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

Abstract

The utility model relates to an energy-saving device for recovering high-purity ammonia from wastewater, and belongs to wastewater treatment in the field of environmental protection. Comprising a deamination tower, a preheater, a wastewater cooler, a heat compensation heat exchanger, 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 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. Low-grade waste heat is converted into a high-grade heat source through the compressor, fresh steam is replaced, and the purpose of saving energy is achieved. The problem that tail gas emission needs retreatment in the prior art is solved, zero emission of tail gas is achieved, and meanwhile co-production of ammonia water and ammonium salt is achieved.

Description

Technical Field

[0001] The utility model relates to wastewater treatment in the field of environmental protection, in particular to an energy-saving device for recovering high-purity ammonia from wastewater. Background Art

[0002] Various types of wastewater are generated during life and industrial production, and most of the wastewater contains 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 the characteristics of high concentration and large volume. If ammonia nitrogen wastewater is not treated or treated to meet the standards and discharged directly, it will cause serious environmental hazards, damage ecological security and even crises. The country also has strict standards for the discharge of ammonia nitrogen in wastewater.

[0003] There are many methods for treating ammonia nitrogen wastewater, such as biochemical method, air stripping method, breakpoint chlorination method, chemical precipitation method, etc., but the actual industrial application is subject to certain limitations, and most of them are only suitable for the treatment of medium and low concentration ammonia nitrogen wastewater. The method of steam ammonia evaporation is currently widely used, especially for the treatment of large volume and high concentration ammonia nitrogen wastewater. It is a very effective method. The ammonia evaporation process can be divided into direct steam heating and indirect steam heating process according to the energy method.

[0004] At present, ammonia nitrogen wastewater has complex composition, high salt content, easy scaling and clogging, and unstable ammonia content. Therefore, the traditional ammonia evaporation 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 200-300kg / t of wastewater; 2) The concentration of the obtained ammonia water is unstable, and the ammonia water concentration usually fluctuates greatly, and the product cannot be exported; 3) Ammonia gas easily escapes to produce tail gas, which requires further tail gas treatment.

[0005] In terms of energy saving, although the use of multi-effect ammonia evaporation can save some energy consumption, it requires more equipment and a complex production process. The existing solutions for treating ammonia nitrogen wastewater using heat pump technology are to directly recover the heat of ammonia-containing steam. The temperature difference between the recovered heat and the heat required for heating is relatively large, which places high requirements on the heat pump equipment and requires a large investment in equipment. Utility Model Content

[0006] The utility model aims to provide an energy-saving device for recovering high-purity ammonia from wastewater, and achieves the purpose of energy saving by recovering the heat of water vapor in ammonia-containing steam. The energy-saving device can produce ammonia water with stable output concentration, and can realize the co-production of ammonia water and ammonium salt, and achieve zero ammonia escape, without the need for subsequent tail gas treatment.

[0007] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0008] The invention discloses an energy-saving device for recovering high-purity ammonia from wastewater, comprising a deammonification tower, a preheater, a wastewater cooler, a heat supplementation heat exchanger, a compressor and a throttle valve.

[0009] The deammonification tower comprises a heating section, a deammonification section, a condensation section, an ammonia washing section, and a purification section; the heating section is provided with a compressor working fluid inlet and outlet, the deammonification section is provided with a wastewater mother liquor inlet, the condensation section is provided with a compressor working fluid inlet and outlet, 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 a wastewater outlet is provided at the bottom of the deammonification tower.

[0010] Furthermore, a working fluid pipeline is connected between the hot side of the deamination tower heating section, the throttle valve, the hot side of the preheater, the cold side of the deamination tower condensation section, the cold side of the wastewater cooler, the cold side of the supplementary heat exchanger, and the compressor to form a working fluid circulation loop.

[0011] Furthermore, the deamination section of the deamination tower is provided with deamination mass transfer internal component plates or fillers.

[0012] Furthermore, the ammonia washing section of the deammonification tower is provided with ammonia washing mass transfer internal component tower plates or fillers.

[0013] Furthermore, the purification section of the deammoniation tower is provided with a dilute acid aqueous solution liquid sealing device.

[0014] Furthermore, an ammonia water extraction device is provided at the bottom of the ammonia washing section of the deammonification tower.

[0015] The energy-saving device for recovering high-purity ammonia from wastewater described in the utility model has the following beneficial effects:

[0016] (1) The utility model discloses an energy-saving device for recovering high-purity ammonia from wastewater. A working fluid circulation loop is formed between the hot side of the deamination tower heating section, the hot side of the preheater, the cold side of the deamination tower condensation section, the cold side of the wastewater cooler, and the cold side of the supplementary heat exchanger. The low-grade thermal energy of the water vapor on the hot side of the deamination tower condensation section is converted into high-grade thermal energy to provide a heat source for the deamination tower heating section, replacing the use of a large amount of fresh steam. At the same time, the deamination tower condensation section no longer requires a refrigerant, and the overall energy consumption is significantly reduced.

[0017] (2) The utility model discloses an energy-saving device for recovering high-purity ammonia from wastewater. The working fluid obtains water vapor heat energy in the condensation section in the middle of the deamination tower. The quality of the heat energy is relatively high, and the temperature difference with the heat source required by the heating section at the bottom of the deamination tower is small, so the investment in the compressor is greatly reduced.

[0018] (3) The utility model discloses an energy-saving device for recovering high-purity ammonia from wastewater. The ammonia washing section of the ammonia removal tower uses pure water to wash ammonia. The ammonia recovery rate is high, and ammonia water with a stable concentration can be obtained. The ammonia water concentration can be adjusted between 5-60%.

[0019] (4) The utility model discloses an energy-saving device for recovering high-purity ammonia from wastewater. The purification section of the deammonification tower is sealed with a dilute acid aqueous solution to achieve zero ammonia escape and zero tail gas discharge, and no tail gas treatment is required.

[0020] (5) The utility model discloses an energy-saving device 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.

[0021] (6) The utility model discloses an energy-saving device for recovering high-purity ammonia from wastewater. Only one deammonification tower is needed to achieve ammonia nitrogen content of wastewater after deammonification of ≤10mg / L, which is lower than the national first-level emission standard. At the same time, ammonia water and ammonium salt can be co-produced, and tail gas is zero-emission. The device has a small number of equipment, a simple process, low investment, high efficiency and wide application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to further understand the present invention, the following drawings are provided for illustration:

[0023] Figure 1 It is a schematic diagram of the process flow of Example 1 of the utility model.

[0024] Figure 2 It is a schematic diagram of the process flow of Example 2 of the utility model.

[0025] Figure 3 It is a schematic diagram of the process flow of Example 3 of the present utility model.

[0026] Explanation of the reference numerals: 1 is a mother liquor feed pump; 2 is a preheater; 3 is a throttle valve; 4 is a wastewater discharge pump; 5 is a wastewater cooler; 6 is a supplementary heat exchanger; 7 is a compressor; 8 is a heating heat exchange pipe; 9 is a deammonification mass transfer internal component tower plate or packing; 10 is a condensation heat exchange pipe; 11 is an ammonia water production device; 12 is a wash ammonia mass transfer internal component tower plate or packing; 13 is a liquid seal device; 14 is a deammonification tower; LS is low-pressure steam; SC is condensed water; HWS is hot water in; HWR is hot water return; N2 is nitrogen. DETAILED DESCRIPTION

[0027] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Example 1

[0028] Reference Figure 1 This embodiment provides an energy-saving device for recovering high-purity ammonia from wastewater, and the device includes a mother liquor feed pump 1, a preheater 2, a throttle valve 3, a wastewater discharge pump 4, a wastewater cooler 5, a heat supplement heat exchanger 6, a compressor 7, and a deammonification tower 14.

[0029] The deammonification tower 14 is a single vertical tower body, comprising a heating heat exchange tube 8, a deammonification mass transfer internal component 9, a condensation heat exchange tube 10, an ammonia water extraction device 11, an ammonia washing mass transfer internal component 12, and a purification section liquid seal device 13. The heating section is provided with a compressor working fluid inlet and outlet, the deammonification section is provided with a wastewater mother liquor inlet, the condensation section is provided with a compressor working fluid inlet and outlet, 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 solution inlet and a salt solution outlet.

[0030] The hot side of the heating heat exchange tube 8 of the deamination tower 14, the throttle valve 3, the hot side of the preheater 2, the cold side of the deamination tower condensation heat exchange tube 10, the cold side of the wastewater cooler 5, the cold side of the supplementary heat exchanger 6, and the compressor are connected with a working fluid pipeline to form a working fluid circulation loop.

[0031] By using the energy-saving device provided in this embodiment, high-purity ammonia can be recovered from wastewater through the following steps: after the wastewater mother liquor is adjusted to pH 11-13 by alkali solution, it is pressurized by the mother liquor feed pump 1, enters the cold side of the preheater 2, and is preheated by the compressor working fluid on the hot side, and then enters the wastewater mother liquor inlet of the deammonification tower 14. The wastewater after the removal of ammonia nitrogen is discharged from the tower kettle of the deammonification tower 14, and after being pressurized by the wastewater discharge pump 4, it goes to the hot side of the wastewater cooler 5, and is discharged from the device after being cooled by the compressor working fluid on the hot side. Pure water enters the pure water inlet of the deammonification tower 14, and contacts with high-concentration ammonia gas in countercurrent on the ammonia washing mass transfer internal component 12, and ammonia water with a stable concentration is produced and extracted from the ammonia outlet. The dilute acid aqueous solution enters the dilute acid aqueous solution inlet of the deammonification tower 14, contacts with the escaping tail gas on the purification section liquid seal device 13, ensures zero discharge of tail gas, and extracts ammonium salt at the salt solution outlet.

[0032] The high-pressure working fluid steam at the outlet of the compressor 7 enters the hot side of the heating heat exchange tube 8 of the deammoniation tower 14, heats the liquid in the bottom of the deammoniation tower 14, and the working fluid itself is condensed. After the condensed working fluid liquid is throttled and decompressed by the throttle valve 3, it enters the hot side of the preheater 2 to heat the wastewater mother liquor on the cold side, and the working fluid itself is further cooled. The cooled working fluid enters the cold side of the condensation heat exchange tube 10 of the deammoniation tower 14. The water vapor in the ammonia vapor contained in the condensation tower heats the working fluid itself. The heated working fluid enters the cold side of the wastewater cooler 5 to cool the wastewater on the cold side, and the working fluid itself is further heated and vaporized. The working fluid further enters the cold side of the supplementary heat exchanger 6, and after the working fluid is further heated by the heat medium, the working fluid enters the compressor to be pressurized and converted into high-pressure working fluid steam. This forms a compressor working fluid cycle.

[0033] In this embodiment, the wastewater mother liquor is ternary ammonia nitrogen wastewater from the lithium battery new material industry, and the treatment capacity is 150m 3 / h, the ammonia nitrogen content is 10000~30000mg / L. After being treated by the technology and device described in the utility model, ammonia water with a stable output concentration of 25%wt is produced, and the ammonia nitrogen content in the wastewater after deammoniation is 6.3mg / L, and the wastewater meets the national first-level discharge standard.

[0034] In this embodiment, the compressor working medium cycle makes full use of the waste heat, and only the heat exchanger 6 needs a heat source, which saves a lot of fresh steam and does not require a refrigerant. Compared with the traditional ammonia distillation process, 178.1 kg of steam can be saved for each ton of wastewater mother liquid, and the power consumption of the compressor required for each ton of wastewater mother liquid is 2.3 KWh, and the comprehensive energy consumption is greatly reduced.

[0035] The compressor working fluid enters the condensing heat exchange tube 10 after being further cooled by the preheater 2, which increases the temperature difference between the cold and hot sides of the condensing heat exchange tube 10, reduces the heat transfer area of ​​the condensing heat exchange tube 10, and reduces equipment investment.

[0036] The compressor working fluid is further heated by the wastewater cooler 5 and the supplementary heat exchanger 6 and then enters the compressor 7, thereby increasing the operating stability of the compressor 7 and greatly improving the operating efficiency of the compressor.

[0037] Since the saturated vapor pressure of ammonia is much greater than the saturated vapor pressure of water at the same temperature, ammonia is easy to escape. Therefore, in the traditional ammonia distillation process, when the concentration of ammonia water reaches more than 15%, the escape of ammonia easily causes the pressure fluctuation of the deamination tower, the operation is unstable, and the operation cannot be stably operated, and a large amount of tail gas needs to be processed. In the present embodiment, the escape of ammonia is controlled by dilute acid, and the operation of the deamination tower is very stable, and a high concentration of ammonia water can be stably output, and the tail gas is zero-emission. At the same time, according to the product needs, by adjusting the amount of pure water and dilute acid, the output ratio of ammonia water and ammonium salt can be adjusted to achieve the product structure adjustment of ammonia water and ammonium salt. Example 2

[0038] Reference Figure 2 This embodiment provides an energy-saving device for recovering high-purity ammonia from wastewater, the device comprising a mother liquid feed pump 1, a preheater 2, a throttle valve 3, a wastewater discharge pump 4, a supplementary heat exchanger 6, a compressor 7, and a deammonification tower 14. The preheater 2 also serves as a wastewater cooler 5.

[0039] The internal structure of the deamination tower 14 is the same as that of the first embodiment.

[0040] A working fluid pipeline is connected between the hot side of the heating heat exchange pipe 8 of the deamination tower 14, the throttle valve 3, the cold side of the deamination tower condensation heat exchange pipe 10, the cold side of the supplementary heat exchanger 6, and the compressor to form a working fluid circulation loop.

[0041] By using the energy-saving device provided in this embodiment, high-purity ammonia can be recovered from wastewater through the following steps: after the wastewater mother liquor is adjusted to pH 11-13 by alkali solution, it is pressurized by the mother liquor feed pump 1, enters the cold side of the preheater 2, and is preheated by the bottom wastewater on the hot side before entering the wastewater mother liquor inlet of the deammonification tower 14. The wastewater after the removal of ammonia nitrogen is discharged from the tower kettle of the deammonification tower 14, and is pressurized by the wastewater discharge pump 4 to the hot side of the wastewater cooler 5, and is discharged from the device after the wastewater mother liquor is cooled. Pure water enters the pure water inlet of the deammonification tower 14, and contacts with high-concentration ammonia gas in countercurrent on the ammonia washing mass transfer internal component 12, and ammonia water with a stable concentration is produced and extracted from the ammonia outlet. The dilute acid aqueous solution enters the dilute acid aqueous solution inlet of the deammonification tower 14, contacts with the escaping tail gas on the purification section liquid seal device 13, ensures zero discharge of tail gas, and extracts ammonium salt at the salt solution outlet.

[0042] The high-pressure working fluid vapor at the outlet of the compressor 7 enters the hot side of the heating heat exchange tube 8 of the deamination tower 14, heats the liquid in the bottom of the deamination tower 14, and the working fluid itself is condensed. The condensed working fluid liquid enters the cold side of the condensation heat exchange tube 10 of the deamination tower 14 after throttling and reducing pressure through the throttle valve 3. The condensation tower contains water vapor in the ammonia vapor, and the working fluid itself is heated. The heated working fluid enters the cold side of the supplementary heat exchanger 6. After the working fluid is heated by the heat medium and superheated and gasified, the working fluid vapor enters the compressor to be pressurized and turned into high-pressure working fluid vapor. This forms a compressor working fluid cycle.

[0043] In this embodiment, the wastewater mother liquor is ammonia nitrogen wastewater from a sodium ammonia production device, and the treatment capacity is 125m 3 / h, the ammonia nitrogen content is 8000~25000mg / L. After being treated by the technology and device described in the utility model, ammonia water with a stable output concentration of 18%wt is produced, and the ammonia nitrogen content in the wastewater after deammoniation is 4.7mg / L, and the wastewater meets the national first-level discharge standard.

[0044] In this embodiment, the working medium cycle converts the low-grade heat energy in the condensing heat exchange tube 10 into high-grade heat energy through the compressor, which is used to heat the hot side of the heat exchange tube 8 to heat the bottom liquid of the deamination tower 14, replacing the fresh steam required in the traditional method, achieving the purpose of energy saving, saving a large amount of fresh steam, and no longer requiring refrigerant on the cold side of the condensing heat exchange tube 10. In this embodiment, the only location that requires a heat source is the hot side of the supplementary heat exchanger, and 90°C hot water is used as the heat source.

[0045] Compared with the traditional ammonia distillation process, this embodiment does not require steam and refrigerant, only hot water and electricity, and uses cheap hot water and electricity instead of expensive steam. Treating each ton of wastewater mother liquid can save 237.9 kg of steam, and the power consumption of the compressor required for each ton of wastewater mother liquid is 2.1 KWh, which greatly reduces the comprehensive energy consumption and saves a lot of operating costs.

[0046] Similar to the first embodiment, dilute acid is used to control the escape of ammonia in this embodiment, the operation of the deammoniation tower is stable, and high-concentration ammonia water can be stably produced with zero tail gas emission. At the same time, the co-production of ammonia water and ammonium salt can be achieved. Example 3

[0047] Reference Figure 3 This embodiment provides an energy-saving device for recovering high-purity ammonia from wastewater, and the device 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 a deammonification tower 14.

[0048] The deammonification tower 14 is a single vertical tower body, comprising a heating heat exchange tube 8, a deammonification mass transfer internal component 9, a condensation heat exchange tube 10, an ammonia water extraction device 11, an ammonia washing mass transfer internal component 12, and a purification section liquid seal device 13. A fresh steam inlet is arranged at the bottom of the deammonification tower, a compressor working fluid inlet and outlet are arranged at the heating section, a wastewater mother liquor inlet is arranged at the deammonification section, a compressor working fluid inlet and outlet are arranged at the condensation section, a pure water inlet and an ammonia water outlet are arranged at the ammonia washing section, and a dilute acid aqueous solution inlet and a salt solution outlet are arranged at the purification section.

[0049] A working fluid pipeline is connected between the hot side of the heating heat exchange tube 8 of the deamination tower 14, the throttle valve 3, the hot side of the preheater 2, the cold side of the deamination tower condensation heat exchange tube 10, the cold side of the wastewater cooler 5, and the compressor to form a working fluid circulation loop.

[0050] By using the energy-saving device provided in this embodiment, high-purity ammonia can be recovered from wastewater through the following steps: after the wastewater mother liquor is adjusted to pH 11-13 by alkali solution, it is pressurized by the mother liquor feed pump 1, enters the cold side of the preheater 2, and is preheated by the compressor working medium on the hot side before entering the wastewater mother liquor inlet of the deammonification tower 14. Fresh steam is introduced into the bottom of the deammonification tower 14, and the wastewater after the removal of ammonia nitrogen is discharged from the tower kettle of the deammonification tower 14, and is pressurized by the wastewater discharge pump 4 to the hot side of the wastewater cooler 5, and is discharged from the device after being cooled by the compressor working medium on the hot side. Pure water enters the pure water inlet of the deammonification tower 14, and contacts with high-concentration ammonia gas in countercurrent on the ammonia washing mass transfer internal component 12, and ammonia water with a stable concentration is produced and extracted from the ammonia outlet. Dilute acid aqueous solution enters the dilute acid aqueous solution inlet of the deammonification tower 14, contacts with the escaping tail gas on the purification section liquid seal device 13, ensures zero discharge of tail gas, and extracts ammonium salt at the salt solution outlet.

[0051] The high-pressure working fluid vapor at the outlet of the compressor 7 enters the hot side of the heating heat exchange tube 8 of the deammoniation tower 14, heats the liquid in the bottom of the deammoniation tower 14, and the working fluid itself is condensed. After the condensed working fluid liquid is throttled and depressurized by the throttle valve 3, it enters the hot side of the preheater 2 to heat the wastewater mother liquor on the cold side, and the working fluid itself is further cooled. The cooled working fluid enters the cold side of the condensation heat exchange tube 10 of the deammoniation tower 14, and the water vapor in the ammonia vapor contained in the condensation tower heats the working fluid itself. The heated working fluid enters the cold side of the wastewater cooler 5 to cool the wastewater on the cold side, and the working fluid itself is further heated and vaporized. The working fluid vapor enters the compressor to be pressurized and becomes high-pressure working fluid vapor. This forms a compressor working fluid cycle.

[0052] In this embodiment, the wastewater mother liquor is landfill leachate ammonia nitrogen wastewater, and the treatment capacity is 30m 3 / h, the ammonia nitrogen content is 2000~8000mg / L. After being treated by the technology and device described in the utility model, ammonia water with a stable output concentration of 10%wt is produced, and the ammonia nitrogen content in the wastewater after deammoniation is 4.7mg / L, and the wastewater meets the national first-level emission standard.

[0053] In this embodiment, the working medium cycle converts the low-grade heat energy of the condensing heat exchange tube 10 and the wastewater cooler 5 into high-grade heat energy through the compressor, which is used to heat the heat exchange tube 8 and the preheater 2, saving the amount of fresh steam, and the condensing heat exchange tube 10 and the wastewater cooler 5 no longer need refrigerant. Compared with the traditional ammonia evaporation process, 135.2 kg of steam can be saved for each ton of wastewater mother liquid, and the power consumption of the compressor required for each ton of wastewater mother liquid is 1.9 KWh, and high-concentration ammonia water is stably produced, with zero tail gas emission, and the comprehensive energy consumption is greatly reduced. At the same time, the co-production of ammonia water and ammonium salt can be achieved.

[0054] The above describes the preferred embodiments of the utility model in detail, but the above contents are only the preferred embodiments of the utility model and cannot be considered to limit the scope of implementation of the utility model. All equivalent changes and improvements made according to the scope of application of the utility model should still fall within the scope of coverage of the utility model patent.

Claims

1. An energy-saving device for recovering high-purity ammonia from wastewater, characterized in that: It includes a deamination tower, a preheater, a wastewater cooler, a heat supplement heat exchanger, a compressor, and a throttle valve; The deammonification tower comprises a heating section, a deammonification section, a condensation section, an ammonia washing section, and a purification section; the heating section is provided with a compressor working fluid inlet and outlet, the deammonification section is provided with a wastewater mother liquor inlet, the condensation section is provided with a compressor working fluid inlet and outlet, 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 a wastewater outlet is provided at the bottom of the deammonification tower.

2. The energy-saving device for recovering high-purity ammonia from wastewater according to claim 1, characterized in that: A working fluid pipeline is connected between the hot side of the deamination tower heating section, the throttle valve, the hot side of the preheater, the cold side of the deamination tower condensation section, the cold side of the wastewater cooler, the cold side of the supplementary heat exchanger, and the compressor to form a working fluid circulation loop.

3. The energy-saving device for recovering high-purity ammonia from wastewater according to claim 1, characterized in that: The deamination section of the deamination tower is provided with deamination mass transfer internal component plates or fillers.

4. The energy-saving device for recovering high-purity ammonia from wastewater according to claim 1, characterized in that: The ammonia washing section of the deammonification tower is provided with ammonia washing mass transfer internal component plates or fillers.

5. The energy-saving device for recovering high-purity ammonia from wastewater according to claim 1, characterized in that: The purification section of the deammoniation tower is equipped with a dilute acid aqueous solution liquid seal device.

6. The energy-saving device for recovering high-purity ammonia from wastewater according to claim 1, characterized in that: An ammonia water extraction device is provided at the bottom of the ammonia washing section of the deammonification tower.

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