TECHNICAL FIELD

The invention relates to a crystallizer. The invention also relates to a fractionation system for edible oils and fats comprising such a crystallizer. The invention also relates to a method for fractionation of edible oils and fats.

BACKGROUND ART

In order to modify edible oils and fats such as palm oil or animal fat a fractionation process may be used. In a fractionation process the starting material is fractioned into distinct products with different physical properties and melting points. One such product is a liquid product with a low melting point commonly known as olein, characterized by being enriched in unsaturated fatty acids. Another products is a solid product with higher melting point commonly called stearin, characterized by being enriched in saturated fatty acids By separating the oils and fats into liquid and solid fractions, products may be created that match exact customer specifications. The process comprises gently cooling of the oil or fat in a controlled process, forming a crystal slurry as certain components crystallize, and then separating the crystals from the crystal slurry. The crystallization is performed in a crystallizer which typically comprises a vessel where the starting product is fed into one end and crystal slurry removed from the other. Cooling medium, often water, is fed through a pipe running through the vessel cooling the slurry which at the same time is mixed by a stirring device or impeller.

The filtration is often performed in a filter press or a membrane filter arranged downstream the crystallizer, where after the components are transported to a specific storage tank or to be used in a further food process or the like. In a typical fractionation process of palm oil, the oil is often heated in a heater before transported to a crystallizer. In the crystallizer stearin crystals are precipitated forming a crystal slurry. The stearin crystals are then filtered out from the slurry leaving a rest of olein. Especially from palm oil as starting material, olein is the main product and the goal is as high yield as possible. While the two products have entirely different properties they may both be usable.

In the crystallization process it is important that the cooling of the oil is performed smoothly and slowly to obtain crystals of good quality and large dimensions. In order to get an even temperature in the vessel a mechanical impeller is often used. This also has negative effects as the impeller tends to break the crystals and prevent them to grow. A mechanical impeller tends also to have a high electricity consumption.

SUMMARY

An object of the present invention is to provide a crystallizer and a fractionation system which reduces the problems mentioned above leading to a higher yield of the desirable end product.

The crystallizer and the fractionation system for achieving the objects above are defined in the appended claims and discussed below.

A crystallizer for edible oils or fats according to the present invention comprises a vessel. Said vessel extends vertically and comprises a top section, an intermediate section and a bottom section. In said vessel a rotor is rotatably arranged around a vertical rotational axis. Said rotor is rotated +/- 90 degrees back and forth by a motor assembly, around a central vertical rotational axis that extends vertically through the vessel. In the rotor a plurality of axially elongated parallel tubes are arranged at a distance from each other. The vessel comprises an inlet at the top of said vessel which inlet is arranged to convey the edible oils or fats into said vessel, and an outlet at the bottom of said vessel which outlet is arranged to convey a crystal slurry, fornned in the vessel from the edible oils or fats, out of said vessel.

The vessel further comprises an inlet pipe arranged to convey a cooling medium into said vessel and rotor, wherein the inlet pipe is connected to first end openings of said parallel tubes at said top section of said vessel for further conveying said cooling medium into said parallel tubes.

Said parallel tubes convey said cooling medium vertically through said vessel. Each of the parallel tubes extends vertically through the vessel six times, starting at said first end opening at said top section of said vessel and ending with a second end opening at the top section of the vessel.

Each of said parallel tubes conveys said cooling medium from said first end opening at said top section of said vessel vertically downwards, through parallel tubes through said intermediate section and to said bottom section of the vessel.

At the bottom section of said vessel, each parallel tube comprises a first 180 degree curvature. After the first 180 degree curvature, each parallel tube extends again through the intermediate section, vertically and parallelly upwards though the intermediate section of the vessel and to the top section of the vessel.

At said top section of the vessel, each parallel tube then comprises a second 180 degree curvature. After the second 180 degree curvature, each parallel tube extends for the third time, vertically and parallelly through said intermediate section of said vessel, downwards to said bottom section of the vessel.

At the bottom section, each parallel tube comprises a third 180 degree curvature. After said third 180 degree curvature, each parallel tube extends vertically and parallelly for the fourth time through the intermediate section, upwards to said top section of said vessel.

At the top section, each parallel tube comprises a forth 180 degree curvature. After said fourth 180 degree curvature, each parallel tube extends vertically and parallelly for the fifth time through the intermediate section, downwards to said bottom section of said vessel.

At the bottom section, each parallel tube comprises a fifth 180 degree curvature. After said fifth 180 degree curvature, each parallel tube extends vertically and parallelly for the sixth time through the intermediate section, upwards to said top section of said vessel ending with said second end opening and connecting to an outlet pipe arranged to convey said cooling medium from said rotor out of the vessel, wherein the outlet pipe in the top section of the vessel.

Said rotating rotor, comprises a motor assembly that rotates said parallel tubes 90 degrees, back and forth, around said vertical rotational axis that extends vertically through the vessel.

By utilizing a rotating rotor, rotating said parallel tubes containing cooling medium an even or a substantially even cooling effect on the edible oils or fats in the vessel may be obtained. Thereby an even crystallization of the edible oils or fats may be obtained. In addition a gentle stirring of the crystal slurry minimises the destruction of large crystals during crystallization.

The rotating rotor may also be associated with a relatively low energy consumption. This may be due to the fact that the rotating rotor does not primarily aim to cause co-rotation of the total volume of edible oils or fats present in the vessel.

The edible oils or fats to be treated in the crystallizer may be liquidized before introduced into the crystallizer, if needed.

The first end openings may be at the lower end of said parallel tubes and said second end openings may be at the upper end of said parallel tubes. That means that the flow of cooling medium from the bottom to the top is directed against the flow of the edible oils or fat which runs from the top to the bottom when introduced into the vessel via the inlet at the top of the vessel.

A baffle arrangement may be attached to the rotor which is arranged to counteract co-rotation of the edible oils or fats.

The rotating rotor brings the crystal slurry in rotation against a certain inertia, i.e. the crystal slurry will rotate in the same direction but with a slower speed. The baffle arrangement gently breaks up this rotation and thus provides gentle stirring of the crystal slurry. Thereby the baffle arrangement may provide a further improvement of the even or substantially cooling effect and/or minimization of the destruction of the large crystals.

The baffle arrangement provides a homogeneous distribution of crystals in the slurry by some of them being pushed to the top and thus introduced into the fresh oils or fats for a better stirring effect and a fast process, which enables better yield.

The baffle arrangement also counteracts solids settling at the bottom of the equipment, and facilitates for the crystals to go to the outlet of the vessel.

The baffle arrangement may comprise down-winding spiral-formed baffle attached to the rotor and winding around the rotational axis.

The baffle arrangement may comprise one or more metal sheets arranged with a distance from each other along the rotational axis (x) and inclined in relation to a horizontal plane.

Said metal sheets may be inclined in different directions in relation to said horizontal plane. The baffle arrangement may comprise a baffle arranged on top of the distributor with an angle horizontally to said distributor The rotor may comprise a distributor, arranged to distribute the cooling medium coming from the inlet pipe into first end openings of each of the parallel tubes.

The distributor provides an even distribution of cooling medium flow to the parallel tubes.

The inlet pipe may be divided in a stationary first part and a rotating second part attached to said rotor. A sealing device may be arranged between the stationary first part and the rotating second part of the inlet pipe .

The outlet pipe may be divided in a stationary first part and a rotating second part attached to said rotor.

A sealing device may be arranged between the stationary first part and the rotating second part of the outlet pipe.

At least one crystallizer according to the above may be comprised in a fractionation system for fractionation of edible oils and fats into components, which then further comprises a filter device for separating crystals from said crystal slurry.

Another aspect of the invention relates to a method for fractionation of edible oils or fats using at least one crystallizer according to anyone of the embodiments described above. Said method comprises the steps of: providing liquid or liquidized edible oils or fats, continuously feeding said provided oils or fats to said inlet at the top of said vessel, cooling said provided oils or fat so that a crystal slurry is formed in said vessel by feeding cooling media to said inlet pipe into said vessel which inlet conveys said cooling media into said first end openings of said parallel tubes comprised by said rotor, continuously withdrawing said crystal slurry from said outlet pipe at the bottom of said vessel connected to said second end openings of said parallel tubes, feeding said crystal slurry into a filter device, separating the crystals from said crystal slurry.

The method may be a method wherein the edible oil is a palm oil.

Examples of other suitable oils and fats may be selected from the non- limiting group of palm kernel oil, coconut oil, tallow, lard, soybean oil, canola or rapeseed oil, cottonseed oil, corn or maize oil, sunflower oil, safflower oil, rice bran oil, olive oil, cocoa butter, sal fats, illipe butter, milk butter, fish oils, groundnut oil, camelia oil, various types of exotic fats and oils, and oil- derivatives such as fatty acid ethyl or methyl esters. Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the appended schematic drawings, in which

Fig. 1 is a schematic view of a fractionation system according to the invention

Fig. 2 is a cross-sectional view of a crystallizer according to the invention. Fig. 3 is a radial cross-sectional view of a rotor of an embodiment of the crystallizer according to fig. 2.

Fig. 4. is a simplified view of one parallel tube of the current invention. Fig. 5 is a radical cross-sectional view of a rotor of an embodiment of the crystallizer according to fig. 2.

Fig. 6. shows a possible embodiment of a baffle of the current invention. Fig. 7. is a radical cross-section of a baffle, according to the embodiment in fig. 7.

Fig. 8. is a radical cross-sectional view of a rotor of a possible

embodiment of the current invention.

DETAILED DESCRIPTION

With reference to Fig. 1 , a fractionation system 1 for edible oils and fats is shown. It may as in the figure comprise a heater 2 for preheating the starting material to a suitable temperature. A typical starting temperature for the fractionation of palm oil may be between 40 and 60° C. There may be different suitable starting temperatures if the starting material is different. Often the edible oils or fats is fed to the heater by a pumping device 3. The pre-heated oils or fats is then lead to a crystallizer 4. There may in some applications be more than one crystallizer in parallel, e.g. to provide the possibility of continuous operation also if service is needed on one of the crystal I izers, or to enhance the capacity of the system. In the crystallizer the edible oils or fats is cooled so that a hard fat or oil component is continuously crystallized creating a crystal slurry, a mix of crystals and liquid content. In palm oil, which is just an example, the crystals comprise mainly palm stearin and the liquid comprises mainly palm olein.

The crystal slurry is then transported to a separating device 5, which e.g. may be a filter press or a membrane filter. The crystal slurry is there separated into a solid crystal component and a liquid component. The crystal component and the liquid component may then be led to separate storage devices or to further processing steps. In fig. 2, a crystallizer 4 is shown which comprises a vertical vessel 6. The vertical vessel 6 comprises a top section 6a, intermediate section 6b and a bottom section 6c. The vessel 6 has an inlet 7 for the starting product of edible oils or fats at the top section 6a and an outlet 8 for the crystal slurry at the bottom section 6c of the vessel 6. In the top section 6a of the vessel 6 is also an inlet pipe 9 for cooling medium and an outlet pipe 10 for the same.

A rotor 1 1 is rotatably arranged in the vessel 6 around a vertical rotational axis (x). The rotor 1 1 comprises a spindle 17 coinciding with the rotational axis (x) which spindle 17 is rotated by an motor assembly 18. A plurality of axial elongated parallel tubes 12 are arranged in the rotor 1 1 . Rotor 1 1 comprises a distributor/collector 13, arranged in the top section 6a of vessel 6. The distributor/collector 13 divides the flow of cooling medium coming from the inlet pipe 9 into first end openings of each of the vertical tubes 12 and collects the flow of cooling medium coming from second end openings of each of the vertical tubes 12 and further out through the outlet pipe 10.

Rotor 1 1 further comprises a bottom support 14, arranged in the bottom section 6c of vessel 6. The bottom support 14 is a mechanical support for parallel tubes 12 of rotor 1 1 .

The parallel tubes 12 are arranged at a distance from each other so that the edible oils or fats may freely flow between them and to ensure an effective and even cooling. Different patterns of the tube arrangement may be used. In the example according to figure 2. 3. and 4., the tubes 12 have been placed evenly over a radial cross-section. Other patterns are possible like a cross- pattern with tubes placed evenly along one diameter or along 2 perpendicular diameters. Then tubes are sweeping over the whole radial cross section when the rotor 1 1 is rotating.

The rotor 1 1 has a baffle arrangement 19 winding down around the rotational axis like a spiral. The baffle arrangement 19 may be a spiral formed baffle of metal sheet with the parallel tubes 12 threaded or drawn through holes in it.

In another embodiment, the baffle arrangement 19 may comprise one or more metal sheets arranged with a distance from each other along the rotational axis (x) and inclined in relation to a horizontal plane. The metal sheets may be inclined in different directions in relation to said horizontal plane.

As an addition to the embodiments above or as an alternative, the baffle arrangement may be a baffle in the form of a metal sheet on top of the bottom support 14 arranged with an angle horizontally to the bottom support 14 in order to convey the crystal slurry, out towards the circumference of the vessel 6, in order to avoid encrustation and deposits, so that said crystal slurry is forced to exit via the slurry outlet 8. Figure 3. is a cross-section of rotor 1 1 , shown by cross-section-line 3a in figure 2. that demonstrates a possible embodiment of distribution of parallel tubes 12 extending through bottom support 14 of rotor 1 1 , within vessel 6, with spindle 17 in the middle. Figure 4, is a schematic view of one parallel pipe 12. The parallel tube

12 comprises five 180 degree curvatures 12i, 12ii, 12iii, 12iv and 12v; and six vertical and parallel tube sections 12a, 12b, 12c, 12d, 12e and 12f, that extend vertically and parallelly through vessel 6 (not shown). The parallel tube 12 conveys the cooling medium arriving to vessel 1 through inlet 9, from first end opening 20, vertically downwards through first vertical and parallel section 12a to bottom section 6c (not shown) of vessel 6. At the bottom section 6c of vessel 6, the parallel tube comprises the first 180 degree curvature 12i. After first curvature 12i, the parallel tube comprises second vertical and parallel section 12b, that extends through the intermediate section 6b (not shown) of vessel 6, vertically and parallelly to the other vertical and parallel sections (12a, 12c, 12d, 12e and 12f) through the intermediate section 6b of vessel 6 to top section 6a (not shown). At the top section 6a, the parallel tube 12 comprises second 180 degree curvature 12ii.

After the second curvature 12ii, the tube 12 comprises a third vertical and parallel section 12c, that extends vertically and parallelly to the other vertical and parallel sections of pipe 12 (12a, 12b, 12d, 12e and 12f) through

intermediate section 6b of vessel 6 , downwards to said bottom section 6a of the vessel 6.

At the bottom section 6c the parallel tube comprises a third 180 degree curvature 12iii. After the third curvature 12iii, the parallel tube extends comprises a forth vertical and parallel section 12d, extending vertically and parallelly with the other vertical and parallel sections of tube 12, through intermediate section 6b, upwards to top section 6a of vessel 6.

At the top section 6a, the parallel tube 12 comprises a forth 180 degree curvature 12iv. After the fourth curvature 12iv the parallel tube comprises the fifth vertical and parallel section 12e, that extends vertically and parallelly with other vertical and parallel sections 12a, 12b, 12c, 12d and 12f through intermediate section 6b, downwards to bottom section 6c of vessel 6.

At the bottom section 6c the parallel tube comprises a fifth 180 degree curvature 12v. After the fifth curvature 12v, the parallel tube comprises the sixth vertical and parallel section 12f, that extends vertically and parallelly with the other parallel and vertical sections 12a, 12b, 12c, 12d and 12e, through the intermediate section 6b, upwards to top section 6a of vessel 6, ending with the second end opening 21 and connecting to an outlet tube arranged to convey said cooling medium from said rotor through outlet pipe 10 (not shown) out of the vessel 6.

Figure 5 is a cross-section of rotor 1 1 , shown by cross-section line 5a in figure 2. The figure demonstrates a possible distribution of parallel tubes 12 and curvatures 12i, 12ii, 12iii, 12iv or 12v, throughout bottom support 14 of rotor 1 1 , within vessel 6, with spindle 17 in the middle. In figure 6. a possible embodiment of a baffle 19 is shown. The baffle 19 is a part of a baffle arrangement, comprising one or more baffles. The baffle 19, is formed in a down-winding spiral or is inclined in relation to a horizontal plane and winds about rotational axis x (not shown). The baffle 19 is attached to rotor 1 1 , and 19 comprises a curvature 30 extending between curvature edges 32, extending along the longitudinal middle of baffle 19. The baffle 19 further comprises multiple holes 31 , arranged throughout the curvature 30, through which parallel tubes 12 (not shown) extend. Figure 7. demonstrates a cross-section of baffle 19, demonstrated by lines 33a and 33b in figure 6. The curvature 30 extends through the longitudinal middle of baffle 19, between curvature edges 32 and comprises holes 31 for parallel tubes 12. Figure 8. is a radical cross-sectional view of a rotor 1 1 within vessel 6, A rotating assembly 40 and 41 , rotate rotor 1 1 +/- 90 degree around the central vertical rotational axis x (not shown) coinciding with spindle 17.

The above described embodiments of the present invention should only be seen as examples. A person skilled in the art realizes that the embodiments discussed can be varied and combined in a number of ways without deviating from the inventive conception.

It should be stressed that a description of details not relevant to the present invention has been omitted and that the figures are just schematic and not drawn according to scale. It should also be said that some of the figures have been more simplified than others. Therefore, some components may be illustrated in one figure but left out on another figure.