Storage tank nitrogen sealing control method, system and device and medium

Abstract

The embodiment of the invention provides a storage tank nitrogen sealing control method, system and device and a medium. The method comprises the steps that the real-time pressure in a storage tank is obtained; according to the real-time pressure, a pressure control valve unit is controlled to exhaust or supplement nitrogen to the storage tank, and the liquid level change rate in the storage tank is obtained; under the condition that the liquid level change rate is larger than a preset change rate, feed-forward compensation is conducted on the storage tank according to the first information and the temperature information of the storage tank, so that the air pressure in the storage tank is stable; and under the condition that the liquid level change rate is smaller than or equal to the preset change rate, the pressure feedback value of the storage tank is obtained through the micro-pressure transmitter, and the pressure feedback value is sent to the PLC for PID closed-loop control, so that the air pressure in the storage tank is stable. Feed-forward compensation or PID closed-loop control is selected according to the liquid level change rate, so that the nitrogen sealing pressure in the storage tank is accurately controlled, the gas phase space pressure stability of the storage tank and the system safety are improved, and the nitrogen consumption is reduced.

Description

Technical Field

[0001] This invention relates to, but is not limited to, the field of nitrogen sealing technology for storage tanks, and particularly to a nitrogen sealing control method, system, device, and medium for storage tanks. Background Technology

[0002] The main purpose of nitrogen sealing of storage tanks is to maintain a slight positive pressure in the tank, isolate the material from the outside environment, reduce the volatilization and waste of the material, and protect the safety of the storage tank.

[0003] However, existing nitrogen sealing systems for storage tanks suffer from low pressure control accuracy due to factors such as delayed response of the breather valve, sudden changes in inlet and outlet flow rates, and temperature fluctuations. This results in low pressure stability in the gas phase space of the storage tank, high nitrogen consumption, and low system safety. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0005] The main objective of this invention is to provide a nitrogen sealing control method, system, device, and medium for storage tanks, which can improve the pressure stability of the gas phase space in the storage tank and the safety of the system, while reducing nitrogen consumption.

[0006] In a first aspect, embodiments of the present invention provide a nitrogen blanketing control method for a storage tank, applied to a nitrogen blanketing system. The nitrogen blanketing system includes a nitrogen replenishment unit, a pressure control valve unit, a storage tank unit, and a control unit. The storage tank unit includes a storage tank and an inlet / outlet pump, a drain valve, and a breather valve installed on the storage tank. The control unit includes a micro-pressure transmitter and a PLC controller connected to the storage tank. The PLC controller is connected to the pressure control valve unit, the inlet / outlet pump, the drain valve, and the micro-pressure transmitter, respectively. The method includes: Obtain the real-time pressure inside the storage tank; The pressure control valve unit is used to vent or replenish nitrogen in the storage tank according to the real-time pressure, and the rate of change of liquid level in the storage tank is obtained. When the liquid level change rate is greater than the preset change rate, feedforward compensation is performed on the storage tank based on the first information corresponding to the feed pump, the drain valve and the breather valve and the temperature information of the storage tank, so as to stabilize the gas pressure in the storage tank. The first information represents the feed information, drainage information and sensitivity information. When the liquid level change rate is less than or equal to the preset change rate, the pressure feedback value of the storage tank is obtained through the micro pressure transmitter, and the pressure feedback value is sent to the PLC controller for PID closed-loop control to stabilize the gas pressure in the storage tank.

[0007] In some optional embodiments, the step of performing feedforward compensation on the storage tank based on the first information corresponding to the feed pump, the drain valve, and the breather valve, and the temperature information of the storage tank, includes: The first pressure change value is determined based on the feed and discharge information and the second information of the storage tank, wherein the second information represents the information corresponding to the liquid and gas phase spaces inside the storage tank. The second pressure change value is determined based on the nitrogen loss corresponding to the drainage volume information; The third pressure change value caused by the sensitivity hysteresis of the breathing valve is determined based on the sensitivity information; The fourth pressure change value is determined based on the temperature information; The first pressure change value, the second pressure change value, the third pressure change value, and the fourth pressure change value are used to feedforward compensation for the storage tank.

[0008] In some optional embodiments, determining the first pressure change value based on the inlet / outlet information and the second information of the storage tank includes: When the feed or discharge information indicates that the storage tank is handling feed or discharge, the volume of the gas pressure space inside the storage tank, the maximum liquid level height of the storage tank, the set pressure of the storage tank, and the gas compressibility coefficient are obtained. The first pressure change value is determined based on the liquid level change rate, the gas pressure space volume, the maximum liquid level height, and the gas compressibility coefficient.

[0009] In some optional embodiments, determining the second pressure change value based on the nitrogen loss corresponding to the drainage information includes: Obtain the absolute pressure and atmospheric pressure of the discharge valve; The nitrogen loss is determined based on the absolute pressure, the atmospheric pressure, the displacement information, and the loss correction factor. The second pressure change value is determined based on the nitrogen loss and the preset pressure conversion formula.

[0010] In some optional embodiments, the pressure control valve unit is connected to a buffer compensation tank, and the method for setting the volume of the buffer compensation tank includes: Obtain the maximum nitrogen replenishment flow rate of the pressure control valve unit and the single drainage volume corresponding to the drainage information; Obtain the preset system response time and security factor; The minimum volume of the buffer compensation tank is determined based on the maximum nitrogen replenishment flow rate, the single drainage volume, the system response time, and the safety factor.

[0011] In some optional embodiments, determining the fourth pressure change value based on the temperature information includes: The heat of vaporization of the medium, the set temperature, the gas constant, and the compensation gain are obtained, wherein the heat of vaporization of the medium characterizes the heat of vaporization of the substance stored in the tank; Obtain the real-time temperature of the gas phase space inside the storage tank; The fourth pressure change value is determined based on the heat of vaporization of the medium, the set temperature, the gas constant, the compensation gain, the real-time temperature, and the set pressure.

[0012] In some optional embodiments, before controlling the pressure control valve unit to vent or replenish nitrogen in the storage tank according to the real-time pressure, the method further includes: Mechanical hysteresis is eliminated in the pressure control valve unit: Nitrogen gas is replenished to the test tank at a preset replenishment rate, and the exhaust status of the pressure control valve unit is detected. The pressure relief point of the pressure control valve unit is set according to the gas output state and the pressure inside the test tank; Nitrogen gas is discharged from the test tank at a preset exhaust rate, and the closed state of the exhaust port is detected. The pressure replenishment point of the pressure control valve unit is set according to the closed state and the pressure inside the test tank.

[0013] Secondly, embodiments of the present invention provide a nitrogen blanketing control system for storage tanks, applied to the aforementioned nitrogen blanketing control method for storage tanks, wherein the nitrogen blanketing control system for storage tanks includes: The first module is used to obtain the real-time pressure inside the storage tank; The second module is used to control the pressure control valve unit to vent or replenish nitrogen in the storage tank according to the real-time pressure, and to obtain the liquid level change rate in the storage tank. The third module is used to perform feedforward compensation on the storage tank based on the first information corresponding to the feed pump, the drain valve and the breather valve and the temperature information of the storage tank when the liquid level change rate is greater than the preset change rate, so as to stabilize the gas pressure in the storage tank. The first information represents the feed information, drainage information and sensitivity information. The fourth module is used to obtain the pressure feedback value of the storage tank through the micro pressure transmitter when the liquid level change rate is less than or equal to the preset change rate, and send the pressure feedback value to the PLC controller for PID closed-loop control to stabilize the gas pressure in the storage tank.

[0014] Thirdly, embodiments of the present invention provide a nitrogen sealing control device for a storage tank, comprising: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor performs the method described above.

[0015] Fourthly, a computer storage medium stores computer-executable instructions for executing the nitrogen sealing control method for the storage tank described in the first aspect.

[0016] The beneficial effects of this invention include: acquiring the real-time pressure inside the storage tank; controlling the pressure control valve unit to vent or replenish nitrogen in the storage tank based on the real-time pressure, and acquiring the liquid level change rate inside the storage tank; when the liquid level change rate is greater than a preset change rate, performing feedforward compensation on the storage tank based on first information corresponding to the inlet / outlet pump, the drain valve, and the breather valve, and the temperature information of the storage tank, to stabilize the gas pressure inside the storage tank, wherein the first information represents inlet / outlet information, drainage volume information, and sensitivity information; when the liquid level change rate is less than or equal to the preset change rate, acquiring the pressure feedback value of the storage tank through the micro-pressure transmitter, and sending the pressure feedback value to the PLC controller for PID closed-loop control, to stabilize the gas pressure inside the storage tank. By timely replenishing nitrogen or venting based on the real-time pressure, and selecting feedforward compensation based on the discharge information, drainage volume information, and sensitivity information, or PID closed-loop control based on the pressure feedback value through the liquid level change rate, the nitrogen sealing pressure inside the storage tank can be precisely controlled, improving the stability of the gas phase space pressure in the storage tank and the system safety, while reducing nitrogen consumption.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0018] Figure 1 This is a structural block diagram of the nitrogen sealing system for storage tanks provided in an embodiment of the present invention; Figure 2 This is a flowchart of the steps of a nitrogen sealing control method for storage tanks provided in an embodiment of the present invention; Figure 3 This is a flowchart of the judgment feedforward compensation and PID closed-loop control provided in the embodiments of the present invention; Figure 4 This is a flowchart illustrating the nitrogen replenishment and venting process of the pressure valve provided in this embodiment of the invention. Figure 5 This is a flowchart of the process for hysteresis compensation debugging of a pressure valve provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a controller provided in one embodiment of the present invention.

[0019] Reference numerals: Controller 1000, Processor 1100, Memory 1200. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, or the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0022] This application provides a nitrogen sealing control method, system, and storage medium for storage tanks, which will be described in detail in the following embodiments.

[0023] like Figure 1 The diagram shows a nitrogen sealing system for achieving nitrogen sealing of a storage tank, as described in this application. The nitrogen sealing system includes a nitrogen replenishment unit, a pressure control valve unit, a storage tank unit, and a control unit. The storage tank unit includes a storage tank and inlet / outlet pumps, a drain valve, and a breather valve installed on the tank. The control unit includes a micro-pressure transmitter connected to the storage tank and a PLC controller. The PLC controller is connected to the pressure control valve unit, the inlet / outlet pumps, the drain valve, and the micro-pressure transmitter, respectively, and is used to receive feedback information and send control commands. The nitrogen replenishment unit specifically includes a nitrogen source for providing the required nitrogen.

[0024] The pressure control valve unit includes a self-operated pressure regulating valve with a pilot valve (referred to as a pressure valve); a buffer compensation tank is connected to the pressure valve. When the pressure in the storage tank drops suddenly, the pressure of the nitrogen source may fluctuate. The buffer compensation tank can pre-store a certain amount of nitrogen and quickly replenish the pressure in the storage tank when the pressure valve is opened, avoiding negative pressure and air backflow in the tank due to delayed nitrogen supply. When the pressure in the tank rises suddenly, the buffer compensation tank can first receive part of the discharged nitrogen (or gaseous medium), relieving the instantaneous discharge load of the pressure valve and preventing instantaneous pressure overshoot from disrupting the nitrogen seal micro-positive pressure balance. The buffer compensation tank can store a certain volume of nitrogen. When the pressure in the storage tank fluctuates slightly, the supply and demand are regulated by the nitrogen in the compensation tank first (releasing the nitrogen in the tank when the pressure is low and temporarily storing excess nitrogen when the pressure is high), reducing the opening and closing frequency of the pressure valve, extending the valve life, and ensuring the continuity and stability of the nitrogen seal pressure.

[0025] The feed pump is used to inject stored materials into the storage tank, and the discharge pump is used to discharge stored materials from the tank. A drain valve is located at the bottom of the tank to discharge water, impurities, etc., generated within the tank. A breather valve prevents excessive or insufficient pressure within the tank; it discharges nitrogen when the pressure is too high and draws in air when the pressure is too low to prevent tank deformation. A radar level gauge is installed on the tank, which monitors the real-time pressure of the gas phase space through a pressure tap. In the PID control, a micro-pressure transmitter obtains the pressure feedback value from the tank and sends it to the PLC controller. The PLC controller initiates nitrogen replenishment or venting based on the specific pressure feedback value. This control has a certain delay and can be used for small pressure changes within the tank.

[0026] like Figure 2 As shown, this embodiment of the invention provides a nitrogen sealing control method for storage tanks, including steps S100, S200, S300, and S400: Step S100: Obtain the real-time pressure inside the storage tank.

[0027] Specifically, a radar level gauge is installed on the storage tank, which detects the real-time pressure of the gas phase space through the pressure tap.

[0028] Step S200: Based on the real-time pressure, control the pressure control valve unit to vent or replenish nitrogen in the storage tank, and obtain the liquid level change rate in the storage tank.

[0029] Specifically, refer to Figure 3 The pressure control valve unit (pressure valve), acting as the actuator, first makes preliminary adjustments based on the real-time pressure. When the pressure is lower than the set value, the nitrogen replenishment channel is opened to replenish nitrogen; when it is higher than the set value, the pressure relief channel is opened to release redundant gas. The liquid level change rate is a key dividing line indicator for judging the operating condition. Its magnitude directly determines whether to use feedforward compensation or PID closed-loop control mode, because the degree of disturbance to the gas pressure inside the tank and the response requirements differ between rapid and gradual changes in liquid level.

[0030] Reference Figure 4 The pressure control valve unit adopts a self-operated pressure regulating valve (pressure valve) with a pilot valve. Its nitrogen replenishment and venting principle is as follows: the pressure sensor on the pressure valve obtains the real-time pressure value and sends it to the pilot valve diaphragm. The pilot valve diaphragm converts the pressure signal into a mechanical displacement signal. When the pressure is less than the set pressure, the main valve spring pushes the pilot valve core downward, increasing the opening and increasing the amount of nitrogen replenished to the storage tank. When the pressure is greater than the set pressure, the main valve diaphragm pushes the pilot valve core upward, decreasing the opening and increasing the amount of venting from the storage tank.

[0031] Step S300: When the liquid level change rate is greater than the preset change rate, feedforward compensation is performed on the storage tank according to the first information corresponding to the feed pump, the drain valve and the breather valve and the temperature information of the storage tank, so as to stabilize the gas pressure in the storage tank. The first information represents the feed information, drainage information and sensitivity information.

[0032] Specifically, when the rate of change in liquid level exceeds a preset value (such as a sudden rise in liquid level due to rapid feeding into the tank, or a sudden drop in liquid level due to large-scale discharge), the gas phase space inside the tank will shrink or expand drastically. In this case, relying solely on pressure feedback for regulation will result in significant pressure fluctuations due to lag. Feedforward compensation aims to anticipate disturbances and intervene in advance, specifically by calculating the compensation amount based on the first piece of information.

[0033] The feed and discharge information of the feed pumps can directly calculate the rate and scale of liquid level changes. For example, the instantaneous flow rate of the feed pump can determine the rate at which the gas phase space shrinks, and thus predict the magnitude of the gas pressure rise. The discharge volume information of the drain valve can help judge the change in the total volume of the medium in the tank, avoiding misjudgment of gas pressure caused by indirect fluctuations in liquid level due to drainage. The sensitivity information of the breather valve can determine its opening / closing pressure threshold, and a pressure adjustment margin can be reserved during feedforward compensation to prevent conflict with the breather valve's operation.

[0034] Temperature changes affect the vapor pressure of nitrogen and other media inside the tank; for example, nitrogen expansion at high temperatures increases pressure. Incorporating temperature parameters into feedforward compensation corrects pressure deviations caused by temperature disturbances, preventing accidental nitrogen injection or depressurization. Ultimately, the PLC controller uses this information to pre-calculate precise control values, driving the pressure control valve unit to operate in advance, significantly reducing the difficulty of subsequent adjustments.

[0035] In some optional embodiments, the step of performing feedforward compensation on the storage tank based on the first information corresponding to the feed pump, the drain valve, and the breather valve, and the temperature information of the storage tank, includes: S310. Determine a first pressure change value based on the feed and discharge information and the second information of the storage tank, wherein the second information represents the information corresponding to the liquid and gas phase spaces inside the storage tank. Specifically, the second piece of information includes the total volume of the storage tank, the current liquid phase volume, the gas phase space volume, and the compressibility coefficient of the medium. Based on the instantaneous flow rate and duration of the feed pumps, the change in liquid phase volume corresponding to the change in liquid level is calculated, thereby obtaining the change in gas phase space volume. Then, combined with the gas state equation for nitrogen, the first pressure change caused by the change in gas phase space volume is deduced.

[0036] S320. Determine the second pressure change value based on the nitrogen loss corresponding to the drainage information; Specifically, when the drain valve is opened to drain water, not only is the liquid accumulated at the bottom of the tank discharged, but nitrogen is also lost due to entrainment in the gas phase space, which in turn causes a drop in gas pressure. Based on the drainage capacity of the drain valve and the structural parameters of the storage tank (such as the dead zone volume at the bottom of the tank and the drainage velocity), the amount of nitrogen loss per unit drainage volume is determined through experimental calibration or empirical formulas. Combining this with the ideal gas equation, the amount of nitrogen loss is converted into a second pressure change value.

[0037] S330. Determine the third pressure change value caused by the sensitivity hysteresis of the breathing valve based on the sensitivity information; Specifically, based on the difference between the current pressure of the storage tank and the action threshold of the breather valve, and the rate of pressure change within the lag time (the higher the sensitivity, the smaller the lag time) (determined by changes in liquid level or temperature), the pressure deviation caused by the lag is calculated to obtain the third pressure change value.

[0038] S340. Determine the fourth pressure change value based on the temperature information; Specifically, the real-time temperature and temperature change rate are obtained through the temperature sensor of the storage tank; with the gas phase space volume and nitrogen mass remaining constant, the fourth pressure change value is derived based on the ideal gas equation.

[0039] S350, Feedforward compensation is performed on the storage tank using the first pressure change value, the second pressure change value, the third pressure change value, and the fourth pressure change value.

[0040] Specifically, the PLC controller vector-superimposes the four pressure change values ​​to obtain the total compensation pressure value, and then converts the positive and negative signs and amplitude of the total compensation pressure value into specific control commands for the pressure control valve unit, thereby performing feedforward compensation for the storage tank.

[0041] In some optional embodiments, determining the first pressure change value based on the inlet / outlet information and the second information of the storage tank includes: S311. When the feed or discharge information indicates that the storage tank is processing feed or discharge, obtain the volume of the gas pressure space inside the storage tank, the maximum liquid level height of the storage tank, the set pressure of the storage tank, and the gas compressibility coefficient. S312. Determine the first pressure change value based on the liquid level change rate, the gas pressure space volume, the maximum liquid level height, and the gas compressibility coefficient.

[0042] Specifically, the gas pressure space volume is the real-time volume of the gas phase within the storage tank (i.e., the total tank volume minus the current liquid phase volume); the maximum liquid level height is the highest liquid level threshold under safe operating conditions; the set pressure is the target gas pressure inside the tank; the gas compressibility coefficient is a dimensionless physical property parameter related to the stored material; and the liquid level change rate characterizes the amount of change in the tank liquid level per unit time (positive values ​​indicate an increase in the feed liquid level, and negative values ​​indicate a decrease in the discharge liquid level). By correlating the liquid level change rate with the rate of change in the gas phase space, and then combining this with the gas compressibility coefficient to correct for pressure changes under ideal gas conditions, the first pressure change value that closely matches the actual operating conditions is finally obtained. The specific formula for calculating the first pressure change value is as follows:

[0043] in, This is the first pressure change value. This is the proportional gain coefficient; Characterizes the rate of change of liquid level; Characterizes the set pressure; Characterizes the maximum liquid level height; Characterizes the volume of the gas phase space; Characterizes the compressibility of a gas.

[0044] In some optional embodiments, determining the second pressure change value based on the nitrogen loss corresponding to the drainage information includes: S321. Obtain the absolute pressure and atmospheric pressure of the discharge valve; S322. Determine the nitrogen loss based on the absolute pressure, the atmospheric pressure, the displacement information, and the loss correction coefficient; S323. Determine the second pressure change value based on the nitrogen loss and the preset pressure conversion formula.

[0045] Specifically, when the drain valve drains water, the absolute pressure inside the tank is higher than atmospheric pressure. This pressure difference will drive some nitrogen gas to be discharged along with the accumulated liquid. The calculation of this loss needs to consider both the pressure difference and the drainage volume. The specific calculation formula is as follows:

[0046]

[0047] in, Indicates the amount of nitrogen lost; Indicates absolute pressure; Indicates the amount of water discharged; Indicates atmospheric pressure; This represents the second pressure change value; the loss correction factor is 0.78. It is the gas constant; This refers to the absolute temperature of the gas phase space inside the tank.

[0048] In some optional embodiments, the pressure control valve unit is connected to a buffer compensation tank, and the method for setting the volume of the buffer compensation tank includes: S350, Obtain the maximum nitrogen replenishment flow rate of the pressure control valve unit and the single drainage volume corresponding to the drainage information; S351. Obtain the preset system response time and security factor; S352. Determine the minimum volume of the buffer compensation tank based on the maximum nitrogen replenishment flow rate, the single drainage volume, the system response time, and the safety factor.

[0049] Specifically, the maximum nitrogen replenishment flow rate is the instantaneous nitrogen flow rate when the nitrogen replenishment valve in the pressure control valve unit is fully open, reflecting the system's maximum nitrogen supply capacity; the single drainage volume is the cumulative drainage volume of a single opening of the drain valve, used to calculate the maximum nitrogen loss corresponding to a single drainage; the system response time is the lag time from the tank pressure deviating from the set value to the pressure control valve completing the adjustment, including the total time consumed by sensor response, PLC calculation, and valve action; the safety factor is a preset coefficient to cope with fluctuations in operating conditions. The specific calculation formula is as follows:

[0050] in, This indicates the minimum volume of the buffer compensation tank; This is the maximum nitrogen replenishment flow rate; This refers to the volume of water discharged in a single instance. This refers to the system response time. This is for the safety factor.

[0051] instantaneous nitrogen supply flow rate of the system The calculation formula is:

[0052] in, This is the valve flow coefficient; The pressure difference across the valve; The density of nitrogen gas; This is the specific gravity coefficient of the gas (0.97 for nitrogen). This is the tank pressure correction function. The controller dynamically adjusts the control accuracy to ±50Pa. Depend on Calculated.

[0053] In some optional embodiments, determining the fourth pressure change value based on the temperature information includes: S341. Obtain the heat of vaporization of the medium, set the temperature, gas constant, and compensation gain, wherein the heat of vaporization of the medium characterizes the heat of vaporization of the substance stored in the storage tank; S342. Obtain the real-time temperature of the gas phase space inside the storage tank; S343. Determine the fourth pressure change value based on the medium evaporation heat, the set temperature, the gas constant, the compensation gain, the real-time temperature, and the set pressure.

[0054] Specifically, the heat of vaporization of the medium is the heat required for a unit mass (or mole) of the tank medium to change from a liquid to a gaseous state; the set temperature is the target temperature for the nitrogen sealing system to operate normally; and the gas constant is also relevant. =8.314; the compensation gain is the coefficient that corrects the deviation between the temperature disturbance model and the actual operating conditions; the real-time temperature is the instantaneous temperature of the gas phase space inside the storage tank; the set pressure is the slight positive pressure inside the tank that the nitrogen sealing system needs to maintain. Specific calculation formulas include:

[0055] in, The heat of evaporation of the medium; To set the temperature; This refers to the real-time temperature of the gas phase. To compensate for the gain.

[0056] In some optional embodiments, before controlling the pressure control valve unit to vent or replenish nitrogen in the storage tank according to the real-time pressure, the method further includes: S201. Perform mechanical hysteresis elimination on the pressure control valve unit: S202. Nitrogen gas is added to the test tank at a preset gas replenishment rate, and the gas outlet status of the pressure control valve unit is detected. S203. Set the pressure relief point of the pressure control valve unit according to the gas output state and the pressure inside the test tank; S204. Expel nitrogen gas from the test tank at a preset exhaust rate and detect the closed state of the exhaust port; S205. Set the pressure compensation point of the pressure control valve unit according to the closed state and the pressure in the test tank.

[0057] Specifically, refer to Figure 5Mechanical hysteresis in pressure control valves refers to the deviation between the valve's operating pressure and the theoretically set pressure. This is mainly caused by: frictional resistance between the valve core and seat, elastic deformation of the seals; deviation in the preload force and elastic hysteresis of the valve spring; and delay in action caused by impurities stuck inside the valve body. After initial commissioning, the inlet valve on the storage tank is closed. Nitrogen is added to the test tank at a preset replenishment rate, and the exhaust status of the pressure control valve unit is monitored. Once nitrogen is detected at the exhaust port, the corresponding gas phase space pressure is set as the pressure relief point, i.e., the pressure value for initiating exhaust. After exhaust begins, nitrogen is discharged from the test tank at a preset exhaust rate, and the closing status of the exhaust port is observed. When the exhaust port closes, the corresponding gas phase space pressure is set as the pressure replenishment point, i.e., the starting pressure value for replenishing nitrogen. This eliminates mechanical hysteresis, ensuring the hysteresis pressure difference is less than 0.05 kPa (the specific value is not limited here).

[0058] Step S400: When the liquid level change rate is less than or equal to the preset change rate, the pressure feedback value of the storage tank is obtained through the micro pressure transmitter, and the pressure feedback value is sent to the PLC controller for PID closed-loop control to stabilize the gas pressure in the storage tank.

[0059] Specifically, when the rate of change of liquid level is less than or equal to the preset value, the operating conditions of the storage tank tend to be stable, with small and slow pressure disturbances. In this case, PID closed-loop control is suitable for fine-tuning. The control logic is as follows: a micro-pressure transmitter continuously collects pressure feedback values; the PLC controller compares the feedback value with the set value to determine the deviation; then, a proportional element quickly responds to the current deviation, an integral element eliminates potential steady-state deviations, and a derivative element suppresses minor fluctuations in the deviation; finally, the opening of the pressure control valve is fine-tuned based on the calculation results. This can accurately counteract small fluctuations in liquid level and minor external pressure disturbances, stabilizing the tank pressure within the set slightly positive pressure range, ensuring nitrogen sealing effectiveness, and simultaneously preventing frequent large valve movements, thus extending equipment lifespan.

[0060] The beneficial effects of this invention include: acquiring the real-time pressure inside the storage tank; controlling the pressure control valve unit to vent or replenish nitrogen in the storage tank based on the real-time pressure, and acquiring the liquid level change rate inside the storage tank; when the liquid level change rate is greater than a preset change rate, performing feedforward compensation on the storage tank based on first information corresponding to the inlet / outlet pump, the drain valve, and the breather valve, and the temperature information of the storage tank, to stabilize the gas pressure inside the storage tank, wherein the first information represents inlet / outlet information, drainage volume information, and sensitivity information; when the liquid level change rate is less than or equal to the preset change rate, acquiring the pressure feedback value of the storage tank through the micro-pressure transmitter, and sending the pressure feedback value to the PLC controller for PID closed-loop control, to stabilize the gas pressure inside the storage tank. By timely replenishing nitrogen or venting based on the real-time pressure, and selecting feedforward compensation based on the discharge information, drainage volume information, and sensitivity information, or PID closed-loop control based on the pressure feedback value through the liquid level change rate, the nitrogen sealing pressure inside the storage tank can be precisely controlled, improving the stability of the gas phase space pressure in the storage tank and the system safety, while reducing nitrogen consumption.

[0061] Secondly, embodiments of the present invention provide a nitrogen blanketing control system for storage tanks, applied to the aforementioned nitrogen blanketing control method for storage tanks, wherein the nitrogen blanketing control system for storage tanks includes: The first module is used to obtain the real-time pressure inside the storage tank; The second module is used to control the pressure control valve unit to vent or replenish nitrogen in the storage tank according to the real-time pressure, and to obtain the liquid level change rate in the storage tank. The third module is used to perform feedforward compensation on the storage tank based on the first information corresponding to the feed pump, the drain valve and the breather valve and the temperature information of the storage tank when the liquid level change rate is greater than the preset change rate, so as to stabilize the gas pressure in the storage tank. The first information represents the feed information, drainage information and sensitivity information. The fourth module is used to obtain the pressure feedback value of the storage tank through the micro pressure transmitter when the liquid level change rate is less than or equal to the preset change rate, and send the pressure feedback value to the PLC controller for PID closed-loop control to stabilize the gas pressure in the storage tank.

[0062] The above is a schematic scheme of a nitrogen sealing control system for a storage tank according to this embodiment. It should be noted that the technical solution of this system and the technical solution of the nitrogen sealing control method for the storage tank described above belong to the same concept. For details not described in detail in the technical solution of the system, please refer to the description of the technical solution of the nitrogen sealing control method for the storage tank described above.

[0063] like Figure 6 As shown, Figure 6A structural block diagram of a controller 1000 in a nitrogen sealing control device for a storage tank according to an embodiment of this application is shown. The controller 1000 includes, but is not limited to, a memory 1200 and a processor 1100. The processor 1100 is connected to the memory 1200 via a bus, and the memory 1200 is used to store data.

[0064] The controller 1000 also includes an access device that enables the controller 1000 to communicate via one or more networks. Examples of such networks include a Public Switched Telephone Network (PSTN), a Local Area Network (LAN), a Wide Area Network (WAN), a Personal Area Network (PAN), or a combination of communication networks such as the Internet. The access device may include one or more of any type of wired or wireless network interface (e.g., a Network Interface Card (NIC)), such as an IEEE 802.11 Wireless Local Area Network (WLAN) interface, a Wi-MAX interface, an Ethernet interface, a Universal Serial Bus (USB) interface, a cellular network interface, a Bluetooth interface, a Near Field Communication (NFC) interface, and so on.

[0065] The controller 1000 can be any type of stationary or mobile electronic device, including mobile computers or mobile electronic devices (e.g., tablet computers, personal digital assistants, laptop computers, notebook computers, netbooks, etc.), mobile phones (e.g., smartphones), wearable electronic devices (e.g., smartwatches, smart glasses, etc.) or other types of mobile devices, or stationary electronic devices such as desktop computers or PCs. The controller 1000 can also be a mobile or stationary server.

[0066] The processor 1100 is used to execute computer-executable instructions for the nitrogen sealing control method of the storage tank.

[0067] The above is a schematic diagram of a controller according to this embodiment. It should be noted that the technical solution of this controller belongs to the same concept as the technical solution of the nitrogen sealing control method for storage tanks described above. For details not described in detail in the technical solution of the controller, please refer to the description of the technical solution of the nitrogen sealing control method for storage tanks described above.

[0068] This application embodiment also provides a storage medium, which is a computer-readable storage medium, storing a computer program that, when executed by a processor, implements the above-described nitrogen sealing control method for storage tanks.

[0069] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof. The device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate, and may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0070] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as processors, such as central processing units, digital signal processors, or microprocessors executing software, or as hardware, or as integrated circuits, such as application-specific integrated circuits. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically include computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0071] The above provides a detailed description of the preferred embodiments of this application. However, this application is not limited to the above-described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for nitrogen sealing control in storage tanks, characterized in that, The method is applied to a nitrogen blanketing system, which includes a nitrogen replenishment unit, a pressure control valve unit, a storage tank unit, and a control unit. The storage tank unit includes a storage tank and inlet / outlet pumps, a drain valve, and a breather valve mounted on the tank. The control unit includes a micro-pressure transmitter and a PLC controller connected to the storage tank. The PLC controller is connected to the pressure control valve unit, the inlet / outlet pumps, the drain valve, and the micro-pressure transmitter, respectively. Obtain the real-time pressure inside the storage tank; The pressure control valve unit is used to vent or replenish nitrogen in the storage tank according to the real-time pressure, and the rate of change of liquid level in the storage tank is obtained. When the liquid level change rate is greater than the preset change rate, feedforward compensation is performed on the storage tank based on the first information corresponding to the feed pump, the drain valve and the breather valve and the temperature information of the storage tank, so as to stabilize the gas pressure in the storage tank. The first information represents the feed information, drainage information and sensitivity information. When the liquid level change rate is less than or equal to the preset change rate, the pressure feedback value of the storage tank is obtained through the micro pressure transmitter, and the pressure feedback value is sent to the PLC controller for PID closed-loop control to stabilize the gas pressure in the storage tank.

2. The nitrogen sealing control method for storage tanks according to claim 1, characterized in that, The step of performing feedforward compensation on the storage tank based on the first information corresponding to the feed pump, the drain valve, and the breather valve, and the temperature information of the storage tank, includes: The first pressure change value is determined based on the feed and discharge information and the second information of the storage tank, wherein the second information represents the information corresponding to the liquid and gas phase spaces inside the storage tank. The second pressure change value is determined based on the nitrogen loss corresponding to the drainage volume information; The third pressure change value caused by the sensitivity hysteresis of the breathing valve is determined based on the sensitivity information; The fourth pressure change value is determined based on the temperature information; The first pressure change value, the second pressure change value, the third pressure change value, and the fourth pressure change value are used to feedforward compensation for the storage tank.

3. The nitrogen sealing control method for storage tanks according to claim 2, characterized in that, The step of determining the first pressure change value based on the inlet / outlet information and the second information of the storage tank includes: When the feed or discharge information indicates that the storage tank is handling feed or discharge, the volume of the gas pressure space inside the storage tank, the maximum liquid level height of the storage tank, the set pressure of the storage tank, and the gas compressibility coefficient are obtained. The first pressure change value is determined based on the liquid level change rate, the gas pressure space volume, the maximum liquid level height, and the gas compressibility coefficient.

4. The nitrogen sealing control method for storage tanks according to claim 2, characterized in that, Determining the second pressure change value based on the nitrogen loss corresponding to the drainage information includes: Obtain the absolute pressure and atmospheric pressure of the discharge valve; The nitrogen loss is determined based on the absolute pressure, the atmospheric pressure, the displacement information, and the loss correction factor. The second pressure change value is determined based on the nitrogen loss and the preset pressure conversion formula.

5. The nitrogen sealing control method for storage tanks according to claim 4, characterized in that, The pressure control valve unit is connected to a buffer compensation tank, and the method for setting the volume of the buffer compensation tank includes: Obtain the maximum nitrogen replenishment flow rate of the pressure control valve unit and the single drainage volume corresponding to the drainage information; Obtain the preset system response time and security factor; The minimum volume of the buffer compensation tank is determined based on the maximum nitrogen replenishment flow rate, the single drainage volume, the system response time, and the safety factor.

6. The nitrogen sealing control method for storage tanks according to claim 3, characterized in that, Determining the fourth pressure change value based on the temperature information includes: The heat of vaporization of the medium, the set temperature, the gas constant, and the compensation gain are obtained, wherein the heat of vaporization of the medium characterizes the heat of vaporization of the substance stored in the tank; Obtain the real-time temperature of the gas phase space inside the storage tank; The fourth pressure change value is determined based on the heat of vaporization of the medium, the set temperature, the gas constant, the compensation gain, the real-time temperature, and the set pressure.

7. The nitrogen sealing control method for storage tanks according to claim 1, characterized in that, Before controlling the pressure control valve unit to vent or replenish nitrogen in the storage tank according to the real-time pressure, the method further includes: Mechanical hysteresis is eliminated in the pressure control valve unit: Nitrogen gas is replenished to the test tank at a preset replenishment rate, and the exhaust status of the pressure control valve unit is detected. The pressure relief point of the pressure control valve unit is set according to the gas output state and the pressure inside the test tank; Nitrogen gas is discharged from the test tank at a preset exhaust rate, and the closed state of the exhaust port is detected. The pressure replenishment point of the pressure control valve unit is set according to the closed state and the pressure inside the test tank.

8. A nitrogen sealing control system for a storage tank, characterized in that, The nitrogen blanketing control method for storage tanks according to any one of claims 1-7, wherein the nitrogen blanketing control system for storage tanks comprises: The first module is used to obtain the real-time pressure inside the storage tank; The second module is used to control the pressure control valve unit to vent or replenish nitrogen in the storage tank according to the real-time pressure, and to obtain the liquid level change rate in the storage tank. The third module is used to perform feedforward compensation on the storage tank based on the first information corresponding to the feed pump, the drain valve and the breather valve and the temperature information of the storage tank when the liquid level change rate is greater than the preset change rate, so as to stabilize the gas pressure in the storage tank. The first information represents the feed information, drainage information and sensitivity information. The fourth module is used to obtain the pressure feedback value of the storage tank through the micro pressure transmitter when the liquid level change rate is less than or equal to the preset change rate, and send the pressure feedback value to the PLC controller for PID closed-loop control to stabilize the gas pressure in the storage tank.

9. A nitrogen sealing control device for a storage tank, characterized in that, include: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor performs the method as described in any one of claims 1-7.

10. A computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions, which are used to execute the nitrogen sealing control method for storage tanks according to any one of claims 1-7.

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