WO2018137744A1

WO2018137744A1 - Nozzle for an extruder

Info

Publication number: WO2018137744A1
Application number: PCT/DK2018/050015
Authority: WO
Inventors: Markus Wied DETHLEFSEN; Niels HJERMITSLEV
Original assignee: Biomar Group A/S
Priority date: 2017-01-27
Filing date: 2018-01-26
Publication date: 2018-08-02
Also published as: EP3573483A1

Abstract

The present invention provides a nozzle for extruding a food or feed substance into a corresponding food or feed extrudate. The nozzle comprises an outlet section having one or more inlet ports for receiving the substance, and one or more outlet ports for providing the extrudate, the outlet section comprising, considered in a downstream direction of the nozzle, a first section having a first minimum flow area, the first section being immediately followed by a second section having a second minimum flow area which is lower than the first minimum flow area, the second section being immediately followed by a third section having a third minimum flow area which is higher than the second minimum flow area, the third section being immediately followed by a fourth section having a fourth minimum flow area which is lower than the third minimum flow area, a downstream end of the fourth section forming the one or more outlet ports, an upstream end of the first section forming the one or more inlet ports, a highest flow area in the outlet section being at most 10 times a flow area of the one or more outlet ports.

Description

Nozzle for an extruder Technical field

This invention relates to a nozzle for an extruder. Background of the invention Feed for fish is often made as an extrudate of a dough-like substance. A reason for making feed this way is that fish feed is frequently coated with oil in order to provide a higher- energy diet. The feed is made in such a way that it contains pockets that can hold the oil. It is currently an important concern that oil leaks out of the extrudate during feed

transportation, feed storage, and generally handling of the feed product, resulting in customer complaints.

Other food and feed products also suffer damage from transportation and handling, where physical impact causes the product to break into smaller pieces, again giving rise to customer dissatisfaction.

Summary of the invention Embodiments of the present invention are able to mitigate one or more of the issues described above.

In a first aspect, the present invention provides a nozzle for extruding a food or feed substance into a corresponding food or feed extrudate. The nozzle comprises: an outlet section having one or more inlet ports for receiving the substance, and one or more outlet ports for providing the extrudate, the outlet section comprising, considered in a downstream direction of the nozzle, a first section having a first minimum flow area, the first section being immediately followed by a second section having a second minimum flow area which is lower than the first minimum flow area.

Preferably, the second section being immediately followed by a third section having a third minimum flow area which is higher than the second minimum flow area, the third section being immediately followed by a fourth section having a fourth minimum flow area which is lower than the third minimum flow area, a downstream end of the fourth section forming the one or more outlet ports, an upstream end of the first section forming the one or more inlet ports, a highest flow area in the outlet section being at most 10 times a flow area of the one or more outlet ports.

Without being bound by theory, at least some embodiments of the invention may be able to produce a turbulent or turbulent-like flow by the product passing through the nozzle. This is belived to produce an extrudate of desired quality. By turbulent or turbulent-like flow may be considered a flow turning and/or twisting including but not limited thereto a flow exhibiting fluctuations over time and/or space.

Preferred embodiments of the nozzle have, seen in a downstream direction, a narrowing followed by a widening followed by a narrowing. The inventors realized that such a change in flow area causes bubbles formed in the substance during extrudate manufacturing to break into smaller bubbles due in part to a change in apparent viscosity of the substance in the different sections and in part due to an urging of the substance both by the restrictions in flow area going from wider to narrower sections, i.e. from the first section to the second section and from the third section to the fourth section, and from the widening in flow area, i.e. from the second section to the wider third section. The latter causes increased formation of bubbles and at the same time a shearing of the bubbles, causing the newly formed bubbles to break up. This increases the mechanical strength of the extrudate product substantially compared to products obtained with existing methods. This results in less degradation of the product during handling. Furthermore, in case oil has been added, the average oil leakage is substantially reduced.

In a cylindrical pipe, "flow area" is simply the area of the pipe's opening at a cross-section normal to the pipe's axis. A similar definition is readily applicable for a rectangular pipe (also not within the scope of the invention). For more complex pipe shapes, the flow area at a given point is determined as the cross-sectional area of the opening of the pipe normal to the average flow direction. This definition applies also to the inlet port(s) and outlet port(s). As an example pertaining to a cylindrical pipe, the flow area of for instance two outlet ports is the sum of the flow areas of the individual outlet ports. The same also applies along the length of the outlet section. In other words, if the outlet section has more than one flow channel, i.e. is split into two or more streams during at least a part of the outlet section, the flow area is the sum of the flow areas of the individual flow channels. In the claims, "flow area" shall therefore be construed as such a sum.

In preferred embodiments, a highest flow area in the outlet section is at most 10 times the flow area of the one or more outlet ports. It was observed that beyond the value 10, the efficiency of the mechanisms described above was significantly reduced. The reason is, at least partly, that if the flow area is very large relative to the flow area of the one or more outlet ports, the flow behaviour becomes substantially more linear, relatively, which allows a large portion of the bubbles to remain intact. In some embodiments, the highest flow area of the outlet section is at most 5 times the flow area of the one or more outlet ports, such as at most 3 times, such as at most 1.2 times.

The terms food and feed substance cover any edible substance, such as a food for humans or animals, such as animal feeds. A food substance may consist of a single product, or it may be a combination of several ingredients. The ratios between minimum flow areas in the different sections also affect the product. The mechanisms described above are not as effective if the minimum flow area in one section is too similar to that of the immediately following section. Preferably, a ratio between the minimum flow area of the first section and the minimum flow area of the second section is at least 1.05. Alternatively, or additionally, a ratio between the minimum flow area of the third section and the minimum flow area of the fourth section is at least 1.05. Further alternatively or additionally, a ratio between the minimum flow area of the third section and the minimum flow area of the second section is at least 1.05.

Preferably, these are all satisfied, i.e. a ratio between the minimum flow area of the first section and the minimum flow area of the second section is at least 1.05, and a ratio between the minimum flow area of the third section and the minimum flow area of the fourth section is at least 1.05, and a ratio between the minimum flow area of the third section and the minimum flow area of the second section is at least 1.05. In some embodiments, at least one of these ratios is at least 1.1, such as at least 1.5, such as at least 2, such as at least 3, such as at least 4, such as at least 5, such as at least 8.

The process of the bubbles breaking into smaller bubbles can be further enhanced by introducing restriction elements that urge a substantial local change in a flow of a part of the substance. In some embodiments, the nozzle therefore comprises one or more urging elements that extend from an inside surface of the second section and forms an angle of at least 30 degrees with respect to an average flow direction of the outlet section. The average flow direction is simply a direction from the center of mass of the substance at the inlet (defined by the one or more inlet ports) to the center of mass of the substance at the outlet (defined by the one or more outlet ports).

In some embodiments, the second section comprises one or more urging elements, wherein at least one of the one or more urging elements comprising an urging element surface part having a local tangent that forms an angle of at least 30 degrees with respect to the average flow direction of the outlet section.

In some embodiments, the second section comprises at least two urging elements each having an urging element surface part having a local tangent that forms an angle of at least 30 degrees with respect to the average flow direction of the outlet section. In some embodiments, two of the urging elements are located at different downstream positions in the second section and they extend in mutually different directions, such as in opposite directions to urge the substance in one direction at one point along the outlet section and subsequently in the opposite direction, or at least in a different direction. In some embodiments, the nozzle consists of at least two separate mutually engageable parts which, when engaged with one another, form the outlet section. This allows parts that are more susceptible to being worn down to more easily be replaced. In some

embodiments, a first part of the at least two engageable parts is a die plate comprising the one or more outlet ports. In such embodiments, the die plate is usually hardly worn by the extrusion process, whereas another of the at least two engageable parts is worn much more quickly and is relatively easily replaced when needed.

In some embodiments, a first of the at least two engageable parts comprises a neck, and a second part of the at least two engageable parts comprises an aperture for receiving and holding the neck of the first part under a downstream pressure from the substance during extrusion.

In some embodiments, the outlet section comprises two or more outlet ports. In some embodiments, at least two of the two or more outlet ports are in fluid communication with a common inlet port of the outlet section.

In some embodiments, a flow path from one of the one or more inlet ports to one of the one or more outlet ports has a length of at least 5 mm. In some embodiments, this flow path length is at least 10 mm, such as at least 20 mm, such as at least 50 mm, such as at least 100 mm. A shorter length is typically used for smaller extrudates, whereas larger extrudates obtain better properties with longer outlet sections.

In some embodiments, a flow path from one of the one or more inlet ports to one of the one or more outlet ports has a length of at most 200 cm, such as at most 150 cm, such as at most 100 cm. In a second aspect, the invention provides an extrusion process for producing a food or feed extrudate from a food or feed substance. The extrusion process differs from existing extrusion methods at least in that it comprises a step of forcing the substance through a nozzle embodiment in accordance with the first aspect of the invention. In some embodiments, process conditions are such that a ratio between a volumetric mass density of the substance and a volumetric mass density of the extrudate is between 1.3 and 30.

In some embodiments, a temperature of the substance in the outlet section reaches at least 100 degrees C and a pressure of more than 1 bar. The high temperature causes water in the mixture to be above boiling temperature. However, a substantial part of the water remains in the liquid state. Near the nozzle outlet section the water content transitions to mainly the vapour state. In some embodiments, a temperature of the substance at the one or more inlet ports is above 105 degrees C.

Typically, the food or feed substance has a protein-to-carbohydrate content ratio, by weight, of at least 2.5, such as at least 5, such as at least 8, such as at least 10.

Brief descriptions of the drawings

Figure 1 schematically illustrates an example of a prior-art extruder in use.

Figure 2 illustrates an extruder nozzle in accordance with prior art.

Figure 3a illustrates a cross-section of a nozzle in accordance with an embodiment of the present invention with indications of the first through fourth outlet sections, and

corresponding minimum flow areas.

Figure 3b illustrates the cross-section also shown in Figure 3a, but with an alternative splitting into first through fourth outlet sections compared to Figure 3a. The corresponding minimum flow areas are also illustrated. Figure 4 illustrates a top view of a nozzle having the cross-section shown in Figure 3a.

Figure 5 illustrates a perspective view of the nozzle shown in Figure 4.

Figure 6 illustrates a perspective view of an embodiment of a nozzle comprising two mutually engageable parts. Figure 7 illustrates a cross-section of the nozzle shown in Figure 6.

Figure 8 illustrates a cross-section of another nozzle in accordance with an embodiment of the present invention, with indications of the first through fourth outlet sections.

Figure 9 illustrates a perspective view of the nozzle in Figure 8. Figure 10 illustrates a top view of the nozzle in Figure 8.

Figure 11 illustrates a die plate for receiving a nozzle in accordance with an embodiment of the invention.

Figure 12 illustrates a cross-section of the die plate in Figure 11, in which a nozzle has been inserted. Figure 13 illustrates a cross-section of a nozzle in accordance with an embodiment of the invention; a die plate is part of the nozzle.

Figure 14 illustrates three views of a nozzle in accordance with an embodiment of the invention; the nozzle has urging elements in the shape of a riffling.

Figure 15 illustrates two nozzle each shown in three views in accordance with two embodiments of the invention; the nozzles have urging elements in the shape of abrupted rifflings.

Figure 16 illustrates three views of a nozzle in accordance with an embodiment of the invention, the nozzle has urging elements in the form of helicoid elements.

Figure 17 illustrates three views of a nozzle in accordance with an embodiment the invention, the nozzle has urging elements in the form of wedge shaped elements.

Figure 18 illustrates three views of a nozzle in accordance with an embodiment the invention, the nozzle has an urging element in the form of wedge shaped element tapering upstream. Detailed description of selected embodiments

The invention will now be exemplified with reference to the accompanying drawings.

Reference signs in this specification, including the claims, are not to be construed as limiting the scope of the invention. The drawings are not necessarily drawn to scale. Fig. 1 illustrates an example of a prior-art extruder 100. The extruder comprises a hopper 101 for receiving ingredients 102 to be mixed and subsequently extruded into an extrudate 113. The hopper feeds the ingredients into a first mixer section 103 in a barrel 105. The mixer section mixes the ingredients to provide a more or less homogeneous mixture. The mixer section 103 is followed in a downstream direction by a die 107. When the mixture is pressed against the die, the mixture is forced to take on the shape of the opening(s) 109 of the die.

Fig. 2 illustrates the die 107, which is essentially simply a plate 108 with holes 109.

Fig. 3a illustrates a cross-section A-A of a nozzle 300 in accordance with an embodiment of the present invention with indications of a division of the outlet section into first through fourth sections 301a, 302, 303, 304, having corresponding minimum flow areas 321a, 322, 323, 324. The white areas in drawing elements 321a, 322, 323, 324 are openings, whereas hatched areas are restrictions which cause a local reduction in the flow area . The nozzle 300 also has one inlet port 310a and three outlet ports 311 (due to the cross-section, only one outlet port is visible).

The minimum flow area 321a of the first section 301a is larger than the minimum flow area 322 of the second outlet section 302. Furthermore, the minimum flow area 323 of the third outlet section 303 is larger than the minimum flow area 322 of the second section 302. Furthermore, the minimum flow area 324 of the fourth section 304 is smaller than the minimum flow area 323 of the third section 303. Furthermore, a highest flow area of the outlet section is, in this division into first through fourth sections, equal to the flow area of the first section, i.e. the minimum flow area 321a. This flow area is approximately a factor of 4.8 times the total area of the three outlet ports.

The minimum flow area 322 of the second section 302 is smaller than the minimum flow area 321a of the first section 301a due to urging element 315, which narrows the flow channel.

Since the nozzle 300 has these properties, it falls within the scope of the invention as defined by the claims.

In the embodiment 300 in Fig. 3a, the second section 302 has three urging elements 315, 316, 317. These cause the breaking of larger bubbles into smaller bubbles to be particularly effective. Being arranged alternatingly on opposite one another improves the breaking up of bubbles further. The increase in flow area in the third section 303 gives an increase in apparent viscosity in some parts, and the increase in flow area also causes an increase in formation of bubbles and at the same time a shearing of the bubbles, causing the newly formed bubbles to break up. This improves the mechanical strength of the final food or feed product.

Fig. 3a also illustrates an optional neck 320. The neck may be used to maintain the nozzle in a die plate under a pressure from a downstream flow of food or feed substance.

Fig. 3b illustrates an alternative division of the outlet section into first through fourth sections, namely as consisting of sections 301b, 302, 303, 304 rather than 301a, 302, 303, 304 as shown in Fig. 3a. As such, only the minimum flow area 321b is different.

The minimum flow area 321b of the first section 301b is larger than the minimum flow area 322 of the second outlet section 302. Furthermore, the minimum flow area 323 of the third outlet section 303 is larger than the minimum flow area 322 of the second section 302. Furthermore, the minimum flow area 324 of the fourth section 304 is smaller than the minimum flow area 323 of the third section 303. Furthermore, a highest flow area of the outlet section is, in this division into first through fourth sections, equal to the flow area at the inlet port 310b, i.e. at the beginning (left side in Fig. 3b) of the first section. In the nozzle 300 this flow area happens to have the same size as the flow area 323 of the third section. The highest flow area of the outlet section is approximately a factor of 2.9 times the total area of the three outlet ports.

The description related to Fig. 3b is another way to determine that the nozzle 300 falls within the scope of the invention as defined by the claims.

A simple, cylindrical flow channel does not fall within the scope of the claims because it is not possible to define first through fourth sections having the characterizing features of the claims. A narrowing cylindrical flow channel also does not have those characterizing features. In Fig. 3a, the urging elements 315, 316, 317 form an angle, , of approximately 50 degrees with respect to the average flow direction (which is illustrated by the dotted arrow 360). The high angle forces a large change in flow direction of part of the substance, which causes an increased breaking of bubbles in that part of the substance, increasing the mechanical stability of the final product. As described, this angle (which is a tangent to a part of the urging element's surface) is preferably at least 30 degrees. Fig. 4 illustrates a top view (upstream end) of a nozzle that has the cross-section A-A shown in Figs. 3a and 3b. It has three flow channels, each ending in a corresponding outlet port.

Fig. 5 illustrates a perspective view of the nozzle in Fig. 4. Fig. 5 also illustrates the neck 320 for maintaining the nozzle in a die plate under a pressure from a downstream flow of food or feed substance.

Fig. 6 illustrates a nozzle 600 similar to that in Fig. 5. The second section comprises similar urging elements 615, 616 and 617, shown in the cross-sectional view in Fig. 7. In this embodiment, the nozzle comprises two mutually engageable parts 601, 602. This is convenient because the urging elements 315, 316, 317 (and correspondingly 615, 616, 617 in the present embodiment) are subject to more wear. Making the nozzle from two parts allows for instance for replacing the more quickly worn parts, including the second section containing the urging elements.

Fig. 8 illustrates a cross-section C-C of another nozzle 800 in accordance with an

embodiment of the invention. The first section 801 is provided as a recess in the nozzle 800. The recess also forms the inlet port 810. The second section 802 comprises openings 830 that provide a reduced minimum flow area in that section. The urging part 815 provides a reduced flow area for the substance to pass through. In this example, a surface of the urging part 815 forms an angle of 90 degrees with respect to the average flow direction. Part of the substance is forced to change direction in order to pass through the openings 830. This causes the desired breaking up of bubbles in the substance. The openings 830 connect to a third section 803 having a larger minimum flow area compared to the minimum flow area of the second section 802. The third section is followed by a fourth section 804. (Note that the flow area in the second section 802 is the total of the flow areas of the individual openings 830.) Again, the increase in flow area causes an increase in apparent viscosity in some parts, and it also leads to an increase in bubble formation and subsequent breaking up of bubbles.

The outlet port 811 provides the extrudate. The nozzle 800 in this example also has a neck 820 similar to the neck 320 of nozzle 300 shown in Fig. 5. Fig. 9 illustrates a perspective view of a nozzle that has the cross-section C-C shown in Fig. 8. It shows the urging part 815 with the openings 830 through which the substance is forced under a pressure for instance from a static mixer.

Fig. 10 illustrates a top view (upstream end) of the nozzle shown in Fig. 9. Fig. 11 illustrates a die plate 1100 comprising a die plate structure 1104 having apertures 1102 for receiving a nozzle in accordance with an embodiment of the invention, in particular a nozzle having a neck. Fig. 11 also illustrates a cross-section B-B of the die plate. At the end of each aperture is a narrowing 1103 for maintaining such a nozzle in the die plate under a downstream pressure. A neck such as 320 in the nozzle 300 in Figs. 3a-5 fits in the narrowing 1103. The nozzle is held in the die plate due to the wider part upstream of the neck.

Holes 1106 are included for attaching the die plate at the end of a food or feed substance provider, for instance at the end of a static mixer. The substance will usually be provided at, or at least near, the center of the die plate. A protrusion 1105, for instance cone-shaped, ensures that the substance is pushed towards the apertures, preventing substance from collecting near the middle of the die plate.

Fig. 12 illustrates the cross-section B-B from Fig. 11, but with a nozzle 1211 inserted in one of the apertures 1102. The nozzle may for instance be a nozzle such as nozzle 300 in Figs. 3a-5 or nozzle 600 shown in Fig. 6 or nozzle 800 shown in Figs. 8-10. Fig. 12 also illustrates a nozzle 1212 similar to nozzle 1211 under insertion into an aperture 1102.

Fig. 13 shows a cross-section of a nozzle 1300 in accordance with another embodiment of the invention. In this embodiment, a die plate structure 1302, similar to die plate structure 1104 in Fig. 11, is part of the nozzle 1300. The nozzle is shown with an engageable part 1306 inserted into an aperture identical to element 1350. A cross-section of a part 1305 engageable with the die plate structure 1302 is shown about to be inserted into the aperture 1350. In this embodiment, the die plate structure 1302 comprises the outlet port 1311 from which the substance will emerge as extrudate. Enlargement of the detail "D" in Fig. 13 illustrates the two parts 1306 and 1302 in more detail. Part 1306 comprises the first, second and third sections, and the die plate structure together with an end of part

1306 forms the fourth section 1307 of the nozzle. The upstream opening in part 1306 forms the inlet port 1310 of the nozzle, and the opposite side of the die plate structure 1302 defines the outlet port 1311. Similar to the die plate structure in Fig. 11, the die plate structure may comprise multiple outlet ports, for instance arranged concentrically, or at least substantially concentrically.

Figure 14 illustrates three views of a nozzle in accordance with an embodiment of the invention; the nozzle has urging elements in the shape of one or more riff lings. In the illustrated embodiment, the first section 1401 and the second section 1402 each

comprising urging elements each in the shape of a riffling 1411, 1412, 1413, such as in the shape of one or more spiralling elements, the spiral direction being different and changes spiralling direction in a lowest flow area of the nozzle.

Figure 15 illustrates two nozzles each shown in three views in accordance with two embodiments of the invention; the nozzles have urging elements in the shape of abrupted rifflings 1521, 1522, 1523 (upper part of fig. 15) 1531, 1532 and 1533 lower part of fig. 15. The second section 1502 (upper part of fig. 15) is illustrated as being smooth in the sense that no urging elements are present in the second section. However, urging elements may be arranged in the second section, e.g. in order to provide a specific shape of the extrudate. 1501 and 1511 refer to first sections; 1502 and 1512 refers to second sections.

Figure 16 illustrates three views of a nozzle in accordance with an embodiment of the invention, the nozzle has urging elements in the form of helicoid each having a leading edge 1611, 1613, and a trailing edge 1613, 1614. In the embodiment shown, the first section 1601 comprising two urging elements each in the shape of a helicoid element. 1602 refers to second section.

Figure 17 illustrates three views of a nozzle in accordance with an embodiment the invention, the nozzle has urging elements in the form of wedge shaped elements 1711, 1712, 1713. In the embodiment shown, the first section 1701 comprises three urging elements in the shape of wedge elements 1711, 1712, 1713 tapering in a narrowing fashion in the downstream direction and extending centrally and across the width of first section. However, one or both of the downstream urging elements may be left out in some embodiments. And, the wedged shaped elements may be arranged with the tapering in the upstream direction. 1702 refers to second section.

Figure 18 illustrates three views of a nozzle in accordance with an embodiment the invention, the nozzle has an urging element in the form of wedge shaped element 1811 tapering in a narrowing fashion upstream. Instead of a wedge shaped elements, the elements may be provided a semi-reactangular cross section with the side facing upstream or downstream may have rounded edges. Such cross sections may also be applied to the urging elements shown in figure 17. More than one wedge shaped elements may be applied as disclosed in 17. 1801 refers to first section and 1802 refers to second section. In the figures 14-18, a nozzle is illustrated as follows: left: side view; middle: end view (towards the first sections), right: cross sectional side view (figures 14, 17), 3 dimensional view (figures 15, 16, 18). Dotted lines in these figures indicate contour lines (phantom lines).

Dimensions indicated in the figures are not to be construed limiting for the scope of the present invention.

Claims

1. A nozzle (300, 600, 800, 1300) for extruding a food or feed substance into a

corresponding food or feed extrudate, comprising :

- an outlet section having one or more inlet ports (310a, 310b, 810, 1310) for receiving the substance, and one or more outlet ports (311, 811, 1311) for providing the extrudate, the outlet section comprising, considered in a downstream direction of the nozzle, a first section (301a, 301b, 801) having a first minimum flow area (321a, 321b), the first section (301a, 301b, 801) being immediately followed by a second section (302, 802) having a second minimum flow area (322) which is lower than the first minimum flow area (321a, 321b).

2. A nozzle in accordance with claim 1, wherein the second section being immediately followed by a third section (303, 803) having a third minimum flow area (323) which is higher than the second minimum flow area (322), the third section being immediately followed by a fourth section (304, 804) having a fourth minimum flow area (324) which is lower than the third minimum flow area (323), a downstream end of the fourth section (304, 804) forming the one or more outlet ports (311, 811, 1311), an upstream end of the first section forming the one or more inlet ports (310a, 310b, 810, 1310), a highest flow area in the outlet section being at most 10 times a flow area of the one or more outlet ports (311, 811, 1311).

3. A nozzle in accordance with claim 1 or 2, wherein the highest flow area of the outlet section is at most 5 times the flow area of the one or more outlet ports, such as at most 3 times, such as at most 1.2 times.

4. A nozzle in accordance with claim 2 or 3, wherein :

a ratio between the minimum flow area (321a, 321b) of the first section (301a, 301b) and the minimum flow area (322) of the second section (302) is at least 1.05, and/or

- a ratio between the minimum flow area (323) of the third section (303) and the minimum flow area (324) of the fourth section (304) is at least 1.05, and/or a ratio between the minimum flow area (323) of the third section (303) and the minimum flow area (322) of the second section (302) is at least 1.05.

5. A nozzle in accordance with one of the preceding claims, wherein the second section (302, 802) comprises one or more urging elements (315, 316, 317, 815), at least one of the one or more urging elements comprising an urging element surface part having a local tangent that forms an angle, a, of at least 30 degrees with respect to an average flow direction (360) of the outlet section.

6. A nozzle in accordance with one of the claim 1-4, wherein the second section (302) comprising at least two urging element (315, 316, 317), wherein two of the urging elements are located at different downstream positions in the second section and they extend in mutually different directions, such as in opposite directions to urge the substance in one direction at one point along the outlet section and subsequently in the opposite direction, or at least in a different direction.

7. A nozzle in accordance with one of claims 1-4, wherein the second section (302) comprises at least two urging elements (315, 316, 317) each having an urging element surface part having a local tangent that forms an angle, , of at least 30 degrees with respect to an average flow direction (360) of the outlet section.

8. A nozzle in accordance with one of the preceding claims 1-4, wherein first section (1401) and second sections (1402) each comprising urging elements each in the shape of a riffling (1411, 1412, 1413), such as in the shape of one or more spiralling elements.

9. A nozzle in accordance with one of the preceding claims 1-4, wherein first section (1601) comprising one or more urging element in the shape of a helicoid element.

10. A nozzle in accordance with one or more of the preceding claims 1-4, wherein the first section (1701) comprising one or more urging elements in the shape of wedge shaped elements 1711, 1712, 1713, 1811) tapering in the downstream or upstream direction and extending centrally and across the width of first second section.

11. A nozzle in accordance with one of the preceding claims, wherein the outlet section consists of at least two separate mutually engageable parts (601, 602, 1305, 1302, 1212, 1104) which, when engaged with one another, form the outlet section.

12. A nozzle in accordance with claim 11, wherein a first part of the at least two engageable parts is a die plate (1302) comprising the one or more outlet ports (1311).

13. A nozzle in accordance with claim 11, wherein a first part of the at least two engageable parts comprises a neck (320, 820), and a second part of the at least two engageable parts comprises an aperture (1102) for receiving and holding the neck of the first part under a downstream pressure from the substance.

14. A nozzle in accordance with one of the preceding claims, wherein the outlet section comprises two or more outlet ports.

15. A nozzle in accordance with claim 14, wherein at least two of the two or more outlet ports are in fluid communication with a common inlet port of the outlet section.

16. A nozzle in accordance with one of the preceding claims, wherein a flow path from one of the one or more inlet ports to one of the one or more outlet ports has a length of at least 5 mm.

17. A nozzle in accordance with one of the preceding claims, wherein a flow path from one of the one or more inlet ports to one of the one or more outlet ports has a length of at most

200 cm.

18. An extrusion process for producing a food or feed extrudate from a food or feed substance, the process being characterized by a step of:

- forcing the substance through a nozzle in accordance with one of claims 1-17, whereby the extrudate is formed at the one or more outlet ports of the nozzle.

19. A process in accordance with claim 18, wherein a ratio between a volumetric mass density of the substance and a volumetric mass density of the extrudate is between 1.3 and 30.

20. A process in accordance with claim 18 or 19, wherein a temperature of the substance at the one or more inlet ports is above 100 degrees C.