Multi-stage centrifugal atomizer and process

Abstract

Multi-stage centrifugal atomizer (100), comprising: an outer shell (102) which includes an inlet port (101) and an outlet port (121) and which comprises: a distributor (104), a first inclined rotating surface (106); and a second inclined rotating surface (108); wherein the first inclined rotating surface (106) is arranged opposite the second inclined rotating surface (108); wherein the inlet is used to introduce a molten material into the multi-stage atomizer, and wherein the outlet is used to remove ultrafine particles with a D50 of less than 20 micrometers; and wherein a convex surface of the first inclined rotating surface (106) faces the inlet of the multi-stage centrifugal atomizer (100) and wherein a convex surface of the second inclined rotating surface (108) faces the outlet of the multi-stage centrifugal atomizer (100) and wherein the first inclined rotating surface (106) serves to receive a molten material from the distributor (104) and to discharge the molten material in the form of particles, wherein the second inclined rotating surface (108) serves to receive the particles from the first inclined rotating surface (106) and to reduce them to a smaller particle size than that which is received from the first inclined rotating surface (106).

Description

[0001] This disclosure relates to an article for the production of ultrafine powders and a process for producing the article, as well as the fine powders. In particular, this disclosure relates to a centrifugal atomizer that can be used to produce fine powders with a very narrow polydispersity index (variation of particle sizes).

[0002] Centrifugal atomizers, such as those used in spray dryers, employ an atomizer head that rotates at relatively high speed and to which the feed material (to be atomized) is fed. The head is equipped with impact elements that break the feed material into small droplets or fragments, which are then expelled to the outside for suspension in a drying gas. A particular type of atomizer head, which is widely used, employs spaced upper and lower plates attached to a vertical shaft and connected by circumferentially spaced atomizing rods. The feed material is fed into a chamber in the central part of the head, and as it moves outward between the upper and lower plates, it is ultimately crushed and atomized by the spaced rods.

[0003] Conventional atomizing devices of the type described above have certain disadvantages. While the atomization achieved is suitable for many commercial operations, maintaining a relatively uniform degree of atomization is difficult, especially with different types of feed material. Uniform atomization is desirable because it significantly facilitates the proper operation of the spray dryer. It prevents the undesirable discharge of oversized particles against the dryer's side walls, facilitates dryer operation at a desired high capacity, and tends to result in a final product with a uniform moisture content. Another disadvantage is that the impact elements are subject to wear. Any attempt to repair the worn parts is laborious and expensive, and generally, the main components of the head must be discarded and replaced.The costs of repairing or replacing such worn parts significantly increase the costs of spray drying processes.

[0004] It is therefore desirable to provide a relatively simple centrifugal atomizer capable of producing uniform atomization with a wide variety of feed materials.

[0005] DE 3341184 A1 relates to a method for producing ultrafine solid metal particles, wherein a stream of molten metal is directed onto a rotating first circular surface.

[0006] US 3986706 A concerns the continuous mixing of particulate materials with liquids and / or other particulate materials and deals in particular with new methods for efficient mixing.

[0007] KR 10 2014 099 144 A describes a device for producing subcooled powder with a rotating cooling device that includes a recessed section.

[0008] DE 4221512 A1 relates to a method and a device for producing rapidly solidified, individual plate-shaped particles directly from the melt.

[0009] CN 1 09 622 982 A discloses a device and a method for producing metal powder, wherein a melt is distributed by centrifugal atomization.

[0010] It can be considered an objective to provide an alternative centrifugal atomizer and an alternative method for producing ultrafine particles. This objective is achieved by the subject matter of claim 1 and the subject matter of claim 8.

[0011] The multi-stage centrifugal atomizer according to the invention comprises an outer shell containing an inlet port and an outlet port, and enclosing a distributor, a first inclined rotating surface, and a second inclined rotating surface. The first inclined rotating surface is arranged opposite the second inclined rotating surface. The inlet is used to introduce a molten material into the multi-stage atomizer, and the outlet is used to remove ultrafine particles with a D50 of less than 20 micrometers.

[0012] A convex surface of the first inclined rotating surface faces the inlet of the multi-stage centrifugal atomizer, and a convex surface of the second inclined rotating surface faces the outlet of the multi-stage centrifugal atomizer.

[0013] The first inclined rotating surface serves to receive molten material from the distributor and to release the molten material in the form of particles, the second inclined rotating surface serving to receive the particles from the first inclined rotating surface and to reduce them to a smaller particle size than that received from the first inclined rotating surface.

[0014] According to one embodiment, an angle γ between an upper inner surface and the outer lower surface of the second inclined rotating surface varies between 90 degrees and 180 degrees.

[0015] According to one embodiment, a first shaft, which touches the first inclined rotating surface, and a second shaft, which touches the second inclined rotating surface, are mounted coaxially and are in rotary connection with a motor.

[0016] According to one embodiment, the first inclined rotating surface is a cone or a conical section and the second inclined rotating surface is a cone or a conical section, wherein a convex surface of the first inclined rotating surface faces the inlet port and a convex surface of the second inclined rotating surface faces the outlet port.

[0017] According to one embodiment, the first inclined rotating surface has an interior angle that is smaller than the interior angle of the second inclined rotating surface.

[0018] According to one embodiment, the convex surface of the first inclined rotating surface includes a section structured with grooves and patterns to facilitate the comminution of a molten material that comes into contact with it.

[0019] According to one embodiment, the convex surface of the first inclined rotating surface includes a section that has non-stick properties.

[0020] According to one embodiment, a concave surface of the second inclined rotating surface includes a section structured with grooves and patterns to facilitate the comminution of a molten material that comes into contact with it.

[0021] According to one embodiment, the convex surface of the second inclined rotating surface is in fluid communication with the outlet port of the multi-stage centrifugal atomizer.

[0022] According to one embodiment, the multi-stage centrifugal atomizer comprises an ultrasonic transducer that is operatively connected either to the first inclined rotating surface, the second inclined rotating surface, or to both the first inclined rotating surface and the second inclined rotating surface.

[0023] According to one embodiment, the ultrasonic transducer delivers a linear back-and-forth motion of up to 50 micrometers at 20 kHz or more to the first inclined rotating surface, the second inclined rotating surface, or both the first inclined rotating surface and the second inclined rotating surface.

[0024] According to one embodiment, the multi-stage centrifugal atomizer removes ultrafine particles with a D50 diameter of 20 micrometers or less.

[0025] According to one embodiment, the multi-stage centrifugal atomizer removes ultrafine particles with a D50 diameter of 20 micrometers or less.

[0026] According to one embodiment, the ultrafine particles comprise silicon or silicon alloys for use in batteries.

[0027] The inventive method for producing ultrafine particles comprises introducing a molten material into an inlet port of a multi-stage centrifugal atomizer, wherein the multi-stage centrifugal atomizer comprises an outer shell containing an inlet port and an outlet port, and enclosing a distributor, a first inclined rotating surface, and a second inclined rotating surface. The first inclined rotating surface is arranged opposite the second inclined rotating surface. The inlet is used to introduce a molten material into the multi-stage atomizer, and the outlet is used to remove ultrafine particles with a D50 of less than 20 micrometers.A convex surface of the first inclined rotating surface faces the inlet of the multi-stage centrifugal atomizer, and a convex surface of the second inclined rotating surface faces the outlet of the multi-stage centrifugal atomizer. The first inclined rotating surface serves to receive molten material from the distributor and discharge it in the form of particles. The second inclined rotating surface serves to receive the particles from the first inclined rotating surface and reduce them to a smaller particle size than those received from the first inclined rotating surface. The molten material is conveyed from the distributor onto the first inclined rotating surface to form particles.The particles are transported from the first inclined rotating surface to the second inclined rotating surface to form the ultrafine particles.

[0028] According to one embodiment, the method further includes removing the ultrafine particles from the outlet port.

[0029] According to one embodiment, the method further comprises exposing the first inclined rotating surface, the second inclined rotating surface, or both the first inclined rotating surface and the second inclined rotating surface to an ultrasonic vibration.

[0030] According to one embodiment, the method further comprises conveying the molten material from the distributor onto the first inclined rotating surface to form particles, and conveying the particles from the first inclined rotating surface to the second inclined rotating surface to form the ultrafine particles, which is carried out simultaneously.

[0031] The features and advantages mentioned above, as well as other features and advantages of the disclosure, are readily apparent from the following detailed description when considered in conjunction with the accompanying drawings.

[0032] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings in which: Fig. 1 is a schematic representation of an exemplary multi-stage centrifugal atomizer; Fig. 2A is another schematic representation of an exemplary section of the multi-stage centrifugal atomizer, showing the arrangement between the two shafts and a piezoelectric stack; Fig. 2B is another schematic representation of an exemplary multi-stage centrifugal atomizer, showing the arrangement between the two shafts; and Fig. Figure 3 is a schematic representation of an exemplary drive to provide rotary motion for the first inclined rotating surface and the second inclined rotating surface.

[0033] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numbers point to identical or equivalent parts and features.

[0034] According to an exemplary embodiment, a multi-stage centrifugal atomizer is disclosed herein, the design of which facilitates the production of particles with a smaller average particle size (hereinafter referred to as ultrafine particles) and a narrower particle size distribution than other commercially available centrifugal atomizers. The multi-stage centrifugal atomizer increases the flow rate of the molten material into the centrifuge and therefore also increases the production rate of the ultrafine particles compared to other commercially available centrifugal atomizers. The multi-stage coaxial centrifugal atomizer has the advantage of producing ultrafine particles (with a target D50 of less than 20 micrometers) with a spherical shape, a narrow particle size distribution, and a homogeneous composition for automotive and non-automotive (energy, aerospace, marine, and the like) industrial applications.D stands for the diameter of powder particles, and D50 means that a cumulative 50% diameter point (or 50% pass particle size) is less than 20 micrometers.

[0035] In one embodiment, the multi-stage coaxial centrifugal atomizer can be used to produce silicon or silicon alloy particles with a D50 of less than 20 micrometers, preferably less than 15 micrometers, and even more preferably less than 10 micrometers. These silicon alloy or silicon particles with a uniform diameter can be used in batteries and energy storage devices.

[0036] The comminution of the molten material can occur in two or more stages. In the first stage, the molten material is discharged from a distributor onto a first inclined rotating surface. This promotes the comminution of the molten material into particles. In the second stage, the particles are discharged from the first inclined rotating surface onto a second inclined rotating surface. The second stage promotes further comminution of the particles into ultrafine particles. The ultrafine particles (50% of which have an average size of less than 20 micrometers) are then discharged from the centrifugal atomizer into a collection vessel. In one embodiment, ultrasonic energy can be transferred either to the first inclined rotating surface, to the second inclined rotating surface, or to both.Ultrasound energy facilitates both the comminution of the molten material and the deagglomeration of particles from agglomerates.

[0037] Fig. Figure 1 shows an exemplary schematic of the multi-stage centrifugal atomizer 100 of this disclosure. The atomizer 100 comprises an outer shell 102 with an inlet port 101 for filling it with the molten material to be atomized. The molten material can be a metal, a ceramic, a polymer, or a combination thereof. Inside the outer shell 102 is a distributor 104, which receives the material that is filled in through the inlet port 101. The distributor 104 contains a plurality of outlet ports 105 through which the material can be discharged to a first inclined rotating surface 106. The molten material contacts the outer (convex) surface of the first inclined rotating surface 106.

[0038] The atomizer 100 also contains a first inclined rotating surface 106 and a second inclined rotating surface 108, which operate in stages to crush the molten material fed to the atomizer.

[0039] The first inclined rotating surface 106 preferably has the shape of a cone. The convex surface of the first inclined rotating surface includes a section 107 containing grooves and patterns to facilitate the comminution of the material that comes into contact with it. The underside 111 of the first inclined rotating surface is provided with a non-stick coating to prevent the material from adhering to the surface. The non-stick coating facilitates the rapid discharge of the material particles from the first inclined rotating surface 106 to the second inclined rotating surface 108, from which the particles are conveyed to an outlet port 121 of the multi-stage centrifugal atomizer 100.A section 109 of the convex surface, located between section 107 and the bottom 111, is the place where the molten material collects during the atomization process as it is conveyed from the distributor to the first inclined rotating surface.

[0040] An example of the second inclined rotating surface 108 is a rotating cup. The second inclined rotating surface can be considered a hollowed-out cone or conical section into which the particles conveyed by the first inclined rotating surface are directed. The concave surface of the second inclined rotating surface 108 includes a section 113 coated with a non-stick surface. The section 115, which abuts the non-stick surface, is inclined and facilitates dispensing from the second inclined rotating surface 108 to the outlet port 121 of the multi-stage centrifugal atomizer 100. In one embodiment, the second inclined rotating surface is arranged opposite the first inclined rotating surface.Material particles formed on the convex surface of the first inclined rotating surface are conveyed to the concave surface of the second inclined rotating surface. The second inclined rotating surface is in fluid communication with the outlet port 121 of the atomizer. Ultrafine particles forming on the second inclined rotating surface are discharged via the outlet port 121 into a reservoir. The ultrafine particles that have formed on the second inclined rotating surface are discharged into the outlet port 121 after passing over and over an upper lip of the non-stick coated section 113. The ultrafine particles are transported to the outlet port 121 by gravity, as shown in [reference]. Fig. 1 shown.

[0041] The distributor 104 includes one or more inlets 103 for conveying molten material from a furnace 202 into it. The distributor 104 should be able to withstand the temperature of the melt without deforming or reacting with the material. The distributor 104 may have one or more outlet ports 105 of a suitable diameter to facilitate rapid discharge of the molten material to the first inclined rotating surface 106. The number of outlet ports 105 and their diameters can be adjusted to control the particle size during and after atomization. The distributor may have two or more outlet ports, preferably three or more, etc.

[0042] The distributor can be stationary or, alternatively, rotate around a vertical shaft (not shown). In a preferred embodiment, the distributor is stationary. In another embodiment, pressure can be applied to the distributor to facilitate the discharge of the molten material.

[0043] The diameter of the distributor outlet connections can be from 1 to 10 millimeters. In a preferred embodiment, the diameter of the distributor outlet connections can be from 2 to 4 millimeters.

[0044] The first inclined rotating surface 106 is located downstream of the distributor. The first inclined rotating surface 106 is preferably a cone or a conical section, wherein the outer surface has a first inner apex angle α ranging from 30 to 150 degrees, preferably 60 to 120 degrees. The first inclined rotating surface 106 has an outer upper surface 107 that is convex and an opposing inner surface that is concave. The apex angle α is the inner apex angle at the concave inner surface. The outer surface of the first inclined rotating surface 106 faces the upper inner surface of the outer shell 102, with its apex pointing towards the inlet port 101. While the inclined surface 106 can be defined by a straight line extending from the apex to the edges, the inclined surface can also be curved.

[0045] The first inclined rotating surface 106 contacts a first shaft 117, which is in rotary connection with a motor (not shown). The rotary motion transmitted from the motor to the first shaft 117 is transferred to the first inclined rotating surface 106. This rotary motion exerts a centrifugal force on the molten material, subjecting it to initial comminution to form the fine particles. This initial comminution can be considered the first stage in the formation of the ultrafine particles.

[0046] The upper outer surface 107 is a textured surface with grooves and indentations that facilitates the comminution of the molten material that comes into contact with it after being dispensed from the distributor. The underside 111 of the first inclined rotating surface is provided with a non-stick coating. The non-stick coating is able to withstand the temperature of the molten material without melting or decomposing itself. The non-stick coating can be a polymer and / or a ceramic to prevent the molten material from adhering to the surface. Examples of non-stick polymers are fluorocarbons (e.g., Teflon), polysiloxanes, polyimide polysiloxanes, or a combination thereof.Anodized aluminum, enamelled cast iron, and superhydrophobic surfaces (surfaces with a texture exhibiting a contact angle of 90 to 140 degrees) can also be used for the non-stick properties of the base 111. The non-stick coating enables rapid discharge of the material particles from the first inclined rotating surface 106 to the second inclined rotating surface 108, from which the particles are conveyed to the outlet port 121 of the multi-stage centrifugal atomizer 100. The non-stick coating also prevents the molten material from agglomerating into larger particles.

[0047] The second inclined rotating surface 108 is located downstream of the first inclined rotating surface 106. The second inclined rotating surface 108 is preferably an inverted cone or an inverted conical section, wherein the inner surface has a second inner vertex angle β that is larger than the first inner angle α. The second inner vertex angle β ranges from 90 to 180 degrees, preferably 120 to 170 degrees. The second inclined rotating surface 108 has an outer lower surface 115 that is convex and an opposing inner surface that is concave. The vertex angle β is the inner vertex angle at the concave inner surface. The outer surface of the second inclined rotating surface 108 is opposite the lower inner surface of the outer shell 102, with its vertex (which may be an imaginary point formed by extending the outer surfaces 108) pointing towards the outlet port 121.While the inclined surface 108 can be defined by a straight line running from the vertex to the edges, the inclined surface can also be curved.

[0048] The upper inner surface 113 of the second inclined rotating surface 108 is also provided with a non-stick coating. In one embodiment, the angle γ between the upper inner surface 113 and the outer lower surface 115 of the second inclined rotating surface 108 varies from 90 degrees to 180 degrees, preferably from 135 to 158 degrees. This angle facilitates the comminution of the molten material into smaller particle sizes.

[0049] The non-stick coating materials described above can be used. The non-stick coating prevents the particles discharged from the first inclined rotating surface from agglomerating into larger particles on the upper inner surface 113. The ultrafine particles that form upon contact with the second inclined rotating surface 108 are discharged from the second inclined rotating surface 108 via the stream 128, collect at the bottom of the inner surface, and are discharged by gravity via the outlet port 121 into a storage container (not shown).

[0050] The second inclined rotating surface 108 contacts a second shaft 119, which is in rotational connection with the motor (not shown). The rotational motion transmitted from the motor to the second shaft 119 is transferred to the second inclined rotating surface 108. This rotational motion exerts a centrifugal force on the particles formed in the first comminution, subjecting them to a second comminution to form the ultrafine particles. This second comminution can be considered the second stage in the formation of the ultrafine particles.

[0051] While Fig. 1 if the lower perimeter 302 of the first inclined rotating surface 106 is above an imaginary plane formed at the upper perimeter 304 of the second inclined rotating surface 108, it is possible that the lower perimeter 302 projects into the open space below the imaginary plane formed at the upper perimeter 304.

[0052] In a Fig. In the embodiment shown in 2A, the first shaft 117 and the second shaft 119 are arranged concentrically around an axis (they are coaxial), and both shafts can be rotated by a rotary motion imposed on them by the same motor. Fig. 2A shows parts of the device Fig. 1, excluding the outer casing and the distributor. Fig. Figure 2A shows the arrangement of the shafts used to drive the first and second inclined rotating surfaces 106 and 108. Fig. Figure 2B is an enlarged view of the arrangement of waves with a key that ensures that the same vertical motion is exerted on the inclined surfaces by a piezoelectric stack (described later). Fig. Figure 2B shows how the vertical motion generated by the piezoelectric stack can be restricted so that there is no variation in the vertical motion through the first inclined rotating surface 106 and the second inclined rotating surface 108.

[0053] With regard to the Fig. 1 and Fig. 2A The coaxial arrangement facilitates the introduction of independent rotational speeds for the different inclined rotating surfaces 106 and 108. In one embodiment, the first shaft 117 and the second shaft 119 can be rotated by a rotary motion transmitted by two separate motors (represented by arrows numbered 602 and 604). In another embodiment, a single motor with two gearboxes can be used to drive the two shafts at different rotational speeds. The first shaft 117 and the second shaft 119 (and consequently the first inclined rotating surface 106 and the second inclined rotating surface 108, respectively) can rotate in the same direction or, alternatively, if desired, in opposite directions. In a preferred embodiment, both the first shaft 117 and the second shaft 119 can rotate in the same direction.Rotation in the same direction helps to accelerate the molten material and increase its kinetic energy if the adhesion / friction between the surface of the rotating disk and the molten material is high enough (and no "slippage" occurs).

[0054] On one or both shafts 117 and 119 (see Fig. 2A) A piezoelectric stack 602 is located, which promotes the vertical movement of the first inclined rotating surface 106 and / or the second inclined rotating surface 108 relative to each other. An ultrasonic transducer (not shown) contained in the piezoelectric stack 602 transmits ultrasonic energy along arrow 504 (back and forth – vertical information) either to wave 117, wave 119, or to both waves 117 and 119. In one embodiment, the piezoelectric stack 602 is in vertical (back and forth) communication with a single wave – wave 119 (which is in communication with the second inclined rotating surface 108).

[0055] Fig. Figure 2B shows an embodiment of the relationship between the first shaft 117 and the second shaft 119. The first shaft 117 contains a key 320 which contacts two stops 322 and 324 provided by a slot 321 in the second shaft 119.

[0056] The rotation ratio of the first shaft 117 to the second shaft 119 (and consequently of the first inclined rotating surface 106 to the second inclined rotating surface 108) can vary from 0.1:1 to 1:0.1. In a preferred embodiment, the rotation ratio of the first shaft 117 to the second shaft 110 is 1:1.

[0057] Fig.Figure 3 shows an exemplary arrangement of the gears that can be used to rotate the respective shafts 117 and 119 and to introduce ultrasonic energy into the molten material. A motor 502 is in rotary connection with a gear 506. The gear 506 is located in a bevel gear arrangement with two gears 402 and 406, which in turn are in rotary connection with the shafts 119 and 117. The rotary motion is thus transmitted from the motor 502 via the gears 506, 406, and 402 to the shafts 117 and 119. An ultrasonic transducer (not shown) transmits ultrasonic energy in the direction of arrow 504 either to wave 117, wave 119, or to both waves 117 and 119. The transducer, together with an optional integrated mechanical amplifier (not shown), can generate a linear back-and-forth motion of up to 50 micrometers at 20 kHz or more.The presence of an ultrasonic transducer contributes to finer particle sizes, as the acceleration is very high, and suppresses deposit formation (particles form an agglomeration on the inclined rotating surfaces).

[0058] The ultrasonic transducer generates a linear back-and-forth motion either in wave 117, wave 119 or in both waves 117 and 119, which facilitates the comminution and deagglomeration of the ultrafine particles.

[0059] In a process for producing ultrafine particles with a D50 of less than 20 micrometers, the molten material, comprising a metal, ceramic, polymer, or combinations thereof, is first poured into the distributor via the atomizer inlet and the distributor inlet. In a first stage, the molten material is discharged from one or more of the distributor outlets onto the first inclined rotating surface. The centrifugal forces of this first inclined rotating surface cause some comminution of the molten material into particles. In a second stage, these particles are discharged from the first inclined rotating surface to the second inclined rotating surface, where they are further comminuted to form the ultrafine particles. The ultrafine particles are then discharged from the atomizer outlet into a storage container.It should be noted that the first and second stages of comminution can be performed simultaneously, even if the molten material is subjected to the second stage after the first. The molten material can be exposed to ultrasonic energy during the first stage, the second stage, or both simultaneously.

[0060] In one embodiment, in a method for manufacturing the multi-stage centrifugal atomizer, the distributor is first fixed to the inside of the atomizer's outer shell. The atomizer's outer shell may have an upper and a lower section. The distributor is attached to the upper section of the outer shell. The first shaft and the second stage are mounted coaxially (concentrically), with one end located within the atomizer's outer shell and the other end connected to a set of gears mounted in a bevel gear assembly. The bevel gear assembly is in rotary engagement with the motor, which drives the rotation of the rotating inclined surfaces.After the waves are arranged in the outer shell, the second inclined rotating surface is attached to one wave (the first or the second wave), while the first inclined rotating surface is attached to the other wave, which is not connected to an inclined rotating surface.

[0061] The multi-stage centrifugal atomizer has the advantage of producing a monodisperse particle distribution. The particle distribution is very narrow (with a polydispersity index of less than 1.2) and has an average particle size, with D50 being less than 20 micrometers. The particles have a spherical shape, a narrow particle size distribution, and a homogeneous composition, and can therefore be used in automotive and non-automotive (energy, aerospace, marine, etc.) industrial applications. The process is also much faster compared to conventional, commercially available centrifugal atomizers. In short, the atomizer presented here can produce larger quantities of better particles in less time compared to commercially available centrifugal atomizers.

[0062] The multi-stage centrifugal atomizer disclosed herein can be used for gas / water atomization and in applications where the morphology, purity, and particle size distribution are less restrictive. Slippage (which adversely affects the comminution of molten material) can occur in a single-stage atomizer, but this can be avoided by the multi-stage acceleration disclosed here.

Claims

[1] Multi-stage centrifugal atomizer (100), comprising: an outer shell (102) which includes an inlet port (101) and an outlet port (121) and which comprises: a distributor (104), a first inclined rotating surface (106); and a second inclined rotating surface (108); wherein the first inclined rotating surface (106) is arranged opposite the second inclined rotating surface (108); wherein the inlet is used to introduce a molten material into the multi-stage atomizer, and wherein the outlet is used to remove ultrafine particles with a D50 of less than 20 micrometers; and wherein a convex surface of the first inclined rotating surface (106) faces the inlet of the multi-stage centrifugal atomizer (100) and wherein a convex surface of the second inclined rotating surface (108) faces the outlet of the multi-stage centrifugal atomizer (100) and wherein the first inclined rotating surface (106) serves to receive a molten material from the distributor (104) and to discharge the molten material in the form of particles, wherein the second inclined rotating surface (108) serves to receive the particles from the first inclined rotating surface (106) and to reduce them to a smaller particle size than that which is received from the first inclined rotating surface (106). [2] Multi-stage centrifugal atomizer (100) according to claim 1, wherein an angle γ between an upper inner surface (113) and the outer lower surface (115) of the second inclined rotating surface (108) varies between 90 degrees and 180 degrees. [3] Multi-stage centrifugal atomizer (100) according to claim 1, wherein a first shaft (117) contacting the first inclined rotating surface (106) and a second shaft (119) contacting the second inclined rotating surface (108) are mounted coaxially and are in rotary connection with a motor (502). [4] Multi-stage centrifugal atomizer (100) according to claim 3, wherein the first inclined rotating surface (106) is a cone or a conical section and wherein the second inclined rotating surface (108) is a cone or a conical section and wherein a convex surface of the first inclined rotating surface (106) faces the inlet port (101) and wherein a convex surface of the second inclined rotating surface (108) faces the outlet port (121). [5] Multi-stage centrifugal atomizer (100) according to claim 4, wherein the first inclined rotating surface (106) has an interior angle that is smaller than the interior angle of the second inclined rotating surface (108), and wherein the convex surface of the first inclined rotating surface (106) has a section that is structured with grooves and patterns to facilitate the comminution of a molten material that comes into contact with it. [6] Multi-stage centrifugal atomizer (100) according to claim 5, wherein the convex surface of the first inclined rotating surface (106) has a section with non-stick properties and wherein a concave surface of the second inclined rotating surface (108) has a section structured with grooves and patterns to facilitate the comminution of a molten material that comes into contact with it. [7] Multi-stage centrifugal atomizer (100) according to claim 1, further comprising an ultrasonic transducer which is operatively connected either to the first inclined rotating surface (106), the second inclined rotating surface (108) or to both the first inclined rotating surface (106) and the second inclined rotating surface (108), and wherein the ultrasonic transducer provides a linear reciprocating motion of up to 50 micrometers at 20 kHz or more on the first inclined rotating surface (106), the second inclined rotating surface (108) or to both the first inclined rotating surface (106) and the second inclined rotating surface (108). [8] Procedures, comprehensive: Introducing a molten material into an inlet port (101) of a multi-stage centrifugal atomizer (100), wherein the multi-stage centrifugal atomizer (100) comprises: an outer shell (102) which includes an inlet port (101) and an outlet port (121) and which comprises: a distributor (104), a first inclined rotating surface (106); and a second inclined rotating surface (108); wherein the first inclined rotating surface (106) is arranged opposite the second inclined rotating surface (108); wherein the inlet is used to introduce a molten material into the multi-stage atomizer, and wherein the outlet is used to remove ultrafine particles with a D50 of less than 20 micrometers; wherein a convex surface of the first inclined rotating surface (106) faces the inlet of the multi-stage centrifugal atomizer (100) and wherein a convex surface of the second inclined rotating surface (108) faces the outlet of the multi-stage centrifugal atomizer (100) and wherein the first inclined rotating surface (106) serves to receive a molten material from the distributor and to discharge the molten material in the form of particles, wherein the second inclined rotating surface (108) serves to receive the particles from the first inclined rotating surface (106) and to reduce them to a smaller particle size than that received from the first inclined rotating surface (106); Conveying the molten material from the distributor (104) onto the first inclined rotating surface (106) to form particles; and Transporting the particles from the first inclined rotating surface (106) to the second inclined rotating surface (108) to form the ultrafine particles. [9] The method of claim 8 further comprising exposing either the first inclined rotating surface (106), the second inclined rotating surface (108) or both the first inclined rotating surface (106) and the second inclined rotating surface (108) to an ultrasonic vibration.

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