Accurate acid adjusting system suitable for continuous flow sewage treatment

Abstract

The invention discloses a precise acid regulating system suitable for continuous flow sewage treatment, which comprises a water distribution regulating tank for receiving continuous flow sewage, an acid adding unit for adding acid into the water distribution regulating tank and a control unit, and is characterized in that firstly, the acid is added into the water distribution regulating tank in a quantitative adding manner through the acid adding unit to carry out pH coarse regulation; the control unit calculates the fine adjustment amount of the pH according to the pH target value and the actual value after the rough adjustment of the pH by adopting a chemical dosage-pH-PID algorithm and controls the acid adding unit to add acid into the water distribution adjusting tank for the fine adjustment of the pH; through combination of coarse adjustment and fine adjustment, accurate addition of the acid liquor can be realized, the problems of excessive addition and hysteresis of the acid liquor are avoided, the dosage-pH-PID algorithm is adopted to control the addition flow of sulfuric acid, the actual pH value fluctuation is smaller, the problems of large fluctuation and hysteresis of PLC automatic acid control are solved, and a water quality guarantee is provided for stable operation of a subsequent process section.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and in particular relates to a precise acid regulating system suitable for continuous flow wastewater treatment. Background Art

[0002] Industrial wastewater has a large volume and complex composition, including a large number of organic and inorganic pollutants. In order to ensure that the effluent quality is stable and meets the standard, in the wastewater treatment project, each process section needs to detect or control the pH of the wastewater to ensure the best treatment effect. At present, industrial wastewater treatment mostly adopts the addition of acid or alkali solution to achieve the purpose of adjusting pH. However, the actual pH adjustment process of wastewater is a reaction process with time-varying, highly nonlinear and large time lag characteristics. The sewage treatment plant still uses manual adjustment or semi-automatic method to adjust pH. Its operation logic is that after exceeding / lowering the set pH value, the system issues corresponding instructions to control the start and stop of the acid agent valve, and the valve opening or dosing pump frequency is controlled according to manual experience. However, since it takes a certain amount of time for the agent to mix with the wastewater, and the water volume of the incoming water is generally volatile, the actual amount of the agent does not match the dosing demand, and the phenomenon of stopping acid addition at low pH and starting acid addition at high pH occurs. The pH control curve is wavy and fluctuates greatly, which affects the treatment effect of the downstream process section. In addition, the water inlet to the acid adjustment tanks of some existing sewage treatment plants fluctuates greatly, and the inability to add flow meters to the water inlet pipes of the adjustment tanks has greatly increased the difficulty of controlling precise pH adjustment. As a result, the actual application status of pH control is not ideal, with high labor intensity, high cost and unstable control effect.

[0003] Therefore, for continuous flow sewage treatment, it is necessary to solve the problems of rough dosage of chemicals, large pH fluctuations and hysteresis caused by traditional manual control or PLC automatic pH control. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a precise acid adjustment system suitable for continuous flow sewage treatment, so as to solve the problems of rough dosage of reagents, large pH fluctuation and hysteresis in traditional manual control or PLC automatic pH control.

[0005] The precise acid adjustment system for continuous flow sewage treatment of the present invention comprises a water distribution regulating tank for receiving continuous flow sewage, an acid adding unit and a control unit for adding acid to the water distribution regulating tank, wherein the acid adding unit first adds acid to the water distribution regulating tank in a quantitative manner for pH rough adjustment, and the control unit calculates the pH fine adjustment amount by using a dosage-pH-PID algorithm according to the pH target value and the actual value after pH rough adjustment, and controls the acid adding unit to add acid to the water distribution regulating tank for pH fine adjustment;

[0006] Further, the acid adding unit includes a first acid adding pump and a second acid adding pump which are respectively connected to the water distribution regulating tank pipeline, the first acid adding pump adds acid to the water distribution regulating tank to control the pH within the range of ±0.5 of the set target value, and the second acid adding pump adds acid to the water distribution regulating tank according to the addition flow calculated by the dosage-pH-PID algorithm of the control unit;

[0007] Further, the water distribution regulating tank is provided with a water inlet pipe, a water outlet pipe, and a first pH meter for detecting the actual pH after acid addition by the first acid liquid dosing pump and a second pH meter for setting the pH target value by acid addition by the second acid liquid dosing pump; flow meters are provided on the water inlet pipe and the water outlet pipe, and the dosing flow rate of the second acid liquid dosing pump is obtained according to a dosage-pH-PID algorithm with the pH target value of the water distribution regulating tank, the actual value after rough adjustment of the pH and the water inlet flow rate of the water distribution regulating tank as parameters;

[0008] Further, the drug dosage-pH-PID algorithm formula is:

[0009]

[0010] Among them, pH0 and pH1 are the actual value of the first pH meter and the target value set by the second pH meter, Q0 is the water flow rate of the water distribution and regulation tank, and a, b, c, d, and e are all constants;

[0011] Furthermore, the pipelines between the first acid solution dosing pump and the second acid solution dosing pump and the water distribution and regulating tank are both provided with flow meters;

[0012] Furthermore, the first acid solution dosing pump is a variable frequency pump or an industrial frequency pump, and the second acid solution dosing pump is a variable frequency pump.

[0013] The beneficial effects of the present invention are as follows: the precise acid adjustment system suitable for continuous flow sewage treatment of the present invention can realize precise addition of acid solution by combining rough adjustment and fine adjustment, avoiding the problems of excessive addition of acid solution and hysteresis, and adopts dosage-pH-PID algorithm to control the flow rate of sulfuric acid addition, so that the actual pH value fluctuates less, solves the problems of large fluctuation and hysteresis of PLC automatic acid control, and provides water quality guarantee for the stable operation of subsequent process sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0015] Figure 1 It is a structural schematic diagram of the present invention;

[0016] Figure 2 This is a diagram of the acid adjustment effect. DETAILED DESCRIPTION

[0017] The precise acid adjustment system for continuous flow sewage treatment of the present embodiment comprises a water distribution regulating tank 1 for receiving continuous flow sewage, an acid adding unit 2 and a control unit 3 for adding acid to the water distribution regulating tank 1. The acid adding unit 2 first adds acid to the water distribution regulating tank 1 in a quantitative manner for pH rough adjustment. The control unit 3 calculates the pH fine adjustment amount by using the dosage-pH-PID algorithm according to the pH target value and the actual value after pH rough adjustment, and controls the acid adding unit 2 to add acid to the water distribution regulating tank 1 for pH fine adjustment. Fenton oxidation technology is one of the most commonly used deep treatment technologies in the process of industrial wastewater treatment. Its principle is to use hydrogen peroxide in Fe under acidic conditions to 2+ Hydroxyl radicals are produced under the catalytic action of to remove organic pollutants in water. This reaction is very sensitive to pH. In order to ensure the treatment effect of the system, the wastewater to be treated generally needs to be pre-acidified to meet the requirements of the subsequent Fenton reaction. A sewage treatment plant needs to adjust its pH to the target value ±0.2 to achieve stable operation of the Fenton system. The water distribution regulating tank 1 is provided with an inlet pipe and an outlet pipe, and the inlet pipe is an overflow inlet. The water distribution regulating tank 1, the acid adding unit 2 and the control unit 3 are all connected and arranged. The first acid addition is rough adjustment. A certain amount of acid is manually added to the water distribution regulating tank 1 through the acid adding unit 2. Then, the second acid addition is calculated by the control unit 3 to obtain the acid addition amount, and a trace amount of acid is added to the water distribution regulating tank 1, which directly acts on the acid adding unit 2, and the acid addition amount is dynamically adjusted in real time to achieve the purpose of fine adjustment. By combining rough adjustment and fine adjustment, the accurate addition of acid can be achieved, avoiding the problem of excessive addition and hysteresis of acid. The added acid is a strong acid such as sulfuric acid and hydrochloric acid.

[0018] In this embodiment, the acid adding unit 2 includes a first acid liquid dosing pump 201 and a second acid liquid dosing pump 202 which are respectively connected to the pipeline of the water distribution regulating tank 1. The first acid liquid dosing pump 201 and the second acid liquid dosing pump 202 are both connected to the acid storage tank 4. The first acid liquid dosing pump 201 adds acid to the water distribution regulating tank 1 to control the pH within the set target value ±0.5, and the second acid liquid dosing pump 202 adds acid to the water distribution regulating tank 1 according to the dosing flow calculated by the dosage-pH-PID algorithm of the control unit 3; the first acid liquid dosing pump 201 and the second acid liquid dosing pump 202 are connected to the pipeline of the water distribution regulating tank 1, and the first acid liquid dosing pump 201 adds a certain amount of acid to the water distribution regulating tank 1 to achieve the purpose of rough adjustment. The second acid liquid dosing pump 202 adds acid to the water distribution regulating tank 1 according to the result of rough adjustment and the dosing flow calculated by the dosage-pH-PID algorithm of the control unit 3, so that the outlet water pH can be stabilized within the target set value ±0.25.

[0019] In this embodiment, the water distribution regulating tank 1 is provided with an inlet pipe, an outlet pipe, a first pH meter for detecting the actual pH after acid addition by the first acid liquid dosing pump 201, and a second pH meter for setting the pH target value by acid addition by the second acid liquid dosing pump 202; flow meters are provided on the inlet pipe and the outlet pipe, and the dosing flow of the second acid liquid dosing pump 202 is obtained according to the dosage-pH-PID algorithm with the pH target value of the water distribution regulating tank 1, the actual value after rough adjustment of the pH and the inlet flow of the water distribution regulating tank 1 as parameters; flow meters are provided on the inlet pipe and the outlet pipe to record the real-time water volume; when the water inlet pipe is designed to overflow water inlet or the water volume cannot be recorded, the flow rate can be calculated by adding an acid level meter to the water distribution regulating tank 1 and combining it with the flow meter of the outlet pipe to obtain the inlet flow. The first acid dosing pump 201 and the second acid dosing pump 202 are provided with flow meters in the strong acid pumping pipelines of the water distribution regulating tank 1, which can add strong acid quantitatively to improve accuracy. The regulating tank is provided with a stirring device to mix the strong acid and wastewater evenly.

[0020] In this embodiment, the drug dosage-pH-PID algorithm formula is:

[0021]

[0022] Among them, pH0 and pH1 are the actual value of the first pH meter and the target value set by the second pH meter respectively, Q0 is the inlet flow rate of the water distribution and regulating tank 1, a, b, c, d, e are all constants, and a, b, c, d are obtained according to the concentration of the acid.

[0023] In this embodiment, the pipelines between the first acid dosing pump 201, the second acid dosing pump 202 and the water distribution regulating tank 1 are both provided with flow meters; the first acid dosing pump 201 is a variable frequency pump or an industrial frequency pump, and the second acid dosing pump 202 is a variable frequency pump. The first acid dosing pump 201 is a variable frequency pump or an industrial frequency pump, which can be adjusted by constant flow or by feedback according to the first pH meter; the second acid dosing pump 202 is a variable frequency pump, which uses the dosage-pH-PID algorithm to add acid, dynamically adjusts the amount of acid added, and realizes accurate dosing of the agent. After the above adjustment, the pH water effect is as follows: Figure 2 The dosage-pH-PID algorithm formula used is: It can be seen that when the pH is adjusted manually or semi-automatically, the pH fluctuation range of the effluent is large (4.2-6.6), and the effluent pH can be stabilized within the range of ±0.25 of the target setting value, indicating that by treating the pH of the incoming water with this precise acid adjustment system, the pH control can be stabilized to ensure the effect of the subsequent Fenton reaction.

[0024] 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 precise acid adjustment system suitable for continuous flow sewage treatment, characterized by: The invention comprises a water distribution regulating tank for receiving continuous flow sewage, an acid adding unit and a control unit for adding acid to the water distribution regulating tank. Acid is first added to the water distribution regulating tank in a quantitative manner by the acid adding unit to perform a rough pH adjustment. The control unit calculates the pH fine adjustment amount by using a dosage-pH-PID algorithm according to the pH target value and the actual value after the rough pH adjustment, and controls the acid adding unit to add acid to the water distribution regulating tank for a fine pH adjustment.

2. The precise acid adjustment system for continuous flow sewage treatment according to claim 1 is characterized by: The acid adding unit includes a first acid dosing pump and a second acid dosing pump which are respectively connected to the water distribution regulating tank pipeline. The first acid dosing pump adds acid to the water distribution regulating tank to control the pH within the set target value ±0.5 range. The second acid dosing pump adds acid to the water distribution regulating tank according to the dosing flow calculated by the dosage-pH-PID algorithm of the control unit.

3. The precise acid adjustment system for continuous flow sewage treatment according to claim 2 is characterized in that: The water distribution regulating tank is provided with an inlet pipe, an outlet pipe, a first pH meter for detecting the actual pH after acid addition by the first acid liquid dosing pump, and a second pH meter for setting the pH target value by acid addition by the second acid liquid dosing pump; flow meters are provided on both the inlet pipe and the outlet pipe, and the dosing flow rate of the second acid liquid dosing pump is obtained according to a dosage-pH-PID algorithm with the pH target value of the water distribution regulating tank, the actual value after rough adjustment of the pH, and the water inlet flow rate of the water distribution regulating tank as parameters.

4. The precise acid adjustment system for continuous flow sewage treatment according to claim 3 is characterized by: The drug dosage-pH-PID algorithm formula is: Among them, pH0 and pH1 are the actual value of the first pH meter and the target value set by the second pH meter respectively, Q0 is the water inlet flow rate of the water distribution regulating tank, and a, b, c, d, and e are all constants.

5. The precise acid adjustment system for continuous flow sewage treatment according to claim 4, characterized in that: The pipelines between the first acid solution dosing pump and the second acid solution dosing pump and the water distribution and regulating tank are both provided with flow meters.

6. The precise acid adjustment system for continuous flow sewage treatment according to claim 2 is characterized in that: The first acid solution dosing pump is a variable frequency pump or an industrial frequency pump, and the second acid solution dosing pump is a variable frequency pump.

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