Centrifugal separator comprising a centrifuge drum with metallic corrosion protection layer, centrifuge drum and method for providing same

Abstract

A centrifugal separator (1) comprising a rotatably mounted centrifuge drum (5) with at least one drum component comprising a metallic drum wall (14), wherein the drum component at least partially delimits a centrifuge interior (17), characterized in that the drum wall (14) is coated with a metallic corrosion protection layer (13) which is metallurgically bonded to the drum wall (14); wherein the entire centrifuge interior (17) is delimited by the corrosion protection layer (13), wherein the centrifuge interior (17) is completely and without gaps delimited by the corrosion protection layer and wherein the corrosion protection layer is pore-free, as well as a centrifuge drum and a method for providing a centrifuge drum.

Description

[0001] The present invention relates to a separator with a corrosion-resistant centrifuge drum, as well as a centrifuge drum and a method for providing it.

[0002] Centrifuge drums are often manufactured from forged steel components. A centrifuge drum typically comprises at least a drum base and a drum cover.

[0003] For many years, the applicant has been providing a corrosion-resistant centrifuge drum as a special product, which is designed, for example, as a drum of a solid jacket separator and which is fitted on the inside with a sheet of a more corrosion-resistant material compared to the base material of the drum wall.

[0004] The sheet metal in question is placed inside the centrifuge chamber and shaped to the inner contour of the centrifuge drum through several forming steps. Particular attention must be paid to ensuring absolute tightness so that no product can get between the sheet metal and the drum wall. Furthermore, the sheet metal must be applied so uniformly that no excessive imbalance occurs during normal centrifuge operation.

[0005] This internally lined centrifuge drum has generally proven its worth, but is comparatively complex to manufacture.

[0006] Moreover, existing lining solutions are limited to simple centrifuge drum geometries. For example, sheet metal lining in the area of ​​solids outlets of nozzle drums or drums of self-emptying separators, while ensuring the tightness of these areas, proves particularly challenging.

[0007] Based on this, the object of the present invention is to provide an alternative to sheet metal lining which is applicable to a wider range of centrifuge drums.

[0008] The present invention solves this problem by providing a centrifugal separator with the features of claim 1.

[0009] A centrifugal separator according to the invention comprises a rotatably mounted centrifuge drum with at least one drum component comprising a metallic drum wall. The drum component defines at least a portion of the centrifuge interior. The drum wall is coated with a metallic corrosion protection layer, which is bonded to the drum wall. Such a centrifugal separator can be designed as a chamber separator, nozzle separator, self-emptying separator, solid-jacket separator, or decanter.

[0010] The metallic corrosion protection layer creates a materially bonded connection zone between the base material of the drum wall and the material of the corrosion protection layer.

[0011] The bonding zone can have a preferred average thickness of less than 15 µm, preferably of about 5-10 µm. In particular, the average thickness of this zone is less than the thickness of the applied corrosion protection layer, so that the corrosion protection layer completely and without gaps covers the drum wall.

[0012] According to the invention, the corrosion protection layer is pore-free. In particular, the corrosion protection layer is also free of cavities.

[0013] Due to the nature of the aforementioned metallurgical bond, undermining or creeping behind the coating is impossible. At the same time, a metallic corrosion protection layer, for example, due to metallic ductility and the molecular lattice structure of a metal, is better suited for corrosion protection against thermal or mechanically induced expansion of the drum wall than non-metallic protective coatings.

[0014] Further advantageous embodiments of the invention are the subject of the dependent claims.

[0015] The drum component can advantageously be designed as a drum base or a drum cover. In decanters, the drum component can also be a drum cylinder.

[0016] The corrosion protection layer is particularly advantageous if it extends at least along all product-contacting areas of the drum component on the metallic drum wall.

[0017] According to the invention, the entire interior of the centrifuge is bounded by the corrosion protection layer.

[0018] The average thickness of the corrosion protection layer can be more than 15 µm, preferably 20-4000 µm, particularly preferably 25-1000 µm.

[0019] It is advantageous if the drum wall is made of a steel material and if the corrosion protection layer has a greater corrosion resistance, in particular a passive layer with greater corrosion resistance, than the drum wall or the base material from which the drum wall is formed.

[0020] The metallic coating can be elemental or a metal alloy based on nickel, titanium, and / or zirconium. The aforementioned components form the main part of the metal alloy.

[0021] The metallic coating can alternatively be elemental or a metal alloy based on aluminum, copper, cobalt, and / or tin. However, these coating systems are somewhat less preferred than the aforementioned nickel, titanium, and / or zirconium coatings due to reduced mechanical stability.

[0022] To improve the mechanical stability of the coating, it may contain hard metals, in particular a composite phase of the aforementioned metals or metal alloys with a carbide compound, as a so-called hard material.

[0023] Furthermore, the mean roughness Ra of a drum inner surface formed by the corrosion protection layer can preferably be between 0.1-20 µm, preferably between 0.15-5 µm, so that corrosive product residues adhere to the drum wall only to a small extent.

[0024] The base material of the drum wall can advantageously be a steel material, in particular a stainless steel material, preferably a 1.4501 or a 1.4418 or a 1.4462 material.

[0025] A preferred form of a separator according to the invention is a chamber separator, a nozzle separator, a self-emptying separator, a solid-jacket separator, or a decanter. With the previous variant of a metallic sheet lining, it was not possible to provide a drum with a complex geometry with a media-tight, corrosion-protective metallic inner surface.

[0026] Furthermore, according to the invention, a centrifuge drum of a centrifugal separator according to the invention is provided. This is preferably a centrifuge drum with a capacity of more than 10 liters, which is preferably designed for continuous operation with a force of more than 10,000 g (1 g = 9.81 m / s²) in the area of ​​the drum wall. Such centrifuges are subject to different mechanical stresses than, for example, a laboratory centrifuge.

[0027] Furthermore, according to the invention, a method for providing a centrifuge drum of a centrifugal separator according to the invention comprises at least the following steps: a. Providing one or more drum components with product-contacting surfaces which, in the assembled state, define a drum interior, and b. Applying a coating material to at least one of the product-contacting surfaces to form a corrosion protection layer by means of a cladding welding process, or by means of a laser cladding welding process, in particular by means of an EHLA laser cladding welding process, c. Assembling the drum parts, e.g. the drum base and the drum cover, into a centrifuge drum by providing the drum interior.

[0028] Further embodiments of the method according to the invention are the subject of the dependent claims.

[0029] The preferred layer thickness can be advantageously adjusted within the framework of the inventive method by controlling the laser power, the powder feed rate, the welding speed, the area rate, and / or the gas flow rate of a carrier gas. A thin yet dense layer thickness is the objective of the method. Imbalances or uneven distributions of the coating must be avoided.

[0030] It is advantageous if, following the application in step b), the inner surface of the drum is machined, ground, smoothed and / or polished, so that the remaining corrosive medium on the surface is also avoided.

[0031] Furthermore, it is advantageous if, after application in step b) and possibly after smoothing and / or polishing, a dye penetrant test is carried out as a leak test of the corrosion protection layer.

[0032] The invention will now be explained in more detail using an exemplary embodiment and the accompanying figures. These show: Fig. 1 schematic representation of an embodiment of a centrifugal separator according to the invention; and Fig. 2 block diagram of a process scheme for carrying out a manufacturing process according to the invention.

[0033] Centrifugal separators, such as chamber separators, nozzle separators, self-emptying centrifuges, solid jacket centrifuges and decanters, are machines that are often exposed to extreme stresses from corrosion and chemical attack in industry.

[0034] These machines are used, for example, in areas such as food processing, chemistry, pharmaceuticals, biotechnology, wastewater treatment, marine industries, or oil refining.

[0035] Due to high mechanical stresses and corrosive environments, protective coatings are often required to extend the service life of components and reduce maintenance costs. These coatings have primarily been plastic-based, for example, in the form of linings or coatings. However, the adhesion of these compounds to the metallic surface of separators is not optimal. In most cases, the coating is held to the metallic surface only by physisorption effects. A true, material-bonded connection along the substrate material surface does not exist. This can lead to creep behind these protective coatings. The present invention addresses this issue.

[0036] Fig. 1Figure 1 shows a centrifugal separator 1 with a product inlet 2 and two product outlets 3, 4 for two liquid phases with different densities. The core component of the centrifugal separator 1 is a rotatably mounted centrifuge drum 5. In the illustrated version, the centrifuge drum 5 rotates about a vertical axis of rotation Z. This axis is set in motion by a drive spindle 6 via a motor (not shown). The motor can be connected to the drive spindle 6 via a direct drive, a geared drive, or a belt drive.

[0037] The product inlet 2 comprises an inlet pipe which extends into a distributor 11. This is arranged coaxially to the axis of rotation Z.

[0038] In distributor 11, the product spreads radially and is then transferred to the centrifuge interior or drum interior 17. Within the centrifuge interior 17, the product is separated in the centrifugal field, preferably at several thousand grams, into a light liquid phase and a heavier liquid phase. The light liquid phase is discharged radially inside via a gripper 9 and transferred to the product outlet 3.

[0039] To maximize the separation area, the separator 1 has one or more separating plates 7 inside the centrifuge interior 17, which preferably form a conical plate pack.

[0040] The heavy phase is discharged from the centrifuge interior 17 via a separating plate 8. It is discharged from the centrifuge drum 5 via a gripper 10 and transferred to the product outlet 4.

[0041] The centrifuge interior 17 is bounded by two drum components, a lower drum part 15 and an upper drum part 16, which are tightly connected to each other via an interface 18. The connection can be made, for example, by a screw connection or the like.

[0042] The drum components each have a drum wall 14, which is designed to be correspondingly robust for mechanical stability against accelerations of more than 10,000 g in the area of ​​the drum wall.

[0043] The drum wall 14 consists of a metallic base material, for example, super duplex steel – specifically material 1.4501. This base material already exhibits a certain degree of corrosion resistance, which is further enhanced by the corrosion protection layer. The drum component, either the drum base or the drum cover, can be a forged component. This offers excellent properties for the high mechanical loads encountered in the application.

[0044] Alternatively, the drum wall 14 can be made from an already corrosion-resistant base material, e.g., material 1.4418. In the area of ​​materials, a distinction is made between corrosion-resistant and highly corrosion-resistant metallic materials.

[0045] According to the invention, the drum wall 14 or the wall base material has a metallic corrosion protection layer 13. Effective corrosion protection of the wall base material can be achieved, among other things, by using a metallic coating material that forms a passive layer on oxygen.

[0046] The coating applied to the wall base material preferably consists of a highly corrosion-resistant metallic material or at least of a material with higher corrosion resistance than the wall base material of the drum wall 14.

[0047] The composition of the coating can be adapted to the requirements of the respective separation process. This allows coating materials with a wide variety of compositions to be applied.

[0048] In a preferred embodiment, the metallic coating can be elemental or a metal alloy based on nickel, titanium, and / or zirconium. These metals form a water-insoluble passive layer and protect the underlying metallic materials from corrosion.

[0049] Aluminum, copper, cobalt and / or tin-based alloys can also be advantageously used as coating materials. Alternatively or additionally, the coating can also include hard metals.

[0050] Additionally, the coating may also contain wear-resistant materials such as chromium carbide, vanadium carbide, tungsten melt carbide, cobalt and / or tungsten titanium carbides or mixed carbides made from the aforementioned compounds.

[0051] It is also possible to apply highly corrosion-resistant steel materials to the drum wall. The steel materials can preferably be unalloyed and / or low-alloy, or in the form of duplex and / or austenitic steel.

[0052] In any case, due to the passivation of the surface, the metallic corrosion protection layer 13 exhibits a significantly lower tendency towards pitting corrosion or stress corrosion cracking and the like than the underlying wall base material of the drum wall 14.

[0053] Particularly preferably, all product-contacting surfaces 12 of the respective drum component, especially the drum lower part 15 or the drum lid 16, are provided with the coating 13. According to the invention, this is done such that the centrifuge interior 17 defined by the drum is completely bounded or enclosed by the metallic corrosion protection layer 13 towards the product.

[0054] Only optionally, drum components within the centrifuge drum 5, e.g. an internally arranged distributor wall of the distributor 11, can also be provided with a metallic corrosion protection layer 13.

[0055] The application of the metallic corrosion protection layer 13 can be carried out using a method as described in Fig. 2 is shown.

[0056] The first step, 101, involves providing a metallic drum component. This may have been manufactured through a forging process and finished through further processing steps such as machining, grinding and / or polishing.

[0057] In a second step, the corrosion protection layer can be applied directly to the component—in this case, the inner wall of the drum—using a suitable coating process. This can be done by cladding, preferably by laser cladding, and particularly preferably by an EHLA (Extreme High-Speed ​​Laser Cladding) process. The coating is applied by locally melting the substrate (base material) using optically focused laser radiation and simultaneously introducing a powdered, corrosion-resistant filler material. However, other cladding processes are also applicable.

[0058] Extreme High-Speed ​​Laser Cladding (EHLA) is an advancement of conventional laser cladding, in which a metal powder or wire is applied to a substrate surface using a laser beam to create a protective or performance-enhancing layer. In this coating process, the powder is guided into the focused laser beam before it even touches the molten substrate, so that the powder material is already molten before impacting the locally melted substrate material. The coating droplets solidify instantly upon contact with the substrate. This results in a very shallow melt pool on the surface with few inclusions, minimal porosity, an increased solidification rate, and a defined mix after solidification.Due to the lower heat input and faster solidification, diffusion and mixing effects occur only to a very limited extent. The formation of a defined dilution zone with a thickness of less than 15 µm, preferably about 5–10 µm, and a preferred layer thickness between 20–1000 µm, enables the formation of comparatively thin, closed, and therefore dense layers. At the same time, the lower heat input significantly increases the speed of laser cladding. This significant increase in process speed compared to other laser cladding processes results not only in shorter processing times but also in improved layer properties with reduced material usage.

[0059] While conventional laser cladding typically operates at speeds in the range of 0.5 to 2 m / min, EHLA achieves speeds of up to 500 m / min. This results in a drastic reduction in processing time.

[0060] Unlike the traditional method, where the powder is only melted after impact with the surface, in EHLA the powder melts completely while suspended above the substrate surface. This modification reduces heat input into the component and enables the processing of temperature-sensitive materials.

[0061] Improved heat input control and precise powder flow regulation enable the application of very thin layers, typically between 25 and 250 µm. This significantly reduces the need for post-processing, e.g., to improve surface finish.

[0062] Because the powder is used more efficiently and melts completely before contacting the substrate, the coating material can be applied very precisely and evenly. This reduces material waste and increases overall efficiency.

[0063] The material application for the formation of the corrosion protection layer, and thus the layer thickness, can be varied based on one or more of the following parameters: a) the laser power b) the powder feed rate c) the welding speed d) the area rate e) the gas flow rate of a carrier gas

[0064] The laser power, i.e. the amount of energy supplied to the powder and the wall base material, can be selected between a few hundred and a few thousand watts to adjust the layer thickness.

[0065] Furthermore, the layer thickness can be adjusted by the amount of powder applied. The powder feed rate also determines the homogeneity of the coating. The powder feed rate can be controlled and adjusted by a powder conveying system.

[0066] The laser's welding speed influences the deposition rate and thus the layer thickness. The preferred welding speed can be selected as a setpoint from a preferred range between 100 and 500 m / min, which is significantly higher than with conventional methods.

[0067] The area rate describes the amount of material applied to a specific area per unit of time. For the present process, the preferred area rate is typically around 250 to 500 cm² / min, which is also significantly higher than the values ​​for conventional laser cladding.

[0068] The gas flow, usually an inert gas such as argon or helium, serves both to protect the melt pool from oxidation and to cool it. The choice of gas and the flow rate can be adjusted depending on the material and application.

[0069] After the molten pool has solidified, the corrosion protection layer 13 forms on the surface, which has better corrosion properties, e.g. by forming a passive layer, and possibly also better wear properties than the wall base material of the partition wall 14.

[0070] The composition of the welding filler material can be adapted to the requirements of the centrifuge drum and the separation process it performs. This allows for the application of coating materials with a wide variety of compositions. The coating materials are preferably selected from powdered materials based on nickel, titanium, or zirconium, with additives of wear-resistant materials such as chromium carbides, vanadium carbides, tungsten carbides, cobalt carbides, tungsten titanium carbides, etc., as well as steel materials (unalloyed / low-alloy) such as duplex or austenitic steel.

[0071] Overall, Extreme High-Speed ​​Laser Cladding (EHLA) enables the application of high-quality, thin layers that are metallurgically bonded to the substrate material. Ideally, coatings with a thickness of less than 300 µm, preferably even less than 100 µm, can be "dense" and thus reliably protect the base material from corrosion. However, the EHLA process can also easily produce layers thicker than 4000 µm with comparatively low heat input. The thin coating also has a positive effect on component distortion. The thermal impact on the substrate material (HAZ) is only in the micrometer range with this process. This also makes corrosion-resistant coatings for heat-sensitive components possible.

[0072] In addition to the criteria mentioned above, the application process described above ensures high-quality adhesion of the coating to the substrate, thus preventing safety risks during operation (e.g., imbalance at high speeds). This also prevents corrosive media from penetrating the protective layer (as was previously the case with coatings).

[0073] In addition, laser cladding, which includes the aforementioned EHLA process, offers manufacturing advantages for complex drum geometries. The development of laser and robot systems has progressed to the point where automated processing of complex drum geometries is now possible. This significantly increases the reproducibility of the drum coating and allows for further advantages beyond those already mentioned. Fig. 1The separators shown, with their comparatively simple geometries, can now also be provided with a corresponding corrosion protection layer 13 for nozzle separators, self-emptying drums, decanter drums, solid-jacket drums, chamber drums, and the like. This was previously not possible with sheet metal linings, partly due to the yield strength of the sheet metal. The range of centrifuge drums that can be coated according to the invention therefore increases significantly.

[0074] After the application of the corrosion protection layer 13 as a continuous coating, it is mechanically reworked, e.g., by machining, grinding, polishing, and / or smoothing 103, to achieve a preferred layer thickness. Depending on the requirements, this thickness can range from 20 to 4000 µm. This can be achieved through machining, grinding, and / or polishing operations. After mechanical processing, the surface finish, depending on the specification, has a mean roughness value (Ra) between 0.1 and 20 µm, preferably between 0.15 and 5.0 µm. The mean roughness value can be determined optically using commercially available measuring instruments according to DIN ISO 21320.

[0075] In the prior art, metal inserts or localized coatings are known that counteract abrasion in the area of ​​the solids discharge openings. The invention goes a step further. The corrosion protection layer not only seals the drum against contact with the medium, but also allows the heavier phase to drain and slide along the inner wall of the centrifuge, thus improving removal. As can be seen from the design of the [unclear] in the Figure 1 As the separator shown, the separated heavy phase is guided upwards along the inside of the centrifuge drum to a gripper. A surface roughened by the coating would impede this flow. Therefore, the surface roughness after the coating process can be adjusted to a target value within the aforementioned range by post-processing such as grinding, polishing, smoothing, and / or machining.

[0076] A leak test of the corrosion protection layer, using a non-destructive testing method such as dye penetrant testing, can then be performed to verify whether the coating is flawless, i.e., completely sealed. This effectively eliminates crevice corrosion.

[0077] Finally, in a further step of post-processing 104, the individual elements of the drum coated in this way, such as the drum lower part and the drum upper part, are balanced and checked for concentricity.

[0078] For centrifugal separators that are used exclusively for one application, the corrosion protection layer can be tailored to the application in terms of material and layer thickness.

[0079] Further design freedoms in manufacturing arise from the fact that the base material of the drum wall no longer needs to meet specific corrosion protection requirements, as this is provided by the corrosion protection layer. This allows the use of drum wall materials with different tensile and compressive strengths, which previously could not be used in the design of centrifuge drums due to insufficient corrosion resistance. Reference sign

[0080] 1 Separator 2 Product inlet 3 Product outlet 4 Product outlet 5 Centrifuge drum 6 Drive spindle 7 Separating plate 8 Separating plate 9 Gripper 10 Gripper 11 Distributor 12 Product contact surface 13 Corrosion protection layer or coating 14 Drum wall 15 Drum base 16 Drum top or drum cover 17 Centrifuge chamber 18 Interface 101 Providing a metallic drum component 102 Applying the corrosion protection coating 103 Machining, grinding, polishing and / or smoothing 104 Post-processing by balancing

Claims

1. Centrifugal separator (1) comprising a rotatably mounted centrifuge drum (5) with at least one drum component comprising a metallic drum wall (14), wherein the drum component at least partially defines a centrifuge interior (17), characterized by the fact that the drum wall (14) is coated with a metallic corrosion protection layer (13) which is bonded to the drum wall (14) in a materially bonded manner, that the entire interior of the centrifuge (17) is bounded by the corrosion protection layer (13), that the centrifuge interior (17) is completely and seamlessly enclosed by the corrosion protection layer and that The corrosion protection layer is pore-free.

2. Centrifugal separator according to claim 1, characterized by the fact that the mean thickness of the corrosion protection layer (13) is more than 15 µm, preferably 20-4000 µm, particularly preferably 25-1000 µm.

3. Centrifugal separator according to claim 1 or 2, characterized by the fact that the drum wall (14) is made of a steel material and that the corrosion protection layer (13) has a greater corrosion resistance, in particular a passive layer with a greater corrosion resistance, than the drum wall (14).

4. Centrifugal separator according to any one of the preceding claims, characterized by the fact that the metallic corrosion protection layer (13) is formed in elemental form or as a metal alloy based on nickel, titanium and / or zirconium.

5. Centrifugal separator according to any one of the preceding claims, characterized by the fact that the metallic corrosion layer (13) is formed in elemental form or as a metal alloy based on aluminium, copper, cobalt and / or tin.

6. Centrifugal separator according to any one of the preceding claims, characterized by the fact thatthe corrosion protection layer (13) comprises hard metals, in particular a composite phase of the aforementioned metals or metal alloys with a carbide compound.

7. Centrifugal separator according to any one of the preceding claims, characterized by the fact that the mean roughness Ra of a drum inner surface formed by the corrosion protection layer (13) is between 0.1-20 µm, preferably 0.15 - 5.0 µm.

8. Centrifugal separator according to any one of the preceding claims, characterized by the fact that the base material of the drum wall (14) is a steel material, preferably 1.4501 or 1.4418 or 1.4462 material.

9. Centrifugal separator (1) according to any of the preceding claims in the form of a chamber separator, nozzle separator, self-emptying separator, decanter or a solid jacket centrifuge.

10. Centrifuge drum (5) of a centrifugal separator (1) according to one of the preceding claims, preferably with a capacity of more than 10 liters and preferably designed for continuous operation with more than 10,000 g in the area of ​​the drum wall.

11. Method for providing a centrifuge drum (5) of a centrifugal separator (1) according to one of the preceding claims at least characterized by the following steps:a. Providing (101) one or more drum components with product-contacting surfaces (12) which, when assembled, define a centrifuge interior (17), and b. Applying (102) a coating material to at least one of the product-contacting surfaces (12) to form a corrosion protection layer (13) by a cladding process, or by a laser cladding process or by an EHLA laser cladding process, c. Assembling the drum components to form a centrifuge drum (5) by providing the centrifuge interior (17).

12. Method according to claim 11, characterized by the fact that the thickness of the corrosion protection layer (13) is adjusted by controlling the laser power, the powder feed rate, the welding speed, the area rate and / or the gas flow rate of a carrier gas.

13. Method according to claim 11 or 12, characterized by the fact thatFollowing the order in step b), machining, grinding, smoothing and / or polishing (103) of the inner surface of the drum, in particular to a center roughness according to claim 10, is carried out.

14. Method according to any one of the preceding claims, characterized by the fact that After the application in step b) and, if necessary, after machining, grinding, smoothing and / or polishing (103), a dye penetrant test is carried out as a leak test of the corrosion protection layer (13).

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