Cascade-based ammonia nitrogen emission index control technology

Abstract

The invention relates to the technical field of sewage treatment, and discloses an ammonia nitrogen emission index control technology based on cascade connection, and the control technology works by connecting an auxiliary loop and a main loop in series. And the auxiliary loop consists of an inner ring controller, an aeration fan and an aerobic tank. The main loop is composed of an outer ring controller, an auxiliary loop and a secondary sedimentation tank. The inner ring controller receives the target dissolved oxygen concentration of the aerobic tank and the actual dissolved oxygen concentration of the aerobic tank, compares the dissolved oxygen concentration error of the aerobic tank, and calculates the power of the aeration fan through a PID (Proportion Integration Differentiation) algorithm. The outer ring controller receives the ammonia nitrogen target emission concentration and the actual ammonia nitrogen emission concentration, compares the ammonia nitrogen target emission concentration with the actual ammonia nitrogen emission concentration to obtain an ammonia nitrogen concentration error, and calculates the target dissolved oxygen concentration of the aerobic tank through a PID algorithm. Compared with the prior art, the method has the advantages that the dynamic tracking performance of the system is improved, the good dynamic tracking performance is achieved, accurate control over the ammonia nitrogen concentration is achieved, the good energy-saving characteristic is achieved, and meanwhile the good robustness is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a cascade-based ammonia nitrogen emission index control technology. Background Art

[0002] Ammonia nitrogen emissions can cause multiple environmental hazards. In the aquatic environment, ammonia nitrogen can cause eutrophication of water bodies. In lakes and rivers, excessive ammonia nitrogen can cause aquatic plants such as algae to multiply in large numbers. These algae will form a thick layer on the water surface, blocking sunlight from reaching the water and reducing the production of dissolved oxygen in the water. After the algae die, their remains are decomposed by microorganisms. This process consumes a large amount of dissolved oxygen, causing fish and other aquatic organisms in the water to die due to lack of oxygen. Ammonia nitrogen is also toxic to aquatic organisms. When the concentration of ammonia nitrogen is high, it will directly poison aquatic animals such as fish. Even lower concentrations of ammonia nitrogen may affect the physiological functions of aquatic organisms and reduce their immunity and reproductive capacity. In terms of the atmospheric environment, part of the ammonia in ammonia nitrogen will volatilize into the atmosphere. Ammonia is an alkaline gas. It will react with acidic substances in the atmosphere such as sulfur dioxide and nitrogen oxides to form secondary particulate matter. These particulate matter will reduce atmospheric visibility, aggravate haze weather, and have adverse effects on the human respiratory system.

[0003] A2O is a sewage treatment process, namely the anaerobic-anoxic-oxygen process, which can simultaneously remove nutrients such as nitrogen and phosphorus from sewage, especially the emission of ammonia nitrogen. It has good effluent quality and effectively prevents eutrophication of water bodies. It is widely used in urban sewage treatment plants and various industrial wastewater treatment facilities. However, the current A2O treatment still faces problems such as low automation, high energy consumption, and low control accuracy, which limits the effect of ammonia nitrogen emission treatment.

[0004] Patent document 1 (CN202420553488) discloses a combined device for treating tail water of fish ponds. The gear 2 is driven by meshing to rotate and drive the stirring paddle to stir the water and reagents in the stirring barrel. The water inside the separation box is separated by a purifier and a ceramic membrane to achieve the effect of efficiently removing ammonia and nitrogen substances, making the outflowing water cleaner and suitable for the survival of aquatic organisms.

[0005] Patent document 2 (CN202411399129.4) collects sludge content data contained in a water pool in an aerobic granular sludge system through a preset particle size detector; performs predictive calculations on the sludge content data regarding the sludge oxygen demand to obtain target oxygen demand data for the water pool; performs parameter control processing on the fan frequency corresponding to the current dissolved oxygen concentration data according to the target oxygen demand data, and outputs optimized frequency data of the fan frequency; and feeds back the optimized frequency data to the fan control system so that the fan control system can optimize and adjust the fan frequency.

[0006] The above two documents regulate sewage treatment indicators through mechanical or computer programs, but both fail to organically combine ammonia nitrogen indicator control and dissolved oxygen concentration control, and fail to establish an accurate and low-energy dissolved oxygen control plan. Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] In view of the shortcomings of the prior art, the present invention provides a cascade-based ammonia nitrogen emission index control technology, which has the advantages of improving the ammonia nitrogen concentration emission treatment effect of the A2O process, increasing the dissolved oxygen concentration control accuracy, and reducing the energy consumption of sewage treatment. It solves the problem that the existing sewage treatment regulation has not established an accurate and low-energy dissolved oxygen control scheme.

[0009] (II) Technical solution

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a cascade-based ammonia nitrogen emission index control technology, which is composed of two control loops, an auxiliary loop and a main loop, connected in series to work.

[0011] Preferably, the auxiliary loop is composed of an inner loop controller C SC (S), aeration fan and aerobic tank.

[0012] Preferably, the main loop is controlled by an outer loop controller C main (S), auxiliary circuit and secondary sedimentation tank.

[0013] Preferably, the inner loop controller C SC (S) Target dissolved oxygen concentration DO by receiving aerobic tank T Compared with the actual dissolved oxygen concentration DO in the aerobic pool, the dissolved oxygen concentration error e in the aerobic pool is obtained. DO =DO T -DO, the aeration fan power P is calculated by PID algorithm fan , to control the actual dissolved oxygen concentration in the aerobic pool to adjust the sewage quality in the aerobic pool. The aeration fan power calculation formula is:

[0014]

[0015] Among them, K p,sc , K i,sc and K d,sc is an adjustable control parameter, (t) represents time, K p,sc e DO (t) represents the error of dissolved oxygen concentration in the aerobic pool at time (t), It represents the integration of the dissolved oxygen concentration error in the aerobic pool from the initial time 0 to the time (t), accumulating the cumulative effect of the error in the past time period. Represents the rate of change of dissolved oxygen concentration error.

[0016] Preferably, the aeration fan is adjusted by changing the aeration fan power P fan , change the aeration volume of the aerobic pool.

[0017] Preferably, a biochemical reaction occurs in the aerobic pool, consuming dissolved oxygen and oxidizing ammonia nitrogen, and the treated aerobic pool wastewater is discharged into the secondary sedimentation tank. At the same time, the actual dissolved oxygen concentration DO of the aerobic pool is fed back to the inner loop controller in real time through the dissolved oxygen concentration sensor in the aerobic pool.

[0018] Preferably, the outer loop controller C main (S) By receiving the target emission concentration of ammonia nitrogen and actual ammonia nitrogen emission concentration Compare the ammonia nitrogen concentration error The target dissolved oxygen concentration DO of the aerobic pool is calculated by PID algorithm r , and output DO to the inner loop controller r , in order to control the actual ammonia nitrogen emission concentration. r The calculation formula is;

[0019]

[0020] Among them, K p,main , K i,main and K d,main is an adjustable control parameter, represents the ammonia nitrogen concentration error at time (t), Represents the cumulative effect of the ammonia nitrogen concentration error from the initial time 0 to time (t), Represents the rate of change of ammonia nitrogen concentration error.

[0021] Preferably, the outlet of the secondary sedimentation tank is equipped with an ammonia nitrogen concentration sensor, which can feed back the actual ammonia nitrogen emission concentration to the outer loop controller in real time.

[0022] Preferably, the adjustable control parameter K p,sc , K i,sc and K d,sc It should meet the following requirements: the actual dissolved oxygen concentration in the aerobic tank under steady-state conditions should be equal to the target dissolved oxygen concentration in the aerobic tank; the power of the aeration fan should never exceed its maximum allowable power during the dynamic adjustment of dissolved oxygen.

[0023] Preferably, the K p,main , K i,main and K d,main The actual ammonia nitrogen emission concentration should always not exceed the required range of ammonia nitrogen emission indicators during the dynamic adjustment process.

[0024] Compared with the prior art, the present invention provides a cascade-based ammonia nitrogen emission index control technology, which has the following beneficial effects:

[0025] 1. The present invention adopts cascade control mode, which is divided into a main loop and an auxiliary loop to control the ammonia nitrogen concentration and the dissolved oxygen concentration respectively, which can effectively reduce the interference of system hysteresis on the control quality, improve the dynamic tracking performance of the system, and has good dynamic tracking performance.

[0026] 2. The present invention realizes precise control of ammonia nitrogen concentration through a feedback control scheme, and controls the ammonia nitrogen concentration near the expected value, which can not only ensure that the ammonia nitrogen concentration does not exceed the emission requirements, but also avoid increasing the energy consumption of the sewage treatment system due to demanding too low ammonia nitrogen concentration, and has good energy-saving characteristics.

[0027] 3. The present invention realizes precise control of dissolved oxygen concentration through a feedback control scheme, improves the accuracy of dissolved oxygen concentration control, reduces the impact of dissolved oxygen disturbance on ammonia nitrogen emission control, and has good robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The control principle diagram of the present invention is shown in FIG. The auxiliary loop and the main loop are connected in series to work. The auxiliary loop is controlled by the inner loop controller C SC (S), aeration fan and aerobic tank, the main circuit is composed of an outer loop controller C main (S), auxiliary circuit and secondary sedimentation tank. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example

[0031] like Figure 1 As shown, the present invention provides a cascade-based ammonia nitrogen emission index control technology, comprising the following steps:

[0032] The physical components are mechanically connected in the order of pretreatment, primary sedimentation tank, anaerobic tank, anoxic tank, aerobic tank, secondary sedimentation tank and sludge treatment, and the aerobic tank is connected to the aeration fan.

[0033] Pretreatment can remove large particles of impurities, primary sedimentation tanks can remove suspended solids, anaerobic tanks and anoxic tanks are used for denitrification, aerobic tanks are used for nitrification, secondary sedimentation tanks are used for mud and water separation, and sludge treatment processes the remaining sludge to gradually remove various pollutants in sewage. Aeration fans provide dissolved oxygen for aerobic tanks. At the same time, through the adjustment of aeration fans, it can be ensured that there is enough dissolved oxygen in the aerobic tank to support the metabolic activities of microorganisms.

[0034] Place the dissolved oxygen concentration sensor in the aerobic tank and the ammonia nitrogen concentration sensor at the outlet of the secondary sedimentation tank.

[0035] Dissolved oxygen is a key factor for the nitrification reaction of microorganisms in aerobic tanks. By real-time monitoring of dissolved oxygen concentration, the power of the aeration fan can be adjusted in time to ensure that the dissolved oxygen concentration in the aerobic tank is maintained within an appropriate range, thereby ensuring the smooth progress of the nitrification reaction. The ammonia nitrogen concentration at the outlet of the secondary sedimentation tank directly reflects whether the treated sewage meets the discharge standards. By real-time monitoring of ammonia nitrogen concentration, the control strategy can be adjusted in time to ensure that ammonia nitrogen emissions meet the requirements.

[0036] According to industry requirements, determine the ammonia nitrogen emission range [0, C max ], where C max is the maximum allowable ammonia nitrogen emission concentration, and the ammonia nitrogen target emission concentration is taken as

[0037] Outer loop controller C main (S) By receiving the target emission concentration of ammonia nitrogen and actual ammonia nitrogen emission concentration Compare the ammonia nitrogen concentration error The target dissolved oxygen concentration DO of the aerobic pool is calculated by PID algorithm r , and output DO to the inner loop controller r , in order to control the actual ammonia nitrogen emission concentration. r The calculation formula is;

[0038]

[0039] Among them, K p,main , K i,main and K d,main is an adjustable control parameter, K p,main e NH3 (t) represents the ammonia nitrogen concentration error at time (t), Represents the cumulative effect of the ammonia nitrogen concentration error from the initial time 0 to time (t), Represents the rate of change of ammonia nitrogen concentration error, K p,main , K i,main and K d,mainDuring the adjustment process, the actual ammonia nitrogen emission concentration should not exceed the required range of ammonia nitrogen emission indicators during the dynamic adjustment process. The outer loop controller C main (S) The target dissolved oxygen concentration of the aerobic pool is calculated through the PID algorithm, thereby indirectly controlling the ammonia nitrogen concentration. This indirect control method can make full use of the relationship between dissolved oxygen and ammonia nitrogen removal to achieve more accurate ammonia nitrogen control.

[0040] Inner loop controller C SC (S) Target dissolved oxygen concentration DO by receiving aerobic tank T Compared with the actual dissolved oxygen concentration DO in the aerobic pool, the dissolved oxygen concentration error e in the aerobic pool is obtained. DO =DO T -DO, the aeration fan power P is calculated by PID algorithm fan , to control the actual dissolved oxygen concentration in the aerobic pool to adjust the sewage quality in the aerobic pool. The aeration fan power calculation formula is:

[0041]

[0042] Among them, K p,sc , K i,sc and K d,sc is an adjustable control parameter, (t) represents time, K p,sc e DO (t) represents the error of dissolved oxygen concentration in the aerobic pool at time (t), It represents the integration of the dissolved oxygen concentration error in the aerobic pool from the initial time 0 to the time (t), accumulating the cumulative effect of the error in the past time period. Represents the rate of change of dissolved oxygen concentration error, adjustable control parameter K p,sc , K i,sc and K d,sc The regulation process should meet the following requirements: the actual dissolved oxygen concentration in the aerobic pool under steady-state conditions should be equal to the target dissolved oxygen concentration in the aerobic pool; the aeration fan power should never exceed its maximum allowable power during the dynamic adjustment of dissolved oxygen. The inner loop controller C SC (S) The power of the aeration fan is calculated through the PID algorithm to directly control the dissolved oxygen concentration in the aerobic tank. This direct control method can quickly respond to changes in the dissolved oxygen concentration and ensure that the dissolved oxygen concentration in the aerobic tank is maintained near the target value.

[0043] The aeration fan changes the aeration flow rate after receiving the aeration fan power signal to adjust the dissolved oxygen concentration in the aerobic tank. The dissolved oxygen sensor in the aerobic tank measures the dissolved oxygen concentration and feeds it back to the inner loop controller. At the same time, the ammonia nitrogen concentration sensor at the outlet of the secondary sedimentation tank measures the ammonia nitrogen concentration and feeds it back to the outer loop controller. By establishing an accurate and low-energy dissolved oxygen control solution, it can effectively improve the ammonia nitrogen removal efficiency, reduce energy consumption, optimize sewage treatment effects, improve system stability, and ensure that the effluent water quality meets the standards, with significant economic and environmental benefits.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cascade-based ammonia nitrogen emission index control technology, characterized in that: The two control circuits, the auxiliary circuit and the main circuit, are connected in series to work.

2. The cascade-based ammonia nitrogen emission index control technology according to claim 1 is characterized in that: The auxiliary loop is composed of an inner loop controller C SC (S), aeration fan and aerobic tank.

3. The cascade-based ammonia nitrogen emission index control technology according to claim 1 is characterized in that: The main loop is composed of an outer loop controller C main (S), auxiliary circuit and secondary sedimentation tank.

4. The cascade-based ammonia nitrogen emission index control technology according to claim 2 is characterized in that: The inner loop controller C SC (S) Target dissolved oxygen concentration DO by receiving aerobic tank T Compared with the actual dissolved oxygen concentration DO in the aerobic pool, the dissolved oxygen concentration error e in the aerobic pool is obtained. DO =DO T -DO, the aeration fan power P is calculated by PID algorithm fan , to control the actual dissolved oxygen concentration in the aerobic pool to adjust the sewage quality in the aerobic pool. The aeration fan power calculation formula is: Among them, K p,sc , K i,sc and K d,sc is an adjustable control parameter, (t) represents time, K p,sc e DO (t) represents the error of dissolved oxygen concentration in the aerobic pool at time (t), It represents the integration of the dissolved oxygen concentration error in the aerobic pool from the initial time 0 to the time (t), accumulating the cumulative effect of the error in the past time period. Represents the rate of change of dissolved oxygen concentration error.

5. The cascade-based ammonia nitrogen emission index control technology according to claim 2 is characterized in that: The aeration fan is adjusted by changing the aeration fan power P fan , change the aeration volume of the aerobic pool.

6. The cascade-based ammonia nitrogen emission index control technology according to claim 2 is characterized in that: Biochemical reactions occur in the aerobic pool, consuming dissolved oxygen and oxidizing ammonia nitrogen, and the treated aerobic pool wastewater is discharged into the secondary sedimentation tank. At the same time, the actual dissolved oxygen concentration DO of the aerobic pool is fed back to the inner loop controller in real time through the dissolved oxygen concentration sensor in the aerobic pool.

7. The cascade-based ammonia nitrogen emission index control technology according to claim 3 is characterized in that: The outer loop controller C main (S) By receiving the target emission concentration of ammonia nitrogen and actual ammonia nitrogen emission concentration Compare the ammonia nitrogen concentration error The target dissolved oxygen concentration DO of the aerobic pool is calculated by PID algorithm r , and output DO to the inner loop controller r , in order to control the actual ammonia nitrogen emission concentration. r The calculation formula is; Among them, K p,main , K i,main and K d,main is an adjustable control parameter, represents the ammonia nitrogen concentration error at time (t), Represents the cumulative effect of the ammonia nitrogen concentration error from the initial time 0 to time (t), Represents the rate of change of ammonia nitrogen concentration error.

8. The cascade-based ammonia nitrogen emission index control technology according to claim 3 is characterized in that: The outlet of the secondary sedimentation tank is equipped with an ammonia nitrogen concentration sensor, which can feed back the actual ammonia nitrogen emission concentration to the outer loop controller in real time.

9. The cascade-based ammonia nitrogen emission index control technology according to claim 4 is characterized in that: The adjustable control parameter K p,sc , K i,sc and K d,sc It should meet the following requirements: the actual dissolved oxygen concentration in the aerobic tank under steady-state conditions should be equal to the target dissolved oxygen concentration in the aerobic tank; the power of the aeration fan should never exceed its maximum allowable power during the dynamic adjustment of dissolved oxygen.

10. The cascade-based ammonia nitrogen emission index control technology according to claim 7, characterized in that: The K p,main , K i,main and K d,main The actual ammonia nitrogen emission concentration should always not exceed the required range of ammonia nitrogen emission indicators during the dynamic adjustment process.

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