A self-priming vacuum membrane distillation sewage treatment device

Abstract

The present invention discloses a self-priming vacuum membrane distillation sewage treatment device, comprising: a waste liquid storage device for storing waste liquid with a certain temperature; a membrane distillation structure, comprising a vacuum flow channel, a feed flow channel connected to the waste liquid storage device through a one-way valve, and a membrane assembly arranged between the vacuum flow channel and the feed flow channel; a condensed water collection container connected to the vacuum flow channel for collecting condensed water in the vacuum flow channel; a refrigeration device for providing a low-temperature environment with a temperature lower than the waste liquid temperature for the vacuum flow channel; and a vacuum pumping structure connected to the vacuum flow channel for preparing a negative pressure environment for the vacuum flow channel. The self-priming vacuum membrane distillation sewage treatment device has a simple structure and can quickly complete the conversion of wastewater into pure water without additional energy consumption. It can be used as a small and portable sewage treatment device that meets the pure water preparation needs in harsh outdoor environments, and can also be adjusted in size accordingly for promotion and application in the environmental protection green energy industry.

Description

Technical Field

[0001] The invention relates to the technical field of green energy application, and in particular to a self-priming vacuum membrane distillation sewage treatment device. Background Art

[0002] The shortage of fresh water resources has become an urgent problem that needs to be solved by countries around the world. Due to the accelerated modernization process, people's living standards are gradually improving, and a series of human factors such as over-exploitation of groundwater and serious surface water pollution have led to less and less available water resources.

[0003] As a water purification technology, membrane distillation (MD) has developed rapidly in recent years and is often used for seawater desalination and treatment of high-salinity wastewater. Unlike conventional membrane processes, membrane distillation is driven by the vapor pressure difference generated by the temperature difference on both sides of the hydrophobic porous membrane. This is a heat-driven separation process in which only volatile molecules can pass through the hydrophobic porous membrane, and non-volatile solutes are completely excluded at the gas-liquid interface and remain in the feed liquid. Membrane distillation is the method with the highest interception rate among the currently known water purification technologies, and can achieve a salt interception rate of 100%. However, compared with other mainstream water purification technologies, since membrane distillation technology requires the formation of a cold and hot temperature difference to construct a driving force for steam transmembrane mass transfer, and consumes electrical energy to drive fluid circulation, the overall energy consumption of the membrane distillation process is relatively high, which is also a key issue limiting its large-scale industrial application.

[0004] In the purification process of printing and dyeing wastewater in sewage treatment plants, biological wastewater treatment needs to be heated to ensure the working environment of anaerobic bacteria. The final discharged waste liquid temperature is between 40-45°C. Direct discharge will cause greater environmental pollution and energy loss. Therefore, how to utilize low-grade waste heat and adopt reasonable methods to purify waste liquid, achieve energy conservation and emission reduction, and resource utilization of waste has become a key factor in improving the energy efficiency of sewage treatment plants and reducing economic costs.

[0005] In view of this, it is necessary to design a self-priming vacuum membrane distillation wastewater treatment device to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a self-priming vacuum membrane distillation sewage treatment device which has a simple structure, can reasonably utilize the heat energy of the waste liquid itself to extract pure water from the waste liquid and does not require additional energy supply.

[0007] To achieve the above-mentioned purpose, the present invention provides a self-priming vacuum membrane distillation sewage treatment device, comprising:

[0008] A waste liquid storage tank is used to store waste liquid at a certain temperature;

[0009] A membrane distillation structure, comprising a vacuum flow channel, a feed flow channel connected to the waste liquid storage via a one-way valve, and a membrane assembly disposed between the vacuum flow channel and the feed flow channel;

[0010] A condensed water collection container, connected to the vacuum flow channel, and used for collecting condensed water in the vacuum flow channel;

[0011] Refrigeration equipment, used for providing a low temperature environment for the vacuum flow channel with a temperature lower than the waste liquid temperature;

[0012] The vacuum pumping structure is connected to the vacuum flow channel and is used for preparing a negative pressure environment of the vacuum flow channel.

[0013] As a further improvement of the present invention, the condensed water collection container is located below the vacuum flow channel.

[0014] As a further improvement of the present invention, the vacuum flow channel is connected to the condensed water collecting container via a connecting hole, and the connecting hole is arranged on a side of the vacuum flow channel close to the refrigeration equipment.

[0015] As a further improvement of the present invention, the refrigeration device is a condensation plate arranged on a side of the vacuum flow channel away from the feed flow channel.

[0016] As a further improvement of the present invention, a fin structure is provided on the side of the condensation plate away from the vacuum flow channel.

[0017] As a further improvement of the present invention, the membrane component is a micro-nano composite membrane prepared by using polyethylene terephthalate material as a substrate and grafting polytetrafluoroethylene material.

[0018] As a further improvement of the present invention, the average pore size of the micro-nano composite membrane is 0.22-5 μm.

[0019] As a further improvement of the present invention, the surface of the micro-nano composite membrane is provided with a super-hydrophobic nano-wire coating located in the inner layer and a super-hydrophobic fluorinated coating located in the outer layer, maintaining a contact angle greater than 150° and a sliding angle less than 10°.

[0020] As a further improvement of the present invention, the vacuum pumping structure is a manual air pump or a vacuum pump.

[0021] As a further improvement of the present invention, the vacuum pumping structure is connected to the vacuum flow channel via a one-way valve.

[0022] As a further improvement of the present invention, the vacuum flow channel is sealed with a fluororubber product having strong corrosion resistance.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention can prevent the formed condensed water from gathering in the vacuum flow channel by disposing a condensed water collecting container connected to the vacuum flow channel below the vacuum flow channel, thereby occupying the capacity of the vacuum flow channel, reducing the volume occupied by the gas in the vacuum flow channel, resulting in a reduction in the compressible gas and reducing the vacuum pumping effect of the device, so that the device may not be able to generate sufficient pressure difference to drive the waste liquid from the waste liquid storage device into the feed liquid flow channel to complete automatic feeding, and the preparation efficiency of pure water may be affected due to the reduction in vacuum effect. In addition, it can also prevent the condensed water from gathering in the vacuum flow channel, so that the side of the vacuum flow channel close to the refrigeration equipment will generate thermal resistance due to the adhesion of condensed water, which will affect the heat dissipation effect of the refrigeration equipment and reduce the temperature difference on both sides of the membrane.

[0025] 2. The self-priming vacuum membrane distillation sewage treatment device of the present invention is simple and can quickly complete the conversion of wastewater into pure water without additional energy consumption, and can be adjusted in size according to actual use and use environment. It can not only obtain a small and portable sewage treatment device that meets the pure water preparation needs under harsh outdoor conditions, but also can be adjusted in size accordingly for promotion and application in the environmental protection green energy industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a self-priming vacuum membrane distillation wastewater treatment device.

[0027] Reference numerals

[0028] 10. Waste liquid storage tank; 21. Feed flow channel; 22. Membrane assembly; 23. Vacuum flow channel; 30. Condensation plate; 31. Fin structure; 40. Manual vacuum pump; 50. Condensate collection container; 60. Connection hole; 70. One-way valve. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0031] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0032] like Figure 1As shown, the present invention provides a self-priming vacuum membrane distillation sewage treatment device, comprising:

[0033] The waste liquid storage tank 10 is used to store waste liquid at a certain temperature;

[0034] The membrane distillation structure comprises a vacuum flow channel 23, a feed flow channel 21 connected to the waste liquid storage 10 via a one-way valve 70, and a membrane assembly 22 disposed between the vacuum flow channel 23 and the feed flow channel 21;

[0035] A condensed water collection container 50 is communicated with the vacuum flow channel 23 and is used for collecting condensed water in the vacuum flow channel 23;

[0036] Refrigeration equipment, used to provide a low-temperature environment for the vacuum flow channel 23 with a temperature lower than the waste liquid temperature;

[0037] The vacuum pumping structure is connected to the vacuum flow channel 23 and is used for preparing a negative pressure environment of the vacuum flow channel 23 .

[0038] Specifically, the refrigeration device is a condensation plate 30 arranged on the side of the vacuum flow channel 23 away from the feed flow channel 21; a fin structure 31 is arranged on the side of the condensation plate 30 away from the vacuum flow channel 23 to cool the vacuum flow channel 23 under natural convection, so that a temperature gradient is formed along the feed flow channel 21 to the condensation plate 30, so that the water vapor in the waste liquid passes through the membrane holes of the membrane assembly 22 under the action of the vapor pressure difference and enters the vacuum flow channel 23, and condenses on the surface of the condensation plate 30 to form condensed water and then flows into the condensed water collection container 50. Exemplarily, the fin is made of pure copper material and is a toothed structure with a pitch of 2 mm.

[0039] Specifically, the condensate collection container 50 is located below the vacuum flow channel 23 to collect and temporarily store the condensate, so as to prevent the condensate formed on the condensation plate 30 from accumulating in the vacuum flow channel 23, occupying the capacity of the vacuum flow channel 23 and causing a reduction in the gas inventory in the vacuum flow channel 23, which in turn reduces the vacuum effect due to the reduction in compressible gas during the vacuum treatment. As a result, the device may not be able to generate sufficient pressure difference to drive the waste liquid from the waste liquid storage tank 10 into the feed liquid flow channel to complete automatic feeding, and the membrane distillation effect may be affected due to the reduced pressure difference on both sides of the membrane. In addition, it can also prevent the condensate from accumulating in the vacuum flow channel 23, so that the condensate plate 30 generates thermal resistance due to the attachment of a large amount of condensate, thereby affecting the heat dissipation effect and reducing the temperature difference on both sides of the membrane.

[0040] Exemplarily, the vacuum flow channel 23 is connected to the condensed water collecting container 50 through a connecting hole 60, and the connecting hole 60 is located on the side of the vacuum flow channel 23 close to the condensation plate 30, and is arranged in a direction parallel to the side wall of the vacuum flow channel 23 to form a gap for the condensed water to flow into the condensed water collecting container 50 through the vacuum flow channel 23, so that when the condensed water flows into the condensed water collecting container 50 through the connecting hole 60, the condensed water can temporarily serve as an isolation member for isolating the vacuum flow channel 23 from the condensed water collecting container 50. At this time, as the waste liquid purification proceeds, the pressure in the vacuum flow channel 23 gradually increases. Under the isolation effect of the condensed water, the pressure in the condensed water collecting container 50 will be lower than the pressure in the vacuum flow channel 23, and then under the effect of the pressure difference, The condensed water quickly flows into the condensed water collecting container 50. When the condensed water in the vacuum flow channel 23 flows into the condensed water collecting container 50, the vacuum flow channel 23 and the condensed water collecting container 50 are connected again. At this time, there is still a slight pressure difference between the vacuum flow channel 23 and the condensed water collecting container 50. Since the connecting hole 60 is correspondingly arranged below the condensation plate 60, under the action of the slight pressure difference between the vacuum flow channel 23 and the condensed water collecting container 50, the newly condensed condensed droplets formed in the lower part of the condensation plate 30 will be driven downward through the connecting hole 60 to flow into the condensed water collecting container 50, and then quickly break away from the surface of the condensation plate. To a certain extent, it can avoid the condensed droplets adhering to the surface of the condensation plate 30 to generate thermal resistance and affect the heat dissipation effect.

[0041] Specifically, the length and width of the connecting hole 60 are set according to the output of condensed water in the vacuum flow channel 23 and actual conditions.

[0042] Specifically, the membrane assembly 22 is a micro-nano composite membrane made of polyethylene terephthalate material as a substrate and grafted with polytetrafluoroethylene material. Exemplarily, the average pore size of the micro-nano composite membrane is 0.22-5 μm, which avoids membrane wetting due to excessive membrane pore size and affects the waste liquid purification effect.

[0043] Specifically, the surface of the micro-nano composite membrane is provided with a super-hydrophobic nano-wire coating located in the inner layer and a super-hydrophobic fluorinated coating located in the outer layer by a liquid phase deposition method, maintaining a contact angle greater than 150° and a sliding angle less than 10°, thereby increasing the gas-liquid contact area, improving the mass transfer flux, and preventing the membrane from wetting and failing, so that the device can maintain long-term operation stability. Exemplarily, the reagent used to prepare the super-hydrophobic nano-wire coating is methyltrichlorosilane, and the reagent used to prepare the super-hydrophobic fluorinated coating is 1H,1H,2H,2H-perfluorodecyltrichlorosilane.

[0044] Specifically, the vacuum flow channel 23 is sealed with a fluororubber product with strong corrosion resistance. Compared with silicone rubber, the fluororubber product has a higher density and is oil-resistant, and can maintain a good sealing effect even when it contacts organic matter in sewage.

[0045] Specifically, the vacuum pumping structure is connected to the vacuum flow through a one-way valve, and the vacuum pumping structure is a manual air pump 40 or a vacuum pump.

[0046] Exemplarily, the vacuum pump is a manual vacuum pump 40; the volume of the feed channel 21 is 25 mL; the volume of the vacuum channel 23 is 25 mL. Under the action of the manual vacuum pump 40, a negative pressure is formed inside the vacuum channel 23, and the absolute pressure can reach 20 KPa, so that the device can maintain stable operation for more than 6 hours;

[0047] The waste liquid is low-temperature printing and dyeing waste liquid, and the waste liquid temperature is greater than or equal to 40°C. In this embodiment, the waste liquid temperature is 40°C, and the self-priming vacuum membrane distillation wastewater treatment device is at room temperature.

[0048] The average pore size of the micro-nano composite membrane is 5 μm, the water output is 100 mL / h, and the area of ​​the connecting hole 60 is 0.1389 cm 2 , the length of the connection hole 60 is 2 cm. Although the size of the connection hole 60 is relatively small, during use, in the intermittent vacuum state, there will be an intermittent pressure difference between the vacuum flow channel 23 and the condensed water collection container 50, so the connection hole 60 is too small to affect the flow of condensed water into the condensed water collection container 50. That is, the existence of the connection hole 60 can facilitate the condensed water to flow from the vacuum flow channel 23 into the condensed water collection container 50, and also facilitate the new condensed droplets at the bottom of the condensation plate 30 to quickly leave the surface of the condensation plate 30.

[0049] When in use, the vacuum channel 23 is intermittently evacuated by a manual vacuum pump 40, and the condensation plate 30 cools the vacuum channel 23 under natural convection conditions, so that a temperature difference and a pressure difference are formed on both sides of the micro-nano composite membrane; the existence of the pressure difference will cause the gas in the feed channel 21 to enter the vacuum channel 23, thereby making the pressure of the feed channel 21 lower than the waste liquid storage 10 connected thereto, and further, a pressure difference will be formed between the feed channel 21 and the waste liquid storage 10, so that the waste liquid in the waste liquid storage 10 will spontaneously flow into the feed channel 21 ; Since the temperature of the waste liquid is higher than that of the vacuum flow channel 23, driven by the vapor pressure difference, the water vapor in the waste liquid enters the vacuum flow channel 23 through the membrane holes, and condenses on the condensation plate 30 to form condensed water, and then flows downward into the condensed water collection container 50, thereby extracting pure water from the waste liquid. During the extraction process, the low-temperature waste heat in the waste liquid is fully utilized, thereby reducing the overall energy consumption of the sewage treatment plant without the need for additional heat source. In addition, during the pure water preparation process, the presence of negative pressure can also reduce the mass transfer resistance, accelerate the movement rate of water vapor, and improve the pure water preparation efficiency. In addition, the existence of the connecting hole 60, on the one hand, facilitates the condensed water formed in the vacuum flow channel 23 to flow into the condensed water collection container 50, and on the other hand, by reasonably designing the size of the connecting hole 60, when the condensed water flows through the connecting hole, the vacuum flow channel 23 and the condensed water collection container 50 are temporarily disconnected, so that as the purification proceeds, the pressure of the vacuum flow channel 23 is higher than that of the condensed water collection container 50, and a pressure difference is formed between the vacuum flow channel 23 and the condensed water collection container 50. Under the action of the pressure difference, the condensed water in the vacuum flow channel 23 can quickly flow into the condensed water collection container 50, and can also drive the newly condensed droplets in the lower part of the condensation plate 30 to quickly move downward and away from the surface of the condensation plate 30 to a certain extent.

[0050] The self-priming vacuum membrane distillation sewage treatment device has a simple structure and does not require continuous power equipment to enable the device to operate continuously and maintain water production performance. It has low energy consumption, and its specifications can be formulated according to actual uses and usage environments. For example, the manual vacuum pump 40 in this embodiment is used as a negative pressure preparation device, and the resulting device structure specifications are relatively small, which is easy to carry and can meet the needs of pure water preparation in the field environment. When pure water is lacking, the surrounding low-temperature water resources such as sweat, urine, etc. can be used to prepare pure water, and pure water extraction can be completed without additional energy consumption.

[0051] The condensate production is calculated according to Formula 1 and Formula 2:

[0052] Formula 1:

[0053] in:

[0054]

[0055]

[0056] Formula 2: α = exp(-4.5818*10 -4 S m -2.0443*10 -6 S m 2 )

[0057] J w : water flux;

[0058] R K : Knudsen diffusion mass transfer resistance;

[0059] R M : molecular diffusion mass transfer resistance;

[0060] R P : viscous flow mass transfer resistance;

[0061] α: Activity coefficient on the feed side

[0062] P vap，fm : Steam partial pressure on the feed side;

[0063] P vac : Absolute pressure of vacuum channel;

[0064] C wq : bending factor of membrane material;

[0065] H mb : film thickness;

[0066] M w : molar mass of water molecule;

[0067] R: gas constant;

[0068] T m : Steam temperature in the membrane pores;

[0069] C kx : membrane porosity;

[0070] R mb : membrane pore radius;

[0071] p α : total pressure;

[0072] p m : Steam pressure in membrane pores;

[0073] D wa : Diffusion coefficient of water vapor in air;

[0074] μ mv : Dynamic viscosity of gas in membrane pores;

[0075] ν m : gas specific volume in membrane pores;

[0076] S m : Wastewater salinity;

[0077] The heat transfer flux is calculated according to formula 3:

[0078] Formula 3: q c =h eff ×(T a,m -T wall )

[0079] q c : Heat flux

[0080] T α,m : Air gap temperature

[0081] T wall : Condensation plate temperature

[0082] h eff : Heat transfer coefficient.

[0083] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A self-priming vacuum membrane distillation sewage treatment device, characterized in that: include: A waste liquid storage tank is used to store waste liquid at a certain temperature; A membrane distillation structure, comprising a vacuum flow channel, a feed flow channel connected to the waste liquid storage via a one-way valve, and a membrane assembly disposed between the vacuum flow channel and the feed flow channel; A condensed water collection container is connected to the vacuum flow channel and is used to collect condensed water in the vacuum flow channel; the vacuum flow channel and the condensed water collection container are connected through a connecting hole, and the connecting hole is arranged on a side of the vacuum flow channel close to the refrigeration device; the condensed water collection container is located below the vacuum flow channel; Refrigeration equipment, used for providing a low temperature environment for the vacuum flow channel with a temperature lower than the waste liquid temperature; The vacuum pumping structure is connected to the vacuum flow channel and is used for preparing a negative pressure environment of the vacuum flow channel.

2. The self-priming vacuum membrane distillation sewage treatment device according to claim 1 is characterized in that: The refrigeration device is a condensation plate arranged on a side of the vacuum flow channel away from the feed flow channel.

3. The self-priming vacuum membrane distillation sewage treatment device according to claim 2 is characterized in that: The condensation plate is provided with a fin structure on one side away from the vacuum flow channel.

4. The self-priming vacuum membrane distillation sewage treatment device according to claim 1 is characterized in that: The membrane component is a micro-nano composite membrane prepared by taking polyethylene terephthalate material as a substrate and grafting polytetrafluoroethylene material.

5. The self-priming vacuum membrane distillation sewage treatment device according to claim 4 is characterized in that: The average pore size of the micro-nano composite membrane is 0.22-5 μm.

6. The self-priming vacuum membrane distillation sewage treatment device according to claim 4 is characterized in that: The surface of the micro-nano composite membrane is provided with a super-hydrophobic nano-wire coating located in an inner layer and a super-hydrophobic fluorinated coating located in an outer layer, maintaining a contact angle greater than 150 degrees and a sliding angle less than 10 degrees.

7. The self-priming vacuum membrane distillation sewage treatment device according to claim 1 is characterized in that: The vacuum pumping structure is a manual air pump or a vacuum pump.

8. The self-priming vacuum membrane distillation sewage treatment device according to claim 1 is characterized in that: The vacuum pumping structure is communicated with the vacuum flow channel via a one-way valve.

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