A high-efficiency constant-temperature heat exchange process for strong acid electrolyte gradient

Abstract

The application discloses a kind of strong acid electrolyte gradient high-efficiency constant-temperature heat exchange processes, including steam decompression, primary heating and secondary heating.The application releases steam energy in two stages: primary heating uses latent heat of decompressed steam to heat process water to 80 DEG C, and secondary heating uses 80 DEG C hot water to heat electrolyte through titanium plate heat exchanger.The application uses gas-liquid mixer to inject acid mixed gas into electrolyte flow by negative pressure generated by vortex propeller, forms gas-liquid two-phase flow, strengthens heat transfer process, improves heating speed and primary heat exchange temperature rise, and produces gas washing effect to greatly reduce acid side fouling and blockage of heat exchanger, and reduces cleaning cost;It also adopts control system and optimization algorithm design to realize accurate control, low energy consumption and high stability process control method, with emergency handling capacity and predictive maintenance function, solves efficiency, corrosion, fouling and acid mist recovery and other key problems in strong acid electrolyte heating.

Description

Technical Field

[0001] This invention relates to the field of acidic wet electrolysis technology, and in particular to a gradient high-efficiency isothermal heat exchange process for strong acid electrolytes. Background Technology

[0002] In industrial processes such as electrolysis, electroplating, and hydrometallurgy, it is often necessary to heat strong acid electrolytes (such as sulfuric acid, hydrochloric acid, and mixed acids) to maintain optimal reaction rates and process stability. However, the high corrosiveness of strong acid media poses a severe challenge to the safety and durability of heating solutions.

[0003] Currently, there are two main methods for heating strong acid electrolytes:

[0004] 1) Direct steam heating: Steam is directly introduced into the electrolyte tank. Although this method has high heat exchange efficiency and low equipment investment, it has fatal flaws: high temperature and high speed steam will severely impact and corrode the injector and pipeline, resulting in a very short equipment life; at the same time, steam condensate will dilute the electrolyte, affecting the process concentration, requiring frequent acid replenishment, increasing the complexity of operation and posing safety hazards.

[0005] 2) Indirect heat exchanger heating: Plate or tube heat exchangers are used to indirectly heat the electrolyte using hot water or steam as the heat medium.

[0006] While this method avoids the dilution problem, it still faces the following challenges:

[0007] ① Low heat exchange efficiency and scaling issues: Strong acid electrolytes have high viscosity and easily form a stable laminar thermal boundary layer on the heat exchange wall, which is the main resistance to heat transfer. This leads to low heat exchange efficiency, often requiring higher heat medium temperatures or larger heat exchange areas. In addition, trace impurities that may be contained in the acid can easily deposit and form scale on the wall, further reducing efficiency and requiring frequent shutdowns for cleaning, affecting continuous production.

[0008] ② Material Costs and Corrosion Risks: To resist acid corrosion, high-grade corrosion-resistant materials (such as titanium, Hastelloy, tantalum, etc.) must be used in the contact parts of the heat exchanger, which is very expensive. Once the heat exchanger is damaged and leaks, the expensive heat medium (such as steam) or softened water will enter the electrolysis system, or acid will leak out, causing significant economic losses and safety accidents.

[0009] Furthermore, the electrolysis process typically generates acid mist, which, if directly emitted, can corrode factory equipment, harm personnel health, and pollute the environment. Current acid mist treatment methods mostly employ independent alkaline spray towers, a "end-of-pipe" treatment approach that consumes chemicals and generates wastewater, failing to achieve resource recycling.

[0010] ③ Difficult and low-precision heat exchange temperature control: Due to the use of heat transfer wall heating, heat control often relies solely on production experience, changing the flow rate or velocity of the heating medium or the area of ​​the heat transfer wall. This control method often results in overheating or overcooling, and the control lag effect is very prominent, leading to defects such as high energy consumption, inaccurate temperature and large fluctuations. At the same time, it lacks effective emergency handling capabilities and predictive maintenance functions when facing various emergency situations (such as sudden drop in heating efficiency, equipment extreme conditions, etc.) and process risks.

[0011] Therefore, there is an urgent need in this field for a new process for heating strong acid electrolytes that can take into account efficient heat exchange, long-term equipment safety, low-maintenance operation, resource recycling, and intelligent operation. Summary of the Invention

[0012] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-efficiency isothermal heat exchange process for strong acid electrolyte gradient.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A gradient high-efficiency isothermal heat exchange process for strong acid electrolytes includes the following steps:

[0015] S1, Steam pressure reduction

[0016] The high-pressure steam generated by the steam boiler is depressurized by a pressure reducer to a pressure of 3-5 Bar. For example, under rated operating conditions, the steam pressure is reduced from the initial pressure of 12.5 Bar to below 3 Bar, and the saturated steam flow rate is reduced to below 3 t / h. The steam pressure is monitored in real time by a pressure sensor (PT), and the main control unit dynamically adjusts the opening of the pressure reducing valve according to the set value (such as 3 Bar) to ensure that the pressure fluctuation range is ≤ ±0.2 Bar.

[0017] S2, Level 1 heating

[0018] After depressurization, steam is injected below the liquid surface of the insulated water tank through a Venturi ejector, heating the water in the tank through mass transfer. The latent heat of the depressurized steam (approximately 3 bar, approximately 134°C) is used to heat a large amount of process water from 60°C to 80°C. This is a phase change heat transfer process with extremely high efficiency, converting the high-grade heat energy of steam into the low-grade heat energy of hot water for storage. The insulated water tank is equipped with multiple temperature sensors (TS), and the main control unit adjusts the opening of the steam solenoid valve through a PID algorithm to keep the water temperature constant at 80°C (allowable deviation ±0.5°C). The water in the insulated water tank is continuously supplied through the boiler feed water softening tank. The 100±3°C humid air generated above the liquid surface mixes with the acid mist from the electrolysis system in the gas mixing chamber. The temperature of the mixed gas is monitored by the TIC, and the mixing ratio of acid mist and humid air is controlled by a proportional valve.

[0019] S3, Secondary Heating

[0020] The heating hydraulic module pumps 80℃ hot water into the titanium plate heat exchanger to exchange heat with the electrolyte. During the heat exchange process, the hot water temperature drops from 80℃ to 60℃ and is then reintroduced into the insulated water tank for reheating. Excess hot water is returned to the boiler for reheating, thus realizing the recycling of the solution, reducing heat loss, and ensuring efficient energy circulation. The strong acid electrolyte is pressurized from the electrolyte tank of the electrolysis system through the acid hydraulic module, and then mixed with the acid-gas mixture through the gas-liquid mixer to obtain a gaseous electrolyte at 35±1℃. After heat exchange in the titanium plate heat exchanger, it becomes an electrolyte at 53±2℃ and is returned to the electrolysis system for continued use. This is a liquid-liquid sensible heat exchange process that is gentle and controllable.

[0021] Preferably, the heating process of S3 adopts the following control strategy: Flow coordinated control: The flow rate of hot water and electrolyte is monitored in real time by the flow switch FS, and the main unit dynamically adjusts the pump frequency to ensure that the flow ratio of water side to acid side is maintained at 1.2-1.5:1; Temperature cascade control: The main circuit uses the electrolyte outlet temperature (target 53±2℃) as the reference, and the secondary circuit uses the hot water inlet temperature (80℃) as feedback, and adjusts the steam supply through PID algorithm; Emergency mode: When the electrolyte temperature is lower than 35℃, the flow rate of humid air is automatically increased to raise the temperature of the gas-carrying electrolyte to 45-50℃ for direct reuse.

[0022] Preferably, the S3 control strategy is implemented through a control system, which includes the following modules: a control host: an industrial PLC (such as Siemens S7-1200) paired with an HMI touch screen, integrating analog input / output modules to receive signals from various sensors; actuators: steam solenoid valves, water pump frequency converters, and pneumatic regulating valves, all supporting 4-20mA signal control; a network architecture for remote cloud control can also be added later: connecting field instruments via the PROFIBUS-DP protocol to support remote cloud data monitoring.

[0023] The implementing mechanism specifically includes the following components:

[0024] The heating hydraulic module consists of two parallel delivery pipes, each of which is equipped with a shut-off valve and a water pump, and the water pump is equipped with a flow switch FS.

[0025] The acid hydraulic module includes a shut-off valve and an acid pump, with the pump equipped with a flow switch FS; the high-pressure steam pipeline in S2 is equipped with a shut-off valve and a steam solenoid valve; the outlet pipe section and electrolyte outlet pipe section of the titanium plate heat exchanger in S3 are equipped with a pressure gauge PG and a temperature display controller TIC, the inlet pipe section of the titanium plate heat exchanger is equipped with a pressure gauge PG, a temperature sensor TS is located below the liquid level in the insulated water tank, and both the electrolyte inlet pipe section and the electrolyte outlet pipe section of the titanium plate heat exchanger are equipped with solenoid valves; the control host also controls the flow valves of the heating hydraulic module and the acid hydraulic module.

[0026] Furthermore, the control system includes the following algorithm model:

[0027] (1) Multivariate Predictive Control (MPC) Model

[0028] Establish a dynamic mathematical model of the heat exchange system, with steam pressure P steam Hot water flow rate F water Electrolyte inlet temperature T in-acid As the input variable, the electrolyte outlet temperature T out (t) is the target variable: T out (t)=f(P steam ,F water ,T in-acid )+ε;

[0029] Where ε is the error term, containing all factors that cause the model's predicted value f(P) to be affected. steam ,F water ,T in-acid ) and the actual measured value T out Factors that differ between (t) are used; a rolling optimization algorithm is adopted to predict the temperature trend for the next 5 minutes every 30 seconds and adjust the actuator action in advance;

[0030] (2) Adaptive PID parameter tuning

[0031] To address the nonlinear characteristics of the heat exchanger, a fuzzy adaptive PID controller is designed: the deviation e and the rate of change of deviation e c Divide the area into zones and apply a strong proportional effect as needed (proportioning factor K). p ), Integral action (I) i ) or differential action (D d This enables the system to automatically adjust its control parameters (P, I, D) when faced with changes in system characteristics or significant disturbances, i.e., parameter self-tuning, and always maintain optimal control performance;

[0032] (3) Energy efficiency optimization algorithm

[0033] Real-time calculation of system thermal efficiency: ;

[0034] Where η is the energy utilization efficiency (or thermal efficiency), representing the effectiveness of acid in absorbing heat from steam, expressed as %; Q acid Q represents the heat absorbed by the acid, usually measured in J or kJ, which is the energy gained by the acid during the heat exchange process. steam F represents the heat released by steam, usually measured in J or kJ, which is the total energy provided by steam during heat exchange; acid c is the mass flow rate of acid, expressed in kg / s or kg / h, representing the mass of acid flowing through per unit time; p T is the isobaric specific heat capacity of an acid, usually expressed in J / (kg·℃) or kJ / (kg·℃). It refers to the amount of heat required to raise the temperature of a unit mass of acid by 1℃ under isobaric conditions. out-acid T represents the outlet temperature of the acid, expressed in °C, i.e., the temperature of the acid after heat exchange. in-acid F represents the inlet temperature of the acid, expressed in °C, i.e., the temperature of the acid before heat exchange; steam The mass flow rate of steam, expressed in kg / s or kg / h, represents the mass of steam flowing through per unit time; h steam This is the latent heat of vaporization of steam, measured in J / kg or kJ / kg. It refers to the heat released when a unit mass of steam changes from a gaseous state to a liquid state under constant temperature and pressure (if the steam releases heat through condensation, this parameter describes the latent heat of that process); it is continuously calculated and recorded, and the control system will draw daily / weekly energy efficiency trend charts.

[0035] Set adaptive threshold: If η is lower than the set threshold (e.g., 85%), a cleaning reminder will be automatically triggered or the gas-liquid mixing ratio will be adjusted. The threshold for cleaning reminders is not fixed. The algorithm will learn the historical efficiency values ​​of the system under optimal conditions to form a dynamic and personalized efficiency benchmark. An alarm will only be triggered if the current efficiency is consistently lower than the benchmark value by a certain margin to avoid false alarms. When efficiency decreases, the system can not only issue an alarm but also provide a preliminary diagnosis based on correlation analysis, such as "The decrease in efficiency may be related to the gas-liquid mixing ratio deviating from the optimal value. It is recommended to check / automatically adjust."

[0036] Predictive maintenance models can be added later:

[0037] Feature extraction: Continuously monitor the slow changing trends of the pressure difference ΔP and heat transfer coefficient U between the acid and water sides of the heat exchanger; Health assessment: Based on these features, a "health index" model is trained using machine learning algorithms (such as regression models or simple neural networks). When the health index is lower than a predetermined threshold, the system will issue an early warning, such as "the heat exchanger is expected to need cleaning in 15 days", thereby achieving planned shutdown maintenance and avoiding unplanned shutdowns.

[0038] Furthermore, the mechanism of the rolling optimization algorithm is as follows:

[0039] ① State estimation: Every 30 seconds, the control system uses the latest sensor data to estimate the internal state of the model (such as the temperature of the heat exchanger wall) in real time through a Kalman filter to correct the model error. ② Prediction and optimization: Based on the currently estimated state, the model predicts the change trajectory of the key parameters of the system within the next 5 - 10 minutes; the optimizer calculates a series of optimal future control actions, such as the change in the opening of the steam valve and the frequency of the water pump, with the main goal of "stabilizing the electrolyte outlet temperature at the set value (53°C)" and the economic goal of "minimizing steam consumption". ③ Implementation and feedback: Only the first calculated control action is implemented, and then the entire process is repeated in the next sampling period. This "rolling optimization" mechanism enables the system to continuously respond to various disturbances.

[0040] Furthermore, the adaptive PID parameter tuning includes the following process:

[0041] Divide the temperature deviation |e| and the deviation change rate |e c | into three fuzzy sets of "large, medium, and small". e c is the change rate between the temperature deviations e detected twice adjacent times. The "large" of |e| is the set where > 5°C, the "medium" of |e| is the set where 1 - 5°C, and the "small" of |e| is the set where < 1°C; the "large" of |e c | is the set where > 10%, the "medium" of |e c | is the set where 1 - 10%, and the "small" of |e c | is the set where < 1%; where e = T setpoint -T actual , T setpoint is the set temperature value. For example, the ideal process requires the electrolyte outlet temperature to be 53°C; T actual is the actual temperature value, that is, the electrolyte outlet temperature value measured in real time by the temperature sensor TIC;

[0042] When |e| ∈ "large", a strong proportional action is adopted, that is, K p is increased significantly to quickly eliminate the deviation, ignoring the integral (I i = 0) and derivative (D d ) actions to prevent integral saturation and system oscillation; when |e| ∈ "medium" and |e c | ∈ "small", then K p is reduced, and an appropriate integral action (I i ) is introduced to smoothly eliminate the static error; when |e| ∈ "small" and |e c | ∈ "large", then the derivative action (D d ) is increased to suppress overshoot and improve stability; anti-integral saturation: When the actuator (such as the steam valve) has reached the limit position (fully open or fully closed) and the deviation has not been eliminated, the algorithm pauses the integral action to prevent large overshoot when recovering.

[0043] Furthermore, the control system also provides the following multi-layered safety protection measures:

[0044] Level 1 equipment: The frequency converters of critical equipment (such as water pumps and acid pumps) have built-in overcurrent and overload protection;

[0045] Secondary process layer: Low flow interlock: If any flow switch FS detects that the flow rate is lower than 50% of the rated value (more stringent setting), an emergency shutdown sequence is immediately triggered: the steam solenoid valve is shut off, the relevant pump is stopped, and the emergency cooling system is activated; High temperature interlock: If the electrolyte outlet temperature exceeds 60℃ or the insulated water tank temperature exceeds 90℃, the heat source is immediately shut off; Pressure interlock: If the steam pressure exceeds the safety limit or the pressure difference ΔP of the titanium plate heat exchanger is continuously higher than 0.15MPa, the system alarms and automatically reduces the load or shuts down;

[0046] Level 3 system layer: The HIM panel of the control host is equipped with a one-button emergency stop button. All interlocking events are recorded in detail, including the trigger time, trigger point, and action result, for post-event analysis.

[0047] Furthermore, security measures also include the following intelligent emergency modes:

[0048] ① If the electrolyte flow rate drops sharply (FS detects flow rate < 70% of rated value), immediately cut off the steam supply and activate emergency cooling; ② When the pressure difference ΔP across the titanium plate heat exchanger exceeds 0.1 MPa, a blockage risk is assessed, the flow rate is automatically reduced, and an alarm is triggered; ③ When the control system detects that the acid-side inlet temperature of the titanium plate heat exchanger remains below 35°C, it automatically determines that the primary heating is insufficient. At this time, the system will perform the following operations: gradually open the humid air inlet proportional valve of the gas mixing chamber; simultaneously fine-tune the bypass valve of the gas-liquid mixer to allow more high-temperature humid air to mix with the electrolyte for preheating; ④ If the temperature still cannot be increased within the set time, an alarm "Electrolyte initial temperature needs to be checked" will be sent to the central control room, and it may be recommended to reduce the production load to maintain a stable outlet temperature. This control system integrates advanced process control, energy efficiency management, and predictive maintenance, significantly improving the technical level and economy of the entire process.

[0049] Preferably, the gas-liquid mixer includes a vortex chamber, which consists of a lower circular vortex zone and an upper inverted cone-shaped air inlet zone. A vortex propeller is connected to the center of the vortex zone via a rotating shaft. An electrolyte inlet pipe and an electrolyte outlet pipe are tangentially connected to the outer ring of the vortex zone. An air inlet pipe is connected to the top of the air inlet zone. The vortex propeller is inclined at 30-45°. The pressurized electrolyte drives the vortex propeller to rotate, creating a vacuum in the air inlet zone. This allows the acid mixture in the gas mixing chamber to be introduced into the vortex chamber and mixed with the electrolyte to obtain a gas-laden electrolyte. The gas-liquid volume ratio in the gas-laden electrolyte is 0.05-0.08:1. The acid components in the acid mixture are redissolved in the water, thereby reducing the amount of acid mist in the electrolysis system. The acid mixture and electrolyte are pre-mixed for mass and heat transfer. At the same time, the gaseous electrolyte enhances mixing and turbulence: the introduction of air forms a gas-liquid two-phase flow, which greatly enhances the turbulence in the channel, destroys the thermal boundary layer on the acid side, and significantly improves the heat transfer coefficient of the titanium plate wall to the acid. In addition, the air flow helps prevent solid deposition or scouring of the channel wall, and may have a purging / cleaning effect, reducing the cleaning frequency of the acid side channel of the titanium plate heat exchanger from 5-7 times per month without gaseous electrolyte to 1-2 times per month with gaseous electrolyte, significantly reducing downtime costs and water consumption.

[0050] Preferably, the electrolyte outlet pipe of the gas-liquid mixer is also directly connected to the electrolysis system via a pipeline. When the temperature of the gaseous electrolyte in the outlet pipe reaches 45-50℃, it can be directly introduced into the electrolysis system for emergency use. If problems occur during electrolyte transportation or preparation, causing the electrolysis operation to stall, the acid mist inlet of the gas mixing chamber can be closed, and the flow rate of humid air can be increased to raise the temperature of the gaseous electrolyte. The humid air inlet pipe, acid mist inlet pipe, and outlet pipe of the gas mixing chamber are all equipped with one-way valves to prevent the acid mixture from rushing into the insulated water tank and the electrolysis system.

[0051] Preferably, the steam and hot water conveying pipelines in S1, S2 and S3 are made of seamless steel pipes, and the strong acid electrolyte pipeline in S3 is made of PP material.

[0052] The electrolysis system is also connected to an electrolyte replenishment tank via pipeline for replenishing the electrolyte.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] 1. This invention releases steam energy in two stages. The first stage of heating utilizes the latent heat of the depressurized steam to heat a large volume of process water from 60°C to 80°C. This is a highly efficient phase-change heat transfer process, converting the high-grade heat energy of the steam into the low-grade heat energy of the hot water for storage. The second stage of heating uses 80°C hot water to heat the electrolyte via a titanium plate heat exchanger. This is a gentle and controllable liquid-liquid sensible heat exchange process. Through gradient utilization of steam heat energy and closed-loop circulation of hot water, energy is recovered and utilized to the maximum extent, significantly reducing steam consumption and operating costs.

[0055] 2. To avoid corrosion of heat exchangers by existing strong acid electrolytes, this invention specifically studies a gas-liquid mixer. By using the negative pressure generated by the vortex impeller, an acid-liquid mixture (mainly air and a small amount of acid vapor) is injected into the electrolyte flow at a precise gas-liquid ratio of 0.05-0.08:1, thus cleverly forming a gas-liquid two-phase flow.

[0056] On the one hand, it absorbs the hot and humid air in the insulated water tank and the acid mist in the electrolysis system, which improves the utilization of steam heat energy and reduces the emission of acid mist from the electrolysis system. On the other hand, it introduces gas into the electrolyte to obtain a gas-laden electrolyte, which has the functions of breaking the thermal boundary layer, improving the heat transfer coefficient, preventing scaling and corrosion, and improving heating efficiency. For electrolytes with a temperature of <35℃, it can be heated to the process requirement of 50℃ or above in one operation without the need for multiple cycles of heating, resulting in low energy consumption.

[0057] 3. This invention innovatively adopts a gas-liquid two-phase flow design, enhancing the heat transfer process, increasing the heating rate and primary heat exchange temperature rise, and ensuring process temperature requirements are met. Through the gas washing effect, it significantly reduces scaling and clogging on the acid side of the heat exchanger, decreasing cleaning frequency by over 60%, saving substantial downtime, labor, and water resources. It achieves effective recovery of acid mist from the electrolytic cell, reducing air pollutant emissions and unnecessary chemical consumption, aligning with green manufacturing principles. Simultaneously, the intelligent control system ensures the accuracy and stability of process parameters, reducing human error and guaranteeing long-term, stable, and efficient operation of the electrolysis system. Furthermore, the process route incorporates multiple emergency pipelines (such as electrolyte replenishment tanks and gas-liquid mixer branch designs), improving the overall production system's anti-interference capability and reliability.

[0058] 4. This invention also employs a control system and optimization algorithm design to achieve a process control method that is precise, energy-efficient, and highly stable. It possesses emergency response capabilities and predictive maintenance functions, realizing intelligent operation, as demonstrated in the following aspects:

[0059] Emergency mode: When the initial temperature of the electrolyte is too low, the system can omit some routine processes and directly generate a gaseous electrolyte at 45-50℃ for emergency use by increasing the flow rate of humid air, thus ensuring the continuity of production.

[0060] Intelligent control: By using a multivariable predictive control algorithm to predict future temperature trends and act in advance, the control difficulties of large time lag systems are overcome; the adaptive PID algorithm can automatically tune parameters according to the operating status to ensure optimal control quality under various loads.

[0061] Predictive maintenance: By monitoring the trends of parameters such as differential pressure and efficiency, the system uses algorithm models to provide early warnings of potential scaling or equipment performance degradation, upgrading maintenance from periodic prevention to on-demand performance, realizing planned downtime and avoiding huge losses from unplanned downtime.

[0062] 5. This invention integrates thermodynamic optimization, enhanced mass and heat transfer, corrosion protection, automatic control, and environmental protection concepts, presenting a sophisticated, efficient, and reliable comprehensive industrial thermal management system engineering project. It utilizes steam thermal energy in a gradient manner and creatively introduces a gas-liquid mixing step, effectively solving several key challenges in heating strong acid electrolytes, including efficiency, corrosion, scaling, and acid mist recovery. Compared to traditional direct heating or ordinary heat exchange methods, it exhibits significant advantages in energy efficiency, equipment lifespan, system stability, and environmental friendliness. Attached Figure Description

[0063] Figure 1 This is a process flow diagram of a gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte proposed in this invention.

[0064] Figure 2 This is a three-dimensional structural diagram of the gas-liquid mixer proposed in Embodiment 1 of the present invention;

[0065] Figure 3 This is a top view of the gas-liquid mixer proposed in Embodiment 1 of the present invention;

[0066] Figure 4 This is an architecture diagram of the control system proposed in Embodiment 3 of the present invention.

[0067] In the diagram: 1. Swirl chamber; 2. Vortex propeller; 3. Electrolyte inlet pipe; 4. Electrolyte outlet pipe; 5. Air inlet pipe. Detailed Implementation

[0068] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0069] Example 1

[0070] A gradient high-efficiency isothermal heat exchange process for strong acid electrolytes includes the following steps:

[0071] S1, Steam pressure reduction:

[0072] The high-pressure steam generated by the steam boiler is depressurized by a pressure reducer to control the steam pressure to 3-5 Bar. For example, under rated operating conditions, the steam pressure is reduced from the initial pressure of 12.5 Bar to below 3 Bar, and the saturated steam flow rate is reduced to below 3 t / h.

[0073] S2, Level 1 heating:

[0074] High-pressure steam, after being depressurized, is introduced into the insulated water tank below the liquid surface through a Venturi injector to heat the water in the tank through mass transfer, keeping the water temperature in the tank constant at 80℃. The water in the insulated water tank is continuously supplied through a boiler feedwater softening tank. At the same time, humid air at 100±3℃ is generated above the liquid surface of the insulated water tank and introduced into a gas mixing chamber to mix with the acid mist above the liquid surface of the electrolysis system to obtain an acid-gas mixture. The water inlet temperature of the tank is 60℃, and the outlet water temperature reaches 80℃ after being heated by steam.

[0075] S3, Secondary Heating:

[0076] Hot water at 80°C is transported to a titanium plate heat exchanger using a heating hydraulic module to exchange heat with the strong acid electrolyte that needs to be heated. During the heat exchange process, the hot water temperature drops from 80°C to 60°C and is then reintroduced into an insulated water tank for reheating. Excess hot water is returned to the boiler for reheating, thus realizing the recycling of the solution, reducing heat loss, and ensuring efficient energy circulation. The strong acid electrolyte is pressurized from the electrolyte tank of the electrolysis system through the acid hydraulic module, and then mixed with the acid-gas mixture through a gas-liquid mixer to obtain a gaseous electrolyte at 35±1°C. After heat exchange in the titanium plate heat exchanger, it becomes an electrolyte at 53±2°C, which is then returned to the electrolysis system for continued use.

[0077] The heating hydraulic module consists of two parallel delivery pipes, each equipped with a shut-off valve and a water pump, with the pump also equipped with a flow switch FS. The acid hydraulic module includes a shut-off valve and an acid pump, with the pump also equipped with a flow switch FS. The high-pressure steam pipeline in S2 is equipped with a shut-off valve and a steam solenoid valve. In S3, the outlet pipe section of the titanium plate heat exchanger and the electrolyte outlet pipe section are equipped with pressure gauges PG and temperature display controllers TIC. The inlet pipe section of the titanium plate heat exchanger is equipped with a pressure gauge PG. A temperature sensor TS is located below the liquid level in the insulated water tank. Both the electrolyte inlet and outlet pipe sections of the titanium plate heat exchanger are equipped with solenoid valves. The steam solenoid valve, temperature sensor TS, and solenoid valves are all connected to a control host, which also controls the flow rates of the heating hydraulic module and the acid hydraulic module.

[0078] Reference Figure 2-3 The gas-liquid mixer includes a vortex chamber 1, which consists of a lower circular vortex zone and an upper inverted cone-shaped air inlet zone. A vortex propeller 2 is connected to the center of the vortex zone via a rotating shaft. An electrolyte inlet pipe 3 and an electrolyte outlet pipe 4 are tangentially connected to the outer ring of the vortex zone. An air inlet pipe 5 is connected to the top of the air inlet zone. The vortex propeller 2 is set at an inclination of 30-45°. The pressurized electrolyte drives the vortex propeller 2 to rotate, creating a vacuum in the air inlet zone. This allows the acid mixture in the gas mixing chamber to be introduced into the vortex chamber 1 and mixed with the electrolyte to obtain a gas-laden electrolyte. The gas-liquid volume ratio in the gas-laden electrolyte is 0.05-0.08:1.

[0079] The acid components in the acid mixture are redissolved in the water, thereby reducing the amount of acid mist in the electrolysis system. The acid mixture and electrolyte are pre-mixed for mass and heat transfer. At the same time, the gaseous electrolyte enhances mixing and turbulence: the introduction of air forms a gas-liquid two-phase flow, which greatly enhances the turbulence in the channel, destroys the thermal boundary layer on the acid side, and significantly improves the heat transfer coefficient of the titanium plate wall to the acid. In addition, the air flow helps prevent solid deposition or scouring of the channel wall, and may have a purging / cleaning effect, reducing the cleaning frequency of the acid side channel of the titanium plate heat exchanger from 5-7 times per month without gaseous electrolyte to 1-2 times per month with gaseous electrolyte, significantly reducing downtime costs and water consumption.

[0080] The electrolyte outlet pipe 4 of the gas-liquid mixer is also directly connected to the electrolysis system via a pipeline. When the temperature of the gaseous electrolyte in the outlet pipe 4 reaches 45-50℃, it can be directly introduced into the electrolysis system for emergency use. If problems occur during electrolyte transportation or preparation, causing the electrolysis operation to stall, the acid mist inlet of the gas mixing chamber can be closed, and the flow rate of humid air can be increased to raise the temperature of the gaseous electrolyte. The humid air inlet, acid mist inlet, and outlet pipes of the gas mixing chamber are all equipped with one-way valves to prevent the acid mixture from rushing into the insulated water tank and the electrolysis system. The electrolysis system is also connected to an electrolyte replenishment tank via a pipeline for replenishing the electrolyte.

[0081] Example 2

[0082] The operation of Example 1 also requires the following steps:

[0083] 1. Equipment Installation: Install the following main equipment according to design requirements: 3t steam boiler, boiler heat source distribution cylinder, seamless steel pipes, pressure reducing valve, heat exchange and insulation water tank, water pump, titanium heat exchanger, control unit, and strong acid electrolyte pipeline (PP material) and tank system, etc. Ensure that the connecting pipes between all equipment are well sealed. Seamless steel pipes are used for steam and hot water transportation, connecting all equipment to form a complete heating system.

[0084] 2. System Commissioning: After equipment installation, the entire system is commissioned. Start the steam boiler to generate high-pressure steam, and adjust the steam pressure from 12.5 Bar to the rated operating pressure of 3.0 Bar using the pressure reducer. Check if the inlet water temperature of the insulated water tank is 60℃, observe the steam heating of the water in the tank, and ensure the outlet water temperature is stable at 80℃. Commission the water pump to ensure it can smoothly deliver 80℃ hot water to the titanium plate heat exchanger.

[0085] 3. Operation: After commissioning, the strong acid electrolyte requiring heating is initially heated through a gas-liquid mixer to obtain a gaseous electrolyte, which is then introduced into the heated side of the titanium plate heat exchanger at an initial temperature of approximately 35°C (if below 35°C, the mixing flow rate of humid air can be increased). The system is started, and the hot water and electrolyte exchange heat in the titanium plate heat exchanger. The main control unit monitors and adjusts various parameters in real time to ensure that the hot water temperature on the heat medium side drops from 80°C to 60°C, and the electrolyte temperature on the heated side rises from 35°C to 50°C. The heat-exchanged electrolyte is returned to the electrolysis system for reuse, and the cooled hot water is returned to the boiler through pipelines for further heating, achieving continuous and stable system operation. During operation, the equipment is regularly inspected and maintained to ensure long-term, efficient, and safe system operation.

[0086] Example 3

[0087] Reference Figure 4 Based on Example 1, a control system is added, and the heat exchange process is changed to a strong acid electrolyte gradient high-efficiency isothermal heat exchange process with enhanced intelligent control, including the following steps:

[0088] S1, Steam pressure reduction

[0089] The high-pressure steam generated by the steam boiler is depressurized by a pressure reducer to a pressure of 3-5 Bar. The steam pressure is monitored in real time by a pressure sensor (PT), and the main control unit dynamically adjusts the opening of the pressure reducing valve according to the set value (e.g., 3 Bar) to ensure that the pressure fluctuation range is ≤ ±0.2 Bar.

[0090] S2, Level 1 heating

[0091] After depressurization, steam is injected below the liquid surface of the insulated water tank through a Venturi ejector, heating the water in the tank through mass transfer. The latent heat of the depressurized steam (approximately 3 bar, approximately 134°C) is used to heat a large amount of process water from 60°C to 80°C. This is a phase change heat transfer process with extremely high efficiency, converting the high-grade heat energy of steam into the low-grade heat energy of hot water for storage. The insulated water tank is equipped with multiple temperature sensors (TS), and the main control unit adjusts the opening of the steam solenoid valve through a PID algorithm to keep the water temperature constant at 80°C (allowable deviation ±0.5°C). The water in the insulated water tank is continuously supplied through the boiler feed water softening tank. The 100±3°C humid air generated above the liquid surface mixes with the acid mist from the electrolysis system in the gas mixing chamber. The temperature of the mixed gas is monitored by the TIC, and the mixing ratio of acid mist and humid air is controlled by a proportional valve.

[0092] S3, Secondary Heating

[0093] The heating hydraulic module pumps 80°C hot water into the titanium plate heat exchanger to exchange heat with the electrolyte.

[0094] The heating process of S3 employs the following control strategies: Flow coordination control: The flow rate of hot water and electrolyte is monitored in real time via a flow switch FS, and the host dynamically adjusts the pump frequency to ensure the flow ratio of water to acid is maintained at 1.2-1.5:1; Temperature cascade control: The main loop uses the electrolyte outlet temperature (target 53±2℃) as a reference, and the secondary loop uses the hot water inlet temperature (80℃) as feedback, adjusting the steam supply through a PID algorithm; Emergency mode: When the electrolyte temperature is below 35℃, the humid air flow is automatically increased to raise the temperature of the electrolyte with gas to 45-50℃ for direct reuse. The control strategy of S3 is implemented through a control system, which includes the following modules: Control host: An industrial PLC (such as Siemens S7-1200) paired with an HMI touchscreen, integrating analog input / output modules to receive signals from various sensors.

[0095] Combination Figure 4 and Figure 1 The actuators include steam solenoid valves, water pump frequency converters, and pneumatic regulating valves distributed in the insulated water tank, heating hydraulic module, titanium plate heat exchanger, gas-liquid mixer, acid hydraulic module, and electrolysis system, all supporting 4-20mA signal control; the high-pressure steam pipeline in S2 is equipped with a shut-off valve and a steam solenoid valve; the outlet pipe section of the titanium plate heat exchanger and the electrolyte outlet pipe section in S3 are equipped with pressure gauges PG and temperature display controllers TIC, the inlet pipe section of the titanium plate heat exchanger is equipped with pressure gauge PG, the insulated water tank is equipped with a temperature sensor TS below the liquid level, and the electrolyte inlet pipe section and electrolyte outlet pipe section of the titanium plate heat exchanger are equipped with solenoid valves; the flow valves of the heating hydraulic module and the acid hydraulic module are also included.

[0096] like Figure 4 As shown, the control system includes the following algorithm model:

[0097] (1) Multivariate Predictive Control (MPC) Model

[0098] Establish a dynamic mathematical model of the heat exchange system, with steam pressure P steam Hot water flow rate F water Electrolyte inlet temperature T in-acid As the input variable, the electrolyte outlet temperature T out (t) is the target variable: T out (t)=f(P steam ,F water ,T in-acid )+ε;

[0099] Where ε is the error term, containing all factors that cause the model's predicted value T to be affected. out (t)=f(P steam ,F water ,T in-acid ) and the actual measured value T outFactors that differ between (t) are used; a rolling optimization algorithm is adopted to predict the temperature trend for the next 5 minutes every 30 seconds and adjust the actuator action in advance;

[0100] (2) Adaptive PID parameter tuning

[0101] To address the nonlinear characteristics of the heat exchanger, a fuzzy adaptive PID controller is designed: the deviation e and the rate of change of deviation e c Divide the area into zones and apply a strong proportional effect as needed (proportioning factor K). p ), Integral action (I) i ) or differential action (D d This enables the system to automatically adjust its control parameters (P, I, D) when faced with changes in system characteristics or significant disturbances, i.e., parameter self-tuning, and always maintain optimal control performance;

[0102] (3) Energy efficiency optimization algorithm

[0103] Real-time calculation of system thermal efficiency: ;

[0104] Where η is the energy utilization efficiency, Q acid Q is the heat absorbed by the acid. steam F is the heat released by steam. acid c is the mass flow rate of the acid. p T is the isobaric specific heat capacity of an acid. out-acid T is the outlet temperature of the acid. in-acid F is the inlet temperature of the acid. steam h is the mass flow rate of steam. steam The latent heat of vaporization of steam is continuously calculated and recorded, and the control system will draw daily / weekly energy efficiency trend charts.

[0105] Set an adaptive threshold: If η is lower than the set threshold (e.g., 85%), a cleaning reminder will be automatically triggered or the gas-liquid mixing ratio will be adjusted. The threshold for the cleaning reminder is not fixed. The algorithm will learn the historical efficiency values ​​of the system under optimal conditions to form a dynamic and personalized efficiency benchmark. An alarm will only be triggered if the current efficiency is consistently lower than the benchmark value by a certain margin to avoid false alarms. When efficiency decreases, the system can not only issue an alarm but also provide a preliminary diagnosis based on correlation analysis, such as "The decrease in efficiency may be related to the gas-liquid mixing ratio deviating from the optimal value. It is recommended to check / automatically adjust."

[0106] The mechanism of the rolling optimization algorithm is as follows:

[0107] ① State estimation: Every 30 seconds, the control system uses the latest sensor data to perform real-time estimation of the internal state of the model (such as the temperature of the heat exchanger wall) through a Kalman filter to correct the model error; ② Prediction and optimization: Based on the currently estimated state, the model predicts the change trajectory of the key parameters of the system within the next 5-10 minutes; The optimizer takes "stabilizing the electrolyte outlet temperature at the set value (53°C)" as the main goal and "minimizing the steam consumption" as the economic goal, and calculates a series of optimal future control actions, such as the change in the opening of the steam valve and the frequency of the water pump; ③ Implementation and feedback: Only the first calculated control action is implemented, and then the entire process is repeated in the next sampling period. This "rolling optimization" mechanism enables the system to continuously respond to various disturbances.

[0108] Adaptive PID parameter tuning includes the following process: The temperature deviation |e| and the rate of change of the deviation |e c | are divided into three fuzzy sets of "large, medium, and small". e c is the rate of change between the temperature deviations e detected twice adjacent to each other. The "large" of |e| is the set where > 5°C, the "medium" of |e| is the set where 1 - 5°C, and the "small" of |e| is the set where < 1°C; The "large" of |e c | is the set where > 10%, the "medium" of |e c | is the set where 1 - 10%, and the "small" of |e c | is the set where < 1%; where e = T setpoint -T actual , T setpoint is the set temperature value. For example, the ideal process requires the electrolyte outlet temperature to be 53°C; T actual is the actual temperature value, that is, the electrolyte outlet temperature value measured in real time by the temperature sensor TIC;

[0109] When |e| ∈ "large", a strong proportional action is adopted, that is, K p is increased significantly to quickly eliminate the deviation, ignoring the integral (I i = 0) and derivative (D d ) actions to prevent integral saturation and system oscillation; When |e| ∈ "medium" and |e c | ∈ "small", then K p is reduced, and an appropriate integral action (I i ) is introduced to smoothly eliminate the static error; When |e| ∈ "small" and |e c | ∈ "large", then the derivative action (D d ) is increased to suppress overshoot and improve stability; Anti-integral saturation: When the actuator (such as the steam valve) has reached the limit position (fully open or fully closed) and the deviation has not been eliminated, the algorithm pauses the integral action to prevent large overshoots when resuming.

[0110] The control system also provides the following multi-layered safety protection measures, such as Figure 4 As shown:

[0111] Level 1 equipment: The frequency converters of critical equipment (such as water pumps and acid pumps) have built-in overcurrent and overload protection;

[0112] Secondary process layer: Low flow interlock: If any flow switch FS detects that the flow rate is lower than 50% of the rated value (more stringent setting), an emergency shutdown sequence is immediately triggered: the steam solenoid valve is shut off, the relevant pump is stopped, and the emergency cooling system is activated; High temperature interlock: If the electrolyte outlet temperature exceeds 60℃ or the insulated water tank temperature exceeds 90℃, the heat source is immediately shut off; Pressure interlock: If the steam pressure exceeds the safety limit or the pressure difference ΔP of the titanium plate heat exchanger is continuously higher than 0.15MPa, the system alarms and automatically reduces the load or shuts down;

[0113] Level 3 system layer: The HIM panel of the control host is equipped with a one-button emergency stop button. All interlocking events are recorded in detail, including the trigger time, trigger point, and action result, for post-event analysis.

[0114] Safety protection measures also include the following intelligent emergency modes:

[0115] ① If the electrolyte flow rate drops sharply (FS detects flow rate < 70% of rated value), immediately cut off the steam supply and activate emergency cooling; ② When the pressure difference ΔP across the titanium plate heat exchanger exceeds 0.1 MPa, a blockage risk is identified, the flow rate is automatically reduced, and an alarm is triggered; ③ When the control system detects that the acid side inlet temperature of the titanium plate heat exchanger remains below 35°C, it will automatically determine that the primary heating is insufficient. At this time, the system will perform the following operations: gradually open the humid air inlet proportional valve of the gas mixing chamber; simultaneously fine-tune the bypass valve of the gas-liquid mixer to allow more high-temperature humid air to mix with the electrolyte for preheating; ④ If the temperature still cannot be increased within the set time, an alarm "Electrolyte initial temperature needs to be checked" will be sent to the central control room, and it may be recommended to reduce the production load to maintain a stable outlet temperature.

[0116] Example 3, based on the hardware of Example 1, adds advanced detection and control algorithms to further improve stability, energy efficiency, and predictability. This control system integrates advanced process control, energy efficiency management, and predictive maintenance, significantly enhancing the overall technical level and economic efficiency of the process.

[0117] Comparative Example 1

[0118] Based on Example 1, the gas mixing chamber and its related emergency pipelines are removed, while the rest is the same as in Example 1. The result is that the electrolyte with a temperature <35°C can only be raised to below 48°C in one operation, requiring multiple cycles of heating, which greatly increases the cost; the electrolyte with a temperature ≥35°C can reach about 50°C in one operation, but the acid side channel of the titanium plate heat exchanger needs to be heated 5-7 times per month, while Example 1 only needs to be heated 1-2 times per month.

[0119] Comparative Example 2

[0120] S1. Steam pressure reduction: The high-pressure steam generated by the steam boiler is reduced through a pressure reducer to control the steam pressure to 3-5 Bar.

[0121] S2. Mixed heating: Steam at 120℃ and 3 bar after pressure reduction is directly fed into the electrolyte tank through a Venturi injector for mass transfer heating. The result is fast heating speed and low energy consumption. However, the Venturi injector and its steam pipeline are subject to significant corrosion and need to be replaced 1-2 times a week, resulting in long downtime and hindering the normal operation of the electrolysis system.

[0122] The data from Examples 1 / 3 and Comparative Examples 1 / 2 are summarized in Table 1 below:

[0123] Table 1: Impact of process and control systems on process energy consumption and heating efficiency

[0124]

[0125] Data Analysis:

[0126] 1. Gradient Utilization and High-Efficiency Cycle Mechanism of Steam Thermal Energy: In Example 1, high-quality steam was not directly used for final heating; instead, its energy was released in two stages. First Stage Heating (S2): The latent heat of the depressurized steam (approximately 3 bar, approximately 134°C) was used to heat a large amount of process water from 60°C to 80°C. This is a phase change heat transfer process with extremely high efficiency, converting the high-grade thermal energy of the steam into the low-grade thermal energy of the hot water for storage. Second Stage Heating (S3): The 80°C hot water was used to heat the electrolyte through a titanium plate heat exchanger. This is a liquid-liquid sensible heat exchange process that is gentle and controllable.

[0127] Energy cycle: The hot water after heat exchange drops to 60℃, which is exactly the inlet temperature of the insulated water tank. It can be returned to the water tank for reheating with almost no loss, forming a nearly closed heat cycle (except for heat dissipation through pipes and water replenishment). This greatly reduces the fuel consumption required for the boiler to reheat the 60℃ cold water to 80℃.

[0128] Comparing Example 1 and Comparative Example 2: In Comparative Example 2, 120°C steam is directly injected into the electrolyte. Although the heat transfer rate is fast, its effective energy is seriously wasted. After the latent heat of the steam is used for heating, the energy of the high-temperature condensate (if it is saturated steam, the condensate temperature is also close to 120°C) is not effectively recovered. It is directly discharged into the electrolyte system or requires additional cooling, resulting in lower overall energy efficiency. This process achieves cascaded energy utilization through hot water circulation.

[0129] 2. The function of the gas-liquid mixer, namely, acid mist recovery and enhanced heat transfer mechanism: Acid mist recovery: Acid mist (usually sulfuric acid mist, phosphoric acid mist, etc.) generated by the electrolysis system is introduced into the gas mixing chamber and mixed with 100°C humid air generated by the insulated water tank. The high temperature and high humidity environment of the humid air causes the acid mist molecules to recondense or dissolve, forming an "acid-liquid mixture". When this gas comes into contact with the electrolyte in the gas-liquid mixer, the acid components are quickly absorbed back into the electrolyte. This achieves closed-loop recovery of acid mist, reducing chemical loss and environmental pollution.

[0130] Forming a gas-liquid two-phase flow: The negative pressure generated by the vortex propeller injects the acid mixture (mainly air and a small amount of acid vapor) into the electrolyte flow at a precise gas-liquid ratio of 0.05-0.08:1.

[0131] Disruption of the thermal boundary layer: When a liquid flows over a wall, it forms a relatively static "boundary layer," which is the main obstacle to heat transfer. The bubbles, constantly deforming, bursting, and agitating during the flow, violently disrupt this insulating layer, causing intense mixing between the fluid in the core area and the fluid on the wall. This allows heat to be transferred more efficiently from the titanium plate to the electrolyte bulk.

[0132] Improving the heat transfer coefficient: The sharp increase in turbulence directly leads to a significant increase in the convective heat transfer coefficient on the acid side. This means that with the same heat transfer area and temperature difference, the heat transfer capacity increases significantly, or in other words, to achieve the same heat transfer capacity, a smaller heat transfer area or temperature difference is required.

[0133] Online cleaning (anti-scaling and anti-corrosion): The flushing action of air bubbles (similar to "air washing") effectively prevents solid particles from depositing and forming scale on the channel walls, and may wash away newly formed, soft initial scale layers. At the same time, the flowing air bubbles reduce stagnation areas, avoiding excessively high local concentrations or impurity accumulation, thereby mitigating localized corrosion.

[0134] Comparing Example 1 with Comparative Example 1: Example 1 reduces the cleaning frequency from 5-7 times per month to 1-2 times per month. This is the most direct economic benefit indicator—cleaning frequency—resulting in cost savings: each cleaning session means downtime losses, labor costs, and the costs of cleaning water and chemicals. A 60%-80% reduction in frequency directly leads to a considerable decrease in operating costs. It also improves equipment utilization: equipment runs for longer periods, resulting in better production continuity.

[0135] Heating efficiency: Comparative Example 1 shows that electrolytes with a temperature <35℃ cannot be heated to the required temperature above 50℃ in a single operation, requiring multiple cycles and resulting in high energy consumption. However, Example 1, through enhanced heat transfer, can heat the electrolyte from 35℃ to 53±2℃ in a single operation, achieving higher efficiency and lower energy consumption.

[0136] 3. Material selection and system control mechanism:

[0137] Corrosion protection materials: Seamless steel pipes (high strength, pressure and temperature resistance) are used on the steam and hot water sides (neutral or weakly alkaline). PP (polypropylene) pipes and titanium heat exchangers are used on the strong acid electrolyte side. These materials have excellent corrosion resistance to strong acids, eliminating equipment damage and solution contamination caused by corrosion at the source.

[0138] Precise Control: The system is equipped with a temperature sensor (TS), temperature display controller (TIC), pressure gauge (PG), flow switch (FS), and solenoid valves, all centrally managed by the control unit. This enables real-time monitoring and automatic adjustment of all thermal and hydraulic parameters, ensuring the system always operates under optimal conditions: 80℃ hot water, 35℃ inlet liquid, and 53℃ outlet liquid. This stabilizes the electrolysis process and avoids energy waste or product quality issues caused by temperature fluctuations. Results: The system boasts extremely high reliability, a high degree of automation, and low maintenance requirements.

[0139] Compared to the extremely high maintenance cost of replacing the steam ejector 1-2 times per week in Comparative Example 2, the equipment lifespan advantage of Examples 1 and 3 is unparalleled.

[0140] 4. Emergency Handling Mechanism: When the electrolyte supply is disrupted, the electrolyte inlet and outlet of the titanium plate heat exchanger can be shut off, and the 45-50℃ electrolyte with gas at the outlet of the gas-liquid mixer can be directly fed into the electrolysis system. By closing the acid mist inlet and increasing the flow rate of humid air, the temperature of the mixed solution can be increased. Effect: This provides system redundancy and emergency backup, avoids unplanned shutdowns, and demonstrates the robustness of the process design.

[0141] 5. Algorithm optimization:

[0142] Compared with Example 1, Example 3 shows improved performance, including:

[0143] 1) Control precision:

[0144] Steam pressure: Fluctuation range improved from "3-5 Bar" to ≤±0.2 Bar. Water tank temperature: Improved from "80℃" to 80±0.5℃. Electrolyte outlet temperature: More precise control with smaller fluctuations. Energy efficiency management: Real-time calculation of thermal efficiency η, with adaptive thresholds (e.g., 85%) for monitoring and optimization. Maintenance mode: Upgraded from "periodic / reactive" maintenance to predictive maintenance, providing early warnings (e.g., "cleaning expected in 15 days").

[0145] 2) Control Algorithm:

[0146] ① The heat exchange process has an inertial lag effect. Traditional PID control is a "reactive adjustment" (it only acts after the temperature deviation occurs), while multivariable predictive control (MPC) predicts the temperature trend in the next few minutes based on a model and adjusts the steam valve and water pump in advance to "preemptively suppress" the temperature. It has a stronger ability to cope with disturbances (such as changes in production load), a smoother control curve, and better product quality consistency. At the same time, it reduces steam consumption through optimization.

[0147] ② Conventional PID parameters are fixed, but system operating conditions (such as scaling degree, flow rate changes) will change. Adaptive PID can adjust parameters based on the deviation (e) and the rate of change of the deviation (e). c The magnitude of the value of P, I, and D is automatically adjusted to maintain the optimal response speed and stability under different deviations, preventing overshoot or oscillation and adapting to nonlinear changes in the system.

[0148] ③ Transform the experience of operation experts into program logic. For example, when the system detects that "the electrolyte inlet temperature is consistently below 35°C", it does not simply issue an alarm, but automatically executes a series of operations (opening the humid air valve and adjusting the bypass) to attempt self-repair, thereby enhancing the system's autonomy, reducing unplanned downtime, and ensuring production safety.

[0149] This invention utilizes steam thermal energy in a gradient manner and introduces a gas-liquid mixing step, thus solving several key problems in heating strong acid electrolytes, such as efficiency, corrosion, scaling, and acid mist recovery. Compared with traditional direct heating or ordinary heat exchange methods, it exhibits significant advantages in energy efficiency, equipment lifespan, system stability, and environmental friendliness.

[0150] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A gradient high-efficiency isothermal heat exchange process for strong acid electrolyte, characterized in that, Includes the following steps: S1, Steam pressure reduction The high-pressure steam generated by the steam boiler is depressurized by a pressure reducer. The steam pressure is monitored in real time by a pressure sensor, and the main control unit dynamically adjusts the opening of the pressure reducing valve according to the set value to ensure that the pressure fluctuation range is ≤ ±0.2 Bar. S2, Level 1 heating After depressurization, steam is injected below the liquid surface of the insulated water tank. The insulated water tank is equipped with a multi-point temperature sensor TS. The control host adjusts the opening of the steam solenoid valve through a PID algorithm. The humid air generated above the liquid surface of the insulated water tank mixes with the acid mist of the electrolysis system in the gas mixing chamber. The temperature of the mixed gas is monitored by TIC and the mixing ratio of acid mist and humid air is controlled by a proportional valve. S3, Secondary Heating The heating hydraulic module pumps hot water into the titanium plate heat exchanger to exchange heat with the electrolyte; the strong acid electrolyte is pressurized by the acid hydraulic module and then mixed with the acid gas mixture through the gas-liquid mixer to obtain a gaseous electrolyte, which is then heat-exchanged through the titanium plate heat exchanger to obtain the electrolyte. The heating process of S3 adopts the following control strategy: Flow coordination control: The flow rate of hot water and electrolyte is monitored in real time through the flow switch FS, and the main unit is controlled to dynamically adjust the pump frequency; Temperature cascade control: The main loop uses the electrolyte outlet temperature as a reference, and the secondary loop uses the hot water inlet temperature as feedback. The steam supply is adjusted through a PID algorithm. Emergency mode: When the electrolyte temperature is below 35℃, the flow rate of humid air will be automatically increased.

2. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 1, characterized in that, The control strategy of S3 is implemented through a control system, which includes the following modules: Control host: adopts industrial PLC with HMI touch screen, integrates analog input / output module, and receives signals from various sensors; Actuators: Steam solenoid valve, water pump frequency converter, pneumatic regulating valve, all supporting 4-20mA signal control; The actuator specifically includes the following components: The heating hydraulic module consists of two parallel delivery pipes, each of which is equipped with a shut-off valve and a water pump, and the water pump is equipped with a flow switch FS. The acid hydraulic module includes a shut-off valve and an acid pump, and the acid pump is equipped with a flow switch FS; The high-pressure steam pipeline in S2 is equipped with a shut-off valve and a steam solenoid valve; The S3 titanium plate heat exchanger outlet pipe section and electrolyte outlet pipe section are equipped with pressure gauge PG and temperature display controller TIC. The titanium plate heat exchanger inlet pipe section is equipped with pressure gauge PG. The insulated water tank is equipped with temperature sensor TS below the liquid level. The titanium plate heat exchanger electrolyte inlet pipe section and electrolyte outlet pipe section are both equipped with solenoid valves. Flow valves for heating hydraulic modules and acid hydraulic modules.

3. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 2, characterized in that, The control system includes the following algorithm models: (1) Multivariate predictive control model Establish a dynamic mathematical model of the heat exchange system, with steam pressure P steam Hot water flow rate F water Electrolyte inlet temperature T in-acid As the input variable, the electrolyte outlet temperature T out (t) is the target variable: T out (t)=f(P steam ,F water ,T in-acid )+ε; Where ε is the error term, containing all factors that cause the model's predicted value f(P) to be affected. steam ,F water ,T in-acid ) and the actual measured value T out Factors that cause differences between (t) A rolling optimization algorithm is used to predict the temperature trend for the next 5 minutes every 30 seconds and adjust the actuator actions in advance. (2) Adaptive PID parameter tuning To address the nonlinear characteristics of the heat exchanger, a fuzzy adaptive PID controller is designed: Let the deviation e and the rate of change of deviation e c The system is divided into zones, and strong proportional, integral, or derivative actions are applied as needed, so that it can automatically adjust its control parameters when faced with changes in system characteristics or large disturbances. (3) Energy efficiency optimization algorithm Real-time calculation of system thermal efficiency: ; Where η is the energy utilization efficiency, Q acid Q is the heat absorbed by the acid. steam F is the heat released by steam. acid c is the mass flow rate of the acid. p T is the isobaric specific heat capacity of an acid. out-acid T is the outlet temperature of the acid. in-acid F is the inlet temperature of the acid. steam h is the mass flow rate of steam. steam The latent heat of vaporization of steam is continuously calculated and recorded, and the control system will draw daily / weekly energy efficiency trend charts. Set adaptive threshold: If η is lower than the set threshold, a cleaning reminder will be automatically triggered or the gas-liquid mixing ratio will be adjusted. The threshold for cleaning reminder is not fixed. The algorithm will learn the historical efficiency value of the system under optimal conditions to form a dynamic and personalized efficiency benchmark. An alarm will only be triggered if the current efficiency is continuously lower than the benchmark value by a certain margin to avoid false alarms. When efficiency declines, the system can not only issue an alarm, but also provide a preliminary diagnosis of the cause based on correlation analysis.

4. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 3, characterized in that, The mechanism of the rolling optimization algorithm is as follows: ①State estimation: Every 30 seconds, the control system uses the latest sensor data to estimate the internal state of the model in real time through a Kalman filter in order to correct model errors; ② Prediction and optimization: Based on the current estimated state, the model predicts the trajectory of changes in key system parameters within the next 5-10 minutes; the optimizer takes "stabilizing the electrolyte outlet temperature at the set value" as the main objective and "minimizing steam consumption" as the economic objective, and calculates a series of optimal future control actions, including changes in steam valve opening and pump frequency. ③ Implementation and Feedback: Only the calculated first step of the control action is implemented, and then the entire process is repeated in the next sampling period.

5. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 3, characterized in that, The adaptive PID parameter tuning includes the following process: The temperature deviation |e| and the rate of change of deviation |e c | Divided into three fuzzy sets: "large", "medium", and "small", e c Let |e| be the rate of change between two consecutive temperature deviations (e). The "large" range of |e| represents the set >5℃, the "medium" range represents the set 1-5℃, and the "small" range represents the set <1℃. c | is a set whose "largeness" is greater than 10%, |e c The "middle" of | represents the set of 1-10%, |e c The "small" of | is a set that is less than 1%; Where e=T setpoint -T actual T setpoint To set the temperature value; T actual This is the actual temperature value, i.e., the electrolyte outlet temperature value measured in real time by the temperature sensor TIC; When |e|∈"large", a strong proportional action is applied, i.e., K p Significantly increased, quickly eliminating deviations; When |e| ∈ "medium" and |e c | ∈ "small", then reduce K p , introduce appropriate integral action to smoothly eliminate the static error; When |e|∈"small"and|e c If |∈"large", then the differential action is increased, and overshoot is suppressed; Anti-integral saturation: When the actuator has reached the limit position and the deviation has not been eliminated, the algorithm pauses the integral action to prevent large overshoot during recovery.

6. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 2, characterized in that, The control system also provides the following multi-layered security protection measures: Level 1 Equipment: The frequency converters of key equipment have built-in overcurrent and overload protection; Second-level process layer: Low flow interlock: If any flow switch FS detects that the flow rate is below 50% of the rated value, an emergency shutdown sequence will be immediately triggered: the steam solenoid valve will be shut off, the relevant pumps will be stopped, and the emergency cooling system will be activated; High temperature interlock: If the electrolyte outlet temperature exceeds 60℃ or the insulated water tank temperature exceeds 90℃, immediately cut off the heat source; Pressure interlock: If the steam pressure exceeds the safety limit or the pressure difference ΔP of the titanium plate heat exchanger continues to be higher than 0.15MPa, the system will alarm and automatically reduce the load or shut down. Level 3 system layer: The HIM panel of the control host is equipped with a one-button emergency stop button. All interlocking events are recorded in detail, including the trigger time, trigger point, and action result, for post-event analysis.

7. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 6, characterized in that, The security measures also include the following intelligent emergency modes: ①If the electrolyte flow rate drops suddenly, immediately cut off the steam supply and activate emergency cooling; ② When the pressure difference ΔP across the titanium plate heat exchanger exceeds 0.1 MPa, a blockage risk is identified, the flow rate is automatically reduced, and an alarm is triggered. ③ When the control system detects that the acid side inlet temperature of the titanium plate heat exchanger is consistently below 35°C, it will automatically determine that the primary heating is insufficient. At this time, the system will perform the following operations: gradually open the humid air inlet proportional valve of the gas mixing chamber; and simultaneously fine-tune the bypass valve of the gas-liquid mixer to allow more high-temperature humid air to mix with the electrolyte for preheating. ④ If the temperature still cannot be raised within the set time, an alarm "Electrolyte initial temperature needs to be checked" will be sent to the central control room, and the production load will be reduced to maintain a stable outlet temperature.

8. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 1, characterized in that, The gas-liquid mixer includes a swirl chamber (1), which consists of a lower circular swirl zone and an upper inverted cone-shaped air inlet zone. A vortex propeller (2) is connected to the center of the swirl zone via a rotating shaft. An electrolyte inlet pipe (3) and an electrolyte outlet pipe (4) are tangentially connected to the outer ring of the swirl zone. An air inlet pipe (5) is connected to the top of the air inlet zone. The vortex propeller (2) is set at an inclination of 30-45°. The vortex propeller (2) is driven to rotate by the pressurized electrolyte, and a vacuum is created in the air intake area. This allows the acid mixture in the gas mixing chamber to be introduced into the vortex chamber (1) and mixed with the electrolyte to obtain a gas-carrying electrolyte. The gas-liquid volume ratio in the gas-carrying electrolyte is 0.05-0.08:

1.

9. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 1, characterized in that, The electrolyte outlet pipe (4) of the gas-liquid mixer is also directly connected to the electrolysis system through a pipeline. When the temperature of the gas-containing electrolyte in the electrolyte outlet pipe (4) reaches 45-50℃, it is directly introduced into the electrolysis system for emergency use. The gas mixing chamber is equipped with one-way valves for the humid air inlet pipe, acid mist inlet pipe, and outlet pipe.

10. The gradient high-efficiency isothermal heat exchange process for a strong acid electrolyte according to claim 1, characterized in that, The steam and hot water conveying pipelines in S1, S2 and S3 are made of seamless steel pipes, and the strong acid electrolyte pipeline in S3 is made of PP material. The electrolysis system is also connected to an electrolyte replenishment tank via a pipeline.

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