Gas stripping sludge reflux device, operation method and gas stripping sludge calculation method

Abstract

The invention provides a non-clogging gas stripping sludge backflow device which comprises a cylinder, a connecting flange and a gas inlet pipe, the top end of the cylinder is sealed, the bottom of the cylinder is provided with a sludge inlet base used for allowing sludge to enter the cylinder, the side wall of the cylinder is connected with a mixing pipe, and the connecting flange is fixedly connected to the tail end of the mixing pipe and is in coupling connection with a backflow pipeline. The air inlet pipe is fixedly connected to the side wall of the cylinder and communicated with an existing blast room, and the connecting position of the air inlet pipe is located between the mixing pipe and the sludge inlet base. The invention also provides a gas stripping sludge backflow operation method and a gas stripping sludge calculation method, the backflow of the nitrification liquid and the sludge can be realized only by using a gas source emitted by an existing blower room of a sewage treatment plant and provided by an aeration air pipe bypass, the high backflow ratio of the sludge can be realized under the condition of low energy consumption, and the method has the advantages of low energy consumption, small occupied area and the like, and is suitable for popularization and application. Therefore, the daily operation and maintenance cost of a sewage treatment plant is remarkably improved, and the overall investment cost is also reduced.

Description

Technical Field

[0001] The invention relates to the technical field of sewage purification, and in particular to an air lift sludge return device, an operation method and an air lift sludge calculation method. Background Art

[0002] The sludge return pump is mainly involved in the mixed liquor return and denitrification process in the sewage treatment process. As a key equipment in a water purification plant, the sludge return pump's main function is to maintain a stable activated sludge concentration (MLSS) by continuously returning the treated sludge in the sedimentation tank or other sludge treatment equipment to the biochemical reaction tank. It not only helps the uniform distribution and exchange of anaerobic and aerobic bacteria, and improves the biological denitrification and phosphorus removal effect, but also effectively prevents sludge swelling, improves sewage treatment efficiency and effluent water quality, and ensures the stable operation of the sewage treatment system. However, in the actual operation of the water purification plant, the traditional paddle sludge return pump highlights the following shortcomings: High energy consumption and carbon emissions: Traditional paddle sludge return pumps usually rely on electric drive motors to operate, and their efficiency is relatively low. They have relatively high energy consumption and carbon emissions, which do not meet the current environmental protection requirements of energy conservation, emission reduction, pollution reduction and carbon reduction, and will increase the operating costs of sewage treatment plants during long-term operation.

[0003] High maintenance cost: Due to the complex structure of the traditional paddle sludge return pump and the long-term immersion in the sludge mixture, its impeller, bearings and other parts are prone to wear and tear, and specific equipment maintenance personnel are required to regularly inspect and replace worn parts, perform troubleshooting, cleaning and lubrication to ensure the normal operation of the pump, which increases operating costs and time costs.

[0004] Poor operation stability: Traditional paddle sludge return pumps are easily affected by a large amount of solid particles, fibers and other impurities in the sludge during operation, causing blockage or jamming, thus affecting the stable operation of the pump.

[0005] Limited adjustment range: The flow and pressure adjustment range of traditional paddle sludge return pumps is relatively limited, making it difficult to adapt to changes in return demand under different process conditions. This may result in poor treatment results or excessive energy consumption.

[0006] Large noise and vibration: Traditional paddle sludge return pumps may generate large noise and vibration during operation, which not only affects the working environment, but may also have an adverse effect on the structure and service life of the pump. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides an air lift sludge return device, an operation method and an air lift sludge calculation method. In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A non-clogging air lift sludge return device comprises a cylinder, a connecting flange and an air inlet pipe. The top of the cylinder is sealed, the bottom is provided with a mud inlet base for sludge to enter the cylinder, and the side wall is connected to a mixing pipe. The connecting flange is fixedly connected to the end of the mixing pipe and coupled with the return pipe. The air inlet pipe is fixedly connected to the side wall of the cylinder and connected to the existing blast room. The air inlet pipe connection position is located between the mixing pipe and the mud inlet base.

[0008] Furthermore, a limiting block is fixedly connected to the connecting flange, a slot is provided on the limiting block, the return pipe is installed on a base for fixing the return pipe, a blocking block is provided on the base, and the blocking block cooperates with the slot to press the connecting flange against the end of the return pipe.

[0009] Furthermore, two parallel limit columns are fixedly connected to the base, and the limit columns are respectively located on both sides of the reflux pipe. The limit block is provided with a limit groove that cooperates with the two limit columns, and the limit groove is used to clamp the limit block between the limit columns.

[0010] Furthermore, the matching portion between the return pipe and the connecting flange is configured to be wedge-shaped so that the cylinder can be installed on the return pipe from top to bottom.

[0011] Furthermore, a lifting lug for hanging a rope is fixedly connected to the top of the cylinder.

[0012] Furthermore, a counterweight cylinder is fixedly connected to the top end of the cylinder.

[0013] Furthermore, a vortex structure is provided in the cylinder, and the airflow entering the cylinder through the air inlet pipe flows into the return pipe along the vortex structure.

[0014] A method for operating the airlift sludge reflux operation, using the reflux device as described above, comprises the following steps: S1. Lift the reflux device, clamp the limit block between the two limit columns of the base, lower the reflux device, and make it slide between the limit columns. When the clamping groove of the limit block is clamped in the clamping block on the base, the reflux device is aligned with the reflux pipe and stabilized under the joint action of the two limit columns, the limit block and the clamping block. At this time, the mud inlet base of the reflux device falls on the bottom base surface; S2. Open the ball valve of the air inlet pipe to allow part of the gas produced by the Roots blower in the existing blower room of the sewage treatment plant to enter the cylinder through the air inlet pipe, generating bubbling behavior. The bubbles rise due to buoyancy and impact force and fill the entire cylinder. A gas-liquid-solid three-phase mixture is formed in the cylinder, and a liquid-solid two-phase mixture is formed outside the cylinder. The density of the three-phase mixture is less than that of the two-phase mixture. The three-phase mixture flows out through the reflux pipe, driving the muddy water at the bottom of the cylinder to continuously enter the cylinder and be discharged, forming a stable sludge return.

[0015] Furthermore, in S2, the compressed air flow entering the cylinder from the air inlet pipe passes through the vortex structure in the cylinder, driving the mud and water entering the cylinder from the mud inlet base to generate a gas-liquid-solid three-phase fluid vortex, and finally discharged from the return pipe.

[0016] A method for calculating airlift sludge, according to the proposed lifting height L and the immersion depth H of the reflux device, the theoretical airlift reflux air volume is calculated, and the density of the three-phase mixed liquid ρ2 is less than the two-phase mixed liquid ρ1. According to the liquid equilibrium condition, under the pressure of the water column of the airlift sludge reflux device immersed below the liquid surface, the gas-liquid-solid three-phase mixed liquid rises to the total height of L, and the equilibrium relationship can be listed as: ρ1H=ρ2L; Where: ρ1 is the density of the sludge mixed liquid outside the sludge return device (kg / m 3 ), ρ2 is the density of the solid-liquid-gas three-phase mixed liquid in the sludge reflow device (kg / m 3 ), H is the submerged depth of the sludge return device m, L is the sum of the total lifting height of the sludge return device and the submerged depth m, and H / L is the submerged ratio; Similarly, the principle of normal working of gas lift is: as long as ρ1H>ρ2L, the three-phase mixed liquid flows out through the reflux pipe, driving the muddy water at the bottom of the cylinder to continuously enter the cylinder and be discharged, forming a stable sludge reflux; The theoretical air stripping reflux air consumption is calculated according to the following formula: ; Where: W is the amount of compressed gas emitted by the blower m 3 / h, K is the safety factor, generally 1.2, Q is the designed sludge lifting flow rate m 3 / h, H is the proposed sludge lifting height in m; The efficiency coefficient is generally taken as 0.35~0.45; h is the immersion depth of the air lift reflux pump m.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The airlift sludge reflux device provided by the present invention has a simple structure, low cost, convenient installation, no maintenance required during operation, and is easy to control. At the same time, it has a large sludge lifting capacity, which is beneficial to improving the efficiency of water lifting treatment, and has a certain significance for energy saving and consumption reduction, efficiency improvement and carbon reduction in the operation process of sewage treatment plants; 2. When using the activated sludge method to treat sewage, if the design is A 2In the O process, the sludge internal reflow ratio is usually set between 200% and 400%. In order to ensure that the effluent quality meets the discharge standards, the sludge concentration in actual operation is required to be as high as possible, resulting in the sludge reflow volume generally far exceeding the actual demand. When using a traditional paddle-type reflow pump driven by electric energy, this excessive reflow will inevitably increase the consumption of electric energy and the risk of pump damage. The air lift sludge reflow device uses air lifting technology as fluid power, and does not require traditional water pumps that are prone to damage and blockage. Parts such as underwater paddles, at the same time, it does not require electricity to drive, only the existing blower room of the sewage treatment plant, and the air source provided by the aeration duct bypass can realize the nitrification liquid and sludge reflow, and can achieve a high sludge reflow ratio under low energy consumption conditions. It has the advantages of low energy consumption and small footprint, which not only significantly improves the daily operation and maintenance costs of the sewage treatment plant, but also reduces the overall investment cost; 3. The number of traditional paddle-type reflux pumps directly determines the adjustment gear of the reflux ratio in the process, which can usually only be scheduled at fixed gears such as 100%, 200%, etc. The reflux ratio of the sludge mixed liquid returned by the sludge reflux pump based on the air lift principle can be adjusted by the amount of compressed air blown out by the blower, thereby achieving a larger reflux ratio. Compared with the traditional process of reflux of nitrification liquid through a water pump, this process can achieve dozens or even hundreds of times of sewage reflux on the basis of low energy consumption. At the same time, although the capacity of a single group of air lift reflux pumps is limited, the reflux ratio combination can be achieved through the synergy of multiple systems, thereby realizing precise control of the reflux volume and adjustment according to real-time needs. It is an efficient strategy that can accurately reflux nitrification liquid according to actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the main structure of an embodiment of the present invention; Figure 2 It is a schematic diagram of the top view structure of the limit block according to an embodiment of the present invention.

[0019] In the above drawings: base 1, block 2, limit column 3, cylinder 4, connecting flange 5, air inlet pipe 6, mixing pipe 7, limit block 8, slot 9, limit slot 10, lifting ear 11, counterweight cylinder 12, vortex structure 13, return pipe 14, mud inlet base 15. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Please refer to Figure 1 , Figure 2As shown, a non-clogging air lift sludge return device includes a cylinder 4, a connecting flange 5 and an air inlet pipe 6. The top of the cylinder 4 is sealed, and a mud inlet base 15 for sludge to enter the cylinder 4 is provided at the bottom. A mixing tube 7 is connected to the side wall. The mixing tube 7 adopts a conical tube design to increase the pressure in the mixing tube 7. The connecting flange 5 is fixedly connected to the end of the mixing tube 7 and coupled with the return pipe 14. The air inlet pipe 6 is fixedly connected to the side wall of the cylinder 4 and connected to the existing blast room. The connection position of the air inlet pipe 6 is located between the mixing tube 7 and the mud inlet base.

[0022] The cylinder 4 is inflated through the air inlet pipe 6, and the air flow forms a gas-liquid-solid three-phase mixed liquid in the cylinder 4. The three-phase mixed liquid flows upward through the mixing pipe 7 and flows out from the return pipe 14. At the same time, the air flow changes the pressure in the cylinder 4, so that the liquid-solid two-phase mud-water mixture at the bottom enters the cylinder 4 from the mud inlet base 15, and forms a three-phase mixed liquid with the newly-introduced gas and is discharged from the return pipe 14, completing the reflux work.

[0023] In this embodiment, if Figure 1 As shown, the connection flange 5 is fixedly connected to a limit block 8, the limit block 8 is provided with a slot 9, the return pipe 14 is mounted on a base 1 for fixing the return pipe 14, the base 1 is provided with a block 2, the block 2 cooperates with the slot 9 to abut the connection flange 5 against the end of the return pipe 14. The cooperation of the block 2 and the slot 9 facilitates quick alignment and installation of the return device, and is convenient for operation.

[0024] In this embodiment, if Figure 2 As shown, two parallel limiting columns 3 are fixedly connected to the base 1, and the limiting columns 3 are respectively located on both sides of the reflux pipe 14. The limiting block 8 is provided with limiting grooves 10 that match the two limiting columns 3, and the limiting grooves 10 are used to clamp the limiting block 8 between the limiting columns 3. The limiting block 8 uses a limiting groove 10 of a certain thickness to match the limiting column 3, so that the reflux device is relatively stable when sliding from top to bottom on the limiting column 3.

[0025] In another embodiment, Figure 1 As shown, the matching part of the return pipe 14 and the connecting flange 5 is set in a wedge shape, so that the cylinder 4 is installed on the return pipe 14 from top to bottom. Such a design facilitates the alignment and matching of the return pipe 14 and the connecting flange 5, and realizes automatic installation without the need for staff to go into the water for operation.

[0026] In this embodiment, if Figure 1 As shown, the top of the cylinder 4 is fixedly connected with a lifting lug 11 for hanging a rope, which is convenient for hoisting operation and installation, and saves labor and is convenient.

[0027] In this embodiment, if Figure 1As shown, the top of the cylinder 4 is fixedly connected with a weight cylinder 12, which is used to overcome the buoyancy effect of sinking.

[0028] In another embodiment, please refer to Figure 1 As shown, a vortex structure 13 is arranged in the cylinder 4, and the airflow from the air inlet pipe 6 entering the cylinder 4 flows into the return pipe 14 along the vortex structure 13. The cylinder 4 is enhanced to absorb muddy water at the bottom, saving power resources.

[0029] The present invention also provides an airlift sludge reflux operation method, using the above reflux device, comprising the following steps: S1, lift the reflux device, clamp the limit block 8 between the two limit columns 3 of the base 1, lower the reflux device, and make it slide between the limit columns 3. When the clamping groove 9 of the limit block 8 is clamped in the clamping block 2 on the base 1, the reflux device is aligned with the reflux pipe 14 and stabilized under the joint action of the two limit columns 3, the limit block 8 and the clamping block 2. At this time, the mud inlet base 15 of the reflux device falls on the bottom base surface; S2. Open the ball valve of the air inlet pipe 6, so that part of the gas generated by the Roots blower in the existing blower room of the sewage treatment plant is passed into the cylinder 4 through the air inlet pipe 6, generating bubbling behavior. The bubbles rise due to buoyancy and impact force and fill the entire cylinder 4. A gas-liquid-solid three-phase mixed liquid is formed in the cylinder 4, and a liquid-solid two-phase mixed liquid is formed outside the cylinder 4. The density of the three-phase mixed liquid is less than that of the two-phase mixed liquid. The three-phase mixed liquid flows out through the reflux pipe 14, driving the muddy water at the bottom of the cylinder 4 to continuously enter the cylinder 4 and be discharged, forming a stable sludge return.

[0030] Furthermore, in S2, the compressed airflow entering the cylinder 4 from the air inlet pipe 6 drives the mud and water entering the cylinder 4 from the mud inlet base 15 to generate a gas-liquid-solid three-phase fluid vortex through the vortex structure in the cylinder 4, and finally discharged from the return pipe 14, thereby increasing the mud suction effect of the airflow in the cylinder 4.

[0031] The present invention also provides a method for calculating airlift sludge. According to the proposed lifting height L and the immersion depth H of the reflux device, the theoretical airlift reflux air volume is calculated, and the density ρ2 of the three-phase mixed liquid is less than the two-phase mixed liquid ρ1. According to the liquid balance condition, under the water column pressure of the part of the airlift sludge reflux device immersed below the liquid surface, the gas-liquid-solid three-phase mixed liquid rises to the total height L, and the equilibrium relationship can be listed as: ρ1H=ρ2L; Where: ρ1 is the density of the sludge mixed liquid outside the sludge return device (kg / m 3 ), ρ2 is the density of the solid-liquid-gas three-phase mixed liquid in the sludge reflow device (kg / m 3 ), H is the submerged depth of the sludge return device m, L is the sum of the total lifting height of the sludge return device and the submerged depth m, and H / L is the submerged ratio; Similarly, the principle of normal working of gas lift is: as long as ρ1H>ρ2L, the three-phase mixed liquid flows out through the reflux pipe, driving the muddy water at the bottom of the cylinder to continuously enter the cylinder and be discharged, forming a stable sludge reflux; The theoretical air stripping reflux air consumption is calculated according to the following formula: ; Where: W is the amount of compressed gas emitted by the blower m 3 / h, K is the safety factor, generally 1.2, Q is the designed sludge lifting flow rate m 3 / h, H is the proposed sludge lifting height in m; The efficiency coefficient is generally taken as 0.35~0.45; h is the immersion depth of the air lift reflux pump m.

[0032] The reflow device and operation method have been successfully applied to the Malisi Water Purification Plant (Phase I and II) in Huarong County. The effluent of the water purification plant meets the Class A standard. Phase I and II have four integrated self-reflow improved oxidation ditches, each of which has an anaerobic zone, anoxic zone, aerobic zone and sedimentation zone from inside to outside. The treatment capacity is 40,000 tons / day, of which the water inlet of a single pool is 400m 3 / h, the effective retention time of the anaerobic zone is designed to be 1.0h, the pool depth is 6.1m and the effective volume is 417m3. The effective volume ratio of the anaerobic zone, anoxic zone and aerobic zone is 1:2:6. The original design of the single oxidation ditch uses 4 sludge return pumps with autocouplers, each with P=5kw, Q=100m 3 / h. In summer, the reflux ratio is usually set to 150%, and in winter, the reflux ratio is set to 300% to achieve stable and standard discharge. At this stage, the 1# oxidation ditch was originally planned to open two sludge return pumps for reflux. The sludge return ratio of 150% can achieve standard discharge of treated water quality. After the present invention is placed 6m underwater along the conduit and coupled and fixedly connected to the sludge return pipe, when the pressure gauge shows that the blower blowing pressure is greater than 6 atmospheres, according to the flow of the gas flowmeter, the gear-adjustable ball valve is opened and adjusted at this time. By adjusting the gas flow, the sludge return ratio is adjusted to 150%. After replacing the original two sludge return pumps with one gas lift sludge return device for 24 hours, the removal rates of COD, ammonia nitrogen, total phosphorus, and total nitrogen in the oxidation ditch effluent are compared with those before the pump body was replaced. The operating effect is shown in the following table: Table 1 Removal rate of organic matter in sewage under the condition of 150% sludge return ratio achieved by two submersible sewage pumps

[0033] Table 2 Removal rate of organic matter in sewage under the condition of 150% sludge return ratio achieved by one unit of the present invention

[0034] The energy consumption and carbon emission data of each reflux pump are as follows: Table 3 Power consumption, energy consumption and carbon emissions of sludge return pump

[0035] In actual implementation, it can be found that: on the one hand, one unit of the present invention not only replaces two 5kw sludge return pumps, but also theoretically can achieve an annual electricity saving of 43,800 kw, a reduction in energy consumption of 10.76tce and a carbon emission reduction of 42.66t. In the example sewage plant, each oxidation ditch was originally equipped with 4 5kw sludge return pumps, and there were 4 oxidation ditches in the plant area. A total of 16 5kw sludge return pumps can be replaced by the present invention. Theoretically, if the sludge return ratio reaches 150% in summer each year, the electricity consumption can be reduced by 350,400 kw, the energy consumption can be reduced by 43.04tce, and the carbon emission can be reduced by 170.64t. Theoretically, if the sludge return ratio reaches 300% in winter each year, the electricity consumption can be reduced by 700,800 kw, the energy consumption can be reduced by 86.08tce, and the carbon emission can be reduced by 341.28t. On the other hand, under the condition of unchanged process, the removal rates of pollutants COD, NH3-N, TP and TN in sewage can be increased by 1.99%, 0.42%, 3.11% and 5.58% respectively. While playing the role of energy saving, consumption reduction, pollution reduction and carbon reduction, it can significantly reduce its operation and maintenance costs.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A non-clogging airlift sludge return device, characterized in that: It includes a cylinder, a connecting flange and an air inlet pipe. The top of the cylinder is sealed, the bottom is provided with a mud inlet base for sludge to enter the cylinder, and a mixing pipe is connected to the side wall. The connecting flange is fixedly connected to the end of the mixing pipe and coupled with the return pipe. The air inlet pipe is fixedly connected to the side wall of the cylinder and connected to the existing blast room. The connection position of the air inlet pipe is located between the mixing pipe and the mud inlet base.

2. A non-clogging airlift sludge return device according to claim 1, characterized in that: A limiting block is fixedly connected to the connecting flange, a slot is provided on the limiting block, the return pipe is installed on a base for fixing the return pipe, a block is provided on the base, and the block cooperates with the slot to press the connecting flange against the end of the return pipe.

3. A non-clogging airlift sludge return device according to claim 2, characterized in that: The base is fixedly connected to two parallel limiting columns, the limiting columns are respectively located on both sides of the reflux pipe, the limiting block is provided with limiting grooves matching with the two limiting columns, and the limiting grooves are used to clamp the limiting block between the limiting columns.

4. A non-clogging airlift sludge return device according to claim 3, characterized in that: The matching part between the return pipe and the connecting flange is arranged in a wedge shape so that the cylinder can be installed on the return pipe from top to bottom.

5. The non-clogging airlift sludge return device according to claim 1, characterized in that: The top of the cylinder is fixedly connected with a lifting lug for hanging a rope.

6. The non-clogging airlift sludge return device according to claim 1, characterized in that: The top end of the cylinder is fixedly connected with a counterweight cylinder.

7. The non-clogging airlift sludge return device according to claim 1, characterized in that: A vortex structure is arranged in the cylinder, and the airflow entering the cylinder through the air inlet pipe flows into the return pipe along the vortex structure.

8. A method for reflux operation of airlift sludge, characterized in that: Using the reflux device as described in any one of claims 1 to 7, comprising the following steps: S1. Lift the reflux device, clamp the limit block between the two limit columns of the base, lower the reflux device, and make it slide between the limit columns. When the clamping groove of the limit block is clamped in the clamping block on the base, the reflux device is aligned with the reflux pipe and stabilized under the joint action of the two limit columns, the limit block and the clamping block. At this time, the mud inlet base of the reflux device falls on the bottom base surface; S2. Open the ball valve of the air inlet pipe to allow part of the gas produced by the Roots blower in the existing blower room of the sewage treatment plant to enter the cylinder through the air inlet pipe, generating bubbling behavior. The bubbles rise due to buoyancy and impact force and fill the entire cylinder. A gas-liquid-solid three-phase mixture is formed in the cylinder, and a liquid-solid two-phase mixture is formed outside the cylinder. The density of the three-phase mixture is less than that of the two-phase mixture. The three-phase mixture flows out through the reflux pipe, driving the muddy water at the bottom of the cylinder to continuously enter the cylinder and be discharged, forming a stable sludge return.

9. The air lift sludge return operation method according to claim 1, characterized in that: In S2, the compressed air flow entering the cylinder from the air inlet pipe passes through the vortex structure in the cylinder, driving the mud and water entering the cylinder from the mud inlet base to generate a gas-liquid-solid three-phase fluid vortex, and finally discharged from the return pipe.

10. A method for calculating airlift sludge, characterized in that: According to the proposed lifting height L and the immersion depth H of the reflux device, the theoretical air volume of the gas lift reflux is calculated, and the density of the three-phase mixed liquid ρ2 is less than the two-phase mixed liquid ρ1. According to the liquid balance condition, under the pressure of the water column of the part of the gas lift sludge reflux device immersed below the liquid surface, the gas-liquid-solid three-phase mixed liquid rises to the total height of L, and the equilibrium relationship can be listed as: ρ1H=ρ2L; Where: ρ1 is the density of the sludge mixed liquid outside the sludge return device (kg / m 3 ), ρ2 is the density of the solid-liquid-gas three-phase mixed liquid in the sludge reflow device (kg / m 3 ), H is the submerged depth of the sludge return device m, L is the sum of the total lifting height of the sludge return device and the submerged depth m, and H / L is the submerged ratio; Similarly, the principle of normal working of gas lift is: as long as ρ1H>ρ2L, the three-phase mixed liquid flows out through the reflux pipe, driving the muddy water at the bottom of the cylinder to continuously enter the cylinder and be discharged, forming a stable sludge reflux; The theoretical air stripping reflux air consumption is calculated according to the following formula: ； Where: W is the amount of compressed gas emitted by the blower m 3 / h, K is the safety factor, generally 1.2, Q is the designed sludge lifting flow rate m 3 / h, H is the planned sludge lifting height in m; The efficiency coefficient is generally taken as 0.35~0.45; h is the immersion depth of the air lift reflux pump m.

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