Device and process for treating salt-containing wastewater by using membrane distillation method

Abstract

The invention discloses a device and a process for treating salt-containing wastewater by using a membrane distillation method, and belongs to the technical field of wastewater treatment. The device comprises a particle filter column, a water inlet tank, a membrane distiller and a water outlet tank, wherein a particle filter material modified by a sodium hydroxide solution is arranged in the particle filter column; the particle filtering column comprises a water inlet formed in the bottom end and a water outlet formed in the top end; a heater is arranged in the water inlet tank and is communicated with a water inlet of the particle filtering column; a membrane component is arranged in the membrane distiller and divides the membrane distiller into a water inlet side and a water outlet side, the membrane distiller is provided with a first inlet and a first outlet which are formed in the water inlet side and a second inlet and a second outlet which are formed in the water outlet side, the first inlet is communicated with the water outlet of the particle filtering column, and the first outlet is communicated with the water inlet tank; a condensation mechanism is arranged in the water outlet tank, the second outlet is communicated with the inlet of the water outlet tank, and the outlet of the water outlet tank is communicated with the second inlet. The treatment effect of membrane distillation in high-salinity wastewater treatment can be improved, and the service life of a membrane is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of wastewater treatment, and in particular to a device and process for treating saline wastewater using membrane distillation. Background Art

[0002] Membrane distillation has the advantages of high recovery rate or zero liquid discharge, and is a promising wastewater treatment method. In addition, membrane distillation technology is not affected by the salinity of the influent, making it a research hotspot for saline wastewater treatment.

[0003] Salty wastewater contains Ca 2+ , Ba 2+ Mg 2+ 、CO3 2- and SO4 2- As the water recovery rate increases during membrane distillation, the salt solution becomes supersaturated, and crystals precipitate on the membrane surface and in the solution and settle on the membrane surface to form a membrane scaling layer. Membrane scaling leads to a decrease in membrane distillation flux and an increase in effluent conductivity. The growth of crystals in the membrane pores destroys the membrane structure and induces membrane wetting, which seriously limits the application of membrane distillation technology in the treatment of saline wastewater.

[0004] Feedwater pretreatment, membrane modification and optimization of operating conditions are common methods to prevent scaling and scaling-induced wetting in membrane distillation. Compared with the modification of membrane performance and the optimization of operating conditions, the feedwater pretreatment technology to regulate water quality has become an important method to control scaling-induced wetting in membrane distillation systems. Among various pretreatment methods, filtration technology is the main pretreatment method. However, the traditional prefiltration step can neither control the inorganic salt ions before membrane distillation nor the inorganic salts precipitated during membrane distillation. Summary of the invention

[0005] The present application provides a device and process for treating saline wastewater using membrane distillation, which can improve the treatment effect of membrane distillation in high-salt wastewater treatment and extend the service life of the membrane.

[0006] This application is implemented as follows: In a first aspect, the present application provides a device for treating saline wastewater using a membrane distillation method, comprising: A particle filter column, wherein the particle filter column has a particle filter material, and the particle filter material is obtained after being modified by a sodium hydroxide solution; the particle filter column comprises a water inlet and a water outlet, the water inlet is arranged at the bottom end of the particle filter column, and the water outlet is arranged at the top end of the particle filter column; and An inlet water tank is provided with a heater for heating the saline wastewater. The saline wastewater in the inlet water tank can enter the particle filter column through the water inlet of the particle filter column. A membrane distiller, wherein the membrane distiller has a membrane assembly, the membrane assembly divides the membrane distiller into a water inlet side and a water outlet side, the membrane distiller has a first inlet and a first outlet arranged on the water inlet side, and a second inlet and a second outlet arranged on the water outlet side, the first inlet is connected to the water outlet of the particle filter column, and the first outlet is connected to the water inlet tank; and A water outlet water tank is provided with a condensing mechanism, the second outlet is communicated with the inlet of the water outlet water tank, and the outlet of the water outlet water tank is communicated with the second inlet.

[0007] In a possible implementation, a temperature detector and / or a conductivity detector is provided in the outlet water tank.

[0008] In a possible embodiment, a water collecting tank is further included, and the outlet water tank and the water collecting tank are connected via an overflow pipe, wherein an end of the overflow pipe located in the outlet water tank has a pipe opening higher than an end of the overflow pipe located in the water collecting tank.

[0009] In a possible implementation, the condensing mechanism includes a condenser and a condenser tube. The liquid in the condenser is connected to the condenser tube by a water outlet pipe. The water outlet of the condenser tube is connected to the condenser. The condenser tube is serpentine.

[0010] In a possible implementation scheme, a first pumping mechanism is provided between the water inlet tank and the particle filter column, and the water in the water inlet tank is pumped to the particle filter column by the first pumping mechanism; a second pumping mechanism is provided between the water outlet tank and the membrane distiller, and the water in the water outlet tank is pumped to the membrane distiller by the second pumping mechanism.

[0011] In a possible embodiment, the granular filter material includes any one of activated alumina, activated carbon, zeolite, anthracite and quartz sand.

[0012] In a possible implementation scheme, the liquid inlet of the water inlet tank is connected to a wastewater delivery pipeline, and a lift pump and a water inlet valve are provided on the wastewater delivery pipeline.

[0013] In a possible implementation scheme, the water inlet tank and the particle filter column are connected via a connecting pipe, and the connecting pipe is provided with a water stop valve.

[0014] In a second aspect, the present application provides a process for treating saline wastewater by membrane distillation, which uses the device for treating saline wastewater by membrane distillation according to the first aspect to treat saline wastewater, comprising the following steps: The salt-containing wastewater in the water inlet tank is heated by the heater, enters the particle filter column from the water inlet of the particle filter column, is filtered by the particle filter material in the particle filter column, and enters the water inlet side of the membrane distiller from the water outlet of the particle filter column. After being treated by the membrane component, it enters the water outlet side and is discharged to the water outlet tank through the second outlet; the wastewater is cooled by the condensation mechanism in the water outlet tank and then enters the water outlet side from the second inlet; the wastewater on the water inlet side is discharged to the water inlet tank through the first outlet.

[0015] In a possible implementation, the particle filter material is activated alumina, which is obtained by impregnating and modifying the activated alumina with a sodium hydroxide solution. The mass ratio of the activated alumina to the sodium hydroxide solution is 1:3, and the concentration of the sodium hydroxide solution is 20 g / L.

[0016] The embodiments of the present application have at least the following beneficial effects: The present application provides an apparatus and process for treating saline wastewater using membrane distillation. The particle filter material in the particle filter column is obtained after modification with sodium hydroxide solution. The modification makes the particle filter material have a larger retention space and surface area, providing more nucleation sites for multiphase crystallization. At the same time, the continuous filtration formed by the particle filter column in which water enters from the bottom and discharges from the top extends the residence time of the saline wastewater in the particle filter column, and impurities in the wastewater are captured in time and effectively. The amount of scale deposited on the surface of the membrane component of the membrane distiller is reduced, and the water quality of the effluent is effectively improved in conjunction with the membrane distillation process. It can effectively improve the effluent quality of the membrane distiller, reduce the frequency of membrane cleaning and replacement, and has the advantages of low operating cost, low energy consumption, and easy maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The test results of pore size and pore volume of the activated alumina modified with sodium hydroxide solution in Example 1, Comparative Examples 3 to 6, Comparative Examples 8 to 15 of the present application and the activated alumina not modified with sodium hydroxide solution in Comparative Example 7; Figure 2 The results of the sodium content test on the surface of the filter material of Example 1, Comparative Examples 3 to 6, Comparative Examples 8 to 15 modified with sodium hydroxide solution and Comparative Example 7 not modified with sodium hydroxide solution are shown; Figure 3 This is a SEM image of the activated alumina modified by sodium hydroxide solution in Example 1 and Comparative Examples 3 to 6 of the present application; Figure 4 The results are graphs of the water outlet flux of the membrane distiller of Example 1 of the present application and Comparative Examples 1-2 and the conductivity of the treated wastewater; Figure 5 It is a schematic diagram of a device for treating saline wastewater in a specific embodiment of the present application.

[0019] Icons: 10-device for treating saline wastewater; 11-particle filter column; 111-water inlet; 112-water outlet; 12-water inlet tank; 121-heater; 13-membrane distiller; 131-membrane assembly; 132-water inlet side; 133-water outlet side; 134-first inlet; 135-first outlet; 136-second inlet; 137-second outlet; 14-water outlet tank; 141-condensation mechanism; 1411-condensation pipe; 142-temperature detector; 143-conductivity detector; 15-water collecting tank; 16-overflow pipe; 171-first pumping mechanism; 172-second pumping mechanism; 173-wastewater delivery pipeline; 174-lifting pump; 175-water inlet valve; 176-water stop valve; 177-water production valve; 18-pressure sensor. DETAILED DESCRIPTION

[0020] To make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all of the embodiments. The components of the embodiment of the present application described and shown in the accompanying drawings here can be arranged and designed with various configurations. Those who do not specify specific conditions in the embodiment are carried out according to the conditions recommended by normal conditions or manufacturers. Those who do not specify manufacturers for reagents used or instruments are conventional products that can be obtained by commercial purchase.

[0021] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a connection between the two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0022] The following is a detailed description of the device and process for treating saline wastewater using membrane distillation in this application: In the first aspect, the present application provides a device 10 for treating saline wastewater using membrane distillation, referring to Figure 5 , which includes a particle filter column 11, an inlet water tank 12, a membrane distiller 13 and an outlet water tank 14.

[0023] The particle filter column 11 has a particle filter material, which is obtained by modification with a sodium hydroxide solution; the particle filter column 11 includes a water inlet 111 and a water outlet 112, wherein the water inlet 111 is arranged at the bottom of the particle filter column 11, and the water outlet 111 is arranged at the top of the particle filter column 11. The continuous filtration formed by the particle filter column 11 in which water enters from the bottom and exits from the top prolongs the residence time of the salt-containing wastewater in the particle filter column 11, and can timely and effectively capture impurities in the wastewater. The particle filter material in the particle filter column 11 is obtained by modification with a sodium hydroxide solution, and the modification makes the particle filter material have a larger interception space and surface area, providing more nucleation sites for multiphase crystallization.

[0024] Optionally, the particle filter material includes any one of activated alumina, activated carbon, zeolite, anthracite and quartz sand. Optionally, the particle size of the particle filter material is 3 to 6 mm. In the modification method of the particle filter material impregnation, the particle filter material is washed and dried with deionized water, and then impregnated in a sodium hydroxide solution for modification. After impregnation, the particle filter material needs to be washed and dried with deionized water to finally complete the modification.

[0025] The water inlet tank 12 has a heater 121 for heating the saline wastewater, and the saline wastewater in the water inlet tank 12 can enter the particle filter column 11 through the water inlet 111 of the particle filter column 11. Exemplarily, a first pumping mechanism 171 is provided between the water inlet tank 12 and the particle filter column 11, and the water in the water inlet tank 12 is pumped to the particle filter column 11 by the first pumping mechanism 171. Optionally, the first pumping mechanism 171 is a gear pump.

[0026] Furthermore, the liquid inlet of the water inlet tank 12 is connected to a wastewater delivery pipe 173, and a lifting pump 174 and a water inlet valve 175 are provided on the wastewater delivery pipe 173. The lifting pump 174 is used to lift the saline wastewater, and the water inlet valve 175 is used to control the flow rate and flow rate of the saline wastewater in the wastewater delivery pipe 173 entering the water inlet tank 12. Furthermore, the water inlet tank 12 and the particle filter column 11 are connected through a connecting pipe, and a water stop valve 176 is provided on the connecting pipe. The water stop valve 176 can control the water flow to facilitate the maintenance of the particle filter column 11.

[0027] Among them, the membrane distiller 13 has a membrane assembly 131, and the membrane assembly 131 separates the membrane distiller 13 into an inlet side 132 and an outlet side 133. The membrane distiller 13 has a first inlet 134 and a first outlet 135 arranged on the inlet side 132, and a second inlet 136 and a second outlet 137 arranged on the outlet side 133. The first inlet 134 is connected to the outlet 112 of the particle filter column 11, and the first outlet 135 is connected to the inlet water tank 12.

[0028] Exemplarily, the membrane assembly 131 is detachably connected to the main body of the membrane distiller 13, and the membrane assembly 131 is installed on the main body of the membrane distiller 13. Optionally, the membrane assembly 131 of the membrane distiller 13 adopts an organic membrane or an inorganic membrane; when an organic membrane is adopted, it can be polyethersulfone (PES), polysulfone (PS), polyethylene (PE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polypropylene (PP), polyacrylonitrile (PAN) or cellulose acetate (CA); when an inorganic membrane is adopted, it can be aluminum oxide (Al2O3), zirconium oxide (ZrO), titanium oxide (TiO2) or silicon oxide (SiO2).

[0029] A condensing mechanism 141 is provided in the water outlet tank 14, and the second outlet 137 is communicated with the inlet of the water outlet tank 14, and the outlet of the water outlet tank 14 is communicated with the second inlet 136. A second pumping mechanism 172 is provided between the water outlet tank 14 and the membrane distiller 13, and the water in the water outlet tank 14 is pumped to the membrane distiller 13 by the second pumping mechanism 172. Optionally, the second pumping mechanism 172 is a gear pump. In addition, a water stop valve 176 is provided in the connecting pipe section between the water outlet side 133 of the membrane distiller 13 and the water outlet tank 14, so as to control the liquid transportation between the membrane distiller 13 and the water outlet tank 14.

[0030] After being filtered by the particle filter material in the particle filter column 11, the salt-containing wastewater enters the water inlet side 132 of the membrane distiller 13 through the first inlet 134, enters the water outlet side 133 after being processed by the membrane assembly 131, and is discharged to the water outlet tank 14 through the second outlet 137. A part of the water on the water inlet side 132 is discharged from the first outlet 135 to the water inlet tank 12 to form a cycle. Among them, the particle filter column 11 is connected to the first inlet 134 of the membrane distiller 13 through the first pipe, and the first outlet 135 of the membrane distiller 13 is connected to the water inlet tank 12 through the second pipe. The first pipe and the second pipe are provided with a temperature sensor and / or a pressure sensor 18, and the temperature sensor can monitor the temperature of the water inlet side 132 of the membrane distiller 13 in real time. The pressure sensor 18 can monitor the pressure change of the salt-containing wastewater passing through the membrane distiller 13.

[0031] The water outlet tank 14 is provided with a condensing mechanism 141, which can cool and condense the water, and then enter the water outlet side 133 of the membrane distiller 13 from the second inlet 136 to form a cycle. The membrane distillation membrane is powered by the water vapor pressure difference between the water inlet side 132 and the water outlet side 133. The water on the water inlet side 132 is saline wastewater heated by the heater 121 in the water inlet tank 12. Part of the water on the water outlet side 133 is water condensed from the water outlet tank 14. The water vapor passes through the membrane pores of the membrane assembly 131 to the water outlet side 133. The membrane assembly 131 has extremely strong hydrophobicity and can achieve a 100% interception rate of inorganic and non-volatile organic matter. Exemplarily, the condensing mechanism 141 includes a condenser and a condenser tube. The liquid in the condenser is connected to the condenser tube by the water outlet tube. The water outlet of the condenser tube is connected to the condenser. The condenser tube is serpentine.

[0032] The continuous filtration formed by the particle filter column 11 with water entering from the bottom and discharging from the top extends the residence time of the salt-containing wastewater in the particle filter column 11, and impurities in the wastewater are captured timely and effectively. The amount of scale deposited on the surface of the membrane assembly 131 passing through the membrane distiller 13 is reduced, and the water quality of the effluent is effectively improved in conjunction with the membrane distillation process. It can effectively improve the effluent quality of the membrane distiller 13, reduce the frequency of membrane cleaning and replacement, and has the advantages of low operating cost, low energy consumption, and easy maintenance. Among them, a temperature detector 142 and / or a conductivity detector 143 are provided in the outlet water tank 14. The condenser maintains the outlet water temperature, and the temperature detector 142 and the conductivity detector 143 can respectively monitor the water temperature and water quality parameters to ensure the outlet water quality.

[0033] Furthermore, the device 10 for treating saline wastewater also includes a water collecting tank 15, and the outlet water tank 14 and the water collecting tank 15 are connected by an overflow pipe 16, and the overflow pipe 16 is located at one end of the outlet water tank 14 and the pipe opening is higher than the pipe opening at one end of the water collecting tank 15. The water vapor entering the outlet side 133 of the membrane distiller 13 is rapidly liquefied when encountering low temperature and flows to the outlet water tank 14, and the water volume of the outlet water tank 14 increases and flows to the water collecting tank through the overflow pipe 16, thereby ensuring that the water level of the outlet water tank 14 is constant. Among them, a water production valve 177 is provided on the overflow pipe 16 to regulate the water output. In addition, the outer walls of the inlet water tank 12, the particle filter column 11, the membrane distiller 13, the outlet water tank 14 and the connecting pipe section between the two devices are all provided with an insulation layer for heat preservation.

[0034] In a second aspect, the present application provides a process for treating saline wastewater by membrane distillation, which uses the device 10 for treating saline wastewater by membrane distillation according to the first aspect to treat saline wastewater, comprising the following steps: The salt-containing wastewater in the water inlet tank 12 is heated by the heater 121, enters the particle filter column 11 from the water inlet 111 of the particle filter column 11, is filtered by the particle filter material in the particle filter column 11, and enters the water inlet side 132 of the membrane distiller 13 from the water outlet 112 of the particle filter column 11, enters the water outlet side 133 after being treated by the membrane assembly 131, and is discharged to the water outlet tank 14 through the second outlet 137; the wastewater is cooled by the condensation mechanism 141 in the water outlet tank 14 and then enters the water outlet side 133 from the second inlet 136; the wastewater on the water inlet side 132 is discharged to the water inlet tank 12 through the first outlet 135.

[0035] In one embodiment, the particle filter material is activated alumina, which is obtained by impregnating and modifying the activated alumina with a sodium hydroxide solution. The mass ratio of the activated alumina to the sodium hydroxide solution is 1:3, and the concentration of the sodium hydroxide solution is 20 g / L.

[0036] The inventors of the present application found in their research that when the mass ratio of activated alumina to sodium hydroxide solution is 1:3 and the concentration of the sodium hydroxide solution is 20 g / L, the particle filter material that has been immersed for 24 hours has the best effect when used for treating saline wastewater.

[0037] The following is a further detailed description of the device and process for treating saline wastewater by membrane distillation according to the present application in conjunction with the embodiments. Example

[0038] This embodiment provides a device for treating saline wastewater by membrane distillation, which includes a particle filter column 11, an inlet water tank 12, a membrane distiller 13, an outlet water tank 14 and a water collecting tank 15.

[0039] The liquid inlet of the water inlet tank 12 is connected to a wastewater delivery pipe 173, and a lift pump 174 and a water inlet valve 175 are provided on the wastewater delivery pipe 173. The water inlet tank 12 has a heater 121 for heating the saline wastewater. A first pumping mechanism 171 is provided between the water inlet tank 12 and the particle filter column 11, and the water in the water inlet tank 12 is pumped to the particle filter column 11 by the first pumping mechanism 171.

[0040] The particle filter column 11 has a particle filter material, which is obtained after being modified by a sodium hydroxide solution; the particle filter column 11 includes a water inlet 111 and a water outlet 112, the water inlet 111 is arranged at the bottom end of the particle filter column 11, and the water inlet 111 is arranged at the top end of the particle filter column 11. The water inlet tank 12 and the particle filter column 11 are connected by a connecting pipe, and the connecting pipe is provided with a water stop valve 176. The salt-containing wastewater in the water inlet tank 12 can enter the particle filter column 11 through the water inlet 111 of the particle filter column 11.

[0041] The membrane distiller 13 has a membrane assembly 131 therein, which separates the membrane distiller 13 into an inlet side 132 and an outlet side 133. The membrane distiller 13 has a first inlet 134 and a first outlet 135 arranged on the inlet side 132, and a second inlet 136 and a second outlet 137 arranged on the outlet side 133. The first inlet 134 is connected to the outlet 112 of the particle filter column 11, and the first outlet 135 is connected to the inlet water tank 12.

[0042] The outlet water tank 14 is provided with a condensation mechanism 141 and a conductivity detector 143, the second outlet 137 is connected to the inlet of the outlet water tank 14, and the outlet of the outlet water tank 14 is connected to the second inlet 136. A second pumping mechanism 172 is provided between the outlet water tank 14 and the membrane distiller 13, and the water in the outlet water tank 14 is pumped to the membrane distiller 13 by the second pumping mechanism 172. In addition, a water stop valve 176 is provided on the connecting pipe section between the outlet side 133 of the membrane distiller 13 and the outlet water tank 14.

[0043] The outlet tank 14 and the water collecting tank 15 are connected by an overflow pipe 16. The pipe opening of the overflow pipe 16 at one end of the outlet tank 14 is higher than the pipe opening at one end of the water collecting tank 15. A water production valve 177 is provided on the overflow pipe 16 to adjust the water output.

[0044] This embodiment also provides a process for treating saline wastewater using membrane distillation, which is carried out using the above-mentioned device for treating saline wastewater using membrane distillation.

[0045] In this embodiment, calcium sulfate is used to simulate saline wastewater. The saline wastewater is simulated with calcium sulfate at a concentration of 25 mmol / L. The particle filter material in the particle filter column 11 is activated alumina, and the particle size of the activated alumina is 4 mm; a polytetrafluoroethylene membrane assembly 131 is placed in the membrane distiller 13, and the effective area of ​​the membrane is 2×15=30 cm 2 The activated alumina was obtained by being impregnated and modified in a sodium hydroxide solution for 24 hours, the mass ratio of the activated alumina to the sodium hydroxide solution was 1:3, and the concentration of the sodium hydroxide solution was 20 g / L.

[0046] The saline wastewater is added to the inlet water tank 12 by the lift pump 174. The saline solution is heated to a set temperature of 70°C by the heater 121 in the inlet water tank 12 and pumped to the water inlet 111 at the bottom of the particle filter column 11 by the first pumping mechanism 171. The designed flow rate is 180 cm 3 / min. After the wastewater is treated by the particle filter column 11, it enters the water inlet side 132 of the membrane distiller 13 through the water outlet 112 at the top of the particle filter column 11 through the first inlet 134. A portion of the water flows from the first outlet 135 of the water inlet side 132 to the water inlet tank 12 and then returns to the water inlet tank 12. Another portion of the water is treated by the membrane assembly 131 and flows from the second outlet 137 to the water outlet tank 14. The water in the water outlet tank 14 is cooled to a set temperature of 20°C by the condensing mechanism 141 and is pumped again to the membrane distillation water outlet side 133 by the second pumping mechanism 172. The design flow rate of the water outlet side 133 of the membrane distiller 13 is also 180 cm 3 / min. The membrane distiller 13 uses the water vapor pressure difference caused by the temperature difference between the water inlet side 132 and the water outlet side 133 as the driving force. The water vapor is transmitted from the water inlet side 132 to the water outlet side 133. The water vapor is liquefied at low temperature at the water outlet side 133 to extract pure water from the saline wastewater. The water volume of the outlet water tank 14 increases, the water level exceeds the overflow pipe 16, and the treated water flows to the water collecting tank 15 to be collected.

[0047] Comparative Example 1 This comparative example provides a device for treating saline wastewater, which is different from Example 1 only in that the water inlet 111 of the particle filter column 11 of Comparative Example 1 is connected to the wastewater delivery pipeline 173 via the water inlet valve 175, the water outlet 112 of the particle filter column 11 is connected to the water inlet tank 12, the liquid outlet of the water inlet tank 12 is connected to the first inlet 134 of the membrane distiller 13, and the first outlet 135 of the membrane distiller 13 is also connected to the water inlet tank 12. The saline wastewater in Comparative Example 1 is first treated by the particle filter column 11, then flows into the water inlet tank 12, and then flows out into the membrane distiller 13.

[0048] Comparative Example 2 This comparative example provides a device for treating saline wastewater. The only difference from Example 1 is that Comparative Example 2 removes the particle filter column 11 of Example 1, and the water inlet tank 12 directly supplies saline wastewater to the membrane distiller 13 through the first inlet 134.

[0049] Comparative Example 3~Comparative Example 6 This comparative example provides a process for treating saline wastewater using membrane distillation. The only difference from Example 1 is that the concentrations of the sodium hydroxide solutions used in Comparative Examples 3 to 6 are 5 g / L, 10 g / L, 15 g / L and 25 g / L, respectively.

[0050] Comparative Example 7 This comparative example provides a process for treating saline wastewater using membrane distillation. The only difference from Example 1 is that the particle filter material of Comparative Example 7 is not modified with sodium hydroxide solution.

[0051] Comparative Example 8~Comparative Example 11 This comparative example provides a process for treating saline wastewater using membrane distillation, which is different from Example 1 only in that the mass ratios of activated alumina to sodium hydroxide solution in Comparative Examples 8 to 11 are 1:1, 1:5, 1:7 and 1:10, respectively.

[0052] Comparative Example 12~Comparative Example 15 This comparative example provides a process for treating saline wastewater by membrane distillation. The only difference from Example 1 is that the time for impregnation modification of activated alumina with sodium hydroxide solution is 0.5h, 6h, 12h and 36h respectively. Test Example 1 The pore size and pore volume of the activated alumina modified with sodium hydroxide solution in Example 1, Comparative Examples 3 to 6, Comparative Examples 8 to 15 and the activated alumina not modified with sodium hydroxide solution in Comparative Example 7 were tested, and the sodium content on the filter material surface was tested. The results are as follows: Figure 1 and Figure 2 The activated alumina modified by sodium hydroxide solution in Example 1 and Comparative Example 3 to Comparative Example 6 was observed under an electron scanning microscope, and the SEM results were as follows Figure 3 shown.

[0053] from Figure 1~Figure 3 The results show that the sodium hydroxide solution impregnation changes the microstructure and surface element distribution of the activated alumina particles. With the increase of sodium hydroxide concentration, the pore size (Ps) and pore volume (Pv) of the activated alumina first increase and then decrease (refer to Figure 1 ), the loading amount of Na also increases first and then decreases (refer to Figure 2 By adjusting the proportion and time of NaOH impregnation, the performance of activated alumina is consistent with the change of sodium hydroxide concentration. The activated alumina formed has low porosity and low flaky structure (refer to Figure 3 ) and low Na loading. Figure 1~Figure 3 The results show that the optimal impregnation conditions are 20 g / L sodium hydroxide concentration, 1:3 mass ratio of activated alumina to sodium hydroxide solution, and 24 h impregnation time. When the sodium hydroxide concentration is 20 g / L, the activated alumina has both a low flaky structure and a large pore size and pore volume and low Na loading; when the mass ratio of activated alumina to sodium hydroxide solution is 1:3, it has the highest pore size, pore volume, and low Na loading.

[0054] Test Example 2 The water flux of the membrane distiller 13 of Example 1 and Comparative Examples 1-2 was detected, and the conductivity detected by the conductivity detector 143 was recorded. The results are as follows: Figure 4 As shown in (a) and (b).

[0055] from Figure 4 It can be seen from Figures (a) and (b) that, compared with Comparative Examples 1 and 2, the conductivity of the saline wastewater treated by the device and process for treating saline wastewater by membrane distillation in Example 1 is lower and the normalized flux is higher. The optimal flux is 77% of the initial flux, and the final conductivity is 0.32μS / cm.

[0056] The above are only specific embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A device for treating saline wastewater using membrane distillation, characterized in that: include: A particle filter column, wherein the particle filter column has a particle filter material, and the particle filter material is obtained after being modified by a sodium hydroxide solution; The particle filter column comprises a water inlet and a water outlet, wherein the water inlet is arranged at the bottom end of the particle filter column, and the water outlet is arranged at the top end of the particle filter column; and An inlet water tank, wherein the inlet water tank has a heater for heating saline wastewater, and the saline wastewater in the inlet water tank can enter the particle filter column through the water inlet of the particle filter column; A membrane distiller, wherein the membrane distiller has a membrane assembly therein, the membrane assembly separates the membrane distiller into a water inlet side and a water outlet side, the membrane distiller has a first inlet and a first outlet arranged at the water inlet side and a second inlet and a second outlet arranged at the water outlet side, the first inlet is communicated with the water outlet of the particle filter column, and the first outlet is communicated with the water inlet tank; and A water outlet water tank is provided with a condensing mechanism, the second outlet is communicated with the inlet of the water outlet water tank, and the outlet of the water outlet water tank is communicated with the second inlet.

2. The device for treating saline wastewater by membrane distillation according to claim 1, characterized in that: The water outlet tank is provided with a temperature detector and / or a conductivity detector.

3. The device for treating saline wastewater by membrane distillation according to claim 2, characterized in that: It also includes a water collecting tank, the water outlet tank and the water collecting tank are connected via an overflow pipe, and the overflow pipe is located at one end of the water outlet tank and has a higher pipe opening than that of the water collecting tank.

4. The device for treating saline wastewater by membrane distillation according to any one of claims 1 to 3, characterized in that: The condensing mechanism comprises a condenser and a condensing tube. The liquid in the condenser is connected to the condensing tube via a water outlet pipe. The water outlet of the condensing tube is connected to the condenser. The condensing tube is serpentine.

5. The device for treating saline wastewater by membrane distillation according to any one of claims 1 to 3, characterized in that: A first pumping mechanism is provided between the water inlet tank and the particle filter column, and the water in the water inlet tank is pumped to the particle filter column by the first pumping mechanism; a second pumping mechanism is provided between the water outlet tank and the membrane distiller, and the water in the water outlet tank is pumped to the membrane distiller by the second pumping mechanism.

6. The device for treating saline wastewater by membrane distillation according to any one of claims 1 to 3, characterized in that: The granular filter material includes any one of activated alumina, activated carbon, zeolite, anthracite and quartz sand.

7. The device for treating saline wastewater by membrane distillation according to any one of claims 1 to 3, characterized in that: The liquid inlet of the water inlet tank is connected with a wastewater delivery pipeline, and a lifting pump and a water inlet valve are arranged on the wastewater delivery pipeline.

8. The device for treating saline wastewater by membrane distillation according to any one of claims 1 to 3, characterized in that: The water inlet tank and the particle filter column are connected via a connecting pipe, and the connecting pipe is provided with a water stop valve.

9. A process for treating saline wastewater using membrane distillation, characterized in that: The device for treating saline wastewater by membrane distillation as claimed in any one of claims 1 to 8 is used to treat saline wastewater, comprising the following steps: The salt-containing wastewater in the water inlet tank is heated by the heater, enters the particle filter column from the water inlet of the particle filter column, is filtered by the particle filter material in the particle filter column, and enters the water inlet side of the membrane distiller from the water outlet of the particle filter column, enters the water outlet side after being treated by the membrane assembly, and is discharged to the water outlet tank through the second outlet; the wastewater is cooled by the condensation mechanism in the water outlet tank and then enters the water outlet side from the second inlet; the wastewater on the water inlet side is discharged to the water inlet tank through the first outlet.

10. The process for treating saline wastewater by membrane distillation according to claim 9, characterized in that: The particle filter material is activated alumina, which is obtained by being impregnated and modified by the sodium hydroxide solution. The mass ratio of the activated alumina to the sodium hydroxide solution is 1:3, and the concentration of the sodium hydroxide solution is 20 g / L.

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