A high-concentration ammonia-nitrogen wastewater treatment device and its treatment method

Abstract

The present invention discloses a high-concentration ammonia-nitrogen wastewater treatment device and a treatment method thereof, including a pH adjustment tank. A liquid inlet pump is connected in communication between the liquid outlet of the pH adjustment tank and the first liquid inlet of the first heat exchanger. The first liquid outlet of the first heat exchanger is connected in communication with the first liquid inlet of the second heat exchanger. The first liquid outlet of the third heat exchanger is connected in communication with the liquid inlet of the primary stripping tower. A stripping pump is connected in communication between the liquid outlet of the primary stripping tower and the liquid inlet of the secondary stripping tower. A discharge pump is connected in communication between the liquid outlet of the secondary stripping tower and the second liquid inlet of the first heat exchanger. Before the wastewater is treated, the present invention can heat it three times through the heat exchanger, so as to ensure that the temperature of the wastewater can reach 40-50 °C, improve the stripping effect, and when heat exchange is carried out, the first heat exchanger and the second heat exchanger recover and utilize the temperatures of the discharged water and the recovered liquid, reducing heat loss.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia nitrogen wastewater treatment, and specifically provides a high-concentration ammonia nitrogen wastewater treatment device and a treatment method thereof. Background Art

[0002] With the improvement of people's living standards, the strengthening of environmental requirements, the strengthening of environmental pollution control and the development of environmental protection technologies, the representative index of organic matter in water bodies - COD has basically been effectively controlled. However, the up-to-standard discharge of high-ammonia-nitrogen wastewater has not been effectively controlled, and the discharge of untreated nitrogen-containing wastewater has caused great harm to the environment, such as easily leading to lake eutrophication, marine red tides, etc.

[0003] Many methods can effectively treat ammonia nitrogen. For example, physical and chemical methods include stripping, air stripping, breakpoint chlorination, ion exchange, coagulation precipitation, reverse osmosis, electrodialysis, and various advanced oxidation technologies; biological methods include nitrification and cultivation of aquatic plants such as water algae.

[0004] Breakpoint chlorination method has problems of safety and secondary pollution, and the treatment cost is relatively high; the precipitant cost of chemical precipitation method is relatively high, and it is not easy to control the optimal precipitation conditions; air stripping method and steam stripping method are prone to cause secondary pollution; the resin regeneration problem of ion exchange method has not been solved. For traditional biological denitrification method, its main problem is that the growth of nitrifying bacteria is strongly affected by temperature, alkalinity, dissolved oxygen, and COD. At the same time, high-concentration NH3-N wastewater will inhibit the growth of nitrifying bacteria, resulting in low efficiency of the nitrification process and weak shock resistance of the biological system. Based on this, the present invention designs a high-concentration ammonia nitrogen wastewater treatment device and a treatment method thereof to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-concentration ammonia nitrogen wastewater treatment device and a treatment method thereof to solve the above technical problems.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A high-concentration ammonia nitrogen wastewater treatment device includes a pH adjustment tank, a feed pump, a first heat exchanger, a second heat exchanger, a third heat exchanger, a primary stripping tower, a secondary stripping tower, a stripping pump, a discharge pump, a centrifugal fan, an absorption tower, and an absorption recovery pump;

[0007] The liquid outlet of the pH adjustment tank is connected to the first liquid inlet of the first heat exchanger through a feed pump. The first liquid outlet of the first heat exchanger is connected to the first liquid inlet of the second heat exchanger. The first liquid outlet of the second heat exchanger is connected to the first liquid inlet of the third heat exchanger. The first liquid outlet of the third heat exchanger is connected to the liquid inlet of the primary stripping tower. The liquid outlet of the primary stripping tower is connected to the liquid inlet of the secondary stripping tower through a stripping pump. The liquid outlet of the secondary stripping tower is connected to the second liquid inlet of the first heat exchanger through a discharge pump;

[0008] The exhaust air outlet of the secondary stripping tower is connected to the air inlet of the primary stripping tower. The exhaust air outlet of the primary stripping tower is connected to the air inlet of the absorption tower. The exhaust air outlet of the absorption tower is connected to the air inlet of the secondary stripping tower through a centrifugal fan;

[0009] The liquid outlet of the absorption tower is connected to the second liquid inlet of the second heat exchanger through an absorption recovery pump.

[0010] Preferably, the centrifugal fan at the air inlet of the secondary stripping tower is also connected to a make-up air duct, and an electric control valve is provided on the make-up air duct.

[0011] Preferably, the primary stripping tower includes a first tower body. The bottom of the first tower body is connected to a first circulation water tank. The first circulation water tank is provided with a liquid outlet. Inside the first tower body, a first packing layer, a first spray pipe, and a first demisting layer are arranged from bottom to top in sequence. The first spray pipe is connected to the liquid inlet of the first tower body. The air inlet of the first tower body is located below the first packing layer, and the air outlet of the first tower body is located above the first demisting layer.

[0012] Preferably, the structure of the secondary stripping tower is the same as that of the primary stripping tower.

[0013] Preferably, a steam pipe is connected to the second liquid inlet of the third heat exchanger.

[0014] Preferably, the absorption tower includes a second tower body. The bottom of the second tower body is connected to a second circulation water tank. Inside the cavity of the second tower body, a second packing layer, a second spray pipe, and a second demisting layer are arranged from bottom to top in sequence. The first liquid outlet of the second circulation water tank is connected to an absorption pump, and the absorption pump is connected to the second spray pipe. The second liquid outlet of the second circulation water tank is connected to the absorption recovery pump.

[0015] Preferably, sulfuric acid or hydrochloric acid is injected into the second circulation water tank.

[0016] A treatment method for a high-concentration ammonia-nitrogen wastewater treatment device, the treatment method comprising the following steps:

[0017] S1. Introduce the wastewater into the pH adjustment tank and add alkali to adjust the pH value of the wastewater to 10 - 11;

[0018] S2. Sequentially introduce the adjusted wastewater into the first heat exchanger, the second heat exchanger, and the third heat exchanger for heat exchange, thereby raising the temperature of the wastewater to 40°C - 50°C;

[0019] S3. Sequentially introduce the heated wastewater into the primary stripping tower and the secondary stripping tower for stripping treatment to reduce the ammonia nitrogen concentration in the wastewater;

[0020] S4. Introduce the stripped wastewater into the first heat exchanger and perform subsequent treatment after heat exchange with the wastewater whose pH has been adjusted.

[0021] Preferably, the treatment method further includes: introducing the stripping gas in the primary stripping tower into the absorption tower, thereby absorbing the ammonia gas in the stripping gas and forming an absorption liquid.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1) By setting the first heat exchanger, the second heat exchanger, and the third heat exchanger, the wastewater can be heated three times by the heat exchanger before treatment, thereby ensuring that the temperature of the wastewater can reach 40 - 50°C, improving the stripping effect. Moreover, during heat exchange, the first heat exchanger and the second heat exchanger recycle the temperatures of the discharged water and the recovered liquid, reducing heat loss;

[0024] 2) The stripping gas in the present invention is used in a closed cycle in the primary stripping tower, the secondary stripping tower, and the absorption tower. On the one hand, it reduces heat loss. On the other hand, due to the closed effect, there is no gas leakage, and it does not cause adverse effects on the surrounding environment;

[0025] 3) The present invention uses sulfuric acid or hydrochloric acid as the absorption liquid, not only recovering ammonia gas, but also producing ammonium sulfate or ammonium chloride as products, which has recycling value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for describing the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 is a structural schematic diagram of the present invention;

[0028] Figure 2 is a structural schematic diagram of the primary stripping tower in the present invention;

[0029] Figure 3 This is a schematic structural diagram of the absorption tower in the present invention.

[0030] In the attached drawings, the list of components represented by each label is as follows:

[0031] 1. pH adjustment tank; 2. Feed pump; 3. First heat exchanger; 4. Second heat exchanger; 5. Third heat exchanger; 6. Primary stripping tower; 61. First tower body; 62. First circulating water tank; 63. First packing layer; 64. First spray pipe; 65. First demisting layer; 7. Secondary stripping tower; 8. Stripping pump; 9. Discharge pump; 10. Centrifugal fan; 11. Absorption tower; 111. Second tower body; 112. Second circulating water tank; 113. Second packing layer; 114. Second spray pipe; 115. Second demisting layer; 116. Absorption pump; 12. Absorption recovery pump; 13. Makeup air duct. Specific embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] Please refer to Figures 1-3 , the present invention provides a technical solution: a high-concentration ammonia-nitrogen wastewater treatment device, including a pH adjustment tank 1, a feed pump 2, a first heat exchanger 3, a second heat exchanger 4, a third heat exchanger 5, a primary stripping tower 6, a secondary stripping tower 7, a stripping pump 8, a discharge pump 9, a centrifugal fan 10, an absorption tower 11, and an absorption recovery pump 12;

[0034] The liquid outlet of the pH adjustment tank 1 is connected to the first liquid inlet of the first heat exchanger 3 through the feed pump 2, the first liquid outlet of the first heat exchanger 3 is connected to the first liquid inlet of the second heat exchanger 4, the first liquid outlet of the second heat exchanger 4 is connected to the first liquid inlet of the third heat exchanger 5, the first liquid outlet of the third heat exchanger 5 is connected to the liquid inlet of the primary stripping tower 6, the liquid outlet of the primary stripping tower 6 is connected to the liquid inlet of the secondary stripping tower 7 through the stripping pump 8, and the liquid outlet of the secondary stripping tower 7 is connected to the second liquid inlet of the first heat exchanger 3 through the discharge pump 9;

[0035] The exhaust port of the secondary stripping tower 7 is connected to the air inlet of the primary stripping tower 6, the exhaust port of the primary stripping tower 6 is connected to the air inlet of the absorption tower 11, and the exhaust port of the absorption tower 11 is connected to the air inlet of the secondary stripping tower 7 through the centrifugal fan 10;

[0036] The liquid outlet of the absorption tower 11 is connected to the second liquid inlet of the second heat exchanger 4 through an absorption recovery pump 12.

[0037] Specifically, a centrifugal fan 10 at the air inlet of the secondary stripping tower 7 is also connected to a makeup air duct 13. The makeup air duct 13 is provided with an electric control valve. Since there may be air leakage in the stripping tower, absorption tower and air duct, resulting in a decrease in the air volume of the stripping gas, a makeup air inlet needs to be provided at the air inlet of the centrifugal fan to automatically supplement air regularly to ensure the air-water ratio.

[0038] Specifically, the primary stripping tower 6 includes a first tower body 61. The bottom of the first tower body 61 is connected to a first circulation water tank 62. The first circulation water tank 62 is provided with a liquid outlet. Inside the first tower body 61, a first packing layer 63, a first spray pipe 64 and a first demisting layer 65 are arranged in sequence from bottom to top. The first spray pipe 64 is connected to the liquid inlet of the first tower body 61. The air inlet of the first tower body 61 is located below the first packing layer 63, and the air outlet of the first tower body 61 is located above the first demisting layer 65. The wastewater is sprayed from top to bottom through the spray pipe arranged at the top of the primary stripping tower. The wastewater makes water-air contact with the gas entering from the bottom air inlet in the packing layer, and most of the ammonia nitrogen in the water is stripped into the gas in the form of ammonia, thus greatly reducing the ammonia nitrogen concentration in the wastewater.

[0039] Specifically, the structure of the secondary stripping tower 7 is the same as that of the primary stripping tower 6.

[0040] Specifically, the second liquid inlet of the third heat exchanger 5 is connected to a steam pipe, and heat exchange is carried out between steam and wastewater.

[0041] Specifically, the absorption tower 11 includes a second tower body 111. The bottom of the second tower body 111 is connected to a second circulation water tank 112. Inside the cavity of the second tower body 111, a second packing layer 113, a second spray pipe 114 and a second demisting layer 115 are arranged in sequence from bottom to top. The first liquid outlet of the second circulation water tank 112 is connected to an absorption pump 116. The absorption pump 116 is connected to the second spray pipe 114. The second liquid outlet of the second circulation water tank 112 is connected to the absorption recovery pump 12. The absorption pump pumps the absorption liquid out of the circulation water tank and into the spray pipe at the top of the absorption tower. The absorption liquid is sprayed from top to bottom into the packing. The stripping gas (containing a large amount of ammonia) entering from the bottom air inlet of the stripping tower contacts the absorption liquid countercurrently in the packing layer from bottom to top. The absorption liquid reacts with ammonia to produce ammonium sulfate or ammonium chloride, thereby absorbing the ammonia in the gas.

[0042] Specifically, sulfuric acid or hydrochloric acid is injected into the second circulation water tank 112.

[0043] A treatment method for a high-concentration ammonia-nitrogen wastewater treatment device, the treatment method includes the following steps:

[0044] S1. Introduce the wastewater into the pH adjustment tank 1 and add alkali to adjust the pH value of the wastewater to 10 - 11;

[0045] S2. Sequentially introduce the adjusted wastewater into the first heat exchanger 3, the second heat exchanger 4, and the third heat exchanger 5 for heat exchange, thereby raising the temperature of the wastewater to 40°C - 50°C;

[0046] S3. Sequentially introduce the heated wastewater into the primary stripping tower 6 and the secondary stripping tower 7 for stripping treatment to reduce the ammonia nitrogen concentration in the wastewater;

[0047] S4. Introduce the stripped wastewater into the first heat exchanger 3 and perform subsequent treatment after heat exchange with the wastewater whose pH has been adjusted.

[0048] Specifically, the treatment method further includes: introducing the stripping gas in the primary stripping tower 6 into the absorption tower 11, thereby absorbing the ammonia gas in the stripping gas and forming an absorption liquid.

[0049] A specific application embodiment of the present invention is as follows. Please refer to Figures 1 to 3 as shown:

[0050] During wastewater treatment: The wastewater first enters the pH adjustment tank 1, and alkali is added to adjust the pH value of the wastewater to 10 - 11. Then, the wastewater is sequentially pumped into the first heat exchanger 3, the second heat exchanger 4, and the third heat exchanger 5 by the feed pump 2, so that the wastewater exchanges heat with the discharged water from the secondary stripping tower 8, the absorption liquid in the absorption tower 11, and steam respectively, thereby raising its temperature to 40 - 50°C;

[0051] Then, the wastewater is sprayed from top to bottom through the first spray pipe 64 provided at the top of the primary stripping tower 6. The wastewater makes water - gas contact with the gas entering from the bottom air inlet in the first packing layer 63. Most of the ammonia nitrogen in the water is stripped into the gas in the form of ammonia gas, thereby greatly reducing the ammonia nitrogen concentration in the wastewater. At the same time, the pH value of the wastewater also decreases. Then, the pH value of the wastewater is readjusted to 10 - 11 by adding alkali in the first circulation pool 62 at the bottom of the primary stripping tower 6, and then it is pumped into the secondary stripping tower 7 for treatment by the stripping pump 8. The secondary stripping tower 7 has the same structure as the primary stripping tower 6.

[0052] During stripping, the centrifugal fan 10 pumps the stripping gas into the bottom air inlet of the secondary stripping tower 7, and the gas contacts the wastewater sprayed from top to bottom in the packing layer from bottom to top, further stripping to reduce the ammonia nitrogen concentration in the wastewater. Finally, the wastewater is pumped out by the discharge pump 9, enters the first heat exchanger 3 to exchange heat with the wastewater, and then enters the subsequent treatment process. And the stripping gas in the secondary stripping tower 7 removes the liquid droplets in the stripping gas through the demisting layer and then is discharged into the primary stripping tower 6;

[0053] After the stripping gas in the first-stage stripping tower 6 contacts the wastewater in the packing layer, most of the ammonia nitrogen in the water is stripped into the gas in the form of ammonia gas. After the liquid droplets entrained in the gas are removed by the demisting layer provided at the top of the stripping tower, it enters the air inlet at the bottom of the absorption tower 11. The absorption tower 11 is composed of a second circulation pool 112 and a second tower body 111. The absorption liquid - sulfuric acid or hydrochloric acid is stored in the circulation pool of the absorption tower 11. The absorption pump 116 pumps the absorption liquid out of the second circulation pool 112 and into the second spray pipe 114 at the top of the absorption tower 11. The absorption liquid is sprayed downward into the second packing layer 113. The stripping gas (containing a large amount of ammonia gas) entering from the air inlet at the bottom of the stripping tower contacts the absorption liquid countercurrently from bottom to top in the second packing layer 113. The absorption liquid reacts with ammonia gas to produce ammonium sulfate or ammonium chloride, thereby absorbing the ammonia gas in the gas. Then the absorption liquid enters the second circulation pool 112 and is pumped out by the absorption pump 116 again and enters the second spray pipe 114 at the top of the absorption tower 11 and sprays downward, continuously circulating to absorb the ammonia gas in the stripping gas, and at the same time continuously supplementing sulfuric acid or hydrochloric acid to ensure the absorption efficiency.

[0054] After the absorption liquid is absorbed to a certain extent, it is pumped out by the absorption recovery pump 12 and enters the second heat exchanger 4. The wastewater at the first outlet of the first heat exchanger 3 and the absorption liquid perform a second heat exchange in the second heat exchanger 4. After further increasing the temperature of the wastewater, the absorption liquid is recycled.

[0055] After the ammonia gas in the stripping gas in the absorption tower 11 is absorbed, it enters the demister at the top of the absorption tower 11 to remove the liquid droplets entrained in the gas and then re-enters the inlet of the centrifugal fan 10. After the boosting effect of the centrifugal fan 10, it enters the air inlet at the bottom of the second-stage stripping tower again to strip the wastewater.

[0056] The stripping gas continuously circulates in the second-stage stripping tower 7, the first-stage stripping tower 6 and the absorption tower 11. Since there may be air leakage in the stripping tower, the absorption tower and the air duct, resulting in a decrease in the air volume of the stripping gas, a makeup air port needs to be provided at the air inlet of the centrifugal fan 10 to automatically supplement air regularly to ensure the air-water ratio. At the same time, to reduce the heat loss of the treatment system, external insulation layers are provided for all tower bodies, air ducts and water pipes.

[0057] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inner", "front", "center", "both ends", etc. is the orientation or positional relationship based on the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0058] In the present invention, unless otherwise clearly defined and limited, terms such as "installation", "setting", "connection", "fixation", "swivel connection" and the like shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components. Unless otherwise clearly defined, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that these embodiments can be modified without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-concentration ammonia nitrogen wastewater treatment device, characterized in that: It includes a pH adjustment tank (1), a feed pump (2), a first heat exchanger (3), a second heat exchanger (4), a third heat exchanger (5), a primary stripping tower (6), a secondary stripping tower (7), a stripping pump (8), a discharge pump (9), a centrifugal fan (10), an absorption tower (11), and an absorption recovery pump (12); The liquid outlet of the pH adjustment tank (1) is connected to the first liquid inlet of the first heat exchanger (3) through the feed pump (2). The first liquid outlet of the first heat exchanger (3) is connected to the first liquid inlet of the second heat exchanger (4). The first liquid outlet of the second heat exchanger (4) is connected to the first liquid inlet of the third heat exchanger (5). The first liquid outlet of the third heat exchanger (5) is connected to the liquid inlet of the primary stripping tower (6). The liquid outlet of the primary stripping tower (6) is connected to the liquid inlet of the secondary stripping tower (7) through the stripping pump (8). The liquid outlet of the secondary stripping tower (7) is connected to the second liquid inlet of the first heat exchanger (3) through the discharge pump (9); The exhaust port of the secondary stripping tower (7) is connected to the air inlet of the primary stripping tower (6). The exhaust port of the primary stripping tower (6) is connected to the air inlet of the absorption tower (11). The exhaust port of the absorption tower (11) is connected to the air inlet of the secondary stripping tower (7) through the centrifugal fan (10); The liquid outlet of the absorption tower (11) is connected to the second liquid inlet of the second heat exchanger (4) through the absorption recovery pump (12); The centrifugal fan (10) at the air inlet of the secondary stripping tower (7) is also connected to a make-up air pipeline (13), and the make-up air pipeline (13) is provided with an electric control valve; The second liquid inlet of the third heat exchanger (5) is connected to a steam pipe.

2. The high-concentration ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that: The primary stripping tower (6) includes a first tower body (61). The bottom of the first tower body (61) is connected to a first circulation water tank (62). The first circulation water tank (62) is provided with a liquid outlet. Inside the first tower body (61), a first packing layer (63), a first spray pipe (64), and a first demisting layer (65) are sequentially arranged from bottom to top. The first spray pipe (64) is connected to the liquid inlet of the first tower body (61). The air inlet of the first tower body (61) is located below the first packing layer (63). The air outlet of the first tower body (61) is located above the first demisting layer (65).

3. The high-concentration ammonia nitrogen wastewater treatment device according to claim 2, wherein: The structure of the secondary stripping tower (7) is the same as that of the primary stripping tower (6).

4. A high-concentration ammonia-nitrogen wastewater treatment device according to claim 1, characterized in that: The absorption tower (11) includes a second tower body (111). The bottom of the second tower body (111) is connected to a second circulation water tank (112). Inside the cavity of the second tower body (111), a second packing layer (113), a second spray pipe (114), and a second demisting layer (115) are sequentially arranged from bottom to top. The first liquid outlet of the second circulation water tank (112) is connected to an absorption pump (116), and the absorption pump (116) is connected to the second spray pipe (114). The second liquid outlet of the second circulation water tank (112) is connected to the absorption recovery pump (12).

5. The high-concentration ammonia-nitrogen wastewater treatment device according to claim 4, wherein: Sulfuric acid or hydrochloric acid is injected into the second circulation pool (112).

6. A treatment method for a high-concentration ammonia-nitrogen wastewater treatment device according to any one of claims 1-5, characterized in that: The treatment method includes the following steps: S1. Introduce the wastewater into the pH adjustment tank (1), and add alkali to adjust the pH value of the wastewater to 10 - 11; S2. Sequentially introduce the adjusted wastewater into the first heat exchanger (3), the second heat exchanger (4) and the third heat exchanger (5) for heat exchange, so as to raise the temperature of the wastewater to 40°C - 50°C; S3. Sequentially introduce the heated wastewater into the primary stripping tower (6) and the secondary stripping tower (7) for stripping treatment to reduce the ammonia nitrogen concentration in the wastewater; S4. Introduce the stripped wastewater into the first heat exchanger (3), and perform subsequent treatment after heat exchange with the wastewater after pH adjustment.

7. The treatment method of a high-concentration ammonia-nitrogen wastewater treatment device according to claim 6, characterized in that: The treatment method further includes: introducing the stripping gas in the primary stripping tower (6) into the absorption tower (11), so as to absorb the ammonia gas in the stripping gas and form an absorption liquid.

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