Two-stage series connection mvr distillation device and process for residual ammonia water

Abstract

The application discloses a two-stage series MVR distillation device for residual ammonia water, which comprises a distillation tower, the output end of the distillation tower is connected with a heat exchanger through a first pipeline, the output end of the heat exchanger is connected with an ammonia gas condensing cooler through a second pipeline, the top output end of the distillation tower is connected with a secondary steam compressor through a fourth pipeline, the output end of the secondary steam compressor is connected with a reboiler through a fifth pipeline, the output end of the reboiler is connected with a flash tank, the output end of the flash tank is connected with a tertiary steam compressor through a sixth pipeline, and the output end of the tertiary steam compressor is connected with the ammonia gas condensing cooler through a seventh pipeline. The device does not need to provide steam heat source externally, only consumes a small amount of mechanical energy to appropriately increase the pressure and temperature of the secondary steam and the tertiary steam in the device, so that the device has the heat transfer condition of recovering the latent heat, thereby saving a large amount of heat consumption.

Description

Technical Field

[0001] This invention relates to the field of distillation apparatus technology, specifically to a two-stage series MVR distillation apparatus and process for residual ammonia water. Background Technology

[0002] Coal chemical industries such as coking plants and semi-coke plants generate a large amount of residual ammonia water with a concentration of about 0.5% during the production process. This water cannot be treated to meet standards in one go through biological water treatment. It is necessary to reduce the ammonia nitrogen concentration in the residual ammonia water to below 200 mg / L before sending it to a biological treatment station for deep purification.

[0003] Conventional residual ammonia distillation units suffer from high energy consumption; processing 1 ton of residual ammonia requires approximately 160 kg of low-pressure steam. Based on a unit processing 25 t / h of residual ammonia, the steam consumption is estimated at approximately 4 t / h, resulting in high operating costs. Furthermore, insufficient steam supply is a problem during winter in northern regions, worsening the operating conditions for residual ammonia distillation. To address this, a two-stage series MVR distillation unit for residual ammonia is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a two-stage series MVR distillation device and process for residual ammonia water. It adopts a two-stage mechanical compression method to recover the latent heat of secondary steam, and uses a small amount of electrical energy to raise the temperature and pressure of the atmospheric pressure steam with non-recoverable heat in the device, so as to convert it into a heat energy source with high recovery value, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a two-stage series MVR distillation device for residual ammonia water, comprising a distillation column, the output end of which is connected to a heat exchanger via a first pipeline, wherein residual ammonia water from the outside is directly fed into the heat exchanger and preheated to approximately 80°C by the heat exchanger, the output end of which is connected to an ammonia condenser via a second pipeline, wherein the preheated ammonia water enters the ammonia condenser via the second pipeline, and the output end of the ammonia condenser is connected to the top input end of the distillation column via a third pipeline, wherein the ammonia water is heated to approximately 98°C in the ammonia condenser and enters the feed plate position of the distillation column, wherein the ammonia water undergoes distillation in the distillation column, resulting in a significant reduction in ammonia nitrogen concentration, and a portion of the wastewater at the bottom of the column flows through the heat exchanger via the first pipeline and exchanges heat with the incoming ammonia water, and is then discharged after cooling; The top output of the distillation column is connected to a secondary steam compressor via a fourth pipeline. The output of the secondary steam compressor is connected to a reboiler via a fifth pipeline. The top steam of the distillation column enters the secondary steam compressor via the fourth pipeline. After being pressurized and heated by the secondary steam compressor, it enters the reboiler to provide a heat source for the reboiler. The output of the reboiler is connected to a flash tank. The output of the flash tank is connected to a tertiary steam compressor via a sixth pipeline. The output of the tertiary steam compressor is connected to an ammonia condenser via a seventh pipeline. In the reboiler, some of the condensed liquid enters the flash tank. The flashed steam enters the tertiary steam compressor via the sixth pipeline. After being pressurized and heated by the tertiary steam compressor, it enters the ammonia condenser via the seventh pipeline to provide a heat medium for the ammonia condenser.

[0006] Preferably, the heat exchanger is connected to an ammonia inlet pipeline and a bottom wastewater outlet pipeline, the ammonia inlet pipeline and the bottom wastewater outlet pipeline being used for the entry of external residual ammonia and the discharge of bottom wastewater, respectively.

[0007] Preferably, a circulation pipeline connects the distillation column and the reboiler, and a reboiler forced circulation pump is installed on the circulation pipeline. After the ammonia water in the distillation column is distilled, the ammonia nitrogen concentration is greatly reduced. Part of the wastewater at the bottom of the column flows through the first pipeline and exchanges heat with the incoming ammonia water in the heat exchanger, and is then cooled and discharged. The other part of the wastewater is continuously sent into the reboiler by the reboiler forced circulation pump, and after being fully heated, it is converted into steam and enters the bottom of the distillation column, continuously maintaining a high temperature inside the column.

[0008] Preferably, the middle and bottom of the reboiler are respectively connected to a non-condensable gas pipeline and a condensate pipeline, and the output ends of the non-condensable gas pipeline and the condensate pipeline are respectively connected to the upper and middle parts of the flash tank. Some of the non-condensable gas and condensate in the reboiler enter the flash tank through the non-condensable gas pipeline and the condensate pipeline, respectively, with clear layers.

[0009] Preferably, the bottom of the flash tank is connected to the upper input end of the distillation column via a reflux line, and the condensate at the bottom of the flash tank is sent back to the top of the distillation column via a reflux pump along the reflux line to continue participating in the distillation cycle.

[0010] Preferably, the output end of the ammonia condenser is connected to the ammonia water cooler, and the cooled ammonia water can be used as a raw material.

[0011] Another aspect of the present invention is to protect the production process utilizing the aforementioned apparatus, comprising the following steps: the output end of the distillation column is connected to a heat exchanger via a first pipeline, and residual ammonia water from the outside is directly introduced into the heat exchanger and preheated by the heat exchanger; the output end of the heat exchanger is connected to an ammonia condenser via a second pipeline, and the preheated ammonia water enters the ammonia condenser via the second pipeline; the output end of the ammonia condenser is connected to the top input end of the distillation column via a third pipeline, and after being further heated in the ammonia condenser, it enters the feed plate position of the distillation column; after distillation in the distillation column, the ammonia nitrogen concentration is significantly reduced; a portion of the wastewater at the bottom of the column flows through the first pipeline through the heat exchanger and exchanges heat with the incoming ammonia water before being cooled and discharged; the distillation column... The top output end is connected to the secondary steam compressor via the fourth pipeline. The output end of the secondary steam compressor is connected to the reboiler via the fifth pipeline. The steam from the top of the distillation column enters the secondary steam compressor via the fourth pipeline. After being pressurized and heated by the secondary steam compressor, it enters the reboiler to provide a heat source for the reboiler. The output end of the reboiler is connected to the flash tank. The output end of the flash tank is connected to the tertiary steam compressor via the sixth pipeline. The output end of the tertiary steam compressor is connected to the ammonia condenser via the seventh pipeline. In the reboiler, some of the condensed liquid enters the flash tank. The steam from the flash enters the tertiary steam compressor via the sixth pipeline. After being pressurized and heated by the tertiary steam compressor, it enters the ammonia condenser via the seventh pipeline to provide a heat medium for the ammonia condenser.

[0012] Compared with the prior art, the beneficial effects of the present invention are: The method of recovering the latent heat of secondary steam by adopting a two-stage mechanical compression uses a small amount of electrical energy to heat and pressurize the atmospheric steam that cannot recover heat in the device, so as to convert it into a heat energy source with high recovery value. No external steam heat source is required. Only a small amount of mechanical energy is consumed to appropriately pressurize and heat the secondary and tertiary steam in the device, so that it has the heat transfer conditions to recover the latent heat of vaporization, thereby saving a lot of heat consumption. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the device.

[0014] In the diagram: 1-Distillation column, 2-First pipeline, 3-Heat exchanger, 4-Second pipeline, 5-Ammonia condenser / cooler, 6-Third pipeline, 7-Fourth pipeline, 8-Secondary steam compressor, 9-Fifth pipeline, 10-Reboiler, 11-Flash tank, 12-Sixth pipeline, 13-Tertiary steam compressor, 14-Seventh pipeline, 15-Ammonia water inlet pipeline, 16-Bottom wastewater discharge pipeline, 17-Circulation pipeline, 18-Reboiler forced circulation pump, 19-Non-condensable gas pipeline, 20-Condensate pipeline, 21-Reflux pipeline, 22-Ammonia water cooler. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only based on a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example: Please see Figure 1 The present invention provides the following technical solution: a two-stage series MVR distillation device for residual ammonia water, comprising a distillation column 1, the output end of the distillation column 1 being connected to a heat exchanger 3 via a first pipeline 2, the residual ammonia water from the outside being directly fed into the heat exchanger 3 and preheated to about 80°C by the heat exchanger 3, the output end of the heat exchanger 3 being connected to an ammonia condenser 5 via a second pipeline 4, the preheated ammonia water entering the ammonia condenser 5 via the second pipeline 4, the output end of the ammonia condenser 5 being connected to the top input end of the distillation column 1 via a third pipeline 6, the ammonia water being heated to about 98°C in the ammonia condenser 5 and entering the feed plate position of the distillation column 1, the ammonia water undergoing distillation in the distillation column 1, resulting in a significant reduction in ammonia nitrogen concentration, and a portion of the wastewater at the bottom of the column flowing through the first pipeline 2 through the heat exchanger 3 and exchanging heat with the incoming ammonia water, being cooled and discharged; The top output of the distillation column 1 is connected to the secondary steam compressor 8 via the fourth pipeline 7. The output of the secondary steam compressor 8 is connected to the reboiler 10 via the fifth pipeline 9. The steam from the top of the distillation column 1 enters the secondary steam compressor 8 via the fourth pipeline 7. After being pressurized and heated by the secondary steam compressor 8, it enters the reboiler 10 to provide a heat source for the reboiler 10. The output of the reboiler 10 is connected to the flash tank 11. The output of the flash tank 11 is connected to the tertiary steam compressor 13 via the sixth pipeline 12. The output of the tertiary steam compressor 13 is connected to the ammonia condenser 5 via the seventh pipeline 14. In the reboiler 10, some of the condensed liquid enters the flash tank 11. The steam from the flash enters the tertiary steam compressor 13 via the sixth pipeline 12. After being pressurized and heated by the tertiary steam compressor 13, it enters the ammonia condenser 5 via the seventh pipeline 14 to provide a heat medium for the ammonia condenser 5.

[0017] In a conventional residual ammonia distillation process with a capacity of 25t / h, the thermal medium alone consumes more than 4t / h of steam. Assuming a steam price of 200 yuan, the cost of steam consumption is 800 yuan / hour.

[0018] Using the above-mentioned device, processing 25t / h of residual ammonia water consumes only about 300kwh of electricity to meet all the heat demand, with a cost of about 180 yuan / hour.

[0019] This device requires no external steam heat source. It only consumes a small amount of mechanical energy to appropriately pressurize and heat the secondary and tertiary steam inside the device, enabling it to have the heat transfer conditions to recover the latent heat of vaporization, thereby saving a lot of heat consumption.

[0020] Specifically, the heat exchanger 3 is connected to an ammonia inlet pipeline 15 and a bottom wastewater outlet pipeline 16. The ammonia inlet pipeline 15 and the bottom wastewater outlet pipeline 16 are used for the entry of external residual ammonia and the discharge of bottom wastewater, respectively.

[0021] Specifically, a circulation pipeline 17 is connected between the distillation column 1 and the reboiler 10. A reboiler forced circulation pump 18 is installed on the circulation pipeline 17. After the ammonia water in the distillation column 1 is distilled, the ammonia nitrogen concentration is greatly reduced. Part of the wastewater at the bottom of the column flows through the first pipeline 2 and passes through the heat exchanger 3 to exchange heat with the incoming ammonia water, and is then cooled and discharged. The other part of the wastewater is continuously sent into the reboiler 10 by the reboiler forced circulation pump 18. After being fully heated, it is converted into steam and enters the bottom of the distillation column 1, continuously maintaining the high temperature inside the column.

[0022] Specifically, the middle and bottom of the reboiler 10 are respectively connected to a non-condensable gas pipeline 19 and a condensate pipeline 20. The output ends of the non-condensable gas pipeline 19 and the condensate pipeline 20 are respectively connected to the upper and middle parts of the flash tank 11. Some of the non-condensable gas and condensate in the reboiler 10 enter the flash tank 11 through the non-condensable gas pipeline 19 and the condensate pipeline 20, respectively, with clear layers.

[0023] Specifically, the bottom of the flash tank 11 is connected to the upper input end of the distillation column 1 via the reflux line 21, and the condensate at the bottom of the flash tank 11 is sent back to the top of the distillation column 1 via the reflux pump along the reflux line 12 to continue participating in the distillation cycle.

[0024] Specifically, the output end of the ammonia condenser 5 is connected to the ammonia water cooler 22, and the cooled ammonia water can be used as a raw material.

[0025] Working principle: The output end of distillation column 1 is connected to heat exchanger 3 via the first pipeline 2. Residual ammonia water from the outside is directly fed into heat exchanger 3 and preheated to about 80°C. The output end of heat exchanger 3 is connected to ammonia condenser 5 via the second pipeline 4. The preheated ammonia water enters ammonia condenser 5 via the second pipeline 4. The output end of ammonia condenser 5 is connected to the top input end of distillation column 1 via the third pipeline 6. The ammonia water is heated to about 98°C in ammonia condenser 5 and enters the feed plate of distillation column 1. After distillation in distillation column 1, the ammonia nitrogen concentration is significantly reduced. Part of the wastewater at the bottom of the column flows through the first pipeline 2 and passes through heat exchanger 3 to exchange heat with the incoming ammonia water, and is then cooled and discharged. The top output end of distillation column 1 is connected to secondary steam compressor 8 via the fourth pipeline 7. Next, the output end of the secondary steam compressor 8 is connected to the reboiler 10 through the fifth pipeline 9. The steam from the top of the distillation column 1 enters the secondary steam compressor 8 through the fourth pipeline 7. After being pressurized and heated by the secondary steam compressor 8, it enters the reboiler 10 to provide a heat source for the reboiler 10. The output end of the reboiler 10 is connected to the flash tank 11. The output end of the flash tank 11 is connected to the tertiary steam compressor 13 through the sixth pipeline 12. The output end of the tertiary steam compressor 13 is connected to the ammonia condenser 5 through the seventh pipeline 14. In the reboiler 10, some of the condensed liquid enters the flash tank 11. The steam from the flash enters the tertiary steam compressor 13 through the sixth pipeline 12. After being pressurized and heated by the tertiary steam compressor 13, it enters the ammonia condenser 5 through the seventh pipeline 14 to provide a heat medium for the ammonia condenser 5.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0027] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A two-stage series MVR distillation apparatus for residual aqueous ammonia, comprising a distillation column (1), characterized in that: The output end of the distillation column (1) is connected to the heat exchanger (3) through the first pipeline (2). The output end of the heat exchanger (3) is connected to the ammonia condenser (5) through the second pipeline (4). The output end of the ammonia condenser (5) is connected to the top input end of the distillation column (1) through the third pipeline (6). The top output end of the distillation column (1) is connected to the secondary steam compressor (8) through the fourth pipeline (7). The output end of the secondary steam compressor (8) is connected to the reboiler (10) through the fifth pipeline (9). The output end of the reboiler (10) is connected to the flash tank (11). The output end of the flash tank (11) is connected to the tertiary steam compressor (13) through the sixth pipeline (12). The output end of the tertiary steam compressor (13) is connected to the ammonia condenser (5) through the seventh pipeline (14).

2. The two-stage series MVR distillation apparatus for residual ammonia water according to claim 1, characterized in that: The heat exchanger (3) is connected to an ammonia inlet pipeline (15) and a wastewater outlet pipeline (16) at the bottom of the tower.

3. The two-stage series MVR distillation apparatus for residual ammonia water according to claim 2, characterized in that: A circulation pipeline (17) is connected between the distillation column (1) and the reboiler (10), and a reboiler forced circulation pump (18) is installed on the circulation pipeline (17).

4. The two-stage series MVR distillation apparatus for residual ammonia water according to claim 3, characterized in that: The reboiler (10) is connected to a non-condensable gas line (19) and a condensate line (20) at its middle and bottom, respectively. The output ends of the non-condensable gas line (19) and the condensate line (20) are connected to the upper and middle parts of the flash tank (11), respectively.

5. A two-stage series MVR distillation apparatus for residual ammonia water according to claim 4, characterized in that: The bottom of the flash tank (11) is connected to the upper input end of the distillation column (1) via a reflux line (21).

6. A two-stage series MVR distillation apparatus for residual ammonia water according to claim 5, characterized in that: The output end of the ammonia condenser (5) is connected to the ammonia water cooler (22).

7. The manufacturing process of the apparatus as described in claim 1, characterized in that: The output end of the distillation tower (1) is connected to the heat exchanger (3) through the first pipeline (2). The residual ammonia water from the outside is directly fed into the heat exchanger (3) and preheated by the heat exchanger (3). The output end of the heat exchanger (3) is connected to the ammonia condenser (5) through the second pipeline (4). The preheated ammonia water enters the ammonia condenser (5) through the second pipeline (4). The output end of the ammonia condenser (5) is connected to the top input end of the distillation tower (1) through the third pipeline (6). After being further heated in the ammonia condenser (5), it enters the feed plate position of the distillation tower (1). After distillation in the distillation tower (1), the ammonia nitrogen concentration is greatly reduced. A portion of the wastewater at the bottom of the tower flows through the first pipeline (2) through the heat exchanger (3) and exchanges heat with the incoming ammonia water before being cooled and discharged. The top output end of the distillation tower (1) is connected to the secondary steam compressor (8) through the fourth pipeline (7). The output end of 8) is connected to the reboiler (10) through the fifth pipeline (9). The steam at the top of the distillation column (1) enters the secondary steam compressor (8) through the fourth pipeline (7). After being pressurized and heated by the secondary steam compressor (8), it enters the reboiler (10) to provide a heat source for the reboiler (10). The output end of the reboiler (10) is connected to the flash tank (11). The output end of the flash tank (11) is connected to the tertiary steam compressor (13) through the sixth pipeline (12). The output end of the tertiary steam compressor (13) is connected to the ammonia condenser (5) through the seventh pipeline (14). In the reboiler (10), some of the condensed liquid enters the flash tank (11). The steam that flashes out enters the tertiary steam compressor (13) through the sixth pipeline (12). After being pressurized and heated by the tertiary steam compressor (13), it enters the ammonia condenser (5) through the seventh pipeline (14) to provide a heat medium for the ammonia condenser (5).

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