Automatic Alkali Addition System and Method for Coking Wastewater

Abstract

This invention relates to an automatic alkali addition system for coking wastewater, comprising an alkali storage tank, a conveying unit, a pipeline unit, a detection unit, and a control unit; and an automatic alkali addition method for coking wastewater, comprising the following steps: 1) setting a target pH value according to the ammonia nitrogen compliance requirements of the coking wastewater; 2) collecting the measured pH value at the outlet of the ammonia stripping tower wastewater in real time and transmitting it to the control unit in real time; 3) the control unit, based on the measured pH value and the target pH value, using a PID algorithm, obtaining a control signal for adjusting the stroke or frequency of the alkali metering pump; 4) the conveying unit, based on the control signal obtained in step 3), adjusting the alkali dosage in real time; 5) the control unit continuously collecting the measured pH value and repeating steps 2) to 4), dynamically correcting the alkali dosage in real time, which can effectively achieve unblocked continuous operation of the pipeline, precise pH control, while reducing alkali consumption and maintenance costs.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to an automatic alkali addition system and method for coking wastewater. Background Technology

[0002] Coking wastewater refers to the wastewater generated during the coking process. Its composition is highly complex (containing various recalcitrant pollutants such as phenols, cyanides, and ammonia nitrogen) and is generally acidic, with a pH value typically between 4.5 and 6.5. If this acidic wastewater enters the subsequent treatment system without effective pretreatment, two major problems will arise: First, the acidic medium will continuously corrode the transport pipelines and treatment equipment, shortening their lifespan and forcing companies to frequently invest in maintenance and replacement, significantly increasing operating costs. Second, the acidic environment will disrupt the optimal reaction conditions for subsequent processes such as phenol removal and biochemical reactions, interfering with microbial activity and chemical reaction balance, leading to decreased treatment efficiency, fluctuating effluent quality, and difficulty in achieving stable and compliant discharge of pollutants such as ammonia nitrogen. Therefore, precisely controlling the pH value of coking wastewater within the slightly alkaline range through alkali addition is not only a crucial pretreatment step to provide stable and suitable water quality for subsequent processes, but also a core requirement for fundamentally avoiding equipment corrosion risks and ensuring the long-term stable operation of the system.

[0003] Currently, the alkali addition adjustment of coking wastewater in the industry is still mainly controlled manually. The specific process is as follows: operators collect wastewater samples at fixed intervals, obtain values ​​through rapid pH test strips or precise laboratory analysis, and then manually adjust the alkali pump flow rate or alkali concentration based on operational experience. However, this method has many inherent drawbacks that are difficult to overcome, seriously affecting the final wastewater treatment effect and the economic efficiency of system operation, as follows:

[0004] First, there is a significant lag in detection and adjustment. Manual detection cycles typically last for an hour or even longer, making it difficult to capture dynamic fluctuations in wastewater pH in real time. This results in a complete disconnect between adjustment actions and water quality fluctuations. Consequently, the pH value deviates from the optimal control range for extended periods. This makes it impossible to respond promptly to sudden changes in water quality to ensure the stability of subsequent processes, and it is also difficult to avoid the continuous corrosion of equipment by acidic wastewater, creating a vicious cycle of "detection lag - inaccurate adjustment - cumulative damage".

[0005] Secondly, the adjustment precision is low and the economy is poor. Manual operation relies entirely on experience and judgment, lacking scientific quantitative basis, resulting in large fluctuations in pH value after adding alkali, and easily leading to insufficient or excessive alkali addition. When alkali is insufficient, the wastewater remains in an acidic or weakly acidic state, failing to meet the requirements of subsequent treatment processes, thus reducing treatment efficiency and effluent compliance rate, while accelerating equipment corrosion and aging. On the other hand, excessive alkali addition results in ineffective alkali waste. According to statistics, this waste causes companies to lose an average of 10-20 tons of alkali annually, resulting in direct economic losses of 50,000-100,000 yuan. In addition, excessive alkali can also cause alkalinity imbalance in subsequent processes, increasing the difficulty of advanced treatment.

[0006] Third, the process is labor-intensive and lacks operational stability. Operators are required to perform repetitive sampling, testing, and adjustment tasks over extended periods, resulting in high labor intensity. Furthermore, individual errors in manual operation (such as skill level, lack of responsibility, and judgment bias) lead to inconsistent adjustment effects, making the system's operational stability overly dependent on personnel condition and causing significant fluctuations in treatment effectiveness. In addition, during actual production, fluctuations in coking production load cause frequent and drastic fluctuations in wastewater inflow (fluctuations can reach ±30%) and acidity (pH value). The reaction speed and control precision of manual alkali addition are simply not suitable for such operating conditions, further exacerbating pH drift and affecting the stability of subsequent treatment processes.

[0007] To address the aforementioned shortcomings of manual alkali addition, those skilled in the art have attempted to develop various automated or semi-automated alkali addition control schemes. However, these schemes suffer from problems such as complex control logic, indirect feedback paths, and weak adaptability to operating conditions. For example, some schemes require simultaneous collection of multiple parameters, such as ammonia nitrogen concentration and water flow rate, for feedforward calculations, which increases hardware configuration costs and calibration difficulty, and is prone to error accumulation due to parameter coupling. Furthermore, some schemes rely on indirect measurement signals from intermediate links for regulation, resulting in long feedback paths and unresolved adjustment lag issues, making it difficult to cope with ±30% fluctuations in influent flow. In other words, these schemes cannot achieve precise, real-time, and stable control of the pH value of coking wastewater, and may still lead to problems such as decreased efficiency of subsequent processes, excessive ammonia nitrogen in effluent, and accelerated equipment corrosion, failing to meet the actual needs of industrial production. Therefore, there is an urgent need to develop an automated alkali addition method suitable for coking wastewater that can effectively solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing an automatic alkali addition system and method for coking wastewater, which can effectively achieve unblocked continuous operation of pipelines, precise pH control, and reduce alkali consumption and maintenance costs.

[0009] The objective of this invention is achieved through the following approach:

[0010] An automatic alkali addition system for coking wastewater includes an alkali storage tank, a conveying unit, a piping unit, a detection unit, and a control unit.

[0011] Alkali storage tank, used to store alkali solution to be added;

[0012] The conveying unit is used to extract alkali from the alkali storage tank and precisely adjust the output of alkali according to the instructions of the control unit.

[0013] Piping unit, used to achieve high-speed, blockage-free transport of alkali solution;

[0014] The detection unit is used to collect the pH value signal of coking wastewater in real time during the ammonia stripping process and transmit it to the control unit.

[0015] The control unit receives signals from the detection unit and outputs instructions to the delivery unit to achieve real-time dynamic adjustment of the alkali addition amount.

[0016] Preferably, the pipe unit is a straight stainless steel pipe without bends.

[0017] Preferably, the detection unit includes at least two pH sensors, which are installed on the wastewater outlet pipe of the ammonia stripping tower.

[0018] Preferably, the conveying unit includes at least two alkali metering pumps, and the output of alkali solution can be precisely controlled by adjusting the stroke or frequency of the alkali metering pumps.

[0019] Preferably, a method for automatically adding alkali to coking wastewater using an automatic alkali addition system includes the following steps:

[0020] 1) Based on the ammonia nitrogen compliance requirements of coking wastewater and the optimal pH conditions of subsequent treatment processes, and combined with process test data, set the target pH value in the control unit.

[0021] 2) The pH value at the outlet of the ammonia stripping tower wastewater is collected in real time using a pH sensor and transmitted to the control unit in real time;

[0022] 3) The control unit uses a PID algorithm to obtain a control signal for adjusting the stroke or frequency of the alkali metering pump based on the measured pH value and the target pH value.

[0023] 4) The conveying unit adjusts the amount of alkali solution added in real time according to the control signal obtained in step 3);

[0024] 5) The control unit continuously collects the measured pH value and repeats steps 2) to 4) to dynamically adjust the amount of alkali solution added in real time.

[0025] Preferably, step 3) involves obtaining the control signal, which includes:

[0026] 3-1) Calculate the pH deviation value based on the measured pH value and the pH target value, wherein the pH deviation value = pH target value - pH measured value;

[0027] 3-2) Obtain the integrated control output value according to the following formula, and convert it into a control signal. The formula for calculating the integrated control output value is:

[0028]

[0029] In the formula, This is the proportionality coefficient. This is the pH deviation value. The integral coefficient is... is the differential coefficient.

[0030] Preferably, in step 4), an allowable deviation threshold is set. The method for adjusting the alkali dosage in real time according to the control signal is as follows:

[0031] ① When pH deviation value > + At the same time, the alkali metering pump increases its stroke or frequency, and increases the amount of alkali added according to the PID output ratio;

[0032] ② When the pH deviation value is <- When the alkali metering pump reduces its stroke or frequency, the amount of alkali added is reduced according to the PID output ratio.

[0033] ③ When- ≤pH deviation value≤+ At the same time, the alkali metering pump maintains its current stroke or frequency to stably add alkali solution and ensure that the pH value remains stable within the optimal range.

[0034] Preferably, a qualified judgment threshold range is also preset to determine in real time whether the wastewater discharged from the ammonia stripping tower wastewater outlet is qualified, and to achieve wastewater diversion control in the following manner:

[0035] ① When the measured pH value is within the acceptable threshold range, the wastewater is deemed acceptable, and the discharged wastewater is fed into the equalization tank for subsequent treatment processes;

[0036] ② If the measured pH value is not within the acceptable threshold range, the wastewater is deemed unqualified and is immediately switched to the emergency tank.

[0037] Preferably, the control unit monitors the signal transmission quality of the pH sensor, the operating status of the alkali metering pump, and the parameter matching degree in real time. When any device failure is detected, it automatically switches to the backup pH sensor or the backup alkali metering pump and issues an audible and visual alarm.

[0038] The beneficial effects of this invention are as follows:

[0039] (1) The automatic alkali addition system of the present invention includes an alkali storage tank, a conveying unit, a pipeline unit, a detection unit, and a control unit, constructing a functional closed-loop, collaborative, and highly efficient automated treatment system. This system can completely eliminate the dependence on operator experience in traditional manual alkali addition, solving the core pain points such as lagging manual detection and adjustment, low accuracy, and high labor intensity. Through real-time data acquisition and dynamic control, it can effectively ensure that the pH value of coking wastewater after treatment can accurately match the ammonia nitrogen standard and the requirements of subsequent processes, significantly improving the automation level and operational reliability of the treatment process, and avoiding fluctuations in treatment effect caused by individual differences in manual operation.

[0040] (2) This invention uses straight-through stainless steel pipes without bends as pipe units, and the conveying unit is directly connected to the ammonia stripping tower inlet through the pipe unit. This completely eliminates the traditional pipe layout logic that is prone to blockage (such as S-shaped bends, high-positioned troughs, float flow meters, etc.). Through this straight-through structure without bends, the hidden dangers of slowed flow rate and crystal deposition caused by unnecessary bends are eliminated. At the same time, the stainless steel material has both alkali corrosion resistance and smooth surface characteristics. Combined with the high-speed flow field formed by the alkali metering pump, the pipe blockage problem caused by alkali crystallization and impurity deposition is eliminated from the source. This enables the system to operate continuously without blockage for a long time, completely saving the manpower, materials and downtime losses of the traditional system that requires pipe cleaning 1-2 times a week, and greatly reducing operation and maintenance costs and production interruption risks.

[0041] (3) The present invention features a dual-redundancy design with at least two pH sensors in the detection unit and at least two alkali metering pumps in the delivery unit. Combined with the real-time fault monitoring function of the control unit, this significantly improves the system's operational reliability and stability. The pH sensors are installed on the wastewater outlet pipe of the ammonia stripping tower, capturing the real-time pH value of the discharged wastewater and the pH value of the treatment environment inside the ammonia stripping tower. When a fault is detected in the pH sensor in use (e.g., signal interruption, measurement abnormality), the system automatically switches to another pH sensor, ensuring continuous and stable detection signals and providing reliable data support for the control unit. Simultaneously, the alkali metering pumps achieve precise control of the alkali output by adjusting the stroke or frequency. When a fault is detected in the alkali metering pump in use (e.g., abnormal pressure, parameter mismatch), another alkali metering pump can be immediately activated to avoid interruption of alkali dosing. Furthermore, the audible and visual alarm function in case of a fault promptly alerts staff for maintenance, minimizing fault handling time and effectively avoiding problems such as pH value loss and ammonia nitrogen exceeding standards due to equipment failure, ensuring the continuity of the treatment process.

[0042] (4) This invention uses the measured pH value at the outlet of the ammonia stripping tower wastewater as the core control indicator. Through a closed-loop control process of setting a target value, collecting measured values ​​in real time, performing PID algorithm calculations, and dynamically adjusting the dosage, it achieves fully automated and precise control of the alkali dosage throughout the entire process. The control unit continuously collects measured pH values ​​and dynamically corrects the dosage, enabling it to quickly respond to drastic fluctuations in the inflow volume (fluctuation range can reach ±30%) and acidity of the coking wastewater. This ensures that the wastewater pH value remains stable within the optimal range required by subsequent processes. This not only solves the shortcomings of traditional manual alkali addition, which cannot adapt to dynamic operating conditions, but also achieves precise on-demand alkali addition. It avoids equipment corrosion and decreased efficiency of subsequent processes caused by insufficient alkali addition, as well as alkali waste caused by excessive alkali addition, significantly enhancing the economy and adaptability of the treatment process.

[0043] (5) This invention sets an allowable deviation threshold. This makes the adjustment of alkali dosage more rational and stable. When the pH deviation exceeds the threshold, the alkali metering pump precisely adjusts the stroke or frequency according to the PID output ratio to ensure that the adjustment of the alkali dosage matches the magnitude of the deviation. This quickly corrects the deviation without causing new imbalances due to over-adjustment. When the deviation is within the threshold range, stable dosage is maintained to avoid frequent adjustments caused by small pH fluctuations, reducing equipment wear and energy waste. At the same time, it ensures that the pH value is always stable in the optimal range, providing stable and suitable water quality conditions for subsequent processes such as phenol removal and biochemical reactions, and further ensuring stable and compliant ammonia nitrogen discharge.

[0044] (6) The invention uses the measured pH value at the outlet of the ammonia stripping tower wastewater as the sole control input, which can directly anchor the final effect index of wastewater treatment without introducing multiple complex parameters such as ammonia nitrogen concentration and water flow rate. This not only simplifies the system's control logic and hardware configuration, avoiding calibration difficulties and error accumulation caused by multi-parameter coupling, but also directly maps the alkali addition effect through real-time feedback of the pH value at the outlet of the ammonia stripping tower wastewater, making the PID closed-loop control response more direct and the adjustment more precise.

[0045] Compared to other control schemes that require collecting multiple water quality or flow parameters for feedforward calculations or rely on indirect measurement signals, the "end-oriented" control logic of this invention does not require a preset fixed alkali addition flow rate. Even if there is a slight blockage in the internal pipeline (such as residual crystals in winter) or a flow meter failure, or fluctuations in flow or pressure in the intermediate links, or even a very slight change in the flow resistance of the pipeline (or other non-fatal failures), this invention can still achieve precise real-time control of pH value, fundamentally avoiding the adjustment deviation caused by the accumulation of intermediate parameter errors.

[0046] Meanwhile, this design can automatically adapt to fluctuations in influent water quality and quantity, greatly improving the system's self-adaptability, reducing the configuration of redundant sensors, flow meters and other equipment, lowering the risk of equipment failure and maintenance costs, completely avoiding the adjustment lag problem caused by indirect measurement, ensuring that the amount of alkali added is always precisely matched with the treatment needs, avoiding alkali waste, and ensuring the long-term stable and efficient operation of the system.

[0047] (7) This invention achieves automated control of wastewater diversion by pre-setting a qualified threshold range. When the measured pH value is within the qualified range, the wastewater automatically enters the equalization tank to connect with the subsequent treatment process; when the pH value is unqualified, it immediately switches to the emergency tank to prevent unqualified wastewater from entering the subsequent system and causing problems such as equipment corrosion and process disorder, further strengthening the defense line for effluent ammonia nitrogen compliance and reducing the operation and maintenance pressure and cost of subsequent treatment links. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the system of the present invention;

[0049] Figure 2 This is a schematic diagram of the process of the present invention;

[0050] Figure 3 This is a schematic diagram of a traditional system. Detailed Implementation

[0051] like Figures 1 to 3 As shown, an automatic alkali addition system for coking wastewater includes an alkali storage tank, a conveying unit, a pipeline unit, a detection unit, and a control unit.

[0052] The alkali storage tank is used to store the alkali solution to be added. Its outlet is connected to the conveying unit to provide a stable supply of alkali solution to the entire system, ensuring the continuous demand for alkali addition in the pretreatment stage of coking wastewater and ensuring the stability requirements of subsequent processes for alkali addition.

[0053] The delivery unit includes at least two alkali metering pumps. These pumps employ a redundant design, with one in operation and one as a backup, effectively mitigating the risk of system downtime due to single pump failure and ensuring uninterrupted alkali dosing. The metering pumps selected for this unit can be either Milton Roy Prominent Gamma / 4 (flow range 0-50 L / h, maximum operating pressure 1.6 MPa) or ProMinent Beta / 4 (flow range 0-100 L / h), featuring stroke or frequency adjustment capabilities to precisely regulate the alkali output according to the control unit's instructions. Specifically, the input end of the metering pump is connected to the outlet end of the alkali storage tank to draw alkali from the tank, while the output end seamlessly connects to the piping unit for stable alkali transport.

[0054] The piping unit utilizes straight-through stainless steel pipes without bends to achieve high-speed, blockage-free transport of alkali solution. In traditional alkali dosing systems, S-shaped bends reduce the alkali solution flow rate, leading to NaOH crystallization and deposition. When elevated tanks rely on gravity to transport alkali solution, clumps settled at the bottom of the tank can easily flow into the pipes, reducing the pipe diameter and even causing blockages. Simultaneously, the installation of float flowmeters increases fluid flow resistance, and their internal structure easily becomes a node for crystal deposition, further exacerbating the risk of blockage. Pipeline blockage not only causes fluctuations or interruptions in alkali solution dosing but also leads to unstable fluid conditions in the wastewater outlet pipe of the ammonia stripping tower, distorting pH adjustment and failing to meet the pH control requirements of subsequent processes.

[0055] In this embodiment, the piping unit uses a DN32 straight-through stainless steel pipe without bends, completely eliminating the S-shaped bends in traditional pipes and retaining only the necessary functional connection pipes, thus eliminating all unnecessary bends. One end of the pipe is connected to the outlet of the metering pump of the conveying unit, and the other end is directly connected to the inlet of the ammonia stripping tower. The pushing force of the metering pump keeps the alkali solution flowing at a high speed, avoiding blockage problems caused by NaOH crystallization or impurity deposition from the source.

[0056] The detection unit includes at least two pH sensors (i.e., online pH meters). These two pH sensors employ a redundant design, with one sensor in operation and the other as a backup. They are installed on the wastewater outlet pipe of the ammonia stripping tower to collect real-time pH signals of the coking wastewater's reaction environment within the ammonia stripping tower and the discharged wastewater. The collected signals are transmitted to the control unit in real-time via a 4-20mA signal line. Optional models of the pH sensors are the Metler Thornton InPro 3250i or Emerson Rosemount 1056. In this embodiment, the measured pH value is transmitted to the control unit once per second to provide accurate feedback data.

[0057] The control unit receives the pH signal transmitted by the detection unit and outputs control commands to the delivery unit to achieve real-time dynamic adjustment of the alkali dosage. Specifically, the control unit in this embodiment adopts the Yokogawa CENTUM VP series DCS system (i.e., Yokogawa Electric CENTUM VP Distributed Control System). This system is configured with PID control function blocks, possessing powerful PID algorithm calculation capabilities and equipment monitoring functions. The DCS system establishes communication connections with the two metering pumps of the delivery unit, the two pH sensors of the detection unit, and the level gauge of the alkali storage tank through signal lines, integrating functions such as pH setting, data acquisition, algorithm calculation, command output, and fault alarm. The control screen can display various operating parameters in real time.

[0058] like Figure 1As shown, it also includes "residual ammonia water" and a "residual ammonia water pump." The residual ammonia water pump is responsible for transporting the residual ammonia water to the ammonia stripping tower for spraying. Because coking wastewater contains various recalcitrant impurities such as phenols, cyanides, and suspended solids, these impurities easily evaporate along with the ammonia vapor during the ammonia stripping process, affecting the purity of the final product. By spraying the residual ammonia water into the ammonia stripping tower, a highly efficient washing process is formed, thoroughly washing away impurities such as phenols and suspended solids from the ammonia vapor. This ensures that the concentrated ammonia water or ammonium sulfate product obtained after subsequent condensation and absorption or chemical reaction by the fractionator / saturator meets the required purity. Simultaneously, the residual ammonia water sprayed into the ammonia stripping tower itself contains ammonia components. After participating in the evaporation process within the tower, it enters the subsequent recovery system along with the ammonia vapor and is ultimately recovered into the ammonia water product, achieving the recycling of ammonia resources. This not only improves the product recovery rate but also reduces the ineffective discharge of wastewater.

[0059] The automatic control method for alkali addition using the above-mentioned automatic alkali addition system for coking wastewater includes the following steps:

[0060] 1) Based on the ammonia nitrogen compliance requirements for coking wastewater and the optimal pH conditions for subsequent treatment processes (ammonia stripping, biochemical treatment, coagulation and sedimentation, etc.), and combined with process test data, a target pH value is set in the DCS system of the control unit. In actual production, the adjustable pH range is 8.0-9.5, for the following reasons:

[0061] Firstly, the ammonia stripping process relies on an alkaline environment to remove ammonium ions from the wastewater. ) is converted into free ammonia ( The ammonia is then removed by stripping. When the pH value is below 8.0, the ammonium ion conversion rate decreases significantly, the ammonia stripping efficiency decreases, resulting in excessive ammonia nitrogen concentration in the effluent and reducing the ammonia recovery output. When the pH value is above 9.5, although the ammonia removal efficiency can be improved, it will cause a surge in alkali consumption and may lead to the risk of alkali corrosion of subsequent pipelines and equipment, increasing operation and maintenance costs.

[0062] Secondly, subsequent biological treatment units (such as A / O, SBR and other processes) rely on the nitrification and denitrification of microorganisms to degrade pollutants. Too low or too high pH values ​​will inhibit the metabolic activity of microorganisms, resulting in a 30%-50% decrease in ammonia nitrogen conversion rate, making it difficult to ensure that the ammonia nitrogen in the subsequent effluent meets the standards.

[0063] Thirdly, in subsequent physicochemical treatment, iron and aluminum salts are commonly used as coagulants. Their hydrolysis products exhibit optimal flocculation performance within the pH range of 8.0-9.0, enabling suspended solids (SS) and chemical oxygen demand (COD) removal rates to reach over 85%. If the pH deviates from this range, the coagulant is prone to forming ineffective complexes, resulting in loose flocs, poor settling performance, and consequently, increased effluent turbidity, increased sludge production, and significantly increased operating load on subsequent filtration units.

[0064] In summary, the target pH value is set to 8.5 in this embodiment. This value can maximize the compatibility with each subsequent treatment process and ensure the overall treatment efficiency and the stability of the effluent quality.

[0065] 2) After system startup, the preset startup sequence is followed: first, the outlet valve of the alkali storage tank is opened; then, the alkali metering pump is started; finally, the PID control mode is activated. Subsequently, the pH sensor is used to collect the actual pH value of the wastewater outlet of the ammonia stripping tower in real time. The sampling frequency is consistent with the sampling frequency of the DCS system, which is once per second. The pH sensor converts the collected pH value signal into a standard 4-20mA electrical signal and transmits it to the DCS system in real time through the signal line. The DCS system filters the signal to remove interference signals and ensure the accuracy of the measured pH value.

[0066] 3) After receiving the measured pH value, the DCS system uses a PID algorithm to obtain a control signal for adjusting the stroke or frequency of the alkali metering pump based on the deviation between the measured pH value and the target pH value. Specific steps include:

[0067] 3-1) Calculate the pH deviation value based on the measured pH value and the pH target value, wherein the pH deviation value = pH target value - pH measured value;

[0068] 3-2) The integrated control output value is obtained according to the following formula. After the calculation is completed, the DCS system converts the integrated control output value into a control signal recognizable by the metering pump (corresponding to stroke or frequency adjustment command). The formula for calculating the integrated control output value is:

[0069]

[0070] In the formula, This is the proportionality coefficient. This is the pH deviation value. The integral coefficient is... The differential coefficient. In this embodiment, the proportional coefficient in the PID algorithm is set. The integral coefficient is 2.0. The differential coefficient is 0.1. The value is 0.05. In practical applications, the above parameters need to be tuned and optimized on-site to adapt to the dynamic fluctuations of water quality and quantity under actual working conditions.

[0071] 4) The delivery unit adjusts the alkali dosage in real time based on the control signal obtained in step 3). To avoid frequent adjustments of the metering pump due to minor fluctuations and to improve system stability and economy, a permissible deviation threshold is preset. This is used to define the stable pH range. In this embodiment, the allowable deviation threshold is... Units. The specific method for adjusting the amount of alkali solution added is as follows:

[0072] ① When pH deviation value > + (i.e., pH deviation value > +) When the measured pH value is <8.4, the alkali metering pump increases its stroke or frequency, and the alkali dosage is increased proportionally to the PID output. For example, when the measured pH value is 7.5 (lower than the target pH value of 8.5), the DCS PID controller calculates the pH deviation value. The output control signal increases the stroke of the metering pump to 80% to quickly replenish the alkali solution and correct the acid deviation.

[0073] ② When the pH deviation value is <- (i.e., pH deviation value < - When the pH value is greater than 8.6, the alkali metering pump should reduce its stroke or frequency and reduce the amount of alkali added according to the PID output ratio to avoid excessive alkali leading to excessively high pH.

[0074] ③ When- ≤pH deviation value≤+ (- ≤pH deviation value≤+ When the pH value is between 8.4 and 8.6, the alkali metering pump should maintain its current stroke or frequency to steadily add alkali solution and ensure that the pH value remains stable within the optimal range.

[0075] 5) The DCS system of the control unit continuously collects the measured pH value and repeats steps 2) to 4), that is, repeats the closed-loop process of "signal acquisition - deviation calculation - PID calculation - command transmission" once per second to realize real-time dynamic correction of the alkali dosage. For example, when the measured pH value is 7.5, after 2-3 minutes of adjustment, the pH value rises to 8.5 and stabilizes in the range of 8.4-8.6.

[0076] Meanwhile, the system has a preset acceptable threshold range (8-9.5) to determine in real time whether the pH value of the wastewater discharged from the ammonia stripping tower is acceptable, and simultaneously implements wastewater diversion control in the following manner:

[0077] ① When the measured pH value is within the acceptable threshold range, the wastewater is deemed acceptable and is introduced into the equalization tank (at this time, the valve at the input end of the equalization tank is open and the valve at the input end of the emergency tank is closed) to enter the subsequent oil removal, phenol removal, and biological treatment processes.

[0078] ② If the measured pH value is not within the acceptable threshold range, the wastewater is deemed unqualified and is immediately switched to the emergency tank (at this time, the valve at the input end of the equalization tank is closed, and the valve at the input end of the emergency tank is opened) to prevent unqualified wastewater from entering the subsequent treatment system and affecting subsequent processes.

[0079] The control unit synchronously monitors in real time the signal transmission quality of the pH sensor (e.g., whether the signal is interrupted or fluctuates abnormally), the operating status of the alkali metering pump (e.g., whether the pump pressure and flow rate match), and the parameter matching degree. The specific fault handling mechanism is as follows:

[0080] ① When a fault is detected in the pH sensor in use, the system automatically switches to the backup sensor to ensure continuous detection signal and avoid uncontrolled regulation due to data interruption;

[0081] ② When a fault is detected in the main alkali metering pump, the system immediately shuts down the main pump and starts the standby pump to ensure that the alkali addition is uninterrupted and to prevent the ammonia stripping reaction from stopping due to the alkali supply interruption;

[0082] ③ When a fault occurs, the system will simultaneously issue an audible and visual alarm, and the alarm information will be recorded in the DCS log, which will help staff to quickly locate and repair the fault, minimize the fault handling time, and reduce the risk of pH runaway.

[0083] When the system is shut down, it is necessary to follow the preset shutdown sequence: first exit the PID automatic mode, stop the alkali metering pump, and after the residual alkali in the pipeline is drained, close the outlet valve of the alkali storage tank to prevent residual alkali crystallization from clogging the pipeline and to ensure stable operation of the system when it is started up next time.

[0084] The above-mentioned automatic alkali addition system and method underwent long-term (12 months) operation testing, with continuous tracking and recording of system operating parameters, treatment effects, and cost data. The results are as follows:

[0085] In terms of operational stability, this invention achieves high-speed direct delivery of alkali solution through a bend-free stainless steel pipe design, completely solving the problem of easy blockage in traditional S-shaped bend pipes. It has successfully achieved 12 consecutive months of blockage-free operation without the need for any pipe dredging work, effectively solving the industry pain point that traditional systems require 1-2 dredging operations per week. At the same time, it ensures that the pH value of the wastewater discharged from the ammonia stripping tower always meets the process requirements.

[0086] In terms of economic benefits, this invention achieves on-demand addition of alkali solution through precise PID control. Compared with the traditional manual mode, it can reduce the ineffective loss of 10-20 tons of alkali solution per year, reducing direct economic losses by 50,000-100,000 yuan. At the same time, it completely eliminates the labor, materials and downtime losses of pipeline dredging, resulting in a total annual cost saving of hundreds of thousands of yuan, with significant economic benefits.

[0087] In terms of adaptability, traditional alkali addition systems are poorly adapted to fluctuations in influent flow and water quality. When the influent flow changes by more than ±20%, the pH value is difficult to maintain stability and cannot meet the requirements of subsequent processes. In contrast, this invention employs a "end-to-end" closed-loop control strategy, eliminating the need for fixed flow settings. Even under conditions where influent flow fluctuations exceed ±30% or ammonia concentration changes significantly, the alkali addition rate can be quickly and adaptively adjusted via a PID algorithm, ensuring pH control accuracy remains within ±0.1% error. The system's anti-interference capability and overall stability are significantly superior to traditional solutions. Furthermore, the system is equipped with a backup pH sensor and a backup alkali metering pump, forming a dual-redundancy design. During 12 months of continuous operation, it successfully handled sudden equipment failures, automatically switching to backup equipment and issuing audible and visual alarms to ensure uninterrupted and stable system operation, further enhancing system reliability.

[0088] In summary, this invention, through its minimalist anti-clogging physical structure, precise closed-loop intelligent control strategy (single pH feedback PID regulation), and dual-redundant reliable design, not only enables continuous operation of coking wastewater without clogging and precise pH control to meet the needs of subsequent treatment processes, but also significantly improves the system's adaptability to fluctuations in influent water quality and quantity, and greatly reduces alkali consumption and operation and maintenance costs.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. An automatic caustic addition system for coking wastewater, characterized by, It includes an alkali storage tank, a conveying unit, a piping unit, a detection unit, and a control unit; Alkali storage tank, used to store alkali solution to be added; The conveying unit is used to extract alkali from the alkali storage tank and precisely adjust the output of alkali according to the instructions of the control unit. Piping unit for clogging-free delivery of alkali solution; The detection unit is used to collect the pH value signal of coking wastewater in real time during the ammonia stripping process and transmit it to the control unit. The control unit receives signals from the detection unit and outputs instructions to the delivery unit to achieve real-time dynamic adjustment of the alkali addition amount.

2. The automatic alkali addition system according to claim 1, characterized in that, The pipe unit is a straight stainless steel pipe without bends.

3. The automatic alkali addition system according to claim 1, characterized in that, The detection unit includes at least two pH sensors, which are installed on the wastewater outlet pipe of the ammonia stripping tower.

4. The automatic alkali addition system according to claim 1, characterized in that, The delivery unit includes at least two alkali metering pumps, which can precisely control the output of alkali solution by adjusting the stroke or frequency.

5. A method for automatically adding alkali to coking wastewater using the automatic alkali addition system described in any one of claims 1-4, characterized in that, Includes the following steps: 1) Based on the ammonia nitrogen compliance requirements of coking wastewater and the optimal pH conditions of subsequent treatment processes, and combined with process test data, set the target pH value in the control unit; 2) The pH value at the outlet of the ammonia stripping tower wastewater is collected in real time using a pH sensor and transmitted to the control unit in real time; 3) The control unit uses a PID algorithm to obtain a control signal for adjusting the stroke or frequency of the alkali metering pump based on the measured pH value and the target pH value. 4) The conveying unit adjusts the amount of alkali solution added in real time according to the control signal obtained in step 3); 5) The control unit continuously collects the measured pH value and repeats steps 2) to 4) to dynamically adjust the amount of alkali solution added in real time.

6. The method according to claim 5, characterized in that, Step 3), the steps for obtaining the control signal include: 3-1) Calculate the pH deviation value based on the measured pH value and the pH target value, wherein the pH deviation value = pH target value - pH measured value; 3-2) Obtain the integrated control output value according to the following formula, and convert it into a control signal. The formula for calculating the integrated control output value is: ； In the formula, This is the proportionality coefficient. This is the pH deviation value. The integral coefficient is... is the differential coefficient.

7. The method according to claim 5, characterized in that, In step 4), a permissible deviation threshold is set. The method for adjusting the alkali dosage in real time according to the control signal is as follows: ① When pH deviation value > + At the same time, the alkali metering pump increases its stroke or frequency, and increases the amount of alkali added according to the PID output ratio; ② When the pH deviation value is <- When the alkali metering pump reduces its stroke or frequency, the amount of alkali added is reduced according to the PID output ratio. ③ When- ≤pH deviation value≤+ At the same time, the alkali metering pump maintains its current stroke or frequency to stably add alkali solution and ensure that the pH value remains stable within the optimal range.

8. The method according to claim 5, characterized in that, A pre-set pass / fail threshold range is also used to determine in real time whether the wastewater discharged from the ammonia stripping tower is up to standard, and to implement wastewater diversion control in the following manner: ① When the measured pH value is within the acceptable threshold range, the wastewater is deemed acceptable, and the discharged wastewater is fed into the equalization tank for subsequent treatment processes; ② If the measured pH value is not within the acceptable threshold range, the wastewater is deemed unqualified and is immediately switched to the emergency tank.

9. The method according to claim 5, characterized in that, The control unit monitors the signal transmission quality of the pH sensor, the operating status of the alkali metering pump, and the parameter matching degree in real time. When any equipment failure is detected, it automatically switches to the backup pH sensor or the backup alkali metering pump and issues an audible and visual alarm.

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