditure, taking into account a simplified separation operation with a significantly reduced process time. In addition, one is said to carry out of the method simple and functional device can be created.

In terms of the method, the invention achieves this object in that, in the course of refining in the liquid to be treated, at least one positively charged electrode and one negatively charged electrode generate an electrostatic field of a predetermined field strength, and in that By crystallization onto the solid particles depositing one and / or other electrode after completion of the crystallization and the clarified liquid can be removed or removed separately. The invention is based on the knowledge that solid particles can be moved in a barely or non-conductive liquid with the aid of electrostatic forces. With solid / liquid separations of oils and fats it is e.g. B. solid fat accompanying substances and fat crystals, which can be moved in an electrostatic field relative to the surrounding liquid substance between positively and negatively charged electrodes. The field strength can be set up in such a way that the attachment force of a crystal lattice site to an electrode becomes greater than the electrostatic field force. Then the solid particle in question remains stationary on this electrode. This process can be demonstrated, for example, with butterfat or palm oil in an arrangement which corresponds in electrical design to a cylindrical capacitor with a central electrode. If the positive pole is applied to the central electrode at a field strength of approx. 1 KV / mm and the clear melt is cooled, then the solid phase or the solid article is deposited on the central electrode. After the crystallization has ended, the depleted liquid phase or the clarified oil can be removed from the

He Arrangement to be drained. The solid phase or the solid particles remain on the central electrode and can be removed mechanically or by melting.

If, in the same arrangement, raw sunflower oil is cooled from approx. 70 ° C. in a field of 1 KV / mm to 20 ° C., needle-shaped crystals are formed, which grow concentrically radially towards one another from both electrodes. If the field strength is reduced to 0.3 KV / mm and the temperature is lowered to 6 ° C, then the crystals are deposited on the outer electrode and remain stationary. The oil between the two electrodes is completely clear and can be removed. Storage of the oil cleaned in this way does not lead to precipitation of cloudy substances even over a long period at only 6 ° C. Surprisingly, dewaxing of sunflower oil is achieved. Furthermore, a chemical analysis shows that even undesired phosphatides have been removed.

The method according to the invention can be applied to all liquid substances if they have little or no electrical conductivity. It can be used for the purpose of refining liquid substances if substances dissolved therein can be converted into the solid state by supersaturation and these substances are to be separated from the mother liquor by immobilization. Areas of application for refining or cleaning are degumming, dewaxing, removal of foreign substances and natural accompanying substances such as waxes, sterols and cholesterol in, for example, sunflower oil, soap, shea fat (removal of isoprene.. Corn oil, cod liver oil, herring oil, mink, beef tallow, p : nmaiz, Walόi, fish oil, wheat germ oil. In the context of the method according to the invention, however, a separation of fats or fractional crystallization is also possible. Because the invention recommends that by way of a frak¬ tioned crystallization by means of an electrostatic field of sufficient field strength a ^'pendulum motion of the solid-solid particle between the electrodes produced relative to the liquid-resistance and the liquid is slowly cooled under field influence, and that, finally, solid particles deposited on one and / or other electrode are removed after the clarified or depleted liquid has been discharged. In this context, the invention is based on the knowledge that when the field strength is sufficiently high, a solid particle which touches one of the two electrodes charges to the potential of the electrode in question and is repelled at the same moment in the direction of the counter electrode. The same process takes place on the counter electrode, so that the solid particle moves in the opposite direction. In terms of process technology, the rapid pendulum movement between the electrodes relative to the liquid can advantageously be used instead of a bath movement generated by mechanical stirring for the exchange of heat and material and, moreover, leads to a homogeneous mixture. This applies in particular when the melt or mother liquor is cooled under the influence of the field. The resulting crystals are oriented in the direction of the electric field lines and can be moved relative to the liquid phase at high field strengths. A much faster heat and mass transfer is achieved than with the otherwise usual stirring. As is known, in the course of a fractional crystallization, the melt is allowed to cool slowly with careful stirring in order to make it as large and easily filterable as possible

Spare sheet Obtain crystals of the higher melting glycerides. Consequently, in the context of the process according to the invention, glyceridic oils and fats can be subjected to fractional crystallization in a particularly advantageous manner in order to obtain more usable solid or liquid parts. This applies, for example, to palm oil, palm kernel oil, coconut fat, shea fat, cottonseed oil, olive oil, milk fat, beef tallow, lard, peanut oil, etc.

The process according to the invention can be carried out not only batchwise, but also semi-continuously and continuously.

The invention also relates to a device which is particularly suitable for a functionally appropriate implementation of the method according to the invention. This device is characterized by at least one reactor with liquid inlet and liquid outlet and a positively charged electrode and a negatively charged electrode in the reactor. The procedure is such that the reactor is filled and then the separation and immobilization process is carried out by applying the appropriate field strength. In the following step, the liquid phase is removed from the reactor and the remaining solid phase is discharged mechanically or melted off by the application of heat. Electrodes and reactor can be arranged horizontally or vertically. The horizontal arrangement is preferred if the holding force of the solid phase or solid particles on the electrodes is σeπng and mechanical discharge is used. The electrodes themselves can be adapted in terms of material and geometry to the requirements of the substances to be processed.

The advantages achieved by the invention are first of all time to see that a drastic reduction in process time is achieved. This is because the recharging effect realized within the scope of the invention moves individual solid particles in the respective liquid. Here, taking into account a sufficiently large field strength, an intensive mixing and stirring effect can be achieved. The relative movement between the solid particles and the mother liquor is significantly improved, so that at the same time an optimized heat and material exchange is achieved on the crystallization front. In addition, the separation operation is simplified considerably by immobilizing the solid phase. The separation process is independent of the crystal form. Consequently, the method according to the invention is particularly suitable for separation operations in which the crystal formation is disturbed by accompanying substances with a certain surface activity and nucleation effect in such a way that crystals which are difficult to filter are formed. However, the method according to the invention is also environmentally friendly because, in contrast to conventional methods, no auxiliaries are required which have to be disposed of. A chemical neutralization during fat refining can consequently be dispensed with. In fact, a substantially more environmentally friendly physical refining is achieved. Finally, the method according to the invention is characterized by low energy consumption. Because the build-up of the necessary field forces requires minimal current strengths in the order of microamps. Heating and cooling operations are kept to a minimum. The expenditure on equipment is extremely low due to the elimination of filters or centrifuges. Finally, multi-stage arrangements with different temperature treatments and field strengths can be easily implemented.

Spare sheet The invention is explained in more detail below with reference to a drawing showing various exemplary embodiments; show it:

1 shows a device according to the invention with a reactor and central electrode,

2 to 7 modified Ausführungsfor en of the object of FIG. 1,

8 shows a multi-stage reactor arrangement,

Fig. 9 shows a hexagonal E. Λtrodenanordnung with switchable center electrodes and

10 shows a traveling field arrangement made of switchable electrodes.

1 shows a reactor 1 designed as a glass tube with liquid inlet 2 and liquid outlet 3 as well as a positively charged central electrode 4 which is surrounded by a negatively charged spiral electrode 5. The center electrode 4 or coil electrode 5 can optionally be designed as a positively charged electrode.

2, the reactor is designed as a cylindrical tube 6 with a positively charged center electrode 4, the tube 6 forming the negatively charged electrode.

3 and 4, a reactor is realized with a positively charged center electrode 4, which is charged by negatively charged

Replacement sheet NEN electrodes 5 in a symmetrical distribution, for example polygonal distribution is surrounded. According to FIG. 3, a quadratic distribution, according to FIG. 4 a hexagonal distribution of the negatively charged electrodes 5 is provided.

5 shows a reactor designed as a trough 7 for the liquid to be treated, with a disk 8 rotating in the trough 7 with a wiper 9 assigned to the disk 8, the trough 7 being the negatively charged electrode and the disk 8 being the form a positively charged electrode.

According to FIG. 6, the reactor is designed as a tube 10 with a continuous endless chain 11 and the stripper 12 is assigned to the endless chain, the endless chain 11 carried through the tube 10 forming the positively charged electrode and the tube 10 forming the negatively charged electrode. Instead of the endless chain 11, an endless wire can also be provided.

7 shows a reactor which is designed as a screw housing 13 with screws 14 a, 14 b arranged in parallel and at a predetermined distance from one another and driven in opposite directions. One screw 14a forms the positively charged electrode and the other screw 14b forms the negatively charged electrode, so that the solid particles are transported in the edge region of the screw spiral in the direction of the arrow.

The embodiments according to FIGS. 2 to 7 are preferably suitable for a continuous mode of operation, according to which the solid particles are continuously removed from the reactor, while the liquid stream of the clarified liquid can be drawn off continuously. A semi-continuous mode of operation can then be achieved, for example

Spare sheet if three reactors la, 1b, lc mt each center electrode 4, a common inlet line 15 and a common Ablaufleitunglβ with the interposition of each inlet valve 17 and outlet valve 18 are arranged in a row. This is because the filling / clarifying / emptying steps of the middle reactor 1b can then be overlapped with the clarifying / emptying steps of the upstream reactor 1 a and the filling / clarifying steps of the downstream reactor 1c or carried out simultaneously.

FIG. 9 shows an embodiment according to which a plurality of reactors 1, each with a hexagonal arrangement of the negatively charged electrodes 5 and positively charged center electrode 4, are arranged in series. By reversing the polarity of the central electrodes 4, the solid particles attached to the central electrodes 4 can be transported in the direction of the arrow. This is also achieved with the traveling field arrangement of electrodes 19 shown in FIG. 10, in which a plurality of electrodes arranged in at least three parallel rows is provided, of which the middle row has positively charged electrodes 20 and by shifting or Switching over the electrostatic field, the deposited solid particles can be transported in the direction of the arrow.

Spare sheet

Claims

1. A process for separating undesired accompanying substances from liquids with little or no electrical conductivity, in particular from vegetable, animal and maritime oils and fats, characterized in that in the course of refining in the liquid to be treated by means of at least one positive charged electrode and a negatively charged electrode, an electrostatic field of a given field strength is generated, and that the solid particles deposited by crystallization on one and / or another electrode separate after the end of crystallization and the clarified liquid be performed.

2. The method according to claim 1, characterized in that in the way of a fractional crystallization by means of an elek¬ trostatic field sufficient field strength produces a Pendelbe¬ movement of the solid particles between the electrodes relative to the liquid and the liquid is slowly cooled under the influence of field, and that the solid particles that finally adhere to one and / or another electrode are clarified after the clarified liquid has been drained off.

3. The method according to claim 1 or 2, characterized in that the refining and fractional crystallization are carried out dis¬ continuously, semi-continuously or continuously.

. Device for carrying out the method according to one of claims 1 to 3, characterized by at least one reac-

etching sheet Gate (1) with liquid inlet (2) and liquid outlet (3) and a central electrode (4), which is surrounded by a spiral electrode (5).

5. The device according to claim 4 and independently thereof, characterized in that the reactor is designed as a cylindrical tube (6) with a positively charged center electrode (4), the tube (6) forming the negatively charged electrode

6. Apparatus according to claim 4 or 5, independently thereof, characterized in that a positively charged central electrode (4) is surrounded by negatively charged electrodes (5) in a symmetrical distribution, for example polygonal distribution, in a reactor.

7. Device according to one of claims 4 to 6 and independend thereof, characterized in that the reactor as a trough (7) for the liquid to be treated with a disk (8) rotating in the trough and a scraper assigned to the disk (9 ) is formed, the trough (7) forming the negatively charged electrode and the disk (8) forming the positively charged electrode.

8. Device according to one of claims 4 to 7 and independend thereof, characterized in that the reactor is designed as a tube (10) with a circulating endless chain (11) or endless wire and the endless chain (11) or the endless wire is a stripper ( 12), the endless chain (11) or the endless wire passing through the tube (10) forming the positively charged electrode and the tube forming the negatively charged electrode.

Replacement sheet

9. Device according to one of claims 4 to 8 and independend thereof, characterized in that the reactor is formed as a screw housing (13) with parallel arranged at a predetermined distance from one another and driven in opposite directions screws (14a, 14b), the one screw (14a) the positively charged and the other screw (14b) the negatively charged electrode.

10. Device according to one of claims 4 to 9 and independend thereof, characterized in that several, for example three reactors (la, 1b, lc), a common feed line (15) and a common drain line (16) with intermediate circuit each have an inlet valve (17) and an outlet valve (18) and are arranged in series for semi-continuous operation.

11. The device according to one of claims 4 to 10 and independently thereof, characterized in that the reactor as the central electrode (4) has a hollow electrode with inwardly rotatably mounted jacket parts and a central suction for the solid particles.

12. The device according to one of claims 4 to 11 and independently thereof, characterized in that several reactors, each with a hexagonal arrangement of the negatively charged electrodes (5) and positively charged center electrode (4), are arranged in series one behind the other.

13. Device according to one of claims 4 to 12 and independently thereof, characterized in that a plurality of in at least three pa-

Spare sheet electrodes (19) arranged in parallel rows are provided, of which the middle row has positively charged electrodes (20) and the deposited solid particles can be transported in a predetermined direction by shifting or switching over the electrostatic field.

Spare sheet