Desalination and dehydration recovery device for ethylene glycol waste liquid

Abstract

The utility model discloses a desalting, dewatering and recycling device for ethylene glycol waste liquid, which is used for recycling ethylene glycol from the ethylene glycol waste liquid containing sodium chloride and water. The recovery device comprises an evaporative crystallization unit, a desalination unit, a rectification dehydration unit, a condensate water collection unit and a vacuum unit which are connected in sequence, wherein the evaporative crystallization unit is used for evaporating and concentrating ethylene glycol waste liquid and separating out sodium chloride crystals, the desalination unit is used for separating, concentrating and separating out green sodium crystals, the rectification dehydration unit is used for separating ethylene glycol and water, and the condensate water unit is used for collecting condensate water of the rectification unit; the evaporative crystallization section adopts a vacuum single-effect process and a separator amplification special design, so that entrainment of liquid drops containing sodium chloride is effectively prevented, the evaporative crystallization unit and the rectification dehydration unit control high vacuum degree, energy consumption is saved, and the device is easy to realize; meanwhile, the device is simple in technological process, high in automation degree and low in operation cost, meets the sustainable development requirement and can be widely applied to the actual industrial production process.

Description

Technical Field

[0001] The utility model belongs to the field of wastewater treatment and environmental protection, and specifically relates to a desalting, dehydrating and recycling device for ethylene glycol waste liquid. Background Art

[0002] Ethylene glycol is mainly used to make polyester, terylene, polyester resin, desiccant, plasticizer, surfactant, synthetic fiber, cosmetics, and antifreeze; the freezing point of ethylene glycol changes with the concentration of ethylene glycol in aqueous solution. When the concentration is below 60%, the freezing point decreases as the concentration of ethylene glycol in aqueous solution increases. However, after the concentration exceeds 60%, the freezing point increases with the increase of ethylene glycol concentration. When the content of ethylene glycol is 60%, the freezing point can be reduced to -48.3°C. Based on its properties, offshore oil platforms and other offshore operating platforms often use ethylene glycol as an antifreeze. Since its use environment is usually exposed to seawater (sodium chloride), its components when recovered as platform antifreeze waste liquid are basically composed of ethylene glycol, sodium chloride, and water. The cost of treating this waste liquid as hazardous waste is high and causes waste of resources. Utility Model Content

[0003] The utility model aims to overcome the defects of the prior art and provides a desalting, dehydrating and recovering device for ethylene glycol waste liquid.

[0004] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a desalination and dehydration recovery device for ethylene glycol waste liquid, characterized in that it includes an evaporation crystallization unit, a desalination unit, a distillation and dehydration unit, and a vacuum unit connected in sequence; the evaporation crystallization unit is connected to the desalination unit, the desalination unit is connected to the distillation and dehydration unit, and the vacuum unit is connected to the distillation and dehydration unit.

[0005] Preferably, the evaporation crystallization unit includes a feed pump, an evaporation crystallizer, a forced circulation pump, a forced circulation heat exchanger, and a crystallization discharge pump which are connected in sequence, the inlet of the feed pump is connected to the waste liquid storage tank outside the boundary area, the crystallization discharge pump is connected to the desalination unit, and the upper end of the gas phase of the evaporation crystallizer is provided with a separation section with filler, and the upper end of the gas phase of the evaporation crystallizer is connected to the distillation dehydration unit.

[0006] Preferably, the desalination unit comprises a thickener, a centrifuge, a mother liquor tank, and a mother liquor reflux pump which are connected in sequence; the feed port of the thickener is connected to the crystallization discharge pump, and the outlet of the mother liquor reflux pump is connected to the circulation pipeline of the crystallizer of the evaporation crystallization unit.

[0007] Preferably, the distillation dehydration unit includes a transfer pump, a concentrate pump, a falling film circulation pump, a falling film reboiler, a distillation dehydration tower, a condenser, a receiving tank, and a distillation water pump which are connected in sequence; the outlet of the transfer pump is connected to the gas phase pipe at the top of the evaporation crystallizer for reflux of the gas phase filling section of the evaporation crystallizer; the tail gas pipe of the condenser is connected to the vacuum unit.

[0008] Preferably, the vacuum unit comprises an exhaust pipe, a water ring vacuum pump, a working fluid circulation cooling plate exchanger, and a steam-water separator which are connected in sequence; the inlet of the water ring vacuum pump is connected to the exhaust pipe of the condenser of the distillation and dehydration unit.

[0009] Preferably, the evaporation gas phase pressure of the evaporation crystallization unit is controlled at -80 KPa, and the liquid phase temperature is controlled below 130°C. Negative pressure evaporation ensures low consumption of preheating steam, and controlling the liquid phase temperature facilitates the selection and implementation of the heating medium.

[0010] Preferably, the gas phase pressure at the top of the distillation and dehydration unit is controlled at -80 KPa, and the liquid phase temperature is <125°C.

[0011] 1. The beneficial effects of the utility model compared with the prior art are: the desalination and dehydration recovery device for ethylene glycol waste liquid described in the utility model provides a process for recovering ethylene glycol from high-salt ethylene glycol wastewater, realizes the separation of sodium chloride, ethylene glycol and water, thereby realizing the reuse of ethylene glycol and achieving the purpose of turning waste into treasure; compared with traditional hazardous waste treatment methods, the treatment cost is low and it is more energy-saving and environmentally friendly.

[0012] 2. The utility model adopts the process of evaporation crystallization and centrifugal separation to make sodium chloride crystallize out in the wastewater system through concentration, and then separate the sodium chloride with a centrifuge. The evaporation crystallization and distillation dehydration unit needs to control the evaporation gas phase pressure to -80kPa, so as to control the liquid phase temperature below 130°C, ensure the operability of centrifugal separation, reduce the preheating heat load, and facilitate the selection of heating medium.

[0013] 3. The evaporation crystallizer of the evaporation crystallization unit of the utility model adopts a specially designed gas-phase gas-liquid separation section, which uses sedimentation to reduce gas-liquid entrainment and then enters the separator packing section to further reduce droplet entrainment, thereby preventing sodium chloride from entering the distillation dehydration unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0015] Figure 1The present invention is a schematic structural diagram of a desalination, dehydration and recovery device for ethylene glycol waste liquid provided in a specific embodiment of the present invention.

[0016] The reference numerals in the figure are as follows: 1. feed pump; 2. forced circulation heat exchanger; 3. evaporator crystallizer; 4. crystallization discharge pump; 5. forced circulation pump; 6. thickener; 7. centrifuge; 8. mother liquor reflux pump; 9. mother liquor tank; 10. transfer pump; 11. falling film reboiler; 12. distillation dehydration tower; 13. falling film circulation pump; 14. concentrate pump; 15. water ring vacuum pump; 16. condenser; 17. receiving tank; 18. distillation water pump. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0018] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0019] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in this utility model specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0020] It should be further understood that the term “and / or” used in the present specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0021] like Figure 1 The specific embodiment shown is a desalination and dehydration recovery device for ethylene glycol waste liquid provided in this embodiment, which can be used in the process of recovering ethylene glycol from high-salt ethylene glycol waste liquid.

[0022] See also Figure 1The desalination and dehydration recovery device for ethylene glycol waste liquid includes an evaporation crystallization unit, a desalination unit, a distillation dehydration unit, and a vacuum unit; the evaporation crystallization unit is connected to the desalination unit, the desalination unit is connected to the distillation dehydration unit, and the vacuum unit is connected to the distillation dehydration unit. The evaporation crystallization unit includes a feed pump 1, an evaporation crystallizer 3, a forced circulation pump 5, a forced circulation heat exchanger 2, and a crystallization discharge pump 4 connected in sequence, the inlet of the feed pump 1 is connected to the waste liquid storage tank outside the boundary area, the crystallization discharge pump 4 is connected to the desalination unit, the gas phase upper end of the evaporation crystallizer 3 is provided with a separation section with fillers, and the gas phase upper end of the evaporation crystallizer 3 is connected to the distillation dehydration unit. The desalination unit includes a thickener 6, a centrifuge 7, a mother liquid tank 9, and a mother liquid reflux pump 8 connected in sequence; the feed port of the thickener 6 is connected to the crystallization discharge pump 4, and the outlet of the mother liquid reflux pump 8 is connected to the circulation pipeline of the crystallizer of the evaporation crystallization unit. The distillation and dehydration unit includes a transfer pump 10, a concentrate pump 14, a falling film circulation pump 13, a falling film reboiler 11, a distillation and dehydration tower 12, a condenser 16, a receiving tank 17, and a distillation water pump 18, which are connected in sequence; the outlet of the transfer pump 10 is connected to the gas phase pipe at the top of the evaporation crystallizer 3, which is used for reflux of the gas phase filling section of the evaporation crystallizer 3; the tail gas pipe of the condenser 16 is connected to the vacuum unit. The distillation and dehydration unit includes a transfer pump 10, a concentrate pump 14, a falling film circulation pump 13, a falling film reboiler 11, a distillation and dehydration tower 12, a condenser 16, a receiving tank 17, and a distillation water pump 18, which are connected in sequence; the outlet of the transfer pump 10 is connected to the gas phase pipe at the top of the evaporation crystallizer 3, which is used for reflux of the gas phase filling section of the evaporation crystallizer 3; the tail gas pipe of the condenser 16 is connected to the vacuum unit. The vacuum unit comprises an exhaust pipe, a water ring vacuum pump 15, a working fluid circulation cooling plate, and a steam-water separator which are connected in sequence; the inlet of the water ring vacuum pump 15 is connected to the exhaust pipe of the condenser 16 of the distillation and dehydration unit.

[0023] In this embodiment, the inlet water temperature of a solution of a desalination and dehydration recovery device for ethylene glycol waste liquid is 35° C., the mass fraction of ethylene glycol is 50%, the concentration of sodium chloride is 3%, and the mass flow rate is 35 t / h.

[0024] Among them, Figure 1 As shown, the ethylene glycol waste liquid to be treated enters the evaporation crystallizer 3 through the action of the feed pump 1.

[0025] The solution of the evaporation crystallizer 3 passes through the entrance of the forced circulation pump 5, and then enters the forced circulation heat exchanger 2. After the temperature and pressure are increased, it enters the evaporation crystallizer 3 for flash separation. The evaporation gas phase temperature in the evaporation crystallizer 3 is 71°C, the liquid phase temperature is 124°C, and the pressure is -80KPa. After flash separation, the concentrated liquid is pumped into the forced circulation heat exchanger 2 through the forced circulation pump 5 for heating and evaporation again. The concentrated liquid circulates in this way. When the sodium chloride in the waste liquid reaches supersaturation, crystals are precipitated. The slurry is sent to the thickener 6 through the bottom crystallization discharge pump 4. After the sodium chloride crystals are concentrated, they enter the centrifuge 7 for centrifugal separation. The separated sodium chloride crystals are sent out of the system, and the separated ethylene glycol mother liquid tank 9 is returned to the forced circulation heat exchanger 2 through the mother liquid reflux pump 8. The ethylene glycol and water vapor evaporated by evaporation flash enter the gas phase filling section of the crystallizer, and perform mass and heat transfer with the transfer material of the distillation and dehydration unit, and enter the distillation and dehydration unit after fully reducing the entrainment of sodium chloride.

[0026] The ethylene glycol and water vapor separated from the evaporation crystallizer enter the middle of the distillation and dehydration tower 12 of the distillation and dehydration unit to form an ascending airflow, and perform mass and heat transfer with the descending reflux liquid in the packing of the distillation and dehydration tower 12. In the distillation and dehydration tower, the heavy component ethylene glycol is easily condensed and descends to the tower bottom, and the light component water is easily steamed and rises to the condenser 16 for condensation. A part of the distillation condensed water directly refluxes into the distillation and dehydration tower, and a part enters the receiving tank 17 for receiving. The buffered condensed water is transported out of the system through the distillation water pump 18. The bottom concentrate is pumped into the falling film reboiler 11 from the bottom of the kettle by the falling film circulation pump 13 for heating. The vaporized steam enters the distillation and dehydration tower to form an ascending airflow. A part of the ethylene glycol concentrate enters the evaporation crystallizer 3 through the transfer pump 10, and a part is transported out of the system through the concentrate pump 14. The distillation and dehydration unit controls the tower top pressure to be -80 kPa, the tower top temperature to be 60°C, and the tower bottom temperature to be 117°C; the tower top reflux ratio is 0.62.

[0027] The ethylene glycol waste liquid desalination and dehydration recovery device described in this embodiment has a feed temperature of 35°C, a feed rate of 35 t / h, an ethylene glycol mass fraction of 50%, a sodium chloride concentration of 3%, a concentrated liquid product ethylene glycol concentration of 99%, and water 1%; the operating parameters are shown in Table 1.

[0028] Table 1 Operating parameters

[0029]

[0030]

[0031] The utility model evaporation crystallization and distillation dehydration unit controls the evaporation gas phase pressure to -80kPa, thereby controlling the liquid phase temperature below 130°C, ensuring the operability of centrifugal separation, reducing the preheating heat load, and facilitating the selection of heating medium.

[0032] The evaporation crystallizer of the utility model evaporation crystallization unit adopts a specially designed gas-liquid separation section, which uses sedimentation to reduce gas-liquid entrainment and then enters the separator packing section to further reduce droplet entrainment, thereby preventing sodium chloride from entering the distillation dehydration unit.

[0033] The desalination and dehydration recovery device for ethylene glycol waste liquid described in the utility model provides a process for recovering ethylene glycol from high-salt ethylene glycol wastewater, realizes the separation of sodium chloride, ethylene glycol and water, realizes the reuse of ethylene glycol, and achieves the purpose of turning waste into treasure;

[0034] The above examples are only used to further illustrate the technical content of the utility model, so that readers can understand it more easily, but it does not mean that the implementation methods of the utility model are limited to this. Any technical extension or re-creation made based on the utility model is protected by the utility model. The protection scope of the utility model shall be based on the claims.

Claims

1. A desalination and dehydration recovery device for ethylene glycol waste liquid, characterized in that: It comprises an evaporation crystallization unit, a desalination unit, a distillation dehydration unit and a vacuum unit which are connected in sequence; the evaporation crystallization unit is connected to the desalination unit, the desalination unit is connected to the distillation dehydration unit, and the vacuum unit is connected to the distillation dehydration unit.

2. The desalination and dehydration recovery device for ethylene glycol waste liquid according to claim 1, characterized in that: The evaporation crystallization unit comprises a feed pump (1), an evaporation crystallizer (3), a forced circulation pump (5), a forced circulation heat exchanger (2), and a crystallization discharge pump (4) which are connected in sequence. The inlet of the feed pump (1) is connected to a waste liquid storage tank outside the boundary area. The crystallization discharge pump (4) is connected to the desalination unit. The upper end of the gas phase of the evaporation crystallizer (3) is provided with a separation section with fillers. The upper end of the gas phase of the evaporation crystallizer (3) is connected to the distillation dehydration unit.

3. The desalination and dehydration recovery device for ethylene glycol waste liquid according to claim 2, characterized in that: The desalination unit comprises a thickener (6), a centrifuge (7), a mother liquor tank (9), and a mother liquor reflux pump (8) which are connected in sequence; the feed inlet of the thickener (6) is connected to the crystallization discharge pump (4), and the outlet of the mother liquor reflux pump (8) is connected to the circulation pipeline of the crystallizer of the evaporation crystallization unit.

4. The desalination and dehydration recovery device for ethylene glycol waste liquid according to claim 2, characterized in that: The distillation and dehydration unit comprises a material transfer pump (10), a concentrate pump (14), a falling film circulation pump (13), a falling film reboiler (11), a distillation and dehydration tower (12), a condenser (16), a receiving tank (17), and a distillation water pump (18) which are connected in sequence; the outlet of the material transfer pump (10) is connected to the gas phase pipe at the top of the evaporation crystallizer (3) for reflux of the gas phase filling section of the evaporation crystallizer (3); the tail gas pipe of the condenser (16) is connected to the vacuum unit.

5. The desalination and dehydration recovery device for ethylene glycol waste liquid according to claim 4, characterized in that: The vacuum unit comprises an exhaust pipe, a water ring vacuum pump (15), a working fluid circulation cooling plate, and a steam-water separator which are connected in sequence; the inlet of the water ring vacuum pump (15) is connected to the exhaust pipe of the condenser (16) of the distillation and dehydration unit.

6. The desalination and dehydration recovery device for ethylene glycol waste liquid according to claim 2, characterized in that: The evaporation gas phase pressure of the evaporation crystallization unit is controlled at -80KPa, and the liquid phase temperature is controlled below 130°C. Negative pressure evaporation ensures low consumption of preheating steam, and controlling the liquid phase temperature facilitates the selection and implementation of the heating medium.

7. The desalination and dehydration recovery device for ethylene glycol waste liquid according to claim 4, characterized in that: The gas phase pressure at the top of the distillation and dehydration unit is controlled at -80 KPa, and the liquid phase temperature is <125°C.

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