Oxalic acid hydrolysis mixing kettle

Abstract

The utility model relates to the technical field of reaction kettle, specifically, a kind of oxalic acid hydrolysis mixing kettle, including hydrolysis mixing kettle and heating device, hydrolysis mixing kettle includes mixing chamber, heating device includes the inner heating coil that is arranged in mixing chamber, and the outer heating coil that is arranged on the outer wall of hydrolysis mixing kettle, the lateral wall of hydrolysis mixing kettle is equipped with the opening being communicated with mixing chamber, one end of inner heating coil is provided with connecting flange, inner heating coil is located in mixing chamber through opening, connecting flange is detachably connected with the lateral wall of hydrolysis mixing kettle and seals opening, compared with prior art, the application is realized the detachable connection of inner heating coil and kettle body lateral wall by connecting flange, replace traditional welding / fixed sealing structure, without overall disassembly kettle body, only flange is disassembled to complete new and old coil replacement, substantially simplify process, shorten time consumption, reduce kettle body sealing damage and leakage risk, also reduce replacement cost, significantly improve maintenance convenience.

Description

Technical Field

[0001] This utility model relates to the field of reaction vessel technology, and more specifically, to an oxalic acid hydrolysis mixing vessel. Background Technology

[0002] Oxalic acid is an important precipitant material for the mining and beneficiation of ionic rare earth ores, as well as for the separation and purification of rare earth elements, especially for the purification of high-end rare earth elements such as lanthanum and europium. Compared to the traditional sodium formate process (energy consumption of 2.8 tons of standard coal / ton of oxalic acid), the hydrolysis process can reduce the overall energy consumption to 1.5 tons of standard coal / ton of oxalic acid, and produces no saline wastewater, making it highly valuable and economically viable, thus becoming the preferred route for oxalic acid production. The oxalic acid hydrolysis mixing reactor, as a crucial piece of equipment in the oxalic acid process, is a vital link in ensuring that the entire process achieves its production targets.

[0003] To meet the stringent temperature requirements of hydrolysis reactions, existing hydrolysis mixing vessels are generally equipped with heating devices. Among them, the internal heating coil has become one of the mainstream heating structures because it can directly contact the reactants in the mixing chamber and has high heat transfer efficiency.

[0004] However, the internal heating coils of existing hydrolysis mixing vessels are mostly integrated with the vessel body through welding or fixed sealing connections. During long-term use, the internal heating coils are prone to damage due to material corrosion, scaling, or high-temperature aging, requiring regular maintenance or replacement. However, since the internal heating coils are not detachable from the vessel body, replacement requires complete disassembly of the vessel body. This not only involves complex and time-consuming procedures but also necessitates suspending the entire hydrolysis production process, resulting in a significant reduction in production efficiency. Furthermore, the disassembly process can easily damage the vessel body's sealing structure, increasing the risk of subsequent leaks, and the replacement cost is high.

[0005] Furthermore, some improvement solutions attempt to enhance durability by optimizing the material of the internal heating coil, but these do not fundamentally solve the problem of disassembly and replacement, failing to meet the actual needs of industrial production for convenient equipment maintenance and production continuity. Therefore, there is an urgent need for a hydrolysis mixing vessel structure that enables convenient disassembly and replacement of the internal heating coil to overcome the shortcomings of existing technologies. Utility Model Content

[0006] The technical problem to be solved by this utility model is that the internal heating coil of the existing hydrolysis mixing vessel is fixedly connected to the vessel body, which makes it difficult to disassemble and replace the internal heating coil after it is damaged. This utility model proposes an oxalic acid hydrolysis mixing vessel.

[0007] This utility model provides an oxalic acid hydrolysis mixing vessel, including a hydrolysis mixing vessel and a heating device. The hydrolysis mixing vessel includes a mixing chamber. The heating device includes an inner heating coil disposed in the mixing chamber and an outer heating coil disposed on the outer wall of the hydrolysis mixing vessel. The side wall of the hydrolysis mixing vessel has an opening communicating with the mixing chamber. One end of the inner heating coil is provided with a connecting flange. The inner heating coil is located in the mixing chamber through the opening. The connecting flange is detachably connected to the side wall of the hydrolysis mixing vessel and seals the opening.

[0008] Compared with existing technologies, this application achieves a detachable connection between the internal heating coil and the side wall of the vessel body through a connecting flange, replacing the traditional welding / fixed sealing structure. It eliminates the need to disassemble the entire vessel body; only the flange needs to be removed to replace the old coil, greatly simplifying the process, shortening the time, reducing the risk of vessel body seal damage and leakage, reducing replacement costs, and significantly improving maintenance convenience. At the same time, it adopts a dual heating structure with an internal heating coil in the mixing chamber and an external heating coil on the outer wall of the vessel body. The internal coil ensures efficient heat transfer, while the external coil assists in temperature control, which can accurately and stably maintain the temperature required for the hydrolysis reaction, helping the process achieve production targets.

[0009] In one possible implementation, the connecting flange is provided with multiple connecting rods on the side facing the hydrolysis mixing vessel. The connecting rods are slidably engaged with the side wall of the opening. Multiple support plates located in the mixing chamber are connected to the connecting rods at intervals along the length of the connecting rods. Each support plate is provided with multiple support holes. The internal heating coil includes multiple heating tubes, which are respectively inserted into the multiple support holes.

[0010] Compared with the prior art, the connecting rod on the flange side of this application slides with the opening sidewall, which facilitates the precise positioning and disassembly of the internal heating coil. The support plates and support holes distributed at intervals on the connecting rod can stably limit the position of multiple heating tubes, preventing the heating tubes from shifting or deforming due to material impact or temperature changes, and ensuring heat transfer uniformity. At the same time, the interval design of the support plates does not hinder the flow of materials, taking into account both the support stability of the heating tubes and the reaction efficiency of materials in the mixing chamber, further improving the practicality and reliability of the equipment.

[0011] In one possible implementation, a sealing gasket is provided at the connection between the internal heating coil and the connecting flange, and a sealing gasket surrounding the opening is provided at the connection between the connecting flange and the hydrolysis mixing vessel. This application provides sealing gaskets at the connections between the internal heating coil and the connecting flange, and between the connecting flange and the vessel body, with the latter surrounding the opening. This dual-layer sealing effectively prevents material leakage within the mixing chamber while preventing external impurities from entering, ensuring a clean reaction environment and production safety, and further improving the equipment's sealing reliability.

[0012] In one possible implementation, each connecting rod is detachably fitted with a sleeve, and the support plate is fixed to the sleeve. By detachably fitting the sleeve to the connecting rod and fixing the support plate to the sleeve, the spacing between the support plate and the connecting rod can be flexibly adjusted through the detachable engagement of the sleeve and the connecting rod to accommodate internal heating coils of different lengths, thus improving the device's adaptability to coils. Furthermore, when the support plate or sleeve is damaged, it is not necessary to replace the entire connecting rod; only the damaged sleeve or support plate needs to be disassembled and replaced, further reducing component maintenance and replacement costs. At the same time, it does not affect the stable support of the internal heating coil and the overall ease of disassembly and assembly, thus balancing structural flexibility, maintenance economy, and operational reliability.

[0013] In one possible implementation, the support plate, the sleeve, and the connecting rod are all made of 904 stainless steel. 904 stainless steel possesses excellent resistance to corrosive materials such as oxalic acid, effectively preventing corrosion damage to components during long-term contact with hydrolytic reaction materials, significantly extending the service life of the support plate, sleeve, and connecting rod. Simultaneously, 904 stainless steel combines high strength and toughness, ensuring stable support of the internal heating coil by the support plate and reliable connection between the sleeve and connecting rod, preventing structural deformation or breakage due to insufficient material strength, and reducing long-term operating costs.

[0014] In one possible implementation, multiple connecting rods are arranged in a ring-shaped interval along the circumference of the connecting flange. This structure allows the support plates to form a surrounding support for the heating coil inside the mixing chamber via the ring-shaped connecting rods, preventing the coil from shifting or being damaged due to uneven local stress and improving support stability.

[0015] In one possible implementation, the internal heating coil is a U-shaped tube, and the number of support holes is multiple sets, with each set of support holes including two rows of support holes spaced apart, and the two ends of the U-shaped tube being inserted and fixed into the corresponding support holes respectively.

[0016] Compared with the prior art, this application sets the internal heating coil as a U-shaped tube, which can increase the heat transfer area and improve the heat transfer efficiency within the limited mixing chamber; the support holes are set as multiple sets, each set containing two rows of spaced support holes, which can accommodate multiple U-shaped tubes for insertion and fixation, ensuring that the U-shaped tubes are installed stably and avoiding displacement and deformation, while the spaced distribution does not hinder the material flow, taking into account both the heat transfer effect and the material mixing reaction efficiency, and further optimizing the equipment performance.

[0017] In one possible implementation, each U-tube includes an inlet and an outlet, the inlet being connected to an external steam source and the outlet being connected to a condensate collector, and the U-tube being fixed to the hydrolysis mixing vessel via a connecting flange.

[0018] Compared with the prior art, the U-shaped tube in this application has an inlet connected to external steam and an outlet connected to a condensate collector. This allows steam to smoothly enter the U-shaped tube through the inlet, efficiently releasing heat by utilizing the large contact area between the U-shaped tube and the material to meet the heating requirements of the hydrolysis reaction. At the same time, it allows the condensate after heat exchange to be discharged into the collector in a timely manner through the outlet, avoiding the accumulation of condensate in the tube and affecting steam flow and heat transfer efficiency, thus achieving efficient steam recycling. Meanwhile, the flange fixing method ensures the sealing of the connection between the U-shaped tube and the reactor body, preventing steam leakage or material seepage into the tube.

[0019] In one possible implementation, the hydrolysis mixing vessel is made of 904L stainless steel. This application specifies 904L stainless steel as the material for the hydrolysis mixing vessel. This material has excellent corrosion resistance to acidic hydrolysable materials such as oxalic acid, effectively resisting corrosion of the vessel body caused by long-term immersion and scouring, preventing leakage or structural strength reduction due to corrosion, and ensuring production safety.

[0020] In one possible implementation, the internal heating coil is made of zirconium.

[0021] Compared with existing technologies, this application uses zirconium as the material for the internal heating coil. This material has excellent corrosion resistance to highly corrosive media such as oxalic acid, which is far superior to traditional stainless steel. It can effectively avoid problems such as corrosion perforation and scaling blockage in the internal heating coil during long-term contact with hydrolyzed materials, ensuring the long-term smooth operation and heating stability of the coil. At the same time, zirconium also has good thermal conductivity, which can efficiently transfer steam heat to the material, ensuring that the temperature conditions required for the hydrolysis reaction are quickly achieved.

[0022] In one possible implementation, the external heating coil is made of 304 stainless steel. This application uses 304 stainless steel for the external heating coil, which only contacts the outer wall of the vessel and does not directly contact highly corrosive materials such as oxalic acid. 304 stainless steel is sufficient to resist external environmental corrosion, and it also has good thermal conductivity, meeting the auxiliary heating requirements of the outer wall. More importantly, the cost of 304 stainless steel is significantly lower than that of zirconium and 904L stainless steel, which can greatly reduce the overall manufacturing cost of the equipment while ensuring the external heating function and structural stability. Attached Figure Description

[0023] Figure 1 This is an overall structural diagram of the oxalic acid hydrolysis mixing vessel of this application; Figure 2 This is a structural diagram of the internal heating coil in this application; Figure 3 This is a schematic diagram of the connecting flange structure; Explanation of reference numerals in the attached figures: 1. Mixing chamber; 21. Inner heating coil; 22. Outer heating coil; 3. Connecting flange; 4. Connecting rod; 5. Support plate; 6. Sleeve. Detailed Implementation

[0024] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0025] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0026] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] As shown in Figure 1, an oxalic acid hydrolysis mixing vessel includes a hydrolysis mixing vessel and a heating device. The hydrolysis mixing vessel includes a mixing chamber 1. The heating device includes an inner heating coil 21 disposed in the mixing chamber 1 and an outer heating coil 22 disposed on the outer wall of the hydrolysis mixing vessel. The side wall of the hydrolysis mixing vessel is provided with an opening communicating with the mixing chamber 1. One end of the inner heating coil 21 is provided with a connecting flange 3. The inner heating coil 21 is located in the mixing chamber 1 through the opening. The connecting flange 3 is detachably connected to the side wall of the hydrolysis mixing vessel and seals the opening.

[0029] In existing hydrolysis mixing vessels, the internal heating coil 21 is mostly integrated with the vessel body through welding or fixed sealing connections. During long-term use, the internal heating coil 21 is prone to damage due to material corrosion, scaling, or high-temperature aging, requiring regular maintenance or replacement. However, since the internal heating coil 21 is not detachable from the vessel body, replacement requires complete disassembly of the vessel body. This not only involves complex and time-consuming procedures but also necessitates suspending the entire hydrolysis production process, resulting in a significant reduction in production efficiency. Furthermore, the disassembly process can easily damage the vessel body's sealing structure, increasing the risk of subsequent leaks, and the replacement cost is high. This application achieves a detachable connection between the internal heating coil 21 and the side wall of the vessel body through the connecting flange 3, replacing the traditional welding / fixed sealing structure. It eliminates the need to disassemble the entire vessel body; only the flange needs to be removed to replace the old coil, greatly simplifying the process, shortening the time, reducing the risk of vessel body seal damage and leakage, reducing replacement costs, and significantly improving maintenance convenience. At the same time, it adopts a dual heating structure with the internal heating coil 21 in the mixing chamber 1 and the external heating coil 22 on the outer wall of the vessel body. The internal coil ensures efficient heat transfer, while the external coil assists in temperature control, which can accurately and stably maintain the temperature required for the hydrolysis reaction, helping the process achieve production targets.

[0030] As shown in Figure 1 and Figure 2, this application provides a detachable connection method. Specifically, a plurality of connecting rods 4 are provided on the side of the connecting flange 3 facing the hydrolysis mixing vessel. The connecting rods 4 are slidably engaged with the side wall of the opening. A plurality of support plates 5 located in the mixing chamber 1 are connected to the connecting rods 4 at intervals along the length direction of the connecting rods 4. Each support plate 5 is provided with a plurality of support holes. The internal heating coil 21 includes a plurality of heating tubes, and the plurality of heating tubes are respectively inserted into the plurality of support holes.

[0031] In practical applications, the following steps can be taken for replacement: First, remove the fasteners between the connecting flange 3 and the side wall of the vessel, so that the connecting flange 3 drives the connecting rod 4 to slide outward along the opening side wall, and simultaneously remove the support plate 5 and the heating tube inserted in the support hole from the mixing chamber 1. Secondly, pull out the old heating tube from the support hole of the support plate 5 and replace it with a new heating tube; Finally, slide the support plate 5 with the new heating tube and the connecting rod 4 along the opening side wall into the mixing chamber 1, so that the connecting flange 3 is re-fixed to the side wall of the vessel, and the replacement is completed.

[0032] Referring to Figure 2, this application provides a more specific solution: each connecting rod 4 is detachably equipped with a sleeve 6, and the support plate 5 is fixed to the sleeve 6. During disassembly, after the entire assembly of "connecting flange 3 + connecting rod 4 + sleeve 6 + support plate 5 + internal heating coil 21" is pulled out, the fixing of the sleeve 6 to the connecting rod 4 can be removed individually, allowing for the individual replacement of the support plate 5 and the sleeve 6. This does not damage the integrated structure of the connecting rod 4 and the flange, and the "intermediate transition" function of the sleeve 6 makes the maintenance of the support plate 5 more flexible, further enhancing the overall solution's disassemblyability and component reusability.

[0033] More specifically, this application also provides a sealing gasket at the connection between the internal heating coil 21 and the connecting flange 3, and a sealing gasket surrounding the opening is provided at the connection between the connecting flange 3 and the hydrolysis mixing vessel.

[0034] In this application, the support plate 5, sleeve 6 and connecting rod 4 are all made of 904 stainless steel. Depending on other application scenarios, the support plate 5, sleeve 6 and connecting rod 4 can be replaced with different materials, mainly to extend their service life.

[0035] In this application, multiple connecting rods 4 are arranged in a ring at intervals along the circumferential direction of the connecting flange 3, the internal heating coil 21 is a U-shaped tube, and the number of support holes is multiple sets, each set of support holes including two rows of support holes arranged at intervals, and the two ends of the U-shaped tube are respectively inserted and fixed to the corresponding support holes.

[0036] Multiple connecting rods 4 are arranged in a ring at intervals, and are connected and fixed to the U-shaped inner heating coil 21 by inserting them into the two rows of support holes. This not only provides stable support to the U-shaped coil through the ring connecting rods 4 and the two rows of support holes, preventing the coil from shaking, but also increases the heat transfer area through the U-shaped structure. The ring distribution does not obstruct the flow of materials, ensuring heat exchange efficiency. At the same time, the plug-in fixing combined with the overall detachable design makes the coil easier to install and remove, taking into account stability, high efficiency and convenient maintenance.

[0037] In this application, each U-shaped tube includes an inlet and an outlet. The inlet is connected to an external steam source, and the outlet is connected to a condensate collector. The U-shaped tube is fixed to the hydrolysis mixing vessel via a connecting flange 3. Replacing the traditional jacketed heating with a steam tracing pipe (i.e., internal heating coil 21) improves heat transfer efficiency by 2.3 times, and the modular and detachable design (including connecting flange 3, connecting rod 4, etc.) facilitates inspection and maintenance.

[0038] In this application, the hydrolysis mixing vessel is made of 904L stainless steel.

[0039] It is worth mentioning that the heating coil 21 in this application is made of zirconium.

[0040] In the process of hydrolyzing dimethyl oxalate to produce oxalic acid, the mixing unit (i.e., the hydrolysis mixing vessel) is a key reaction unit, and its reaction efficiency directly affects the processing load of the subsequent distillation system. Currently, the industry generally adopts a design scheme of enamel-lined mixing vessels combined with mechanical stirring and jacketed steam heating. However, significant technical defects have been exposed in actual operation: on the one hand, the inherent high thermal resistance of the enamel layer leads to low heat transfer efficiency, and the temperature response delay during steam heating is severe, with the measured heating rate being 30%-40% lower than that of metal materials; on the other hand, the risk of cracking of the enamel layer under sudden temperature changes (ΔT>60℃) is prominent. In regions with large diurnal temperature differences, such as Xinjiang, frequent thermal stress shocks lead to an enamel detachment accident rate as high as 47%, seriously affecting the continuous operation of the unit.

[0041] For the reasons mentioned above, this application uses zirconium as the material for the internal heating coil 21. This material has excellent corrosion resistance to highly corrosive media such as oxalic acid, which is far superior to traditional stainless steel. It can effectively avoid problems such as corrosion perforation and scaling blockage in the internal heating coil 21 during long-term contact with hydrolyzed materials, ensuring the long-term smooth operation and heating stability of the coil. At the same time, zirconium also has good thermal conductivity, which can efficiently transfer steam heat to the material, ensuring that the temperature conditions required for the hydrolysis reaction are quickly achieved.

[0042] More specifically, the external heating coil 22 of this application is made of 304 stainless steel.

[0043] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0044] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An oxalic acid hydrolysis mixing vessel, characterized in that, The device includes a hydrolysis mixing vessel and a heating device. The hydrolysis mixing vessel includes a mixing chamber (1). The heating device includes an inner heating coil (21) disposed in the mixing chamber (1) and an outer heating coil (22) disposed on the outer wall of the hydrolysis mixing vessel. The side wall of the hydrolysis mixing vessel is provided with an opening communicating with the mixing chamber (1). One end of the inner heating coil (21) is provided with a connecting flange (3). The inner heating coil (21) is located in the mixing chamber (1) through the opening. The connecting flange (3) is detachably connected to the side wall of the hydrolysis mixing vessel and seals the opening.

2. The oxalic acid hydrolysis mixing vessel according to claim 1, characterized in that, The connecting flange (3) is provided with multiple connecting rods (4) on the side facing the hydrolysis mixing vessel. The connecting rods (4) are slidably engaged with the side wall of the opening. Multiple support plates (5) located in the mixing chamber (1) are connected to the connecting rods (4) at intervals along the length direction of the connecting rods (4). Each support plate (5) is provided with multiple support holes. The internal heating coil (21) includes multiple heating tubes, and the multiple heating tubes are respectively inserted into the multiple support holes.

3. The oxalic acid hydrolysis mixing vessel according to claim 2, characterized in that, A sealing gasket is provided at the connection between the internal heating coil (21) and the connecting flange (3), and a sealing gasket is provided around the opening at the connection between the connecting flange (3) and the hydrolysis mixing vessel.

4. The oxalic acid hydrolysis mixing vessel according to claim 2, characterized in that, Each of the connecting rods (4) is detachably provided with a sleeve (6), and the support plate (5) is fixed to the sleeve (6).

5. The oxalic acid hydrolysis mixing vessel according to claim 4, characterized in that, The support plate (5), the sleeve (6) and the connecting rod (4) are all made of 904 stainless steel.

6. The oxalic acid hydrolysis mixing vessel according to claim 2, characterized in that, Along the circumferential direction of the connecting flange (3), multiple connecting rods (4) are distributed in a ring-shaped interval.

7. The oxalic acid hydrolysis mixing vessel according to claim 2, characterized in that, The internal heating coil (21) is a U-shaped tube, and the number of the support holes is multiple sets. Each set of the support holes includes two rows of support holes distributed at intervals. The two ends of the U-shaped tube are respectively inserted and fixed to the corresponding support holes.

8. The oxalic acid hydrolysis mixing vessel according to claim 7, characterized in that, Each of the U-shaped tubes includes an inlet and an outlet. The inlet is connected to an external steam source, and the outlet is connected to a condensate collector. The U-shaped tube is fixed to the hydrolysis mixing vessel via a connecting flange (3).

9. The oxalic acid hydrolysis mixing vessel according to claim 1, characterized in that, The hydrolysis mixing vessel is made of 904L stainless steel.

10. The oxalic acid hydrolysis mixing vessel according to claim 1, characterized in that, The inner heating coil (21) is made of zirconium, and the outer heating coil (22) is made of 304 stainless steel.

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