Separation device and method for precipitating ammonia nitrogen in sewage by struvite method

Abstract

The invention relates to the technical field of sewage treatment equipment, in particular to a separation device and method for precipitating ammonia nitrogen in sewage through a struvite method.The separation device comprises a mixing pool, a sewage inlet, a magnesium source inlet and a phosphorus source inlet are formed in the mixing pool, and a sewage discharge pipeline is arranged at the bottom of the mixing pool; the other end of the sewage discharge pipeline is provided with a hydrocyclone, the sewage discharge pipeline is sequentially provided with a centrifugal pump and a Venturi tube, the bottom of the hydrocyclone is provided with a sediment discharge pipeline, a water outlet in the top of the hydrocyclone is provided with a horizontal separation column, and the tail end of the horizontal separation column is provided with a drainage pipeline. And the bottom of the tail end of the horizontal separation column is connected with the Venturi tube through a pipeline. According to the present invention, with the dual effects of the hydrocyclone and the horizontal separation column, the efficient separation of the sewage and the struvite precipitation is achieved, the precipitation efficiency is improved, and the struvite purity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment equipment, and in particular to a device and method for separating ammonia nitrogen in sewage by using a struvite method to precipitate it. Background Art

[0002] With the rapid advancement of industrialization, the amount of sewage discharge has increased dramatically. Organic amine products are key raw materials in the chemical industry. The sewage generated during their production process is rich in amino components. These substances will release a large amount of ammonia nitrogen during biodegradation, which will not only pollute surface water and cause eutrophication of water bodies, but also damage groundwater ecosystems and even endanger human health. Therefore, effective means are urgently needed to deeply purify them.

[0003] There are many treatment technologies for high-concentration ammonia nitrogen wastewater, such as air stripping, biological methods, ion exchange and precipitation methods. However, the air stripping method is not only energy-intensive and has high operating costs, but also prone to scale formation, and its efficiency is greatly reduced in cold weather. The biological method is not satisfactory for the treatment of high-concentration ammonia nitrogen wastewater due to limitations such as large footprint, slow reaction rate and long sludge acclimation cycle.

[0004] In the 1990s, struvite precipitation was used as an emerging technology for treating ammonia nitrogen wastewater, and was particularly good at treating high-concentration wastewater. This method effectively removes ammonia nitrogen by adding an appropriate amount of magnesium source and phosphorus source to the wastewater, which reacts chemically with the ammonia nitrogen in the wastewater to generate magnesium ammonium phosphate precipitate. The generated magnesium ammonium phosphate precipitate is also a high-quality slow-release fertilizer, which realizes the resource recycling of ammonia nitrogen. In addition, the struvite precipitation reaction is not restricted by temperature and toxins in the water. It is simple in design and easy to operate. It can not only treat low-concentration ammonia nitrogen wastewater, but also shows excellent removal ability for high-concentration wastewater.

[0005] However, the existing equipment systems for treating sewage using the struvite precipitation method are usually large in size, occupy a large amount of site space, and have a relatively complicated operation process. In order to increase the precipitation and crystallization rate of struvite, a large amount of precipitant is required, which increases the cost of sewage treatment, and the equipment needs to be pressurized, which consumes a lot of power. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a device and method for separating ammonia nitrogen in sewage by using a struvite method.

[0007] To achieve the above-mentioned purpose, the technical scheme of the present invention is as follows: a device for separating ammonia nitrogen in sewage by a struvite method, comprising a mixing tank, wherein a sewage inlet, a magnesium source inlet and a phosphorus source inlet are respectively arranged on the mixing tank, a sewage discharge pipe is arranged at the bottom of the mixing tank, a hydrocyclone is arranged at the other end of the sewage discharge pipe, a centrifugal pump and a venturi tube are arranged on the sewage discharge pipe in sequence, a sedimentation discharge pipe is arranged at the bottom of the hydrocyclone, a horizontal separation column is arranged at the water outlet at the top of the hydrocyclone, a drainage pipe is arranged at the end of the horizontal separation column, and the bottom of the end of the horizontal separation column is connected to the venturi tube through a pipe.

[0008] Furthermore, a stirring paddle is arranged in the mixing tank, and a motor for controlling the rotation of the stirring paddle is arranged on the top of the stirring paddle.

[0009] Furthermore, the venturi tube is close to the inlet end of the hydrocyclone.

[0010] Furthermore, the inner diameter of the horizontal separation column is larger than the inner diameter of the sewage discharge pipe.

[0011] Furthermore, the horizontal separation column is a horizontally arranged cylindrical structure.

[0012] Furthermore, a first valve is provided on the sewage discharge pipe, a second valve is provided on the sediment discharge pipe, and a third valve is provided on the connecting pipe between the horizontal separation column and the venturi tube.

[0013] Furthermore, the first valve, the second valve and the third valve are all flow control valves.

[0014] Furthermore, a pH monitor is provided in the mixing tank.

[0015] Furthermore, a pressure gauge and a flow meter are provided between the centrifugal pump and the venturi tube.

[0016] A method for separating ammonia nitrogen from wastewater precipitated by struvite, based on the above-mentioned device for separating ammonia nitrogen from wastewater precipitated by struvite, comprises the following steps:

[0017] Step 1: adding a magnesium source and a phosphorus source into the sewage containing ammonia nitrogen and stirring to mix;

[0018] Step 2: The mixed sewage in step 1 is passed through a venturi tube into a hydrocyclone to separate the precipitate from the solution;

[0019] Step 3: The sewage discharged from the hydrocyclone partially flows back to the venturi tube through the horizontal separation column and enters the hydrocyclone again for sedimentation cycle.

[0020] The beneficial effects achieved by the present invention are:

[0021] 1. The present invention realizes efficient separation of sewage and struvite precipitates through the dual effects of a hydrocyclone and a horizontal separation column. The hydrocyclone uses the centrifugal force generated by rotation to separate larger struvite precipitates from sewage, while the horizontal separation column further separates fine struvite particles, thereby improving the precipitation efficiency and the purity of the struvite.

[0022] 2. The present invention utilizes the principle of the Venturi tube to return part of the water in the horizontal separation column to the front end of the hydrocyclone. The small particles precipitated in the reflux water can be used as crystal seeds, which helps to form larger precipitation particles in the subsequent process, thereby reducing the use of precipitants and reducing the cost of sewage treatment.

[0023] 3. The whole device of the present invention has a simple structure, the components are tightly connected, and the footprint is small, which is convenient for daily maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0025] Explanation of the markings in the figure: 1. Mixing tank; 2. Sewage discharge pipe; 3. Centrifugal pump; 4. Venturi tube; 5. Hydrocyclone; 6. Sedimentation discharge pipe; 7. Horizontal separation column; 8. Drainage pipe; 11. Sewage inlet; 12. Magnesium source inlet; 13. Phosphorus source inlet; 14. Agitator; 15. Motor; 21. First valve; 61. Second valve; 71. Third valve. DETAILED DESCRIPTION

[0026] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a device and method for separating ammonia nitrogen from sewage by struvite precipitation according to the present invention in conjunction with the accompanying drawings.

[0027] like Figure 1 As shown, a device for separating ammonia nitrogen in sewage by struvite precipitation includes a mixing tank 1, a sewage inlet 11 for sewage, a magnesium source inlet 12 for magnesium source, and a phosphorus source inlet 13 for phosphorus source are respectively arranged on the top of the mixing tank 1, a stirring paddle 14 is arranged in the mixing tank 1, and a motor 15 for controlling the rotation of the stirring paddle 14 is arranged above the stirring paddle 14. A pH monitor is also arranged in the mixing tank 1 to facilitate the adjustment of the pH value of the sewage in the mixing tank 1.

[0028] A sewage discharge pipe 2 is provided at the bottom of the mixing tank 1, and the other end of the sewage discharge pipe 2 is connected to the water inlet of the hydrocyclone 5. A centrifugal pump 3 and a venturi tube 4 are provided on the sewage discharge pipe 2. A first valve 21 is provided between the mixing tank 1 and the centrifugal pump 3. The first valve 21 is a flow control valve. The centrifugal pump 3 is arranged close to the mixing tank 1 to facilitate rapid discharge of the sewage after the reaction in the mixing tank 1 into the hydrocyclone 5. The venturi tube 4 is close to the water inlet end of the hydrocyclone 5. A pressure gauge and a flow meter are also provided on the sewage discharge pipe 2. The pressure gauge and the flow meter are arranged between the centrifugal pump 3 and the venturi tube 5.

[0029] A sedimentation discharge pipe 6 is provided at the bottom of the hydrocyclone 5, and the sedimentation discharge pipe 6 is convenient for discharging the struvite sediment in the hydrocyclone 5. A second valve 61 is provided on the sedimentation discharge pipe 6, and the second valve 61 is a flow control valve. A horizontal separation column 7 is provided at the water outlet at the top of the hydrocyclone 5. The horizontal separation column 7 is a horizontally arranged cylindrical structure, and the inner diameter of the horizontal separation column 7 is larger than the inner diameter of the sewage discharge pipe 2. The other end of the horizontal separation column 7 is connected to a drainage pipe 8. The bottom of one end of the horizontal separation column 7 connected to the drainage pipe 8 is connected to the venturi tube 4 through a connecting pipe. A third valve 71 is provided at the connection between the horizontal separation column 7 and the venturi tube 4, and the third valve 71 is a flow control valve.

[0030] The diameter of the sewage discharge pipe 2 is 35 mm, the diameters of the connecting pipes between the drainage pipe 8 and the horizontal separation column 7 and the venturi tube 4 are all 50 mm, and the inner diameter of the horizontal separation column 7 is larger than the inner diameter of the drainage pipe 8 .

[0031] A method for separating ammonia nitrogen from sewage by struvite precipitation comprises the following steps:

[0032] Step 1: adding a magnesium source and a phosphorus source into the sewage containing ammonia nitrogen and stirring to mix;

[0033] Step 2: The mixed sewage in step 1 is passed through the venturi tube 4 into the hydrocyclone 5 to separate the precipitate from the solution;

[0034] Step 3: The sewage discharged from the hydrocyclone 5 partially flows back to the venturi tube 4 through the horizontal separation column 7 and enters the hydrocyclone 5 again for sedimentation cycle.

[0035] The working process of the present invention is:

[0036] 1 t of sewage to be treated is added into the mixing tank 1 through the sewage inlet 11, and the stirring paddle 14 is started by the motor 15 to stir the sewage. According to the concentration of ammonia nitrogen in the sewage to be treated in the mixing tank 1, a corresponding amount of magnesium salt is added into the mixing tank 1 through the magnesium source inlet 12, and a corresponding amount of phosphate is added into the mixing tank 1 through the phosphorus source inlet 13. The centrifugal pump 3 is started, and the flow rate of the centrifugal pump 3 is adjusted to 10 t / h. At the same time, the water flow rate of the sewage inlet is controlled to be 10 t / h. The sewage is accelerated by the centrifugal pump 3, passes through the venturi tube 4, and enters the hydrocyclone 5 at a higher speed along the tangent direction of the feed pipe of the hydrocyclone 5. 5, the larger struvite precipitate is discharged through the precipitation discharge pipe 6 at the bottom of the hydrocyclone 5, and the treated sewage and the fine struvite particles in the hydrocyclone 5 enter the horizontal separation column 7. The treated sewage continues to rotate in the horizontal separation column 7 due to inertia, and the sewage and the fine struvite particles are further separated. The fine struvite particles return to the hydrocyclone 5 through the connecting pipe between the horizontal separation column 7 and the venturi tube 4 to continue to participate in precipitation. The fine struvite precipitate can be used as a crystal seed for precipitation, thereby improving the precipitation efficiency of the struvite in the hydrocyclone 5, reducing the amount of precipitant used, and reducing the sewage treatment cost.

[0037] The working principle of the present invention is:

[0038] Sewage containing ammonia nitrogen is added to the mixing tank 1, and corresponding dosages of magnesium and phosphorus are added. The mixed liquid is lifted by the centrifugal pump 3 and enters the hydrocyclone 5 from the feed pipe along the tangential direction at a high speed. Due to the limitation of the outer cylinder wall, the liquid is forced to rotate from top to bottom. The solid particles in the outer vortex are subjected to centrifugal force. When the centrifugal force on the solid particles is greater than the liquid resistance generated by the movement, the solid particles will overcome the liquid resistance and move toward the wall, separate from the suspension, and the particles reaching the vicinity of the wall are pushed by the continuous liquid, move downward along the wall, and gather near the bottom flow outlet to form a greatly thickened struvite precipitate, which is discharged from the precipitation discharge pipe 6 at the bottom of the hydrocyclone 5. The separated and purified liquid and some fine struvite particles rotate downward and continue to move. After entering the conical section, the liquid rotation speed is accelerated due to the gradual reduction of the inner diameter of the hydrocyclone 5. Since the pressure distribution along the radial direction is uneven when the liquid generates eddy current motion, the closer to the axis, the smaller it is, and it approaches zero when it reaches the axis, forming a low pressure area or even a vacuum area, causing the liquid to move toward the axis. At the same time, since the bottom flow port of the hydrocyclone 5 is greatly reduced, the liquid cannot be discharged quickly from the bottom flow port, and the overflow port in the center of the top cover of the cyclone chamber, because it is in a low-pressure area, allows part of the liquid to move toward it, thereby forming an upward rotational motion, and is discharged from the overflow port into the horizontal separation column 7. The liquid enters the horizontal separation column 7, and due to inertia, the liquid continues to make centrifugal motion in the horizontal separation column 7, so that the liquid and the fine struvite particles are further separated. The inner diameter of the horizontal separation column 7 is larger than the inner diameter of the sewage discharge pipe 2, so the water in the horizontal separation column 7 can be returned to the front end of the hydrocyclone 5 through the principle of the venturi tube 4. The small particle precipitation in the reflux water can be used as a crystal seed, and due to the uneven flow rate at the elbow, tee, etc., a larger precipitation is formed, which is mixed with the mixed liquid and enters the hydrocyclone 5 again, thereby increasing the particle size of the struvite, reducing the amount of precipitant used, and saving the sewage treatment cost.

[0039] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A device for separating ammonia nitrogen from sewage by struvite precipitation, characterized in that: The invention comprises a mixing pool (1), wherein the mixing pool (1) is respectively provided with a sewage inlet (11), a magnesium source inlet (12) and a phosphorus source inlet (13); a sewage discharge pipe (2) is provided at the bottom of the mixing pool (1); a hydrocyclone (5) is provided at the other end of the sewage discharge pipe (2); a centrifugal pump (3) and a venturi tube (4) are sequentially provided on the sewage discharge pipe (2); a sedimentation discharge pipe (6) is provided at the bottom of the hydrocyclone (5); a horizontal separation column (7) is provided at the water outlet at the top of the hydrocyclone (5); a drainage pipe (8) is provided at the end of the horizontal separation column (7); and the bottom of the end of the horizontal separation column (7) is connected to the venturi tube (4) through a pipe.

2. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: A stirring paddle (14) is arranged in the mixing tank (1), and a motor (15) for controlling the rotation of the stirring paddle (14) is arranged on the top of the stirring paddle (14).

3. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: The venturi tube (4) is close to the inlet end of the hydrocyclone (5).

4. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: The inner diameter of the horizontal separation column (7) is greater than the inner diameter of the sewage discharge pipe (2).

5. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: The horizontal separation column (7) is a horizontally arranged cylindrical structure.

6. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: The sewage discharge pipe (2) is provided with a first valve (21), the sediment discharge pipe (6) is provided with a second valve (61), and the connecting pipe between the horizontal separation column (7) and the venturi tube (4) is provided with a third valve (71).

7. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 6, characterized in that: The first valve (21), the second valve (61) and the third valve (71) are all flow control valves.

8. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: A pH monitor is provided in the mixing tank (1).

9. The device for separating ammonia nitrogen from sewage by struvite precipitation according to claim 1, characterized in that: A pressure gauge and a flow meter are provided between the centrifugal pump (3) and the venturi tube (4).

10. A separation method of ammonia nitrogen in wastewater by struvite precipitation according to any one of claims 1 to 9, characterized in that: The following steps are included: Step 1: adding a magnesium source and a phosphorus source into the sewage containing ammonia nitrogen and stirring to mix; Step 2: The mixed sewage in step 1 is passed through a venturi tube (4) into a hydrocyclone (5) to separate the precipitate from the solution; Step 3: The sewage discharged from the hydrocyclone (5) partially flows back to the venturi tube (4) through the horizontal separation column (7) and enters the hydrocyclone (5) again for sedimentation cycle.

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