Fully-automatic pH regulating system based on liquid mixed reactor

Abstract

The present application relates to the technical field of industrial wastewater treatment, and discloses a full-automatic pH adjusting system and process based on a liquid mixing reactor. The system comprises a raw material supply unit, a liquid mixing reactor, a discharge unit, a dosing unit and a detection control unit connected in sequence. The liquid mixing reactor adopts a pipeline continuous flow design, the process pipeline adopts a specific material and length, and is provided with a plurality of one-time formed elbows. The pipeline is provided with a feeding port, a dosing port, a plurality of pH detection ports and a discharge port along the flow direction, wherein the dosing port is inserted obliquely along the flow, and the pH detection ports are inserted obliquely against the flow. The detection control unit collects the signals of the plurality of pH detection ports downstream, feeds back the dosing amount of the precision metering pump in the dosing unit, and realizes closed-loop control. The present application realizes rapid and uniform mixing, high-precision control and full-automatic operation of the wastewater pH adjusting process, and provides stable and reliable pretreatment guarantee for the subsequent evaporation process.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, and particularly relates to a fully automatic pH adjustment system based on a liquid mixing reactor. Background Technology

[0002] In the industrial sector, evaporation is a common process for reducing the volume of wastewater containing ammonium chloride (NH4Cl). To effectively prevent ammonia nitrogen (NH3-N) from escaping with water vapor into the condensate during evaporation, the pH of the wastewater must be precisely adjusted from near-neutral or alkaline to acidic (typically pH < 5) before it enters the evaporator. Currently, the industry commonly uses stirred tanks (reaction vessels) for manual or semi-automatic acid adjustment.

[0003] The traditional method has the following obvious drawbacks: 1) Uneven mixing: Relying on mechanical stirring, the mixing intensity is limited, and it is easy to have local areas that are too acidic or have pH that does not meet the standard; 2) Lagging control and poor precision: Usually, only a pH probe is set at a single position in the mixing tank, and the detection data is not representative enough and cannot truly reflect the overall mixing effect, resulting in lagging control feedback and low adjustment precision; 3) Low degree of automation and reliance on manual labor: The dosage is mostly based on experience, making it difficult to achieve stable and continuous precise control, and human error is large; 4) Large equipment footprint and high energy consumption: The mixing tank is large in size, and the matching stirring motor has high energy consumption.

[0004] These problems directly lead to large pH fluctuations in the pretreated effluent, affecting the stable operation of subsequent evaporation processes and potentially causing excessive ammonia nitrogen levels in the condensate, increasing subsequent treatment costs. Therefore, there is an urgent need for pretreatment equipment and processes that can achieve rapid, uniform mixing and high-precision, fully automated pH adjustment. Summary of the Invention

[0005] This invention provides a fully automatic pH adjustment system based on a liquid mixing reactor, which aims to solve the problems of uneven mixing, low control accuracy, poor automation, and unstable operation that exist when using traditional stirred tanks (reactors) to adjust the pH of ammonium chloride-containing wastewater before evaporation.

[0006] The present invention is implemented as follows: a fully automatic pH adjustment system based on a liquid mixing reactor includes a raw material supply unit, a liquid mixing reactor and a discharge unit connected in sequence by pipelines, and also includes a dosing unit and a detection and control unit. The outlet of the raw material supply unit is connected to the inlet of the liquid mixing reactor; The dosing unit includes a hydrochloric acid dosing branch and a formaldehyde dosing branch, which are respectively connected to the acid dosing port and the formaldehyde dosing port of the liquid mixing reactor. The detection and control unit includes multiple pH sensors located at different positions on the liquid mixing reactor, and a programmable logic controller (PLC) that is signal-connected to all the pH sensors, the feed pump of the raw material supply unit, and the metering pump of the dosing unit.

[0007] Preferably, the raw material supply unit includes a raw liquid buffer tank and a feed pump, wherein the inlet pipe of the feed pump is connected to the raw liquid buffer tank and the outlet pipe is connected to the feed inlet of the liquid mixing reactor.

[0008] Preferably, the liquid mixing reactor includes a process pipe as the main flow channel. The process pipe is made of TA2 material, with an outer diameter of 57 mm, a wall thickness of 2.5 mm, and a total length of not less than 75 meters, so that the designed residence time of the material in the pipe is not less than 0.5 minutes and the designed flow velocity is 0.4 m / s.

[0009] Preferably, the process pipeline is provided with a plurality of elbows formed in one step by a pipe bending machine, and the number of elbows is 15. The liquid mixing reactor also includes a support structure, which includes multiple support columns made of No. 8 channel steel and U-shaped clamps for fixing the process pipeline.

[0010] Preferably, the process pipeline is provided with a feed inlet, a first pH detection port, an acid addition port, a second pH detection port, a third pH detection port, a formaldehyde addition port, a fourth pH detection port, and a discharge port in sequence along the material flow direction, and a reflux port is also provided on the process pipeline; The acid addition port and formaldehyde addition port are inserted into the process pipe at a 45° angle in the direction of flow, and the first, second, third and fourth pH detection ports are inserted into the process pipe at a 45° angle in the direction of flow counter.

[0011] Preferably, the hydrochloric acid dosing branch of the dosing unit includes a hydrochloric acid storage tank, a hydrochloric acid delivery pump, and a first precision metering pump connected in sequence by pipelines. The first precision metering pump is located on one side of the acid inlet, and the outlet pipe of the first precision metering pump is connected to the acid inlet; The formaldehyde dosing branch of the dosing unit includes a formaldehyde storage tank, a formaldehyde delivery pump, and a second precision metering pump connected in sequence by pipelines. The second precision metering pump is located on one side of the formaldehyde inlet, and the outlet pipe of the second precision metering pump is connected to the formaldehyde inlet; The hydrochloric acid dosing branch and / or the formaldehyde dosing branch also include a buffer tank disposed between the delivery pump and the precision metering pump to prevent the pressure shock generated by the delivery pump from acting directly on the precision metering pump.

[0012] Preferably, in the detection control unit, the pH sensor includes a first sensor installed at a first pH detection port, a second sensor installed at a second pH detection port, a third sensor installed at a third pH detection port, and a fourth sensor installed at a fourth pH detection port. The PLC is configured to receive signals from at least two downstream pH sensors and to perform PID feedback regulation on the acid addition amount of the first precision metering pump based on the average or maximum value of the multi-point signals.

[0013] Preferably, the discharge unit includes a discharge buffer tank, and the inlet pipe of the discharge buffer tank is connected to the discharge port of the liquid mixing reactor.

[0014] Preferably, a plurality of control valves are provided on the feed pipeline between the raw material supply unit and the liquid mixing reactor, and on the dosing pipeline between the dosing unit and the liquid mixing reactor; the valves include one or more of the following: a switching valve for pipeline isolation and maintenance, a check valve for preventing fluid backflow, and a regulating valve for adjusting pipeline flow.

[0015] The process of a fully automated pH adjustment system includes the following steps: S1: After being temporarily stored in the raw material supply unit, the ammonium chloride-containing wastewater is pumped into the liquid mixing reactor by the feed pump at a constant flow rate of 3 m³ / h. S2: Wastewater flows in the process pipeline, and the detection and control unit detects its initial pH value through the first pH detection port; S3: Based on the deviation between the initial pH value and the set target value, the PLC instructs the first precision metering pump of the dosing unit to start and inject a quantitative amount of hydrochloric acid through the acid inlet; S4: When the mixture flows through the second, third and fourth pH detection ports downstream, it is continuously monitored. The PLC integrates these multiple pH signals and provides real-time feedback on the hydrochloric acid injection volume of the first precision metering pump to form a closed-loop control. S5: According to process requirements, formaldehyde is injected through the formaldehyde inlet via the second precision metering pump of the dosing unit. S6: Wastewater whose pH value has been adjusted and stabilized within the target acidic range is discharged from the outlet to the discharge unit.

[0016] Compared with related technologies, the fully automatic pH adjustment system based on a liquid mixing reactor provided by this invention has the following advantages: 1. Significantly Improved Mixing Efficiency and Uniformity: This invention completely replaces the traditional stirred tank with a continuous flow reactor of a specific length. The material flows within the pipe at a set velocity, passing through multiple specially designed high-curvature bends, generating continuous and intense turbulence. This fluid dynamics-based mixing method allows acids, formaldehyde, and other reagents to be continuously cut, diffused, and recombined with wastewater along the main flow direction, achieving rapid and uniform mixing at the molecular level. In contrast, traditional stirred tanks rely on the local shearing of mechanical impellers, resulting in mixing dead zones, concentration gradients that are too acidic near the dosing point and insufficient at the far end, poor mixing uniformity, and a longer time required to achieve the same mixing effect. 2. By setting multiple pH detection points at intervals along the flow direction of the process pipeline and adopting a counter-current oblique insertion sampling method, more representative fluid samples from the pipeline cross-section can be effectively obtained, avoiding the randomness of single-point detection due to the influence of the pipe wall boundary layer or local eddies. Multi-point monitoring constitutes a distributed sensing network for the reaction process, and the data more accurately reflects the overall pH status of the system. 3. Based on a programmable logic controller (PLC), the pH signals from multiple downstream monitoring points (such as average or most conservative values) are used to adjust the upstream chemical dosage in real time using PID feedback, forming a feedforward-feedback composite closed-loop control system. This "result-based correction action" strategy can quickly respond to fluctuations in influent water quality or flow rate, overcoming the shortcomings of traditional methods that rely on single-point, lag-signal adjustment, resulting in large control deviations and slow responses. This allows for stable and precise control of the effluent pH value within a narrow target range. 4. Optimized equipment structure, high operational economy and reliability, compact structure, small footprint. The pipeline reactor can be flexibly arranged according to the site (e.g., coiled pipes, serpentine pipes), significantly saving equipment floor space compared to a bulky mixing tank. The system power mainly comes from the feed pump and dosing pump, eliminating the need for a high-power stirring motor required for a mixing tank, significantly reducing operating energy consumption. Good durability and easy maintenance: The main body of the process piping is made of corrosion-resistant TA2 (industrial pure titanium) material, and key connections use a one-time forming process for bending pipes, reducing the number of welds, lowering the risk of leakage, and improving the overall corrosion resistance and service life of the equipment. Modular design also facilitates fault diagnosis and component replacement. 5. This invention provides stable and precisely pH-compliant feed water, ensuring stable operation of subsequent evaporation processes from the source. It effectively inhibits ammonia nitrogen volatilization, reducing the ammonia nitrogen concentration in the evaporation condensate, which not only improves evaporation efficiency but also reduces the pressure on end-of-pipe wastewater treatment, enhancing the overall efficiency and reliability of the entire wastewater treatment process. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow and liquid mixing reactor connection of the fully automatic pH adjustment system of the present invention; Figure 2 This is a schematic diagram of the main structure of the liquid mixing reactor of the present invention; Figure 3 For the present invention Figure 2 A magnified view of a specific pipe opening in the middle section; Figure 4 This is a schematic diagram of the installation of the support structure (column and U-shaped clip) of the present invention.

[0018] In the diagram: 100, Raw material supply unit; 101, Raw material buffer tank; 102, Feed pump; 200, Liquid mixing reactor; 1, Process piping; 2, Elbow; 3, Support column; 4, U-shaped clamp; N1, Inlet; N2, First pH detection port; N3, Acid addition port; N4, Second pH detection port; N5, Third pH detection port; N6, Reflux port; N7, Formaldehyde addition port; N8, Fourth pH detection port; N9, Outlet; 300, Outlet unit; 301, Outlet buffer tank; 400, Dosing unit; 401, Hydrochloric acid storage tank; 402, Hydrochloric acid transfer pump; 403, Formaldehyde storage tank; 404, Formaldehyde transfer pump; 405, First precision metering pump; 406, Second precision metering pump; 407, Buffer tank. Detailed Implementation

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] Please see Figures 1 to 4 The fully automatic pH adjustment system based on a liquid mixing reactor provided by the present invention mainly includes a raw material supply unit 100, a liquid mixing reactor 200, a discharge unit 300, a dosing unit 400, and a detection and control unit.

[0022] The raw material supply unit 100 provides a stable flow rate of wastewater to be treated. It includes a raw material buffer tank 101 and a feed pump 102. The raw material buffer tank 101 collects, temporarily stores, and homogenizes the ammonium chloride-containing wastewater from the upstream process, buffering fluctuations in its flow rate and concentration. The feed pump 102 is preferably a corrosion-resistant centrifugal pump or screw pump, with its inlet connected to the bottom of the raw material buffer tank 101 via a pipe, and its outlet connected to the inlet N1 of the liquid mixing reactor 200. The operation of the feed pump 102 is controlled by a PLC in the detection and control unit to maintain a constant feed flow rate, for example, 3 m³ / h.

[0023] The liquid mixing reactor 200 is primarily composed of a long process pipe 1. In a preferred embodiment of the invention, the process pipe 1 is made of TA2 (industrial pure titanium) material resistant to hydrochloric acid corrosion, with an outer diameter of 57 mm and a wall thickness of 2.5 mm. Based on the processing flow rate (3 m³ / h) and the required residence time (≥0.5 minutes), the total length of the pipe is designed to be 96 meters, at which point the average flow velocity inside the pipe is approximately 0.4 m / s. The process pipe 1 is connected by 15 large-curvature elbows 2, formed by a pipe bending machine in a single cold bending process, and arranged in a compact serpentine or coiled structure. This design not only reduces the number of welds and improves equipment integrity, but more importantly, the fluid flowing through the elbows 2 generates strong turbulence, continuously promoting the mixing of the added reagents and wastewater. The entire reactor is supported by multiple support columns 3 made of 8# channel steel, and the process pipe 1 is firmly fixed to the support columns 3 by U-shaped clamps 4, ensuring a stable and reliable structure.

[0024] Multiple functional ports are sequentially installed along the material flow direction on process pipeline 1. Their connection relationships and functions are as follows: Feed inlet N1: Located at the starting end, it connects to the incoming material pipe of the raw material supply unit 100.

[0025] The first pH detection port, N2, is located downstream of N1 and upstream of the acid addition port, N3. This port is inserted at a 45° angle against the current and is equipped with a pH sensor for detecting the unadjusted stock solution or as an initial reference value.

[0026] Acid dosing port N3: Located downstream of N2. This port is inserted at a 45° angle downstream and connects to the hydrochloric acid dosing branch of dosing unit 400. The angled insertion downstream facilitates the acid jet to be in the same direction as the main fluid, allowing it to be rapidly entrained and diffused.

[0027] The second pH sensor port N4 and the third pH sensor port N5 are sequentially located downstream of the acid inlet N3 along the flow direction. Both are inserted at a 45° angle against the current and are equipped with pH sensors. This counter-current angled insertion design effectively collects fluid samples from the central region of the pipeline, avoiding the boundary layer of the pipe wall, making the measured values ​​more representative. They are used to monitor the mixing and reaction effects of different pipe sections after acid addition.

[0028] Return port N6: Can be located downstream of N5. This port can be connected to the return pipeline to the inlet of the raw liquid buffer tank 101 via a valve, as needed for process operation, material circulation under abnormal conditions, or sampling.

[0029] Formaldehyde dosing port N7: Located downstream of N5 (or N6). This port is also inserted at a 45° angle downstream and connects to the formaldehyde dosing branch of dosing unit 400 for adding formaldehyde and other auxiliary agents as needed.

[0030] The fourth pH sensor port, N8, is located downstream of N7, near the outlet. This port is inserted at a 45° angle against the current and houses a pH sensor to monitor the pH value of the final effluent. It is one of the key feedback points for closed-loop control.

[0031] Discharge port N9: Located at the end, connected to discharge unit 300.

[0032] It should be noted that "countercurrent oblique 45° insertion" refers to the central axis of the pipe opening forming a 135° angle with the main flow direction inside the process pipe 1 (i.e., insertion at a 45° angle in the opposite direction); "co-current oblique 45° insertion" refers to a 45° angle (i.e., insertion at a 45° angle in the same direction). Those skilled in the art will understand that this angle (45°) is a preferred embodiment. In practical applications, adjustments within the range of 30°-60° can still achieve the purpose of this invention based on fluid characteristics.

[0033] The dosing unit 400 is responsible for accurately adding chemicals to the system, including separate hydrochloric acid dosing branches and formaldehyde dosing branches.

[0034] The hydrochloric acid dosing branch includes a hydrochloric acid storage tank 401, a hydrochloric acid transfer pump 402, a buffer tank 407, and a first precision metering pump 405, connected sequentially by pipelines. The hydrochloric acid transfer pump 402 is responsible for transferring hydrochloric acid from the storage tank to the buffer tank 407. The buffer tank 407 is used to eliminate pressure pulsations generated by the transfer pump, providing a stable inlet pressure for the downstream first precision metering pump 405. The first precision metering pump 405 (such as a mechanical diaphragm metering pump) delivers precisely metered hydrochloric acid through the pipeline to the acid dosing port N3, according to instructions from the detection and control unit.

[0035] The formaldehyde dosing branch has a similar structure, including a formaldehyde storage tank 403, a formaldehyde delivery pump 404, and a second precision metering pump 406 connected in sequence by pipes. The second precision metering pump 406 accurately adds formaldehyde to the formaldehyde dosing port N7.

[0036] Regarding the specific piping configuration, the dosing line connecting to the acid inlet N3 can use, for example, a pipe marked "PL-0101-15-304," indicating that this section of pipe is made of 304 stainless steel with a nominal diameter of DN15. The pipe connecting to the main body of process piping 1 can use, for example, a pipe marked "PL-0101-50-PE," indicating that this section of pipe is made of polyethylene (PE) with a nominal diameter of DN50. These specific material and specification selections are the preferred options based on the corrosiveness of the medium and process requirements.

[0037] The detection and control unit is centered around a programmable logic controller (PLC). Four pH sensors (not individually labeled in the diagram) are installed at the four detection ports N2, N4, N5, and N8, respectively, transmitting standard signals to the PLC in real time. The PLC is also communicatively connected to the feed pump 102, the first precision metering pump 405, and the second precision metering pump 406. The PLC has a preset target pH control program. The preferred control logic is as follows: pH values ​​are collected from the three detection points N4, N5, and N8 downstream of the acid addition point. The average (or lowest) value of these three values ​​is taken as the representative pH value of the current system and compared with the preset target value (e.g., pH=4.0). A PID (proportional-integral-derivative) control algorithm is used for real-time calculation, outputting a control signal (e.g., 4-20mA) to the first precision metering pump 405. This dynamically adjusts the pump's stroke frequency or stroke, thereby precisely changing the amount of acid added, forming a fast closed-loop feedback control circuit. For formaldehyde dosing, the PLC can control the start / stop and flow rate of the second precision metering pump 406 according to a preset program or signals from other sensors (such as ORP oxidation-reduction potential).

[0038] The discharge unit 300 mainly includes a discharge buffer tank 301, whose inlet is connected to the discharge port N9 of the liquid mixing reactor 200 via a pipeline. The wastewater, after precise pH adjustment, is temporarily stored here to provide a stable and qualified feed for the subsequent evaporation process.

[0039] In addition, various valves (not shown in the figure) are installed on the key pipelines of the system as needed. For example, shut-off valves or ball valves can be installed at the outlet of feed pump 102 and the inlet and outlet of each metering pump (405, 406) for isolation during equipment maintenance; check valves can be installed on the metering pump outlet pipeline to prevent backflow of the medium; needle valves or regulating valves can be installed on the sampling or fine adjustment branches.

[0040] Working principle: During system operation, ammonium chloride-containing wastewater first enters the raw solution buffer tank 101. Under PLC control, the feed pump 102 pumps the wastewater into the process pipeline 1 of the liquid mixing reactor 200 at a constant flow rate (e.g., 3 m³ / h). When the wastewater flows through the first pH detection port N2, the pH sensor detects its initial value and uploads it to the PLC.

[0041] The PLC calculates the initial acid addition amount based on the deviation between the initial pH and the set target value, and instructs the first precision metering pump 405 to start, injecting a measured amount of hydrochloric acid into the pipeline through the acid addition port N3. Under the action of the co-current oblique injection and the turbulence generated by the subsequent elbow 2, the acid solution quickly mixes with the wastewater.

[0042] The mixed liquor continues to flow downstream, being continuously monitored as it passes through the second, third, and fourth pH detection ports (N4, N5, N8). The PLC continuously receives pH signals from these three downstream points and, through the aforementioned multi-point feedback control logic, adjusts the acid addition rate of the first precision metering pump 405 in real time and with precision. This closed-loop control, which adjusts the upstream "action" based on the downstream "result," ensures that the final effluent pH value (based on the monitoring value at point N8) can quickly and stably reach and be maintained within the set target range.

[0043] If the process requires it (e.g., to fix or remove certain impurities), the PLC can control the second precision metering pump 406 to inject a quantitative amount of formaldehyde through the formaldehyde inlet N7.

[0044] Finally, the wastewater, with pH adjusted to the standard and uniformly mixed, is discharged from outlet N9 and enters outlet buffer tank 301, completing the entire treatment process. Return outlet N6 can guide a portion of the material back to the original liquid buffer tank 101 for further treatment during system startup, commissioning, or when the effluent fails to meet standards.

[0045] It is worth noting that the circuits, electronic components, and modules involved in this invention are all existing technologies, which can be fully implemented by those skilled in the art, and need not be elaborated upon. The content protected by this invention does not involve improvements to the software and methods.

[0046] It should be understood that the disclosed apparatus can be implemented in other ways, as illustrated in the embodiments provided in this application. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or communication connections shown or discussed may be through some interfaces; the indirect coupling or communication connections between devices or units may be telecommunications or other forms.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A fully automated pH adjustment system based on a liquid mixing reactor, characterized in that, It includes a raw material supply unit (100), a liquid mixing reactor (200) and a discharge unit (300) connected in sequence by pipelines, as well as a dosing unit (400) and a detection and control unit; The outlet of the raw material supply unit (100) is connected to the feed inlet (N1) of the liquid mixing reactor (200). The dosing unit (400) includes a hydrochloric acid dosing branch and a formaldehyde dosing branch, which are respectively connected to the acid dosing port (N3) and the formaldehyde dosing port (N7) of the liquid mixing reactor (200). The detection and control unit includes multiple pH sensors located at different positions on the liquid mixing reactor (200), and a programmable logic controller (PLC) that is connected to all the pH sensors, the feed pump (102) of the raw material supply unit (100), and the metering pump of the dosing unit (400).

2. The fully automatic pH adjustment system as described in claim 1, characterized in that, The raw material supply unit (100) includes a raw liquid buffer tank (101) and a feed pump (102). The inlet pipe of the feed pump (102) is connected to the raw liquid buffer tank (101), and the outlet pipe is connected to the feed port (N1) of the liquid mixing reactor (200).

3. The fully automatic pH adjustment system as described in claim 1, characterized in that, The liquid mixing reactor (200) includes a process pipe (1) as the main flow channel. The process pipe (1) is made of TA2 material, with an outer diameter of 57 mm, a wall thickness of 2.5 mm, and a total length of not less than 75 meters, so that the designed residence time of the material in the pipe is not less than 0.5 minutes and the designed flow rate is 0.4 m / s.

4. The fully automatic pH adjustment system as described in claim 3, characterized in that, The process pipeline (1) is provided with a plurality of elbows (2) formed in one step by a pipe bending machine, and the number of elbows (2) is 15. The liquid mixing reactor (200) also includes a support structure, which includes multiple support columns (3) made of No. 8 channel steel and U-shaped clamps (4) for fixing the process pipeline (1).

5. The fully automatic pH adjustment system as described in claim 3, characterized in that, The process pipeline (1) is provided with an inlet (N1), a first pH detection port (N2), an acid addition port (N3), a second pH detection port (N4), a third pH detection port (N5), a formaldehyde addition port (N7), a fourth pH detection port (N8), and an outlet (N9) in sequence along the material flow direction. A reflux port (N6) is also provided on the process pipeline (1). The acid inlet (N3) and formaldehyde inlet (N7) are inserted into the process pipe (1) at a 45° angle in the direction of flow, and the first, second, third, and fourth pH detection ports (N2, N4, N5, N8) are inserted into the process pipe (1) at a 45° angle in the direction of flow.

6. The fully automatic pH adjustment system as described in claim 5, characterized in that, The hydrochloric acid dosing branch of the dosing unit (400) includes a hydrochloric acid storage tank (401), a hydrochloric acid transfer pump (402), and a first precision metering pump (405) connected in sequence by pipelines. The first precision metering pump (405) is located on the side of the acid inlet (N3), and the outlet pipe of the first precision metering pump (405) is connected to the acid inlet (N3). The formaldehyde dosing branch of the dosing unit (400) includes a formaldehyde storage tank (403), a formaldehyde delivery pump (404), and a second precision metering pump (406) connected in sequence by pipelines. The second precision metering pump (406) is located on the side of the formaldehyde inlet (N7), and the outlet pipe of the second precision metering pump (406) is connected to the formaldehyde inlet (N7). The hydrochloric acid dosing branch and / or the formaldehyde dosing branch also include a buffer tank (407) disposed between the delivery pump and the precision metering pump to prevent the pressure shock generated by the delivery pump from acting directly on the precision metering pump.

7. The fully automatic pH adjustment system as described in claim 6, characterized in that, In the detection control unit, the pH sensor includes a first sensor installed in the first pH detection port (N2), a second sensor installed in the second pH detection port (N4), a third sensor installed in the third pH detection port (N5), and a fourth sensor installed in the fourth pH detection port (N8). The PLC is configured to receive signals from at least two downstream pH sensors and to perform PID feedback regulation on the amount of acid added by the first precision metering pump (405) based on the average or maximum value of the multi-point signals.

8. The fully automatic pH adjustment system as described in claim 1, characterized in that, The discharge unit (300) includes a discharge buffer tank (301), the inlet pipe of which is connected to the discharge port (N9) of the liquid mixing reactor (200).

9. The fully automatic pH adjustment system as described in claim 8, characterized in that, Multiple control valves are provided on the feed line between the raw material supply unit (100) and the liquid mixing reactor (200), and on the dosing line between the dosing unit (400) and the liquid mixing reactor (200); the valves include one or more of the following: a switching valve for pipeline isolation and maintenance, a check valve for preventing fluid backflow, and a regulating valve for regulating pipeline flow.

10. A process employing the fully automatic pH adjustment system as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: After being temporarily stored in the raw material supply unit (100), the ammonium chloride-containing wastewater is pumped into the liquid mixing reactor (200) by the feed pump (102) at a constant flow rate of 3 m³ / h. S2: Wastewater flows in the process pipeline (1), and the detection control unit detects its initial pH value through the first pH detection port (N2); S3: Based on the deviation between the initial pH value and the set target value, the PLC instructs the first precision metering pump (405) of the dosing unit (400) to start and inject a quantitative amount of hydrochloric acid through the acid inlet (N3); S4: When the mixed liquid flows through the second, third, and fourth pH detection ports (N4, N5, N8) downstream, it is continuously monitored. The PLC integrates these multi-point pH signals and provides real-time feedback on the hydrochloric acid injection volume of the first precision metering pump (405) to form a closed-loop control. S5: According to process requirements, formaldehyde is injected through the formaldehyde inlet (N7) via the second precision metering pump (406) of the dosing unit (400); S6: Wastewater whose pH value has been adjusted and stabilized within the target acidic range is discharged from the outlet (N9) to the discharge unit (300).

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