Distillation wastewater treatment system based on carbon dioxide Rankine cycle

Abstract

The utility model relates to the technical field of energy conservation and environmental protection, in particular to a distillation wastewater treatment system based on carbon dioxide Rankine cycle. Comprising a raw material tank, a first circulating pump, a second circulating pump, a first heat exchanger, a second heat exchanger, a third heat exchanger, a vacuum membrane distillation assembly, a double-screw steam compressor, an expansion machine, a condensed water tank, a first control valve, a second control valve and a vacuum pump, an outlet of the first circulating pump is connected with a cold-side inlet of the first heat exchanger. When the system is used, secondary steam condensation latent heat in the system is used as a feed liquid evaporation heat source, and steam condensate water waste heat is used for power generation to provide electric energy for the system, so that the consumption of external energy is remarkably saved, and the evaporation operation cost of the system is greatly reduced; the device is suitable for evaporation and concentration treatment of industrial wastewater in petrochemical engineering, steel, chlor-alkali, non-ferrous metal and other industries.

Description

Technical Field

[0001] The utility model relates to the technical field of energy conservation and environmental protection, in particular to a distillation wastewater treatment system based on a carbon dioxide Rankine cycle. Background Art

[0002] In recent years, my country's synthetic raw material pharmaceutical industry has experienced rapid growth. With this growth, energy demand has also been rising annually. This is particularly true in the production of synthetic raw material pharmaceuticals (including intermediates). Production processes such as fermentation, distillation, crystallization, drying, and desiccation all consume significant amounts of heat energy. The final step in synthetic raw material pharmaceutical production involves treating the various wastewaters generated during previous production processes. This industrial wastewater is often highly concentrated, difficult to degrade, corrosive, and toxic. Discharging it without proper treatment not only pollutes the environment but also wastes resources. Evaporation processes are commonly used for wastewater treatment, with double-effect, multi-effect, and MVR processes being the most common. Industrial steam is typically used as the heat source. While industrial steam costs contribute significantly to a company's production costs, the exhaust and secondary steam generated after heat exchange are also very high in volume. Recycling is rare, with most wastewater being vented or simply discharged through heat exchange and condensation, resulting in significant heat energy waste. Therefore, the development of new and efficient industrial wastewater treatment technologies is necessary.

[0003] Invention patent CN201610983912.4 discloses an MVR membrane distillation system and method. The system mainly includes hollow fiber membrane tubes, hollow fiber solid-wall heat-conducting tubes, brackets, partitions, twin-screw steam compressors and other components. By utilizing MVR to recover the secondary steam latent heat of the vacuum membrane distillation process, the evaporation energy consumption is reduced and the energy utilization efficiency of the system is improved. However, the current MVR membrane distillation system continuously increases the concentration of the feed liquid during the actual evaporation and concentration process, and the power consumption of the steam compressor also increases accordingly. When the feed liquid increases to a certain concentration, the system will no longer be energy-efficient. In addition, the system directly discharges the steam condensate and does not recycle the remaining heat, so there is still great potential for energy saving.

[0004] The CO2 Rankine cycle is a well-established waste heat power generation system. A circulating pump pressurizes CO2, which is then heated using waste heat. The high-temperature, high-pressure CO2 then enters an expander, where it expands and generates power. Finally, it is condensed through a heat exchanger. This entire process achieves a multi-energy coupling of "heat energy + electricity." Therefore, coupling the CO2 Rankine cycle with high-efficiency heat pumps and membrane distillation technologies to achieve efficient industrial wastewater treatment presents a significant challenge. Therefore, this utility model provides a distillation wastewater treatment system based on the CO2 Rankine cycle to address this issue. Utility Model Content

[0005] The purpose of the present invention is to provide a distillation wastewater treatment system based on the carbon dioxide Rankine cycle to solve the problems raised in the above background technology.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] A distillation wastewater treatment system based on a carbon dioxide Rankine cycle includes a raw material tank, a first circulation pump, a second circulation pump, a first heat exchanger, a second heat exchanger, a third heat exchanger, a vacuum membrane distillation component, a twin-screw steam compressor, an expander, a condensate tank, a first control valve, a second control valve, and a vacuum pump. The outlet of the raw material tank is connected to the inlet of the first circulation pump via the first control valve, the outlet of the first circulation pump is connected to the cold side inlet of the first heat exchanger, the cold side outlet of the first heat exchanger is connected to the solution inlet of the lower part of the vacuum membrane distillation component, and the solution outlet of the vacuum membrane distillation component is connected to the top inlet of the raw material tank.

[0008] As a further solution of the present invention, the steam outlet of the vacuum membrane distillation component is connected to the inlet of the twin-screw steam compressor, and the outlet of the twin-screw steam compressor is connected to the hot side inlet of the first heat exchanger.

[0009] As a further solution of the present invention, the hot side outlet of the first heat exchanger is connected to the hot side inlet of the second heat exchanger, the hot side outlet of the second heat exchanger is connected to the top inlet of the condensate tank, the top outlet of the condensate tank is connected to the inlet of the vacuum pump, and the vacuum pump outlet is connected to the second control valve.

[0010] As a further solution of the present invention, the cold side inlet of the second heat exchanger is connected to the outlet of the second circulation pump, the cold side outlet of the second heat exchanger is connected to the inlet of the expander, the outlet of the expander is connected to the hot side inlet of the third heat exchanger, the hot side outlet of the third heat exchanger is connected to the inlet of the second circulation pump, and the twin-screw steam compressor is connected to the central axis of the expander.

[0011] As a further solution of the present invention, the vacuum membrane distillation component is provided with a solution inlet, a solution outlet and a steam outlet on the outside, and is composed of a plurality of hollow fiber membrane tubes on the inside.

[0012] As a further solution of the present invention, each membrane tube in the vacuum membrane distillation assembly is made of a corrosion-resistant polytetrafluoroethylene (PTFE) hydrophobic microporous membrane with a membrane pore size of 0.2-0.4 μm.

[0013] A working method of a distillation wastewater treatment system based on a carbon dioxide Rankine cycle includes the above-mentioned distillation wastewater treatment system based on a carbon dioxide Rankine cycle, and is characterized by comprising the following processes: first, a first circulation pump and a first control valve are turned on, and the feed liquid preheated to a required temperature in a raw material tank is filled with a vacuum membrane distillation component under the drive of the first circulation pump, and then the vacuum pump and the second control valve are turned on to evacuate the system so that the tube side of the vacuum membrane distillation component maintains a required negative pressure environment, and water molecules in the feed liquid in the vacuum membrane distillation component evaporate on the shell side membrane surface, pass through the membrane pores to reach the tube side under the drive of the trans-membrane vapor pressure difference, and then are compressed, heated, and pressurized by a twin-screw steam compressor. It then enters the first heat exchanger to release heat to the cold side liquid for condensation. The condensed water then enters the second heat exchanger to continue releasing heat and is finally collected in the condensate tank. The concentrated liquid returns to the raw material tank through the outlet of the vacuum membrane distillation component to continue circulating and concentrating. After reaching the required concentration, it is recycled. The low-temperature and low-pressure carbon dioxide working medium is pressurized by the second circulation pump and enters the second heat exchanger to absorb heat and become a supercritical state. It then enters the expander to expand and generate electricity. The low-pressure carbon dioxide working medium discharged from the expander then enters the third heat exchanger to release heat and cool into low-temperature and low-pressure carbon dioxide, and finally returns to the second circulation pump to continue circulating operation. The electricity generated by the expander will be used to drive the twin-screw steam compressor.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. When the utility model is used, the secondary steam produced by the vacuum membrane distillation component is compressed, heated and pressurized by a high-efficiency heat pump process, and its latent heat is used as the heat source for evaporating the original liquid, effectively saving external heat sources and cooling water. The waste heat of the steam condensate is recovered by the carbon dioxide Rankine cycle to generate electricity and provide electricity for the operation of the twin-screw steam compressor, effectively saving external electricity, thereby greatly reducing the energy consumption of the entire evaporation process. The system can not only evaporate and concentrate salt solutions, but also evaporate and concentrate highly corrosive solutions such as sulfuric acid and hydrochloric acid.

[0016] 2. When the utility model is used, the latent heat of secondary steam condensation inside the system is used as the heat source for evaporation of the feed liquid, and the waste heat of steam condensed water is used to generate electricity to provide electricity for the system, which significantly saves the consumption of external energy and greatly reduces the evaporation operating costs of the system. It is suitable for evaporation and concentration treatment of industrial wastewater in petrochemical, steel, chlor-alkali, non-ferrous metals and other industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a distillation wastewater treatment system based on the carbon dioxide Rankine cycle.

[0018] In the figure: 1. Raw material tank; 2-1. First circulation pump; 2-2. Second circulation pump; 3-1. First heat exchanger; 3-2. Second heat exchanger; 3-3. Third heat exchanger; 4. Vacuum membrane distillation component; 5. Twin-screw steam compressor; 6. Expander; 7. Condensate tank; 8-1. First control valve; 8-2. Second control valve; 9. Vacuum pump. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0020] In this utility model, the word "exemplary" is used to mean "serving as an example, illustration or description". Any embodiment described in this utility model as "exemplary" is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any person skilled in the art to implement and use the utility model. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the utility model can be implemented without using these specific details. In other examples, well-known structures and processes are not described in detail to avoid obscuring the description of the utility model with unnecessary details. Therefore, the utility model is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the utility model.

[0021] Example

[0022] See also Figure 1 In an embodiment of the present invention, a distillation wastewater treatment system based on the carbon dioxide Rankine cycle includes a raw material tank 1, a first circulation pump 2-1, a second circulation pump 2-2, a first heat exchanger 3-1, a second heat exchanger 3-2, a third heat exchanger 3-3, a vacuum membrane distillation component 4, a twin-screw steam compressor 5, an expander 6, a condensate tank 7, a first control valve 8-1, a second control valve 8-2, and a vacuum pump 9. The outlet of the raw material tank 1 is connected to the inlet of the first circulation pump 2-1 through the first control valve 8-1, the outlet of the first circulation pump 2-1 is connected to the cold side inlet of the first heat exchanger 3-1, the cold side outlet of the first heat exchanger 3-1 is connected to the lower solution inlet of the vacuum membrane distillation component 4, and the solution outlet of the vacuum membrane distillation component 4 is connected to the top inlet of the raw material tank 1.

[0023] The steam outlet of the vacuum membrane distillation component 4 is connected to the inlet of the twin-screw steam compressor 5, and the outlet of the twin-screw steam compressor 5 is connected to the hot side inlet of the first heat exchanger 3-1.

[0024] The hot side outlet of the first heat exchanger 3-1 is connected to the hot side inlet of the second heat exchanger 3-2, the hot side outlet of the second heat exchanger 3-2 is connected to the top inlet of the condensate tank 7, the top outlet of the condensate tank 7 is connected to the inlet of the vacuum pump 9, and the outlet of the vacuum pump 9 is connected to the second control valve 8-2.

[0025] The cold side inlet of the second heat exchanger 3-2 is connected to the outlet of the second circulation pump 2-2, the cold side outlet of the second heat exchanger 3-2 is connected to the inlet of the expander 6, the outlet of the expander 6 is connected to the hot side inlet of the third heat exchanger 3-3, the hot side outlet of the third heat exchanger 3-3 is connected to the inlet of the second circulation pump 2-2, and the twin-screw steam compressor 5 is connected to the central axis of the expander 6.

[0026] The vacuum membrane distillation component 4 is provided with a solution inlet, a solution outlet and a steam outlet on the outside, and is composed of a plurality of hollow fiber membrane tubes on the inside.

[0027] Each membrane tube in the vacuum membrane distillation assembly 4 is made of a corrosion-resistant polytetrafluoroethylene (PTFE) hydrophobic microporous membrane with a pore size of 0.2-0.4 μm.

[0028] The working principle of this utility model is:

[0029] When the present invention is used, firstly, the first circulation pump 2-1 and the first control valve 8-1 are turned on, and the feed liquid preheated to the required temperature in the raw material tank 1 is filled with the vacuum membrane distillation component 4 under the drive of the first circulation pump 2-1, and then the vacuum pump 9 and the second control valve 8-2 are turned on to evacuate the system, so that the tube side of the vacuum membrane distillation component 9 maintains the required negative pressure environment, and the water molecules in the feed liquid in the vacuum membrane distillation component 9 evaporate on the shell side membrane surface, and pass through the membrane pores to reach the tube side under the drive of the trans-membrane vapor pressure difference, and then pass through the twin-screw steam compressor 5 to increase the temperature and pressure, and then enter the first heat exchanger 3-1 to release heat to the cold side feed liquid for condensation, and the condensed water then enters the second The heat exchanger 3-2 continues to release heat and is finally collected in the condensate tank 7. The concentrated liquid returns to the raw material tank through the outlet of the vacuum membrane distillation component 9 to continue circulating and concentrating, and is recycled after reaching the required concentration; the low-temperature and low-pressure carbon dioxide working medium is pressurized by the second circulation pump 2-2 and enters the second heat exchanger 3-2 to absorb heat and become a supercritical state, and then enters the expander 6 to expand and generate electricity, and the low-pressure carbon dioxide working medium discharged from the expander 6 enters the third heat exchanger 3-3 to release heat and cool into low-temperature and low-pressure carbon dioxide, and finally returns to the second circulation pump 2-2 to continue circulating operation, and the electricity generated by the expander 6 will be used to drive the twin-screw steam compressor 5.

[0030] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A distillation wastewater treatment system based on a carbon dioxide Rankine cycle, comprising a raw material tank (1), a first circulation pump (2-1), a second circulation pump (2-2), a first heat exchanger (3-1), a second heat exchanger (3-2), a third heat exchanger (3-3), a vacuum membrane distillation component (4), a twin-screw steam compressor (5), an expander (6), a condensate tank (7), a first control valve (8-1), a second control valve (8-2), and a vacuum pump (9), characterized in that: The outlet of the raw material tank (1) is connected to the inlet of the first circulation pump (2-1) via the first control valve (8-1), the outlet of the first circulation pump (2-1) is connected to the cold side inlet of the first heat exchanger (3-1), the cold side outlet of the first heat exchanger (3-1) is connected to the lower solution inlet of the vacuum membrane distillation component (4), and the solution outlet of the vacuum membrane distillation component (4) is connected to the top inlet of the raw material tank (1).

2. A distillation wastewater treatment system based on carbon dioxide Rankine cycle according to claim 1, characterized in that: The steam outlet of the vacuum membrane distillation component (4) is connected to the inlet of the twin-screw steam compressor (5), and the outlet of the twin-screw steam compressor (5) is connected to the hot side inlet of the first heat exchanger (3-1).

3. The distillation wastewater treatment system based on the carbon dioxide Rankine cycle according to claim 2, characterized in that: The hot side outlet of the first heat exchanger (3-1) is connected to the hot side inlet of the second heat exchanger (3-2), the hot side outlet of the second heat exchanger (3-2) is connected to the top inlet of the condensate tank (7), the top outlet of the condensate tank (7) is connected to the inlet of the vacuum pump (9), and the outlet of the vacuum pump (9) is connected to the second control valve (8-2).

4. A distillation wastewater treatment system based on carbon dioxide Rankine cycle according to claim 3, characterized in that: The cold side inlet of the second heat exchanger (3-2) is connected to the outlet of the second circulation pump (2-2), the cold side outlet of the second heat exchanger (3-2) is connected to the inlet of the expander (6), the outlet of the expander (6) is connected to the hot side inlet of the third heat exchanger (3-3), the hot side outlet of the third heat exchanger (3-3) is connected to the inlet of the second circulation pump (2-2), and the twin-screw steam compressor (5) is connected to the central axis of the expander (6).

5. The distillation wastewater treatment system based on the carbon dioxide Rankine cycle according to claim 1, characterized in that: The vacuum membrane distillation component (4) is provided with a solution inlet, a solution outlet and a steam outlet on the outside, and is composed of a plurality of hollow fiber membrane tubes on the inside.

6. The distillation wastewater treatment system based on the carbon dioxide Rankine cycle according to claim 5, characterized in that: Each membrane tube in the vacuum membrane distillation assembly (4) is made of a corrosion-resistant polytetrafluoroethylene (PTFE) hydrophobic microporous membrane with a membrane pore size of 0.2-0.4 μm.

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