Device and method for removing ammonia nitrogen in high-salinity wastewater

Abstract

The invention relates to a device and a method for removing ammonia nitrogen in high-salinity wastewater. The device comprises a buffer tank, a raw material conveying pump, a raw material preheater, a concentration tower I, a concentration tower II and a concentration tower III which are connected in sequence, tower kettles of the concentration tower I, the concentration tower II and the concentration tower III are respectively connected with corresponding reboilers and tower kettle liquid delivery pumps, and tower tops of the concentration tower I, the concentration tower II and the concentration tower III are respectively connected with corresponding tower top liquid reflux tanks, tower top reflux pumps and tower top coolers; and the tower top liquid return tanks of the concentration tower II and the concentration tower III are respectively connected with corresponding deep coolers. According to the method, three-tower triple-effect differential pressure thermal coupling rectification is adopted, ammonia nitrogen in the high-salinity wastewater is effectively removed, all effective components are recycled, purified water at each tower top can be used for preparing 20 (wt)% of ammonia water, and a tower bottom concentrated solution can be used for refining saline water in chlor-alkali chemical industry; the tower top steam of the concentration tower I can be used as a heat source of the concentration tower II, and the tower top steam of the concentration tower II can be used as a heat source of the concentration tower III, so that the steam consumption is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of high-salt wastewater treatment in chemical production, and specifically relates to a device and a method for removing ammonia nitrogen from high-salt wastewater. Background Art

[0002] In the basic chemical industry, most companies have realized the integrated circular economy model of "chlor-alkali coal-electricity". Chlor-alkali chemicals and coal chemicals will produce a large amount of high-salt wastewater during the production process, and the ammonia nitrogen content in this part of high-salt water is usually relatively high. Traditional high-salt wastewater in industrial production is usually treated by incineration or evaporation crystallization technology. The salt produced is classified as hazardous waste and has difficulty in sales. This makes the treatment of high-salt wastewater only input but no output, resulting in an increase in unit costs and a huge burden on enterprises. Therefore, in order to improve the circular economy industrial chain, it is necessary to invent a device and method for removing ammonia nitrogen from high-salt wastewater, so that the high-salt water after the removal of ammonia nitrogen can be used for chlor-alkali chemical brine refining, and the removed ammonia nitrogen can be used to produce ammonia water.

[0003] Chinese patent CN 215559109 U proposes a salt-containing waste liquid concentration and crystallization system, including a concentration device, a first partition heat exchanger, a compressor and an evaporation crystallization device, wherein the original waste liquid inlet of the concentration device is used to receive the salt-containing waste liquid, the concentrated waste liquid outlet of the concentration device is connected to the heat-absorbing medium inlet of the first partition heat exchanger, the heat-absorbing medium outlet of the first partition heat exchanger is respectively connected to the heat-releasing medium inlet of the concentration device and the waste liquid inlet of the evaporation crystallization device, the steam outlet of the concentration device is connected to the steam inlet of the compressor, the steam outlet of the compressor is connected to the heat-releasing medium inlet of the first partition heat exchanger, and the heat-releasing medium outlet of the first partition heat exchanger is used to output steam. Although the salt-containing waste liquid concentration and crystallization system described in the utility model can reduce the emission of environmental pollutants and improve energy utilization, thereby reducing the operating cost of the salt-containing waste liquid concentration and crystallization system, the salt-containing waste liquid concentration and crystallization system described in the invention cannot be used to treat wastewater containing organic matter.

[0004] Chinese patent CN 217479269 U discloses a caprolactam waste liquid resource treatment device containing NH4+, comprising a reactor connected to the caprolactam device, an ammonia evaporation tower connected to the reactor, an ammonia absorption tower and a concentration tower respectively connected to the ammonia evaporation tower, the ammonia absorption tower is connected to the ammonium sulfate crystallization system, and the concentration tower is respectively connected to the sewage biochemical treatment device and the incineration device. The waste liquid in the caprolactam waste liquid resource treatment device containing NH4+ described in the utility model is concentrated by a negative pressure double-effect tower. Although the process is simple and the operation is convenient, the steam usage is large, which is not very ideal in terms of energy saving. Summary of the invention

[0005] Based on the problems existing in the prior art, the purpose of the present invention is to provide a device and method for removing ammonia nitrogen from high-salinity wastewater.

[0006] The objective of the present invention is achieved through the following technical scheme: A device for removing ammonia nitrogen from high-salt wastewater comprises a buffer tank, a raw material delivery pump, a raw material preheater, a concentration tower I, a concentration tower II, and a concentration tower III which are connected in sequence.

[0007] The concentration tower I and the concentration tower II are packed towers; the upper section of the concentration tower III is a packed tower, and the lower section is a plate tower.

[0008] The tower bottoms of the concentration towers I, II and III are respectively connected with corresponding reboilers and tower bottom liquid delivery pumps, and the tower tops are respectively connected with corresponding tower top liquid reflux tanks, tower top reflux pumps and tower top coolers.

[0009] The bottom of the concentration tower I is provided with a bottom liquid cooler.

[0010] The bottoms of the concentration tower II and the concentration tower III are respectively connected to corresponding bottom circulation pumps.

[0011] The top liquid reflux tanks of the concentration tower II and the concentration tower III are respectively connected with corresponding deep coolers.

[0012] The top of the concentration tower III is also connected to an evaporative condenser, and the evaporative condenser and the top cooler of the concentration tower III are connected in series or in parallel.

[0013] A venting pipeline is respectively arranged on the top of the concentration tower I, the concentration tower II and the concentration tower III to connect with the cooling separator.

[0014] The above-mentioned device for removing ammonia nitrogen from high-salinity wastewater specifically comprises the following process steps: ① The high-salt wastewater from outside the boundary with ammonia nitrogen content of 1000-1500 mg / L, salt content of 8-10 (wt)%, and pH of 10-11 is stabilized and buffered in the buffer tank, and then the pressure is raised to 0.4-0.6 MPaG through the raw material delivery pump, and then preheated by the top cooler of the concentration tower III, the top cooler of the concentration tower II, the top cooler of the concentration tower I, the bottom liquid cooler of the concentration tower I, and the raw material preheater, and then sent to the middle and lower part of the concentration tower I, and heated by the reboiler of the concentration tower I, so that the rising steam and the descending liquid are fully in contact, so as to achieve the separation of water and heavy components. The temperature of the bottom of the concentration tower I is controlled at 100-110°C; the pressure at the top of the concentration tower I is controlled at 10-50kPaG; the top steam of the concentration tower I is used as the heat source of the reboiler of the concentration tower II, heating the bottom liquid of the concentration tower II while condensing the top steam of the concentration tower I; the condensed liquid enters the top liquid reflux tank of the concentration tower I, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of the concentration tower I, a part of it is sent to the top of the concentration tower I to reflux into the tower, and the other part is cooled to 35-45°C by the top cooler of the concentration tower I and sent to the ammonia water preparation section outside the boundary for recycling; ② The bottom liquid of Concentrator I is cooled by the bottom liquid cooler of Concentrator I and then sent to the middle and lower part of Concentrator II by the bottom liquid delivery pump of Concentrator I, and heated by the reboiler of Concentrator II. The heat source of the reboiler of Concentrator II is provided by the top steam of Concentrator I, and the bottom temperature of Concentrator II is controlled at 80-90℃; the top pressure of Concentrator III is controlled at -60~-20kPaG; the top steam of Concentrator II is used as the heat source of the reboiler of Concentrator III to heat the bottom liquid of Concentrator III and condense the top steam of Concentrator II; the condensate enters the top liquid reflux tank of Concentrator II, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of Concentrator II, a part of it is sent to the top of Concentrator II and refluxed into the tower, and the other part is cooled to 35-45℃ by the top cooler of Concentrator II and then sent to the ammonia preparation section outside the boundary for recycling; the uncondensed gas in the top liquid reflux tank of Concentrator II is condensed by the cryogenic refrigerator, and the gas that has not yet condensed is sent to the vacuum system; ③ The bottom liquid of concentrator II is pumped to the middle of concentrator III by the bottom liquid delivery pump of concentrator II, and heated by the reboiler of concentrator III. The heat source of the reboiler of concentrator III is provided by the top steam of concentrator II, and the bottom temperature of concentrator III is controlled at 55-65℃; the top pressure of concentrator III is controlled at -110~-90kPaG; the top steam of concentrator III is condensed in the top cooler and evaporative condenser of concentrator III, and the uncondensed gas is condensed by the cryogenic refrigerator, and the gas that has not condensed is sent to the vacuum system; the condensate of the top cooler, evaporative condenser and cryogenic refrigerator of concentrator III enters the top liquid reflux tank of concentrator III, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of concentrator III, a part of it is sent to the top of concentrator III to reflux into the tower, and the other part is sent outside for recycling; the bottom liquid of concentrator III is pumped to the brine refining section of chlor-alkali chemical industry by the bottom liquid delivery pump of concentrator III.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The top steam of the concentration tower I described in the present invention can be used as a heat source for the concentration tower II, and the top steam of the concentration tower II can be used as a heat source for the concentration tower III, which greatly reduces the consumption of steam; the purified water from the tops of the concentration towers I, II and III can be used to prepare 20 (wt)% ammonia water, saving water resources and reducing production costs; the ammonia nitrogen content in the bottom liquid of the concentration tower III is low, and can be used for brine refining in chlor-alkali chemical industry; the present invention adopts multiple heat exchange, and all the heat in the system is effectively utilized, avoiding energy waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a simplified flow chart of the present invention.

[0017] Figure 1 1 is the concentration tower I, 2A is the reboiler of the concentration tower I, 2B is the reboiler of the concentration tower II, 2C is the reboiler of the concentration tower III, 3 is the raw material preheater, 4 is the bottom liquid cooler of the concentration tower I, 5A is the bottom liquid delivery pump of the concentration tower I, 5B is the bottom liquid delivery pump of the concentration tower II, 5C is the bottom liquid delivery pump of the concentration tower III, 6A is the top reflux pump of the concentration tower I, 6B is the top reflux pump of the concentration tower II, 6C is the top reflux pump of the concentration tower III, 7A is the top reflux pump of the concentration tower I, 7B is the top liquid reflux tank of concentration tower I, 7C is the top liquid reflux tank of concentration tower II, 8 is concentration tower II, 9 is the tower kettle circulation pump, 10A is the top cooler of concentration tower I, 10B is the top cooler of concentration tower II, 10C is the top cooler of concentration tower III, 11 is concentration tower III, 12 is the deep freezer, 13 is the evaporative condenser, 14 is the raw material delivery pump, 15 is the buffer tank, and 16 is the cooling separator. DETAILED DESCRIPTION

[0018] See attached Figure 1 An embodiment of the present invention provides a device for removing ammonia nitrogen from high-salt wastewater, which includes a buffer tank, a raw material delivery pump, a raw material preheater, a concentration tower I, a concentration tower II, and a concentration tower III connected in sequence.

[0019] Another embodiment is different in that the bottoms of the concentration towers I, II and III are each connected with a corresponding reboiler and bottom liquid delivery pump, and the tops are each connected with a corresponding top liquid reflux tank, top reflux pump and top cooler.

[0020] Another embodiment is different in that the bottom of the concentration tower I is provided with a bottom liquid cooler.

[0021] Another embodiment is different in that the bottoms of the concentration tower II and the concentration tower III are each connected to a corresponding bottom circulation pump.

[0022] Another embodiment is different in that the top liquid reflux tanks of the concentration tower II and the concentration tower III are each connected to a corresponding cryogenic cooler.

[0023] Another embodiment is different in that the top of the concentration tower III is also connected to an evaporative condenser, and the evaporative condenser and the top cooler of the concentration tower III are connected in series or in parallel.

[0024] A venting pipeline connected to a cooling separator is provided at the top of each of the concentration towers I, II and III, so that ammonia gas in the top gas of each tower is cooled and separated and then recycled for the preparation of ammonia water.

[0025] The above-mentioned device for removing ammonia nitrogen from high-salinity wastewater specifically comprises the following process steps: ① The high-salt wastewater from outside the boundary with ammonia nitrogen content of 1000-1500 mg / L, salt content of 8-10 (wt)%, and pH of 10-11 is stabilized and buffered in the buffer tank, and then the pressure is raised to 0.4-0.6 MPaG through the raw material delivery pump, and then preheated by the top cooler of the concentration tower III, the top cooler of the concentration tower II, the top cooler of the concentration tower I, the bottom liquid cooler of the concentration tower I, and the raw material preheater, and then sent to the middle and lower part of the concentration tower I, and heated by the reboiler of the concentration tower I, so that the rising steam and the descending liquid are fully in contact, so as to achieve the separation of water and heavy components. The temperature of the bottom of the concentration tower I is controlled at 100-110°C; the pressure at the top of the concentration tower I is controlled at 10-50kPaG; the top steam of the concentration tower I is used as the heat source of the reboiler of the concentration tower II, heating the bottom liquid of the concentration tower II while condensing the top steam of the concentration tower I; the condensed liquid enters the top liquid reflux tank of the concentration tower I, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of the concentration tower I, a part of it is sent to the top of the concentration tower I to reflux into the tower, and the other part is cooled to 35-45°C by the top cooler of the concentration tower I and sent to the ammonia water preparation section outside the boundary for recycling; ② The bottom liquid of Concentrator I is cooled by the bottom liquid cooler of Concentrator I and then sent to the middle and lower part of Concentrator II by the bottom liquid delivery pump of Concentrator I, and heated by the reboiler of Concentrator II. The heat source of the reboiler of Concentrator II is provided by the top steam of Concentrator I, and the bottom temperature of Concentrator II is controlled at 80-90℃; the top pressure of Concentrator III is controlled at -60~-20kPaG; the top steam of Concentrator II is used as the heat source of the reboiler of Concentrator III to heat the bottom liquid of Concentrator III and condense the top steam of Concentrator II; the condensate enters the top liquid reflux tank of Concentrator II, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of Concentrator II, a part of it is sent to the top of Concentrator II and refluxed into the tower, and the other part is cooled to 35-45℃ by the top cooler of Concentrator II and then sent to the ammonia preparation section outside the boundary for recycling; the uncondensed gas in the top liquid reflux tank of Concentrator II is condensed by the cryogenic refrigerator, and the gas that has not yet condensed is sent to the vacuum system; ③ The bottom liquid of concentrator II is pumped to the middle of concentrator III by the bottom liquid delivery pump of concentrator II, and heated by the reboiler of concentrator III. The heat source of the reboiler of concentrator III is provided by the top steam of concentrator II, and the bottom temperature of concentrator III is controlled at 55-65℃; the top pressure of concentrator III is controlled at -110~-90kPaG; the top steam of concentrator III is condensed in the top cooler and evaporative condenser of concentrator III, and the uncondensed gas is condensed by the cryogenic refrigerator, and the gas that has not condensed is sent to the vacuum system; the condensate of the top cooler, evaporative condenser and cryogenic refrigerator of concentrator III enters the top liquid reflux tank of concentrator III, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of concentrator III, a part of it is sent to the top of concentrator III to reflux into the tower, and the other part is sent outside for recycling; the bottom liquid of concentrator III is pumped to the brine refining section of chlor-alkali chemical industry by the bottom liquid delivery pump of concentrator III.

[0026] The ammonia nitrogen content in the bottom liquid of the concentration tower III is 5 mg / L.

[0027] Another embodiment is different in that the ammonia nitrogen content in the bottom liquid of the concentration tower III is 3 mg / L.

[0028] Another embodiment is different in that the ammonia nitrogen content in the bottom liquid of the concentration tower III is 2 mg / L.

[0029] The bottom liquid of the concentration tower III contains 25 (wt)% salt.

[0030] Another embodiment is different in that the bottom liquid of the concentration tower III contains 27 (wt)% salt.

[0031] Another embodiment is different in that the bottom liquid of the concentration tower III contains 28 (wt)% salt.

[0032] The pH of the bottom liquid of concentration tower III is 6.

[0033] Another embodiment is different in that the pH of the bottom liquid of concentration tower III is 7.

[0034] Another embodiment is different in that the pH of the bottom liquid of concentration tower III is 8.

[0035] The heat of the reboiler of the concentration tower I is provided by 0.4MPaG steam.

[0036] Another embodiment is different in that the heat of the reboiler of the concentration tower I is provided by 1.0 MPaG steam.

[0037] Another embodiment is different in that the heat of the reboiler of the concentration tower I is provided by 2.0 MPaG steam.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for removing ammonia nitrogen from high-salinity wastewater, characterized in that: The device includes a buffer tank, a raw material delivery pump, a raw material preheater, a concentration tower I, a concentration tower II, and a concentration tower III which are connected in sequence; the tower kettles of the concentration tower I, the concentration tower II, and the concentration tower III are respectively connected with corresponding reboilers and tower kettle liquid delivery pumps, and the tower tops are respectively connected with corresponding tower top liquid reflux tanks, tower top reflux pumps, and tower top coolers; the tower top liquid reflux tanks of the concentration tower II and the concentration tower III are respectively connected with corresponding deep coolers; the tower kettle of the concentration tower I is provided with a tower kettle liquid cooler; the tower kettles of the concentration tower II and the concentration tower III are respectively connected with corresponding tower kettle circulation pumps; and a venting pipeline is respectively arranged on the tops of the concentration towers I, the concentration tower II, and the concentration tower III to connect with a cooling separator.

2. The device for removing ammonia nitrogen from high-salinity wastewater according to claim 1, characterized in that: The top of the concentration tower III is also connected to an evaporative condenser, and the evaporative condenser and the top cooler of the concentration tower III are connected in series or in parallel.

3. The device for removing ammonia nitrogen from high-salinity wastewater according to claim 1, characterized in that: The concentration tower I and the concentration tower II are packed towers; the upper section of the concentration tower III is a packed tower, and the lower section is a plate tower.

4. A method for removing ammonia nitrogen from high-salinity wastewater, characterized in that: The method for removing ammonia nitrogen from high-salt wastewater includes the following process steps: ② the high-salt wastewater from outside the boundary is stabilized and buffered in a buffer tank, and then the pressure is raised to 0.4-0.6MPaG by a raw material delivery pump, and then it is preheated by a top cooler of a concentration tower III, a top cooler of a concentration tower II, a top cooler of a concentration tower I, a bottom liquid cooler of a concentration tower I, and a raw material preheater, and then it is sent to the middle and lower part of a concentration tower I, and is heated by a reboiler of a concentration tower I, so that the rising steam and the descending liquid are fully in contact, so as to realize the separation of water and heavy components, and the bottom temperature of the concentration tower I The temperature of the tower is controlled at 100-110℃; the pressure at the top of the concentrator I is controlled at 10-50kPaG; the top steam of the concentrator I is used as the heat source of the reboiler of the concentrator II to heat the bottom liquid of the concentrator II and condense the top steam of the concentrator I; the condensate enters the top liquid reflux tank of the concentrator I, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of the concentrator I, a part of it is sent to the top of the concentrator I to reflux into the tower, and the other part is cooled to 35-45℃ by the top cooler of the concentrator I and sent to the ammonia preparation section outside the boundary for recycling; ② The bottom liquid of Concentrator I is cooled by the bottom liquid cooler of Concentrator I and then sent to the middle and lower part of Concentrator II by the bottom liquid delivery pump of Concentrator I, and heated by the reboiler of Concentrator II. The heat source of the reboiler of Concentrator II is provided by the top steam of Concentrator I, and the bottom temperature of Concentrator II is controlled at 80-90℃; the top pressure of Concentrator III is controlled at -60~-20kPaG; the top steam of Concentrator II is used as the heat source of the reboiler of Concentrator III to heat the bottom liquid of Concentrator III and condense the top steam of Concentrator II; the condensate enters the top liquid reflux tank of Concentrator II, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of Concentrator II, a part of it is sent to the top of Concentrator II and refluxed into the tower, and the other part is cooled to 35-45℃ by the top cooler of Concentrator II and then sent to the ammonia preparation section outside the boundary for recycling; the uncondensed gas in the top liquid reflux tank of Concentrator II is condensed by the cryogenic refrigerator, and the gas that has not yet condensed is sent to the vacuum system; ③ The bottom liquid of concentrator II is pumped to the middle of concentrator III by the bottom liquid delivery pump of concentrator II, and heated by the reboiler of concentrator III. The heat source of the reboiler of concentrator III is provided by the top steam of concentrator II, and the bottom temperature of concentrator III is controlled at 55-65℃; the top pressure of concentrator III is controlled at -110~-90kPaG; the top steam of concentrator III is condensed in the top cooler and evaporative condenser of concentrator III, and the uncondensed gas is condensed by the cryogenic refrigerator, and the gas that has not condensed is sent to the vacuum system; the condensate of the top cooler, evaporative condenser and cryogenic refrigerator of concentrator III enters the top liquid reflux tank of concentrator III, and after being pressurized to 0.3-0.5MPaG by the top reflux pump of concentrator III, a part of it is sent to the top of concentrator III to reflux into the tower, and the other part is sent outside for recycling; the bottom liquid of concentrator III is pumped to the brine refining section of chlor-alkali chemical industry by the bottom liquid delivery pump of concentrator III.

5. The method for removing ammonia nitrogen from high-salinity wastewater according to claim 4, characterized in that: The high-salt wastewater from the outside has an ammonia nitrogen content of 1000-1500 mg / L, a salt content of 8-10 (wt)%, and a pH of 10-11.

6. The method for removing ammonia nitrogen from high-salinity wastewater according to claim 4, characterized in that: The ammonia nitrogen content in the bottom liquid of concentration tower III is ≤5mg / L.

7. The method for removing ammonia nitrogen from high-salinity wastewater according to claim 4, characterized in that: The salt content in the bottom liquid of concentration tower III is 25-28 (wt)%.

8. The method for removing ammonia nitrogen from high-salinity wastewater according to claim 4, characterized in that: The pH of the bottom liquid of concentration tower III is 6-8.

9. The method for removing ammonia nitrogen from high-salinity wastewater according to claim 4, characterized in that: The heat for the reboiler of Concentrator I is provided by 0.4-2.0MPaG steam.

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