Energy-saving process and device for recovering high-purity ammonia from wastewater

Abstract

The present application relates to a kind of energy-saving process technology and device for recovering high-purity ammonia from wastewater, belonging to the field of wastewater treatment in environmental protection.It comprises a deamination tower, a preheater, a wastewater cooler, a heat supplementing and heat exchanging device, a compressor and a throttle valve.The deamination tower comprises a heating section, a deamination section, a condensation section, an ammonia washing section and a purification section.The heating section is provided with compressor working medium inlets and outlets, the deamination section is provided with a wastewater mother liquor inlet, the condensation section is provided with compressor working medium inlets and outlets, the ammonia washing section is provided with a pure water inlet and an ammonia water outlet, and the purification section is provided with a dilute acid aqueous solution inlet and a salt solution outlet.The low-grade waste heat is converted into high-grade heat source by using the compressor, instead of fresh steam, to achieve the purpose of energy saving.The problem of existing technology that tail gas needs to be treated again is solved, tail gas zero emission is realized, and co-production of ammonia water and ammonium salt is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection, in particular to a process and device for recovering high-purity ammonia from wastewater. BACKGROUND

[0002] Various types of wastewater are generated in daily life and industrial production, most of which contain ammonia nitrogen, which can be mainly divided into urban life ammonia nitrogen wastewater, agricultural ammonia nitrogen wastewater and industrial ammonia nitrogen wastewater. Industrial ammonia nitrogen wastewater is the most serious source of wastewater, with high concentration and large volume. If ammonia nitrogen wastewater is not treated or treated substandardly and directly discharged, it will cause serious environmental harm, destroy ecological safety and even crisis. The state also has strict standards for the discharge of ammonia nitrogen in wastewater.

[0003] There are various methods for treating ammonia nitrogen wastewater, such as biochemical method, air stripping method, breakpoint chlorination method, chemical precipitation method, etc., but actual industrial application is limited, and most of them are only suitable for the treatment of low-concentration ammonia nitrogen wastewater. The method of steam stripping ammonia is currently widely used, especially for treating large-volume and high-concentration ammonia nitrogen wastewater. The ammonia stripping process can be divided into direct steam heating and indirect steam heating processes according to energy sources.

[0004] At present, ammonia nitrogen wastewater has complex composition, high salt content and easy scaling and plugging, and the ammonia content is unstable. Therefore, the traditional ammonia stripping method for treating ammonia nitrogen wastewater has the following defects: 1) the treatment energy consumption is relatively high, and the steam consumption is often as high as 200-300 kg / t of wastewater; 2) the ammonia water concentration obtained is unstable, and the product cannot be sold outside due to large fluctuations in ammonia water concentration; 3) ammonia gas is easy to escape to produce tail gas, which needs to be further treated.

[0005] In terms of energy saving, although multi-effect ammonia stripping can save part of the energy consumption, the equipment is more and the production process is more complex. The existing schemes for treating ammonia nitrogen wastewater by using heat pump technology all directly recover the heat of ammonia-containing steam, and the temperature difference between the recovered heat and the required heat is relatively large, which requires a relatively high heat pump device and a relatively large investment. SUMMARY

[0006] The purpose of the present application is to provide an energy-saving process and device for recovering high-purity ammonia from wastewater, which realizes energy saving by recovering the heat of water vapor in ammonia-containing steam. The process and device can produce ammonia water with stable concentration, realize co-production of ammonia water and ammonium salt, realize zero ammonia gas escape, and do not need subsequent tail gas treatment.

[0007] To achieve the above purpose, the present application provides the following technical solutions:

[0008] An energy-saving process for recovering high-purity ammonia from wastewater, comprising the following steps:

[0009] After the waste water mother liquor is adjusted to pH 11-13 by alkali liquor, it is preheated by a preheater and then enters the middle of the deamination tower to be in countercurrent contact with the ammonia-containing water vapor from the bottom of the tower to constantly enrich ammonia; the liquid at the bottom of the tower is heated by the working medium of the heat side compressor, thereby generating steam; the ammonia-enriched water vapor enters the heat side of the heat exchange tube in the tower and is cooled by the working medium of the cold side compressor, thereby condensing the water vapor in the ammonia gas and further enriching the ammonia gas; the enriched ammonia gas is washed by pure water, and high-concentration ammonia water is collected at the upper part of the deamination tower; the escaped ammonia gas is sealed by dilute acid aqueous solution at the top of the tower, thereby producing ammonium salt aqueous solution at the top of the deamination tower to achieve zero emission of tail gas; the waste water after deamination is collected at the bottom of the deamination tower, cooled by a cooler, and then discharged from the device.

[0010] After the working medium steam at the heat side of the heat exchange tube at the bottom of the tower is heat-exchanged with the liquid at the cold side of the tower, working medium liquid is generated; the working medium liquid enters the cold side of the heat exchange tube in the tower after passing through a throttle valve to cool the ammonia-containing steam at the heat side of the tube; the working medium recovers the latent heat of the water vapor in the ammonia-containing steam, is heated and gasified, and then enters the cold side of the heat recovery heat exchanger to be heat-exchanged with the heat medium at the heat side of the heat exchanger, thereby producing superheated working medium steam; the superheated working medium steam is pressurized by a compressor into high-pressure steam, and then heats the liquid at the cold side of the heat exchange tube at the bottom of the tower.

[0011] Further, the working medium liquid of the compressor passes through a throttle valve and is heat-exchanged with the waste water mother liquor at the heat side and the cold side of a preheater.

[0012] Further, the working medium of the compressor passes through the cold side of the heat exchange tube in the tower and is further heat-exchanged with the waste water at the cold side and the heat side of a waste water cooler.

[0013] Further, the working medium liquid of the compressor is water or R22 or R32 or R134, and the corresponding working medium steam of the compressor is water vapor or R22 steam or R32 steam or R134 steam.

[0014] Further, the heat medium at the heat side of the heat recovery heat exchanger is steam or hot water or heat conducting oil.

[0015] Further, the dilute acid aqueous solution is dilute sulfuric acid aqueous solution or dilute hydrochloric acid aqueous solution or carbonic acid aqueous solution or phosphoric acid aqueous solution.

[0016] An energy-saving device for recovering high-purity ammonia from waste water, comprising a deamination tower, a preheater, a waste water cooler, a heat recovery heat exchanger, a compressor, and a throttle valve.

[0017] The deamination tower comprises a heating section, a deamination section, a condensation section, an ammonia washing section, and a purification section; the heating section is provided with compressor working medium inlets and outlets, the deamination section is provided with a waste water mother liquor inlet, the condensation section is provided with compressor working medium inlets and outlets, the ammonia washing section is provided with a pure water inlet and an ammonia water outlet, the purification section is provided with a dilute acid aqueous solution inlet and a salt solution outlet, and the bottom of the deamination tower is provided with a waste water outlet.

[0018] Furthermore, the hot side of the deammoniation tower heating section, the throttling valve, the hot side of the preheater, the cold side of the deammoniation tower condensing section, the cold side of the wastewater cooler, the cold side of the supplementary heat exchanger, and the compressor are connected by working fluid pipelines to form a working fluid circulation loop.

[0019] Furthermore, the ammonia removal section of the ammonia removal tower is equipped with ammonia removal mass transfer internal components such as trays or packing.

[0020] Furthermore, the ammonia washing section of the deammoniation tower is equipped with ammonia washing mass transfer internal components such as trays or packing.

[0021] Furthermore, the purification section of the ammonia removal tower is equipped with a dilute acid aqueous solution liquid seal device.

[0022] Furthermore, an ammonia water extraction device is installed at the bottom of the ammonia washing section of the deammoniation tower.

[0023] The energy-saving process and apparatus for recovering high-purity ammonia from wastewater described in this invention have the following beneficial effects:

[0024] (1) The present invention discloses an energy-saving process method and apparatus for recovering high-purity ammonia from wastewater. A working fluid circulation loop is formed between the hot side of the heating section of the ammonia removal tower, the hot side of the preheater, the cold side of the condensing section of the ammonia removal tower, the cold side of the wastewater cooler, and the cold side of the supplementary heat exchanger. The low-grade heat energy of water vapor on the hot side of the condensing section of the ammonia removal tower is converted into high-grade heat energy, which provides a heat source for the heating section of the ammonia removal tower, replacing the use of a large amount of fresh steam. At the same time, the condensing section of the ammonia removal tower no longer needs a refrigerant, and the overall energy consumption is significantly reduced.

[0025] (2) The present invention discloses an energy-saving process method and apparatus for recovering high-purity ammonia from wastewater. The working fluid obtains water vapor heat energy in the condensation section in the middle of the deammoniation tower. The heat energy has a relatively high grade and a small temperature difference with the heat source required by the heating section at the bottom of the deammoniation tower, which greatly reduces the investment in the compressor.

[0026] (3) The present invention discloses an energy-saving process and apparatus for recovering high-purity ammonia from wastewater. The ammonia washing section of the ammonia removal tower uses pure water to wash ammonia, which has a high ammonia recovery rate and can obtain ammonia water with a stable concentration. The ammonia water concentration can be adjusted between 5-60%.

[0027] (4) The present invention discloses an energy-saving process and device for recovering high-purity ammonia from wastewater. The purification section of the ammonia removal tower is sealed with dilute acid aqueous solution to achieve zero ammonia escape and zero tail gas emission, and no further tail gas treatment is required.

[0028] (5) The present invention discloses an energy-saving process and apparatus for recovering high-purity ammonia from wastewater, which can realize the co-production of ammonia water and ammonium salt, and can switch products according to production needs.

[0029] (6) The present invention discloses an energy-saving process and apparatus for recovering high-purity ammonia from wastewater. It only requires one ammonia removal tower to achieve an ammonia nitrogen content of ≤10mg / L in the wastewater after ammonia removal, which is lower than the national first-class emission standard. At the same time, it can achieve the co-production of ammonia water and ammonium salt, and the tail gas has zero emission. The equipment is small, the process is simple, the investment is small, the benefits are high, and the applicability is wide. Attached Figure Description

[0030] To further illustrate the present invention, the following figures are provided:

[0031] Figure 1 This is a schematic diagram of the process flow of Embodiment 1 of the present invention.

[0032] Figure 2 This is a schematic diagram of the process flow of Embodiment 2 of the present invention.

[0033] Figure 3 This is a schematic diagram of the process flow of Embodiment 3 of the present invention.

[0034] Explanation of reference numerals in the attached diagram: 1 is the mother liquor feed pump; 2 is the preheater; 3 is the throttle valve; 4 is the wastewater discharge pump; 5 is the wastewater cooler; 6 is the supplementary heat exchanger; 7 is the compressor; 8 is the heating heat exchange tube; 9 is the ammonia removal mass transfer internal component tray or packing; 10 is the condensation heat exchange tube; 11 is the ammonia water extraction device; 12 is the ammonia washing mass transfer internal component tray or packing; 13 is the liquid seal device; 14 is the ammonia removal tower; LS is low-pressure steam; SC is condensate; HWS is hot water supply; HWR is hot water return; N2 is nitrogen. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1

[0036] Reference Figure 1 This embodiment provides an energy-saving process and apparatus for recovering high-purity ammonia from wastewater. The apparatus includes a mother liquor feed pump 1, a preheater 2, a throttle valve 3, a wastewater discharge pump 4, a wastewater cooler 5, a supplementary heat exchanger 6, a compressor 7, and an ammonia removal tower 14.

[0037] The ammonia removal tower 14 is a single vertical tower body, comprising heating heat exchange tubes 8, ammonia removal mass transfer internal components 9, condensation heat exchange tubes 10, ammonia water extraction device 11, ammonia washing mass transfer internal components 12, and a purification section liquid seal device 13. The heating section is equipped with a compressor working fluid inlet and outlet, the ammonia removal section is equipped with a wastewater mother liquor inlet, the condensation section is equipped with a compressor working fluid inlet and outlet, the ammonia washing section is equipped with a pure water inlet and an ammonia water outlet, and the purification section is equipped with a dilute acid solution inlet and a salt solution outlet.

[0038] The deammonia removal tower 14 is connected to the heating heat exchange tube 8 (hot side), throttle valve 3, preheater 2 (hot side), deammonia removal tower condenser heat exchange tube 10 (cold side), wastewater cooler 5 (cold side), supplementary heat exchanger 6 (cold side), and compressor by a working fluid pipeline, forming a working fluid circulation loop.

[0039] The energy-saving process method provided in this embodiment includes the following steps: The wastewater mother liquor, after its pH is adjusted to 11-13 by alkaline solution, is pressurized by mother liquor feed pump 1 and enters the cold side of preheater 2. It is then preheated by the compressor working fluid on the hot side before entering the wastewater mother liquor inlet of deammoniation tower 14. The wastewater after ammonia nitrogen removal is discharged from the bottom of deammoniation tower 14, pressurized by wastewater discharge pump 4, and sent to the hot side of wastewater cooler 5. It is then cooled by the compressor working fluid on the hot side before being discharged from the device. Pure water enters the pure water inlet of deammoniation tower 14 and comes into countercurrent contact with high-concentration ammonia gas on the ammonia washing mass transfer internal component 12, producing a stable concentration of ammonia water, which is collected from the ammonia water outlet. A dilute acid aqueous solution enters the dilute acid aqueous solution inlet of deammoniation tower 14 and comes into contact with the escaping tail gas on the purification section liquid seal device 13, ensuring zero tail gas emissions. Simultaneously, ammonium salt is collected at the salt solution outlet.

[0040] The high-pressure working fluid vapor from the compressor 7 outlet enters the hot side of the heating heat exchange tube 8 of the ammonia removal tower 14, heating the liquid in the bottom of the tower and condensing the working fluid itself. The condensed working fluid liquid is then throttled and depressurized by the throttling valve 3 before entering the hot side of the preheater 2 to heat the wastewater mother liquor on the cold side, further cooling the working fluid. The cooled working fluid then enters the cold side of the condensation heat exchange tube 10 of the ammonia removal tower 14, where it is heated by water vapor from the ammonia vapor. The heated working fluid then enters the cold side of the wastewater cooler 5 to cool the wastewater, further heating and vaporizing the working fluid. Finally, the working fluid enters the cold side of the supplementary heat exchanger 6, where it is further heated by a heat medium before entering the compressor for pressurization, becoming high-pressure working fluid vapor. This forms the compressor working fluid cycle.

[0041] In this embodiment, the wastewater mother liquor is ternary ammonia nitrogen wastewater from the lithium battery new material industry, with a treatment volume of 150m³. 3 The ammonia nitrogen content is 10,000~30,000 mg / L per hour. After treatment by the method and device described in this invention, ammonia water with a stable concentration of 25% wt is produced. The ammonia nitrogen content in the wastewater after ammonia removal is 6.3 mg / L, and the wastewater meets the national first-class discharge standard.

[0042] In this embodiment, the compressor working fluid circulation makes full use of waste heat, requiring only the supplementary heat exchanger 6 to generate a heat source, thus saving a significant amount of fresh steam and eliminating the need for refrigerant. Compared to the traditional ammonia stripping process, this method saves 178.1 kg of steam per ton of wastewater mother liquor, while the power consumption of the compressor per ton of wastewater mother liquor is only 2.3 kWh, resulting in a substantial reduction in overall energy consumption.

[0043] After the compressor working fluid is further cooled by the preheater 2, it enters the condenser heat exchange tube 10, which increases the temperature difference between the hot and cold sides of the condenser heat exchange tube 10, reduces the heat transfer area of ​​the condenser heat exchange tube 10, and reduces equipment investment.

[0044] The compressor working fluid is further heated by the wastewater cooler 5 and the supplementary heat exchanger 6 before entering the compressor 7, which increases the stability of the compressor operation and greatly improves the operating efficiency of the compressor.

[0045] Because the saturated vapor pressure of ammonia is much higher than that of water at the same temperature, ammonia easily escapes. Therefore, in traditional ammonia stripping processes, when the ammonia concentration reaches 15% or higher, the escape of ammonia can easily lead to pressure fluctuations in the ammonia stripping tower, resulting in unstable operation and the generation of large amounts of tail gas that require treatment. In this embodiment, dilute acid is used to control ammonia escape, resulting in very stable operation of the ammonia stripping tower, which can stably produce high-concentration ammonia water with zero tail gas emissions. Furthermore, the production ratio of ammonia water and ammonium salts can be adjusted by changing the amounts of pure water and dilute acid, according to product requirements, thus achieving product structure adjustment for ammonia water and ammonium salts. Example 2

[0046] Reference Figure 2 This embodiment provides an energy-saving process and apparatus for recovering high-purity ammonia from wastewater. The apparatus includes a mother liquor feed pump 1, a preheater 2, a throttling valve 3, a wastewater discharge pump 4, a supplementary heat exchanger 6, a compressor 7, and an ammonia removal tower 14. The preheater 2 also serves as a wastewater cooler 5.

[0047] The internal structure of the deammoniation tower 14 is the same as that in Example 1.

[0048] The heating heat exchange tube 8 (hot side), throttle valve 3, condensing heat exchange tube 10 (cold side), supplementary heat exchanger 6 (cold side), and compressor of the deammoniation tower 14 are connected by a working fluid pipeline to form a working fluid circulation loop.

[0049] The energy-saving process method provided in this embodiment includes the following steps: The wastewater mother liquor, after its pH is adjusted to 11-13 by alkaline solution, is pressurized by mother liquor feed pump 1 and enters the cold side of preheater 2. It is preheated by the bottom wastewater on the hot side before entering the wastewater mother liquor inlet of the ammonia removal tower 14. The wastewater after ammonia nitrogen removal is discharged from the bottom of the ammonia removal tower 14, pressurized by wastewater discharge pump 4, and sent to the hot side of wastewater cooler 5, where it is cooled by the wastewater mother liquor before being discharged from the device. Pure water enters the pure water inlet of the ammonia removal tower 14 and comes into countercurrent contact with high-concentration ammonia gas on the ammonia washing mass transfer internal component 12, producing a stable concentration of ammonia water, which is then collected from the ammonia water outlet. Dilute acid aqueous solution enters the dilute acid aqueous solution inlet of the ammonia removal tower 14 and comes into contact with the escaping tail gas on the purification section liquid seal device 13, ensuring zero tail gas emissions. Simultaneously, ammonium salt is collected at the salt solution outlet.

[0050] The high-pressure working fluid vapor from the compressor 7 outlet enters the hot side of the heating heat exchange tube 8 of the ammonia removal tower 14, heating the liquid in the bottom of the tower, where the working fluid itself condenses. The condensed working fluid liquid is then throttled and depressurized by the throttling valve 3 before entering the cold side of the condensation heat exchange tube 10 of the ammonia removal tower 14. The condenser contains water vapor from the ammonia vapor, further heating the working fluid. The heated working fluid then enters the cold side of the supplementary heat exchanger 6, where it is heated by a heat medium until it superheats and vaporizes. The resulting working fluid vapor then enters the compressor for pressurization, becoming high-pressure working fluid vapor. This forms the compressor working fluid cycle.

[0051] In this embodiment, the wastewater mother liquor is ammonia nitrogen wastewater from the sodium ammonia production unit, with a treatment capacity of 125m³. 3 The ammonia nitrogen content is 8000~25000 mg / L per hour. After treatment by the method and device described in this invention, ammonia water with a stable concentration of 18% wt is produced. The ammonia nitrogen content in the wastewater after ammonia removal is 4.7 mg / L, and the wastewater meets the national first-class discharge standard.

[0052] In this embodiment, the working fluid circulation converts the low-grade heat energy in the condenser heat exchanger tube 10 into high-grade heat energy through a compressor. This high-grade heat energy is used to heat the bottom liquid of the deammoniation tower 14 on the hot side of the heat exchanger tube 8, replacing the fresh steam required in the traditional method. This achieves energy saving, conserving a significant amount of fresh steam, and eliminates the need for refrigerant on the cold side of the condenser heat exchanger tube 10. The only location requiring a heat source in this embodiment is the hot side of the supplementary heat exchanger, which uses 90°C hot water as the heat source.

[0053] Compared to traditional ammonia stripping processes, this embodiment eliminates the need for steam and refrigerant, requiring only hot water and electricity, thus replacing expensive steam with inexpensive hot water and electricity. It saves 237.9 kg of steam per ton of wastewater mother liquor treated, while the power consumption of the compressor required per ton of wastewater mother liquor is only 2.1 kWh, resulting in a significant reduction in overall energy consumption and substantial savings in operating costs.

[0054] Similar to Example 1, this example uses dilute acid to control ammonia escape, ensuring stable operation of the ammonia removal tower and stable production of high-concentration ammonia water with zero tail gas emissions. Simultaneously, it enables the co-production of ammonia water and ammonium salts. Example 3

[0055] Reference Figure 3 This embodiment provides an energy-saving process and apparatus for recovering high-purity ammonia from wastewater. The apparatus includes a mother liquor feed pump 1, a preheater 2, a throttle valve 3, a wastewater discharge pump 4, a wastewater cooler 5, a compressor 7, and an ammonia removal tower 14.

[0056] The ammonia removal tower 14 is a single vertical tower body, comprising heating heat exchange tubes 8, ammonia removal mass transfer internal components 9, condensation heat exchange tubes 10, ammonia water extraction device 11, ammonia washing mass transfer internal components 12, and a purification section liquid seal device 13. A fresh steam inlet is located at the bottom of the ammonia removal tower; the heating section has a compressor working fluid inlet and outlet; the ammonia removal section has a wastewater mother liquor inlet; the condensation section has a compressor working fluid inlet and outlet; the ammonia washing section has a pure water inlet and an ammonia water outlet; and the purification section has a dilute acid solution inlet and a salt solution outlet.

[0057] The heating heat exchange tube 8 (hot side), throttle valve 3, preheater 2 (hot side), condenser heat exchange tube 10 (cold side), wastewater cooler 5 (cold side), and compressor of the deammoniation tower 14 are connected by a working fluid pipeline to form a working fluid circulation loop.

[0058] The energy-saving process method provided in this embodiment includes the following steps: The wastewater mother liquor, after its pH is adjusted to 11-13 by alkaline solution, is pressurized by mother liquor feed pump 1 and enters the cold side of preheater 2. It is preheated by the compressor working fluid on the hot side and then enters the wastewater mother liquor inlet of deammoniation tower 14. Fresh steam is introduced into the bottom of deammoniation tower 14. The wastewater after ammonia nitrogen removal is discharged from the bottom of deammoniation tower 14, pressurized by wastewater discharge pump 4, and sent to the hot side of wastewater cooler 5. It is cooled by the compressor working fluid on the hot side and then discharged from the device. Pure water enters the pure water inlet of deammoniation tower 14 and comes into countercurrent contact with high-concentration ammonia gas on the ammonia washing mass transfer internal component 12, producing a stable concentration of ammonia water, which is collected from the ammonia water outlet. Dilute acid aqueous solution enters the dilute acid aqueous solution inlet of deammoniation tower 14 and comes into contact with the escaping tail gas on the purification section liquid seal device 13, ensuring zero tail gas emission. Simultaneously, ammonium salt is collected at the salt solution outlet.

[0059] The high-pressure working fluid vapor from the compressor 7 outlet enters the hot side of the heating heat exchange tube 8 of the ammonia removal tower 14, heating the liquid in the bottom of the tower, where the working fluid itself is condensed. The condensed working fluid liquid is then throttled and depressurized by the throttling valve 3 before entering the hot side of the preheater 2 to heat the wastewater mother liquor on the cold side, further cooling the working fluid. The cooled working fluid then enters the cold side of the condensation heat exchange tube 10 of the ammonia removal tower 14, where it is heated by the water vapor in the ammonia vapor. The heated working fluid then enters the cold side of the wastewater cooler 5 to cool the wastewater on the cold side, further heating and vaporizing the working fluid. The working fluid vapor then enters the compressor for pressurization, becoming high-pressure working fluid vapor. This forms the compressor working fluid cycle.

[0060] In this embodiment, the wastewater mother liquor is ammonia nitrogen wastewater from landfill leachate, with a treatment volume of 30m³. 3 The ammonia nitrogen content is 2000~8000 mg / L per hour. After treatment by the method and device described in this invention, ammonia water with a stable concentration of 10% wt is produced. The ammonia nitrogen content in the wastewater after ammonia removal is 4.7 mg / L, and the wastewater meets the national first-class discharge standard.

[0061] In this embodiment, the working fluid circulation converts the low-grade heat energy of the condenser heat exchanger 10 and wastewater cooler 5 into high-grade heat energy through a compressor, which is used to heat the heat exchanger 8 and preheater 2, saving fresh steam consumption. Furthermore, the condenser heat exchanger 10 and wastewater cooler 5 no longer require refrigerant. Compared with the traditional ammonia stripping process, this method saves 135.2 kg of steam per ton of wastewater mother liquor treated, while the power consumption of the compressor required per ton of wastewater mother liquor is only 1.9 kWh. It stably produces high-concentration ammonia water, achieves zero tail gas emissions, and significantly reduces overall energy consumption. Simultaneously, it enables the co-production of ammonia water and ammonium salts.

[0062] The preferred embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention patent.

Claims

1. An energy-saving process for recovering high-purity ammonia from wastewater, characterized in that, Includes the following steps: The ammonia stripping tower consists of a heating section, an ammonia stripping section, a condensation section, an ammonia washing section, and a purification section from bottom to top. The heating section is equipped with the compressor working fluid inlet and outlet, the ammonia stripping section is equipped with the wastewater mother liquor inlet, the condensation section is equipped with the compressor working fluid inlet and outlet, the ammonia washing section is equipped with the pure water inlet and the ammonia water outlet, the purification section is equipped with the dilute acid solution inlet and the salt solution outlet, and the ammonia stripping tower is equipped with the wastewater outlet at the bottom. The wastewater mother liquor, after being adjusted to pH 11-13 with alkali solution, is preheated by a preheater and then enters the middle of the deammoniation tower, where it comes into countercurrent contact with ammonia-containing water vapor coming from the bottom of the tower, continuously enriching ammonia. The liquid at the bottom of the tower is heated by the working fluid of the hot-side compressor on the cold side of the heat exchange tubes, continuously generating steam. The enriched ammonia-containing water vapor enters the tower and is cooled by the working fluid of the cold-side compressor on the hot side of the heat exchange tubes, condensing the water vapor in the ammonia gas and further enriching the ammonia gas. The enriched ammonia gas is washed with pure water, and high-concentration ammonia water is collected in the upper part of the deammoniation tower. The escaping ammonia gas is sealed with dilute acid aqueous solution at the top of the tower, producing ammonium salt aqueous solution at the top of the deammoniation tower. The wastewater after ammonia removal is collected at the bottom of the deammoniation tower, cooled by a cooler, and then discharged from the unit. After the compressor working fluid vapor on the hot side of the heat exchange tube at the bottom of the tower exchanges heat with the bottom liquid on the cold side, working fluid liquid is generated. After passing through the throttling valve, the working fluid liquid enters the heat exchange tube in the tower on the cold side to cool the ammonia-containing water vapor on the hot side. After the working fluid itself is heated and vaporized, it enters the make-up heat exchanger on the cold side to exchange heat with the heat medium on the hot side, producing superheated working fluid vapor. The superheated working fluid vapor is pressurized into high-pressure steam by the compressor and then goes to the heat exchange tube at the bottom of the tower on the hot side to heat the bottom liquid on the cold side. After passing through the throttling valve, the working fluid liquid of the compressor exchanges heat with the mother liquid on the hot side and cold side of the preheater; After passing through the cold side of the heat exchange tubes in the tower, the compressor working fluid enters the wastewater cooler on the cold side and further exchanges heat with the wastewater at the bottom of the tower on the hot side.

2. The energy-saving process for recovering high-purity ammonia from wastewater as described in claim 1, characterized in that: The working fluid of the compressor is water, R22, R32, or R134, and the corresponding working fluid vapor of the compressor is water vapor, R22 vapor, R32 vapor, or R134 vapor.

3. The energy-saving process for recovering high-purity ammonia from wastewater as described in claim 1, characterized in that: The heat transfer medium on the hot side of the supplementary heat exchanger is steam, hot water, or heat transfer oil.

4. The energy-saving process for recovering high-purity ammonia from wastewater as described in claim 1, characterized in that: The dilute acid aqueous solution is a dilute sulfuric acid aqueous solution, a dilute hydrochloric acid aqueous solution, a carbonic acid aqueous solution, or a phosphoric acid aqueous solution.

5. An energy-saving device for recovering high-purity ammonia from wastewater, characterized in that: An energy-saving process for recovering high-purity ammonia from wastewater according to any one of claims 1-4 includes an ammonia removal tower, a preheater, a wastewater cooler, a supplementary heat exchanger, a compressor, and a throttling valve. The ammonia removal tower comprises, from bottom to top, a heating section, an ammonia removal section, a condensation section, an ammonia washing section, and a purification section. The heating section is equipped with a compressor working fluid inlet and outlet, the ammonia removal section is equipped with a wastewater mother liquor inlet, the condensation section is equipped with a compressor working fluid inlet and outlet, the ammonia washing section is equipped with a pure water inlet and an ammonia water outlet, the purification section is equipped with a dilute acid solution inlet and a salt solution outlet, and a wastewater outlet is located at the bottom of the ammonia removal tower.

6. The energy-saving device for recovering high-purity ammonia from wastewater as described in claim 5, characterized in that: The hot side of the deammoniation tower heating section, the throttling valve, the hot side of the preheater, the cold side of the deammoniation tower condensing section, the cold side of the wastewater cooler, the cold side of the supplementary heat exchanger, and the compressor are connected by working fluid pipelines to form a working fluid circulation loop.

7. The energy-saving device for recovering high-purity ammonia from wastewater as described in claim 5, characterized in that: The ammonia removal section of the ammonia removal tower is equipped with ammonia removal mass transfer internal components such as trays or packing.

8. The energy-saving device for recovering high-purity ammonia from wastewater as described in claim 5, characterized in that: The ammonia washing section of the deammoniation tower is equipped with ammonia washing mass transfer internal components such as trays or packing.

9. The energy-saving device for recovering high-purity ammonia from wastewater as described in claim 5, characterized in that: The purification section of the ammonia removal tower is equipped with a dilute acid aqueous solution liquid seal device.

10. The energy-saving device for recovering high-purity ammonia from wastewater as described in claim 5, characterized in that: The ammonia washing section of the deammoniation tower is equipped with an ammonia water extraction device at the bottom.

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