CN111689539A - Membrane distillation process for advanced treatment of high-concentration desulfurization wastewater concentrated solution of power plant - Google Patents
Membrane distillation process for advanced treatment of high-concentration desulfurization wastewater concentrated solution of power plant Download PDFInfo
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Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/08—Thin film evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2201/00—Apparatus for treatment of water, waste water or sewage
- C02F2201/002—Construction details of the apparatus
- C02F2201/007—Modular design
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/14—Maintenance of water treatment installations
Abstract
The invention discloses a membrane distillation process for advanced treatment of a high-concentration desulfurization wastewater concentrated solution in a power plant. By regulating and controlling the technological parameters of the feeding temperature, the feeding flow, the feeding conductivity and the cooling water circulation flow in the membrane distillation system, the treatment efficiency of the concentrated solution is obviously improved, the discharge of pollutants is reduced, and the wastewater discharge standard is improved.
Description
Technical Field
The invention relates to the technical field of high-concentration liquid waste treatment control and environment-friendly purification treatment, in particular to a membrane distillation process for advanced treatment of high-concentration desulfurization wastewater concentrated solution in a power plant.
Background
As of 2009, the installed capacity of electric power in China is as high as 8.52 × 108Kw, wherein the specific gravity of the coal-fired power generation is 74.6%. With the continuous expansion of social and economic scales, coal-fired power generation still occupies a leading position in the energy structure of China. The flue gas treatment method mainly adopts a limestone-gypsum wet flue gas desulfurization method, and the desulfurization waste water produced by the method has very complex water quality, is typical of high salt content, high hardness, high chloride ion concentration, strong corrosivity and scalingHigh pollution of waste water. The waste water not only causes environmental pollution and resource waste, but also influences the development of social economy. Therefore, the zero-emission advanced treatment of the high-concentration desulfurization wastewater concentrate in the power plant becomes a hot spot of current research.
A large amount of high-concentration desulfurization wastewater concentrated solution generated in the desulfurization wastewater treatment process of a power plant has the characteristics of high salt content, high hardness, high total solid content, high corrosivity, concentration polarization and the like, membrane components such as reverse osmosis are utilized for reutilization, the treatment effect is poor, and the membrane components are easily and quickly polluted. In the actual treatment process, a part of high-concentration concentrated solution is subjected to precipitation treatment in a physicochemical treatment mode, so that not only is a large amount of medicament waste and secondary pollution generated, but also certain resource waste is caused; and a part of high-concentration concentrated solution is treated in a high-temperature evaporation crystallization mode, so that the energy consumption is high and the economical efficiency is poor.
Therefore, aiming at the research of the zero-emission advanced treatment problem of the high-concentration desulfurization wastewater concentrated solution, the invention adopts the membrane distillation treatment process, utilizes the advantages of high interception rate, small equipment volume, low energy consumption, high separation efficiency and the like of the membrane distillation technology, researches the removal efficiency of different influencing factors on the desulfurization wastewater concentrated solution under pilot scale conditions, and regulates and controls the process parameters to be in the optimal state. At present, the research on the membrane distillation technology in the process of the zero-emission advanced treatment of the high-concentration desulfurization wastewater concentrated solution in a power plant is less, and particularly, the research is related to the research performed under the pilot-scale test condition.
Disclosure of Invention
In order to solve the problems in the background art, the invention aims to provide a membrane distillation process for advanced treatment of a high-concentration desulfurization wastewater concentrated solution in a power plant, which achieves zero emission standard after advanced treatment of the high-concentration desulfurization wastewater concentrated solution through a series of research and regulation settings of process parameters.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a membrane distillation process for advanced treatment of high-concentration desulfurization wastewater concentrated solution in a power plant, which comprises the following steps:
s1, connecting a membrane distillation system, and adding a high-concentration desulfurization wastewater concentrated solution to be treated into a wastewater tank;
s2, setting the distillation process feeding temperature set value of the membrane distillation assembly to be 67-80 ℃, starting a brine pump, and conveying the high-concentration desulfurization wastewater concentrated solution to a heat exchanger through the brine pump for circulating heating;
s3, controlling the feed flow rate of the membrane distillation assembly to be 2-6m through a flow meter3Controlling the feed conductivity of the membrane distillation assembly to be 106.3-159.7ms/cm by a conductivity meter, starting a cooling water circulating pump and a cooling water system when the feed temperature of the membrane distillation assembly reaches over 67 ℃, and controlling the circulating flow of the cooling water to be 2-6m3The membrane distillation component begins to distill to generate strong brine and fresh water, the strong brine returns to the waste water tank, and the fresh water enters the fresh water collecting bottle after being cooled;
and S4, changing the technological parameters of the feeding temperature, the feeding flow rate, the feeding conductivity and the cooling water circulation flow rate in the membrane distillation system, and repeating the steps.
Furthermore, the feeding temperature, the feeding flow rate, the feeding conductivity and the cooling water circulation flow rate are gradually changed in a slowly increasing mode.
Further, the membrane distillation system adopts a continuous operation mode, and the operation time is 10-22 days.
Further, the membrane distillation assemblies are four membrane distillation assemblies connected in series, two membrane distillation assemblies connected in series and two membrane distillation assemblies connected in parallel or four membrane distillation assemblies connected in parallel. The membrane distillation modules are preferably two membrane distillation modules connected in series and in parallel.
Further, the membrane distillation method in the membrane distillation system includes direct contact membrane distillation, reduced pressure or vacuum membrane distillation, air gap membrane distillation, and purge gas membrane distillation.
Compared with the prior art, the invention has the following beneficial effects:
the method has the advantages of simple process, easy control, improved recovery rate of the desulfurization wastewater concentrated solution, reduced actual energy consumption and no secondary pollution. The membrane distillation technology is applied to the zero-emission advanced treatment process of the high-concentration desulfurization wastewater concentrated solution, so that the pollution tolerance capacity of the membrane is improved, membrane pollution to a certain degree is reduced, the service life of a membrane component is prolonged, and the stability and the economy of operation are improved; and the membrane distillation technology does not need membrane pressure difference required by membrane components such as reverse osmosis and the like, so that energy loss in the actual process is reduced, meanwhile, the membrane distillation technology can utilize low-quality heat sources generated by a power plant, and substances are transmitted at a temperature lower than the boiling point of waste liquid, so that resource utilization can be maximized, and the membrane distillation technology is environment-friendly and energy-saving.
The membrane distillation system is used as a desulfurization wastewater zero-discharge treatment process, so that the treatment efficiency of the concentrated solution is improved, the discharge of pollutants is reduced, and the wastewater discharge standard is improved. The experiment result shows that the interception rate is up to 100 percent, the total dissolved solids of the produced water is 3.9-6.5mg/L, and the conductivity of the produced water is 8.6-9.9 us/cm.
Drawings
The invention is described in further detail below with reference to specific embodiments and with reference to the following drawings.
FIG. 1 is a block diagram of a membrane distillation system according to the present invention;
FIG. 2 is a graph of the effect of feed temperature on membrane flux;
FIG. 3 is a graph of the effect of feed flow on membrane flux;
FIG. 4 is a graph of the effect of cooling water circulation flow on membrane flux;
FIG. 5 is a graph of the effect of increasing feed flow and cooling water circulation flow in proportion on membrane flux;
FIG. 6 is a graph of the effect of feed conductivity on membrane flux;
FIG. 7 is an electron micrograph of the initial surface contamination of the film;
FIG. 8 is an electron micrograph of the contamination of the film surface after 1 month of operation;
FIG. 9 is an electron micrograph of the contamination of the film surface after 2 months of operation;
wherein, waste water tank 1, salt water pump 2, heat exchanger 3, flowmeter 4, cooling water circulating pump 5, cooling water system 6, membrane distillation subassembly 7.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description is made with reference to the accompanying drawings and the detailed description.
The structure of the membrane distillation system is shown in figure 1, a high-concentration desulfurization wastewater concentrated solution in a wastewater tank 1 on the left side enters a heat exchanger 3 through a brine pump 2 to be circularly heated, and a flow meter 4, a conductivity meter, a thermometer and a pressure gauge are respectively installed on a pipeline between the heat exchanger and a membrane distillation assembly and used for measuring the flow, the conductivity, the temperature and the pressure of wastewater before entering a membrane distillation assembly 7. And starting a cooling water circulating pump 5 and a cooling water system 6, installing a flow meter 4 on a pipeline between the cooling system and the membrane distillation assembly for measuring the circulating flow of the cooling water, starting the distillation process of the membrane distillation assembly 7 to generate strong brine and fresh water, returning the strong brine to the waste water tank 1, and cooling the fresh water to enter the fresh water collecting bottle.
The membrane distillation process for the advanced treatment of the high-concentration desulfurization wastewater concentrated solution in the power plant comprises the following steps:
s1, connecting a membrane distillation system, and adding a high-concentration desulfurization wastewater concentrated solution to be treated into the wastewater tank, wherein the properties of the high-concentration desulfurization wastewater concentrated solution are shown in Table 1;
TABLE 1
| Index (I) | Numerical value |
| Total hardness mg/L | 28.5-32 |
| Ca2+mg/L | 10.0-11.0 |
| Mg2+mg/L | 2.0-2.19 |
| Conductivity ms/cm | 106.3-159.7 |
| Total chemical oxygen demand mg/L | 720-765 |
| Cl-mg/L | 20000-25200 |
S2, setting the distillation process feeding temperature set value of the membrane distillation assembly to be 67-80 ℃, starting a brine pump, and conveying the high-concentration desulfurization wastewater concentrated solution to a heat exchanger through the brine pump for circulating heating;
s3, controlling the feed flow rate of the membrane distillation assembly to be 2-6m through a flow meter3Controlling the feed conductivity of the membrane distillation assembly to be 106.3-159.7ms/cm by a conductivity meter, starting a cooling water circulating pump and a cooling water system when the feed temperature of the membrane distillation assembly reaches over 67 ℃, and controlling the circulating flow of the cooling water to be 2-6m3The membrane distillation component begins to distill to generate strong brine and fresh water, the strong brine returns to the waste water tank, and the fresh water enters the fresh water collecting bottle after being cooled;
and S4, changing the technological parameters of the feeding temperature, the feeding flow rate, the feeding conductivity and the cooling water circulation flow rate in the membrane distillation system, and repeating the steps.
Wherein, the feeding temperature, the feeding flow, the feeding conductivity and the cooling water circulation flow are gradually changed in a slowly increasing mode. The membrane distillation system adopts a continuous operation mode, and the operation time is 10-22 days.
Wherein, the membrane distillation assembly is four membrane distillation assemblies connected in series, two membrane distillation assemblies connected in parallel in series or four membrane distillation assemblies connected in parallel. The membrane distillation modules are preferably two membrane distillation modules connected in series and in parallel.
The membrane distillation method in the membrane distillation system comprises direct contact type membrane distillation, reduced pressure or vacuum membrane distillation, air gap type membrane distillation and purge gas membrane distillation.
In the test process, the total hardness, calcium ion concentration and magnesium ion concentration in the wastewater are measured by an EDTA titration method (GB/T7477-1987); the conductivity is measured by a conductivity meter method in Water and wastewater monitoring and analyzing methods in China; measuring the chloride ion concentration by inorganic anion chromatography (HJ 84-2016); the chemical oxygen demand was measured by dichromate method (HJ828-2017), and is shown in Table 2.
TABLE 2
| Item | Measurement method |
| Total hardness, calcium, magnesium ion concentration | EDTA titration method (GB/T7477-1987) |
| Electrical conductivity of | Conductivity meter method |
| Concentration of chloride ion | Ion chromatography (HJ 84-2016) |
| Chemical Oxygen Demand (COD) | Dichromate method (HJ828-2017) |
Example 1
Effect of feed temperature on Membrane flux
The flow of circulating cooling water in the membrane distillation system is 4m3H, feed flow 4m3H, this implementationThe effect of feed temperature on membrane distillation flux was investigated. As shown in FIG. 2, the daily water production of the membrane increased from 583.2L/d on the first day to 1154.4L/d as the feed temperature was increased stepwise from 67 ℃ to 81 ℃ over the entire experimental period of 22 days. At days 1 to 6, the feed temperature is increased from 67 ℃ to 67.7 ℃, the daily water yield of the membrane is increased from 583.2L/d to 715.2L/d, and the daily water yield of the membrane is increased faster; from day 7 to day 16, when the feed temperature was increased from 67.7 ℃ to 70.5 ℃, the membrane water production decreased slightly from 715.2L/d to 672L/d, with the temperature interval decreasing slightly with increasing temperature; when the feed temperature is increased from 70.5 ℃ to 81 ℃ from the day 17 to the day 22, the daily water yield of the membrane is increased from 672L/d to 1154L/d, and the increase amplitude is larger, which shows that the temperature in the temperature interval has more obvious influence on the membrane flux.
Example 2
Effect of feed flow on Membrane flux
As shown in fig. 3, this example investigated the effect of feed flow rate on membrane distillation flux under otherwise identical experimental conditions. The whole experimental period lasted 16 days, with feed flow from 3.1m on day one to day 43The per hour is increased to 4.1m3At the time of/h, the daily water yield of the membrane is increased from 657.6L/d to 955.2L/d. As the experiment continued, the feed flow rate remained stable and the membrane daily water production decreased slightly from day 6 to day 10. On days 7 to 16, the feed rate was increased to 6m3At/h, the membrane water yield increased from 948L/d to 1108.8L/d. From the analysis of the whole experimental operation process, the membrane flux of the membrane distillation system is continuously increased along with the continuous increase of the feed circulation flow, which shows that the feed circulation flow and the membrane flux have obvious positive correlation.
Example 3
Influence of cooling water circulation flow on membrane flux
As shown in fig. 4, this example investigated the effect of the cooling water circulation flow rate on the membrane flux under the same other experimental conditions. When the cooling water circulation volume is 2.1m from the first day3Increase to 4m on day 63At the time of/h, the daily water yield of the membrane is increased from 602.4L/d to 775.2L/d. On days 5 to 516 days period, with cooling water circulation from 4m3The/h is increased to 5.9m3At/h, the water yield of the membrane increased from 775.2L/d to 852L/d. Therefore, in the initial stage of the experiment, the membrane flux is rapidly improved along with the increase of the cooling water circulation flow, because under the condition that the material of the heat transfer plate and the air gap condition are fixed, the increase of the cooling water circulation flow can reduce the phenomenon of membrane cold side temperature difference polarization, the flow rate is larger, the heat of the heat transfer plate is taken away by the cooling water more, the condensation effect of the heat transfer plate is better, and the membrane flux is increased.
Example 4
Influence of increase of feed flow and cooling water circulation flow on membrane flux
As shown in fig. 5, the effect of increasing the feed flow rate and the cooling water circulation flow rate in the same ratio on the membrane distillation flux was investigated under the same other experimental conditions. According to the experimental results, it is shown that the same ratio is obtained from 2m with the feed flow and the cooling water circulation flow3Increase of h to 6m3At the time of/h, the daily water yield of the membrane is increased from 640.8L/d to 1468.8L/d, the increase amplitude of the daily water yield of the membrane is large, and the increase and change trend of the membrane flux is in obvious positive correlation with the increase and change trend of the same-ratio acceleration, which shows that the same-ratio increase of the feed flow and the cooling water circulation flow has obvious positive influence on the increase of the membrane flux.
Example 5
Effect of feed concentration on Membrane flux
As shown in fig. 6, this example investigated the effect of feed concentration on membrane distillation flux under otherwise identical experimental conditions. The results show that when the conductivity of the feed solution is increased from 122.0ms/cm to 215.0ms/cm, the daily water production of the membrane is increased from 955.2L/d to 988.8L/d, the membrane flux is maintained at a relatively stable level, and the membrane flux does not change greatly, which indicates that the increase in the feed concentration under the experimental conditions does not cause a significant change in the membrane flux. It can be seen that the membrane distillation system has good operation effect on the concentrated solution of high-concentration desulfurization waste water when the conductivity of the feed is in the range of 122.0ms/cm to 215.0 ms/cm.
Example 6
Variation of membrane distillation flux by connecting membrane distillation modules in series or parallel
As shown in table 3, this example investigated the effect of different membrane distillation module connections on membrane distillation flux. The results show that different membrane module connections have different effects on membrane flux under otherwise identical experimental conditions. In the mode of serially connecting the membrane modules, the membrane modules can better utilize heat energy, and the loss of the heat energy is reduced to the maximum extent, but the investment of a membrane distillation system is higher. When the membrane modules are connected in a parallel mode, the membrane flux reaches the maximum value, and the water yield reaches 1632L/h, compared with the water yield of the membrane modules in a series mode, the water yield is improved by 456-552L/h, but the energy consumption is improved by nearly 4 times. Meanwhile, compared with the connection mode of the full-series or full-parallel membrane modules, the mixed and series water yield is between the two membrane modules, when the combination mode of the membrane modules is a combination mode combining two series and two parallel, the water yield is improved by 264-88L/h compared with the full-series, and the water yield is reduced by 264L/h compared with the full-parallel. Therefore, from the angle analysis of the manufacturing cost of the membrane distillation system and the actual long-term energy loss, the reasonable connection mode of the parallel-series membrane modules has higher advantageous performance in the aspects of improving the water production efficiency of the membrane distillation system, saving energy and reducing consumption, and has more outstanding economic performance in the actual application process.
TABLE 3
Example 7
In this example, the feed flow rate and the cooling water circulation flow rate are both 4m3The reason for the formation of membrane fouling and the corresponding membrane cleaning method were investigated under conditions of feed temperature of 72.0 + -3 deg.C and feed conductivity in the range of 106.3-159.7 ms/cm. As shown in fig. 7, 8 and 9, after the operation time of the distillation membrane is 0 day, 1 month and 2 months, the membrane surface of the membrane module after dissection can be scanned by an electron microscope, and the pollution of the membrane module is continuously increased along with the increase of the operation time of the membrane distillation system. Further, by analyzing the substance adhered to the surface of the film by energy spectrum element analysis, the analysis result is revealedThe total content of chlorine and sodium is 70.31%, the content of oxygen is 10.73%, the content of iron is 8.35%, the content of sulfur is 7.5%, the total content of calcium and magnesium is only 0.50%, and the content of the remaining elements is 2.61%. The above analysis results show that the scale or crystal mass formed on the anatomical surface of the membrane module mainly contains sodium chloride and then contains iron. Therefore, in the membrane fouling cleaning method, it is necessary to perform regular acid washing in addition to the conventional pure water rinsing. The recovery rate of the membrane flux after the clean water washing is up to 99%, and the recovery rate of the membrane flux after the acid washing is close to 100%, which shows that the combined mode of the clean water washing and the acid washing has good efficiency for removing the membrane pollution, the washing cost is low, and the economic performance is higher.
The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.
Claims (6)
1. A membrane distillation process for advanced treatment of high-concentration desulfurization wastewater concentrated solution in a power plant is characterized by comprising the following steps:
s1, connecting a membrane distillation system, and adding a high-concentration desulfurization wastewater concentrated solution to be treated into a wastewater tank;
s2, setting the distillation process feeding temperature set value of the membrane distillation assembly to be 67-80 ℃, starting a brine pump, and conveying the high-concentration desulfurization wastewater concentrated solution to a heat exchanger through the brine pump for circulating heating;
s3, controlling the feed flow rate of the membrane distillation assembly to be 2-6m through a flow meter3Controlling the feed conductivity of the membrane distillation assembly to be 106.3-159.7ms/cm by a conductivity meter, starting a cooling water circulating pump and a cooling water system when the feed temperature of the membrane distillation assembly reaches over 67 ℃, and controlling the circulating flow of the cooling water to be 2-6m3The membrane distillation component begins to distill to generate strong brine and fresh water, the strong brine returns to the waste water tank, and the fresh water enters the fresh water collecting bottle after being cooled;
and S4, changing the technological parameters of the feeding temperature, the feeding flow rate, the feeding conductivity and the cooling water circulation flow rate in the membrane distillation system, and repeating the steps.
2. The membrane distillation process for the advanced treatment of high concentration desulfurization wastewater concentrate of a power plant as claimed in claim 1, characterized in that the feeding temperature, the feeding flow rate, the feeding conductivity and the cooling water circulation flow rate are all gradually changed in a slowly increasing manner.
3. The membrane distillation process for the advanced treatment of high concentration desulfurization wastewater concentrate of power plant as claimed in claim 2, characterized in that the membrane distillation system adopts a continuous operation mode, and the operation time is 10-22 days.
4. The membrane distillation process for the advanced treatment of high concentration desulfurization wastewater concentrates of power plants according to claim 1, characterized in that the membrane distillation modules are four membrane distillation modules in series, two membrane distillation modules in parallel in series or four membrane distillation modules in parallel.
5. The membrane distillation process for the advanced treatment of high-concentration desulfurization wastewater concentrate of a power plant according to claim 4, characterized in that the membrane distillation assembly comprises two membrane distillation assemblies connected in series and connected in parallel.
6. The membrane distillation process for the advanced treatment of high concentration desulfurization wastewater concentrates of power plants according to claim 1, characterized in that the membrane distillation method in the membrane distillation system comprises direct contact membrane distillation, reduced pressure or vacuum membrane distillation, air gap membrane distillation, purge gas membrane distillation.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114262111A (en) * | 2021-12-27 | 2022-04-01 | 北京华源泰盟节能设备有限公司 | Softened sewage treatment system of heat exchange station |
| CN114715976A (en) * | 2022-04-18 | 2022-07-08 | 浙江大学 | Direct contact type membrane distillation device suitable for pure water preparation and pure water preparation method |
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| JP2000325949A (en) * | 1999-05-25 | 2000-11-28 | Ebara Corp | Apparatus for salt-to-fresh water distillation |
| CN105254101A (en) * | 2015-10-29 | 2016-01-20 | 中国能建集团装备有限公司南京技术中心 | Desulfurization waste water zero-discharging treatment technology for coal-fired power plants |
| CN204981458U (en) * | 2015-08-20 | 2016-01-20 | 北京中电加美环保科技有限公司 | A membrane distillation system that is used for concentration of desulfurization waste water to handle |
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| JP2000325949A (en) * | 1999-05-25 | 2000-11-28 | Ebara Corp | Apparatus for salt-to-fresh water distillation |
| CN204981458U (en) * | 2015-08-20 | 2016-01-20 | 北京中电加美环保科技有限公司 | A membrane distillation system that is used for concentration of desulfurization waste water to handle |
| CN105254101A (en) * | 2015-10-29 | 2016-01-20 | 中国能建集团装备有限公司南京技术中心 | Desulfurization waste water zero-discharging treatment technology for coal-fired power plants |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114262111A (en) * | 2021-12-27 | 2022-04-01 | 北京华源泰盟节能设备有限公司 | Softened sewage treatment system of heat exchange station |
| CN114715976A (en) * | 2022-04-18 | 2022-07-08 | 浙江大学 | Direct contact type membrane distillation device suitable for pure water preparation and pure water preparation method |
| CN114715976B (en) * | 2022-04-18 | 2023-01-24 | 浙江大学 | Direct contact type membrane distillation device suitable for pure water preparation and pure water preparation method |
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