A multi-functional complementary vacuum membrane distillation wastewater treatment system and method

Abstract

A kind of multi-energy complementary vacuum membrane distillation wastewater treatment system and method, belong to energy-saving and environmental protection field.The system includes solar heat collector, middle-deep layer geothermal well, vapor compression heat pump, vacuum membrane assembly, circulating pump, heat exchanger, vacuum pump and other equipment.Its characterized in that: with liquid water as working substance, first sequentially through the middle-deep layer geothermal well group buried in underground 1500m below, vacuum membrane distillation secondary steam, vapor compression heat pump and solar heat collection system gradually improve heat, then through heat exchanger heat transfer to the industrial wastewater to be treated, so that it reaches the required temperature, using circulating pump to fill vacuum membrane assembly, under negative pressure environment, through vacuum membrane distillation process purification separation, the produced secondary steam passes through heat exchanger and transfers sensible heat and latent heat to liquid working substance water to condense and collect, the produced concentrated liquid returns to water tank to continue circulating concentration, after reaching the required concentration, recycling.The invention maximizes the recycling of geothermal energy, solar energy and secondary steam heat energy, meets the energy demand in the process of vacuum membrane distillation wastewater treatment through multi-energy complementation, has the advantages of high energy utilization efficiency, low operating cost, strong operating stability, etc., suitable for industrial heating, building heating, ventilation and air conditioning and other fields.

Description

Technical Field

[0001] This invention relates to a multi-energy complementary vacuum membrane distillation wastewater treatment system and method, belonging to the field of energy conservation and environmental protection. Background Technology

[0002] Vacuum membrane distillation is a newly emerging separation technology that has been widely applied in industrial wastewater treatment, seawater desalination, traditional Chinese medicine concentration, and the food industry. A vacuum membrane distillation system mainly consists of a vacuum membrane module, a circulating pump, a feed tank, a condensate tank, and a vacuum pump. The vacuum membrane module is composed of multiple hollow fiber membrane tubes, each made of hydrophobic microporous polytetrafluoroethylene (PTFE). Driven by the circulating pump, the feed solution in the feed tank fills the hot side of the vacuum membrane module, while the vacuum pump creates a negative pressure environment on the cold side. Driven by the vapor pressure difference across the hydrophobic membrane, water molecules in the solution on the hot side of the membrane evaporate and pass through the membrane pores to the cold side, where they are finally condensed in the condenser, thus separating the feed solution into a concentrate and fresh water. However, due to factors such as membrane fouling, temperature and concentration polarization, and the lack of latent heat recovery devices, existing vacuum membrane distillation systems generally suffer from poor thermodynamic performance and low energy efficiency, thus limiting the industrial application of vacuum membrane distillation technology.

[0003] Renewable energy refers to naturally occurring, continuously renewable, and sustainably usable resources. These primarily include solar energy, geothermal energy, wind energy, hydropower, biomass energy, and ocean energy, which are abundant and widely accessible. Solar energy is the most common renewable energy source, boasting advantages such as being clean, harmless, inexhaustible, and possessing enormous energy reserves. It primarily collects and utilizes solar radiation through photothermal and photovoltaic conversions to meet various needs such as heating and power generation, offering a very broad application prospect. Geothermal energy is natural heat energy extracted from the Earth's lava. It is also a clean and renewable energy source, possessing advantages such as large reserves, wide distribution, green and low-carbon characteristics, strong applicability, and good stability. Especially deep geothermal energy, through the installation of sealed metal heat exchangers in underground boreholes, utilizes the circulating flow of the medium within the heat exchanger to extract heat energy from deep underground, which is then used to meet human energy needs for heating, hot water, and cooling through high-efficiency heat pump units and other equipment. Furthermore, this technology has no impact on the natural environment, including groundwater layers and soil, offering advantages of environmental friendliness and sustainability.

[0004] Currently, although solar energy and medium-deep geothermal technology have been gradually applied in my country and are widely used in the HVAC field, research on their application in industrial wastewater treatment is limited, especially regarding vacuum membrane distillation processes, which are currently nonexistent. Therefore, coupling solar energy and medium-deep geothermal technology to efficiently and cost-effectively meet the energy requirements of vacuum membrane distillation systems for treating industrial wastewater is of significant value and importance for the industrial application of vacuum membrane distillation technology. Summary of the Invention

[0005] This invention proposes a multi-energy complementary vacuum membrane distillation wastewater treatment system and method with low energy consumption and high stability.

[0006] A multi-energy complementary vacuum membrane distillation wastewater treatment system, characterized in that it mainly includes: a group of medium-deep geothermal wells, a first control valve, a second control valve, a third control valve, a fourth control valve, a fifth control valve, a sixth control valve, a vapor compression heat pump, a first water tank, a second water tank, a third water tank, a first circulating pump, a second circulating pump, a solar collector, a first heat exchanger, a second heat exchanger, a vacuum membrane assembly, and a vacuum pump. The vapor compression heat pump consists of a compressor, an evaporator, a condenser, and a throttling valve. The outlet of the medium-deep geothermal well group is connected to the cold-side inlet of the second heat exchanger via a first control valve. The cold-side outlet of the second heat exchanger is connected to the hot-side inlet of the evaporator in the vapor compression heat pump. The hot-side outlet of the evaporator is connected to the inlet of the medium-deep geothermal well group via a second control valve. The cold-side outlet of the evaporator is connected to the compressor inlet, the compressor outlet is connected to the hot-side inlet of the condenser, and the hot-side outlet of the condenser is connected to the cold-side inlet of the evaporator via a throttling valve. The outlet of the first water tank is connected to the inlet of the first circulating pump via a fourth control valve, and the outlet of the first circulating pump is connected to the cold-side inlet of the condenser. The condenser's cold-side outlet is connected to the solar collector's inlet via a third control valve. The solar collector's outlet is connected to the first heat exchanger's hot-side inlet, and the first heat exchanger's hot-side outlet is connected to the first water tank's inlet. The second water tank's outlet is connected to the second circulating pump's inlet via a fifth control valve. The second circulating pump's outlet is connected to the first heat exchanger's cold-side inlet, and the first heat exchanger's cold-side outlet is connected to the vacuum membrane module's tube-side inlet. The vacuum membrane module's tube-side outlet is connected to the second water tank's inlet. The vacuum membrane module's shell-side outlet is connected to the second heat exchanger's hot-side inlet. The second heat exchanger's hot-side outlet is connected to the third water tank's inlet via a sixth control valve, and the third water tank's outlet is connected to the vacuum pump.

[0007] The working method of the solar-powered deep geothermal multi-energy complementary vacuum membrane distillation wastewater treatment system is as follows: the first control valve and the second control valve are opened, and the liquid working fluid water absorbs geothermal energy and is heated by the deep geothermal well group. Then it enters the cold side of the second heat exchanger to absorb the waste heat of the steam and is further heated. After being heated twice, the liquid working fluid water enters the hot side of the evaporator in the vapor compression heat pump, releasing heat to the refrigerant circulating working fluid on the cold side of the evaporator, and then returns to the mid-deep geothermal well group to absorb geothermal energy. The refrigerant working fluid absorbs heat and evaporates into steam on the cold side of the evaporator, enters the compressor for compression into high-temperature and high-pressure steam, and then enters the hot side of the condenser to release heat through condensation, becoming a low-temperature and high-pressure liquid working fluid. The low-temperature and high-pressure liquid working fluid then passes through a throttling valve to reduce its pressure into a low-temperature and low-pressure liquid working fluid, and finally enters the cold side of the evaporator to continue absorbing heat and evaporating. When the third control valve, the fourth control valve, and the first circulation pump are opened, the liquid working fluid water in the first water tank enters the cold side of the condenser to absorb heat from the refrigerant working fluid under the drive of the first circulation pump, and then enters the solar collector to absorb heat. The solution is further heated by solar energy, then enters the hot side of the first heat exchanger to release heat, and finally returns to the cold side of the condenser to continue absorbing heat from the refrigerant. The fifth and sixth control valves are opened, and the solution to be treated in the second water tank is sent to the cold side of the first heat exchanger to absorb heat through the second circulation pump. Then, the tube side of the vacuum membrane module is filled, and the vacuum pump is started to create a vacuum, so that the shell side of the vacuum membrane module is under a certain negative pressure. The solution in the tube side of the vacuum membrane module evaporates on the membrane surface and reaches the shell side under the drive of the vapor pressure difference on both sides of the membrane. The high-temperature vapor enters the hot side of the second heat exchanger through the shell side outlet of the vacuum membrane module, condenses and releases heat, and is finally collected in the third water tank. Meanwhile, the concentrated solution in the tube side of the vacuum membrane module enters the second water tank for further circulation and concentration until the required concentration is reached and then recycled.

[0008] The aforementioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized by the complementary use of solar and geothermal energy as heat sources in the vacuum membrane distillation wastewater treatment process, eliminating the need for external heat sources and cooling water systems. This not only effectively utilizes renewable energy but also efficiently recycles and treats industrial wastewater.

[0009] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that: the medium-deep geothermal well group is composed of multiple medium-deep geothermal wells connected in parallel, each medium-deep geothermal well has a diameter of 100-500 mm and a depth of 1000-4000 m, and uses coaxial sleeves and U-shaped tubes to realize the heat exchange between liquid water and geothermal energy.

[0010] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that: the above-mentioned vapor compression heat pump is composed of a compressor, an evaporator, a condenser and a throttling valve, and the working fluid used is R134a, or R22, or R123.

[0011] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that: the vacuum membrane module is composed of multiple hollow fiber membrane tubes, each membrane tube is made of polytetrafluoroethylene hydrophobic microporous membrane with a pore size of 0.1-0.5 μm.

[0012] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that: the first water tank is used to store softened water, the second water tank is used to store industrial wastewater, and the third water tank is used to store condensed fresh water. Attached Figure Description

[0013] Figure 1 This invention proposes a multi-energy complementary vacuum membrane distillation wastewater treatment system and method.

[0014] The labels in the diagram are as follows: 1. Medium-deep geothermal well group; 2. Medium-deep geothermal well; 3-1 First control valve; 3-2 Second control valve; 3-3 Third control valve; 3-4 Fourth control valve; 3-5 Fifth control valve; 3-6 Sixth control valve; 4. Vapor compression heat pump; 5. Compressor; 6. Evaporator; 7. Condenser; 8. Throttling valve; 9-1 First water tank; 9-2 Second water tank; 9-3 Third water tank; 10-1 First circulating pump; 10-2 Second circulating pump; 11. Solar energy; 12. Solar collector; 13-1 First heat exchanger; 13-2 Second heat exchanger; 14. Vacuum membrane module; 15. Vacuum pump. Detailed Implementation

[0015] Figure 1 This invention relates to a multi-energy complementary vacuum membrane distillation wastewater treatment system and method. The following refers to... Figure 1 Describe the specific working process of this technology.

[0016] The device operates as follows: First control valve 3-1 and second control valve 3-2 are opened. Liquid working fluid water absorbs geothermal energy and increases in temperature through the mid-deep geothermal well group 1. It then enters the cold side of the second heat exchanger 13-2 to absorb waste heat from the steam and further increase in temperature. After two heating cycles, the liquid working fluid water enters the hot side of the evaporator 6 in the vapor compression heat pump 4, releasing heat to the refrigerant circulating working fluid on the cold side of the evaporator 6. It then returns to the mid-deep geothermal well group 1 to absorb geothermal energy. The refrigerant working fluid absorbs heat and evaporates into steam on the cold side of the evaporator 6. It then enters the compressor 5 for compression, becoming high-temperature, high-pressure steam. This steam then enters the hot side of the condenser 7, where it condenses and releases heat, becoming low-temperature, high-pressure liquid working fluid. This low-temperature, high-pressure liquid working fluid then passes through the throttling valve 8 to decrease in pressure, becoming low-temperature, low-pressure liquid working fluid. Finally, this low-temperature, low-pressure liquid working fluid enters the cold side of the evaporator 6 to continue absorbing heat and evaporating. The third control valve 3-3, the fourth control valve 3-4, and the first circulation pump 10-1 are opened. The liquid working fluid water in the first water tank 9-1 enters the cold side of the condenser 7 to absorb the heat of the refrigerant working fluid under the drive of the first circulation pump 10-1. Then it enters the solar collector 12 to absorb solar energy for further heating. Then it enters the hot side of the first heat exchanger 13-1 to release heat. Finally, it returns to the cold side of the condenser 7 to continue absorbing the heat of the refrigerant working fluid. The fifth control valve 3-5 and the sixth control valve 3-6 are opened, and the liquid to be treated in the second water tank 9-2 is sent to the cold side of the first heat exchanger 13-1 to absorb heat via the second circulation pump 10-2. Then, the tube side of the vacuum membrane assembly 14 is filled, and the vacuum pump 15 is started to create a vacuum, so that the shell side of the vacuum membrane assembly 14 is under a certain negative pressure. The tube side solution of the vacuum membrane assembly 14 evaporates on the membrane surface and reaches the shell side under the drive of the vapor pressure difference across the membrane. The high-temperature vapor enters the hot side of the second heat exchanger 13-2 through the shell side outlet of the vacuum membrane assembly 14, condenses and releases heat, and is finally collected in the third water tank 9-3. Meanwhile, the concentrated solution in the tube side of the vacuum membrane assembly 14 enters the second water tank 9-2 for further circulation and concentration until the required concentration is reached and then recycled.

[0017] Although the specific implementation process of the present invention has been described in detail above with reference to the accompanying drawings, this is not intended to limit the present invention. Those skilled in the art should understand that all variations and improvements made within the spirit and principles of the present invention and under the guidance of the present invention are within the scope of protection of the present invention.

Claims

1. A multi-energy complementary vacuum membrane distillation wastewater treatment system, characterized in that... Mainly includes: Medium-deep geothermal well group (1), first control valve (3-1), second control valve (3-2), third control valve (3-3), fourth control valve (3-4), fifth control valve (3-5), sixth control valve (3-6), vapor compression heat pump (4), first water tank (9-1), second water tank (9-2), third water tank (9-3). The system consists of a first circulating pump (10-1), a second circulating pump (10-2), a solar collector (12), a first heat exchanger (13-1), a second heat exchanger (13-2), a vacuum membrane assembly (14), and a vacuum pump (15); wherein the vapor compression heat pump (4) is composed of a compressor (5), an evaporator (6), a condenser (7), and a throttle valve (8); The outlet of the medium-deep geothermal well group (1) is connected to the cold side inlet of the second heat exchanger (13-2) via the first control valve (3-1), the cold side outlet of the second heat exchanger (13-2) is connected to the hot side inlet of the evaporator (6) in the vapor compression heat pump (4), and the hot side outlet of the evaporator (6) is connected to the inlet of the medium-deep geothermal well group (1) via the second control valve (3-2). The cold side outlet of the evaporator (6) is connected to the inlet of the compressor (5), the outlet of the compressor (5) is connected to the hot side inlet of the condenser (7), and the hot side outlet of the condenser (7) is connected to the cold side inlet of the evaporator (6) through the throttle valve (8). The outlet of the first water tank (9-1) is connected to the inlet of the first circulating pump (10-1) via the fourth control valve (3-4). The outlet of the first circulating pump (10-1) is connected to the cold side inlet of the condenser (7). The cold side outlet of the condenser (7) is connected to the inlet of the solar collector (12) via the third control valve (3-3). The outlet of the solar collector (12) is connected to the hot side inlet of the first heat exchanger (13-1). The hot side outlet of the first heat exchanger (13-1) is connected to the inlet of the first water tank (9-1). The outlet of the second water tank (9-2) is connected to the inlet of the second circulating pump (10-2) via the fifth control valve (3-5). The outlet of the second circulating pump (10-2) is connected to the cold side inlet of the first heat exchanger (13-1). The cold side outlet of the first heat exchanger (13-1) is connected to the tube side inlet of the vacuum membrane module (14). The tube side outlet of the vacuum membrane module (14) is connected to the inlet of the second water tank (9-2). The shell side outlet of the vacuum membrane module (14) is connected to the hot side inlet of the second heat exchanger (13-2). The hot side outlet of the second heat exchanger (13-2) is connected to the inlet of the third water tank (9-3) via the sixth control valve (3-6). The outlet of the third water tank (9-3) is connected to the vacuum pump (15).

2. The multi-energy complementary vacuum membrane distillation wastewater treatment system according to claim 1, characterized in that: The medium-deep geothermal well group (1) is composed of multiple medium-deep geothermal wells (2) connected in parallel. Each medium-deep geothermal well has a diameter of 100-500 mm and a depth of 1000-4000 m. Coaxial casing and U-shaped pipe are used to realize the heat exchange between liquid water and geothermal energy.

3. The multi-energy complementary vacuum membrane distillation wastewater treatment system according to claim 1, characterized in that: The working fluid used in the above-mentioned vapor compression heat pump (4) is R134a, or R22, or R123.

4. The multi-energy complementary vacuum membrane distillation wastewater treatment system according to claim 1, characterized in that: The vacuum membrane module (14) consists of multiple hollow fiber membrane tubes, each of which is made of polytetrafluoroethylene hydrophobic microporous membrane with a pore size range of 0.1-0.5 μm.

5. The multi-energy complementary vacuum membrane distillation wastewater treatment system according to claim 1, characterized in that: The first water tank (9-1) is used to store softened water, the second water tank (9-2) is used to store industrial wastewater, and the third water tank (9-3) is used to store condensed fresh water.

6. The working method of the multi-energy complementary vacuum membrane distillation wastewater treatment system according to claim 1 is as follows: Open the first control valve (3-1) and the second control valve (3-2). The liquid working fluid water absorbs geothermal energy and increases in temperature through the medium-deep geothermal well group (1). Then it enters the cold side of the second heat exchanger (13-2) to absorb the residual heat of the steam and further increase in temperature. After being heated twice, the liquid working fluid water enters the hot side of the evaporator (6) in the vapor compression heat pump (4) and releases heat to the refrigerant circulating working fluid on the cold side of the evaporator (6). Then it returns to the medium-deep geothermal well group (1) to absorb geothermal energy. The refrigerant working fluid absorbs heat and evaporates into steam on the cold side of the evaporator (6). It enters the compressor (5) to be compressed into high-temperature and high-pressure steam. Then it enters the hot side of the condenser (7) and releases heat through condensation to become low-temperature and high-pressure liquid working fluid. The low-temperature and high-pressure liquid working fluid then passes through the throttle valve (8) to reduce the pressure and become low-temperature and low-pressure liquid working fluid. Finally, the low-temperature and low-pressure liquid working fluid enters the cold side of the evaporator (6) to continue to absorb heat and evaporate. Open the third control valve (3-3), the fourth control valve (3-4) and the first circulation pump (10-1). The liquid working fluid water in the first water tank (9-1) enters the cold side of the condenser (7) to absorb the heat of the refrigerant working fluid under the drive of the first circulation pump (10-1). Then it enters the solar collector (12) to absorb solar energy and further increase the temperature. Then it enters the hot side of the first heat exchanger (13-1) to release heat. Finally, it returns to the cold side of the condenser (7) to continue to absorb the heat of the refrigerant working fluid. Open the fifth control valve (3-5) and the sixth control valve (3-6), and send the liquid to be treated in the second water tank (9-2) to the cold side of the first heat exchanger (13-1) to absorb heat through the second circulation pump (10-2). Then fill the tube side of the vacuum membrane module (14), start the vacuum pump (15) to evacuate, so that the shell side of the vacuum membrane module (14) is in a certain negative pressure state. The tube side solution of the vacuum membrane module (14) evaporates on the membrane surface and reaches the shell side under the drive of the vapor pressure difference on both sides of the membrane. The high temperature vapor enters the hot side of the second heat exchanger (13-2) through the shell side outlet of the vacuum membrane module (14) and condenses to release heat, and is finally collected in the third water tank (9-3). The tube side concentrated solution of the vacuum membrane module (14) enters the second water tank (9-2) to continue to circulate and concentrate until the required concentration is reached and then recycled.

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