Multi-energy complementary vacuum membrane distillation wastewater treatment system and method

Abstract

The invention discloses a multi-energy complementary vacuum membrane distillation wastewater treatment system and method, and belongs to the field of energy conservation and environmental protection. The system comprises a solar heat collector, a mid-deep rock hot well, a steam compression type heat pump, a vacuum membrane assembly, a circulating pump, a heat exchanger, a vacuum pump and the like. The method is characterized in that liquid water is used as a working medium, firstly, heat is gradually increased through a mid-deep stratum rock hot well group deeply buried below 1500m underground, vacuum membrane distillation secondary steam, a steam compression heat pump and a solar heat collection system in sequence, and then the heat is transferred to industrial wastewater to be treated through a heat exchanger, so that the industrial wastewater reaches the required temperature; a vacuum membrane assembly is filled with a circulating pump, purification and separation are performed through a vacuum membrane distillation process in a negative pressure environment, sensible heat and latent heat of produced secondary steam are transferred to liquid working medium water through a heat exchanger for condensation and collection, and produced concentrated liquid returns to a water tank for continuous circulating concentration and is recycled after the required concentration is achieved. The geothermal energy, the solar energy and the secondary steam heat energy are recycled to the maximum extent, the energy requirement in the vacuum membrane distillation wastewater treatment process is met through multi-energy complementation, and the system has the advantages of being high in energy utilization efficiency, low in operation cost, high in operation stability and the like and is suitable for the fields of industrial heat supply, building heating, ventilation and air conditioning and the like.

Description

Technical Field

[0001] The 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 Art

[0002] Vacuum membrane distillation is a new separation technology that has emerged in recent years. It can be widely used in industrial wastewater treatment, seawater desalination, Chinese medicine concentration and food industry. The vacuum membrane distillation system is mainly composed of vacuum membrane components, circulation pumps, raw material tanks, condensate tanks and vacuum pumps. The vacuum membrane components are composed of multiple hollow fiber membrane tubes, each of which is made of polytetrafluoroethylene hydrophobic microporous membranes. Driven by the circulation pump, the raw liquid in the raw material tank is filled with the hot side of the vacuum membrane component, and a certain negative pressure environment is created on the cold side of the vacuum membrane component by the vacuum pump. Driven by the vapor pressure difference on both sides of the hydrophobic membrane, the water molecules in the solution on the hot side membrane surface evaporate and pass through the membrane pores to the cold side, and finally condense in the condenser, thereby separating the raw liquid into concentrate and fresh water. However, due to factors such as membrane pollution, temperature concentration polarization and lack of latent heat recovery devices, the existing vacuum membrane distillation systems generally have problems such as poor thermodynamic properties and low energy utilization efficiency, which limits the industrial application of vacuum membrane distillation technology.

[0003] Renewable energy is a resource in nature that can be continuously regenerated and used sustainably. It mainly includes solar energy, geothermal energy, wind energy, hydropower, biomass energy and ocean energy. It is very rich and can be widely obtained. Among them, solar energy is the most common renewable energy, with the advantages of being clean and harmless, continuous and huge energy. It mainly collects and utilizes solar radiation energy through photothermal conversion and photoelectric conversion to meet various needs such as heating and power generation. It has a very broad application prospect. Geothermal energy is natural heat energy extracted from the molten rock inside the earth. It is also a clean renewable energy with the advantages of large reserves, wide distribution, green and low-carbon, strong applicability and good stability. Especially for medium and deep geothermal heat, by installing a closed metal heat exchanger in an underground borehole and utilizing the circulating flow of the medium in the heat exchanger, the heat energy from deep underground is exported, and the energy needs of human heating, hot water, cooling and other energy are met through equipment such as high-efficiency heat pump units. In addition, this technology does not interfere with the natural environment, has no impact on the geological environment such as groundwater layers and soil, and has the advantages of environmental protection and sustainability. At present, although solar energy and medium-deep geothermal technology have been gradually applied in my country and widely used in the field of HVAC, there are few studies on their application in the field of industrial wastewater treatment, especially the research on vacuum membrane distillation process is blank. Therefore, coupling solar energy and medium-deep geothermal technology to efficiently and low-cost meet the energy demand of the vacuum membrane distillation system for treating industrial wastewater has important value and significance for the industrial application of vacuum membrane distillation technology. Summary of the invention

[0004] The invention provides a multi-energy complementary vacuum membrane distillation wastewater treatment system and method with low energy consumption and strong stability.

[0005] A multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that it mainly includes: a medium-deep geothermal well group, 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 steam compression heat pump, a first water tank, a second water tank, a third water tank, a first circulation pump, a second circulation pump, a solar collector, a first heat exchanger, a second heat exchanger, a vacuum membrane assembly, and a vacuum pump. The steam compression heat pump is composed of a compressor, an evaporator, a condenser and a throttle valve; the outlet of the medium-deep geothermal well group is connected to the cold side inlet of the second heat exchanger through the first control valve, the cold side outlet of the second heat exchanger is connected to the hot side inlet of the evaporator in the steam compression heat pump, and the hot side outlet of the evaporator is connected to the inlet of the medium-deep geothermal well group through the second control valve; the cold side outlet of the evaporator is connected to the inlet of the compressor, the outlet of the compressor 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 through the throttle valve; the outlet of the first water tank is connected to the inlet of the first circulation pump through the fourth control valve, and the outlet of the first circulation pump is connected to the cold side inlet of the condenser. The cold side outlet of the condenser is connected to the inlet of the solar collector through the third control valve, the outlet of the solar collector is connected to the inlet of the hot side of the first heat exchanger, and the hot side outlet of the first heat exchanger is connected to the inlet of the first water tank; wherein the second water tank outlet is connected to the inlet of the second circulation pump through the fifth control valve, the outlet of the second circulation pump is connected to the inlet of the cold side of the first heat exchanger, the cold side outlet of the first heat exchanger is connected to the inlet of the tube side of the vacuum membrane assembly, and the tube side outlet of the vacuum membrane assembly is connected to the inlet of the second water tank; the shell side outlet of the vacuum membrane assembly is connected to the inlet of the hot side of the second heat exchanger, the hot side outlet of the second heat exchanger is connected to the inlet of the third water tank through the sixth control valve, and the outlet of the third water tank is connected to the vacuum pump.

[0006] The working method of the solar medium-deep geothermal multi-energy complementary vacuum membrane distillation wastewater treatment system is: open the first control valve and the second control valve, the liquid working medium water absorbs geothermal energy through the medium-deep geothermal well group to increase the temperature, and then enters the cold side of the second heat exchanger to absorb steam waste heat for further temperature increase. After two temperature increases, the liquid working medium water enters the hot side of the evaporator in the steam compression heat pump unit, releases heat to the refrigerant circulating working medium on the cold side of the evaporator, and then returns to the medium-deep rock thermal well group to absorb geothermal energy; the refrigerant working medium absorbs heat on the cold side of the evaporator and evaporates into steam, enters the compressor for compression to become high-temperature and high-pressure steam, and then enters the hot side of the condenser to release heat through condensation to become low-temperature and high-pressure liquid working medium, and the low-temperature and high-pressure liquid working medium is then reduced in pressure by the throttle valve to become low-temperature and low-pressure liquid working medium, and finally the low-temperature and low-pressure liquid working medium enters the cold side of the evaporator to continue absorbing heat and evaporating; the third control valve, the fourth control valve and the first circulating pump are opened, and the liquid working medium water in the first water tank enters the cold side of the condenser driven by the first circulating pump to absorb the heat of the refrigerant working medium, and then enters the solar collector to absorb solar energy The temperature is further increased, and then it enters the hot side of the first heat exchanger to release heat, and finally returns to the cold side of the condenser to continue to absorb the heat of the refrigerant; the fifth control valve and the sixth control valve are opened, and the liquid to be treated in the second water tank is sent to the cold side of the first heat exchanger through the second circulation pump to absorb heat, and then fills the tube side of the vacuum membrane distillation component, and starts the vacuum pump to evacuate, so that the shell side of the vacuum membrane distillation component is in a certain negative pressure state. The tube side solution of the vacuum membrane distillation component evaporates on the membrane surface and reaches the shell side driven by the steam pressure difference on both sides of the membrane. The high-temperature steam enters the hot side of the second heat exchanger through the shell side outlet of the vacuum membrane distillation component to condense and release heat, and is finally collected in the third water tank; and the tube side concentrated solution of the vacuum membrane distillation component enters the second water tank to continue to circulate and concentrate until it reaches the required concentration and is recycled.

[0007] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized by: using solar energy and geothermal energy complementarily as heat sources in the vacuum membrane distillation wastewater treatment process, eliminating external heat sources and cooling water systems, not only effectively utilizing renewable energy, but also efficiently recycling and treating industrial wastewater.

[0008] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized by: 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 casing and U-tube to realize heat exchange between liquid water and geothermal energy.

[0009] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that the above-mentioned steam compression heat pump is composed of a compressor, an evaporator, a condenser and a throttle valve, and the working fluid used is R134a, or R22, or R123.

[0010] The above-mentioned multi-energy complementary vacuum membrane distillation wastewater treatment system is characterized in that the vacuum membrane assembly is composed of a plurality of hollow fiber membrane tubes, each of which is made of a polytetrafluoroethylene hydrophobic microporous membrane with a pore size of 0.1-0.5 um.

[0011] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The invention proposes a multi-energy complementary vacuum membrane distillation wastewater treatment system and method; Names of the numbers in the figure: 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 steam compression heat pump, 5 compressor, 6 evaporator, 7 condenser, 8 throttle valve, 9-1 first water tank, 9-2 second water tank, 9-3 third water tank, 10-1 first circulation pump, 10-2 second circulation pump, 11 solar energy, 12 solar energy collector, 13-1 first heat exchanger, 13-2 second heat exchanger, 14 vacuum membrane assembly, 15 vacuum pump. DETAILED DESCRIPTION

[0013] Figure 1 The present invention proposes a multi-energy complementary vacuum membrane distillation wastewater treatment system and method. Figure 1 Describe the specific working process of this technology.

[0014] The working process of the device is as follows: open the first control valve 3-1 and the second control valve 3-2, the liquid working medium water absorbs geothermal energy through the medium-deep geothermal well group 1 to increase the temperature, and then enters the cold side of the second heat exchanger 13-2 to absorb the residual heat of steam to further increase the temperature. After two temperature increases, the liquid working medium water enters the hot side of the evaporator 6 in the steam compression heat pump unit 4, releases heat to the refrigerant circulating working medium on the cold side of the evaporator 6, and then returns to the medium-deep geothermal well group 1 to absorb geothermal energy. The refrigerant working medium absorbs heat and evaporates to become steam on the cold side of the evaporator 6, enters the compressor 5 for compression to become high-temperature and high-pressure steam, and then enters the hot side of the condenser 7 to release heat through condensation to become a low-temperature and high-pressure liquid working medium, and the low-temperature and high-pressure liquid working medium is then reduced in pressure by the throttle valve 8 to become a low-temperature and low-pressure liquid working medium, and finally the low-temperature and low-pressure liquid working medium 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 medium water in the first water tank 9-1 enters the cold side of the condenser 7 driven by the first circulation pump 10-1 to absorb the heat of the refrigerant working medium, then enters the solar collector 12 to absorb solar energy for further temperature increase, then enters the hot side of the first heat exchanger 13-1 to release heat, and finally returns to the cold side of the condenser 7 to continue to absorb the heat of the refrigerant working medium. 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 through the second circulation pump 10-2 to absorb heat, and then fill the tube side of the vacuum membrane distillation component 14, and the vacuum pump 15 is started to evacuate, so that the shell side of the vacuum membrane distillation component 14 is in a certain negative pressure state, and the tube side solution of the vacuum membrane distillation component 14 evaporates on the membrane surface and reaches the shell side driven by the steam pressure difference on both sides of the membrane. The high-temperature steam enters the hot side of the second heat exchanger 13-2 through the shell side outlet of the vacuum membrane distillation component 14 to condense and release heat, and is finally collected in the third water tank 9-3. The tube side concentrated solution of the vacuum membrane distillation component 14 enters the second water tank 9-2 to continue circulating and concentrating until it reaches the required concentration and is recycled.

[0015] Although the specific implementation process of the present invention is described in detail above according to the accompanying drawings, this does not limit the present invention. Ordinary technicians in this field should understand that all changes and improvements made within the purpose and principles of the present invention and under the inspiration of the present invention belong to the protection scope of the present invention.

Claims

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

2. A multi-energy complementary vacuum membrane distillation wastewater treatment system according to claim 1, characterized in that: The medium-deep geothermal well group (1) is formed by connecting a plurality of medium-deep geothermal wells (2) 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 tubes are used to realize 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 steam 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 assembly (14) is composed of a plurality of hollow fiber membrane tubes, each of which is made of a polytetrafluoroethylene hydrophobic microporous membrane with a pore size ranging from 0.1 to 0.5 um.

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 waste water, 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: The first control valve (3-1) and the second control valve (3-2) are opened, and the liquid working medium water absorbs geothermal energy through the medium-deep geothermal well group (1) to increase its temperature, and then enters the cold side of the second heat exchanger (13-2) to absorb the residual heat of steam to further increase its temperature. After being heated twice, the liquid working medium water enters the hot side of the evaporator (6) in the steam compression heat pump unit (4), releases heat to the refrigerant circulating working medium on the cold side of the evaporator (6), and then returns to the medium-deep geothermal well group (1) to absorb geothermal energy; the refrigerant working medium absorbs heat on the cold side of the evaporator (6) and evaporates into steam, enters the compressor (5) to be compressed into high-temperature and high-pressure steam, and then enters the hot side of the condenser (7) to release heat through condensation to become a low-temperature and high-pressure liquid working medium, and the low-temperature and high-pressure liquid working medium then passes through the throttle valve (8) to reduce its pressure to become a low-temperature and low-pressure liquid working medium, and finally the low-temperature and low-pressure liquid working medium 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, and the liquid working medium water in the first water tank (9-1) enters the cold side of the condenser (7) driven by the first circulation pump (10-1) to absorb the heat of the refrigerant working medium, then enters the solar collector (12) to absorb solar energy for further temperature increase, then enters the hot side of the first heat exchanger (13-1) to release heat, and finally returns to the cold side of the condenser (7) to continue to absorb the heat of the refrigerant working medium; 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) through the second circulation pump (10-2) to absorb heat, and then fills the tube side of the vacuum membrane distillation component (14), and the vacuum pump (15) is started to evacuate, so that the shell side of the vacuum membrane distillation component (14) is in a certain negative pressure state, and the tube side solution of the vacuum membrane distillation component (14) evaporates on the membrane surface and reaches the shell side driven by the steam pressure difference on both sides of the membrane. The high-temperature steam enters the hot side of the second heat exchanger (13-2) through the shell side outlet of the vacuum membrane distillation component (14) to condense and release heat, and is finally collected in the third water tank (9-3); and the tube side concentrated solution of the vacuum membrane distillation component (14) enters the second water tank (9-2) to continue circulating and concentrating until it reaches the required concentration and is recycled.

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