A stirring assembly, acidolysis reactor and sulfuric acid method titanium dioxide production device

Abstract

The application provides a stirring assembly, an acidolysis reactor and a sulfuric acid method titanium dioxide production device, and relates to the technical field of stirring. A pair of stirring shafts are arranged side by side, and in the axial projection, the paddle portions of the pair of stirring shafts are overlapped. One stirring shaft is a first stirring shaft, and the other stirring shaft is a second stirring shaft. The paddles of the first stirring shaft are divided into two paddle groups. One paddle group is located at one end of the first stirring shaft, and the other paddle group is located at the other end of the first stirring shaft. One end surface of the paddle is a material receiving surface, and the other end surface of the paddle is a material backing surface. The material receiving surface of the paddle of one paddle group and the material backing surface of the corresponding paddle on the second stirring shaft are close to each other, and the material backing surface of the paddle of the other paddle group and the material receiving surface of the corresponding paddle on the second stirring shaft are close to each other. The application can alleviate the situation of paddle fracture, improve the service life and product stability.

Description

Technical Field

[0001] This application relates to the field of stirring technology, and in particular to a stirring component, an acid hydrolysis reactor, and a sulfuric acid process titanium dioxide production apparatus. Background Technology

[0002] A continuous acidolysis reactor is used to mix powdered titanium feedstock with concentrated sulfuric acid to ensure a complete reaction. To achieve continuous, stable, and safe operation, this reactor is equipped with a stirring system. Stirring ensures rapid and uniform mixing of the solid titanium feedstock and concentrated sulfuric acid, preventing agglomeration and sedimentation; enhances mass and heat transfer, resulting in a uniform temperature within the reactor and preventing localized overheating; and promotes the smooth escape of gases generated during the reaction (such as vapor and trace amounts of sulfur trioxide).

[0003] Typically, powerful mechanical twin-shaft agitators, such as paddle mixers, are used, driven by top-mounted or side-mounted motors and reducers. However, in actual operation, the paddles of twin-shaft agitators are prone to breakage due to the compression of materials. Utility Model Content

[0004] In view of this, the purpose of this application is to overcome the shortcomings of the prior art and provide a stirring component, an acid hydrolysis reactor, and a sulfuric acid process titanium dioxide production apparatus that can alleviate blade breakage and improve service life and product stability.

[0005] This application provides the following technical solution:

[0006] In a first aspect, embodiments of this application provide a stirring assembly, the stirring assembly comprising:

[0007] A pair of stirring shafts are arranged side by side, and the blades of the pair of stirring shafts partially overlap in axial projection; wherein, one of the stirring shafts is a first stirring shaft and the other stirring shaft is a second stirring shaft, and the blades of the first stirring shaft are divided into two blade groups, one blade group is located at one end of the first stirring shaft and the other blade group is located at the other end of the first stirring shaft.

[0008] Furthermore, one end face of the blade is the feeding face, and the other end face of the blade is the back face. The feeding face of the blade in one blade group and the back face of the corresponding blade on the second stirring shaft are close to each other, and the back face of the blade in another blade group and the feeding face of the corresponding blade on the second stirring shaft are arranged close to each other.

[0009] In some embodiments of the first aspect, the gap between the two blade sets defines a buffer zone, and at least one of the blades of the second stirring shaft is located in the buffer zone.

[0010] In some embodiments of the first aspect, the number of blades on the first stirring shaft is even, the number of blades on the second stirring shaft is odd, the blade on the second stirring shaft located in the buffer zone is a middle blade, the number of the middle blade is one, and the two blade groups are symmetrically arranged about the middle blade.

[0011] In some embodiments of the first aspect, all the blades of the second stirring shaft are arranged at equal intervals in the axial direction, and the blades of the same blade group are arranged at equal intervals.

[0012] In some embodiments of the first aspect, the number of blades on the first stirring shaft is N, the number of blades on the second stirring shaft is M, and N = M + 1.

[0013] In some embodiments of the first aspect, the surface of the stirring shaft is provided with a reinforcing layer.

[0014] In some embodiments of the first aspect, a wear-resistant layer is provided on the top of the blade; wherein, in the direction from the top of the blade to the root, the wear-resistant layer includes a plurality of sub-segments, wherein in adjacent sub-segments, the sub-segment closer to the root has a smaller thickness.

[0015] In some embodiments of the first aspect, the wear-resistant layer is a metal cladding layer.

[0016] Secondly, embodiments of this application also provide an acid hydrolysis reactor, the acid hydrolysis reactor including a stirring assembly as described in any of the above embodiments.

[0017] Thirdly, embodiments of this application also provide a sulfuric acid process titanium dioxide production apparatus, which includes the acidolysis reactor as described in the above embodiments.

[0018] The embodiments of this application have the following advantages:

[0019] This application provides a stirring assembly. The core working principle of this assembly lies in optimizing the layout and relative motion of the blades on a pair of parallel stirring shafts, thereby altering the force state and flow pattern of the material within the reactor and significantly reducing abnormal stress acting on the blades. The pair of stirring shafts partially overlap in their axial projection but do not operate synchronously and symmetrically. The blades of the first stirring shaft are divided into two groups, each arranged at one end of the shaft, forming a specific cooperative relationship with the blades on the second stirring shaft. In one cooperative arrangement, the facing surface (the surface that actively pushes the material) of the first stirring shaft blades and the back surface (the passive surface) of the corresponding blades on the second stirring shaft are close to each other. This allows the blades of the first stirring shaft to act as the main driving blades, shearing and pushing the material first, while the corresponding blades of the second stirring shaft mainly play a supporting role in stirring and receiving the already flowed material. In the other cooperative arrangement, the roles are reversed: the back surface of the first stirring shaft blades and the facing surface of the corresponding blades on the second stirring shaft are close to each other, with the blades of the second stirring shaft undertaking the main driving role. This alternating push and support design creates a more orderly and smoother circulating material flow between the two shafts and inside the reactor. After being pushed by one set of blades, the material can be smoothly continued by the blades on the other shaft, avoiding the situation in traditional symmetrical twin-shaft mixers where the blades on both shafts simultaneously impact and compress material clumps in the same area at high speed.

[0020] Clearly, by avoiding the strong head-on collision and compression of the impeller blades, the largest stress source leading to impeller fatigue fracture is fundamentally eliminated. The load acting on the impeller blades changes from impactful, high-amplitude abnormal stress to a more stable and uniform working stress, thereby significantly improving the overall mechanical reliability and service life of the stirring assembly. Impeller fracture leads to unplanned downtime, disrupting production continuity and the stability of reaction conditions. This design reduces the number of downtime maintenance visits, ensuring that the acidolysis reaction can proceed under stable and controllable process conditions for extended periods, which is beneficial for improving the consistency and stability of titanium dioxide product quality. The partially overlapping dual-shaft layout and alternating stirring mode still ensure that the materials (titanium ore powder and concentrated sulfuric acid) are fully and rapidly mixed, preventing agglomeration and sedimentation. At the same time, the resulting orderly flow field helps to enhance mass and heat transfer, continuing to ensure uniform temperature within the reactor and avoiding localized overheating. Furthermore, smooth material flow also allows the gases generated in the reaction (such as steam) to escape more easily from the material along with the flow field, preventing them from being trapped in dead zones or eddies formed by violent collisions, thus improving operational safety.

[0021] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of a stirring assembly provided in an embodiment of this application is shown from one perspective.

[0024] Figure 2 The diagram shows a structural schematic of a blade provided by an embodiment of this application from one perspective.

[0025] Explanation of key component symbols:

[0026] 100 - Second stirring shaft; 200 - First stirring shaft; 300 - Blade; 310 - Feeding surface; 320 - Backing surface; 330 - Wear-resistant layer; 400 - Buffer zone. Detailed Implementation

[0027] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0028] It should be noted that when an element is said to be "fixed" to another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly" on another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0029] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the template description is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] In related technologies, continuous acidolysis reactors are used to mix powdered titanium raw materials with concentrated sulfuric acid to ensure a complete reaction. To achieve continuous, stable, and safe operation, such reactors are equipped with a stirring system. Stirring ensures rapid and uniform mixing of the solid titanium raw material and concentrated sulfuric acid, preventing agglomeration and sedimentation; it enhances mass and heat transfer, making the reactor temperature uniform and avoiding localized overheating; and it promotes the smooth escape of gases generated in the reaction (such as steam and trace amounts of sulfur trioxide). Typically, powerful mechanical twin-shaft agitators, such as turbine or paddle agitators, are used, driven by top-mounted or side-mounted motors and reducers. However, in actual operation, due to the compression of the material, the blades of the twin-shaft agitator are prone to breakage.

[0033] like Figure 1 and Figure 2 As shown, in order to solve the above-mentioned technical problems, this application provides a stirring assembly, which includes:

[0034] A pair of stirring shafts are arranged side by side, and the blades 300 of the pair of stirring shafts partially overlap in axial projection; wherein, one of the stirring shafts is a first stirring shaft 200 and the other stirring shaft is a second stirring shaft 100, and the blades 300 of the first stirring shaft 200 are evenly divided into two groups of blades 300, one group of blades 300 is located at one end of the first stirring shaft 200 and the other group of blades 300 is located at the other end of the first stirring shaft 200;

[0035] Furthermore, one end face of the blade 300 is the material-facing surface 310, and the other end face of the blade 300 is the material-returning surface 320. The material-facing surface 310 of the blade 300 in one group of blades 300 and the material-returning surface 320 of the corresponding blade 300 on the second stirring shaft 100 are close to each other. The material-returning surface 320 of the blade 300 in another group of blades 300 and the material-facing surface 310 of the corresponding blade 300 on the second stirring shaft 100 are arranged close to each other.

[0036] In these embodiments, a stirring assembly for an acidolysis reactor is provided, the stirring assembly including a pair of stirring shafts, namely a first stirring shaft 200 and a second stirring shaft 100, which are arranged side by side within the reactor shell and are parallel in the horizontal direction. The first stirring shaft 200 and the second stirring shaft 100 are each driven by an independent drive device (such as a motor and a reducer, not shown), and can rotate in the same direction or in opposite directions, preferably in opposite directions, to enhance the shearing and mixing effect of the material.

[0037] In axial projection, there is an overlap region L between the blades 300 on the first stirring shaft 200 and the second stirring shaft 100. The length of this overlap region L accounts for 60% to 80% of the total length of the blades 300 on a single stirring shaft, preferably 70%. This design ensures that the blades 300 on the two shafts can mesh with each other during rotation, achieving efficient stirring and crushing of high-viscosity, high-density titanium raw materials and concentrated sulfuric acid mixtures.

[0038] The impellers 300 on the first stirring shaft 200 are symmetrically arranged along the axial direction and are evenly divided into two groups of impellers 300: a first group of impellers 300 and a second group of impellers 300. The first group of impellers 300 is located at the left end of the first stirring shaft 200, and the second group of impellers 300 is located at its right end. Each group of impellers 300 includes multiple impeller units distributed circumferentially and axially. The impellers 300 can be straight, angled, or turbine-type structures, and are preferably made of corrosion-resistant stainless steel or titanium alloy.

[0039] Crucially, in this embodiment, the impeller 300 has a clearly defined incoming surface 310 and a back surface 320. When the stirring shaft rotates, the material is mainly subjected to thrust from the incoming surface 310. In terms of arrangement, the incoming surfaces 310 of the impellers 300 in the first impeller group and the back surfaces 320 of the corresponding impellers 300 on the second stirring shaft 100 are arranged close to each other; while the back surfaces 320 of the impellers 300 in the second impeller group and the incoming surfaces 310 of the corresponding impellers 300 on the second stirring shaft 100 are arranged close to each other.

[0040] Specifically, in the overlapping area on the left, the material-facing surface 310 of the blade 300 of the first stirring shaft 200 faces the second stirring shaft 100, while the material-returning surface 320 of the blade 300 of the second stirring shaft 100 at the corresponding position faces the first stirring shaft 200, forming an asymmetrical meshing structure with "facing-returning" opposite each other; while in the area on the right, a "returning-facing" opposite arrangement is formed.

[0041] This asymmetrical arrangement ensures that as the two mixing shafts rotate in opposite directions, the material experiences alternating pushing and pulling forces when entering the overlapping area. This not only enhances the mixing intensity but, more importantly, effectively balances the lateral extrusion force on the impeller 300. In a traditional symmetrical arrangement, the facing surfaces 310 of the twin-shaft impeller 300 are opposite each other, leading to intense extrusion of the material in the meshing zone and stress concentration at the root of the impeller 300, making it prone to fatigue fracture. This embodiment, through alternating "facing-back" and "back-facing" arrangements, achieves a more uniform pressure distribution, significantly reducing the risk of impeller 300 fracture due to excessive force on one side.

[0042] For example, the first stirring shaft 200 and the second stirring shaft 100 rotate in opposite directions (i.e., the rotation directions of the two shafts near their ends are opposite), so that the material is pushed downward or inward in the overlapping area, which is beneficial for gas discharge and prevents material splashing.

[0043] In practical applications, this stirring assembly is installed in the acidolysis reactor of a sulfuric acid process titanium dioxide production plant. Ilmenite powder and concentrated sulfuric acid are continuously added from the top of the reactor, and the stirring assembly operates at a speed of 15–30 rpm. Experiments show that, using the stirring assembly of this embodiment, the average service life of the stirring shaft blades 300 is extended compared to traditional structures, the temperature distribution uniformity within the reactor is improved, and no unplanned downtime due to blade 300 breakage occurs.

[0044] In summary, this embodiment effectively alleviates the problem of blade breakage under high load conditions in the twin-shaft agitator by dividing the blades 300 of the first stirring shaft 200 into two symmetrically arranged blade groups 300 and adopting an asymmetrical configuration in which the material-facing surface 310 and the material-returning surface 320 alternately face each other. This improves the stability and safety of equipment operation and meets the requirements of continuous acid hydrolysis process for long-term reliable operation of the stirring system.

[0045] In some embodiments, the gap between the two sets of blades 300 defines a buffer zone 400, and at least one of the blades 300 of the second stirring shaft 100 is located in the buffer zone 400.

[0046] In these embodiments, this embodiment provides an improved stirring assembly structure that further optimizes the force distribution, reduces stress concentration, and improves the operational stability of the equipment.

[0047] Along the axial direction of the first stirring shaft 200, a bladeless region 300 is reserved between the first set of impellers 300 and the second set of impellers 300. For example, the length of this region along the axial direction is set to 50-200 mm. This bladeless region 300 forms a low-shear, low-resistance transition space in space, which is defined as a "buffer zone 400".

[0048] Accordingly, the blades 300 on the second stirring shaft 100 are arranged continuously along the axial direction, and the distribution of the blades 300 covers the entire stirring length. During assembly, at least a portion of one or more blades 300 of the second stirring shaft 100 is located within the axial projection range of the buffer zone 400, that is, the blade 300 is directly opposite the gap between the sets of blades 300 on the first stirring shaft 200.

[0049] Optionally, the impeller 300 located within the buffer zone 400 may be single or multiple, with a width (axial length) less than or equal to the length of the buffer zone 400, and its facing surface 310 or back surface 320 facing the first stirring shaft 200. In this embodiment, the facing surface 310 of the impeller 300 faces the first stirring shaft 200.

[0050] A buffer zone 400 is set on the first stirring shaft 200, so that the shear force is significantly reduced when the material flows through the area, forming a "pressure relief zone" which helps to alleviate the mechanical load of the overall system.

[0051] When the blade 300 of the second stirring shaft 100 enters the buffer zone 400, since there is no blade 300 blocking the corresponding position of the first stirring shaft 200, the blade 300 can stir the material more freely, generating local disturbance, promoting the uniform distribution of the material in the axial direction, and avoiding material accumulation or uneven reaction caused by stirring dead zones.

[0052] Due to the presence of the buffer zone 400, the two sets of blades 300 of the first stirring shaft 200 are structurally separated, avoiding bending fatigue caused by continuous stress on the long shaft. At the same time, the stress environment of the blades 300 of the second stirring shaft 100 within the buffer zone 400 is more gentle, reducing the impact load caused by rigid meshing, thereby reducing the overall probability of blade 300 fracture in the dual-shaft system.

[0053] The presence of buffer zone 400 allows for certain assembly tolerances in the axial position of the blades 300 of the second stirring shaft 100, eliminating the need for strict alignment and improving the fault tolerance of equipment manufacturing and installation.

[0054] In practical operation, this structure is particularly suitable for titanium raw material-concentrated sulfuric acid mixture systems with high solids content and high viscosity. Experimental data show that, under the same operating conditions, the stirring assembly using the structure of this embodiment exhibits reduced drive motor current fluctuations, lower vibration acceleration, and a decrease in the peak stress at the root of the 300mm blade, significantly improving the reliability and service life of the equipment.

[0055] In some embodiments, the number of blades 300 on the first stirring shaft 200 is even, the number of blades 300 on the second stirring shaft 100 is odd, the blade 300 on the second stirring shaft 100 located in the buffer zone 400 is the middle blade 300, the number of the middle blade 300 is one, and the two sets of blades 300 are symmetrically arranged about the middle blade 300.

[0056] In these embodiments, a stirring component arrangement scheme with higher structural symmetry and more balanced force is provided, further improving stirring uniformity and structural stability.

[0057] In this embodiment, the number and spatial layout of the blades 300 of the first stirring shaft 200 and the second stirring shaft 100 are optimized:

[0058] The first stirring shaft 200 has an even number of blades 300, such as 6, 8, or 10. The second stirring shaft 100 has an odd number of blades 300, such as 7, 9, or 11.

[0059] The blades 300 of the second stirring shaft 100 are distributed equidistantly or non-equidistantly along the axial direction. The blade 300 located at the center of the axial direction is defined as the "middle blade 300", and there is one blade in the middle.

[0060] The first stirring shaft 200 has two sets of blades 300: a first set of blades 300 and a second set of blades 300, which are symmetrically arranged about the axial projection position of the middle blade 300. The center of the buffer zone 400 is axially aligned with the center of the middle blade 300, such that the middle blade 300 is wholly or partially located within the buffer zone 400.

[0061] Specifically, when the first stirring shaft 200 and the second stirring shaft 100 are installed in the reactor and in the working position, the middle blade 300 of the second stirring shaft 100 is directly aligned with the gap area (i.e., buffer zone 400) between the two blades 300 on the first stirring shaft 200, achieving precise spatial correspondence.

[0062] This arrangement has the following significant advantages:

[0063] By symmetrically arranging the two sets of blades 300 of the first stirring shaft 200 about the middle blade 300 of the second stirring shaft 100, the mass distribution and force on the entire stirring system in the axial direction are more balanced. During rotation, vibration and eccentric loads are significantly reduced, which helps to extend the service life of bearings and shafts.

[0064] The central blade 300 is located at the geometric center of the mixing zone and within the low-resistance buffer zone 400. It can effectively disturb the material in the central area with less energy consumption, break the possible "inert core", and promote the axial circulation and mixing uniformity of the overall material.

[0065] Since the number of blades 300 on the first stirring shaft 200 is even and the number of blades 300 on the second stirring shaft 100 is odd, the meshing phase of the blades 300 changes continuously during the rotation of the two shafts, avoiding periodic resonance or high stress concentration at a fixed position, thus improving the smoothness of operation.

[0066] Using a single central blade 300 as a symmetrical reference simplifies the equipment installation and positioning process. During on-site assembly, simply aligning the central blade 300 of the second stirring shaft 100 with the gap center of the first stirring shaft 200 achieves precise matching of the overall structure.

[0067] In some embodiments, all blades 300 of the second stirring shaft 100 are arranged at equal intervals in the axial direction, and blades 300 of the same group of blades 300 are arranged at equal intervals.

[0068] In some embodiments, the number of blades 300 of the first stirring shaft 200 is N, and the number of blades 300 of the second stirring shaft 100 is M, and satisfies: N = M + 1.

[0069] In these embodiments, the axial arrangement of the blades 300 on the stirring shaft is optimized to achieve a more uniform stirring effect and more stable mechanical properties.

[0070] All blades 300 of the second stirring shaft 100 are equally spaced in the axial direction, meaning that the axial distance d2 between adjacent blades 300 remains constant. This equidistant arrangement ensures that the second stirring shaft 100 applies uniform thrust and shear force to the material along its entire length, avoiding areas of excessively strong or weak stirring.

[0071] Meanwhile, the blades 300 within each blade group 300 of the first stirring shaft 200 are also arranged at equal intervals. That is, within the first blade group 300, the axial spacing d1 between adjacent blades 300 remains consistent; within the second blade group 300, the spacing between blades 300 is also d1 (which may be the same as or different from d2). For example, if a blade group 300 contains 4 blades 300, then it has 3 equidistant intervals within it.

[0072] In this embodiment, a buffer zone 400 with a length of L0 (e.g., 50-200 mm) is provided between the two sets of blades 300 of the first stirring shaft 200, and no blades 300 are distributed in this area. Therefore, the blades 300 of the entire first stirring shaft 200 are arranged in a "segmented, equidistant, and interrupted" pattern.

[0073] Preferably, the distance d2 between the blades 300 of the second stirring shaft 100 and the distance d1 between the blades 300 of the first stirring shaft 200 are equal or an integer multiple thereof, so as to form regular meshing and misalignment during the reverse rotation of the two shafts, thereby further improving the mixing efficiency and reducing vibration noise.

[0074] This equidistant arrangement scheme has the following technical advantages:

[0075] The equidistant arrangement avoids the "stirring blind zone" or "excessive shear zone" caused by uneven blade distribution, enabling more consistent mixing and reaction of titanium raw materials and concentrated sulfuric acid along the entire length of the reactor, which is beneficial for improving batch stability of product quality. The equidistant structure makes the force distribution on the stirring shaft more regular during rotation, facilitating finite element stress analysis and fatigue life prediction, and helping to optimize structural design and material selection. The equidistant arrangement simplifies the stirring shaft manufacturing process (such as welding positioning and CNC machining), reduces manufacturing errors, and improves product consistency and replaceability.

[0076] In some embodiments, the surface of the stirring shaft is provided with a reinforcing layer.

[0077] In these embodiments, one or more reinforcing layers are provided on the surface of the stirring shaft to improve the service life and efficiency of the stirring shaft.

[0078] Depending on the application scenario and requirements, the reinforcement layer can be, but is not limited to, a metal plating, a ceramic coating, a polymer coating, or a composite material layer.

[0079] For example, when handling highly corrosive materials, one can choose a titanium alloy coating or a ceramic coating with excellent corrosion resistance, such as an alumina or zirconium oxide coating.

[0080] For applications requiring high strength and wear resistance, hard alloy materials such as tungsten carbide (WC) or titanium nitride (TiN) can be used as reinforcing layers.

[0081] In certain special cases, low-friction polymer coatings such as polytetrafluoroethylene (PTFE) can also be used to reduce resistance and wear during the stirring process.

[0082] The reinforcement layer can be coated or deposited through a variety of processes, including physical vapor deposition (PVD), chemical vapor deposition (CVD), thermal spraying, electroplating, etc.

[0083] Physical vapor deposition (PVD) is a commonly used and efficient deposition technique suitable for forming metal or ceramic coatings with high hardness and strong adhesion. Chemical vapor deposition (CVD), on the other hand, is more suitable for preparing protective coatings with uniform thickness and high density.

[0084] Thermal spraying technology can quickly coat large workpieces with a thick and wear-resistant coating, making it suitable for mass production.

[0085] Electroplating is a lower-cost option, especially suitable for preparing metal coatings.

[0086] By setting a reinforcing layer, this utility model achieves the following significant technical effects:

[0087] The reinforcing layer significantly improves the surface hardness and wear resistance of the agitator shaft, effectively extending its service life and reducing maintenance frequency and replacement costs. Selecting appropriate reinforcing layer materials for specific chemical environments can greatly enhance the corrosion resistance of the agitator shaft, ensuring long-term stable operation of the equipment. For reinforcing layers made of low-friction coefficient materials, not only can the heat generated during agitation be reduced, but energy consumption can also be decreased, improving overall work efficiency. Different types of reinforcing layers allow the agitator shaft to adapt to a wider range of applications, maintaining good working condition regardless of extreme temperatures, high pressures, or highly corrosive conditions.

[0088] In some embodiments, a wear-resistant layer 330 is provided on the top of the blade 300; wherein, in the direction from the top of the blade 300 to the root, the wear-resistant layer 330 includes a plurality of sub-segments, and in adjacent sub-segments, the sub-segment closer to the root has a smaller thickness.

[0089] In these embodiments, the surface protection structure of the stirring blade 300 is optimized to provide a wear-resistant layer 330 with a gradient thickness distribution, so as to balance wear resistance, structural strength and material economy.

[0090] The top of the blade 300 is provided with a wear-resistant layer 330. The wear-resistant layer 330 covers the material-facing surface 310, the material-returning surface 320 and the top edge area of ​​the blade 300, with particular emphasis on strengthening the leading edge area where the material impact is strongest.

[0091] Crucially, the wear-resistant layer 330 is divided into multiple sub-segments, such as a first sub-segment and a second sub-segment, in the direction from the top of the blade 300 to the root (i.e., along the length of the blade 300). The sub-segments are arranged sequentially along the axial or length direction, forming a stepped or gradually changing thickness distribution.

[0092] in:

[0093] The first sub-section is located at the top of the blade 300 and directly bears the initial impact and shear of the material. Its wear-resistant layer 330 has the largest thickness, denoted as t1, where t1 ≥ 3.5 mm.

[0094] The second sub-section is located in the middle region, where the stress intensity is reduced compared to the top, and its wear-resistant layer has a thickness of 330 t2. <t1,t2≥2.5mm。

[0095] That is, in adjacent sub-segments, the closer the sub-segment is to the root, the smaller the thickness of its wear-resistant layer 330, forming a gradient decreasing structure of "thick at the top and thin at the root".

[0096] The wear-resistant layer 330 can be made of one or more of the following materials: tungsten carbide, alumina ceramic, nickel-based alloy, ultrafine-grained cemented carbide, or cermet composite material. Segmented spraying using supersonic flame spraying or plasma spraying is preferred to achieve precise thickness control in different areas.

[0097] The top of the blade 300 bears the greatest impact and wear, therefore the thickest wear-resistant layer 330 is installed; while the root stress is mainly bending moment, excessive welding of wear-resistant material may cause cracks or peeling. This solution is to "strengthen as needed" according to the actual stress distribution, avoiding material waste and preventing interface peeling caused by excessive coating thickness.

[0098] The gradient thickness design allows for a smooth transition of interfacial stress caused by the difference in thermal expansion coefficients between the wear-resistant layer 330 and the base metal, reducing the risk of coating cracking or peeling due to thermal cycling or mechanical vibration.

[0099] In some embodiments, a wear-resistant layer 330 is provided on both the end face and the side face of the bottom of the blade 300.

[0100] In some embodiments, the wear-resistant layer 330 is a metal cladding layer.

[0101] In these embodiments, the preparation process of the wear-resistant layer 330 is specifically defined: the wear-resistant layer 330 is a metal cladding layer.

[0102] Metal cladding refers to the process of locally melting and rapidly solidifying added metal or alloy powder onto the substrate surface using a high-energy heat source (such as laser, plasma arc, or electric arc), forming a dense, reinforced layer that is metallurgically bonded to the substrate. This process differs from traditional spray coatings (primarily mechanical bonding) and offers advantages such as high bonding strength, low porosity, and controllable dilution rate, making it particularly suitable for agitator blades operating in high-stress, highly corrosive environments.

[0103] Specifically, the material of the metal cladding layer is selected from one or more of the following:

[0104] Nickel-based alloys, such as Ni-Cr-B-Si self-fluxing alloys, have excellent high-temperature resistance, oxidation resistance, and corrosion resistance.

[0105] Cobalt-based alloys, such as the Stellite series alloys, possess excellent wear resistance and thermal fatigue resistance.

[0106] Iron-based alloys, such as Fe-Cr-Ni-W or Fe-Cr-C alloys, are low in cost, high in hardness, and suitable for moderately corrosive environments.

[0107] Tungsten carbide composite cladding layer: WC particles are pre-placed or fed simultaneously and clad in a nickel-based or cobalt-based binder phase to form a composite structure of "hard phase + metal matrix", which significantly improves the resistance to abrasive wear.

[0108] The metal cladding layer forms a metallurgical bond with the blade substrate (usually 304, 316L stainless steel, or low-alloy steel), with a bonding strength exceeding 400 MPa, far higher than the 10–30 MPa of sprayed coatings. This significantly reduces the risk of coating peeling during operation. The cladding layer has a dense structure with a porosity of less than 1%, effectively preventing corrosive media such as concentrated sulfuric acid from penetrating into the substrate and extending equipment life.

[0109] For worn-out old propeller blades of the 300, local repair and performance upgrades can be achieved through laser cladding, realizing green remanufacturing and reducing the total life cycle cost of the equipment.

[0110] In some embodiments, this application also provides an acidolysis reactor, which includes any of the stirring components described in the above embodiments.

[0111] Since the above-mentioned stirring assembly has the above-mentioned technical effects, the acid hydrolysis reactor including the stirring assembly should have the same technical effects, which will not be elaborated here.

[0112] In some embodiments, this application also provides a sulfuric acid process titanium dioxide production apparatus, which includes an acidolysis reactor as described in the above embodiments.

[0113] Since the acidolysis reactor described above has the aforementioned technical effects, the sulfuric acid process titanium dioxide production equipment including the acidolysis reactor should have the same technical effects, which will not be elaborated further here.

[0114] In all examples shown and described herein, any specific values ​​should be interpreted as merely exemplary and not as limitations; therefore, other examples of exemplary embodiments may have different values.

[0115] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0116] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A stirring assembly, characterized in that, The stirring assembly includes: A pair of stirring shafts are arranged side by side, and the blades of the pair of stirring shafts partially overlap in axial projection; wherein, one of the stirring shafts is a first stirring shaft and the other stirring shaft is a second stirring shaft, and the blades of the first stirring shaft are divided into two blade groups, one blade group is located at one end of the first stirring shaft and the other blade group is located at the other end of the first stirring shaft. Furthermore, one end face of the blade is the feeding face, and the other end face of the blade is the back face. The feeding face of the blade in one blade group and the back face of the corresponding blade on the second stirring shaft are close to each other, and the back face of the blade in another blade group and the feeding face of the corresponding blade on the second stirring shaft are arranged close to each other.

2. The stirring assembly according to claim 1, characterized in that, The gap between the two blade sets defines a buffer zone, and at least one of the blades of the second stirring shaft is located in the buffer zone.

3. The stirring assembly according to claim 2, characterized in that, The number of blades on the first stirring shaft is even, the number of blades on the second stirring shaft is odd, the blade on the second stirring shaft located in the buffer zone is a middle blade, the number of the middle blade is one, and the two blade groups are symmetrically arranged about the middle blade.

4. The stirring assembly according to claim 3, characterized in that, All the blades of the second stirring shaft are arranged at equal intervals in the axial direction, and the blades of the same blade group are arranged at equal intervals.

5. The stirring assembly according to claim 4, characterized in that, The number of blades on the first stirring shaft is N, and the number of blades on the second stirring shaft is M, satisfying: N = M + 1.

6. The stirring assembly according to claim 1, characterized in that, The surface of the stirring shaft is provided with a reinforcing layer.

7. The stirring assembly according to claim 1, characterized in that, The blade has a wear-resistant layer at its top; wherein, in the direction from the top of the blade to the root, the wear-resistant layer includes multiple sub-segments, and in adjacent sub-segments, the sub-segment closer to the root has a smaller thickness.

8. The stirring assembly according to claim 7, characterized in that, The wear-resistant layer is a metal cladding layer.

9. An acid hydrolysis reactor, characterized in that, The acidolysis reactor includes a stirring assembly as described in any one of claims 1 to 8.

10. A sulfuric acid process titanium dioxide production apparatus, characterized in that, The sulfuric acid process titanium dioxide production apparatus includes the acidolysis reactor as described in claim 9.

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