Integrated membrane device for recycling waste sulfuric acid

Abstract

The utility model discloses an integrated membrane device for recycling waste sulfuric acid, which relates to the field of sulfuric acid recycling equipment and comprises an upper plate, a lower plate and a plurality of upright posts, the upper plate and the lower plate are fixed by the upright posts to form a support structure, a membrane separation device is assembled on the lower plate, and a nanofiltration feed pump is assembled on the upper plate in a hanging manner. The membrane separation device is composed of 6-8 microfiltration cavities, a buffer cavity and a nanofiltration cavity, the multiple microfiltration cavities, the buffer cavity and the nanofiltration cavity form an axial integrated vertical layout, the microfiltration cavities are separated in a sealed mode, liquid in the cavities does not flow in series, and a discharge port communicated with the buffer cavity is formed in the bottom of each microfiltration cavity. According to the utility model, the microfiltration pretreatment unit and the nanofiltration separation unit are integrally designed, and the buffer cavity and the nanofiltration cavity form an axial integrated vertical layout, so that the problems of more leakage points and large occupied area caused by a large number of external pipelines in the existing distributed structure are avoided, and the installation space and the maintenance cost are saved.

Description

TECHNICAL FIELD

[0001] The utility model relates to sulfuric acid recovery equipment field, especially a kind of integrated membrane device for waste sulfuric acid recovery. BACKGROUND

[0002] With the rapid development of new energy industry and transportation industry, lead-acid battery as an important energy storage and power device, its scrap quantity increases year by year. The electrolyte in waste lead-acid battery contains high concentration sulfuric acid. The conventional treatment method for waste electrolyte includes calcination method, extraction method, neutralization method and membrane separation method. Among them, although the calcination method can realize the deep recovery of sulfuric acid, it has defects such as large equipment investment, high energy consumption and complex operation, and is suitable for high concentration and large scale waste sulfuric acid treatment scene, and is difficult to adapt to the application requirements of small and medium scale enterprises. The extraction method is limited by the selectivity of the extractant, and has problems such as extractant loss and secondary pollution. The purity of recovered sulfuric acid cannot meet the industrial reuse standard. The neutralization method can only realize the harmless treatment of waste sulfuric acid, and cannot recover the sulfuric acid resource, so the resource utilization rate is low. And the membrane separation technology as an efficient and energy-saving separation means, with the advantages of simple operation, low energy consumption and no secondary pollution, has been preliminarily applied in the field of waste sulfuric acid recovery.

[0003] However, the existing membrane separation device has the following problems in practical application. The device is mostly of dispersed structure, the microfiltration pretreatment unit and the nanofiltration separation unit are independently arranged, the pipeline connection is complex, the occupied area is large, and the fluid adaptability between units is poor, so it is difficult to realize stable and efficient operation. In the membrane separation process, the fluid is easy to form concentration polarization layer on the membrane surface, which significantly reduces the separation efficiency and easily affects the recovery rate of sulfuric acid. In addition, the existing microfiltration unit is mostly single-stage or simple series structure, and lacks independent control ability. When the impurity content of the feed fluctuates or local maintenance is needed, it is difficult to realize the operation of the sub-unit, and the processing flexibility is insufficient. UTILITY MODEL CONTENT

[0004] In view of the above problems, the present application provides an integrated membrane device for waste sulfuric acid recovery.

[0005] To achieve the above purpose, the present application provides the following technical scheme: an integrated membrane device for waste sulfuric acid recovery, comprising an upper plate, a lower plate and a plurality of vertical columns, the plurality of vertical columns fixing the upper plate and the lower plate to form a support structure, the lower plate being provided with a membrane separation device, and the upper plate being provided with a nanofiltration feed pump.

[0006] The membrane separation device is composed of 6-8 microfiltration cavities, 1 buffer cavity and 1 nanofiltration cavity. The plurality of microfiltration cavities, buffer cavities and nanofiltration cavities form an axial integrated vertical layout. The microfiltration cavities are sealed and separated from each other, and the liquids in the cavities do not flow into each other. Each microfiltration cavity is provided with a discharge port connected to the buffer cavity.

[0007] The liquid inlet and outlet of the nanofiltration feed pump are connected with the buffer cavity and the nanofiltration cavity through the feed pipe and the discharge pipe, respectively. The waste sulfuric acid in the microfiltration cavity flows into the buffer cavity through the discharge port, and then flows into the nanofiltration cavity through the feed pipe and the discharge pipe under the operation of the nanofiltration feed pump.

[0008] Further, the nanofiltration cavity is provided with a nanofiltration assembly and a nanofiltration water inlet flow state regulating device arranged at the water inlet end of the nanofiltration assembly. The nanofiltration water inlet flow state regulating device is a waist drum shape with a narrow top and a wide bottom. The top of the nanofiltration water inlet flow state regulating device matches the diameter of the discharge pipe, and the bottom matches the diameter of the nanofiltration assembly.

[0009] The inner wall of the nanofiltration water inlet flow state regulating device is fixed with 6-8 groups of flow state regulating blades. The cross section of the flow state regulating blade is a wave shape structure, the height difference between the wave crest and the wave trough is 10-20mm, and the flow state regulating blade is arranged at an angle of 30° relative to the axis of the nanofiltration water inlet flow state regulating device, forming an oblique shear force on the liquid flowing towards the nanofiltration assembly.

[0010] Further, the microfiltration cavity is provided with a tubular microfiltration membrane assembly, and a plurality of microfiltration cavities are provided with a same annular water inlet main pipe. The annular water inlet main pipe is connected with the tubular microfiltration membrane assembly through a plurality of branch interfaces arranged along the circumference of the annular water inlet main pipe. Independent stop valves are arranged on each branch interface for independently controlling the feed flow of each tubular microfiltration membrane assembly.

[0011] Further, the top and bottom of the tubular microfiltration membrane assembly are respectively provided with a water inlet cover plate and a water outlet cover plate. The outer edges of the water inlet cover plate and the water outlet cover plate are respectively sealed with the end of the tubular microfiltration membrane assembly.

[0012] The water inlet cover plate is provided with a liquid inlet interface corresponding to the branch interface of the annular water inlet main pipe for the inlet of waste sulfuric acid. The water outlet cover plate is provided with a liquid outlet interface for discharging concentrated liquid that does not penetrate the microfiltration membrane.

[0013] Further, the nanofiltration assembly includes a nanofiltration membrane element and a nanofiltration permeation pipe arranged inside the nanofiltration membrane element. Sulfuric acid is introduced into the nanofiltration permeation pipe through the nanofiltration membrane element. The side wall of the nanofiltration permeation pipe is provided with a plurality of groups of collection holes for collecting the permeation liquid of sulfuric acid that penetrates the nanofiltration membrane element. The bottom of the nanofiltration permeation pipe is provided with a nanofiltration liquid guide pipe for collecting and leading out the sulfuric acid.

[0014] Further, the bottom of the nanofiltration water inlet flow state regulating device is provided with a piston matching the diameter of the nanofiltration permeation pipe. The piston is provided with two layers of rubber rings for sealing the piston and the port of the nanofiltration permeation pipe.

[0015] Further, the bottom side of the nanofiltration cavity is provided with a nanofiltration concentrated water discharge port for collecting concentrated liquid that does not penetrate the nanofiltration membrane element.

[0016] Further, the membrane separation device has a height-diameter ratio of 1.2-1.5:1, and the total volume ratio of the microfiltration cavity, the buffer cavity and the nanofiltration cavity is 1-2:1:3-8.

[0017] Further, the feed pipe is provided with a one-way valve, the buffer cavity is provided with a liquid level meter for monitoring the microfiltration permeate in the buffer cavity, and the discharge pipe is provided with a pressure gauge.

[0018] In summary, the technical effects and advantages of the utility model are as follows:

[0019] 1. The utility model integrates the microfiltration pretreatment unit and the nanofiltration separation unit, forms an axial integrated vertical layout of the buffer cavity and the nanofiltration cavity, avoids the problems of many leakage points and large floor area caused by a large number of external pipelines in the existing decentralized structure, saves installation space and maintenance cost. Moreover, when the impurity content or solid-liquid load of the waste sulfuric acid feed changes, each unit can be independently started, stopped and adjusted in flow, and the operation combination of the microfiltration unit can be flexibly adjusted, so that the stability of the microfiltration treatment end is ensured.

[0020] 2. The utility model can weaken the high-concentration boundary layer formed on the membrane surface and inhibit the concentration polarization phenomenon through technical means such as strengthening the horizontal flow state and turbulent disturbance. At the same time, due to the controlled concentration polarization, the fluctuation of the transmembrane pressure difference will be reduced, and the service life of the membrane is effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 It is a three-dimensional schematic view of the utility model.

[0023] Figure 2 It is a cross-sectional structure schematic view of the membrane separation device in the utility model.

[0024] Figure 3 It is a top view structure schematic view of the membrane separation device in the utility model.

[0025] Figure 4 It is a relative position schematic view of the tubular microfiltration membrane assembly, the water inlet cover plate and the water outlet cover plate in the utility model.

[0026] Figure 5 It is a cross-sectional structure schematic view of the tubular microfiltration membrane assembly in the utility model.

[0027] Figure 6 This is a cross-sectional view of the nanofiltration component in this utility model.

[0028] Figure 7 This is a schematic diagram of the nanofiltration influent flow regulation device of this utility model.

[0029] Figure 8 This is a schematic diagram of the flow regulation blade in this utility model.

[0030] In the diagram: 11. Upper plate; 12. Lower plate; 13. Column; 2. Membrane separation device; 21. Microfiltration chamber; 2101. Tubular microfiltration membrane module; 2102. Inlet cover; 2102a. Liquid inlet interface; 2103. Outlet cover; 2103a. Liquid outlet interface; 2104. Annular inlet main pipe; 22. Buffer chamber; 2201. Outlet; 2202. Level gauge; 23. Nanofiltration chamber; 2301, Nanofiltration assembly; 2301a, Nanofiltration liquid guide tube; 2302, Nanofiltration feed water flow regulation device; 2302a, Flow regulation blade; 2302b, Piston; 2303, Nanofiltration permeate tube; 2303a, Collection hole; 2304, Nanofiltration membrane element; 2305, Nanofiltration concentrate outlet; 3, Nanofiltration feed pump; 31, Feed pipe; 32, Discharge pipe; 3201, Pressure gauge. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0032] Example 1: Reference Figure 1 , Figure 2 An integrated membrane device for waste sulfuric acid recovery is shown, comprising an upper plate 11, a lower plate 12, and multiple columns 13. The multiple columns 13 fix the upper plate 11 and the lower plate 12 to form a support structure. The device is characterized in that a membrane separation device 2 is mounted on the lower plate 12, and a nanofiltration feed pump 3 is suspended on the upper plate 11.

[0033] The membrane separation device 2 consists of 6-8 microfiltration chambers 21, 1 buffer chamber 22, and 1 nanofiltration chamber 23. The microfiltration chambers 21, buffer chamber 22, and nanofiltration chamber 23 form an axially integrated vertical layout. Each microfiltration chamber 21 is sealed and separated, preventing cross-flow of liquids within each chamber. Each microfiltration chamber 21 has a discharge port 2201 at its bottom, which communicates with the buffer chamber 22. This parallel arrangement allows waste sulfuric acid to have good throughput expansion capability and operational flexibility during the microfiltration stage.

[0034] Further, the liquid inlet and outlet of the nanofiltration feed pump 3 are connected with the buffer cavity 22 and the nanofiltration cavity 23 through the feed pipe 31 and the discharge pipe 32 respectively, and the waste sulfuric acid in the microfiltration cavity 21 is collected into the buffer cavity 22 through the discharge port 2201, and the buffer cavity 22 is used for temporarily storing the microfiltration permeate and buffering and balancing the flow and pressure fluctuations. In the utility model, through the setting of the buffer cavity 22, the operation fluctuation of the microfiltration stage can be avoided to be directly transmitted to the nanofiltration separation stage, so that relatively stable feed conditions are provided for subsequent nanofiltration treatment. After the buffering is completed, under the action of the nanofiltration feed pump 3, the microfiltration permeate in the buffer cavity 22 is transported to the inside of the nanofiltration cavity 23 through the discharge pipe 32, and is used for further separating and recovering the waste sulfuric acid.

[0035] As shown in Figure 2 , Figure 6 and Figure 7 , the nanofiltration cavity 23 is provided with a nanofiltration assembly 2301 and a nanofiltration water inlet flow state regulating device 2302 arranged at the water inlet end of the nanofiltration assembly 2301, the nanofiltration water inlet flow state regulating device 2302 is a waist drum shape with a narrow top and a wide bottom, the top of the nanofiltration water inlet flow state regulating device 2302 matches the pipe diameter of the discharge pipe 32, and the bottom matches the pipe diameter of the nanofiltration assembly 2301. The liquid can be smoothly transitioned before entering the nanofiltration assembly 2301, avoiding violent impact or flow state disorder phenomenon.

[0036] As shown in Figure 8 , the nanofiltration water inlet flow state regulating device 2302 is fixedly provided with 6-8 groups of flow state regulating blades 2302a on the inner wall, the cross section of the flow state regulating blade 2302a is in a wave shape structure, the height difference between the wave crest and the wave trough is 10-20 mm, and the flow state regulating blade 2302a is arranged at an inclination of 30° relative to the axis of the nanofiltration water inlet flow state regulating device 2302. Through the design of the flow state regulating blade 2302a, the liquid entering the nanofiltration assembly 2301 can produce obvious oblique disturbance and tangential shear force while flowing in the axial direction, so as to improve the shear rate, effectively inhibit the concentration polarization phenomenon, and slow down the occurrence of membrane pollution.

[0037] Specifically, as shown in Figure 3 , the microfiltration cavity 21 is provided with a tubular microfiltration membrane assembly 2101, and a plurality of microfiltration cavities 21 are provided with a same annular water inlet main pipe 2104. In order to realize uniform feeding of the multiple cavities, the annular water inlet main pipe 2104 is connected with the tubular microfiltration membrane assembly 2101 through a plurality of branch interfaces arranged along the circumference of the annular water inlet main pipe 2104, and an independent stop valve is arranged on each branch interface, which is used for independently controlling the feeding flow of each tubular microfiltration membrane assembly 2101. Through the setting of the independent stop valve, the feeding flow of each microfiltration cavity 21 can be adjusted individually, or when a certain microfiltration cavity 21 needs to be repaired, backwashed or stopped, the independent operation or exit of the cavity can be realized without stopping the whole system.

[0038] As shown in Figure 4 、 Figure 5 The tubular microfiltration membrane assembly 2101 is provided with a water inlet cover plate 2102 and a water outlet cover plate 2103 at the top and bottom respectively. The outer edges of the water inlet cover plate 2102 and the water outlet cover plate 2103 are sealingly installed with the end portions of the tubular microfiltration membrane assembly 2101, which can be quickly disassembled, replaced or cleaned when needed while ensuring the operation sealing.

[0039] The water inlet cover plate 2102 is provided with a liquid inlet interface 2102a corresponding to the branch interface of the annular water inlet main pipe 2104, which is used to introduce the waste sulfuric acid stock solution into the tubular microfiltration membrane assembly 2101. The water outlet cover plate 2103 is provided with a concentrated liquid outlet interface 2103a for discharging the concentrated liquid that does not penetrate the microfiltration membrane, so that the trapped solid impurities and macromolecular impurities can be discharged from the system in time to avoid accumulation in the microfiltration cavity 21.

[0040] In the utility model, the nanofiltration assembly 2301 includes a nanofiltration membrane element 2304 and a nanofiltration permeation pipe 2303 arranged inside the nanofiltration membrane element 2304. The sulfuric acid is introduced into the nanofiltration permeation pipe 2303 through the nanofiltration membrane element 2304. The side wall of the pipe body of the nanofiltration permeation pipe 2303 is provided with a plurality of collection holes 2303a for collecting the sulfuric acid permeate liquid that penetrates the nanofiltration membrane element 2304. The bottom of the nanofiltration permeation pipe 2303 is provided with a nanofiltration liquid guide pipe 2301a for collecting and discharging the sulfuric acid. Specifically, the sulfuric acid permeate liquid that penetrates the nanofiltration membrane element 2304 enters the nanofiltration permeation pipe 2303 through the collection holes 2303a and is collected downward, and is discharged through the nanofiltration liquid guide pipe 2301a arranged at the bottom of the nanofiltration assembly 2301, so as to realize the recovery of the sulfuric acid.

[0041] The bottom of the nanofiltration water inlet flow state regulating device 2302 is provided with a piston 2302b matched with the pipe diameter of the nanofiltration permeation pipe 2303. The piston 2302b is provided with two layers of rubber rings for sealing the piston 2302b and the port of the nanofiltration permeation pipe 2303, so that the piston 2302b can form a reliable seal with the nanofiltration permeation pipe 2303 in the assembled state, avoiding that the feed liquid directly enters the permeation side bypassing the nanofiltration membrane element 2304.

[0042] The bottom side of the nanofiltration cavity 23 is provided with a nanofiltration concentrated water discharge port 2305 for discharging the concentrated liquid that does not penetrate the nanofiltration membrane element 2304, so as to complete the nanofiltration separation process.

[0043] In the embodiment, the overall height-diameter ratio of the membrane separation device 2 is set to 1.2-1.5:1, which can make the device in the best operating state. When the overall height-diameter ratio is lower than the range, the lateral size of the device increases, and the floor space increases. When the overall height-diameter ratio is higher than the range, the gravity center of the device moves upward, which is not conducive to the stable operation of the device and the on-site installation and maintenance. The total volume ratio of the microfiltration cavity 21, the buffer cavity 22 and the nanofiltration cavity 23 is set to 1-2:1:3-8, which is the result of the optimization design according to the hydraulic retention requirements and load characteristics of different functional units in the waste sulfuric acid treatment process. The microfiltration cavity 21 mainly undertakes the interception of solid impurities and macromolecular impurities, and the effective volume needs to be matched with the membrane area to ensure sufficient lateral flow rate and shear strength. The buffer cavity 22 is a transition unit between the microfiltration cavity 21 and the nanofiltration cavity 23, and the volume is used to balance the flow and pressure fluctuations caused by the parallel operation of multiple microfiltration cavities 21. The nanofiltration cavity 23 undertakes the main functions of sulfuric acid separation and recovery, and needs a relatively larger effective volume to arrange nanofiltration membrane elements and ensure stable transmembrane pressure difference.

[0044] Through the above volume ratio configuration, the functional units can work cooperatively under different operating loads, and the situations of insufficient pretreatment or subsequent nanofiltration overload can be avoided. In addition, the device has a compact overall structure, which is convenient for engineering application.

[0045] As shown in Figure 1 The feed pipe 31 is provided with a one-way valve, which is used to prevent liquid backflow when the system is shut down or the pressure changes, and further improves the safety and reliability of the system operation. The buffer cavity 22 is provided with a liquid level meter 2202 for monitoring the microfiltration permeate in the buffer cavity 22. The liquid level meter 2202 is used to monitor the liquid level change of the microfiltration permeate in the buffer cavity in real time, thereby providing a basis for the start-stop and operating condition adjustment of the nanofiltration feed pump 3. The discharge pipe 32 is provided with a pressure gauge 3201. The pressure gauge 3201 is used to monitor the feed pressure of the nanofiltration membrane, so that the device is in the appropriate working pressure condition.

[0046] It is worth mentioning that, in the utility model, the shells of the microfiltration cavity 21, the buffer cavity 22 and the nanofiltration cavity 23 are made of polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE or metal material lined with polytetrafluoroethylene. The tubular microfiltration membrane assembly 2101 and the nanofiltration assembly 2301 used are acid-resistant membrane elements. Further, the feed pipe 31 and the discharge pipe 32 in contact with the waste sulfuric acid and the remaining connecting pipelines are lined with polytetrafluoroethylene, polyvinylidene fluoride or fluororubber. The piston 2302b used for sealing is made of fluororubber or perfluoroether rubber material which is resistant to strong acid corrosion.

[0047] On the basis of the embodiment 1, in subsequent embodiments, the overall structural composition of the device, the spatial arrangement mode of each functional unit, and the pipeline connection relationship are consistent with those of the embodiment 1, and there is no essential difference in the basic structural form and working principle. The difference lies in that the subsequent embodiments optimize and adjust the number of microfiltration cavities 21 and the structural proportion parameters between the functional cavities for the application scenarios of increasing the treatment scale of waste sulfuric acid or higher compactness requirement of the device on site. By reconfiguring the matching relationship between the microfiltration pretreatment capacity, the buffer flow stabilizing capacity, and the nanofiltration separation capacity, the device can adapt to the requirements of different treatment fluxes and operating conditions under the premise of keeping the overall structure unchanged, as described in the following embodiments 2 and 3:

[0048] Embodiment 2: In this embodiment, the membrane separation device 2 includes 6 microfiltration cavities 21, 1 buffer cavity 22, and 1 nanofiltration cavity 23. Compared with the embodiment 1, this configuration appropriately reduces the number of microfiltration cavities and correspondingly adjusts the volume proportion of each functional cavity.

[0049] In this configuration, the overall height-diameter ratio of the membrane separation device 2 is set to about 1.2:1; the total volume ratio of the microfiltration cavities 21, the buffer cavity 22, and the nanofiltration cavity 23 is set to about 1:1:3; and the height-diameter ratio of the tubular microfiltration membrane assembly 2101 is set to about 3:1.

[0050] Through the above structural proportion setting, the buffer cavity 22 occupies a relatively large effective volume in the overall structure, thereby enhancing the temporary storage and flow stabilization capacity of the microfiltration permeate. When the water quality of the waste sulfuric acid feed fluctuates greatly, the impurity load changes frequently, or there is instantaneous flux imbalance in the microfiltration stage, the buffer cavity 22 can effectively weaken the influence of fluctuations on the nanofiltration assembly 2301, ensure the relative stability of the nanofiltration feed conditions, and be conducive to the long-term stable operation of the nanofiltration membrane. Therefore, this parameter configuration is particularly suitable for medium-scale waste sulfuric acid recovery scenarios with complex feed water quality and large changes in operating conditions.

[0051] Embodiment 3: In this embodiment, the membrane separation device 2 includes 8 microfiltration cavities 21, 1 buffer cavity 22, and 1 nanofiltration cavity 23. This configuration increases the number of microfiltration cavities 21 and simultaneously expands the volume proportion of the nanofiltration cavity 23 to adapt to the continuous operation requirements under higher treatment flux conditions.

[0052] In this configuration, the overall height-diameter ratio of the membrane separation device 2 is set to about 1.5:1; the total volume ratio of the microfiltration cavities 21, the buffer cavity 22, and the nanofiltration cavity 23 is set to about 2:1:8; and the height-diameter ratio of the tubular microfiltration membrane assembly 2101 is set to about 4:1.

[0053] By increasing the number of microfiltration cavities 21, a greater microfiltration treatment area can be provided in a unit of time, thereby improving the overall flux capacity of the pretreatment stage. At the same time, by significantly increasing the volume ratio of the nanofiltration cavities 23 in the overall structure, the nanofiltration separation unit has stronger treatment capacity and more sufficient membrane element arrangement space to match the separation requirements under the condition of high-flux microfiltration effluent. Therefore, this configuration is suitable for engineering application scenarios with larger treatment scale, higher operation load, or higher requirements for unit land occupation treatment capacity of the device.

[0054] The above-mentioned embodiments 2 and 3, by different parameter configuration modes, without changing the basic structure form and working principle of the device, make the integrated membrane device provided by the utility model be able to be flexibly selected and applied according to the different waste sulfuric acid treatment water quantity, impurity load level and on-site installation conditions within the parameter range defined in the claims.

[0055] Finally, it should be noted that: the above only for the preferred embodiments of the utility model, and not for limiting the utility model, although the utility model has been described in detail with reference to the foregoing embodiments, for the person skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the utility model, should be included in the protection scope of the utility model.

Claims

1. An integrated membrane device for spent sulphuric acid recovery, comprising an upper plate (11), a lower plate (12) and a plurality of uprights (13) which fix the upper plate (11) to the lower plate (12) forming a scaffolding structure, characterised in that, The lower plate (12) is equipped with a membrane separation device (2), and the upper plate (11) is hung with a nanofiltration feed pump (3); The membrane separation device (2) is composed of 6-8 microfiltration cavities (21), a buffer cavity (22) and a nanofiltration cavity (23), the plurality of microfiltration cavities (21), the buffer cavity (22) and the nanofiltration cavity (23) form an axial integrated vertical layout, the microfiltration cavities (21) are sealed and separated, the liquid in the cavities does not flow into each other, and each microfiltration cavity (21) is provided with a discharge port (2201) connected with the buffer cavity (22); The liquid inlet and outlet of the nanofiltration feed pump (3) are connected with the buffer cavity (22) and the nanofiltration cavity (23) through the feed pipe (31) and the discharge pipe (32), respectively, the waste sulfuric acid in the microfiltration cavity (21) flows into the buffer cavity (22) through the discharge port (2201), and then flows into the nanofiltration cavity (23) through the feed pipe (31) and the discharge pipe (32) under the operation of the nanofiltration feed pump (3). The nanofiltration cavity (23) is provided with a nanofiltration assembly (2301) and a nanofiltration water inlet flow state regulating device (2302) arranged at the water inlet end of the nanofiltration assembly (2301), the nanofiltration water inlet flow state regulating device (2302) is in the shape of a narrow top and wide bottom, the top of the nanofiltration water inlet flow state regulating device (2302) is matched with the pipe diameter of the discharge pipe (32), and the bottom is matched with the pipe diameter of the nanofiltration assembly (2301). The nanofiltration water inlet flow state regulating device (2302) is provided with 6-8 groups of flow state regulating blades (2302a) fixed on the inner wall, the cross section of the flow state regulating blade (2302a) is in a wave shape structure, the height difference between the wave crest and the wave trough is 10-20 mm, and the flow state regulating blade (2302a) is arranged at an inclination of 30° relative to the axis of the nanofiltration water inlet flow state regulating device (2302), so as to form an inclined shear force on the liquid flowing to the front of the nanofiltration assembly (2301).

2. The integrated membrane device for spent sulfuric acid recovery according to claim 1, characterized in that, The microfiltration cavity (21) is provided with a tubular microfiltration membrane assembly (2101), and a plurality of microfiltration cavities (21) are provided with a same annular water inlet main pipe (2104), the annular water inlet main pipe (2104) is connected with the tubular microfiltration membrane assembly (2101) through a plurality of branch interfaces arranged along the circumference, and each branch interface is provided with an independent stop valve for independently controlling the feed flow of each tubular microfiltration membrane assembly (2101).

3. The integrated membrane device for spent sulfuric acid recovery according to claim 2, characterized in that, The top and bottom of the tubular microfiltration membrane assembly (2101) are respectively provided with a water inlet cover plate (2102) and a water outlet cover plate (2103), and the outer edges of the water inlet cover plate (2102) and the water outlet cover plate (2103) are respectively sealingly installed with the end portions of the tubular microfiltration membrane assembly (2101); The water inlet cover plate (2102) is provided with a liquid inlet interface (2102a) corresponding to the branch interface of the annular water inlet main pipe (2104) for the liquid inlet of the waste sulfuric acid, and the water outlet cover plate (2103) is provided with a liquid outlet interface (2103a) for discharging concentrated liquid not permeating through the microfiltration membrane.

4. The integrated membrane device for spent sulfuric acid recovery according to claim 1, characterized by, The nanofiltration assembly (2301) comprises a nanofiltration membrane element (2304) and a nanofiltration permeation pipe (2303) arranged inside the nanofiltration membrane element (2304), sulfuric acid is introduced into the nanofiltration permeation pipe (2303) through the nanofiltration membrane element (2304), the pipe wall of the nanofiltration permeation pipe (2303) is provided with a plurality of groups of collection holes (2303a) for collecting the sulfuric acid permeate liquid that permeates the nanofiltration membrane element (2304), and the bottom of the nanofiltration permeation pipe (2303) is provided with a nanofiltration liquid guide pipe (2301a) for centralized collection and leading out of the sulfuric acid.

5. The integrated membrane device for spent sulfuric acid recovery according to claim 4, characterized in that, The nanofiltration water inlet flow state regulating device (2302) is provided at the bottom with a piston (2302b) matched with the pipe diameter of the nanofiltration permeation pipe (2303), and the piston (2302b) is provided with two layers of rubber rings for sealing the piston (2302b) and the port of the nanofiltration permeation pipe (2303).

6. The integrated membrane device for spent sulfuric acid recovery according to claim 4, characterized by, The bottom side of the nanofiltration cavity (23) is provided with a nanofiltration concentrated water discharge port (2305) for collecting concentrated liquid that does not permeate the nanofiltration membrane element (2304).

7. The integrated membrane device for spent sulfuric acid recovery according to claim 1, characterized by, The membrane separation device (2) has a height-diameter ratio of 1.2-1.5:1, and the total volume ratio of the microfiltration cavity (21), the buffer cavity (22) and the nanofiltration cavity (23) is 1-2:1:3-8.

8. The integrated membrane device for spent sulfuric acid recovery according to claim 1, characterized by, A one-way valve is mounted on the feed pipe (31), a liquid level meter (2202) for monitoring the microfiltration permeate liquid in the buffer cavity (22) is mounted on the buffer cavity (22), and a pressure gauge (3201) is mounted on the discharge pipe (32).

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