CN114616094A

CN114616094A - Pellet extruder with cooling system and method for producing pellets

Info

Publication number: CN114616094A
Application number: CN202080058707.1A
Authority: CN
Inventors: 阿诺德·彼得·西奥多尔·克莱文
Original assignee: Pelletizing Technology Netherlands Ltd
Current assignee: Pelletizing Technology Netherlands Ltd
Priority date: 2019-08-19
Filing date: 2020-08-12
Publication date: 2022-06-10
Also published as: NL2023659B1; EP4017719A1; EP4017719C0; WO2021034188A1; NL2023659A; EP4017719B1

Abstract

A pellet extruder comprising a shaft with a longitudinal axis, said shaft having an end at a roll support side supporting a bearing and a rotating member, wherein the shaft is provided with a cooling channel extending along a longitudinal axis and a cooling duct extending coaxially within the cooling channel, both the cooling channel and the cooling duct being closed at the roll support side, the shaft further comprising at least one bearing cooling channel, the bearing cooling passage has first and second radial portions and a third axial portion extending in an axial direction, the first and second radial portions extending in a radial direction from a roll support side and an upstream position of the cooling channel through the end portion to an outward end position near the bearing, the third axial portion interconnecting the first and second radial portions, and the shaft includes a fluid seal between the outer surface of the cooling duct and the cooling duct wall at an axial position between the axial positions of the first and second radial portions.

Description

Pellet extruder with cooling system and method for producing pellets

Technical Field

The invention relates to a pellet press comprising a roll support shaft with a longitudinal axis, said shaft having a diameter D at the roll support side_EPThe end supporting a bearing roller member rotatable about a shaft, wherein the shaft is provided with a cooling channel having an inner diameter D and a cooling duct_IAnd extends along a longitudinal axis, the cooling duct extending coaxially within the cooling channel and having an outer surface located at a distance from the cooling channel wall, the cooling channel and the cooling duct being closed at the roll support side.

Background

In WO 2016/195484 a pellet press is described with a support shaft and a perforated drum rotatably mounted on the support shaft via a drive member having two spaced bearings. A single roller is disposed on the shaft within the drum. The first bearing of the drive member is a radial bearing and the second bearing of the drive member is an axial-radial bearing arranged at a greater radial distance from the axis of rotation of the drum than the radial bearing. An axially movable locking bushing is placed around the shaft between the axial bearing seat and the axial-radial bearing, the bushing engaging the two housings.

When pellets are made of kneadable material having a high viscosity, the bearings of the pellet extruder generate excessive heat, which may cause the viscosity of the lubricant to become too low to maintain effective lubrication. As a result, the bearings can be damaged and the pellet press needs maintenance. Furthermore, when lubricants become too liquid, they can seep into the drum of the pellet extruder, contaminating the pellets. This is particularly undesirable when the pellets are to be used as animal feed, since contaminated feed needs to be discarded.

Due to the position of the bearings within the pellet extruder and the height of the temperature reached by the bearings, air circulation has proven to be insufficient.

An alternative cooling solution is described in US 6,299,430, in which the shaft of a pellet extruder is provided with cooling medium supply and return passages, providing fluid cooling of the shaft. The heat conduction from the bearing to the cooled shaft results in a reduction in the temperature of the bearing.

Disclosure of Invention

It is an object of the present invention to provide a pellet extruder with more efficient bearing cooling. It is another object of the present invention to provide an improved method for forming particles.

To this end, the pellet press according to the invention is characterized in that the roll support shaft further comprises at least one bearing cooling channel having a first and a second radial portion extending from the roll support side position and from the upstream position of the cooling channel wall, respectively, in the radial direction through the end of the shaft to an outward end position near the bearing, and with a third axial portion extending in the axial direction through the end and interconnecting the first and second radial portions, and that the roll support shaft comprises a fluid seal placed between the outer surface of the cooling channel and the wall of the cooling channel at an axial position between the axial positions of the first and second radial bearing cooling channel portions.

Since the at least one bearing cooling channel extends upwardly to an outward end position close to the surface of the roll support shaft on which the bearing rolling members are supported, the cooling liquid passes through the roll support shaft in close proximity to the bearing. This results in an efficient heat exchange between the lubricated bearings and the cooling liquid, increasing the lubrication effect and reducing the failure of the roller bearing components. In addition, due to the improved cooling capacity, the operating temperature of the other parts of the pellet extruder is reduced, also positively affecting its service life.

By the addition of multiple bearing cooling channels, higher cooling capacity can be achieved, allowing the throughput and/or speed of the pellet extruder to be increased. Preferably, the cooling system is arranged to be able to cool the bearing support shaft from 200 ℃ back to 70 ℃, providing a more comfortable and safe working environment for the operator due to the reduction of heat in the surroundings of the pellet extruder. Advantageously, if the cooling capacity is sufficiently high to keep the temperature of the lubricant in the bearing roller member below 120 ℃, a food grade lubricant can be used, thereby eliminating the risk of contamination of the animal feed produced with the pellet extruder. Furthermore, the increased cooling capacity of the shaft results in a reduction of the power consumption of the pellet extruder, contributing to lower carbon dioxide emissions.

An additional advantage provided by the design of the cooling assembly is that assembly and disassembly of the cooling ducts within the cooling channels can be performed by simply inserting the cooling ducts with the fluid seals from the shaft-mounting side of the roll support shaft opposite the roll support side. Thus, implementation of the fluid seal enables ease of manufacture and maintenance.

The cooling bearing in the vicinity of the bearing cooling channel according to the invention may be a bearing supporting the drive member of the drum or a bearing supporting the rollers within the drum or a bearing supporting both.

According to an embodiment, the roller supporting shaft has a diameter D smaller than the end portion_EPDiameter D of_OThe end portion comprising a cylindrical bearing support surface and an annular, radially directed end surface, wherein the radial bearing cooling channel portion is provided by drilling from the bearing support surface to the cooling channel and the axial bearing cooling channel portion is provided by drilling from the annular end surface in the axial direction.

By drilling the channel portions inwardly from the outer surface of the roll support shaft, the ease of manufacture of the radial bearing cooling channels is improved. Thereafter, if additional cooling capacity is required as a result, additional cooling channels may be added to the roll support shaft as and when required. The manufacturing method also allows retrofitting an existing shaft with a cooling system according to the invention.

According to a further embodiment, the bearing cooling channel portion is closed by a plug member at the bearing support surface and at the radially directed end surface.

The plug member ensures that the cooling system is a closed system separate from the lubrication system. The plug member closes the drilled cooling channel and ensures that cooling water does not mix with the roller lubricant and/or contaminate the kneadable material.

According to an embodiment, the fluid seal comprises at least one O-ring.

When the cooling system is operating, the seal may be relatively thin and flexible, since the pressure on both sides of the seal is equal. This allows the sealing ring to be a simple O-ring.

According to a further embodiment, the shaft is provided at the shaft mounting side with a rotatable coupling comprising connector members for connecting the fluid supply duct and the fluid return duct to the cooling channel and the cooling duct, respectively.

To prevent damage when the rotational force on the shaft becomes excessive, for example because the friction between the roller and a perforated drum mounted on and driven through the shaft exceeds a maximum force, the rotatable coupling allows the shaft itself to rotate as an emergency system when required.

According to an embodiment, the pellet extruder further comprises: a cooling member and a pump connected to the cooling channel and the cooling duct for supplying a cooled cooling fluid to the channel or duct; a temperature sensor for measuring the cooling fluid temperature of the heated return fluid from the cooling passage or cooling conduit; and a controller for controlling the rotational speed of a drive member mounted on the roller supporting shaft by bearings and adapted to rotate the perforated drum supported on the end of the shaft about the longitudinal axis L in dependence on the measured temperature.

The cooling member receives the heated cooling fluid exiting the roll support shaft and cools the fluid back to a predetermined lower cooling temperature before the pump pumps the cooling fluid back into the roll support shaft. Thus, the cooling member and the pump allow for recirculation of the cooling fluid. In a preferred arrangement, the cooling means comprises a heat sink and a fan. This arrangement has the advantage that the hot air released in the heat sink can be directed to a desired location (e.g. outside) via the exhaust stack, thereby allowing a comfortable working temperature to be maintained in the working facility around the pellet extruder.

By the addition of a temperature sensor measuring the heated return liquid, the state of the pellet extruder can be monitored and the controller can adjust the rotational speed of the drum to maintain the temperature at the bearing roller members within an optimum range due to the rotation of the drum. As previously mentioned, there is a risk of damage when the temperature at the bearing roller member is too high, as the lubricant becomes less efficient. When the temperature of the bearing roller member is excessive, the increase in the viscosity of the lubricant becomes excessive, and also adversely affects the effectiveness of the machine. Therefore, in order for the pellet press to maintain optimum operation, the temperature of the bearing roller members needs to be maintained optimum. Feedback is provided to the controller by additional temperature sensors, and the controller automatically adjusts the operating parameters of the pellet extruder to maintain this optimum temperature.

Further, the controller may be adapted to adjust the rotational speed and/or distance between the roller and the drum. Alternatively or additionally to the controller controlling the rotational speed of the drum, the controller may also be connected to the cooling member and/or the pump and adapted to adjust the cooling rate and/or the pumping speed at the operation of the cooling member or the pump in dependence of the measured temperature.

Furthermore, the invention provides a method of forming kneadable material into pellets in a pellet extruder comprising a drum with perforated walls, at least one roll inside the drum, the roll being rotatable about an axis and cooperating with an inner surface of the drum to extrude material through the perforations in the drum walls, and driving means to rotate the axes of the drum and the at least one roll relative to each other about an axis with a drum rotation axis, wherein the axis is configured to adjust a distance between the at least one roll and the inner surface of the drum to control a gap width therebetween, wherein the axis is provided with a cooling channel and a cooling duct, the cooling channel having an inner diameter D₁And extends along the drum rotation axis, the cooling duct extending coaxially within the cooling channel and having an outer surface at a distance from the cooling channel wall, the cooling channel and the cooling duct being closed at the roll support side. The method of forming particles comprises the steps of:

-feeding the material into a drum and kneading the material by rotating the drum at the drum rotation speed,

-forcing the material through the holes in the drum wall with a roller having a roller rotation speed, and

-flowing a cooling fluid through the cooling channels and the cooling ducts to cool the shaft,

characterised in that the method further comprises measuring the cooling fluid temperature of the heated return fluid from the cooling channel or cooling duct and adjusting the drum rotation speed, the roller rotation speed and/or the distance between the roller and the drum in dependence on the measured temperature.

Drawings

Embodiments of a pellet extruder according to the invention will be described by way of example with reference to the accompanying drawings, in which

FIG. 1 shows a cross section of a pellet extruder with cooled drive member bearings according to the present invention;

FIG. 2 shows a detailed view of the shaft in section II of FIG. 1; and

fig. 3 shows a perspective view of the shaft portion of fig. 2.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Fig. 1 shows a pellet press 100 having a roll support shaft 10 with a longitudinal axis L, a shaft mounting side 11 for being supported by a machine frame (not shown) and a roll support side 19 with an end supporting a perforated drum 90, which perforated drum 90 is rotated about the longitudinal axis L via a drive member 48. The drive member 48 is mounted on the support shaft 10 via an axial-radial bearing 20 positioned near the end 19 of the shaft 10 and a radial bearing 21 positioned near the shaft mounting side 11. To provide a rigid structure, the drive member 48 is formed in one piece of cast iron.

At the end 19, a roller 80 is mounted on the support shaft 10 so as to be rotatable about a roller axis R spaced at a distance from the longitudinal axis L. The rollers 80 are driven by frictional engagement between the outer roller surface 81 and the inner drum surface 91 via a kneadable material that is extruded in the gap between the

drums

80 and 90 before being extruded through the perforations of the drums to form the pellets.

Pellet extruder 100 is provided with a cooling system, shown as including internal cooling channels and

conduits

30, 32, 34 in roll support shaft 10, cooling member 42, pump 40, temperature sensor 44, and controller 46. The internal cooling channels and

ducts

30, 32, 34 are connected to the cooling member 42 via a rotatable coupling 15, said rotatable coupling 15 having a connector member 17 for connecting the fluid supply duct 7 and the fluid return duct 8 to the internal cooling channels and

ducts

30, 32, 34, allowing the cooling fluid (e.g. water) to be circulated and reused. The pump 40 is located between the cooling member 42 and the supply conduit and is adapted to pump cooling fluid into the internal cooling passage. A temperature sensor 44 is arranged in the fluid return conduit 8 for measuring the cooling fluid temperature of the heated return fluid from the

internal cooling channels

30, 32, 34. In terms of output, the temperature sensor 44 is connected to a controller 46, said controller 46 being arranged to control the rotational speed of the drive member 48 in relation to the pumping rate of the roller support shaft 10 and the pump 40 in dependence on the measured temperature. The rotatable coupling 15 of the cooling system allows rotation of the roller support shaft 10 within the machine frame relative to the fluid supply conduit 7 and the fluid return conduit 8, which may occur as a safety feature against overload in the event that the friction between the drum 90 and the roller 80 exceeds a predetermined maximum force. With reference to fig. 2 and 3, further details of the internal cooling passages and

ducts

30, 32, 34 within the roll support shaft 10 are discussed.

Referring to fig. 2 and 3, respectively, fig. 2 shows a detailed view and a perspective view of the shaft in section II of fig. 1. The roll support shaft 10 has a main portion 18, said main portion 18 having an outer diameter D at the roll support side 11_OThe outer diameter D_OLarger diameter D from the shaft-mounting side to the end_EP. An annular, radially oriented end surface 24 provides a transition between the main portion 18 and the end at the roll support side 19. The outer surface portion of the end portion immediately adjacent to the annular, radially oriented end surface 24 forms a bearing support surface 22 having a length along the longitudinal axis L long enough to support the bearing roller member 20 for the drive member 48 to be mounted on the support shaft 10.

Internal cooling passages and conduits within the shaft 10 with cooling ducts 32, cooling passages 34, and a plurality of bearing cooling passages 30 are shown in FIG. 2. The

cooling passages

34, 32 have an inner diameter D₁Preferably, the inner diameter D₁Between 40-70mm, the cooling

channels

34, 32 extend within the center of the shaft 10 along the longitudinal axis L from the shaft mounting side 11 towards the roll support side 19, which extends along substantially the entire length of the bearing support surface 22 when viewed along the longitudinal axis L. The cooling duct is coaxial with the cooling channel 34 and is positioned within the cooling channel 34, said cooling duct having an outer surface 31, the outer surface 31 being at a distance (dw) between 5-25mm from the inner wall 33 of the cooling channel 34. The cooling duct 32 has a length that is shorter than the length of the cooling channel 34 and extends from the shaft mounting side 11 to a position through the annular radially oriented end surface 24, viewed along the longitudinal axis L. The cooling channel 34 is closed at the roll support side 19. At the roll support side 19, the cooling duct 32 is provided with an O-ring 36 along its outer circumference, said O-ring 36 sealing the end of the cooling duct 32 to the inner wall 33 of the cooling channel 34, preventing cooling fluid from flowing directly from the cooling channel 32 through the cooling channel 34 to the fluid return channel 8. Thus, the portion 35 of the cooling channel 34 extending over the O-ring 36 and over the end of the cooling duct 32 at the roll support side 19 is closed off from the rest of the cooling channel extending from the shaft mounting side 11 and is connected in an open manner to the end of the cooling duct 32 at the roll support side 19 for distributing the cooling fluid into the plurality of radial ducts 30 b.

At the location of the bearing support surface 22, the roller support shaft 10 is provided with a bearing cooling channel 30 connecting the portion 35 to an upstream portion of the cooling channel 34, forming a flow path for cooling fluid by the cooling system. In this flow path, the end of the cooling duct 32 at the roller bearing side 19 is upstream of the end of the cooling duct 32 at the shaft mounting side 11, and the end of the cooling passage 34 at the shaft mounting side 11 is upstream of the end of the cooling passage 34 at the roller supporting side 19.

Each bearing cooling passage 30 has a first portion 30a, a second portion 30b and a third portion 30 c. The first portion 30a and the second portion 30b are radial portions each extending radially outward from a position in the cooling passage wall 33 toward an end position lower than the bearing support surface 22. The first portion 30a extends outwardly from the portion 35 and forms a spray head by having a plurality of radial openings. The second portion 30b extends outward from a position adjacent to the O-ring 36 on a side facing the upstream end of the cooling passage 34. The third portion 30c of each bearing cooling passage 30 extends in the axial direction through the end on the roll support side, connecting the end positions of the first portion 30a and the second radial portion 30b to each other. Preferably, the end positions of the first and

second portions

30a, 30b are between 5 and 50mm from the bearing support surface 22. For ease of manufacture, the first and

second portions

30a, 30b are drilled radially inward into the cooling passage wall 33 from the bearing support surface 22, and the third portion 30c is drilled from the annular, radially oriented end surface 24 through an end location of the second radial portion 30b and into the first radial portion 30 a. To ensure the closure of the cooling system in the shaft and to prevent contamination of the bearing lubricant and kneadable material in the perforated drum 90, the resulting bore holes in the bearing support surface 22 and the annular, radially oriented end surface 24 are closed with plugs 38.

The roller 80 depicted in fig. 1 also includes bearings that can be similarly cooled by extending the cooling system described above.

The invention has been described above with reference to a number of exemplary embodiments shown in the drawings. Modifications and alternative implementations of some parts or elements are possible and are included in the scope of protection defined in the appended claims.

Claims

1. A pellet press (100) comprising a roll support shaft (10) with a longitudinal axis (L), said shaft (10) having a support bearing (20) on a roll support side (12) and a diameter D supporting a rotary member (48) rotatable about said shaft (10)_EPWherein the shaft (10) is provided with a cooling channel (32) and a cooling duct (34), the cooling channel (32) having an inner diameter D₁And extends along the longitudinal axis (L), in which the cooling duct (34) is locatedA channel (32) extending coaxially within and having an outer surface (33) at a distance (dw) from a cooling channel wall (31), the cooling channel (32) and the cooling duct (34) being closed at the roll support side (12),

characterized in that the roll support shaft (10) further comprises at least one bearing cooling channel (30), the bearing cooling channel (30) having first and second radial portions (30a, 30b) and a third axial portion (30c), the first and second radial portions (30a, 30b) extending from a roll support side position and from an upstream position of the cooling channel wall (31), respectively, through an end of the shaft (10) in a radial direction to an outward end position near the bearing (20), the third axial portion (30c) extending through the end in the axial direction and interconnecting the first and second radial portions (30a, 30b), and

a fluid seal (36), the fluid seal (36) being placed between an outer surface of the cooling duct (33) and a wall of the cooling channel (31) at an axial position between axial positions of the first and second radial bearing cooling channel portions (30a, 30 b).

2. Pellet extruder (100) according to claim 1, wherein the roller support shaft (10) has a main portion (18), the diameter D of the main portion (18)_OSmaller than the diameter D of the end portion_EP-the end portion comprising a cylindrical bearing support surface (22) and an annular, radially oriented end surface (24), wherein the radial bearing cooling channel portion (30a, 30b) is arranged to be drilled by drilling from the bearing support surface (22) towards the cooling channel (32), and the axial bearing cooling channel portion (30c) is arranged to be drilled by drilling in an axial direction from the annular end surface (24).

3. The pellet extruder (100) of claim 1 or 2, wherein said bearing cooling channel portion (30a, 30b, 30c) is closed by a plug member (38) at said bearing support surface (22) and at said radially oriented end surface (24).

4. The pellet extruder (100) of any one of the preceding claims, wherein said fluid seal (36) comprises at least one O-ring.

5. Extruder (100) for pellets according to any one of the preceding claims, the shaft (10) being provided with a rotatable coupling (15) at a shaft mounting side (11), the rotatable coupling (15) comprising connector members (17) for connecting a fluid supply duct (7) and a fluid return duct (8) to the cooling channel (32) and the cooling duct (34), respectively.

6. The pellet extruder (100) of any one of the preceding claims, further comprising:

a cooling member (42) and a pump (40), the cooling member (42) and the pump (40) being connected to the cooling channel (32) and the cooling duct (34) for supplying cooled cooling fluid to the channel or duct,

a temperature sensor (44), the temperature sensor (44) for measuring a cooling fluid temperature of the heated return fluid from the cooling channel (32) or cooling conduit (34), an

A controller (46), said controller (46) for controlling the rotational speed of a driving member mounted on said roller supporting shaft via said bearing (20) and adapted to rotate a perforated drum (90) supported on said end of said shaft (10) about said longitudinal axis (L) according to the measured temperature.

7. A method of forming kneadable material into pellets in a pellet extruder (100) comprising a drum (90) with perforated walls, at least one roll (80) inside the drum (90) rotatable about an axis (R) and cooperating with the inner surface of the drum (91), the extruded material passing through the perforations in the drum walls, and driving means rotating the axis of the at least one roll (80) and the drum (90) relative to each other about a shaft (10) with a drum rotation axis (L), wherein the shaft (10)Is configured to adjust a distance (dr) between the at least one roller (80) and an inner surface of the drum (91) to control a gap width therebetween, and wherein the shaft (10) is provided with a cooling channel (32) and a cooling duct (34), the cooling channel (32) having an inner diameter D₁And extending along the drum rotation axis (L), a cooling duct (34) extending coaxially within the cooling channel (32) and having an outer surface (33), the outer surface (33) being located at a distance (dw) from the cooling channel wall (31), the cooling channel (32) and the cooling duct (34) being closed at the roll support side (12), the method of forming particles comprising the steps of:

-feeding the material into the drum (90) and kneading the material by rotating the drum at a drum rotation speed,

-forcing the material through the holes in the drum wall with a roller (80), the roller (80) having a roller rotation speed, and

-flowing a cooling fluid through the cooling channel (32) and the cooling duct (34) to cool the shaft (10),

characterized in that the method further comprises measuring the cooling fluid temperature of the heated return fluid from the cooling channel (32) or cooling duct (34) and adjusting the drum rotation speed, the roller rotation speed and/or the distance (dr) between the roller (80) and the drum (90) in dependence on the measured temperature.