Drying system and method for vinylidene fluoride polymer

Abstract

The invention belongs to the technical field of drying processes, and particularly relates to a drying system and method for vinylidene fluoride polymer, the drying system is used for drying PVDF wet materials, and the drying system comprises an air blower, a heat exchanger, a flash tower, a cyclone dryer, a bag type dust collector, an induced draft fan and a control unit; the bottom of the flash tower is connected to the downstream of the heat exchanger, the middle is connected to the downstream of the wet material bin, and the top is connected to the upstream of the cyclone dryer; the blower is connected to the upstream of the heat exchanger; the bag type dust collector is connected to the downstream of the cyclone dryer, and the induced draft fan is connected to the downstream of the bag type dust collector; and the wet material bin is connected with the flash tower through a screw conveyor. Compared with the prior art, the problems that in the prior art, when the PVDF wet material is dried, the PVDF wet material is prone to being unevenly heated and agglomerated or excessively heated and melted into sand-shaped hard particles or product volatile components are high are solved. According to the scheme, on the premise that the water content reaches the standard, the continuous feeding function is achieved, and the generation of sand-shaped hard particles melted can be effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of drying processes, and particularly relates to a drying system and method for polyvinylidene fluoride polymers. Background Art

[0002] Polyvinylidene fluoride (abbreviation: PVDF) resin mainly refers to a homopolymer of vinylidene fluoride (VDF) or a copolymer of vinylidene fluoride and a small amount of other fluorinated vinyl monomers. Polyvinylidene fluoride resin combines the characteristics of fluororesins and general-purpose resins. In addition to having good chemical corrosion resistance, high temperature resistance, oxidation resistance, weather resistance, and radiation resistance, it also has special properties such as piezoelectricity, dielectricity, and pyroelectricity. It is currently the second-largest product in terms of production volume among fluoroplastics and can be used as materials such as lithium battery binders, solar backsheet films, lithium battery separator coatings, building material films, water treatment membranes, coatings, corrosion-resistant chemical valves and pipelines, etc. It is an environmentally friendly and new energy fluorine-containing new material.

[0003] PVDF mainly enters downstream applications in powder form. Generally, its production process needs to go through the process of emulsion (or suspension) - demulsified material - washed wet material - powder finished product. In the step of drying the washed wet material to powder, if not controlled well, it will cause uneven heating and agglomeration, or overheating to reach the melting range of PVDF, resulting in melting into sand-like hard particles, or high volatile content of the product, directly affecting the application performance of the product and even causing the VOC of the manufactured product to exceed the standard, exceeding the product regulatory requirements.

[0004] In the prior art, such as:

[0005] (1) CN 104448077 B "Production process of polyvinylidene fluoride" mentions filtration, washing, and drying to obtain powdered polyvinylidene fluoride. However, no detailed drying method is given, and using a general drying method is likely to cause problems such as uneven heating, overheating and melting, and high volatile content;

[0006] (2) CN 115875940 A "A continuous drying system for PVDF slurry", such as Figure 1 . The heating temperature range of the heater is 100°C to 200°C, and some of it exceeds the melting point and initial melting temperature of PVDF (generally 135 - 175°C, see Figure 2 ). At the same time, the outlet temperature of its filter reaches 70°C to 130°C. After primary drying, when the semi-finished material flows from the first bag filter to the second bag filter, it is secondarily dried at this temperature. At this time, most of the surface moisture of the material has been dried, and it directly contacts the 70°C to 130°C, which has reached the initial melting temperature of PVDF (see Figure 2 ).

[0007] The above two factors will cause the PVDF powder to be overheated, resulting in partial melting of some powders. The material will be in the form of hard sand grains, affecting the application performance of the product.

[0008] (3) CN 108484814 B "A hydrophilic polyvinylidene fluoride resin". Its post-treatment method is centrifugal dehydration. The dehydrated resin is placed in an oven at 85°C and baked for 24 hours. This method has a long drying time, and the dried material agglomerates severely, which is not conducive to subsequent applications. It cannot reach the particle size level required for lithium battery applications, resulting in difficult dispersion or even gelation phenomena in subsequent applications. Moreover, agglomeration is likely to cause the VOC in the material drying process to volatilize poorly, resulting in the VOC of the subsequent products exceeding the standard and exceeding the product regulations.

[0009] Therefore, it is necessary to propose a drying system and method suitable for polyvinylidene fluoride polymers. Summary of the Invention

[0010] The purpose of the present invention is to provide a drying system and method for polyvinylidene fluoride polymers to solve at least one of the above problems, so as to solve the problems of uneven heating and agglomeration, excessive heating and melting into hard sand-like particles, or high volatile content of the product during the drying of PVDF wet materials in the prior art. On the premise that the moisture content meets the standard, this solution meets the continuous feeding function, can effectively reduce the generation of hard sand-like particles melted, make the product particle size within the range of lithium battery binder applications, improve the dispersion effect, and reduce the gelation phenomenon and VOC exceeding the standard phenomenon during the application process.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] The first aspect of the present invention discloses a drying system for polyvinylidene fluoride polymers, which is used for drying PVDF wet materials, and includes a blower, a heat exchanger, a flash tower, a cyclone dryer, a bag filter, an induced draft fan, and a control unit;

[0013] The bottom of the flash tower is connected to the downstream of the heat exchanger, the middle of the flash tower is connected to the downstream of the wet material bin, and the top of the flash tower is connected to the upstream of the cyclone dryer; the blower is connected to the upstream of the heat exchanger; the bag filter is connected to the downstream of the cyclone dryer, and the induced draft fan is connected to the downstream of the bag filter;

[0014] An inlet air temperature sensor is arranged inside the connecting pipeline between the flash tower and the heat exchanger, a mixing temperature sensor is arranged inside the flash tower, and a heat flow regulating valve is arranged on the heat flow pipeline of the heat exchanger; the wet material bin is connected to the flash tower through a screw conveyor;

[0015] The control unit is electrically connected to the inlet air temperature sensor, the mixing temperature sensor, the heat flow regulating valve, and the screw conveyor respectively.

[0016] Preferably, a stirring device is arranged at the bottom inside the flash evaporation tower.

[0017] Preferably, the stirring speed of the stirring device is 200 - 500 r / min.

[0018] Preferably, a blanking port is arranged at the bottom of the cyclone dryer.

[0019] Preferably, a number of cyclone dryers are arranged in series and / or in parallel between the flash evaporation tower and the bag filter.

[0020] Preferably, the bag filter is a pulse bag filter, and a induced draft fan is arranged at the bottom of the bag filter.

[0021] Preferably, a chimney is connected downstream of the induced draft fan.

[0022] Preferably, an activated carbon adsorption device and / or a water scrubber are connected downstream of the chimney.

[0023] Preferably, the control unit is a PLC controller, and through feedback control, it realizes: adjusting the opening degree of the heat flow regulating valve according to the inlet air temperature obtained by the inlet air temperature sensor, and adjusting the rotation speed of the screw conveyor according to the mixing temperature obtained by the mixing temperature sensor.

[0024] In the second aspect of the present invention, a method for drying a vinylidene fluoride polymer is disclosed, which is implemented by using any one of the drying systems described above;

[0025] The method includes the following steps:

[0026] S1: Store the PVDF wet material inside the wet material bin;

[0027] S2: Turn on the blower, and then turn on the induced draft fan to make the system in a negative pressure state;

[0028] S3: Open the heat flow regulating valve and control the inlet air temperature entering the flash evaporation tower through the heat exchanger;

[0029] S4: Open the screw conveyor to start feeding the PVDF wet material, and control the mixing temperature inside the flash evaporation tower by adjusting the rotation speed of the screw conveyor;

[0030] S5: Continuously feed and discharge to complete the continuous drying of PVDF.

[0031] Preferably, the negative pressure state is -0.5 to -2 kPa, the inlet air temperature is 80 to 130 °C, and the mixing temperature is 60 to 100 °C.

[0032] The working principle of the present invention is:

[0033] The blower filters and introduces the outside air, which is heated to the required inlet air temperature (detected by the inlet air temperature sensor) through the heat exchanger and then enters the flash tower;

[0034] In the middle and lower part of the flash tower, it combines with the PVDF wet material spirally coming in from the wet silo, and a mixed temperature (detected by the mixed temperature sensor) will be formed here;

[0035] The evaporated water continues to rise with the hot air and enters the cyclone dryer. Larger and heavier materials flow out through the discharge port, and lighter materials flow with the air current to the bag filter. The separation of gas and powder is achieved through the interception of the cloth bag. The humid and hot gas is drawn by the induced draft fan and discharged through the chimney.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention provides a method for drying highly efficient and highly dispersed polyvinylidene fluoride (PVDF). Through the flash tower, the combination of the inlet air temperature and the heat flow regulating valve and the interlock of the mixed temperature and the wet material feeding, the appropriate inlet air temperature, mixed temperature and system negative pressure are controlled. On the premise that the moisture content meets the standard, the continuous feeding function is satisfied, the generation of molten sand-like hard particles can be effectively reduced, the product particle size is within the range applicable to lithium battery binders, the dispersion effect is improved, and the gel phenomenon and VOC exceeding the standard phenomenon during the application process are reduced.

[0038] (1) Automation:

[0039] ① Interlock the heat flow regulating valve with the inlet air temperature sensor. Only by inputting the inlet air temperature, the heat flow regulating valve can be automatically controlled to the required temperature;

[0040] ② Interlock the frequency of the feeding screw conveyor with the mixed temperature sensor. Only by inputting the mixed temperature, the feeding frequency can be automatically adjusted.

[0041] (2) For the particle size Dv50 of the product applied to lithium battery binders, it is required to be controlled <50um, and the control range is relatively wide. The discharge port can be closed, and all the materials can be mixed and discharged through the rotary air lock valve, so that the product particle size is uniform and there is no need for further refinement and classification; if there is a requirement for refined particle size, one or more cyclone separators can also be set up to achieve refined particle size classification.

[0042] (3) Environmental protection: An activated carbon adsorption device and a water washing tower can be added behind the chimney to further reduce the tail gas VOC. Description of the Drawings

[0043] Figure 1 It is a process flow schematic diagram of the prior art (CN 115875940 A);

[0044] Figure 2Schematic diagram of the melting point of PVDF resin (used as a conventional lithium battery binder).

[0045] Figure 3 Schematic structural diagram of the drying system for the polyvinylidene fluoride polymer of the present invention.

[0046] Figure 4 Schematic flow diagram of the drying method for the polyvinylidene fluoride polymer of the present invention.

[0047] In the figure: 1 - blower; 2 - heat exchanger; 3 - flash tower; 4 - stirring device; 5 - wet material bin; 6 - cyclone dryer; 7 - bag filter; 8 - chimney; 9 - control unit; 10 - inlet air temperature sensor; 11 - induced draft fan; 12 - screw conveyor; 21 - heat flow regulating valve; 31 - mixing temperature sensor; B1 - discharge opening; B2 - air lock. Detailed implementation mode

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] In the following description, unless otherwise specified, the reagents used may be conventional commercial products, and the methods used are well-known means in the art.

[0050] All matters not described below can adopt the prior art.

[0051] Prior art, CN 115875940 A "A continuous drying system for PVDF slurry", as Figure 1 shown, in which the heating temperature range of the heater is 100°C to 200°C, and part of it exceeds the melting point and initial melting temperature of PVDF (generally 135 - 175°C, see Figure 2 ), and at the same time, the outlet temperature of its filter reaches 70°C to 130°C. After primary drying, when the semi-finished material flows from the first bag filter to the second bag filter, it is secondarily dried by this temperature. At this time, most of the surface moisture of the material has been dried. When it contacts 70°C to 130°C again, it has reached the initial melting temperature of PVDF (see Figure 2 ). Therefore, the solution of the prior art will cause the PVDF powder to be overheated, resulting in partial melting of the powder, and the material being in a hard sand-like state, affecting the application performance of the product.

[0052] In the solution of the present invention:

[0053] A drying system for polyvinylidene fluoride polymer, as Figure 3 shown, for drying PVDF wet material, including a blower 1, a heat exchanger 2, a flash tower 3, a cyclone dryer 6, a bag filter 7, an induced draft fan, and a control unit 9;

[0054] The bottom of the flash evaporation tower 3 is connected to the downstream of the heat exchanger 2, the middle part of the flash evaporation tower 3 is connected to the downstream of the wet material bin 5, and the top of the flash evaporation tower 3 is connected to the upstream of the cyclone dryer 6; the blower 1 is connected to the upstream of the heat exchanger 2; the bag filter 7 is connected to the downstream of the cyclone dryer 6, and the induced draft fan is connected to the downstream of the bag filter 7;

[0055] An air inlet temperature sensor 10 is arranged inside the connecting pipeline between the flash evaporation tower 3 and the heat exchanger 2, a mixing temperature sensor 31 is arranged inside the flash evaporation tower 3, and a heat flow regulating valve 21 is arranged on the heat flow pipeline of the heat exchanger 2; the wet material bin 5 is connected to the flash evaporation tower 3 through a screw conveyor 12;

[0056] The control unit 9 is electrically connected to the air inlet temperature sensor 10, the mixing temperature sensor 31, the heat flow regulating valve 21 and the screw conveyor 12 respectively.

[0057] Wherein:

[0058] The PVDF wet material is the wet material after the polymerized PVDF emulsion or suspension is washed and pressed by a plate and frame filter press, and it is necessary to use a plate and frame filter press to press and control the moisture below 20% in the front-end process;

[0059] The heat exchanger 2 can be of any suitable structure, and the heat flow of the heat exchanger 2 adopts a steam flow;

[0060] The process parameters of the flash evaporation tower 3 can be determined according to the process of conventional PVDF drying; a stirring device 4 is arranged at the bottom inside the flash evaporation tower 3, and the stirring speed is 200 - 500 r / min; the stirring device 4 can adopt a combination of a stirring paddle and a motor, and is equipped with an encoder to detect the rotation speed, and this encoder is electrically connected to the control unit 9 to obtain and monitor the rotation speed of the stirring paddle in real time;

[0061] A discharge port B1 is arranged at the bottom of the cyclone dryer 6, and a rotary air lock B2 is arranged at the bottom of the bag filter 7;

[0062] Several cyclone dryers 6 can be arranged in series and / or in parallel between the flash evaporation tower 3 and the bag filter 7;

[0063] The bag filter 7 is a pulse bag filter;

[0064] The downstream of the induced draft fan is connected to a chimney 8;

[0065] The downstream of the chimney 8 is connected to an activated carbon adsorption device and / or a water washing tower;

[0066] The blower 1, the heat exchanger 2, the flash evaporation tower 3, the cyclone dryer 6, the bag filter 7 and the chimney 8 are connected to each other through a conveying pipeline;

[0067] Both the inlet air temperature sensor 10 and the mixing temperature sensor 31 adopt thermometers;

[0068] The heat flow regulating valve 21 can adopt a solenoid valve;

[0069] The control unit 9 is a PLC controller, and through feedback control, it realizes: adjusting the opening degree of the heat flow regulating valve 21 according to the inlet air temperature obtained by the inlet air temperature sensor 10, and adjusting the rotation speed of the screw conveyor 12 according to the mixing temperature obtained by the mixing temperature sensor 31 (that is, the inlet air temperature sensor 10 is interlocked with the heat flow regulating valve 21, and the mixing temperature sensor 31 is interlocked with the screw conveyor 12).

[0070] A drying method for polyvinylidene fluoride polymer, as Figure 4 shown, is implemented by using the drying system described above;

[0071] The described method includes the following steps:

[0072] S1: Store the PVDF wet material inside the wet material bin 5;

[0073] S2: Turn on the blower 1, and then turn on the induced draft fan to make the system in a negative pressure state;

[0074] S3: Open the heat flow regulating valve 21 and control the inlet air temperature entering the flash evaporation tower 3 through the heat exchanger 2;

[0075] S4: Open the screw conveyor 12 to start feeding the PVDF wet material, and control the mixing temperature inside the flash evaporation tower 3 by adjusting the rotation speed of the screw conveyor 12;

[0076] S5: Turn on the pulse of the bag filter 7 and the discharge port B1 and the air lock B2;

[0077] S6: Continuously feed and discharge to complete the continuous drying of PVDF.

[0078] Among them:

[0079] The negative pressure state is -0.5 to -2 kPa, the inlet air temperature is 80 to 130 °C, and the mixing temperature is 60 to 100 °C;

[0080] When the blower 1 and the induced draft fan are turned on, to ensure the safety of the system, turn on the blower 1 first and then the induced draft fan, with an interval of 5 to 10 seconds; when turning off, turn off the induced draft fan first, and then turn off the blower 1, with an interval of 10 to 15 seconds.

[0081] The blower 1 filters and introduces the outside air, exchanges heat through the heat exchanger 2 to the required inlet air temperature (detected by the inlet air temperature sensor 10) and enters the flash evaporation tower 3;

[0082] At the bottom of the flash evaporation tower 3, there is a stirring device 4, which forms a cyclone by stirring the incoming air and combines with the PVDF wet material spirally entering from the wet material bin 5 in the lower part of the tower. Here, a mixing temperature (detected by the mixing temperature sensor 31) will be formed.

[0083] The evaporated water continues to rise with the hot air and enters the cyclone dryer 6. The materials with larger particle size and heavier weight flow out through the discharge port B1, and the materials with lighter particle size flow with the air flow to the bag filter 7. The separation of gas and powder is achieved through the interception of the cloth bag. The humid and hot gas is drawn by the induced draft fan and discharged through the chimney 8.

[0084] Example 1

[0085] S1: The wet material after washing and pressing the polymerized PVDF emulsion or suspension by the plate and frame filter press is stored inside the wet material bin 5 for treatment.

[0086] S2: Turn on the blower 1, and then turn on the induced draft fan to control the system negative pressure at -1.0 kPa. Open the bottom stirring device 4 of the flash evaporation tower 3 and control the stirring speed at 500 r / min.

[0087] S3: Open the heat flow regulating valve 21 and control the incoming air temperature at 130 °C.

[0088] S4: Open the feed screw conveyor 12 and send the wet PVDF material into the flash evaporation tower 3 through the screw, and control the mixing temperature at 100 °C.

[0089] S5: Turn on the pulse of the bag filter 7, as well as the discharge port B1 and the air lock B2.

[0090] S6: Continuously feed and discharge materials.

[0091] Example 2

[0092] S1: The wet material after washing and pressing the polymerized PVDF emulsion or suspension by the plate and frame filter press is stored inside the wet material bin 5 for treatment.

[0093] S2: Turn on the blower 1, and then turn on the induced draft fan to control the system negative pressure at -0.5 kPa. Open the bottom stirring device 4 of the flash evaporation tower 3 and control the stirring speed at 200 r / min.

[0094] S3: Open the heat flow regulating valve 21 and control the incoming air temperature at 80 °C.

[0095] S4: Open the feed screw conveyor 12 and send the wet PVDF material into the flash evaporation tower 3 through the screw, and control the mixing temperature at 60 °C.

[0096] S5: Turn on the pulse of the bag filter 7, as well as the discharge port B1 and the air lock B2.

[0097] S6: Continuous feeding and discharging.

[0098] Example 3

[0099] S1: The wet material after the washed and pressed PVDF emulsion or suspension after polymerization is stored inside the wet material bin 5 for treatment.

[0100] S2: Turn on the blower 1, then turn on the induced draft fan to control the system negative pressure at -1.0 kPa. Open the bottom stirring device 4 of the flash tower 3 and control the stirring speed at 350 r / min.

[0101] S3: Open the heat flow regulating valve 21 and control the inlet air temperature at 100 °C.

[0102] S4: Open the feeding screw conveyor 12, and feed the wet PVDF material into the flash tower 3 through the screw, and control the mixing temperature at 85 °C.

[0103] S5: Turn on the pulse of the bag filter 7, as well as the discharge port B1 and the air lock B2.

[0104] S6: Continuous feeding and discharging.

[0105] Example 4

[0106] S1: The wet material after the washed and pressed PVDF emulsion or suspension after polymerization is stored inside the wet material bin 5 for treatment.

[0107] S2: Turn on the blower 1, then turn on the induced draft fan to control the system negative pressure at -1.0 kPa. Open the bottom stirring device 4 of the flash tower 3 and control the stirring speed at 500 r / min.

[0108] S3: Open the heat flow regulating valve 21 and control the inlet air temperature at 100 °C.

[0109] S4: Open the feeding screw conveyor 12, and feed the wet PVDF material into the flash tower 3 through the screw, and control the mixing temperature at 85 °C.

[0110] S5: Turn on the pulse of the bag filter 7, as well as the discharge port B1 and the air lock B2.

[0111] S6: Continuous feeding and discharging.

[0112] Comparative Example 1

[0113] Simulate the PVDF drying conditions of the CN 108484814 B patent, and the experimental conditions are as follows:

[0114] Take out the wet material after the washed and pressed PVDF emulsion or suspension after polymerization, put it into an oven at 85 °C, and dry it for 24 h.

[0115] Comparative Example 2

[0116] Simulate the secondary drying of the patent CN 115875940 A, and the experimental conditions are as follows:

[0117] After taking out the dried material of Example 2, place it in the wet material bin 5 again, and then use an inlet air temperature of 120 °C (the other conditions are: the system negative pressure is controlled at -1.0 kPa, the stirring is turned on, and the stirring speed is controlled at 350 r / min) for re-drying.

[0118] Comparative Example 3

[0119] S1: The wet material after washing and pressing the polymerized PVDF emulsion or suspension by a plate and frame filter press is stored inside the wet material bin 5 for treatment;

[0120] S2: Turn on the blower 1, and then turn on the induced draft fan to control the system negative pressure at -1.0 kPa. Open the stirring device 4 and control the stirring speed at 500 r / min.

[0121] S3: Open the heat flow regulating valve 21 and control the inlet air temperature at 150 °C;

[0122] S4: Open the feed screw conveyor 12, and feed the wet PVDF material into the flash evaporation tower 3 through the screw, and control the mixing temperature at 120 °C;

[0123] S5: Turn on the pulse of the bag filter 7, as well as the discharge port B1 and the rotary air lock B2;

[0124] S6: Continuously feed and discharge.

[0125] Performance test:

[0126] The test methods involved in the specific implementation are as follows:

[0127] (1) Inlet air, outlet air temperature and system pressure tests are feedback by thermometers and pressure gauges.

[0128] (2) VOC test & moisture content test:

[0129] VOC test: Obtained by subtracting moisture from volatile matter;

[0130] Among them,

[0131] Volatile matter is tested by a halogen moisture analyzer at a test temperature of 105 °C, 10 g, and baked for 20 minutes;

[0132] Moisture is directly measured by Karl Fischer,

[0133] Subtracting the two gives the organic volatile matter VOC.

[0134] (3) Large particles:

[0135] ① Touch the powder by hand to see if there is a sandy hard particle feeling in the powder;

[0136] ② Weigh 5 g of the PVDF finished product, add 20 g of ethanol, then put it into an ultrasonic machine and ultrasonicate for 5 min. After the ultrasonication is completed, transfer it to a magnetic stirrer and stir at a speed of 500 rpm for 5 min;

[0137] ③ Finally, pour the stirred PVDF solution onto a 100-mesh nylon filter screen at one time, wash the beaker with anhydrous ethanol, and then pour the washed anhydrous ethanol onto the filter screen to observe whether there are hard particles that cannot be dispersed.

[0138] (4) Particle size test:

[0139] Weigh (0.07 - 0.09) g of PVDF powder with a 50 mL beaker, add (5 ± 0.01) g of anhydrous ethanol to the beaker, put in a stirring bar about 2.5 mm long and seal it with plastic wrap. Ultrasonicate in an ultrasonic machine for 5 min, transfer it to a magnetic stirrer and stir at a speed of 500 rpm for more than 20 min, and then drop the sample into a laser particle size analyzer to ensure that the light shielding rate is (8 - 12)% (the relevant instrument parameters are that the particle refractive index is set to 1.42, the dispersant is water, and the refractive index of the dispersant is 1.33).

[0140] (5) Processing time: Convert to the time required for single-ton processing.

[0141] Perform performance tests on the dried PVDF finished products of Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3 by the above method. The specific data are shown in Table 1 below:

[0142] Table 1 Performance test results of Examples 1 - 4 and Comparative Examples 1 - 3

[0143]

[0144] It can be concluded from the test results that Examples 1, 2, 3, and 4 can all meet the particle size, moisture content, and VOC requirements for lithium battery binder applications, and can be selected according to relevant indicators. Considering comprehensive energy conservation and efficiency, Example 3 is better.

[0145] In summary, the present invention provides a method for drying a highly efficient and highly dispersed polyvinylidene fluoride polymer (PVDF). Through the flash evaporation tower 3, the combination of the inlet air temperature and the heat flow regulating valve 21 and the mixing temperature and the feed interlock, the appropriate inlet air temperature, mixing temperature, and system negative pressure are controlled. On the premise that the moisture content meets the standard, the continuous feeding function is satisfied, the generation of molten sandy hard particles can be effectively reduced, the product particle size is within the range of lithium battery binder applications, the dispersion effect is improved, and the gel phenomenon and VOC exceeding the standard phenomenon during the application process are reduced.

[0146] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A drying system for vinylidene fluoride polymer, used for drying PVDF wet material, characterized in that: It comprises a blower (1), a heat exchanger (2), a flash tower (3), a cyclone dryer (6), a bag filter (7), an induced draft fan (11) and a control unit (9); The bottom of the flash tower (3) is connected to the downstream of the heat exchanger (2), the middle of the flash tower (3) is connected to the downstream of the wet material bin (5), and the top of the flash tower is connected to the upstream of the cyclone dryer (6); the blower (1) is connected to the upstream of the heat exchanger (2); the bag dust collector (7) is connected to the downstream of the cyclone dryer (6), and the induced draft fan (11) is connected to the downstream of the bag dust collector (7); An air inlet temperature sensor (10) is provided inside the connecting pipeline between the flash tower (3) and the heat exchanger (2), a mixing temperature sensor (31) is provided inside the flash tower (3), and a heat flow regulating valve (21) is provided on the heat flow pipeline of the heat exchanger (2); the wet material bin (5) is connected to the flash tower (3) via a screw conveyor (12); The control unit (9) is electrically connected to the air inlet temperature sensor (10), the mixing temperature sensor (31), the heat flow regulating valve (21) and the screw conveyor (12) respectively.

2. A drying system for vinylidene fluoride polymer according to claim 1, characterized in that: A stirring device (4) is arranged at the bottom of the flash tower (3).

3. A drying system for vinylidene fluoride polymer according to claim 1, characterized in that: The bottom of the cyclone dryer (6) is provided with a feed opening (B1).

4. A drying system for vinylidene fluoride polymer according to claim 1, characterized in that: A plurality of cyclone dryers (6) are arranged in series and / or in parallel between the flash tower (3) and the bag dust collector (7).

5. A drying system for vinylidene fluoride polymer according to claim 1, characterized in that: The bag dust collector (7) is a pulse bag dust collector, and a fan (B2) is arranged at the bottom of the bag dust collector (7).

6. A drying system for vinylidene fluoride polymer according to claim 1, characterized in that: The downstream of the induced draft fan (11) is connected to a chimney (8).

7. A drying system for vinylidene fluoride polymer according to claim 6, characterized in that: The downstream of the chimney (8) is connected to an activated carbon adsorption device and / or a water washing tower.

8. A drying system for vinylidene fluoride polymer according to claim 1, characterized in that: The control unit (9) is a PLC controller, which realizes through feedback control: adjusting the opening of the heat flow regulating valve (21) according to the inlet air temperature obtained by the inlet air temperature sensor (10), and adjusting the rotation speed of the screw conveyor (12) according to the mixed temperature obtained by the mixed temperature sensor (31).

9. A method for drying a vinylidene fluoride polymer, characterized in that: The method is implemented by using a drying system as described in any one of claims 1 to 8; The method comprises the following steps: S1: storing the PVDF wet material in the wet material bin (5); S2: Turn on the blower (1), and then turn on the induced draft fan (11), so that the system is in a negative pressure state; S3: Open the heat flow regulating valve (21) to control the inlet temperature of the air entering the flash tower (3) through the heat exchanger (2); S4: Open the screw conveyor (12) to start feeding the PVDF wet material, and control the mixing temperature in the flash tower (3) by adjusting the rotation speed of the screw conveyor (12); S5: Continuously feed and discharge materials to complete the continuous drying of PVDF.

10. The method for drying a vinylidene fluoride polymer according to claim 9, characterized in that: The negative pressure state is -0.5 to -2 kPa, the air inlet temperature is 80 to 130°C, and the mixing temperature is 60 to 100°C.

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