Method of granulation

Abstract

A method of pelletizing, comprising the steps of: providing a hollow body arranged to rotate around a first axis of rotation, the hollow body comprising a wall rotationally arranged symmetrically around the first axis so as to enclose an interior space, the wall being provided with a plurality of through holes forming nozzles; providing a second body shaped so as to fit into the interior space of the hollow body, nesting the second body within the hollow body so that a gap is obtained between an inner surface of the wall of the hollow body and an outer surface of the second body; supplying a flow of liquid to the gap through a liquid inlet in liquid connection with the gap; generating a liquid jet from the nozzles in at least a radially outward direction relative to the first axis of rotation by driving at least one of the hollow body and the second body in a rotational motion around the first axis of rotation using a rotational drive unit; exerting a reciprocating pressure excitation on the liquid jet by moving one of the hollow body and the second body relative to the other of the hollow body and the second body along the first axis of rotation using a reciprocating drive unit; and decoupling the rotation of said one of the hollow body and the second body from the rotation of the reciprocating drive unit.

Description

Technical Field

[0001] This invention relates to a granulation method. Background Technology

[0002] Granulation is a known process for converting a given amount of liquid (specifically a given amount of molten material) into multiple fairly uniform spherical particles. It involves two operations: first, forming droplets from a given amount of liquid; and second, individually solidifying the droplets by cooling them as they fall through an upward flow of ambient air. Because there is no aggregation, the size distribution of the droplets determines the size distribution of the product. Plastic granules and laundry detergent are examples of the resulting products.

[0003] By installing a droplet generator on top of what is essentially a large cooling tower granulation tower, heat is transferred from the droplets to the air as they fall and solidify. The granulation tower must be tall enough to make the granules strong enough not to break upon impact with the tower floor.

[0004] Typically, the two approaches used to generate these droplets are not entirely the same. The first approach uses a static granulation cylinder, the simplest form of which is very similar to a shower head, where liquid is propelled through a fixed cylinder that includes dispersive nozzles for generating liquid jets. These jets break apart after traveling a certain distance, thus forming droplets. The second approach uses a rotating granulation cylinder. A rotating granulation cylinder includes dispersive nozzles in its sidewalls and / or bottom. By rotating the cylinder at a certain speed, centrifugal force propels the liquid through the nozzles, thereby generating a jet. Granulation devices that include rotating granulation cylinders tend to have a greater production capacity than those that include fixed cylinders.

[0005] A crucial step in granulation is generating droplets from a liquid stream, particularly controlling the size of these droplets precisely and accurately, thereby controlling the size of the resulting granules. The particle size distribution (also known as particle size distribution) produced using existing droplet distribution methods is typically quite broad. Specifically, these methods often generate “dust particles,” which reduce the process yield and tend to contaminate the surrounding environment. On the other hand, these methods also often produce large droplets that are not sufficiently solidified by the end of the process (i.e., when they reach the tower floor). As a result, these droplets break apart upon impact and may “stick” together (i.e., coalesce) the spherical particles that have accumulated at the bottom of the tower. This leads to a further reduction in the process yield. Summary of the Invention

[0006] One object of the present invention is to alleviate at least a portion of the aforementioned problems. Specifically, one object of the present invention is to increase granulation yield.

[0007] Therefore, the present invention provides a granulation method, comprising the following steps:

[0008] - Provide a hollow body arranged to rotate about a first axis of rotation, the hollow body including a wall that is symmetrically arranged to rotate about the first axis to surround an interior space, the wall being provided with a plurality of through holes forming nozzles;

[0009] - Provide a second body, the shape of which is designed to fit into the interior space of the hollow body, and nest the second body inside the hollow body so that a gap is obtained between the inner surface of the wall of the hollow body and the outer surface of the second body.

[0010] - Preferably, a liquid flow (e.g., molten material) is supplied to the gap through a liquid inlet connected to the gap liquid;

[0011] - By preferably using a rotary drive unit to drive at least one of the hollow body and the second body to rotate about a first rotation axis, a liquid jet is generated from the nozzle in at least a radially outward direction relative to the first axis;

[0012] - By preferably using a reciprocating drive unit to move one of the hollow body and the second body relative to the other of the hollow body and the second body along a first rotation axis, a reciprocating pressure excitation is applied to the liquid jet; and

[0013] - The rotation of one of the separated hollow bodies and the second body is related to the rotation of the reciprocating drive unit.

[0014] A reciprocating drive unit reciprocates one of the hollow body and the second body along the axial direction of the first axis, applying varying pressure to the liquid present in the gap. It should be noted that the suspension (i.e., nesting) arrangement of the second body creates a sufficiently large gap so that the hollow body and the second body never come into contact with each other. These pressure pulses propagate to the liquid jet generated by the nozzle through the wall of the hollow body, causing the jet to break into more uniformly sized droplets. To improve the precision of controlling the pressure variations applied to the liquid, the rotation of the hollow body and the second body is separated from the rotation of the reciprocating drive unit (at least about an axis parallel to the first axis). Thus, the reciprocating drive unit does not need to rotate with the hollow body, which also makes the construction of the reciprocating drive unit simpler and more robust, and eliminates the need to handle any torsional forces, such as those propagating from the hollow body and the second body, which would otherwise be introduced into the reciprocating drive unit. For example, even if only the hollow body is driven, the liquid present in the gap will effectively act as a hydraulic coupling, thereby transmitting torque to the second body. Therefore, separating the reciprocating drive unit from these rotations and associated torques allows the use of stacked piezoelectric elements within the reciprocating drive unit. Since these stacked piezoelectric elements can generate vibrations with sufficiently large force amplitudes over a wide frequency band and can be precisely controlled, small-amplitude, strong vibrations can be generated at a predetermined frequency and transmitted to one of the hollow and second bodies. This allows the liquid in the gap to be excited by reciprocating pressure excitation at a predetermined frequency. However, piezoelectric elements can be very sensitive to torsional loads and are therefore prone to damage.

[0015] This method enables the generation of a substantially uniform pressure distribution in the liquid across essentially the entire circumference of the internal space. It allows for more precise and accurate control of droplet size, thereby improving the performance of the granulation process in terms of particle / droplet size distribution. Furthermore, the device allows for a more uniform distribution of droplets across the width of the granulation tower, further increasing the yield of the granulation process. Therefore, this method allows for the production of droplets with smaller size variations compared to granulation methods according to the prior art. The liquid flow (e.g., molten material) is converted into droplets in the granulation process, and the droplets can solidify over time to obtain granules. It should be noted that this method (i.e., the method of distributing droplets) can also be applied to other processes where distributing droplets with smaller size variations is advantageous.

[0016] In a preferred embodiment, the step of separating the rotation includes: providing a coupling mechanism between the reciprocating drive unit and one of the hollow body and the second body; and enabling the hollow body and the second body to rotate relative to the reciprocating drive unit (at least about an axis parallel to the first axis) via the coupling mechanism. The coupling mechanism or coupling unit is arranged to enable the hollow body and the second body to rotate relative to the reciprocating drive unit in a reliable manner.

[0017] In a preferred embodiment, the coupling mechanism includes a first rotary bearing unit and a second rotation axis. The step of providing the coupling mechanism includes: coupling the lower end of a reciprocating drive unit to a first portion of the first rotary bearing unit, and coupling one of the hollow body and the second body to the second portion of the first rotary bearing unit. During the step of applying reciprocating pressure excitation, the lower end of the reciprocating drive unit moves between a first position and a second position in a direction substantially parallel to the second axis. The step of enabling relative rotation includes rotating the second portion of the rotary bearing unit relative to the first portion of the first rotary bearing unit about the second rotation axis. Thus, the reciprocating drive unit and one of the hollow body and the second body are effectively coupled via the rotary bearing, thereby substantially preventing the transmission of damaging torsional loads to the reciprocating drive unit.

[0018] In a preferred embodiment, the provided hollow body is at least partially substantially cylindrical and / or conical, wherein the internal space is at least partially substantially cylindrical or conical, and wherein the provided second body is shaped to substantially resemble the internal space of the hollow body, such that the width of the resulting gap is substantially constant along the entire circumference of the second body. In such a hollow body, a substantially uniform pressure distribution in the liquid can be generated over substantially the entire circumference of the internal space, which in turn improves performance in terms of droplet size uniformity and also allows for a more uniform distribution of droplets across the width of the granulation tower, thereby increasing the yield of the granulation process.

[0019] Further preferably, the method further includes the step of coaxially arranging the hollow body, the second body, and the first rotary bearing unit such that the first and second rotation axes coincide, and the hollow body, the second body, and the first rotary bearing unit rotate about the same rotation axis. Thus, during use, essentially only axial force acts on the first rotary bearing unit, eliminating the need to transmit any other reaction force to, for example, the support frame of the device, and enabling a robust and simple construction.

[0020] According to a preferred embodiment, the method further includes the step of using a controller to control a reciprocating drive unit so that one of the hollow body and the second body moves relative to the other of the hollow body and the second body at a predetermined frequency and amplitude. The control action of the controller allows for customization of the frequency and / or amplitude of driving the reciprocating drive unit, thereby further improving yield. For example, it has been found that the operating frequency and / or operating amplitude for driving the reciprocating drive unit can be determined, for example, based on the viscosity of the liquid, thereby splitting the jet into droplets of substantially more uniform size, thus improving yield.

[0021] In a preferred embodiment, the method includes the steps of: coupling a reciprocating drive unit to a frame assembly and suspending a coupling mechanism axially on the reciprocating drive unit. This allows the use of a reciprocating drive unit that requires a certain amount of tensile prestress for precise and reliable operation. More preferably, the method further includes the step of: arranging a second rotary bearing unit, configured to rotate about a third rotational axis, between the reciprocating drive unit and the frame, wherein the third rotational axis is substantially parallel to and preferably coincides with the second rotational axis. Thus, the reciprocating drive unit is arranged between the two bearing units and can rotate freely about its axis. Even in the event of a (partial) failure of the first bearing unit, the second bearing unit can still prevent the reciprocating drive unit from having to withstand excessive torque originating from either the hollow body or the second body.

[0022] In a preferred embodiment, the method includes the step of substantially blocking any rotation of the reciprocating drive unit about a second rotation axis by means of a rotary blocking mechanism. The coupling mechanism preferably includes a rotary blocking mechanism. For example, a relatively small torque may still be able to be transmitted through the coupling mechanism due to a small amount of friction in the coupling mechanism. By blocking rotation using the provided blocking mechanism, this torque is absorbed by the blocking mechanism and thus transferred around the reciprocating drive unit. Preferably, a stop pin (preferably provided in the blocking mechanism) is provided for blocking rotation (relative to the frame), as this allows for blocking rotation in a simple and reliable manner.

[0023] A preferred embodiment further includes the steps of: providing a stacked piezoelectric element in a reciprocating drive unit, and contracting and / or expanding the stacked piezoelectric element in a direction substantially parallel to the first axis to move one of the hollow body and the second body relative to the other. The stacked piezoelectric element can transmit the force required to propagate pressure changes or pressure pulses to the jet, causing the jet to break into droplets of more uniform size. Furthermore, the stacked piezoelectric element can be driven precisely in terms of frequency and amplitude, even at the desired force level.

[0024] In a preferred embodiment of the method, the method further includes a step of preloading the reciprocating drive unit using a biasing mechanism. Some types of actuators require a certain amount of preload to function properly. As a non-limiting example, stacked piezoelectric elements that require a minimum predetermined tensile preload to operate reliably can be used. Preferably, for example, the step of preloading the reciprocating drive unit using a biasing mechanism includes suspending the coupling mechanism and one of the hollow body and the second body onto the reciprocating drive unit, thereby applying a tensile preload to the reciprocating drive unit. Thus, gravity itself acts as the preload applied to the reciprocating drive unit, resulting in a simple and robust biasing mechanism.

[0025] Preferably, the method further includes providing a shaft assembly comprising a first shaft and a second shaft, and arranging the second shaft between the connecting mechanism and one of the hollow body and the second body, and arranging the first shaft between the rotary drive unit and the other of the hollow body and the second body. Since the second body is arranged within the internal space of the hollow body, and the two need to be driven in different ways, the shaft assembly is arranged such that the second shaft is positioned between the connecting mechanism and one of the hollow body and the second body, allowing the hollow body and the first body to be driven in a reciprocating manner; and the first shaft is positioned between the rotary drive unit and the other of the hollow body and the second body to allow rotation of at least the hollow body and the other of the second body, thereby subjecting the liquid in the gap to centrifugal force. Preferably, the method further includes the step of coaxially arranging the first shaft and the second shaft to obtain a compact shaft assembly suitable for the stated purpose. Alternatively or additionally, the method preferably further includes the step of arranging the first shaft to at least partially surround the second shaft in the radial direction, or arranging the second shaft to at least partially surround the first shaft in the radial direction. This also allows for a compact shaft assembly, in which the inner shaft is also protected by the outer shaft.

[0026] Preferably, alternatively or additionally, the step of providing the shaft assembly further includes providing a third bearing system arranged between the first and second shafts, wherein the third bearing system includes at least a linear bearing member; wherein the method further includes the step of moving the second shaft relative to the first shaft in an axial direction when one of the hollow body and the second body is moved relative to the other of the hollow body and the second body along a first axis of rotation using a reciprocating drive unit; these are preferably relative movements only permitted by the third bearing system. Thus, the third bearing system can achieve smooth operation with reduced friction. Furthermore, by connecting the first and second shafts by the third bearing system, the forces applied to the second shaft, in addition to the torque and axial force around the shaft, are transmitted to the first shaft, rather than through the connecting mechanism.

[0027] In a preferred embodiment, the method further includes the steps of: arranging a rotational transmission mechanism between the hollow body and the second body; and connecting the rotational motion of the hollow body and the second body about a first axis via the rotational transmission mechanism. Thus, the rotational motion transmitted from the rotational drive unit to the hollow body is also transmitted to the second body. Consequently, when both rotate at the same rotational speed, the shearing effects in the liquid are reduced; these shearing effects, for example, exist due to the speed difference between the hollow body and the second body, and have a decelerating effect on the liquid. Therefore, by connecting the rotational motion of the hollow body to the second body, the centrifugal force acting on the liquid in the gap and the pressure of the liquid acting on the inner surface of the hollow body wall can be more precisely controlled.

[0028] Preferably, the provided rotary transmission mechanism includes a male connector and a female connector. The male connector is disposed on one of the hollow body and the second body at a non-zero radial distance from the first axis, and the female connector is disposed on the other of the hollow body and the second body. The female connector is arranged to slidably receive the male connector to connect the rotational movement of the hollow body and the second body, while allowing relative movement between the hollow body and the second body in the axial direction. This provides a simple and robust rotary connection.

[0029] In a preferred embodiment, the method includes the step of supplying liquid flow to the gap by supplying liquid through a liquid inlet that merges into the second body and then through at least one through-hole in the second body, which forms a liquid connection between the gap and the liquid inlet. In use, liquid is thus supplied to the gap located between the hollow body and the second body. Preferably, the method then further includes the steps of: arranging a main through-hole extending substantially parallel to the first axis and merging into the lower part of the hollow body; and supplying liquid to the lower part of the hollow body through the main through-hole. Thus, the liquid supplied to the gap is distributed substantially uniformly in the radial direction on the circumference of the gap, which is also preferred if the main through-hole is arranged substantially centrally in the second body. Alternatively or additionally, the method may further include the steps of: arranging a secondary through-hole extending outward in at least the radial direction as viewed from the first axis on the circumference of the second body; and supplying liquid to the gap through the secondary through-hole. Thus, the supply of liquid can be distributed across the gap, thereby achieving a more uniform distribution in the axial direction on the circumference of the gap. Then, preferably, the step of arranging the secondary through-holes includes arranging the secondary through-holes of the second body at a non-zero distance from the nozzles of the hollow body when viewed in the radial direction. By arranging the holes and outlets so that they substantially do not overlap, a more uniform pressure distribution can be obtained on the inner wall of the hollow body. A more uniform pressure distribution at the wall results in more uniform (liquid) conditions at the nozzles arranged in the wall. As a result, the jet conditions are more uniform, thereby forming droplets more uniformly at different nozzles.

[0030] In a preferred embodiment, the method includes the steps of: arranging a substantially wing-shaped member in a through-hole of the second body; and causing a liquid flow to rotate with the rotation of the second body via the wing-shaped member. The wing-shaped member can be used to transmit the rotational motion of the hollow body and / or the second body to the liquid flow entering from the liquid inlet. The wing-shaped member preferably protrudes inward from the circumferential wall defining the through-hole. More preferably, the wing-shaped member protrudes substantially radially inward and / or wherein the wing-shaped member extends substantially over the entire height of the through-hole at least at the location of the circumferential wall. Thus, the liquid flow can be effectively forced into rotational motion by rotation, thereby forming a stable vortex of liquid within the hollow body or the second body.

[0031] In a preferred embodiment, the hollow body and the second body are hollow truncated cones, and the step of applying reciprocating pressure excitation includes reciprocatingly changing the width of the gap between the hollow body and the second body. The cylindrical body may, for example, be shaped externally as a truncated cone, i.e., a truncated cone. The hollow body and / or the second body preferably include an internal space of substantially similar shape. Due to the shape of the cylinder (i.e., a truncated cone or a truncated cone), the hollow body and the second body are substantially symmetrical, thereby achieving a uniform gap between the outer surface of the second body and the inner surface of the wall of the hollow body by arranging them substantially coaxially. By reciprocatingly driving one of the hollow body and the second body, the width of the gap changes reciprocally, allowing pressure pulses to be introduced into any liquid that may be present in the gap.

[0032] In a preferred embodiment, wherein the liquid jet splits into droplets, the method further includes the steps of: generating a cooling fluid flow; and at least partially solidifying the distributed droplets by cooling as they move through the generated cooling fluid flow. Thus, the droplets (preferably molten material) solidify due to the cooling fluid flow. The cooling fluid can be, for example, cooling a liquid or cooling a gas (depending on the nature of the liquid). Furthermore, the direction of the cooling fluid flow can be substantially along the direction of droplet descent (e.g., along the substantially vertically downward direction of gravity), but can also be substantially opposite to the direction of droplet descent (e.g., along the substantially vertically upward direction of gravity). By varying these parameters of the cooling fluid flow, the time (and / or distance) for at least partial solidification of the droplets can be adjusted to desired specifications. For example, even for very small particles, it can be ensured that the particles fall to the bottom of a suitable cooling tower, and that when the particles reach the bottom of the cooling tower, they are at least solidified to a degree that significantly reduces or even substantially prevents particle aggregation. Attached Figure Description

[0033] The invention is further illustrated by the following figures, which illustrate a preferred embodiment of the method, wherein a droplet dispensing device is used to generate particles from a liquid stream. The figures are not intended to limit the scope of the invention in any way, wherein:

[0034] - Figure 1 A 3D perspective view of a droplet dispensing apparatus for granulation, used to perform an embodiment of the method according to the invention, is schematically shown.

[0035] - Figure 2 schematically shown Figure 1 A cross-sectional view of the droplet dispensing device in the first plane.

[0036] - Figure 3 The diagram schematically shows an enlarged cross-sectional view of the top of the droplet dispensing device in a first plane.

[0037] - Figure 4 The diagram schematically shows an enlarged cross-sectional view of the bottom of the droplet dispensing device in a first plane.

[0038] - Figure 5 schematically shown Figure 1 A cross-sectional view of the droplet dispensing device in the second plane.

[0039] - Figure 6 The diagram schematically shows an enlarged cross-sectional view of the top of the droplet dispensing device in a second plane.

[0040] - Figure 7 The diagram schematically shows an enlarged cross-sectional view of the bottom of the droplet dispensing device in a second plane.

[0041] - Figure 8 A preferred embodiment of the reciprocating drive unit and coupling mechanism for a droplet dispensing device is schematically shown.

[0042] - Figure 9 The image shows the experimental results of the traditional droplet distribution method.

[0043] - Figure 10 An image showing experimental results of a droplet dispensing method according to an embodiment of the present invention is illustrated.

[0044] - Figure 11 Two different types of nozzles are schematically shown arranged in the circumferential wall of a hollow body. Detailed Implementation

[0045] Figure 1A 3D perspective view of a droplet dispensing apparatus for performing an embodiment of the method according to the invention is schematically shown. The droplet dispensing apparatus 1 includes a lower rotating assembly 2 comprising a hollow body 21 and a second body 22. A rotation drive unit 3 is arranged to drive the rotation of the lower rotating assembly 2, a reciprocating drive unit 4 is used to reciprocate the second body 22 along a rotation axis I, and a coupling mechanism 8 is used to separate the rotation from the reciprocating drive unit 4. The apparatus may also include a mounting bracket assembly 5, comprising, for example, a mounting bracket 51 for mounting the apparatus in a suitable cooling tower (i.e., a granulation tower (not shown)). Furthermore, the cylinder 52 is similar in size to an opening through which the apparatus typically needs to be inserted for mounting in the granulation tower. An inlet piping system 6 is provided for supplying liquid to the lower rotating assembly 2 of the apparatus 1, as described in more detail below. Reference will be made below. Figures 1 to 8 and Figure 11 The operation of an embodiment of device 1 will be described in more detail.

[0046] Figures 2 to 4 schematically shown Figure 1 A cross-sectional view of the droplet dispensing device 1 for granulation in the first plane. Figures 5 to 7 schematically shown Figure 1 The droplet distribution device is shown in a cross-sectional view in a second plane that is substantially perpendicular to the first plane. The lower rotating assembly 2 includes a rotating hollow body 21 in which a rotating second body 22 is arranged. The hollow body 21 and the second body 22 are shaped such that the shape of the second body 22 (at least on its outer side) is adapted to fit into the interior space 211 of the hollow body 21, and the second body 22 substantially matches the shape of the interior space 211 of the hollow body 21, thereby forming a gap 23 between the outer surface of the second body 22 and the inner surface of the circumferential wall of the hollow body 21. The hollow body 21 and the second body 22 are preferably substantially cylindrical (i.e., formed as hollow conical truncated sections) and are arranged such that, once installed in the granulation tower, the top of the hollow body 21 and the second body 22 has a larger dimension (e.g., diameter) than the bottom of the hollow body 21 and the second body 22. This helps to distribute the droplets more evenly throughout the granulation tower.

[0047] The second body 22 may include an opening 221 at its bottom and a plurality of smaller through holes 222, which may be arranged in several rows of through holes 222 at different (angular) positions in the circumferential wall of the second body 22, as observed about the axis of rotation I. These rows of through holes 222 may extend substantially over the entire height of the second body 22.

[0048] In use, the central inlet 24 guides the liquid flow into the interior space of the second body 22. The central inlet 24 may be fitted with multiple flow guiding elements 241, 242, which facilitate guiding the liquid flow toward and / or in the direction of rotation of the interior space of the second body 22. The liquid then flows through the opening 221 and / or through multiple through-holes 222 into the gap 23. Multiple through-holes (also referred to as nozzles 91, 92) are arranged in the circumferential wall 212 of the hollow body 21. In use, the hollow body 21 rotates about the axis of rotation I, such that any liquid held in the gap 23 is exposed to centrifugal force emanating from the rotation, thereby generating pressure in the liquid and forcing the liquid out of the multiple nozzles 91, 92, thus forming liquid jets 901, 911 (see...). Figure 9 and Figure 10 The liquid jets 901 and 911 are guided at least partially radially outward relative to the axis of rotation I. Since the width of the gap 23 can be varied reciprocally by driving a reciprocating drive unit (as described in more detail below), pressure pulses can be introduced into the liquid present in the gap 23. These pulses propagate to the jets ejected from nozzles 91 and 92. By adjusting the frequency and amplitude of the width variation of the gap 23, pressure pulses that cause the jet to rapidly split into droplets can be obtained, resulting in droplets of substantially equal size, thus significantly reducing droplet size diffusion.

[0049] Nozzles 91, 92 (see) Figure 11 The nozzles 91, 92, or any combination of these nozzles and other types of nozzles can be arranged in different ways within the circumferential wall 212. The first nozzle 91 is arranged as a through-hole substantially perpendicular to the outer and / or inner surfaces of the circumferential wall 212. The second nozzle 92 is arranged such that, once the droplet dispensing device is installed in the granulation tower, the through-hole extends substantially horizontally (i.e., substantially perpendicular to the axis of rotation I). Alternatively, a recess 93 can be arranged in the outer surface of the circumferential wall 212 of the hollow body 21, such that the through-hole of the second nozzle 92 merges into the recess 93, wherein the surface of the recess 93 is substantially perpendicular to the through-hole of the second nozzle 92.

[0050] The second body 22 may further include a plurality of wing-shaped components 223 extending radially from the central axis connector 224 toward the circumferential wall 225 of the second body 22. These wing-shaped components 223 force the liquid entering the interior space of the second body 22 to rotate with the second body 22. Further, additional flow-directing elements 226 may be arranged on top of the wing-shaped components 223 to help distribute the liquid throughout the second body 22. Thus, a stable and substantially constant vortex of rotating liquid can be obtained in the second body and the hollow body, thereby generating more constant process conditions at the nozzles 91, 92 and thus better controlling the process. In this embodiment, the second body 22 is connected at its top 226 to the top 213 of the hollow body 21. The hollow body 21 itself is driven by the rotary drive unit 3. An outer shaft 71 is provided, which is connected at its first end 711 to the rotary drive unit and at its second end 712 to the top 213 of the hollow body. The outer shaft 71 can be connected to the mounting bracket assembly 5 via a rotary bearing 74. The mounting bracket assembly includes a bracket mounting support 51 for mounting or arranging the droplet generating device 1 in the granulation tower.

[0051] The second body 22 is connected to the inner shaft 72 via a central axis connector 224, which is arranged to receive and engage with the lower portion 721 of the inner shaft 72. The inner shaft 71 is largely surrounded by the outer shaft 72 and supported by a plurality of sliding bearings 73, allowing the inner shaft 71 (preferably only) to move relative to the outer shaft 72 in the direction along the axis of rotation I and in the direction of rotation about the axis of rotation I. To protect the sliding bearings 73 and the space between the inner shaft 71 and the outer shaft 72 from dust and / or liquid contamination, a flexible bearing cap 75 is arranged between the bottom 712 of the outer shaft 71 and the central axis connector 224.

[0052] Figure 3 A schematic cross-sectional view of the droplet dispensing device in a first plane, magnified from the top of the device 1, is shown. In this embodiment, the rotary drive unit 3 is configured to drive the outer shaft 71 using a second pulley 34, which can be directly connected to the first end 711 of the outer shaft 71. The rotary drive unit 3 may include a (electric) motor 31 that drives the first pulley 32, and wherein the first pulley 32 and the second pulley 34 are connected by a drive belt 33 that transmits rotational motion from the motor 31 to the outer shaft 71. However, it should be noted that any other suitable rotary transmission mechanism or drive mechanism may be used for this purpose. The outer shaft 71 is connected to a shaft retainer 54 via a rotary bearing 74, the shaft retainer 54 being formed by a tubular member connecting and retaining the rotary bearing 74, and wherein the shaft retainer 54 is in turn connected to a base member 53, the base member 53 further including a mounting bracket 51.

[0053] For the inner shaft 72, which is mostly surrounded by the outer shaft 71, an extension extends from the first end 711 of the outer shaft at its upper end 721. The upper end 721 is received by the output shaft 81 of the connecting mechanism 8. The connecting mechanism 8, including the rotary bearing 82, undertakes the rotational movement of the inner shaft 72, thereby protecting the reciprocating drive unit 4 from any torsional forces that could potentially damage the vibrating element 41, which is preferably a stacked piezoelectric element. The stacked piezoelectric element is capable of generating a wide-bandgap vibration with a sufficiently large force amplitude and can be precisely controlled, thereby obtaining small-amplitude vibrations.

[0054] To secure the vibrating element 41 accordingly, it is held between the lower connecting member 42 and the upper connecting member 43. The vibrating element 41 is directly connected to and held on the upper connecting member 43. The lower connecting member 42 is directly connected to the upper part 83 of the connecting mechanism 8. The upper connecting member 43 is held by a secondary connecting mechanism 84, which also includes a rotary bearing 85. Thus, the reciprocating drive unit 4 is unrestricted in its rotation about the rotation axis I, such that even if a small torsional force is transmitted through the connecting mechanism 8, the vibrating element 41 is effectively isolated from any potentially damaging torsional force that might be potentially transmitted from the inner shaft 72. To further facilitate this, the connecting mechanism 8 includes a stop pin 86 that transmits the generated torsional force to the frame suspension member 55.

[0055] The secondary connecting mechanism 84 is directly connected to the suspension member 55 via its fixed upper part 86. Thus, the reciprocating drive unit 4, the connecting mechanism 8, the inner shaft 72, and the second body 22 are all suspended on the suspension member 55. Axial forces from these parts are thus transmitted through the vibrating element 41, thereby giving the vibrating element 41 a preload. These suspended parts 8, 72, and 22 effectively form a biasing mechanism for the vibrating element 41. The suspension member 55 is part of the fixed frame assembly 5.

[0056] Figure 5 It shows that along the line that is substantially perpendicular to Figures 2 to 4 A cross-sectional view of the plane. Figure 5 A liquid inlet portion 6 is shown, comprising an assembly of tubular members and arranged to connect at its first end 61 to a liquid supply system and at its second end 62 to converge into a central inlet 24. Liquid flows through a fixed first section 244 of the central inlet 24 and is arranged to flow to a second section 244 of the central inlet 24, wherein the second section 242 rotates together with the hollow body 21.

[0057] In use, the hollow body 21 is driven by the rotary drive unit 3 to rotate along the rotation axis I, as described above. Liquid is supplied to the second body 22 through the liquid inlet portion 6, allowing the liquid to reach the gap 23 through the second body 21, which includes multiple openings 221, 222. The reciprocating drive unit 4 is used to change the width of the gap 23. In the current embodiment, this is achieved by driving a vibrating element 41, which transmits the reciprocating motion along the rotation axis I to the second body 22 via the coupling mechanism 8 and the inner shaft 72. By controlling the vibrating element 41 according to a predetermined frequency and amplitude, pressure pulses are introduced into the liquid held in the hollow body 21. The combination of the centrifugal force caused by rotation and the pressure pulses introduced into the liquid allows a jet to be formed through nozzles 91, 92, which breaks into individual droplets, wherein the individual droplets have only small variations in size (compared to conventional rotating droplet generating devices), making them substantially uniform in size.

[0058] exist Figure 10 The results from the experimental setup using the device are shown in the figure, while Figure 9 The photograph shows the results of an experimental setup from a conventional rotating droplet generating device. The photograph shows a hollow body 121 including a first nozzle 91 and a second nozzle 92. The second nozzle 92 is arranged to converge into a recess 93 disposed in the outer surface of the hollow body 121. Figure 9 In the image, we can see the actual liquid jet 901 leaving the nozzles 91 and 92. The liquid jet 901 only breaks into a series of droplets 902 of different sizes after a certain distance. The droplets 902 are widely distributed in size because the jet breaks into larger primary droplets and smaller secondary or satellite droplets. As many different droplets may recombine downstream to form even larger droplets, the droplet size is greatly diffused.

[0059] exist Figure 10In the process, the liquid in the hollow body 22 is excited by a pressure pulse with a predetermined frequency and amplitude. It is evident that the jet 911 begins to split almost immediately after exiting the nozzles 91 and 92, and the resulting droplets 912 are more similar in size compared to droplets 911. Furthermore, the individual droplets 912 are observed to be dispersed at more regular intervals, resulting in less droplet coalescence. In the experimental setup, water / glycerol mixtures with different viscosities were tested. In the first test, water with a viscosity of 1 mPa*s was used, where excellent results (in terms of a narrow distribution of droplet size) were found to be obtained by: rotating the cylinder to achieve a water velocity of 1.5 m / s in the resulting jet; and by introducing a pressure pulse caused by a vibration with a frequency of approximately 280 Hz and an amplitude of approximately 20 μm. When using a slightly more viscous mixture with a viscosity of 4 mPa*s, the following set of basic ideal conditions was found, for example: a liquid jet velocity of 1.3 m / s; and by introducing pressure pulses caused by the introduction of vibrations with a frequency of approximately 240 Hz and an amplitude of approximately 35 μm. When using a more extreme mixture with a viscosity of 35 mPa*s, excellent results were obtained, for example: a velocity of 1.15 m / s; and vibrations were introduced with a frequency of approximately 190 Hz and an amplitude of approximately 35 μm.

[0060] Figure 8 Further shown are the coupling mechanism 108 of the alternative embodiment and the sub-coupling mechanism 1084 of the alternative embodiment, wherein all other components are connected to... Figures 1 to 7 The illustrated embodiment is the same. The connecting mechanism 108 includes two rotary bearings 1082, specifically spherical roller thrust bearings, which are preferably substantially identical. The bearings 1082 are arranged such that their first ends 1086 are arranged adjacent to each other, allowing only rotational movement of the output shaft 82 relative to the housing unit 187 of the connecting mechanism 108, thereby achieving a reliable connecting mechanism 108 with minimal clearance in the axial direction. Clearance in the axial direction of the connecting mechanism 108 affects the transmission of vibration from the vibrating element 41 to the second body 22, and thus negatively impacts the performance of the droplet generating device 1. Furthermore, the spherical roller thrust bearings are well-suited for transmitting high axial (i.e., thrust) loads, thus achieving a reliable connecting mechanism 108 for transmitting axial force from the reciprocating drive unit 4 to the second body. Moreover, the secondary connecting mechanism 1084 includes a similar arrangement of two rotary bearings 1085, specifically spherical roller thrust bearings.

[0061] The invention is not limited to the embodiments shown, but extends to other embodiments that fall within the scope of the appended claims.

Claims

1. A granulation method, comprising the following steps: - Provide a hollow body arranged to rotate about a first rotation axis, the hollow body including a wall arranged symmetrically about the first rotation axis to surround an internal space, the wall being provided with a plurality of through holes forming nozzles; - Provide a second body, the shape of which is adapted to be fitted into the internal space of the hollow body, the second body being nested in the hollow body such that a gap is obtained between the inner surface of the wall of the hollow body and the outer surface of the second body; - A liquid flow is supplied to the gap through a liquid inlet connected to the gap liquid; - By using a rotary drive unit to drive at least one of the hollow body and the second body to rotate about the first rotation axis, a liquid jet is generated from the nozzle in at least a radially outward direction relative to the first rotation axis; - By using a reciprocating drive unit to move one of the hollow body and the second body relative to the other of the hollow body and the second body along the first rotation axis, a reciprocating pressure excitation is applied to the liquid jet; and - The rotation of one of the hollow body and the second body about an axis parallel to the first rotation axis is separated from the rotation of the reciprocating drive unit about the axis parallel to the first rotation axis.

2. The granulation method according to claim 1, wherein the step of separating the rotation comprises: -A connection mechanism is provided between the reciprocating drive unit and one of the hollow body and the second body; -The connecting mechanism enables one of the hollow body and the second body to rotate relative to the reciprocating drive unit.

3. The granulation method according to claim 2, wherein the connecting mechanism comprises a first rotary bearing unit and a second rotary axis, wherein the step of providing the connecting mechanism comprises: The lower end of the reciprocating drive unit is connected to the first part of the first rotary bearing unit, and one of the hollow body and the second body is connected to the second part of the first rotary bearing unit. -During the step of applying reciprocating pressure excitation, the lower end of the reciprocating drive unit moves between the first and second positions in a direction parallel to the second rotation axis, and -The step of enabling relative rotation includes rotating the second portion of the rotary bearing unit about the second rotation axis relative to the first portion of the first rotary bearing unit.

4. The granulation method according to claim 3, wherein the provided hollow body is at least partially cylindrical and / or conical, wherein the internal space is at least partially cylindrical or conical, and wherein the shape of the provided second body is designed to resemble the internal space of the hollow body, such that the width of the obtained gap is constant along the entire circumference of the second body.

5. The granulation method according to claim 4 further includes the following step: The hollow body, the second body, and the first rotary bearing unit are arranged coaxially such that the first rotation axis and the second rotation axis coincide, and the hollow body, the second body, and the first rotary bearing unit rotate around the same rotation axis.

6. The granulation method according to any one of claims 1 to 5, further comprising the following step: A controller is used to control the reciprocating drive unit so that one of the hollow body and the second body moves relative to the other of the hollow body and the second body at a predetermined frequency and amplitude.

7. The granulation method according to any one of claims 3 to 5, further comprising the following step: The reciprocating drive unit is connected to the frame assembly, and the connecting mechanism is suspended on the reciprocating drive unit in the axial direction.

8. The granulation method according to claim 7 further includes the following step: A second rotary bearing unit, arranged to rotate about a third rotation axis, is disposed between the reciprocating drive unit and the frame assembly, wherein the third rotation axis is parallel to the second rotation axis.

9. The granulation method according to claim 7 further comprises the following steps: A second rotary bearing unit, arranged to rotate about a third rotation axis, is disposed between the reciprocating drive unit and the frame assembly, wherein the third rotation axis coincides with the second rotation axis.

10. The granulation method according to any one of claims 3 to 5, comprising the step of blocking any rotation of the reciprocating drive unit about the second rotation axis by means of a rotation blocking mechanism.

11. The granulation method of claim 10, further comprising the step of providing a stop pin for the blocking mechanism to block the rotation.

12. The granulation method according to any one of claims 1 to 5, further comprising providing a stacked piezoelectric element in the reciprocating drive unit, and contracting and / or expanding the stacked piezoelectric element in a direction parallel to the first axis of rotation to cause one of the hollow body and the second body to move relative to the other of the hollow body and the second body.

13. The granulation method according to any one of claims 2 to 5, further comprising the step of preloading the reciprocating drive unit using a biasing mechanism.

14. The granulation method of claim 13, wherein the step of preloading the reciprocating drive unit using a biasing mechanism comprises: - Suspend the connecting mechanism and one of the hollow body and the second body on the reciprocating drive unit, thereby applying a tensile preload to the reciprocating drive unit.

15. The granulation method of claim 2, further comprising providing a shaft assembly including a first shaft and a second shaft, and arranging the second shaft between the coupling mechanism and one of the hollow body and the second body, and arranging the first shaft between the rotary drive unit and the other of the hollow body and the second body.

16. The granulation method according to claim 15 further includes the step of arranging the first shaft and the second shaft coaxially.

17. The granulation method according to claim 15, comprising the following steps: The first shaft is arranged to at least partially surround the second shaft in the radial direction, or the second shaft is arranged to at least partially surround the first shaft in the radial direction.

18. The granulation method according to claim 15, 16 or 17, wherein the step of providing the shaft assembly further comprises providing a third bearing system disposed between the first shaft and the second shaft, wherein the third bearing system comprises at least a linear bearing member; -The method further includes the following steps: When the reciprocating drive unit is used to move one of the hollow body and the second body relative to the other of the hollow body and the second body along the first rotation axis, the second axis moves in the axial direction relative to the first axis.

19. The granulation method according to any one of claims 1 to 5, further comprising the following step: - The rotary transmission mechanism is arranged between the hollow body and the second body; - The rotational motion of the hollow body and the second body around the first rotation axis is connected by the rotational transmission mechanism.

20. The granulation method of claim 1, wherein the step of supplying the liquid flow to the gap comprises: The liquid is supplied through the liquid inlet into the second body and then through at least one through-hole in the second body, the at least one through-hole forming a liquid connection between the gap and the liquid inlet.

21. The granulation method according to claim 20, further comprising the following steps: - The main through-hole is arranged to extend parallel to the first axis of rotation and merge into the lower part of the hollow body; - The liquid is supplied to the lower part of the hollow body through the main through-hole.

22. The granulation method according to claim 20, further comprising the following steps: - A secondary through-hole extending outward in at least the radial direction as viewed from the first axis of rotation is arranged on the circumference of the second body; - The liquid is supplied to the gap through the secondary through-hole.

23. The granulation method according to claim 22, wherein the step of arranging the secondary through-holes comprises: The secondary through-hole of the second body is arranged such that, when viewed along the radial direction, it is at a non-zero distance from the nozzle of the hollow body.

24. The granulation method according to any one of claims 20 to 23, comprising the following steps: - A wing-shaped component is arranged in the through-hole of the second body; and - The wing-shaped component causes the liquid flow to rotate as the second body rotates.

25. The granulation method according to any one of claims 1 to 5, 15 to 17, or 20 to 23, wherein the hollow body and the second body are hollow conical truncated bodies, and wherein the step of applying reciprocating pressure excitation includes reciprocatingly changing the width of the gap between the hollow body and the second body.

26. The granulation method according to any one of claims 1 to 5, 15 to 17, or 20 to 23, wherein the liquid jet splits into droplets, the method further comprising the step of: - Generates a cooling fluid flow; - When the dispensed droplets move through the generated cooling fluid flow, the dispensed droplets are at least partially solidified by cooling.

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