A reverse osmosis acidification device and a regulation control method

Abstract

This application relates to a reverse osmosis acid addition device and its regulation and control method, belonging to the field of reverse osmosis water treatment technology. To solve the problem of unreasonable acid addition points in the acid addition device, it includes a corrosion-resistant storage tank, a metering pump, a pulsation damper, a back pressure valve, a multi-stage static mixer, a security filter, an online water quality monitoring unit, and an intelligent control unit. The inlet of the metering pump is connected to the corrosion-resistant storage tank, and the outlet of the metering pump is connected sequentially to the pulsation damper and the back pressure valve, and then connected to the inlet pipe at the front end of the security filter, forming the acid addition point. This application ensures that the acid and the inlet water reach a fully uniform mixing state before entering the security filter, eliminating the defects of local over-acid corrosion of pipes and membrane elements caused by unreasonable acid addition points and insufficient mixing, as well as the defects of local high alkalinity still causing calcium carbonate scaling, thus ensuring the long-term stable operation of the reverse osmosis system and extending the service life of the membrane elements.

Description

Technical Field

[0001] This application relates to the field of reverse osmosis water treatment technology, and in particular to a reverse osmosis acid addition device and its regulation and control method. Background Technology

[0002] In reverse osmosis water treatment systems, calcium carbonate scaling is the main cause of decreased membrane element flux, increased operating pressure differential, and reduced desalination rate. Adding acid to the feed water to adjust the pH and alkalinity, thereby altering the carbonic acid balance system and reducing the Langerier saturation index, is a classic and effective method to inhibit calcium carbonate scaling.

[0003] However, existing acid addition devices generally suffer from unreasonable acid addition points. These points are often located in pipelines without adequate consideration of subsequent mixing conditions. The short contact time between the injected acid and the influent results in insufficient mixing, easily leading to localized over-acidity or excessively high alkalinity. Over-acidity accelerates corrosion of pipelines and membrane elements, causing irreversible damage, especially to stainless steel components and reverse osmosis membranes. Conversely, in areas of excessively high alkalinity, calcium carbonate remains supersaturated, failing to effectively eliminate the risk of scaling. This results in scaling still occurring on the surfaces of the security filter elements and membrane components, thus requiring improvement. Summary of the Invention

[0004] To address the problem of unreasonable acid addition points in acid addition devices, this application provides a reverse osmosis acid addition device and its regulation and control method.

[0005] The reverse osmosis acid addition device and its regulation and control method provided in this application adopt the following technical solution: A reverse osmosis acid addition device includes a corrosion-resistant storage tank, a metering pump, a pulsation damper, a back pressure valve, a multi-stage static mixer, a security filter, an online water quality monitoring unit, and an intelligent control unit; the inlet of the metering pump is connected to the corrosion-resistant storage tank, and the outlet of the metering pump is connected to the pulsation damper and the back pressure valve in sequence, and then connected to the inlet pipeline at the front end of the security filter, forming an acid addition point; The multi-stage static mixer is installed on the inlet pipe between the acid addition point and the security filter. The multi-stage static mixer has multiple spiral mixing units arranged inside along the fluid flow direction. The spiral mixing units of the multi-stage static mixer are used to perform multi-stage cutting, rotating and flipping mixing of acid and inlet water. The online water quality monitoring unit is located at the inlet pipeline upstream of the acid addition point and at the outlet of the multi-stage static mixer. The online water quality monitoring unit is used to collect inlet water parameters. The intelligent control unit is connected to the online water quality monitoring unit and the metering pump respectively, and is used to control the acid addition amount of the metering pump according to the collected inlet water parameters.

[0006] Because existing acid addition devices generally suffer from unreasonable acid addition point locations; the acid addition points are usually set in the pipeline without fully considering the subsequent mixing conditions, resulting in short contact time between the acid and the inlet water after injection and insufficient mixing, which easily leads to local over-acidity or local high alkalinity. By adopting the above technical solution, including a corrosion-resistant storage tank, a metering pump, a pulsation damper, a back pressure valve, a multi-stage static mixer, a security filter, a water quality online monitoring unit 18, and an intelligent control unit, the inlet of the metering pump is connected to the corrosion-resistant storage tank, and the outlet of the metering pump is connected to the pulsation damper and the back pressure valve in sequence, and then connected to the inlet water pipeline at the front end of the security filter. The connection point forms the acid addition point. The multi-stage static mixer is installed on the inlet water pipeline between the acid addition point and the security filter. The water quality online monitoring unit 18 is set at the inlet water pipeline upstream of the acid addition point and at the outlet of the multi-stage static mixer. The corrosion-resistant storage tank is used to store prepared dilute acid solutions. The metering pump draws acid from the storage tank and enters the pump chamber through the metering pump inlet valve and check valve on the inlet pipeline. The check valve prevents the acid from flowing back into the storage tank. After being pressurized by the metering pump, the acid flows sequentially through the metering pump outlet valve and the pulse damper inlet valve before entering the pulse damper. The pulse damper adopts a gasbag structure, utilizing the compressibility of gas to absorb the pulsating pressure wave at the metering pump outlet, converting the intermittent pulse flow into a stable continuous flow. The stable acid then passes through a back pressure valve to stabilize the outlet pressure, preventing siphon backflow caused by negative pressure in the pipeline. Finally, it flows through the acid dosing device to the reverse osmosis inlet water pipeline dosing valve and is injected into the acid dosing point of the inlet water pipeline. When the pipeline pressure rises abnormally, the pressure relief valve automatically opens, allowing part of the acid to flow back to the corrosion-resistant storage tank through the bypass pipeline, protecting the pipeline and equipment. The online water quality monitoring units are located upstream of the acidification point and at the outlet of the static mixer. The sensor upstream of the acidification point collects the initial water quality parameters of the raw water, including influent flow rate, pH value, temperature, calcium hardness, and total alkalinity, as the basis for feedforward control. The sensor at the outlet of the static mixer collects the actual pH value of the mixed water, as the basis for closed-loop feedback control. The pH sensor adopts a PTFE electrode sheath and a dual-liquid interface structure, which is resistant to acid corrosion and pollution. The hardness and alkalinity sensors are equipped with conical flow cells and automatic cleaning interfaces to ensure long-term stable operation in dilute acid environments. The signals from each sensor are isolated by a safety barrier before being uploaded to the intelligent control unit to prevent damage to the control card by on-site corrosion current or leakage signals. The intelligent control unit is the core control hub of the device. Its control principle is based on the real-time calculation and regulation of the Langerile Saturation Index (LSI). First, the intelligent control unit performs filtering, smoothing, and outlier removal preprocessing on the collected raw water flow rate, pH value, temperature, calcium hardness, and total alkalinity. It also performs temperature compensation based on the inlet water temperature to correct the calcium carbonate saturation pH value, eliminating deviations caused by temperature changes in the calcium carbonate dissolution equilibrium. Second, based on the corrected pH, calcium hardness, total alkalinity, and system recovery rate, it calculates the concentrated water LSI value online according to the built-in mathematical model: LSI = pH measurement (pHs); the final control objective is to stabilize the concentrate LSI value within the -0.2 to 0 range; then, a composite control strategy combining flow feedforward and pH closed-loop is adopted to output the acid addition command: feedforward adjustment uses the influent flow rate and total alkalinity as feedforward variables, calculates the theoretical acid addition amount using the carbonic acid balance relationship, and quickly outputs the basic acid addition command; when the influent flow rate changes, the operating frequency or stroke of the metering pump is adjusted in real time to make the acid addition amount change synchronously with the influent flow rate, so that more water means more acid and less water means less acid, eliminating the lag and overshoot caused by flow fluctuations; closed-loop fine-tuning uses the LSI target value as the control index, compares the real-time LSI value with the target value, generates a correction amount through the PID algorithm, and dynamically fine-tunes the basic acid addition amount to stabilize the concentrate LSI value within the set range; finally, the final acid addition command is converted into a 4-20mA analog signal or PWM signal and output to the metering pump to adjust its speed or stroke, so as to achieve precise and continuous adjustment of the acid addition amount. By optimizing the location of the acid addition point and incorporating a multi-stage static mixer, the acid addition point is positioned upstream of the security filter. A multi-stage static mixer is connected in series on the inlet pipe between the acid addition point and the security filter. This allows the acid to be injected along with the raw water and enter the mixer together. The continuous cutting, rotation, and tumbling action of the spiral mixing unit creates multi-stage forced mixing, ensuring that the acid and inlet water are fully and evenly mixed before entering the security filter. This eliminates the defects caused by improper acid addition point location and insufficient mixing, such as localized over-acid corrosion of pipes and membrane elements, and localized high alkalinity leading to calcium carbonate scaling. This ensures the long-term stable operation of the reverse osmosis system and extends the service life of the membrane elements.

[0007] Optionally, the bottom of the multi-stage static mixer is provided with a drain port, which is connected to a static mixer drain manual valve and a static mixer drain electric valve for draining residual acid; the multi-stage static mixer is installed with a slope of not less than 1% to prevent water accumulation.

[0008] By adopting the above technical solution, a drain port is set at the bottom of the multi-stage static mixer, which is connected to the static mixer drain manual valve and the static mixer drain electric valve. With the setting of the static mixer drain manual valve and the static mixer drain electric valve, when the system is shut down or under maintenance, the manual valve can be used to realize the on-site evacuation operation, and the electric valve can be used to realize the remote evacuation control, ensuring that the residual acid in the mixer is discharged in time. At the same time, the multi-stage static mixer is installed with a slope of not less than 1%, so that the residual liquid flows naturally to the drain port under the action of gravity, preventing water accumulation.

[0009] Optionally, the metering pump is equipped with a metering pump inlet valve and a check valve on its inlet pipe, and a metering pump outlet valve on its outlet pipe. A bypass pipe is led out from the metering pump outlet and the metering pump outlet valve and connected to the anti-corrosion storage tank. A pressure relief valve is installed on the bypass pipe. A pressure gauge and a pulse damper inlet valve are sequentially installed on the pipe between the metering pump outlet valve and the pulse damper.

[0010] By adopting the above technical solution, a metering pump inlet valve and a check valve are installed on the inlet pipe of the metering pump, and a metering pump outlet valve is installed on the outlet pipe of the metering pump. A bypass pipe is led out from the outlet pipe of the metering pump and the outlet pipe of the metering pump, and a pressure relief valve is installed on the bypass pipe. A pressure gauge and a pulse damper inlet valve are installed sequentially on the pipe between the metering pump outlet valve and the pulse damper. Through the installation of the metering pump inlet valve, check valve, metering pump outlet valve, pressure relief valve, pressure gauge, and pulse damper inlet valve, the metering pump inlet valve facilitates the disconnection of the inlet pipe during metering pump maintenance; the check valve prevents acid from flowing back from the pump chamber to the anti-corrosion storage tank; the metering pump outlet valve facilitates the adjustment and disconnection of the outlet flow; when the pipeline pressure rises abnormally, the pressure relief valve automatically opens to return part of the acid to the anti-corrosion storage tank, protecting the pipeline and equipment safety; the pressure gauge displays the pressure of the acid adding pipeline in real time, facilitating operators to monitor the operating status; and the pulse damper inlet valve facilitates the isolation and maintenance of the pulse damper.

[0011] Optionally, the top of the anti-corrosion storage tank is equipped with a stirrer, which is a paddle stirrer; the bottom of the anti-corrosion storage tank is equipped with a drain valve; and the upper part of the anti-corrosion storage tank is also connected to an acid mist absorber.

[0012] By adopting the above technical solution, an agitator is installed at the top of the anti-corrosion storage tank, a drain valve is installed at the bottom of the anti-corrosion storage tank, and an acid mist absorber is connected to the upper part of the anti-corrosion storage tank. Through the agitator, drain valve, and acid mist absorber, the dilute acid solution prepared in the storage tank is continuously stirred to ensure uniform acid concentration and avoid deviation in acid addition due to concentration stratification. The drain valve facilitates the periodic emptying of sediment and impurities at the bottom of the tank to keep the acid clean. The acid mist absorber absorbs and treats the acid mist generated during acid preparation and operation to prevent acid mist from escaping and corroding surrounding equipment and to ensure personnel safety.

[0013] Optionally, the corrosion-resistant storage tank is equipped with a liquid level sensor, which is connected to an intelligent control unit and used to interlock and stop the metering pump when the liquid level is low. The corrosion-resistant storage tank is connected to a water replenishment pipeline for introducing RO permeate for replenishment, and the water replenishment pipeline is equipped with a manual inlet valve and an electric inlet valve for the storage tank. The corrosion-resistant storage tank is also connected to an acid replenishment pipeline for introducing concentrated hydrochloric acid for replenishment, and the acid replenishment pipeline is equipped with a manual inlet valve and an electric inlet PPR valve for the storage tank. The corrosion-resistant storage tank is also equipped with an online hydrochloric acid concentration monitoring instrument, which is connected to the intelligent control unit and used for feedback control of the opening and closing of the acid inlet valve.

[0014] By adopting the above technical solution, a liquid level sensor is installed inside the anti-corrosion storage tank. The water supply pipeline of the anti-corrosion storage tank is equipped with a manual inlet valve and an electric inlet valve. The acid supply pipeline of the anti-corrosion storage tank is equipped with a manual inlet valve and an electric PPR valve. The anti-corrosion storage tank is also equipped with an online hydrochloric acid concentration monitoring instrument. Through the installation of the liquid level sensor, the manual inlet valve, the electric inlet valve, the manual inlet valve, the electric PPR valve, and the online hydrochloric acid concentration monitoring instrument, the liquid level sensor is integrated with the intelligent control unit. The system features a multi-connection mechanism that interlocks to stop the metering pump when the liquid level falls below the set lower limit to prevent damage from dry running. The manual and electric valves for the chemical storage tank inlet enable manual and automatic control of RO permeate water replenishment. Similarly, the manual and electric PPR valves for the concentrated hydrochloric acid inlet enable manual and automatic control of concentrated hydrochloric acid replenishment. An online hydrochloric acid concentration monitoring instrument provides real-time feedback of the acid concentration signal. The intelligent control unit automatically controls the opening and closing of the electric acid inlet valve based on the concentration signal, achieving precise closed-loop regulation of the acid concentration and ensuring that the acid concentration in the chemical storage tank remains within the set range.

[0015] Optionally, an acid addition device is provided at the acid addition point to the dosing valve of the reverse osmosis feed water pipeline; a security filter inlet valve is provided on the pipeline between the outlet of the multi-stage static mixer and the inlet of the security filter.

[0016] By adopting the above technical solution, an acid addition device is installed at the acid addition point, leading to a dosing valve on the reverse osmosis feed water pipeline. A security filter inlet valve is installed on the pipeline between the outlet of the multi-stage static mixer and the inlet of the security filter. The installation of the acid addition device dosing valve and the security filter inlet valve at the acid addition point facilitates the on / off control of the connection between the acid addition pipeline and the main feed water pipeline. The acid injection can be cut off when the acid addition system is under maintenance or shut down. The security filter inlet valve facilitates the control of the water flow into the security filter. When replacing filter elements or maintaining the security filter, it is not necessary to shut down the upstream pipeline, thus achieving isolation.

[0017] Optionally, the online water quality monitoring unit includes a flow sensor, a pH sensor, a temperature sensor, a hardness sensor, and an alkalinity sensor; the pH sensor adopts a dual-liquid interface structure; the hardness sensor and the alkalinity sensor are equipped with a conical flow tank and an automatic cleaning interface; a safety barrier is provided between the online water quality monitoring unit and the intelligent control unit.

[0018] By adopting the above technical solution, the online water quality monitoring unit includes a flow sensor, a pH sensor, a temperature sensor, a hardness sensor, and an alkalinity sensor. Through the setting of the online water quality monitoring unit, multiple parameters such as influent flow rate, pH, temperature, calcium hardness, and total alkalinity can be collected synchronously and in real time, providing a complete water quality data foundation for the intelligent control unit.

[0019] Optionally, the pump head of the metering pump is a hydraulic diaphragm pump; the pulsation damper is a pneumatic pulsation damper; and the back pressure valve is an anti-siphon check valve.

[0020] By adopting the above technical solution, the metering pump head is a hydraulic diaphragm pump, the pulsation damper is a pneumatic pulsation damper, and the back pressure valve is an anti-siphon check valve. Through the setting of the metering pump, pulsation damper, and back pressure valve models, the metering pump uses a hydraulic diaphragm pump, utilizing hydraulic oil to uniformly drive the diaphragm, adapting to long-term dilute hydrochloric acid transport conditions. The pulsation damper uses a pneumatic pulsation damper, utilizing the compressibility of the gas inside the pneumatic bladder to effectively absorb the pulsating pressure wave at the metering pump outlet, converting the pulsed flow into a stable continuous flow, avoiding uneven mixing and localized over-acid corrosion caused by flow fluctuations. The back pressure valve uses an anti-siphon check valve, which, while stabilizing the back pressure at the metering pump outlet, structurally prevents siphon backflow when the pipeline is under negative pressure, avoiding water in the inlet pipeline flowing back into the acid pipeline and causing concentration changes.

[0021] Optionally, the intelligent control unit has a built-in Langerier saturation index calculation model, with the control target being to keep the concentrated water Langerier saturation index value stable at -0.2-0, and outputs the acid addition command by using a flow feedforward combined with pH closed-loop regulation; the intelligent control unit has a temperature compensation function, which corrects the calcium carbonate saturation pH value in real time according to the inlet water temperature.

[0022] By adopting the above technical solution, the intelligent control unit incorporates a Langerier saturation index calculation model, aiming to stabilize the concentrated water Langerier saturation index value between -0.2 and 0. Through the intelligent control unit's design, it ensures maximum suppression of calcium carbonate scaling without posing a corrosion risk. It outputs acid addition commands using a flow feedforward combined with pH closed-loop adjustment. The feedforward adjustment ensures rapid response during large flow fluctuations, while the closed-loop fine-tuning ensures control accuracy during steady-state operation, preventing scaling due to insufficient acid addition or corrosion due to excessive acid addition. It also features temperature compensation, real-time correction of the calcium carbonate saturation pH value based on the inlet water temperature, eliminating the impact of temperature changes on the calcium carbonate dissolution balance, and ensuring accurate acid addition at low temperatures and adequate acid addition at high temperatures.

[0023] Optionally, a method for regulating and controlling a reverse osmosis acid addition device includes the following steps: S1. Start the metering pump to draw acid from the anti-corrosion storage tank. After the flow pulsation is eliminated by the pulsation damper and the outlet pressure is stabilized by the back pressure valve, the acid is smoothly added to the inlet pipe at the front end of the security filter. After the acid and raw water are initially mixed, they enter the multi-stage static mixer. The fluid is cut, rotated and turned multiple times by multiple spiral mixing units to achieve uniform mixing of acid and raw water and avoid local over-acidity or local high alkalinity. S2. The water quality online monitoring unit, located upstream of the acid addition point and at the outlet of the static mixer, collects parameters such as influent flow rate, pH value, temperature, calcium hardness, and total alkalinity in real time, and obtains the reverse osmosis system recovery rate through the intelligent control unit; the intelligent control unit performs filtering, smoothing, and outlier removal preprocessing on the collected parameters. S3, the intelligent control unit performs temperature compensation based on the inlet water temperature, corrects the calcium carbonate saturation pH value in real time, and calculates the concentrated water Langerier saturation index value online in combination with calcium hardness, total alkalinity and system recovery rate; at the same time, it corrects the calculated acid addition amount based on the concentration signal fed back by the hydrochloric acid concentration monitoring instrument. S4. Using the influent flow rate and total alkalinity as feedforward variables, the theoretical acid addition amount is calculated using the carbonic acid balance relationship, and the basic acid addition amount command is output. When the influent flow rate changes, the feedforward regulation adjusts the operating frequency or stroke of the metering pump in real time so that the acid addition amount changes synchronously with the influent flow rate. S5. Using the Langerilla saturation index target value of -0.2-0 as the control index, the real-time concentrated Langerilla saturation index value is compared with the target value. A correction amount is generated through the PID algorithm to perform closed-loop fine-tuning of the basic acid addition amount. The corrected acid addition amount command is converted into a 4-20mA analog signal or PWM signal and output to the metering pump. The speed or stroke of the metering pump is adjusted in real time to stabilize the concentrated Langerilla saturation index value within the set range.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. By setting up a reasonable acid addition point and a multi-stage static mixer, the acid addition point is located at the front end of the security filter, and a multi-stage static mixer is connected in series on the inlet pipe between the acid addition point and the security filter. This allows the acid to enter the mixer together with the raw water after injection. Through the continuous cutting, rotation and tumbling action of the spiral mixing unit, multi-stage forced mixing is formed, ensuring that the acid and the feed water reach a fully uniform mixing state before entering the security filter. This eliminates the defects caused by unreasonable acid addition point location and insufficient mixing, such as local over-acid corrosion of pipes and membrane elements, as well as the defects caused by local high alkalinity that still produce calcium carbonate scaling. This ensures the long-term stable operation of the reverse osmosis system and extends the service life of the membrane elements. 2. By setting up an online water quality monitoring unit, multiple parameters such as influent flow rate, pH, temperature, calcium hardness, and total alkalinity can be collected synchronously and in real time, providing a complete water quality data foundation for the intelligent control unit; 3. Through the setting of the intelligent control unit, the scale formation of calcium carbonate is suppressed to the maximum extent without causing corrosion risk. The acid addition command is output by using a flow feedforward combined with pH closed-loop regulation. The feedforward regulation ensures a fast response when the flow rate fluctuates greatly, and the closed-loop fine adjustment ensures the control accuracy during steady-state operation. This avoids scale formation due to insufficient acid addition or corrosion due to excessive acid addition. At the same time, it has a temperature compensation function, which corrects the saturated pH value of calcium carbonate in real time according to the inlet water temperature, eliminates the influence of temperature changes on the calcium carbonate dissolution balance, and ensures that acid addition is not incorrect at low temperatures and not insufficient at high temperatures. Attached Figure Description

[0025] Figure 1 This is a flow chart of the water treatment system used in the reverse osmosis acid addition device in the embodiments of this application.

[0026] Figure 2 This is a schematic diagram of a reverse osmosis acid addition device in an embodiment of this application.

[0027] Explanation of reference numerals in the attached diagram: 1. Corrosion-resistant storage tank; 2. Liquid level sensor; 3. Metering pump; 4. Pulse damper; 5. Pressure relief valve; 6. Back pressure valve; 7. Pressure gauge; 8. Metering pump inlet valve; 9. Check valve; 10. Metering pump outlet valve; 11. Pulse damper inlet valve; 12. Manual inlet valve for storage tank; 13. Agitator; 14. Drain valve; 15. Static mixer; 16. Inlet valve for security filter; 17. Security filter; 18. Online water quality monitoring unit; 19. Manual drain valve for static mixer; 20. Electric drain valve for static mixer; 21. Dosing valve for acid addition device to reverse osmosis feed water pipeline; 22. Electric inlet valve for storage tank; 23. Electric PPR valve for acid inlet of storage tank; 24. Manual inlet valve for acid in storage tank; 25. Acid mist absorber; 26. Online hydrochloric acid concentration monitoring instrument. Detailed Implementation

[0028] To illustrate in detail the technical solutions adopted by the present invention to achieve the intended technical objectives, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Furthermore, the technical means or technical features in the embodiments of the present invention can be replaced without creative effort. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0029] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0030] This application discloses a reverse osmosis acid addition device. (Refer to...) Figure 1 and Figure 2 The reverse osmosis acid addition device includes a corrosion-resistant storage tank 1, a metering pump 3, a pulsation damper 4, a back pressure valve 6, a multi-stage static mixer 15, a security filter 17, an online water quality monitoring unit 18, and an intelligent control unit. The corrosion-resistant storage tank 1 is used to store the prepared dilute acid solution. The inlet of the metering pump 3 is connected to the corrosion-resistant storage tank 1. The outlet of the metering pump 3 is connected in sequence to the pulsation damper 4 and the back pressure valve 6, and then connected to the inlet pipe at the front end of the security filter 17. The connection point forms the acid addition point.

[0031] Reference Figure 1 and Figure 2 The top of the corrosion-resistant storage tank 1 is equipped with a stirrer 13. In this embodiment, the stirrer 13 is a paddle stirrer, which can be a two-blade straight paddle or a three-blade folding paddle. The paddle material is PP, fiberglass FRP, or PTFE-lined. The stirring shaft is made of carbon steel lined with plastic or stainless steel lined with PTFE. The rotation speed is 60-100 rpm, and it is installed vertically from the top. The corrosion-resistant storage tank 1 is made of PE plastic, which is resistant to 30% concentrated hydrochloric acid and 5% dilute hydrochloric acid. The volume is configured according to the hourly flow rate of the metering pump 3 × 8-12 hours. A drain valve 14 is installed at the bottom of the corrosion-resistant storage tank 1. The drain valve 14 is made of PVC. The ball valve and the upper part of the corrosion-resistant storage tank 1 are also connected to an acid mist absorber 25; the corrosion-resistant storage tank 1 is equipped with a lockable overflow port and an acid-resistant exhaust port, and the inlet pipeline is equipped with a PVC filter and a PVC flange union; the stirrer 13 continuously stirs the dilute acid solution prepared in the storage tank to ensure uniform acid concentration and avoid deviation in acid addition due to concentration stratification; the drain valve 14 facilitates the periodic emptying of sediment and impurities at the bottom of the tank to keep the acid clean; the acid mist absorber 25 absorbs and treats the acid mist generated during acid preparation and operation to prevent acid mist from escaping and corroding surrounding equipment and to ensure personnel safety.

[0032] Reference Figure 1 and Figure 2The corrosion-resistant chemical storage tank 1 is equipped with a liquid level sensor 2, which is connected to the intelligent control unit and is used to interlock and stop the metering pump 3 when the liquid level is low. The corrosion-resistant chemical storage tank 1 is connected to a water supply pipeline for introducing RO permeate, and the water supply pipeline is equipped with a manual inlet valve 12 and an electric inlet valve 22. Simultaneously, the corrosion-resistant chemical storage tank 1 is also connected to an acid supply pipeline for introducing concentrated hydrochloric acid, and the acid supply pipeline is equipped with a manual inlet valve 24 and an electric inlet PPR valve 23. The corrosion-resistant chemical storage tank 1 is also equipped with an online hydrochloric acid concentration monitoring instrument 26, which is connected to the intelligent control unit for... The system controls the opening and closing of the acid inlet valve; the level sensor 2 is connected to the intelligent control unit, and interlocks to stop the metering pump 3 when the level is lower than the set lower limit to prevent the pump from running dry and being damaged; the manual valve 12 and the electric valve 22 for the chemical storage tank inlet enable manual and automatic control of RO permeate water replenishment; the manual valve 24 and the electric PPR valve 23 for the chemical storage tank inlet enable manual and automatic control of concentrated hydrochloric acid replenishment; the online hydrochloric acid concentration monitoring instrument 26 provides real-time feedback of acid concentration signals; and the intelligent control unit automatically controls the opening and closing of the electric valve for the acid inlet based on the concentration signals to achieve precise closed-loop adjustment of the acid concentration and ensure that the acid concentration in the chemical storage tank is maintained within the set range.

[0033] Reference Figure 1 and Figure 2 The pump head of metering pump 3 is a hydraulic diaphragm pump. In this embodiment, the pump head material can be PVDF, which is acid-resistant, has stable output pressure, and high metering accuracy. A metering pump inlet valve 8 and a check valve 9 are installed on the inlet pipe of metering pump 3, and a metering pump outlet valve 10 is installed on the outlet pipe of metering pump 3. At the same time, a bypass pipe is led out from the pipe between the outlet of metering pump 3 and the metering pump outlet valve 10 and connected to the anti-corrosion storage tank 1. A pressure relief valve 5 is installed on this bypass pipe. A series of valves are installed on the pipe between the metering pump outlet valve 10 and the pulsation damper 4. The system is equipped with a pressure gauge 7 and a pulse damper inlet valve 11; a metering pump inlet valve 8 facilitates the disconnection of the inlet pipeline during metering pump 3 maintenance; a check valve 9 prevents acid from flowing back from the pump chamber to the anti-corrosion storage tank 1; a metering pump outlet valve 10 facilitates the adjustment and disconnection of the outlet flow; when the pipeline pressure rises abnormally, the pressure relief valve 5 automatically opens to return part of the acid to the anti-corrosion storage tank 1, protecting the pipeline and equipment; the pressure gauge 7 displays the pressure of the acid adding pipeline in real time, facilitating operators to monitor the operating status; and the pulse damper inlet valve 11 facilitates the isolation and maintenance of the pulsation damper 4.

[0034] Reference Figure 1 and Figure 2The pulsation damper 4 is an air-bag type pulsation damper, and the back pressure valve 6 is an anti-siphon check valve. The entire pipeline is made of UPVC, PPR, or PTFE-lined steel pipe, and the valves are pneumatic diaphragm valves or rubber-lined ball valves. The multi-stage static mixer 15 is installed on the inlet pipeline between the acid addition point and the security filter 17. The multi-stage static mixer 15 has multiple spiral mixing units arranged inside along the fluid flow direction. The multi-stage static mixer 15 is of type SK and is made of UPVC, PP, CPVC, or PE. The mixing units are equipped with reinforcing ribs or thickened pipe walls. The spiral mixing units of the multi-stage static mixer 15 are used to perform multi-stage cutting, rotation, and tumbling mixing of acid and inlet water. The mixing residence time is not less than 10 seconds, and the mixing uniformity is not less than 98%.

[0035] Reference Figure 1 and Figure 2 The bottom of the multi-stage static mixer 15 is formed with a drain port, which is connected to a static mixer drain manual valve 19 and a static mixer drain electric valve 20 for draining residual acid. The multi-stage static mixer 15 is installed with a slope of not less than 1% to prevent water accumulation. When the system is shut down or under maintenance, the manual valve can be used for on-site venting, or the electric valve can be used for remote venting control to ensure that the residual acid in the mixer is discharged in time. At the same time, the multi-stage static mixer 15 is installed with a slope of not less than 1% so that the residual liquid flows naturally to the drain port under the action of gravity to prevent water accumulation.

[0036] Reference Figure 1 and Figure 2 An acid-adding device is installed at the acid-adding point, leading to a dosing valve 21 in the reverse osmosis feed water pipeline; a security filter inlet valve 16 is installed on the pipeline between the outlet of the multi-stage static mixer 15 and the inlet of the security filter 17; the acid-adding device at the acid-adding point, leading to a dosing valve 21 in the reverse osmosis feed water pipeline, facilitates the on / off control of the connection between the acid-adding pipeline and the main feed water pipeline, and can cut off the acid injection when the acid-adding system is under maintenance or shut down; the security filter inlet valve 16 facilitates the control of the water flow into the security filter 17, and does not require shutting down the front-end pipeline when replacing filter elements or maintaining the security filter 17, thus achieving isolation.

[0037] Reference Figure 1 and Figure 2 The online water quality monitoring unit 18 is located at the inlet pipe upstream of the acid addition point and at the outlet of the multi-stage static mixer 15. The online water quality monitoring unit 18 is used to collect inlet water parameters. The intelligent control unit is connected to the online water quality monitoring unit 18 and the metering pump 3 respectively, and is used to control the amount of acid added by the metering pump 3 according to the collected inlet water parameters.

[0038] Reference Figure 1 and Figure 2The online water quality monitoring unit 18 includes a flow sensor, a pH sensor, a temperature sensor, a hardness sensor, and an alkalinity sensor. The electrode sheath of the pH sensor is made of PTFE material, and the pH sensor adopts a double-liquid interface structure with the outer cavity filled with a saturated KCl solution. The housings of the temperature sensor and the flow sensor are made of PTFE-lined material or integrally injection molded, and the junction box is explosion-proof and corrosion-resistant. The hardness sensor and the alkalinity sensor are equipped with a conical flow cell and an automatic cleaning interface, and adopt corrosion-resistant optical or ultrasonic detection principles. A safety barrier is set between the online water quality monitoring unit 18 and the intelligent control unit for signal isolation. The sensor installation point of the online water quality monitoring unit 18 is higher than the highest water level, or a vacuum breaking interface is set to prevent dilute acid from being drawn back into the sensor due to negative pressure and causing damage. It realizes the synchronous real-time acquisition of multiple parameters such as influent flow rate, pH, temperature, calcium hardness, and total alkalinity, providing a complete water quality data foundation for the intelligent control unit.

[0039] Reference Figure 1 and Figure 2The intelligent control unit incorporates a Langerier saturation index calculation model, aiming to stabilize the concentrated water Langerier saturation index value between -0.2 and 0. It outputs acid addition commands using a flow feedforward combined with pH closed-loop regulation. The intelligent control unit features temperature compensation, with a built-in temperature compensation coefficient correction table. It corrects the calcium carbonate saturation pH value in real time based on the influent temperature; for every 1°C increase in temperature, pH decreases by approximately 0.01, and the intelligent control unit automatically completes calibration. The intelligent control unit receives signals from the online water quality monitoring unit 18 in real time and performs filtering, smoothing, range conversion, and outlier removal preprocessing. It corrects the calcium carbonate saturation pH value (pHs) based on the influent temperature and combines it with calcium hardness, total alkalinity, and system recovery rate according to the formula LSI = pH measurement – ​​pHs, online calculation of concentrate LSI value; based on feedforward regulation, it quickly responds to flow changes, and uses PID closed-loop fine-tuning to achieve precise LSI approaching the target range. Finally, the acid addition command is converted into a 4-20mA analog signal or PWM signal output to metering pump 3 to adjust its speed or stroke; ensuring that calcium carbonate scaling is suppressed to the maximum extent without causing corrosion risk. Feedforward regulation ensures rapid response during large flow fluctuations, and closed-loop fine-tuning ensures control accuracy during steady-state operation, avoiding scaling due to insufficient acid addition or corrosion due to excessive acid addition. It also has a temperature compensation function, correcting the calcium carbonate saturation pH value in real time according to the inlet water temperature, eliminating the impact of temperature changes on the carbonate dissolution balance, and ensuring that acid addition is not incorrect at low temperatures and not insufficient at high temperatures. The intelligent control unit also communicates and links with the scale inhibitor dosing system, coordinating the adjustment of the scale inhibitor dosage based on the real-time operating pH value. When the pH is too low, it automatically slightly increases the scale inhibitor dosage to prevent hydrolysis and ineffectiveness. When the pH is moderate, it reduces the dosage to save on reagents. The intelligent control unit is equipped with a multi-level safety protection mechanism, including pH high and low limit alarms and protection, LSI index over-limit alarm, metering pump 3 fault protection, low liquid level interlock protection, and over-acid protection. When the pH value is lower than the set lower limit or drops sharply, metering pump 3 is forcibly shut down and an alarm is output. When the concentrate LSI index exceeds the target range of -0.2 to 0, a warning is triggered, indicating abnormal water quality or adjustment deviation. When metering pump 3 fails and stops, the standby pump is automatically put into operation to ensure continuous acid addition.

[0040] Reference Figure 1 and Figure 2This device should be installed indoors or in a rain-sheltered location, with acid-resistant dikes and anti-corrosion flooring, away from electrical cabinets, bearings, and stainless steel equipment. The acid dosing room should be equipped with a forced ventilation system, ensuring at least 12 air changes per hour to prevent acid mist accumulation and potential safety accidents. The intelligent control unit uses an independent local control cabinet. The control cabinet is an outdoor stainless steel cabinet with an IP55 or higher protection rating, measuring 600mm × 800mm × 250mm. The built-in PLC controller is a Siemens S7-200SMART or Mitsubishi FX3U series, equipped with a 7-inch or 10-inch touchscreen. The control cabinet can be set on-site to set LSI target values, modify PID parameters, view real-time trend curves and alarm history; the signal cable uses KVVP2 shielded cable, and the control cabinet is reliably grounded and separated from the equipment grounding to avoid ground loop interference with analog quantities; it can also be connected to the plant-level DCS system, such as Emerson, Zhejiang University Control System, and Hollysys, in remote IO mode according to on-site needs, and the control logic is implemented in the DCS controller. The flowchart includes a flow feedforward module, LSI index calculation module, PID adjustment module and metering pump 3 output module to achieve centralized monitoring.

[0041] The implementation principle of a reverse osmosis acid addition device according to an embodiment of this application is as follows: A corrosion-resistant storage tank 1 is used to store the prepared dilute acid solution. A metering pump 3 draws acid from the storage tank and enters the pump chamber through the metering pump inlet valve 8 and check valve 9 on the inlet pipeline. The check valve 9 prevents the acid from flowing back into the storage tank. After being pressurized by the metering pump 3, the acid flows sequentially through the metering pump outlet valve 10 and the pulse damper inlet valve 11, entering the pulsation damper 4. The pulsation damper 4 adopts a gasbag structure, utilizing the compressibility of gas to absorb the pulsating pressure wave at the outlet of the metering pump 3, converting the intermittent pulse flow into a stable continuous flow. The stable acid then passes through the back pressure valve 6 to stabilize the outlet pressure, preventing siphon backflow caused by negative pressure in the pipeline. Finally, it flows through the acid addition device to the dosing valve of the reverse osmosis inlet pipeline and is injected into the acid addition point of the inlet pipeline. When the pipeline pressure rises abnormally, the pressure relief valve 5 automatically opens, allowing part of the acid to flow back to the corrosion-resistant storage tank 1 through the bypass pipeline, protecting the pipeline and equipment. The online water quality monitoring unit 18 is installed upstream of the acid addition point and at the outlet of the static mixer 15. The sensor upstream of the acid addition point is used to collect the initial water quality parameters of the raw water, including influent flow rate, pH value, temperature, calcium hardness, and total alkalinity, as the basis for feedforward control. The sensor at the outlet of the static mixer 15 is used to collect the actual pH value of the mixed water, as the basis for closed-loop feedback control. The pH sensor adopts a PTFE electrode sheath and a dual-liquid interface structure, which is resistant to acid corrosion and pollution. The hardness and alkalinity sensors are equipped with a conical flow tank and an automatic cleaning interface to ensure long-term stable operation in a dilute acid environment. The signals from each sensor are isolated by a safety barrier and then uploaded to the intelligent control unit to prevent on-site corrosion current or leakage signals from damaging the control card. The intelligent control unit is the core control hub of the device. Its control principle is based on the real-time calculation and regulation of the Langerile Saturation Index (LSI). First, the intelligent control unit performs filtering, smoothing, and outlier removal preprocessing on the collected raw water flow rate, pH value, temperature, calcium hardness, and total alkalinity. It also performs temperature compensation based on the inlet water temperature to correct the calcium carbonate saturation pH value, eliminating deviations caused by temperature changes in the calcium carbonate dissolution equilibrium. Second, based on the corrected pH, calcium hardness, total alkalinity, and system recovery rate, it calculates the concentrated water LSI value online according to the built-in mathematical model: LSI = pH measurement (pHs); the final control objective is to stabilize the concentrate LSI value within the -0.2 to 0 range; then, a composite control strategy combining flow feedforward and pH closed-loop is adopted to output the acid addition command: feedforward adjustment uses the influent flow rate and total alkalinity as feedforward variables, calculates the theoretical acid addition amount using the carbonic acid balance relationship, and quickly outputs the basic acid addition command; when the influent flow rate changes, the operating frequency or stroke of metering pump 3 is adjusted in real time to make the acid addition amount change synchronously with the influent flow rate, so that more water means more acid and less water means less acid, eliminating the lag and overshoot caused by flow fluctuations; closed-loop fine adjustment uses the LSI target value as the control index, compares the real-time LSI value with the target value, generates a correction amount through the PID algorithm, and dynamically fine-tunes the basic acid addition amount to stabilize the concentrate LSI value within the set range; finally, the final acid addition command is converted into a 4-20mA analog signal or PWM signal and output to metering pump 3 to adjust its speed or stroke, so as to achieve precise and continuous adjustment of the acid addition amount. By setting the acid addition point at a reasonable location and using a multi-stage static mixer 15, the acid addition point is placed at the front end of the security filter 17. A multi-stage static mixer 15 is connected in series on the inlet pipe between the acid addition point and the security filter 17. This allows the acid to enter the mixer together with the raw water after injection. Through the continuous cutting, rotation, and tumbling action of the spiral mixing unit, multi-stage forced mixing is formed, ensuring that the acid and the inlet water reach a fully uniform mixing state before entering the security filter 17. This eliminates the defects caused by unreasonable acid addition point location and insufficient mixing, such as local over-acid corrosion of pipes and membrane elements, and local high alkalinity still causing calcium carbonate scaling. This ensures the long-term stable operation of the reverse osmosis system and extends the service life of the membrane elements.

[0042] A method for regulating and controlling a reverse osmosis acid addition device includes the following steps: S1. Start metering pump 3 to draw acid from anti-corrosion storage tank 1. After the flow pulsation is eliminated by pulsation damper 4 and the outlet pressure is stabilized by back pressure valve 6, it is smoothly added to the inlet pipe at the front end of security filter 17. After the acid and raw water are initially mixed, they enter multi-stage static mixer 15. Through multiple spiral mixing units, the fluid is cut, rotated and turned multiple times to achieve uniform mixing of acid and raw water and avoid local over-acidity or local high alkalinity. S2. The water quality online monitoring unit 18, located upstream of the acid addition point and at the outlet of the static mixer 15, collects parameters such as influent flow rate, pH value, temperature, calcium hardness, and total alkalinity in real time, and obtains the reverse osmosis system recovery rate through the intelligent control unit; the intelligent control unit performs filtering, smoothing, and outlier removal preprocessing on the collected parameters. S3, the intelligent control unit performs temperature compensation based on the inlet water temperature, corrects the calcium carbonate saturation pH value in real time, and calculates the concentrated water Langerier saturation index value online in combination with calcium hardness, total alkalinity and system recovery rate; at the same time, it corrects the calculated acid addition amount based on the concentration signal fed back by the hydrochloric acid concentration online monitoring instrument 26. S4. Using the influent flow rate and total alkalinity as feedforward variables, the theoretical acid addition amount is calculated using the carbonic acid balance relationship, and the basic acid addition amount command is output. When the influent flow rate changes, the feedforward regulation adjusts the working frequency or stroke of the metering pump 3 in real time so that the acid addition amount changes synchronously with the influent flow rate. S5. Using the target value of the Langerilla saturation index (-0.2-0) as the control index, the real-time concentrated Langerilla saturation index value is compared with the target value. A correction amount is generated through the PID algorithm to fine-tune the basic acid addition amount in a closed loop. The corrected acid addition amount command is converted into a 4-20mA analog signal or a PWM signal and output to the metering pump 3. The speed or stroke of the metering pump 3 is adjusted in real time to stabilize the concentrated Langerilla saturation index value within the set range.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A reverse osmosis acid addition device, characterized in that: It includes an anti-corrosion storage tank, a metering pump, a pulsation damper, a back pressure valve, a multi-stage static mixer, a security filter, an online water quality monitoring unit, and an intelligent control unit; the inlet of the metering pump is connected to the anti-corrosion storage tank, and the outlet of the metering pump is connected to the pulsation damper and the back pressure valve in sequence, and then connected to the water inlet pipe at the front end of the security filter, forming an acid addition point. The multi-stage static mixer is installed on the inlet pipe between the acid addition point and the security filter. The multi-stage static mixer has multiple spiral mixing units arranged inside along the fluid flow direction. The spiral mixing units of the multi-stage static mixer are used to perform multi-stage cutting, rotating and flipping mixing of acid and inlet water. The online water quality monitoring unit is located at the inlet pipeline upstream of the acid addition point and at the outlet of the multi-stage static mixer. The online water quality monitoring unit is used to collect inlet water parameters. The intelligent control unit is connected to the online water quality monitoring unit and the metering pump respectively, and is used to control the acid addition amount of the metering pump according to the collected inlet water parameters.

2. The reverse osmosis acid addition device according to claim 1, characterized in that: The bottom of the multi-stage static mixer is provided with a drain port, which is connected to a static mixer drain manual valve and a static mixer drain electric valve for draining residual acid; the multi-stage static mixer is installed with a slope of not less than 1% to prevent water accumulation.

3. The reverse osmosis acid addition device according to claim 1, characterized in that: The metering pump is equipped with a metering pump inlet valve and a check valve on its inlet pipe, and a metering pump outlet valve on its outlet pipe. A bypass pipe is led out from the metering pump outlet and the metering pump outlet valve to the anti-corrosion storage tank. A pressure relief valve is installed on the bypass pipe. A pressure gauge and a pulse damper inlet valve are installed in sequence on the pipe between the metering pump outlet valve and the pulse damper.

4. The reverse osmosis acid addition device according to claim 1, characterized in that: The anti-corrosion storage tank is equipped with a stirrer at the top, which is a paddle stirrer. The bottom of the anti-corrosion storage tank is equipped with a drain valve, and the upper part of the anti-corrosion storage tank is also connected to an acid mist absorber.

5. A reverse osmosis acid addition device according to claim 4, characterized in that: The corrosion-resistant chemical storage tank is equipped with a liquid level sensor, which is connected to an intelligent control unit to interlock and stop the metering pump when the liquid level is low. The tank is also connected to a water supply line for introducing RO permeate, which includes a manual inlet valve and an electric inlet valve. Furthermore, the tank is connected to an acid supply line for introducing concentrated hydrochloric acid, which includes a manual inlet valve and an electric inlet PPR valve. Finally, the tank is equipped with an online hydrochloric acid concentration monitoring instrument, which is connected to the intelligent control unit for feedback control of the acid inlet valve's opening and closing.

6. The reverse osmosis acid addition device according to claim 1, characterized in that: An acid addition device is installed at the acid addition point, leading to a chemical dosing valve in the reverse osmosis feed water pipeline; a security filter inlet valve is installed on the pipeline between the outlet of the multi-stage static mixer and the inlet of the security filter.

7. A reverse osmosis acid addition device according to claim 1, characterized in that: The online water quality monitoring unit includes a flow sensor, a pH sensor, a temperature sensor, a hardness sensor, and an alkalinity sensor; the pH sensor adopts a dual-liquid interface structure; the hardness sensor and the alkalinity sensor are equipped with a conical flow tank and an automatic cleaning interface; a safety barrier is installed between the online water quality monitoring unit and the intelligent control unit.

8. A reverse osmosis acid addition device according to claim 1, characterized in that: The metering pump head is a hydraulic diaphragm pump; the pulsation damper is a pneumatic pulsation damper; and the back pressure valve is an anti-siphon check valve.

9. A reverse osmosis acid addition device according to claim 1, characterized in that: The intelligent control unit has a built-in Langerier saturation index calculation model. It takes the Langerier saturation index value of the concentrate being kept stable at -0.2-0 as the control target, and outputs the acid addition command by using a flow feedforward combined with pH closed-loop regulation. The intelligent control unit has a temperature compensation function, which corrects the calcium carbonate saturation pH value in real time according to the inlet water temperature.

10. A method for regulating and controlling a reverse osmosis acid addition device, characterized in that, Includes the following steps: S1. Start the metering pump to draw acid from the anti-corrosion storage tank. After the flow pulsation is eliminated by the pulsation damper and the outlet pressure is stabilized by the back pressure valve, it is smoothly added to the inlet pipe at the front end of the security filter. After the acid solution and raw water are initially mixed, they enter a multi-stage static mixer. The fluid is cut, rotated and tumbled multiple times by multiple spiral mixing units to achieve uniform mixing of acid solution and raw water and avoid local over-acidity or local high alkalinity. S2. The water quality online monitoring unit, located upstream of the acid addition point and at the outlet of the static mixer, collects parameters such as influent flow rate, pH value, temperature, calcium hardness, and total alkalinity in real time, and obtains the reverse osmosis system recovery rate through the intelligent control unit; the intelligent control unit performs filtering, smoothing, and outlier removal preprocessing on the collected parameters. S3, the intelligent control unit performs temperature compensation based on the inlet water temperature, corrects the calcium carbonate saturation pH value in real time, and calculates the concentrated water Langerier saturation index value online in combination with calcium hardness, total alkalinity and system recovery rate; at the same time, it corrects the calculated acid addition amount based on the concentration signal fed back by the hydrochloric acid concentration monitoring instrument. S4. Using the influent flow rate and total alkalinity as feedforward variables, the theoretical acid addition amount is calculated using the carbonic acid balance relationship, and the basic acid addition amount command is output. When the influent flow rate changes, the feedforward regulation adjusts the operating frequency or stroke of the metering pump in real time so that the acid addition amount changes synchronously with the influent flow rate. S5. Using the Langerilla saturation index target value of -0.2-0 as the control index, the real-time concentrated Langerilla saturation index value is compared with the target value. A correction amount is generated through the PID algorithm to perform closed-loop fine-tuning of the basic acid addition amount. The corrected acid addition amount command is converted into a 4-20mA analog signal or PWM signal and output to the metering pump. The speed or stroke of the metering pump is adjusted in real time to stabilize the concentrated Langerilla saturation index value within the set range.

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