Method and system for washing vinylidene fluoride polymer

Abstract

The invention belongs to the technical field of polymer production, and particularly relates to a vinylidene fluoride polymer washing method and system, and the method comprises the following steps: S1, inputting a PVDF reaction mixed solution into a plate-and-frame filter press, and carrying out filter pressing; s2, crushing a PVDF filter cake obtained by filter pressing, adding a washing solution mixed with an organic dispersant, and stirring to form PVDF slurry; s3, the high-temperature washing liquid and the PVDF slurry are jointly input into a plate-and-frame filter press for filter pressing; s4, detecting the conductivity of the waste liquid generated by filter pressing in the step S3: if the measured conductivity is greater than a target value, returning to the step S2; if the measured conductivity is smaller than or equal to the target value, washing is completed. Compared with the prior art, the problems that in the prior art, washing of the PVDF polymer needs to consume a large amount of high-purity water and time, VOC exceeds the standard, and products become yellow at high temperature still exist are solved. According to the scheme, the method for washing the polymerized PVDF resin with high efficiency and low cost is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer production, and in particular relates to a washing method and system for vinylidene fluoride polymers. Background Art

[0002] Polyvinylidene fluoride (PVDF for short) has excellent chemical stability, thermal stability, mechanical stability, and weather resistance. It can be used as lithium battery binder, solar backplane film, lithium battery separator coating, building material film, water treatment membrane, coating, corrosion-resistant chemical valve pipeline and other materials. It is an environmentally friendly, new energy fluorine-containing new material.

[0003] Since the PVDF polymerization process requires the addition of some additives (such as emulsifiers / dispersants, initiators, chain transfer agents, etc.), if these additives are not removed during the production process, it will directly affect the product performance (such as product VOC exceeding the standard, product yellowing, and in serious cases, affecting battery safety performance). At present, the production process uses centrifuges or plate and frame filter presses and adds high-purity water for cleaning. The conductivity of the wastewater discharged from the washing is tested to confirm whether the washing is clean. Generally, it is required to be washed to a standard of ≤1μS / cm.

[0004] However, at present, centrifuges or plate and frame filter presses are used to wash the polymerized PVDF resin. Since the -CF- and -CH- bonds in the PVDF structure have strong hydrophobicity, the wettability of PVDF in contact with water molecules is poor and the hydrophobic effect is strong. In addition, as the washing proceeds, the dispersant or emulsifier on the surface of PVDF decreases, and PVDF will show stronger hydrophobicity, resulting in PVDF not being able to contact water well, causing the conductivity of the wastewater in the middle and late stages to drop very slowly, which in turn causes this process to consume a large amount of high-purity water and time. At present, under the washing method, the general high-purity water unit consumption (the water required to wash each ton of PVDF) can be as high as 50m 3 / ton, and the single batch processing time is as long as 8 hours; and there will be wrapping in the emulsion demulsification process after polymerization. If the washing process cannot be dispersed and unfolded, it will cause the subsequent product volatile organic matter (VOC) to exceed the standard and the product will turn yellow at high temperature.

[0005] Based on this, it is necessary to design a washing method suitable for PVDF polymers. Summary of the invention

[0006] The purpose of the present invention is to provide a method and system for washing vinylidene fluoride polymers in order to solve at least one of the above problems, so as to solve the problem that the washing of PVDF polymers in the prior art requires a large amount of high-purity water and time, and there is still the possibility of VOC exceeding the standard and yellowing of the product at high temperature. This scheme realizes an efficient and low-cost method for washing polymerized PVDF resin: the use of staged washing combined with the crushing process of PVDF and the addition of similar miscible organic dispersants can make PVDF better dispersed in the washing liquid and take away the organic matter added during the polymerization reaction, making the washing process more efficient and less costly, and the product has lower VOC residue and better high-temperature yellowing (product whiteness).

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The first aspect of the present invention discloses a method for washing a vinylidene fluoride polymer, comprising the following steps:

[0009] S1: inputting the PVDF reaction mixture into a plate and frame filter press for filtration;

[0010] S2: crushing the PVDF filter cake obtained by filter pressing, adding a washing liquid mixed with an organic dispersant, and stirring to form a PVDF slurry;

[0011] S3: inputting the high-temperature washing liquid and the PVDF slurry into a plate and frame filter press for filtering;

[0012] S4: Detect the conductivity of the waste liquid generated by the filter pressing in step S3: if the measured conductivity is greater than the target value, return to step S2; if the measured conductivity is less than or equal to the target value, the washing is completed.

[0013] Preferably, in step S1, the PVDF reaction mixture is an emulsion or a suspension.

[0014] Preferably, the pressure of the filter press is 0.3-0.6 MPa.

[0015] Preferably, in step S2, the organic dispersant is an alcohol dispersant, and the weight ratio of the washing liquid, the organic dispersant and the PVDF filter cake is 3-4:1:1.

[0016] Preferably, in step S2, the organic dispersant is one or more of methanol, ethanol and isopropanol.

[0017] Preferably, in step S2, the stirring time is not less than 30 minutes.

[0018] Preferably, in step S3, the temperature of the high-temperature washing liquid is 60-80° C., and the single introduction time of the high-temperature washing liquid is 30-60 minutes.

[0019] Preferably, the washing liquid is pure water, the resistance of the pure water is not less than 16 megohms and the TOC is not higher than 0.1 mg / L.

[0020] The second aspect of the present invention discloses a washing system for vinylidene fluoride polymers, wherein PVDF is washed by any of the above-mentioned washing methods;

[0021] The washing system comprises:

[0022] a first delivery pump, a plate and frame filter press, a screw conveyor, a transfer stirring tank, a conductivity detection mechanism, a washing liquid storage tank, an organic dispersant storage tank, and a second delivery pump;

[0023] The reaction kettle located upstream of the washing system is connected to the plate and frame filter press via a first delivery pump;

[0024] The plate-frame filter press is connected to the transfer stirring tank and the wet material bin located downstream of the washing system through a screw conveyor, and the transfer stirring tank and the wet material bin are located at both ends of the screw conveyor respectively; a reflux pump is also provided between the transfer stirring tank and the plate-frame filter press;

[0025] The conductivity detection mechanism is used to detect the conductivity of the waste liquid discharged from the plate and frame filter press;

[0026] The washing liquid storage tank and the organic dispersant storage tank are connected to the plate and frame filter press and the transfer stirring tank through a second delivery pump.

[0027] Preferably, the first delivery pump is a pneumatic diaphragm pump, the second delivery pump is a pneumatic diaphragm pump, and the reflux pump is a pneumatic diaphragm pump.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention provides an efficient and low-cost method for washing polymerized PVDF resin; the time-consuming original washing method (8 hours) is reduced to 3 hours, and the water consumption per ton can be controlled within 10m 3 within;

[0030] (2) The washing method of the present invention can improve the hydrophilicity problem of the PVDF washing process by adding a certain proportion of organic dispersant, and then can quickly remove the residual organic matter on the surface of PVDF and its inner part during the washing process, thereby optimizing the production process, reducing costs, and being more efficient and environmentally friendly; at the same time, the product obtained by washing has better performance, lower VOC residue in the product, and better high-temperature yellowing (whiteness of the product). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a process for washing a vinylidene fluoride polymer;

[0032] Figure 2 It is a schematic diagram of the structure of the washing system of vinylidene fluoride polymer;

[0033] In the figure: 1-first delivery pump; 2-plate and frame filter press; 3-screw conveyor; 4-transfer stirring tank; 5-conductivity detection mechanism; 6-washing liquid storage tank; 7-organic dispersant storage tank; 8-second delivery pump; 9-reactor; 10-wet material silo. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] In the following description, unless otherwise specified, the reagents used are conventional commercially available products, and the methods used are well known in the art.

[0036] A method for washing a vinylidene fluoride polymer, such as Figure 1 As shown, the following steps are included:

[0037] S1: inputting the PVDF reaction mixture into the plate-frame filter press 2 for filter pressing;

[0038] S2: crushing the PVDF filter cake obtained by filter pressing, adding a washing liquid mixed with an organic dispersant, and stirring to form a PVDF slurry;

[0039] S3: inputting the high-temperature washing liquid and the PVDF slurry into the plate-frame filter press 2 for filter pressing;

[0040] S4: Detect the conductivity of the waste liquid generated by the filter pressing in step S3: if the measured conductivity is greater than the target value, return to step S2; if the measured conductivity is less than or equal to the target value, the washing is completed.

[0041] in:

[0042] In step S1, the PVDF reaction mixture is an emulsion or a suspension; the PVDF reaction mixtures used in the following examples are all emulsions with a solid content of 20% and a density of 1.03 g / cm 3 (The density of water can be directly used in the calculation).

[0043] In steps S2 and S3, the pressure of the filter press is 0.3-0.6 MPa, and the pressure holding time is 5 min.

[0044] In step S2, the organic dispersant is one or more of methanol, ethanol and isopropanol. Considering the toxicity and safety of the reagent, ethanol is preferably used; the washing liquid is pure water, the resistance of the pure water is not less than 16 megohms and the TOC is not higher than 0.1 mg / L; the weight ratio of the washing liquid, the organic dispersant and the PVDF filter cake is 3 to 4:1:1, preferably 4:1:1; the stirring frequency is 20 Hz, and the time is not less than 30 min.

[0045] In step S3, the high temperature washing liquid is high temperature pure water, the temperature is 60-80°C, and the single introduction time of the high temperature washing liquid is 30-60 minutes, preferably 40 minutes. The ethanol and other organic matters are removed by continuously introducing the high temperature pure water.

[0046] In step S4, the target conductivity value of the waste liquid is 1 μS / cm.

[0047] A washing system for vinylidene fluoride polymers, such as Figure 2 As shown, PVDF is washed using the washing method described above;

[0048] The washing system comprises:

[0049] A first delivery pump 1, a plate and frame filter press 2, a screw conveyor 3, a transfer stirring tank 4, a conductivity detection mechanism 5, a washing liquid storage tank 6, an organic dispersant storage tank 7, and a second delivery pump 8;

[0050] The reaction kettle 9 located upstream of the washing system is connected to the plate and frame filter press 2 via the first delivery pump 1;

[0051] The plate-frame filter press 2 is connected to the transfer stirring tank 4 and the wet material bin 10 located downstream of the washing system through a screw conveyor 3, respectively. The transfer stirring tank 4 and the wet material bin 10 are located at both ends of the screw conveyor 3, respectively. A reflux pump is also provided between the transfer stirring tank 4 and the plate-frame filter press 2.

[0052] The conductivity detection mechanism 5 is used to detect the conductivity of the waste liquid discharged from the plate and frame filter press 2;

[0053] The washing liquid storage tank 6 and the organic dispersant storage tank 7 are connected to the plate and frame filter press 2 and the transfer stirring tank 4 through a second delivery pump 8 .

[0054] in:

[0055] The screw conveyor 3 is arranged at the filter cake discharge port below the plate and frame filter press 2. In addition to conveying the filter cake, it can also crush the filter cake. One end of the screw conveyor 3 is a transfer mixing tank 4, and the other end is a wet material bin 10. The conveying path of the screw conveyor 3 is switched by adjusting the forward and reverse rotation of the screw conveyor 3.

[0056] The conductivity detection mechanism 5 is a conductivity detector: it can be an external device that performs detection by sampling wastewater; it can also be an online conductivity detector arranged on the waste liquid pipeline of the plate and frame filter press 2.

[0057] The first delivery pump 1 is a pneumatic diaphragm pump, the second delivery pump 8 is a pneumatic diaphragm pump, and the reflux pump is a pneumatic diaphragm pump.

[0058] The pipeline between the washing liquid storage tank 6 and the second delivery pump 8, and the pipeline between the organic dispersant storage tank 7 and the second delivery pump 8 are respectively provided with flow meters for mixing the organic dispersant and the washing liquid in proportion. Since the washing liquid storage tank 6 and the organic dispersant storage tank 7 are connected to the second delivery pump 8 together, but there is a need to open them separately, the washing liquid storage tank 6 and the organic dispersant storage tank 7 are in parallel, and a three-way valve is used to switch between different feeding methods; similarly, the second delivery pump 8 needs to deliver different feed liquids to the plate-frame filter press 2 and the transfer stirring tank 4 respectively, so the pipelines led out from the second delivery pump 8 are also connected to the plate-frame filter press 2 and the transfer stirring tank 4 respectively by a three-way valve to feed them separately.

[0059] Since the organic dispersant used in the washing process is volatile and flammable, the washing system as a whole needs to be placed in a closed ventilation environment (placed in a closed space and equipped with ventilation equipment, such as an exhaust fan, etc.) to wash the PVDF polymer, and the electrical appliances and equipment used are corresponding explosion-proof electrical appliances and explosion-proof equipment. In addition, an ethanol distillation recovery device (such as a flash tower, a distillation tower, etc.) can also be connected downstream of the ventilation equipment to recover the volatilized ethanol.

[0060] In the following embodiments, the water used is pure water that meets the above requirements.

[0061] Example 1

[0062] ①To volume 2m 3 Plate and frame filter press 2, pumping 1m 3 The polymerized PVDF emulsion with a solid content of 20% is squeezed, and the pressure is maintained for 5 minutes to remove the mother liquid. The pressure is released, the filter plate is opened, and the PVDF filter cake is crushed and conveyed to the transfer stirring tank 4 by the screw conveyor 3.

[0063] ② Measure and convert through the flow meter, add 800kg of water and 200kg of ethanol from the washing liquid storage tank 6 and the organic dispersant storage tank 7 to the transfer stirring tank 4 through the second delivery pump 8, and stir for 30 minutes to form a PVDF dispersed slurry.

[0064] ③ The dispersed slurry is returned to the plate and frame filter press 2 through the reflux pump, and 60°C high-purity water is introduced from the washing liquid storage tank 6 through the second delivery pump 8 for 30 minutes; squeeze, and the conductivity of the squeezed water is tested by the conductivity detection mechanism 5 until it is ≤1μs / cm, otherwise repeat steps ② to ③;

[0065] ④ After the conductivity of the squeezed water is qualified, the pressure is released, the screw conveyor 3 is reversed and the filter plate is opened, and the filter cake is sent to the wet material bin 10 through the screw conveyor 3, waiting for the next drying process to obtain PVDF solid powder.

[0066] Example 2

[0067] ①To volume 2m 3 Plate and frame filter press 2, pumping 1m 3 The polymerized PVDF emulsion with a solid content of 20% is squeezed, and the pressure is maintained for 5 minutes to remove the mother liquid. The pressure is released, the filter plate is opened, and the PVDF filter cake is crushed and conveyed to the transfer stirring tank 4 by the screw conveyor 3.

[0068] ② Measure and convert through the flow meter, add 800kg of water and 200kg of ethanol from the washing liquid storage tank 6 and the organic dispersant storage tank 7 to the transfer stirring tank 4 through the second delivery pump 8, and stir for 30 minutes to form a PVDF dispersed slurry.

[0069] ③ The dispersed slurry is returned to the plate and frame filter press 2 through the reflux pump, and 80°C high-purity water is introduced from the washing liquid storage tank 6 through the second delivery pump 8 for 40 minutes; squeeze, and the conductivity of the squeezed water is tested by the conductivity detection mechanism 5 until it is ≤1μs / cm, otherwise repeat steps ② to ③;

[0070] ④ After the conductivity of the squeezed water is qualified, the pressure is released, the screw conveyor 3 is reversed and the filter plate is opened, and the filter cake is sent to the wet material bin 10 through the screw conveyor 3, waiting for the next drying process to obtain PVDF solid powder.

[0071] Example 3

[0072] ①To volume 2m 3 Plate and frame filter press 2, pumping 1m 3 The polymerized PVDF emulsion with a solid content of 20% is squeezed, and the pressure is maintained for 5 minutes to remove the mother liquid. The pressure is released, the filter plate is opened, and the PVDF filter cake is crushed and conveyed to the transfer stirring tank 4 by the screw conveyor 3.

[0073] ② Measure and convert through the flow meter, add 600kg of water and 200kg of ethanol from the washing liquid storage tank 6 and the organic dispersant storage tank 7 to the transfer stirring tank 4 through the second delivery pump 8, and stir for 30 minutes to form a PVDF dispersed slurry.

[0074] ③ The dispersed slurry is returned to the plate and frame filter press 2 through the reflux pump, and 60°C high-purity water is introduced from the washing liquid storage tank 6 through the second delivery pump 8 for 40 minutes; squeeze, and the conductivity of the squeezed water is tested by the conductivity detection mechanism 5 until it is ≤1μs / cm, otherwise repeat steps ② to ③;

[0075] ④ After the conductivity of the squeezed water is qualified, the pressure is released, the screw conveyor 3 is reversed and the filter plate is opened, and the filter cake is sent to the wet material bin 10 through the screw conveyor 3, waiting for the next drying process to obtain PVDF solid powder.

[0076] Example 4

[0077] ①To volume 2m 3 Plate and frame filter press 2, pumping 1m 3 The polymerized PVDF emulsion with a solid content of 20% is squeezed, and the pressure is maintained for 5 minutes to remove the mother liquid. The pressure is released, the filter plate is opened, and the PVDF filter cake is crushed and conveyed to the transfer stirring tank 4 by the screw conveyor 3.

[0078] ② Measure and convert through the flow meter, add 800kg of water and 200kg of ethanol from the washing liquid storage tank 6 and the organic dispersant storage tank 7 to the transfer stirring tank 4 through the second delivery pump 8, and stir for 30 minutes to form a PVDF dispersed slurry.

[0079] ③ The dispersed slurry is returned to the plate and frame filter press 2 through the reflux pump, and 60°C high-purity water is introduced from the washing liquid storage tank 6 through the second delivery pump 8 for 60 minutes; squeeze, and the conductivity of the squeezed water is tested by the conductivity detection mechanism 5 until it is ≤1μs / cm, otherwise repeat steps ② to ③;

[0080] ④ After the conductivity of the squeezed water is qualified, the pressure is released, the screw conveyor 3 is reversed and the filter plate is opened, and the filter cake is sent to the wet material bin 10 through the screw conveyor 3, waiting for the next drying process to obtain PVDF solid powder.

[0081] Comparative Example 1

[0082] ①To volume 2m 3 Plate and frame filter press 2, pumping 1m 3 The polymerized PVDF emulsion with a solid content of 20% is squeezed, and the pressure is maintained for 5 minutes to remove the mother liquid. The pressure is released, the filter plate is opened, and the PVDF filter cake is crushed and conveyed to the transfer stirring tank 4 by the screw conveyor 3.

[0083] ② Measure and convert through the flow meter, add 3000 kg of water from the washing liquid storage tank 6 and the organic dispersant storage tank 7 to the transfer stirring tank 4 through the second delivery pump 8, and stir for 30 minutes to form a PVDF dispersed slurry.

[0084] ③ The dispersed slurry is returned to the plate and frame filter press 2 through the reflux pump, and 60°C high-purity water is introduced from the washing liquid storage tank 6 through the second delivery pump 8 for 40 minutes; squeeze, and the conductivity of the squeezed water is tested by the conductivity detection mechanism 5 until it is ≤1μs / cm, otherwise repeat steps ② to ③;

[0085] ④ After the conductivity of the squeezed water is qualified, the pressure is released, the screw conveyor 3 is reversed and the filter plate is opened, and the filter cake is sent to the wet material bin 10 through the screw conveyor 3, waiting for the next drying process to obtain PVDF solid powder.

[0086] Performance Testing:

[0087] (1) Conductivity test: Take 500 mL of water after the second squeezing, let it stand for 1 minute, and test it using a conductivity meter (Ray-Magnetics DDS-307A).

[0088] (2) Solid powder VOC test: Use Mettler halogen moisture meter, model HE83, take a sample of 10g, set the temperature to 105°C, and set the time to 10 minutes to obtain the result M1. Then take 2g and use the Karl Fischer method to test the moisture content M2. The VOC content is: M1-M2;

[0089] (3) Solid powder high temperature yellowing test, refer to Example 1 of CN202311691224.7 "A test method and quality evaluation method for high temperature yellowing of fluorinated polymers";

[0090] (4) The flow meter calculates the required amount of pure water and dispersion dosage; the timer calculates the required washing time.

[0091] According to the performance tests of (1) to (4), Examples 1 to 4 and Comparative Example 1 were tested. The test results are shown in Table 1.

[0092] Table 1 Performance test results

[0093]

[0094] The test results in Table 1 show that Examples 1 to 4 using the new washing method proposed in this solution have a significant improvement effect compared with Comparative Example 1 of the conventional method, and have greatly improved water usage, time usage, and high-temperature yellowing of the product. Among them, Example 2 performs best in various parameters.

[0095] The method of the present invention can improve the hydrophilicity problem of the PVDF washing process by adding a certain proportion of ethanol (or methanol, isopropanol), quickly remove the residual organic matter on the surface of PVDF and wrapped, optimize the production process, reduce costs, and be more efficient and environmentally friendly; at the same time, the product performance is better.

[0096] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. 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 work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for washing a vinylidene fluoride polymer, characterized in that: The steps include: S1: inputting the PVDF reaction mixture into a plate and frame filter press for filtration; S2: crushing the PVDF filter cake obtained by filter pressing, adding a washing liquid mixed with an organic dispersant, and stirring to form a PVDF slurry; S3: inputting the high-temperature washing liquid and the PVDF slurry into a plate and frame filter press for filtering; S4: Detect the conductivity of the waste liquid generated by the filter pressing in step S3: if the measured conductivity is greater than the target value, return to step S2; if the measured conductivity is less than or equal to the target value, the washing is completed.

2. The method for washing a vinylidene fluoride polymer according to claim 1, characterized in that: In step S1, the PVDF reaction mixture is an emulsion or a suspension.

3. The method for washing a vinylidene fluoride polymer according to claim 1, characterized in that: The pressure of the filter press is 0.3-0.6 MPa.

4. The method for washing a vinylidene fluoride polymer according to claim 1, characterized in that: In step S2, the organic dispersant is an alcohol dispersant, and the weight ratio of the washing liquid, the organic dispersant and the PVDF filter cake is 3-4:1:

1.

5. The method for washing a vinylidene fluoride polymer according to claim 4, characterized in that: In step S2, the organic dispersant is one or more of methanol, ethanol and isopropanol.

6. The method for washing a vinylidene fluoride polymer according to claim 1, characterized in that: In step S2, the stirring time is not less than 30 minutes.

7. The method for washing a vinylidene fluoride polymer according to claim 1, characterized in that: In step S3, the temperature of the high-temperature washing liquid is 60-80° C., and the single introduction time of the high-temperature washing liquid is 30-60 minutes.

8. The method for washing a vinylidene fluoride polymer according to claim 1, characterized in that: The cleaning liquid is pure water, the resistance of the pure water is not less than 16 megohms and the TOC is not higher than 0.1 mg / L.

9. A washing system for vinylidene fluoride polymers, characterized in that: Washing PVDF using the washing method described in any one of claims 1 to 8; The washing system comprises: A first delivery pump (1), a plate and frame filter press (2), a screw conveyor (3), a transfer stirring tank (4), a conductivity detection mechanism (5), a washing liquid storage tank (6), an organic dispersant storage tank (7) and a second delivery pump (8); A reaction kettle (9) located upstream of the washing system is connected to a plate and frame filter press (2) via a first delivery pump (1); The plate-frame filter press (2) is connected to the transfer stirring tank (4) and the wet material bin (10) located downstream of the washing system through a screw conveyor (3), respectively. The transfer stirring tank (4) and the wet material bin (10) are located at two ends of the screw conveyor (3), respectively. A reflux pump is also provided between the transfer stirring tank (4) and the plate-frame filter press (2); The conductivity detection mechanism (5) is used to detect the conductivity of the waste liquid discharged from the plate and frame filter press (2); The washing liquid storage tank (6) and the organic dispersant storage tank (7) are connected to the plate and frame filter press (2) and the transfer stirring tank (4) via a second delivery pump (8).

10. A washing system for vinylidene fluoride polymer according to claim 9, characterized in that: The first delivery pump (1) is a pneumatic diaphragm pump, the second delivery pump (8) is a pneumatic diaphragm pump, and the reflux pump is a pneumatic diaphragm pump.

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