A method and system for solid-liquid separation of flocculated material

Abstract

The present application relates to a kind of solid-liquid separation method and solid-liquid separation system of flocculation material, the solid-liquid separation method and solid-liquid separation system provided by the present application make flocculation material complete solid-liquid separation under the working condition of closed, inert gas protection, the liquid phase produced in solid-liquid separation process is used as circulating detergent, countercurrent displacement washing is carried out to filter cake, can efficiently remove the impurity components wrapped and adsorbed by filter cake, realize liquid phase recycling, effectively reduce VOC emission.The whole process avoids the mechanical ignition risk brought by high-speed centrifugation from source, relies on closed inhibition gas phase space, inert gas protection, safety interlock unit monitoring and other means to build explosion-proof system, while guaranteeing solid-liquid separation effect and operation safety.Suitable for industrialized continuous production of solution-polymerized styrene-butadiene rubber and other wet rubber compound, complete continuous production line is formed by connecting front-end continuous ultrasonic flocculation, rear-end extrusion dewatering drying unit.

Description

Technical Field

[0001] This invention relates to the field of rubber wet mixing technology, and in particular to a solid-liquid separation method and system for flocculated materials. Background Technology

[0002] Solvent-based wet mixing technology involves pre-dispersing fillers such as silica in an organic solvent, mixing it with solution-polymerized rubbers such as styrene-butadiene rubber (SSBR), and then obtaining the masterbatch through flocculation, solid-liquid separation, and dehydration drying. The primary solid-liquid separation of the flocculated material is a crucial intermediate step connecting flocculation and deep dehydration drying.

[0003] In existing technologies, this process often employs open or semi-closed filtration, vibrating sieving, or high-speed centrifugation. For example, some wet-process rubber compounding routes use vibrating screens to separate agglomerated particles, or use 4000 rpm high-speed centrifuges to centrifuge the flocculent masterbatch. These methods present significant problems when applied to organic solvent systems: First, commonly used solvents such as cyclohexane and n-hexane have low flash points (n-hexane flash point approximately -22℃, cyclohexane flash point approximately -18℃) and wide explosion limits. Mechanical friction and static electricity buildup in the rotating parts of the high-speed centrifuge can create ignition sources, making it the highest-risk equipment type under these conditions. Second, the strong shearing action of high-speed centrifugation on the flocs causes floc breakage and increases the fine powder entrainment rate, resulting in material loss and contamination of the liquid phase recovery system. Third, open or semi-open operations lead to significant solvent evaporation, resulting in high losses and difficulty in controlling the concentration of combustible gases on-site. Fourth, the flocs obtained from chemical flocculation exhibit significant variations in particle size and high fine powder content, leading to low filtration rates and further forcing producers to rely on high-speed centrifugation.

[0004] Although general explosion-proof equipment such as explosion-proof centrifuges and nitrogen protection devices for centrifuges have been publicly available in the chemical industry, they only solve the problem of "explosion-proof equipment body" and do not provide process-level solutions for the material characteristics of rubber flocculent materials, such as "whether high-speed centrifugation is required and how to avoid high-speed centrifugation".

[0005] Therefore, how to provide a safe solid-liquid separation method and system that matches the characteristics of flocculated materials, avoids high mechanical energy input from the source, and has a closed-loop solvent recovery is an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a solid-liquid separation method and system for flocculated materials, which takes into account intrinsic safety and explosion protection, material floc protection, and liquid phase recycling. It is connected to a front-end continuous ultrasonic flocculation unit and a rear-end extrusion dehydration and drying unit to form a complete continuous production line, which is suitable for the industrial continuous production of wet-process masterbatch rubber such as solution-polymerized styrene-butadiene rubber.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a solid-liquid separation system for flocculated materials, the solid-liquid separation system comprising a solid-liquid separation unit 1, a countercurrent displacement washing unit 2, an inert gas protection unit 3, a safety interlock unit 4, and a liquid phase recovery unit 5; The solid-liquid separation unit 1 includes a sealed vacuum desliming device 11; The vacuum dehydration device 11 includes a vacuum dehydration zone, a washing zone, and a post-wash dehydration zone along the material travel direction; The countercurrent displacement washing unit 2 includes a spray device 21 and a liquid collection device 22; The spraying device 21 is located above the washing area and is used to spray washing liquid onto the filter cake below. The liquid collection device 22 is located below the vacuum desolution zone, the washing zone and the post-wash desolution zone, and is used to receive the circulating washing liquid after passing through the filter cake and the liquid phase generated after vacuum desolution. The inert gas protection unit 3 is connected to the solid-liquid separation unit 1 to form a closed loop, providing an inert gas protection atmosphere for the solid-liquid separation unit. The safety interlock unit 4 is electrically connected to the solid-liquid separation unit 1; The liquid phase recovery unit 5 is connected to the countercurrent displacement washing unit 2.

[0008] The solid-liquid separation system provided by this invention includes a solid-liquid separation unit, a countercurrent displacement washing unit, an inert gas protection unit, a safety interlock unit, and a liquid phase recovery unit. The solid-liquid separation unit includes a vacuum dewatering device, which is divided into dewatering, washing, and post-wash dewatering zones. Combined with the spray and collection structure of the countercurrent displacement washing unit, it can fully penetrate the filter cake and displace the mother liquor (containing residual filler powder, additives, etc.) entrained in the flocs, effectively improving the purity of the filter cake. The liquid phase recovery structure enables the recycling of the washing liquid, balancing treatment efficiency and energy conservation and environmental protection. The sealed solid-liquid separation unit is equipped with an inert gas protection unit to eliminate flammable and explosive safety hazards. Simultaneously, the system is equipped with a safety interlock unit that collects the operating parameters of each unit in real time and implements interlock control, enabling timely handling of abnormal operating conditions and ensuring continuous and stable operation of the equipment.

[0009] Preferably, the solid-liquid separation unit 1 further includes a sealed gravity settling device 12 disposed upstream of the vacuum dehydration device 11 and connected to the vacuum dehydration device 11.

[0010] In this invention, the solid-liquid separation unit can also be configured as a graded structure with a gravity sedimentation device and a vacuum dehydration device connected in a closed series. The sedimentation pretreatment is performed first, followed by vacuum dehydration, which can effectively reduce the filtration load, reduce solid loss, and significantly improve the solid-liquid separation efficiency and solid phase recovery rate.

[0011] Preferably, the gas phase space in the sealed vacuum dehydration device 11 is connected to the inert gas protection unit 3.

[0012] Preferably, the sealed gravity settling device 12 is a fully liquid sealed structure with no gas phase space inside, or the gas phase space is connected to the inert gas protection unit 3.

[0013] The vacuum desolvation device and gravity sedimentation device used in this invention are both closed structures and are circulated with the inert gas protection unit. They can suppress the oxygen content in the gas phase atmosphere inside the device, reduce the risk of combustible vapors formed by the volatilization of organic solvents forming an explosive mixture with oxygen, and even if a large amount of solvent volatilizes during the filtration process, the oxygen concentration of the system can be controlled below the explosion limit, thus achieving inertization and explosion protection of the system and avoiding the hidden danger of combustion and explosion inside the device.

[0014] Preferably, the sealed vacuum desiccant device 11 includes a sealing cover 1101, a conveying filter belt 1102, and a vacuum chamber 1103.

[0015] Preferably, the conveyor filter belt 1102 passes through the inside of the sealed cover 1101, and the vacuum box 1103 is disposed on the lower side of the conveyor filter belt 1102, corresponding to the vacuum dehydration zone and the post-wash dehydration zone, respectively.

[0016] Preferably, the conveyor filter belt 1102 is a conductive filter cloth, which is grounded to release the charge accumulated on the filter belt. The grounding resistance is ≤10 Ω, for example, it can be 1 Ω, 2 Ω, 4 Ω, 5 Ω, 6 Ω, 8 Ω or 10 Ω, etc.

[0017] Preferably, the inert gas protection unit 3 includes a circulating fan 31, a condenser 32, and a solvent collection tank 33 connected in sequence. The gas phase outlet of the condenser 32 is connected to the inlet of the circulating fan 31, the outlet of the circulating fan 31 is connected to the inert gas interface of the solid-liquid separation unit 1, and the liquid phase outlet of the condenser 32 is connected to the solvent collection tank 33. When the solid-liquid separation system is running, the vapor carrying liquid enters the condenser 32 from the vapor outlet of the solid-liquid separation unit, the condensed gas returns to the inert gas interface via the circulating fan 31, and the condensate enters the solvent collection tank 33, realizing closed-loop circulation of inert gas and vapor recovery.

[0018] Preferably, when the solid-liquid separation unit 1 is a vacuum dehydration device 11, its inert gas interface and steam outlet are provided on the sealing cover 1101, the inert gas interface is connected to the outlet of the circulating fan 31, and the steam outlet is connected to the inlet of the condenser 32.

[0019] Preferably, when the solid-liquid separation unit 1 is a combination of a gravity settling device 12 and a vacuum desliming device 11, its inert gas interface and steam outlet are provided on the sealing cover 1101, the inert gas interface is connected to the outlet of the circulating fan 31, and the steam outlet is connected to the inlet of the condenser 32; when the gravity settling device 12 has a gas phase space, the gas phase space of the gravity settling device 12 is provided with an inert gas interface and a steam outlet; the inert gas interface of the gravity settling device 12 is connected to the outlet of the circulating fan 31, and the steam outlet of the gravity settling device 12 is connected to the inlet of the condenser 32.

[0020] Preferably, the solid-liquid separation system is further provided with a connection sealing device 6.

[0021] Preferably, the sealing device 6 at the connection point is located at the rotating connection point that passes through the sealed boundary of each device in the solid-liquid separation system, including the position where the shaft of the drive roller and / or redirecting roller of the conveying filter belt 1102 extends through the sealing cover 1101, and the position where the shaft of the circulating fan 31 connects to the housing.

[0022] Preferably, the connection sealing device 6 includes any one or a combination of at least two of the following: a labyrinth seal, a mechanical seal, or a nitrogen seal.

[0023] Preferably, the spraying device 21 can be configured as a multi-stage structure, with each stage of the spraying device arranged sequentially along the filter cake transport direction in the vacuum desliming device. Each stage of the spraying device is provided with an independent liquid collection device 22 below it. The last stage of the spraying device along the filter cake travel direction is connected to the circulating washing liquid outlet of the liquid phase recovery unit 5. The outlet of the subsequent stage liquid collection device is connected to the inlet of the previous stage spraying device. The first stage liquid collection device is connected to the inlet of the liquid phase recovery unit 5, so that the washing liquid is applied step by step in the opposite direction to the filter cake travel direction, realizing multi-stage countercurrent replacement washing.

[0024] Preferably, the liquid phase recovery unit 5 includes a mother liquor storage tank 51, a distillation recovery system 52, and a circulating liquid storage tank 53 connected in sequence.

[0025] Preferably, when the countercurrent displacement washing unit 2 has a single-stage structure, the liquid collection device 22 of the vacuum dehydration zone is connected to the mother liquor storage tank 51.

[0026] Preferably, when the countercurrent displacement washing unit 2 has a multi-stage structure, the first-stage liquid collection device along the filter cake traveling direction in the multi-stage structure is connected to the mother liquor storage tank 51.

[0027] Preferably, when the countercurrent displacement washing unit 2 has a single-stage structure, the circulating liquid storage tank 53 is connected to the spray device 21.

[0028] Preferably, when the countercurrent displacement washing unit 2 has a multi-stage structure, the circulating liquid storage tank 53 is connected to the last stage spray device in the multi-stage spray structure along the filter cake traveling direction.

[0029] When this invention employs multi-stage spraying, the last-stage spraying device along the material's travel direction is supplied with circulating washing liquid recovered through distillation from the circulating liquid storage tank in the liquid phase recovery unit; this is called "fresh circulating washing liquid." The circulating washing liquid collected by the subsequent-stage collection device is sequentially sent to the preceding-stage spraying device; this is called "recycled liquid." The first-stage collection device discharges liquid into the mother liquor storage tank in the liquid phase recovery unit, ensuring that the overall flow direction of the circulating washing liquid is opposite to the filter cake's travel direction, thus achieving countercurrent recycling at each stage. Compared to single-stage spraying, this structure can improve the mother liquor replacement efficiency and reduce solid entrainment with the same amount of fresh recovered washing liquid.

[0030] Preferably, the number of stages of the spraying device is set to 2-4 stages, for example, it can be 2 stages, 3 stages or 4 stages.

[0031] Preferably, the safety interlocking unit 4 includes an online oxygen content monitoring device 41, an online combustible gas concentration monitoring device 42, and an interlocking control module 43.

[0032] In this invention, the drive motor of the conveyor belt 1102, the circulating fan 31, the online oxygen content monitoring device 41, the online combustible gas concentration monitoring device 42, and the interlocking control module 43, as well as the various liquid transfer pumps in the system, located within the explosion hazard zone, are equipped with explosion-proof and / or intrinsically safe electrical equipment that meets the explosion-proof requirements of the hazardous area. The explosion hazard zone refers to the area surrounding the equipment that may form an explosive gas atmosphere, as determined according to the explosion hazard zone classification requirements for organic solvent media, including the drive motor of the conveyor belt 1102, the circulating fan 31, the liquid transfer pumps, and the online oxygen content monitoring device 41, the online combustible gas concentration monitoring device 42, and the interlocking control module 43.

[0033] In a second aspect, the present invention provides a method for solid-liquid separation of flocculated materials, wherein the solid-liquid separation system for flocculated materials as described in the first aspect is used to perform solid-liquid separation of the flocculated materials, the solid-liquid separation method comprising: The flocculated material is subjected to solid-liquid separation, washing, and post-washing dehydration under a closed environment and inert gas protection to obtain a solid phase and a liquid phase. The average particle size of the flocs in the flocculated material is 0.5~5 mm.

[0034] The range of 0.5 to 5 mm can be, for example, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. Preferably, the flocculated material is a flocculent material obtained by ultrasonic flocculation of a solvent-based composite liquid.

[0035] Preferably, the average particle size of the flocs is 1 to 4 mm, for example, 1 mm, 2 mm, 3 mm or 4 mm.

[0036] The solid-liquid separation method for flocculated materials provided by this invention is applicable to flocculated materials with an average particle size of 0.5~5 mm. This flocculated material is obtained after ultrasonic flocculation treatment. If the average particle size of the flocs is less than 0.5 mm, the flocs are too fine, the filtration rate drops sharply, and the entrainment rate of fine powder penetrating the filter medium increases. In production, it may even be necessary to return to high-speed centrifugation, thus losing the safety advantage of this invention. If the average particle size of the flocs is greater than 5 mm, too much mother liquor is entrained inside the flocs, the countercurrent displacement washing efficiency decreases, and the solvent entrainment loss increases. Under conditions of full liquid sealing and inert gas protection, the flocculated material undergoes solid-liquid separation. The liquid phase produced during the solid-liquid separation process is used as a circulating washing agent to perform countercurrent displacement washing on the filter cake. The inert gas is recycled in a closed loop, and after condensation to remove liquid phase vapor, it is reused. An online oxygen content monitoring device (oxygen volume concentration is below 60% of the limiting oxygen concentration and preferably not exceeding 8%, and the machine is interlocked to stop when it exceeds the set value) and an online combustible gas concentration monitoring device (the machine is interlocked to stop when the combustible gas concentration reaches 25% of the lower explosive limit) form a dual safety interlock monitoring system, which realizes continuous solid-liquid separation with intrinsic safety, low entrainment, and high solvent recovery rate.

[0037] Preferably, the inert gas includes nitrogen.

[0038] Preferably, the solid-liquid separation includes vacuum dehydration.

[0039] Preferably, the solid-liquid separation further includes gravity sedimentation before vacuum dehydration.

[0040] Preferably, the residence time of the material during gravity settling is 5 to 30 minutes, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0041] Preferably, the vacuum degree of the vacuum dehydration is 0.02~0.08 MPa, for example, it can be 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa or 0.08 MPa, etc.

[0042] Preferably, the filter medium used for vacuum desliming has a mesh size of 100 to 400 mesh, such as 100 mesh, 200 mesh, 300 mesh or 400 mesh.

[0043] Preferably, during the vacuum dehydration process, the material travels at a speed of 0.5 to 5 m / min along the conveyor belt, for example, 0.5 m / min, 1 m / min, 2 m / min, 3 m / min, 4 m / min, or 5 m / min.

[0044] Preferably, the vacuum degree of the post-washing and descaling process is 0.02~0.08 MPa, for example, it can be 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa or 0.08 MPa, etc.

[0045] Preferably, the material residence time during vacuum dehydration is 1 to 5 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, or 5 minutes; the material residence time during washing is 1 to 10 minutes, for example, 1 minute, 2 minutes, 3 minutes, 5 minutes, 8 minutes, or 10 minutes; and the material residence time during post-wash dehydration is 1 to 5 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, or 5 minutes.

[0046] Preferably, the circulating washing liquid used in the washing process is obtained by distillation and recovery of the liquid phase produced during the solid-liquid separation process.

[0047] Preferably, the total amount of the circulating washing liquid is calculated based on the circulating washing liquid entering the washing zone from the liquid phase recovery unit, and its mass ratio to the solid phase mass in the flocculant is (0.3~2):1, for example, it can be 0.3:1, 0.5:1, 0.8:1, 1:1, 1.3:1, 1.5:1, 1.8:1 or 2:1, etc.; in multi-stage washing, the liquid used between each stage is not counted repeatedly in the amount of fresh circulating washing liquid.

[0048] Preferably, the liquid content of the solid material is 40-60%, for example, it can be 40%, 45%, 50%, 55% or 60%.

[0049] This invention employs countercurrent displacement washing, where the recovered liquid is used to wash the filter cake. The washing liquid is recycled in a countercurrent manner. Under the condition that the total amount used is only 0.3 to 2 times the solid phase mass in the flocculant, the mother liquor (containing residual filler powder and additives) entrained in the flocs is fully replaced. After washing, the solid phase liquid content is 40 to 60%, which can be directly connected to the subsequent extrusion dehydration process. The liquid phase is distilled to recover organic solvents and antisolvents for recycling, and the recovery rate can reach more than 95%.

[0050] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention provides a solid-liquid separation method and system for flocculated materials that abandons the traditional high-speed centrifugal separation process and completely eliminates the mechanical ignition source generated by high-speed friction and impact from the source. At the same time, it is equipped with multiple protection measures such as a sealed solid-liquid separation unit, an inert gas protection unit, a safety interlock unit, and a sealing device at the grounding connection of the conductive filter cloth to prevent air infiltration and static electricity accumulation, and to build a comprehensive and highly reliable explosion-proof safety system.

[0051] (2) The solid-liquid separation method used in this invention has no high-speed shearing force throughout the process, which can completely protect the flocculated floc structure of the material and effectively reduce the fine powder entrainment rate. The original dispersion morphology of the filler will not be damaged throughout the process, and the excellent dispersion performance of the material can be maintained stably, which can greatly ensure and improve the dispersion level of the flocculent material and ensure the uniform and stable quality of the finished product.

[0052] (3) The present invention adopts a countercurrent displacement washing process to recycle the separated and recovered liquid phase as washing liquid, which efficiently removes filter cake impurities. At the same time, it is equipped with an integrated process of distillation recovery and condensation reuse to realize the closed-loop recycling of washing liquid, which greatly improves the overall solvent recovery rate, reduces organic solvent loss from the source of the process, significantly reduces VOC emissions during the production process, and is green, environmentally friendly and has lower production costs.

[0053] (4) The present invention adopts a closed belt vacuum dehydration equipment, which can realize long-term stable continuous automated operation and break the limitations of intermittent production. This process unit can be perfectly connected to the front-end continuous ultrasonic flocculation process, and can also be directly linked to the back-end extrusion dehydration and drying processes. The whole process is smoothly connected and does not require manual transfer, thus building an integrated continuous production line that is suitable for large-scale stable industrial production. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the solid-liquid separation system for flocculated materials provided by the present invention; Among them, 1-solid-liquid separation unit, 11-vacuum dehydration device, 12-gravity sedimentation device, 1101-sealed cover, 1102-conveyor filter belt, 1103-vacuum box; 2-Countercurrent displacement washing unit, 21-Spray device, 22-Liquid collection device; 3-Inert gas protection unit, 31-Circulating fan, 32-Condenser, 33-Solvent collection tank; 4-Safety interlock unit; 41-Online oxygen content monitoring device; 42-Online combustible gas concentration monitoring device; 43-Interlock control module; 5-Liquid phase recovery unit, 51-Mother liquor storage tank, 52-Distillation recovery system, 53-Circulating liquid storage tank; 6-Sealing device at the connection point. Detailed Implementation

[0055] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0056] Preparation Example 1 This preparation example provides a flocculant, which is prepared by the following method: A composite solution was obtained by mixing 667 parts by weight of SSBR-cyclohexane polymer solution (containing 100 parts by weight of SSBR) and Si-69 modified silica pre-dispersion solution (containing 60 parts by weight of silica, 4.8 parts by weight of Si-69, and 80 parts by weight of cyclohexane) at 50℃ and 800 rpm for 10 min. The composite solution was then contacted with 95% ethanol (mass ratio 1.5:1) in a flooded tubular reactor in a continuous flow manner. Ultrasonic flocculation was performed for 30 s at a power density of 3 kW / L, a frequency of 20 kHz, a duty cycle of 50%, and 30℃ to obtain flocculent material with an average particle size of approximately 2.8 mm.

[0057] Preparation Example 2 This preparation example provides a flocculant, which is prepared by the following method: 667 parts by weight of SSBR-cyclohexane polymer solution containing 15 wt% (containing 100 parts by weight of SSBR) and Si-69 modified silica pre-dispersion solution (containing 60 parts by weight of silica, 4.8 parts by weight of Si-69, and 80 parts by weight of cyclohexane) were mixed at 50℃ and 800 rpm for 10 min to obtain a composite solution. The composite solution was then contacted with 95% ethanol (mass ratio 1.5:1) in a flooded tubular reactor in a continuous flow manner, and ultrasonic flocculation was performed for 120 s at a power density of 0.5 kW / L, a frequency of 20 kHz, a duty cycle of 50%, and 30℃ to obtain flocculent material with an average particle size of approximately 4.5 mm.

[0058] Preparation Example 3 This preparation example provides a flocculant, which is prepared by the following method: 667 parts by weight of SSBR-cyclohexane polymer solution containing 15 wt% (containing 100 parts by weight of SSBR) and Si-69 modified silica pre-dispersion solution (containing 60 parts by weight of silica, 4.8 parts by weight of Si-69, and 80 parts by weight of cyclohexane) were mixed at 50℃ and 800 rpm for 10 min to obtain a composite solution. The composite solution was then contacted with 95% ethanol (mass ratio 1.5:1) in a flooded tubular reactor in a continuous flow manner, and ultrasonic flocculation was performed for 10 s at a power density of 10 kW / L, a frequency of 20 kHz, a duty cycle of 50%, and 30℃ to obtain flocculent material with an average particle size of approximately 0.3 mm.

[0059] For ease of comparison between embodiments, unless otherwise stated, Embodiments 1-5 and Comparative Example 2 all employ a continuous feeding method, with a continuous feeding capacity of 100 kg / h for wet flocculated material. Comparative Examples 1 and 3 employ a batch centrifugation method, with a batch processing capacity of 20 kg of wet flocculated material per batch. The above processing capacities are merely exemplary operating conditions under the equipment scale used in this embodiment and do not constitute a limitation on the processing capacity of the present invention. The actual processing capacity can be adjusted according to the scale of the device, the effective filtration area, the filter belt speed, and the properties of the material.

[0060] Example 1 This embodiment provides a solid-liquid separation method and system for flocculated materials. The solid-liquid separation system includes a solid-liquid separation unit 1, a gravity settling device 12, a vacuum desliming device 11, a sealed cover 1101, a conveyor filter belt 1102, and a vacuum box 1103; a countercurrent displacement washing unit 2, a spray device 21, and a liquid collection device 22 (equipped with two-stage spray devices and corresponding independent liquid collection devices); an inert gas protection unit 3, a circulating fan 31, a condenser 32, and a solvent collection tank 33; a safety interlock unit 4, an online oxygen content monitoring device 41, a combustible gas concentration online monitoring device 42, and an interlock control module 43; a liquid phase recovery unit 5, a mother liquor storage tank 51, a distillation recovery system 52, and a circulating liquid storage tank 53; and a connection sealing device 6. Based on wet flocculated materials, the continuous feed rate in this embodiment is 100 kg / h.

[0061] The gravity settling device 12 is connected to the vacuum desliming device 11. A spray device 21 is positioned above the corresponding washing zone of the vacuum desliming device 11, including a first-stage spray device and a second-stage spray device along the filter cake travel direction. A liquid collection device 22 is positioned in the vacuum desliming zone, washing zone, and post-wash desliming zone of the vacuum desliming device 11, including a first-stage liquid collection device and a second-stage liquid collection device along the filter cake travel direction in the washing zone. The second-stage spray device is connected to the circulating liquid storage tank 53, and the second-stage liquid collection device is connected to the first-stage spray device. The first-stage liquid collection device is connected to the mother liquor storage tank 51. In the liquid phase recovery unit 5, the mother liquor storage tank 51, the distillation recovery system 52, and the circulating liquid storage tank 53 are sequentially connected. The inert gas protection unit 3 includes... A circulating fan 31, a condenser 32, and a solvent collection tank 33 are connected in sequence. The gas phase outlet of the condenser 32 is connected to the inlet of the circulating fan 31, the outlet of the circulating fan 31 is connected to the inert gas interface of the solid-liquid separation unit 1, and the liquid phase outlet of the condenser 32 is connected to the solvent collection tank 33. The sealing cover 1101 in the vacuum dehydration device 11 and the gravity settling device 12 are both equipped with inert gas interfaces and vapor outlets. The inert gas interfaces are all connected to the outlet of the circulating fan 31, and the vapor outlets are all connected to the inlet of the condenser 32. The online oxygen content monitoring device 41, the online combustible gas concentration monitoring device 42, and the interlocking control module 43 are electrically connected to the vacuum dehydration device 11 and the gravity settling device 12, respectively.

[0062] The solid-liquid separation method includes: The flocculent material obtained in Preparation Example 1 was fed into a sealed gravity settling device at a continuous feed rate of 100 kg / h for settling (full liquid, sealed, oxygen volume concentration controlled ≤8% in the gravity settling device, connected to an inert gas protection unit for closed-loop circulation). After settling for 15 min, a flocculent material settling layer and supernatant were formed. The material in the settling layer was then conveyed to a sealed vacuum desliming device (vacuum degree in the vacuum desliming zone and the post-wash desliming zone was 0.05 MPa, the conveyor filter belt was a 200-mesh conductive filter cloth and grounded, the conveyor filter belt travel speed was 2 m / min, the material residence time in the vacuum desliming zone was 2 min, the material residence time in the washing zone was 3 min, and the material residence time in the post-wash desliming zone was 2 min). (The sealed cover gas phase space is connected to the inert gas protection unit for closed-loop circulation). Vacuum dehydration is carried out in the vacuum dehydration zone. After dehydration, the filter cake undergoes two-stage countercurrent displacement washing in the washing zone. The amount of fresh circulating washing liquid entering the second-stage spray device from the circulating liquid storage tank is 1 times the mass of the solid phase in the flocculant. The liquid collected by the second-stage collection device is reused in the first-stage spray device, and the liquid discharged from the first-stage collection device enters the mother liquor storage tank. After washing, the filter cake undergoes dehydration again in the post-wash dehydration zone to obtain solid material and liquid phase.

[0063] Example 2 This embodiment provides a solid-liquid separation method and system for flocculated materials. The solid-liquid separation system includes a solid-liquid separation unit 1, a gravity settling device 12, a vacuum descaling device 11, a sealed cover 1101, a conveyor filter belt 1102, and a vacuum box 1103; a countercurrent displacement washing unit 2, a spray device 21, and a liquid collection device 22 (equipped with three-stage spray devices and corresponding independent liquid collection devices); an inert gas protection unit 3, a circulating fan 31, a condenser 32, and a solvent collection tank 33; a safety interlock unit 4, an online oxygen content monitoring device 41, a combustible gas concentration online monitoring device 42, and an interlock control module 43; a liquid phase recovery unit 5, a mother liquor storage tank 51, a distillation recovery system 52, and a circulating liquid storage tank 53; and a connection sealing device 6. Based on wet flocculated materials, the continuous feed rate in this embodiment is 100 kg / h.

[0064] The gravity settling device 12 is connected to the vacuum desliming device 11. A spray device 21 is positioned above the washing zone of the vacuum desliming device 11, and includes a first-stage spray device, a second-stage spray device, and a third-stage spray device along the filter cake's travel direction. A liquid collection device 22 is positioned in the vacuum desliming device 11 corresponding to the vacuum desliming zone, washing zone, and post-wash desliming zone. In the washing zone, it includes a first-stage liquid collection device, a second-stage liquid collection device, and a third-stage liquid collection device along the filter cake's travel direction. The third-stage spray device is connected to the circulating liquid storage tank 53, the third-stage liquid collection device is connected to the second-stage spray device, the second-stage liquid collection device is connected to the first-stage spray device, and the first-stage liquid collection device is connected to the mother liquor storage tank 51. The mother liquor storage tank 51 and the refined liquid storage tank 51 in the liquid phase recovery unit 5... The distillation recovery system 52 and the circulating liquid storage tank 53 are connected in sequence; the inert gas protection unit 3 includes a circulating fan 31, a condenser 32 and a solvent collection tank 33 connected in sequence, the gas phase outlet of the condenser 32 is connected to the inlet of the circulating fan 31, and the liquid phase outlet of the condenser 32 is connected to the solvent collection tank 33; the sealing cover 1101 in the vacuum dehydration device 11 and the gravity settling device 12 are both provided with inert gas interface and vapor outlet, the inert gas interface is connected to the outlet of the circulating fan 31, and the vapor outlet is connected to the inlet of the condenser 32; the online oxygen content monitoring device 41, the combustible gas concentration online monitoring device 42 and the interlocking control module 43 are electrically connected to the vacuum dehydration device 11 and the gravity settling device 12 respectively.

[0065] The solid-liquid separation method includes: The flocculent material obtained in Preparation Example 1 was fed into a sealed gravity settling device at a continuous feed rate of 100 kg / h for settling (full liquid, sealed, oxygen volume concentration controlled ≤8% in the gravity settling device, connected to an inert gas protection unit for closed-loop circulation). After settling for 15 min, a flocculent material settling layer and supernatant were formed. The material in the settling layer was then conveyed to a sealed vacuum desliming device (the vacuum degree in the vacuum desliming zone and the post-wash desliming zone was 0.05 MPa, the conveyor filter belt was a 200-mesh conductive filter cloth and grounded, the conveyor filter belt travel speed was 2 m / min, and the material residence times in the vacuum desliming zone, washing zone, and post-wash desliming zone were 2 min, 3 min, and 2 min, respectively). (Min, the sealed cover gas phase space is connected to the inert gas protection unit closed-loop circulation), vacuum dehydration is carried out in the vacuum dehydration zone; the dehydrated filter cake enters the washing zone for three-stage countercurrent displacement washing, based on the fresh circulating washing liquid entering the third-stage spray device from the circulating liquid storage tank, its amount is 0.6 times the mass of the solid phase in the flocculant; the recycled liquid collected by the third-stage collection device is reused in the second-stage spray device, the recycled liquid collected by the second-stage collection device is reused in the first-stage spray device, and the liquid discharged from the first-stage collection device enters the mother liquor storage tank; the washed filter cake is dehydrated again in the post-wash dehydration zone to obtain solid material and liquid phase.

[0066] Example 3 This embodiment provides a solid-liquid separation method and system for flocculated materials. The difference from Example 1 is that the flocculated material of the same mass as that obtained in Preparation Example 1 is replaced with the flocculated material obtained in Preparation Example 2; all other conditions are the same as those in Example 1, and the continuous feed rate is 100 kg / h.

[0067] Example 4 This embodiment provides a solid-liquid separation method and system for flocculated materials. The difference from Embodiment 1 is that the countercurrent displacement washing unit 2 is only equipped with a single-stage spray device 21 and a corresponding liquid collection device 22. The spray device 21 is connected to the circulating liquid storage tank 53, and the liquid collection device 22 is connected to the mother liquor storage tank 51. There is no interstage washing liquid reflux. The rest of the system structure is the same as that of Embodiment 1, and the continuous feed processing capacity is 100 kg / h.

[0068] The solid-liquid separation method includes: The flocculent material obtained in Preparation Example 1 was processed under the gravity sedimentation and vacuum dehydration conditions of Example 1. The material residence times in the vacuum dehydration zone, washing zone, and post-wash dehydration zone were 2 min, 3 min, and 2 min, respectively. The dehydrated filter cake was washed in the washing zone using a single-stage spray displacement washing method. The circulating washing liquid was directly supplied to the spray device from the circulating liquid storage tank. The amount of circulating washing liquid was 1 times the mass of the solid phase in the flocculent material. The washing discharge collected by the liquid collection device was directly sent to the mother liquor storage tank without interstage countercurrent reuse. The washed filter cake was dehydrated again in the post-wash dehydration zone to obtain solid material and liquid phase.

[0069] Example 5 This embodiment provides a solid-liquid separation method and system for flocculated materials. The difference from Embodiment 1 is that the solid-liquid separation unit 1 is only equipped with a vacuum desliming device 11 and does not have a gravity settling device 12; the countercurrent displacement washing unit 2 is still equipped with a two-stage spray device 21 and a corresponding independent liquid collection device 22. The rest of the system structure is the same as that of Embodiment 1, and the continuous feed processing capacity is 100 kg / h.

[0070] The solid-liquid separation method includes: The flocculent material obtained in Preparation Example 1 was fed directly into a sealed vacuum dehydration device at a continuous feed rate of 100 kg / h without gravity settling. (The vacuum degree in the vacuum dehydration zone and the post-wash dehydration zone was 0.05 MPa, the conveyor filter belt was a 200-mesh conductive filter cloth and grounded, the conveyor filter belt travel speed was 2 m / min, the material residence time in the vacuum dehydration zone, the washing zone, and the post-wash dehydration zone was 2 min, 3 min, and 2 min, respectively, and the gas phase space of the sealed cover was connected to an inert gas protection unit for closed-loop circulation.) Vacuum dehydration was performed in the vacuum dehydration zone. The dehydrated filter cake was washed using the two-stage countercurrent displacement method of Example 1, with the circulating washing liquid volume being 1 times the mass of the solid phase in the flocculent material. The washed filter cake was dehydrated again in the post-wash dehydration zone to obtain solid material and liquid phase.

[0071] Comparative Example 1 This comparative example provides a solid-liquid separation method for flocculated materials. 20 kg of each batch of flocculated material obtained in Preparation Example 1 is fed into a high-speed centrifuge at 4000 rpm for open-top centrifugation for 10 min to obtain solid material and liquid phase.

[0072] Comparative Example 2 This comparative example provides a solid-liquid separation method for flocculated materials. The flocculated material obtained in Preparation Example 1 is fed into a sealed vacuum dehydration device at a continuous feed rate of 100 kg / h (the vacuum degree in the vacuum dehydration zone and the post-wash dehydration zone is 0.05 MPa, the conveyor filter belt is a 200-mesh conductive filter cloth and grounded, the conveyor filter belt travel speed is 2 m / min, the material residence time in both the vacuum dehydration zone and the post-wash dehydration zone is 2 min, and the gas phase space of the sealed cover is connected to an inert gas protection unit for closed-loop circulation) for vacuum dehydration without spray replacement washing, to obtain solid material and liquid phase.

[0073] Comparative Example 3 This comparative example provides a solid-liquid separation method for flocculent materials. The flocculent material with an average particle size of approximately 0.3 mm obtained in Preparation Example 3 was first tested under the vacuum dewatering conditions of Example 1. Because the fine flocs were difficult to stably form a filter cake and exhibited significant filter penetration, continuous vacuum belt dewatering could not be maintained. Therefore, the same 4000 rpm high-speed centrifugation operation as in Comparative Example 1 was adopted. Specifically, 20 kg of wet flocculent material was centrifuged for 10 min in each batch, and the mother liquor was discharged. Subsequently, a two-stage centrifugal replacement washing process was performed. In the first stage, the centrifuged supernatant obtained from the second stage washing of the previous batch was added to the centrifuged wet material, at a volume 0.5 times the mass of the solid phase in this batch. After low-speed stirring for 5 min, centrifugation was carried out at 4000 rpm for 10 min. In the second stage, the recovered washing liquid provided by the circulating liquid storage tank was added, at a volume 0.5 times the mass of the solid phase in this batch. After low-speed stirring for 5 min, centrifugation was carried out again at 4000 rpm for 10 min. The supernatant obtained in the second stage was reserved as the first-stage washing liquid for the next batch, and the supernatant obtained in the first stage was incorporated into the mother liquor recovery system. After completing no fewer than three consecutive batches and achieving stable performance of the washing solution, samples were taken for performance testing.

[0074] Test methods (1) Floc particle size (mm): The floc material obtained in the preparation example was subjected to low-amplitude wet sieving using a standard test sieve group. The sieve aperture sizes were 0.25 mm, 0.5 mm, 1.0 mm, 2.0 mm, 3.15 mm, 4.0 mm and 5.0 mm respectively. After sieving for 3 min, the mass of each particle size was weighed, and the average particle size of the floc was calculated by mass weighting according to the representative particle size of each particle size. (2) Solid liquid content (%): Weigh the separated solid sample and record it as M0. Place it in a vacuum drying oven and dry it to constant weight at 70±2℃ and gauge pressure not higher than -0.08 MPa to obtain dry basis mass M1. The solid liquid content is calculated as (M0-M1) / M0×100%. (3) Fine powder entrainment rate (%): The liquid phase after separation is tested by liquid phase filtration weighing method. The liquid phase material is filtered and then dried to constant weight under vacuum at 70±2℃. The mass of fine powder entrained in the liquid phase is obtained after deducting the mass of the blank filter membrane and is converted according to the total amount of liquid phase. The fine powder entrainment rate is expressed as the percentage of the mass of fine powder entrained in the liquid phase to the mass of the corresponding solid phase in the feed. (4) Solvent recovery rate (%): The liquid phase components of the system are summarized, and cyclohexane and ethanol are quantified using a gas chromatograph with a flame ionization detector; the solvent recovery rate is calculated as the ratio of the total mass of net recovered and recyclable cyclohexane and ethanol during the stable operation cycle to the total mass of cyclohexane and ethanol input in the feed during the same period, and the result is expressed as a percentage; the interstage liquid used in multi-stage washing is not included in the recovery amount repeatedly; (5) On-site safety performance: Examples 1-5 and Comparative Example 2 use the online monitoring device 42 of combustible gas concentration in the safety interlock unit 4 to continuously monitor the combustible gas concentration inside the equipment and key emission points, and record it in %LEL (lower explosive limit percentage); Comparative Example 1 and Comparative Example 3 did not use the safety interlock unit of the present invention, and used an independent online LEL detector with the same range to conduct comparative monitoring around the centrifuge.

[0075] The test results are shown in Table 1: Table 1 The test results show that: (1) As can be seen from Examples 1 to 5, when solid-liquid separation is carried out under the solid-liquid separation method and solid-liquid separation system of the flocculated material provided by the present invention, the solid phase liquid content is 45-55%, the fine powder entrainment rate is not higher than 0.5%, the solvent recovery rate is above 96.5%, and the on-site combustible gas concentration is stable below 10% LEL. At the same time, the solid-liquid separation effect and operational safety are guaranteed, and the connection requirements for subsequent direct docking extrusion dehydration are met.

[0076] (2) According to Examples 1 and 4, under the same conditions of feed, vacuum degree, filter belt speed, residence time in each zone and amount of circulating washing liquid, after using two-stage countercurrent replacement washing in Example 1, the solid liquid content decreased from 53% in Example 4 to 48%, and the solvent recovery rate increased from 96.5% to 97.2%. This shows that graded collection and countercurrent application of washing liquid can improve the utilization efficiency of washing liquid and the replacement effect of mother liquor.

[0077] (3) According to Examples 1 and 5, under the same operating parameters, after setting a 15-minute gravity sedimentation pretreatment before vacuum dehydration in Example 1, the solid liquid content decreased from 55% to 48%, the fine powder entrainment rate decreased from 0.5% to 0.3%, and the solvent recovery rate increased from 96.7% to 97.2%. This shows that gravity sedimentation can remove some free liquid in advance and reduce the load of subsequent vacuum dehydration, which is beneficial to reduce the loss of fine powder with the liquid phase and improve the overall separation stability.

[0078] (4) Comparative Example 1 uses high-speed centrifugation. Although the liquid content in the solid phase is the lowest, the problem of easy floc breakage during solid-liquid separation leads to the fine powder entrainment rate rising to 2.8%. Furthermore, the open operation causes the solvent to evaporate, resulting in an alarm for excessive concentration of combustible gas on site. Therefore, the high-speed centrifugation process not only reduces the quality of solid-liquid separation but also poses significant safety risks.

[0079] (5) In Comparative Example 2, without countercurrent displacement washing, the solid phase after separation contained more mother liquor and the solvent recovery rate dropped to 92.3%. This demonstrates the important role of countercurrent displacement washing in achieving closed-loop solvent circulation.

[0080] (6) The average particle size of the flocculant used in Comparative Example 3 was only 0.3 mm. Under the vacuum belt dewatering conditions of Example 1, it was difficult to stably form a filter cake and obvious filter penetration occurred. Therefore, it was necessary to return to high-speed centrifugation at 4000 rpm and match it with two-stage centrifugal displacement washing. Although the solid liquid content could be reduced to 43% after centrifugation, the fine powder entrainment rate was still as high as 3.5%, and the risk of ignition was reintroduced into the high-speed rotating equipment. This result shows that when the average particle size of the flocs is less than 0.5 mm, the continuous and safe separation route of this invention, which is based on low mechanical energy vacuum dewatering, is difficult to implement stably. Therefore, it is supported to regard 0.5~5 mm as the preferred floc particle size window.

[0081] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A solid-liquid separation system for flocculated materials, characterized in that, The solid-liquid separation system includes a solid-liquid separation unit (1), a countercurrent displacement washing unit (2), an inert gas protection unit (3), a safety interlock unit (4), and a liquid phase recovery unit (5). The solid-liquid separation unit (1) includes a closed vacuum desliming device (11). The vacuum dehydration device (11) includes a vacuum dehydration zone, a washing zone and a post-wash dehydration zone along the material travel direction; The countercurrent displacement washing unit (2) includes a spray device (21) and a liquid collection device (22). The spraying device (21) is located above the washing area and is used to spray washing liquid onto the filter cake below; The liquid collection device (22) is located below the vacuum desolution zone, the washing zone and the post-wash desolution zone, and is used to receive the circulating washing liquid after passing through the filter cake and the liquid phase generated after vacuum desolution. The inert gas protection unit (3) is connected to the solid-liquid separation unit (1) to form a closed loop, providing an inert gas protection atmosphere for the solid-liquid separation unit; The safety interlock unit (4) is electrically connected to the solid-liquid separation unit (1); The liquid phase recovery unit (5) is connected to the countercurrent displacement washing unit (2).

2. The solid-liquid separation system according to claim 1, characterized in that, The solid-liquid separation unit (1) also includes a closed gravity settling device (12) located upstream of the vacuum dehydration device (11) and connected to the vacuum dehydration device (11). Preferably, the gas phase space in the sealed vacuum dehydration device (11) is connected to the inert gas protection unit (3); Preferably, the sealed gravity settling device (12) is a full liquid sealed structure with no gas phase space inside, or the gas phase space is connected to the inert gas protection unit (3). Preferably, the sealed vacuum desiccant device (11) includes a sealing cover (1101), a conveyor filter belt (1102), and a vacuum chamber (1103). Preferably, the conveyor filter belt (1102) passes through the inside of the sealing cover (1101), and the vacuum box (1103) is disposed on the lower side of the conveyor filter belt (1102), corresponding to the vacuum desliming zone and the post-wash desliming zone respectively; Preferably, the conveyor filter belt (1102) is a conductive filter cloth, which is grounded to release the charge accumulated on the filter belt, and the grounding resistance is ≤10 Ω; Preferably, the inert gas protection unit (3) includes a circulating fan (31), a condenser (32) and a solvent collection tank (33) connected in sequence. The gas phase outlet of the condenser (32) is connected to the inlet of the circulating fan (31), the outlet of the circulating fan (31) is connected to the inert gas interface of the solid-liquid separation unit (1), and the liquid phase outlet of the condenser (32) is connected to the solvent collection tank (33). Preferably, when the solid-liquid separation unit (1) is a vacuum dehydration device (11), its inert gas interface and steam outlet are set on the sealing cover (1101), the inert gas interface is connected to the outlet of the circulating fan (31), and the steam outlet is connected to the inlet of the condenser (32). Preferably, when the solid-liquid separation unit (1) is a combination of a gravity settling device (12) and a vacuum desliming device (11), its inert gas interface and steam outlet are provided on the sealing cover (1101), the inert gas interface is connected to the outlet of the circulating fan (31), and the steam outlet is connected to the inlet of the condenser (32); when the gravity settling device (12) has a gas phase space, the gas phase space of the gravity settling device (12) is provided with an inert gas interface and a steam outlet; the inert gas interface of the gravity settling device (12) is connected to the outlet of the circulating fan (31), and the steam outlet of the gravity settling device (12) is connected to the inlet of the condenser (32); Preferably, the solid-liquid separation system is further provided with a connection sealing device (6); Preferably, the sealing device (6) at the connection point is located at the rotating connection point of the solid-liquid separation system that passes through the sealed boundary of each device, including the position where the shaft of the drive roller and / or the redirecting roller of the conveying filter belt (1102) extends through the sealing cover (1101), and the position where the shaft of the circulating fan (31) connects to the housing. Preferably, the connection sealing device (6) includes any one or a combination of at least two of the following: a labyrinth seal, a mechanical seal, or a nitrogen seal.

3. The solid-liquid separation system according to claim 1 or 2, characterized in that, The spraying device (21) can be configured as a multi-stage structure. Each spraying device is arranged in sequence along the filter cake transport direction in the vacuum desliming device. Each spraying device is equipped with an independent liquid collection device (22) below it. The last spraying device along the filter cake travel direction is connected to the circulating washing liquid outlet of the liquid recovery unit (5). The outlet of the next liquid collection device is connected to the inlet of the previous spraying device. The first liquid collection device is connected to the inlet of the liquid recovery unit (5). This allows the washing liquid to be applied in the opposite direction to the filter cake travel direction, thereby achieving multi-stage countercurrent replacement washing. Preferably, the liquid phase recovery unit (5) includes a mother liquor storage tank (51), a distillation recovery system (52) and a circulating liquid storage tank (53) connected in sequence. Preferably, when the countercurrent displacement washing unit (2) has a single-stage structure, the liquid collection device (22) of the vacuum dehydration zone is connected to the mother liquor storage tank (51). Preferably, when the countercurrent displacement washing unit (2) has a multi-stage structure, the first-stage liquid collection device along the filter cake traveling direction in the multi-stage structure is connected to the mother liquor storage tank (51). Preferably, when the countercurrent displacement washing unit (2) has a single-stage structure, the circulating liquid storage tank (53) is connected to the spray device (21). Preferably, when the countercurrent displacement washing unit (2) has a multi-stage structure, the circulating liquid storage tank (53) is connected to the last stage spray device in the multi-stage spray structure along the filter cake traveling direction; Preferably, the number of stages of the spraying device is set to 2-4 stages.

4. The solid-liquid separation system according to any one of claims 1-3, characterized in that, The safety interlocking unit (4) includes an online oxygen content monitoring device (41), an online combustible gas concentration monitoring device (42), and an interlocking control module (43).

5. A method for solid-liquid separation of flocculated materials, characterized in that, The solid-liquid separation method for flocculated materials is performed using the solid-liquid separation system for flocculated materials as described in any one of claims 1-4, wherein the solid-liquid separation method includes: The flocculated material is subjected to solid-liquid separation, washing, and post-washing dehydration under a closed environment and inert gas protection to obtain solid material and liquid phase; the average particle size of the flocs in the flocculated material is 0.5~5 mm.

6. The solid-liquid separation method according to claim 5, characterized in that, The flocculated material is a flocculent material obtained by ultrasonic flocculation of a solvent-based composite liquid. Preferably, the average particle size of the flocs is 1~4 mm; Preferably, the inert gas includes nitrogen.

7. The solid-liquid separation method according to claim 6, characterized in that, The solid-liquid separation includes vacuum dehydration; Preferably, the solid-liquid separation further includes gravity sedimentation before vacuum dehydration; Preferably, the residence time of the material under gravity settling is 5 to 30 minutes; Preferably, the vacuum degree of the vacuum dehydration is 0.02~0.08 MPa; Preferably, the filter medium used for vacuum dehydration has a mesh size of 100-400 mesh; Preferably, during the vacuum dehydration process, the material travels at a speed of 0.5 to 5 m / min along the conveyor belt; Preferably, the vacuum degree of the post-washing desolvation is 0.02~0.08 MPa; Preferably, the material residence time during vacuum dehydration is 1-5 min, the material residence time during washing is 1-10 min, and the material residence time after washing and dehydration is 1-5 min.

8. The solid-liquid separation method according to any one of claims 5-7, characterized in that, The circulating washing liquid used in the washing process is obtained by distillation and recovery of the liquid phase produced during the solid-liquid separation process.

9. The solid-liquid separation method according to claim 8, characterized in that, The total amount of the circulating washing liquid is calculated based on the circulating washing liquid entering the washing zone from the liquid phase recovery unit, and its mass ratio to the solid phase mass in the flocculant is (0.3~2):

1.

10. The solid-liquid separation method according to any one of claims 5-9, characterized in that, The liquid content of the solid material is 40-60%.

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