Intelligent ammonia water safe unloading system for tank car and control method

Abstract

The invention relates to the technical field of liquefiable fluid unloading, in particular to an intelligent ammonia water safe unloading system for a tank car and a control method, and the system realizes full-process automatic and closed operation of ammonia water unloading through cooperation of a buffer tank, a gas phase balance pipeline, an electronic liquid level meter, an electric valve and an intelligent control system. The system maintains the pressure balance between the tank car and the ammonia water storage tank through the gas phase balance pipeline, and the intelligent control system automatically switches the two operation modes of liquid inlet buffering and transferring and discharging according to the liquid level information of the buffer tank, and executes a standard stop program when the conditions are met. After the system executes a stop program, the residual ammonia water in the pipeline is automatically recovered to the buffer tank by reopening the electric valve of the inlet pipeline, so that the safety and environmental protection problems caused by residual liquid discharge in the traditional operation are thoroughly solved, and the safety, environmental protection and high efficiency of the ammonia water unloading process are realized.

Description

Technical Field

[0001] This application relates to the field of unloading technology for easily liquefied fluids, specifically to an intelligent ammonia water safety unloading system and control method for tank trucks. Background Technology

[0002] Ammonia water, as an important chemical raw material and denitrification reducing agent, is widely used in industrial production. Its transportation and unloading involve highly volatile and irritating ammonia, posing significant safety risks. Currently, the industry commonly uses tank trucks for transportation. Upon arrival at the user's location, the ammonia water is transferred to fixed storage tanks via rubber hoses or metal flexible hoses using unloading pumps. This traditional operating mode is highly dependent on manual operation and has a series of inherent defects, becoming a pressing safety and environmental protection problem that the industry urgently needs to solve.

[0003] During ammonia unloading, the loading port on the top of the tanker truck needs to be opened to balance the pressure, causing the volatilized ammonia gas to leak directly, resulting in air pollution at the work site and endangering personnel health. At the end of ammonia unloading, the residual ammonia water in the connecting pipelines cannot be effectively recovered and is usually treated by direct discharge or flushing, which not only wastes materials but also easily leads to personal injury and environmental pollution accidents. When ammonia water storage tanks are being fed, the gas inside the tank is discharged into the atmosphere through the breather valve, and the entrained ammonia gas causes fugitive emissions; at the same time, if the tank level gauge malfunctions and causes overflow, ammonia water will overflow through the exhaust system, with serious consequences. Throughout the entire process, the opening and closing of valves and the starting and stopping of pumps are all judged and operated manually, which carries the risk of misoperation and is labor-intensive and inefficient.

[0004] While existing technologies have made some improvements to address the aforementioned issues, such as adding valves to pipelines or using more corrosion-resistant materials, these improvements are mostly limited to localized optimizations and fail to provide a comprehensive, closed-loop, automated, and inherently safe solution at the system level. Therefore, developing an intelligent system capable of systematically solving the safety, environmental protection, and automation problems during ammonia unloading has significant application value. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an intelligent ammonia water safety unloading system and control method for tank trucks.

[0006] In a first aspect, the present invention provides an intelligent ammonia safety unloading system for tank trucks, comprising: The buffer tank is connected to the tank truck via an inlet pipeline and to the ammonia storage tank via an outlet pipeline and an ammonia unloading pump. A gas phase balance pipeline is connected between the top of the ammonia storage tank and the top of the tank truck to establish and maintain gas phase pressure balance between the ammonia storage tank and the tank truck during the ammonia unloading process. An electronic level gauge is installed on the buffer tank to monitor its internal liquid level; Multiple electric valves are installed at least on the inlet pipe, outlet pipe, and exhaust port pipe of the buffer tank; The intelligent control system is communicatively connected to the electronic level gauge, the ammonia unloading pump, and each of the electric valves. The intelligent control system is configured as follows: Based on the liquid level information fed back by the electronic level gauge, the buffer tank is controlled to alternately perform liquid inlet buffering operation and transfer discharge operation. The liquid inlet buffering operation includes opening the inlet pipeline electric valve to allow ammonia water to flow from the tank truck into the buffer tank. The transfer discharge operation includes opening the outlet pipeline electric valve and starting the ammonia unloading pump to transport the ammonia water in the buffer tank to the ammonia water storage tank. When the preset ammonia unloading stop condition is met, a stop procedure is executed. The stop procedure includes at least closing the inlet pipeline electric valve to stop liquid inlet. After executing the stop procedure, a residual liquid recovery operation is performed. The residual liquid recovery operation includes reopening the inlet pipeline electric valve to allow the residual ammonia water remaining in the inlet pipeline to flow into the buffer tank.

[0007] As a preferred embodiment of the technical solution of the present invention, it further includes a pressure sensing unit for monitoring the pressure difference between the tank truck and the buffer tank; The intelligent control system is communicatively connected to the pressure sensing unit and is further configured as follows: Based on the real-time liquid level data from the electronic level gauge and the differential pressure data from the pressure sensing unit, the rotational speed of the ammonia unloading pump or the opening degree of the electric valve in the outlet pipeline is dynamically adjusted to stably control the liquid level in the buffer tank within a preset target operating range. Specifically, the intelligent control system pre-stores or learns the differential pressure-flow characteristic relationship of the inlet pipeline system to estimate the inlet flow rate based on the real-time differential pressure; the intelligent control system pre-stores or learns the pump speed-flow characteristic curve of the ammonia unloading pump in the outlet pipeline system to estimate the outlet flow rate based on the set speed value or to deduce the set speed value from the target outlet flow rate.

[0008] By introducing a pressure sensing unit and dynamically adjusting the ammonia unloading pump or valve based on real-time liquid level and differential pressure data, the system can proactively respond to changes in operating conditions, rather than passively waiting for the liquid level to exceed the limit, thereby accurately stabilizing the buffer tank liquid level within the target range. Stable liquid level control avoids frequent start-stop of the ammonia unloading pump and pressure surges in the pipeline, reducing equipment wear and energy consumption, and preventing pump cavitation damage due to excessively low liquid levels or overflow risks due to excessively high liquid levels.

[0009] As a preferred embodiment of the technical solution of the present invention, the intelligent control system is specifically configured as follows: Based on the rate of change of liquid level fed back by the electronic level gauge and the differential pressure data of the pressure sensing unit, the time when the liquid level in the buffer tank reaches the preset high limit or low limit is predicted. Based on the predicted time, a feedforward-feedback composite control algorithm is used to adjust the speed of the ammonia unloading pump in advance to suppress overshoot and drastic fluctuations in the buffer tank level. The feedforward-feedback composite control algorithm includes: calculating a flow imbalance prediction based on the inlet flow rate estimated from the differential pressure-flow characteristic relationship and the outlet flow rate estimated from the pump speed-flow characteristic curve; generating a feedforward control quantity based on this prediction; and then superimposing it with a feedback control quantity based on the level deviation before outputting the result.

[0010] By analyzing the trend of liquid level changes and pressure differential, the time when the liquid level reaches its limit can be predicted, allowing for early intervention. This changes the traditional reactive correction mode of control systems, enabling proactive prevention. Employing a feedforward-feedback composite control, the feedforward component directly offsets flow rate changes caused by pressure differential variations, while the feedback component eliminates residual deviations. The combination of these two methods effectively suppresses drastic fluctuations and overshoot in the liquid level, ensuring an extremely smooth unloading process and further enhancing safety and process quality.

[0011] As a preferred embodiment of the technical solution of the present invention, it further includes a gas analysis unit, which is installed on the gas phase equilibrium pipeline for monitoring the concentration of oxygen in the pipeline; The intelligent control system is communicatively connected to the gas analysis unit and is further configured as follows: The oxygen concentration in the gas phase balance pipeline is monitored in real time; when the oxygen concentration exceeds a first safety threshold, a safety alarm is generated; and / or, when the oxygen concentration exceeds a higher second safety threshold, a safety intervention action is triggered; the safety intervention action includes: controlling the opening of the injection valve connected to the inert gas source to inject inert gas into the gas phase balance pipeline.

[0012] By monitoring oxygen concentration in real time and automatically injecting inert gas, the system actively maintains the gaseous space in a non-flammable state, fundamentally eliminating the risk of ammonia forming an explosive mixture with air and providing inherent safety that traditional mechanical protection cannot achieve. The system differentiates between warning and action thresholds, enabling tiered management of safety status. It can issue early warnings when potential risks appear (Level 1 alarm) and automatically execute emergency intervention when danger is imminent (Level 2 alarm), responding rapidly and accurately, greatly reducing the possibility of combustion and explosion accidents.

[0013] As a preferred embodiment of the technical solution of the present invention, it also includes an environmental sensing unit for collecting ambient temperature and / or wind speed data at the unloading site. The intelligent control system is communicatively connected to the environmental sensing unit and is further configured as follows: Based on the ambient temperature and / or wind speed data, dynamically adjust the parameters in the preset ammonia unloading stop conditions, or the safety parameters related to the gas phase space.

[0014] The system can automatically adjust safety thresholds and operating parameters based on ambient temperature and wind speed. In hot, windless weather, it automatically lowers the high-level pump shutdown threshold and oxygen activation threshold, ensuring that the safety margin always matches environmental risk. This solves the problem of fixed-parameter systems potentially lacking sufficient protection in severe weather or exhibiting low efficiency in mild weather.

[0015] As a preferred embodiment of the technical solution of the present invention, a check valve is provided on the gas phase balance pipeline to prevent gas from flowing back from the tank truck to the ammonia storage tank. The buffer tank has an exhaust port connected to an upward-extending exhaust pipe, the outlet height of which is configured to be higher than the ammonia storage tank and the tank truck.

[0016] The check valve effectively prevents gas from flowing back into the relatively pure ammonia storage tank, protecting the quality of the medium inside the tank and ensuring system safety. Positioning the buffer tank's exhaust pipe outlet above both the storage tank and the tank truck utilizes the physical height difference to create a natural barrier, ensuring that gas emitted from the buffer tank diffuses upwards under any circumstances, avoiding the risk of accumulation at lower levels.

[0017] As a preferred embodiment of the present invention, the inlet of the buffer tank is located at the upper part of the tank body, and the upper detection point of the electronic level gauge is not lower than the lower edge of the inlet, and the lower detection point of the electronic level gauge is not higher than the upper edge of the outlet of the buffer tank; the intelligent control system is preset with a high limit threshold and a low limit threshold based on the electronic level gauge.

[0018] By limiting the installation range of the level gauge and its position relative to the inlet and outlet, it is ensured that the range measured by the level gauge is precisely the effective working volume of the buffer tank, thus avoiding detection blind spots and providing a reliable data foundation for intelligent control.

[0019] The preset high and low thresholds provide clear judgment criteria for the system's automatic start-up, shutdown, switching, and interlocking protection, making the entire control logic rigorous and reliable and avoiding malfunctions.

[0020] As a preferred embodiment of the present invention, the inlet of the buffer tank is connected to the inlet pipe through an inlet pipe extending into the tank body, and the distance from the outlet end face of the inlet pipe to the top of the buffer tank is 75%-95% of the total height of the buffer tank.

[0021] The inlet pipe extending into the tank allows ammonia to be released below the liquid surface, naturally forming a liquid seal at the pipe opening. This significantly reduces the escape of gas carried by the ammonia upon entering the tank and the possibility of short-circuiting gas from the tank through the inlet, further reducing fugitive emissions during loading and unloading. A fixed inlet depth defines a stable gas-phase buffer volume, which is beneficial for calculating and stabilizing system pressure balance, and improves the efficiency of the gas-phase balance pipeline.

[0022] Secondly, the present invention also provides an intelligent ammonia safety unloading control method for tank trucks based on the system described in the first aspect, executed by the intelligent control system, comprising the following steps: S1. Open the electric valve of the inlet pipeline and the exhaust valve of the buffer tank to allow ammonia water to flow into the buffer tank under the action of pressure difference; S2. When the buffer tank level reaches the first preset level, close the exhaust valve, open the outlet pipeline electric valve and start the ammonia unloading pump to transfer the ammonia water to the ammonia water storage tank. S3. During the buffer transfer phase, at least one of the following shall be executed in parallel: Based on the real-time liquid level in the buffer tank and the pressure difference between the tank truck and the buffer tank, the speed of the ammonia unloading pump is dynamically adjusted to keep the liquid level stable in the second preset liquid level range. The gas composition in the gas phase balance pipeline is monitored in real time. If the oxygen concentration exceeds the limit, an alarm or inerting protection action is triggered. S4. Monitor whether the preset stop conditions are met. If they are met, execute the stop procedure. After the stop procedure, perform the residual liquid recovery operation.

[0023] As a preferred embodiment of the technical solution of the present invention, the stopping condition is: the liquid level of the ammonia storage tank reaches a preset high level, or the liquid level of the buffer tank drops to a preset low threshold. The shutdown procedure includes: opening the buffer tank vent valve, closing the electric valve of the inlet pipeline, waiting for the buffer tank liquid level to drop to the preset low threshold, closing the buffer tank outlet valve and the ammonia unloading pump, and finally closing the buffer tank vent valve. The residual liquid recovery operation is as follows: after closing the inlet valve of the buffer tank, reopen the valve to allow the residual ammonia in the connecting pipeline to flow into the buffer tank by gravity, and then close the valve again.

[0024] The system differentiates between two shutdown conditions: full storage tank and empty buffer tank. It also specifies standard shutdown procedures, including pressure balancing, ensuring a smooth and orderly shutdown process and preventing water hammer or pressure imbalance in pipelines caused by sudden shutdowns. The system clearly defines the method for reopening the inlet valve at specific times to recover residual liquid using gravity flow. The operation is simple, reliable, and fully automated, ensuring the effective execution of the residual ammonia recovery process and achieving closed-loop environmentally friendly operation.

[0025] As can be seen from the above technical solutions, this application has the following advantages: By alternating operation modes of liquid inlet buffering and material transfer, the traditional manual operation process is transformed into a standardized procedure automatically executed by an intelligent control system, fundamentally eliminating the risk of human error. The buffer tank, as a key buffer unit, not only enables flow control, but its associated residual liquid recovery operation can automatically recover residual ammonia in the connecting pipeline, solving the environmental pollution problem caused by residual liquid discharge at the end of ammonia unloading. Connecting the storage tank and the tank truck through a gas phase balance pipeline effectively balances the pressure of both, reducing ammonia volatilization and leakage caused by pressure fluctuations, providing a basic safety guarantee for the entire unloading process. Attached Figure Description

[0026] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a connection block diagram of the intelligent control system provided in an embodiment of the present invention.

[0028] Figure 2 A block diagram of a system provided in an embodiment of the present invention.

[0029] Figure 3 This is a flowchart illustrating the method provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the purpose, features, and advantages of this application more apparent and understandable, specific embodiments and accompanying drawings will be used to clearly and completely describe the technical solution protected by this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this application and in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] like Figure 1 As shown, this embodiment of the invention provides an intelligent ammonia water safety unloading system for tank trucks, comprising: The buffer tank is connected to the tank truck via an inlet pipeline and to the ammonia storage tank via an outlet pipeline and an ammonia unloading pump. A gas phase balance pipeline is connected between the top of the ammonia storage tank and the top of the tank truck to establish and maintain gas phase pressure balance between the ammonia storage tank and the tank truck during the ammonia unloading process. An electronic level gauge is installed on the buffer tank to monitor its internal liquid level; Multiple electric valves are installed at least on the inlet pipe, outlet pipe, and exhaust port pipe of the buffer tank; The intelligent control system is communicatively connected to the electronic level gauge, the ammonia unloading pump, and each of the electric valves. The intelligent control system is configured as follows: Based on the liquid level information fed back by the electronic level gauge, the buffer tank is controlled to alternately perform liquid inlet buffering operation and transfer discharge operation. The liquid inlet buffering operation includes opening the inlet pipeline electric valve to allow ammonia water to flow from the tank truck into the buffer tank. The transfer discharge operation includes opening the outlet pipeline electric valve and starting the ammonia unloading pump to transport the ammonia water in the buffer tank to the ammonia water storage tank. When the preset ammonia unloading stop condition is met, a stop procedure is executed. The stop procedure includes at least closing the inlet pipeline electric valve to stop liquid inlet. After executing the stop procedure, a residual liquid recovery operation is performed. The residual liquid recovery operation includes reopening the inlet pipeline electric valve to allow the residual ammonia water remaining in the inlet pipeline to flow into the buffer tank.

[0033] In practice, the connection from the ammonia water inlet to the buffer tank is as follows: quick connector, stainless steel pipe (10cm long), electric ball valve, manual ball valve, stainless steel pipe (length as needed). Normally, the electric ball valve is closed, and the manual ball valve is open for emergency closure. The second section of stainless steel pipe connects to the upper part of the buffer tank, with the distance from the top of the connection point to the top of the buffer tank being 85% of the total height of the buffer tank.

[0034] Buffer tank: ① A vent pipe (DN20) is installed at the top center. The vent pipe is equipped with one electric ball valve and one manual ball valve. The length of the vent pipe should be sufficient to extend 50cm above the ammonia storage tank and the tank truck to prevent ammonia from being discharged from the venting system; ② The buffer tank is equipped with one electronic level gauge. The upper part of the level gauge is flush with the lower edge of the ammonia inlet, and the lower part is flush with the upper edge of the ammonia outlet. The upper limit is set at the upper 15% of the level gauge, and the lower limit is set at the lower 15% of the level gauge; ③ The ammonia outlet of the buffer tank is connected to the ammonia unloading pump using a stainless steel pipe, with one electric ball valve and one manual ball valve installed in the middle.

[0035] From ammonia storage tank to ammonia tanker truck: The ammonia storage tank is equipped with a breather valve and a check valve at the top. A flexible metal hose with the same diameter as the ammonia unloading system is installed outside the check valve. A metal disc is connected to the hose, and this disc should be able to connect to the ammonia filling port on the tanker truck. The breather valve is installed on this gas phase balance pipeline as a safety backup for the system.

[0036] Connect the metal hose to the quick-connect interface at the inlet of the buffer tank and verify no leakage using an ammonia leak detection device. Next, open the top of the tanker truck and connect it to the vent valve disc of the ammonia storage tank. Click the "Automatic Ammonia Unloading" button on the top of the control panel. The system first opens the inlet ball valve and the vent ball valve at the top of the buffer tank. When the buffer tank level rises to 20% of the top of the level gauge, it closes the vent valve at the top of the buffer tank, opens the ball valve between the buffer tank and the ammonia unloading pump, and starts the ammonia unloading pump. When the level reaches the upper limit, the control system triggers a high-high alarm and interlocks to shut down the inlet electric valve of the buffer tank and the ammonia unloading pump.

[0037] (1) When the ammonia water storage tank level gauge reaches 85% of the tank height, first open the vent valve at the top of the buffer tank, then close the inlet ball valve of the buffer tank. When the level gauge of the buffer tank reaches the lower limit, close the ball valve between the buffer tank and the ammonia unloading pump, then close the ammonia unloading pump and close the vent valve at the top of the buffer tank.

[0038] (2) When the level gauge of the buffer tank reaches the lower limit, it means that the tank truck has been emptied and the relevant procedure (1) is executed.

[0039] After ammonia unloading is complete, open the inlet ball valve of the buffer tank and manually unload the residual ammonia from the metal hose connecting the tank truck and the buffer tank into the buffer tank. Then disconnect the metal hose joint and check the residual ammonia again. If it has been emptied, close the inlet electric butterfly valve of the buffer tank. Disconnect the ammonia storage tank exhaust system disc from the top of the tank truck, close the ammonia inlet on the top of the tank truck, and place the exhaust system disc in a dedicated water tank or pool to absorb ammonia vapor and prevent ammonia vapor from overflowing under normal circumstances.

[0040] This application connects an ammonia transport tanker truck to an ammonia unloading system. An ammonia unloading buffer tank is installed in the middle, equipped with a venting system and a level gauge. The ammonia storage tank's venting system is connected to the loading disc of the tanker truck, ensuring pressure balance among the tanker truck, ammonia storage tank, and buffer tank, and establishing a gas phase balance loop between the storage tank and the tanker truck. Intelligent start-stop control of the buffer tank's level is used. All key control points in the unloading system employ electric ball valves, and valve control and ammonia unloading pump startup are controlled by a PLC or DCS intelligent control system.

[0041] That is, a check valve is installed on the gas phase balance pipeline to prevent gas from flowing back from the tanker truck to the ammonia storage tank; the vent of the buffer tank is connected to an upward-extending vent pipe, and the outlet height of the vent pipe is configured to be higher than the ammonia storage tank and the tanker truck. The inlet of the buffer tank is located at the upper part of its tank body, and the upper detection point of the electronic level gauge is not lower than the lower edge of the inlet, and the lower detection point of the electronic level gauge is not higher than the upper edge of the outlet of the buffer tank; the intelligent control system is preset with high and low level thresholds based on the electronic level gauge. The inlet of the buffer tank is connected to the inlet pipeline through an inlet pipe extending into the tank body, and the distance from the outlet end face of the inlet pipe to the top of the buffer tank is 75%-95% of the total height of the buffer tank.

[0042] In some embodiments, a pressure sensing unit is also included for monitoring the pressure difference between the tank truck and the buffer tank; The intelligent control system is communicatively connected to the pressure sensing unit and is further configured as follows: Based on the real-time liquid level data of the electronic level gauge and the differential pressure data of the pressure sensing unit, the speed of the ammonia unloading pump or the opening degree of the electric valve in the outlet pipeline is dynamically adjusted to stably control the liquid level of the buffer tank within the preset target working range.

[0043] During the operation of the ammonia unloading pump and the transfer of material from the buffer tank to the ammonia storage tank, the liquid level in the buffer tank is maintained within a preset target working range to avoid the liquid level being too high (leading to overflow risk due to proximity to the inlet) or too low (leading to cavitation and cavitation of the ammonia unloading pump), while improving unloading efficiency. In this embodiment of the invention, the target working range is 30%-70% of the liquid level metering range.

[0044] Input signals include: real-time liquid level in the buffer tank as feedback from the electronic level gauge. The real-time pressure difference between the tank truck and the buffer tank is measured by the pressure sensing unit. ,in, It is the main driving force that propels ammonia water from the tanker truck into the buffer tank, and its changes directly affect the inlet flow rate.

[0045] The output signals include: the speed setpoint sent to the frequency converter of the ammonia unloading pump. Or send the opening setting value to the electric regulating valve in the outlet pipeline. For example, in a variable frequency pump system, the main adjustment is the rotational speed, while in a constant speed pump system, the main adjustment is the valve opening. This embodiment of the invention uses the adjustment of the ammonia unloading pump speed as an example for illustration.

[0046] Specific control steps include: Step 1: System Initialization and Parameter Setting Target liquid level In this embodiment of the invention, the liquid level measurement range is set to 50%.

[0047] Target work area In this embodiment of the invention, the percentages are set to [30%, 70%], and the primary objective of the control is to make... It falls within this range.

[0048] Control cycle The time interval between each calculation and adjustment performed by the control system.

[0049] Pressure differential-flow characteristic model / curve This is an empirical or theoretical model used to calculate based on real-time differential pressure. Estimated inflow rate from tanker truck to buffer tank To achieve precise feedforward control, the intelligent control system pre-stores or obtains the pressure-flow characteristic relationship of the inlet pipeline system through self-learning. This relationship indicates the pressure difference between the tank truck and the buffer tank under a specific pipeline configuration. and the resulting ammonia inlet flow rate The quantitative correspondence between them. This relationship can be represented by a mathematical model. ， in The flow coefficient is obtained through system calibration.

[0050] During the control process, the system reads the differential pressure signal measured by the pressure sensing unit in real time. Based on the pressure difference-flow characteristic relationship, the current inlet flow rate is estimated in real time. This estimated value is used in the feedforward control channel to compensate for changes in the inlet flow rate caused by differential pressure fluctuations. This, combined with level feedback control, enables rapid, stable, and high-precision control of the buffer tank level.

[0051] Pump speed-flow characteristic curve: used to determine the flow rate based on the current pump speed. Estimated outflow rate from the buffer tank pump Similarly, to achieve precise control and estimation of the ammonia unloading pump's output flow rate, the intelligent control system pre-stores or obtains the pump speed-flow characteristic curve of the ammonia unloading pump in the specific outlet pipeline system through self-learning. This characteristic curve indicates the pump speed under the current pipeline resistance characteristics. and the output flow generated The quantitative correspondence between them can be obtained through calibration tests during the commissioning phase: that is, under conditions of no liquid inflow interference, the rate of drop in the buffer tank level is measured at different stable pump speeds, thereby calculating and fitting the value of the liquid level. The relationship curve.

[0052] During the control process, the system utilizes this characteristic curve to achieve bidirectional mapping: (Positive) Based on the current pump speed setting. Estimate the current actual output flow. It is used for predicting liquid level changes and calculating feedforward compensation.

[0053] (Reverse) When the control algorithm calculates the target output flow rate to be achieved At that time, the required pump speed value can be obtained by reverse calculation based on this characteristic curve. And send it to the pump drive unit for execution.

[0054] PID controller parameters: proportional coefficient Integral time Differential time .

[0055] Step 2: Data Acquisition and Preprocessing In each control cycle Initially, the system reads through the communication interface: Real-time liquid level in buffer tank ; Real-time pressure difference between tank truck and buffer tank ; Current speed of ammonia unloading pump (Output value of the previous cycle); For reading and Perform filtering (such as moving average filtering) to eliminate signal noise.

[0056] Step 3: Calculation and Interval Determination of Liquid Level Deviation Calculate the deviation between the current liquid level and the target liquid level: .

[0057] judge Which region is it located in? Safe Zone: Within this range, precise adjustments are performed with the goal of making Approaching .

[0058] Warning zone: Within this range, rapid adjustments are performed with the goal of quickly bringing the liquid level back to the safe zone.

[0059] Danger Zone: Approaching 0% or 100%. Emergency interlock is triggered, and this routine adjustment procedure is suspended.

[0060] Step 4: Model-based feedforward control calculation use and pressure difference-flow model Predict the current inlet flow rate .

[0061] use Based on the pump speed-flow characteristic curve, estimate the current outlet flow rate: .

[0062] Calculate the estimated flow imbalance: . This indicates that if more liquid enters than exits, the liquid level will rise; conversely, if less liquid enters than exits, the level will fall.

[0063] according to Given the cross-sectional area A of the buffer tank, predict the liquid level change trend: predict the liquid level change in the next cycle. .

[0064] Feedforward control output: based on Directly calculate the pump speed adjustment amount for feedforward compensation. The purpose is to preemptively offset the impact of inlet flow rate fluctuations caused by pressure differential changes on the liquid level. For example, when Enlargement leads to When the value increases, the feedforward control will increase in advance. This is to match the increased liquid inflow, thereby stabilizing the liquid level.

[0065] Step 5: Feedback-based PID control calculation Based on the liquid level deviation obtained in step three Based on the deviation history, standard PID control algorithm calculations are performed: Proportional Term ; Integral term ; Differential term ; Feedback control output: .

[0066] Step Six: Control Output Combining and Limiting Synthesized final control quantity: The feedforward output and the feedback output are added together to obtain the total speed adjustment. .

[0067] Calculate the new pump speed setpoint: .

[0068] Output limiting processing: make sure The speed shall not exceed the maximum safe speed and minimum stable speed allowed by the ammonia unloading pump.

[0069] if In the warning zone, stronger control parameters (such as larger ones) can be used. Alternatively, it can output a fixed, large adjustment value for a faster response.

[0070] Output control signal: the signal after amplitude limiting As The speed is adjusted by sending analog output or communication protocol data to the frequency converter of the ammonia unloading pump.

[0071] Step 7: Execute repeatedly Waiting for the next control cycle T to arrive, return to step two to begin a new round of data acquisition, calculation, and adjustment, forming a closed-loop control.

[0072] In some embodiments, the intelligent control system is specifically configured as follows: Based on the rate of change of liquid level fed back by the electronic level gauge and the differential pressure data of the pressure sensing unit, the time when the liquid level in the buffer tank reaches the preset high limit or low limit is predicted. Based on the predicted time, the rotational speed of the ammonia unloading pump is adjusted in advance through a feedforward-feedback composite control algorithm to suppress overshoot and drastic fluctuations in the buffer tank level.

[0073] To further suppress liquid level fluctuations and prevent the triggering of high and low limit alarms, the intelligent control system performs the following predictive control steps: S1. Real-time calculation of the rate of change of the buffer tank level. And combined with the pressure difference measured by the pressure sensing unit By using a pre-stored system model, the system dynamically predicts when the liquid level will reach a preset high limit. or lower limit Remaining time .

[0074] S2, will With the preset warning time threshold Comparison. When ≤ When this occurs, the system is deemed to require emergency intervention. Based on the predicted arrival time and current net flow, the system calculates a targeted feedforward control variable. The purpose of this control quantity is to... Within a given timeframe, the liquid level change trend will be smoothly guided towards a safe direction.

[0075] S3. Simultaneously, the system calculates the conventional PID feedback control quantity based on the current liquid level deviation in parallel. . Feedforward control quantity With feedback control quantity The commands are superimposed to synthesize the final control instructions.

[0076] S4. The synthesized control command is converted into the speed setting value of the ammonia unloading pump. After being processed by rate limiting and amplitude limiting, it is sent to the pump drive unit for execution.

[0077] In some embodiments, a gas analysis unit is also included, which is disposed on the gas phase balance pipeline for monitoring the oxygen concentration in the pipeline; The intelligent control system is communicatively connected to the gas analysis unit and is further configured as follows: The oxygen concentration in the gas phase balance pipeline is monitored in real time; when the oxygen concentration exceeds a first safety threshold, a safety alarm is generated; and / or, when the oxygen concentration exceeds a higher second safety threshold, a safety intervention action is triggered; the safety intervention action includes: controlling the opening of the injection valve connected to the inert gas source to inject inert gas into the gas phase balance pipeline.

[0078] To ensure the inherent safety of the gas phase space during ammonia unloading and prevent the formation of an explosive atmosphere, the system executes the following safety monitoring procedures: (1) Before and throughout the ammonia unloading operation, the oxygen concentration sensor works continuously, transmitting real-time concentration signals. Transmitted to the intelligent control system.

[0079] (2) The control system has a preset first warning threshold. With the second action threshold ( > The system continuously compares... With threshold: when > When the system determines the situation to be in a warning state, it generates a primary alarm and records it. when > When this occurs, the system determines the situation to be dangerous, immediately generates a high-level alarm, and initiates a safety intervention procedure.

[0080] (3) In a hazardous situation, the control system automatically issues a command to open the injection valve connected between the inert gas source and the gas phase balance pipeline. The inert gas (such as nitrogen) is injected into the pipeline to dilute and replace the gas phase space.

[0081] (4) Continuous monitoring of the control system ,when Falling below The system will remain stable or automatically close the injection valve after a preset injection duration. The alarm status will then change to pending confirmation, requiring manual reset by the operator before the system fully resumes normal monitoring.

[0082] In some embodiments, an environmental sensing unit is also included for collecting ambient temperature and / or wind speed data at the unloading site; The intelligent control system is communicatively connected to the environmental sensing unit and is further configured as follows: Based on the ambient temperature and / or wind speed data, dynamically adjust the parameters in the preset ammonia unloading stop conditions, or the safety parameters related to the gas phase space.

[0083] To address the impact of varying environmental conditions on the safe unloading of ammonia, the system performs the following adaptive optimization steps: The ambient temperature T and wind speed V in the unloading area are collected in real time and processed to obtain characteristic values. and .based on( , The system matches the data in a predefined risk matrix to determine the current environmental risk level (e.g., low, medium, high).

[0084] High temperature and low wind mode: >30°C and <1.0 m / s, identified as high risk; Normal temperature stroke mode: 15°C ≤ ≤ 30°C and 1.0 m / s ≤ ≤ 3.0 m / s, classified as medium risk; Low temperature high wind mode: <15°C and >3.0 m / s, classified as low risk.

[0085] The system pre-stores optimal safety parameter sets corresponding to different environmental risk levels. This mapping relationship is determined based on the physical properties of ammonia (volatility, explosion limits) and environmental hydrodynamics (diffusion conditions). For example: When the risk level is determined to be high (high temperature and no wind), the system will automatically execute: a. Set the ammonia storage tank to the stop receiving level. Reduce from the default value X1 to X2 (X2) <X1)。

[0086] b. The action threshold for gas phase oxygen concentration Reduce from the default value Y1 to Y2 (Y2) <Y1)。

[0087] When the risk level is determined to be low (low temperature and windy), the system can adjust some parameters accordingly to improve efficiency, but still keep them within the absolute safety limits.

[0088] The adjusted parameters take effect immediately and are used for control logic and safety interlocks. The system continuously monitors environmental changes, and automatically triggers a new round of parameter optimization when the risk level changes. Simultaneously, the system records all parameter adjustment events, creating a traceable safety operation profile.

[0089] Based on the determined operating mode, the system dynamically adjusts one or more of the following key parameters: A. Adjust the parameters in the ammonia unloading stop conditions. Preset high stop level for ammonia storage tank Adjust the logic: High-temperature operating conditions: To prevent the ammonia in the storage tank from evaporating rapidly and the gas phase pressure from increasing dramatically due to high temperatures, the operating temperature should be reduced. For example, reducing the percentage from the conventional 85% to 80% allows for more expansion space in the gas phase, and stopping the feed earlier reduces risk.

[0090] Low temperature / high wind conditions: Evaporation is slowed down, so the speed can be appropriately increased. To improve the efficiency of a single uninstallation, but still within absolute safety limits.

[0091] Specific adjustment formula:

[0092] The adjusted high stop liquid level, The default setting is to stop the liquid level. , For reference temperature and wind speed, , The influence coefficients of temperature and wind speed ( For positive, (Possibly negative), determined through engineering experience or simulation.

[0093] final It must be within the preset absolute safety upper and lower limits.

[0094] B. Adjust the safety parameters related to the gas phase space. This mainly involves the previously defined oxygen concentration monitoring thresholds.

[0095] Affected parameter: Warning threshold Action threshold Inertization stop threshold Inerting can be stopped when the concentration is below this value.

[0096] This invention also provides an intelligent ammonia safety unloading control method for tank trucks based on the system described in the above embodiments, executed by the intelligent control system, as described in the above embodiments. Figure 2As shown, the ammonia water inlet to the buffer tank is installed in the following order: quick connector, stainless steel pipe (10cm long), electric ball valve, manual ball valve, stainless steel pipe (length as needed). Normally, the electric ball valve is closed, and the manual ball valve is open for emergency closure. The second section of stainless steel pipe connects to the upper part of the buffer tank, with the distance from the top of the connection point to the top of the buffer tank being 85% of the total height of the buffer tank.

[0097] Buffer tank: ① A vent pipe (DN20) is installed at the top center. The vent pipe is equipped with one electric ball valve and one manual ball valve. The length of the vent pipe should be sufficient to extend 50cm above the ammonia storage tank and the tank truck to prevent ammonia from being discharged from the venting system; ② The buffer tank is equipped with one electronic level gauge. The upper part of the level gauge is flush with the lower edge of the ammonia inlet, and the lower part is flush with the upper edge of the ammonia outlet. The upper limit is set at the upper 15% of the level gauge, and the lower limit is set at the lower 15% of the level gauge; ③ The ammonia outlet of the buffer tank is connected to the ammonia unloading pump using a stainless steel pipe, with one electric ball valve and one manual ball valve installed in the middle.

[0098] From ammonia storage tank to ammonia tanker truck: The ammonia storage tank is equipped with a breather valve and a check valve at the top. A flexible metal hose with the same diameter as the ammonia unloading system is installed outside the check valve. A metal disc is connected to the hose, and this disc should be able to connect to the ammonia filling port on the tanker truck. The breather valve is installed on this gas phase balance pipeline as a safety backup for the system.

[0099] like Figure 3 As shown, the method includes the following steps: S1. Open the electric valve of the inlet pipeline and the exhaust valve of the buffer tank to allow ammonia water to flow into the buffer tank under the action of pressure difference; S2. When the buffer tank level reaches the first preset level, close the exhaust valve, open the outlet pipeline electric valve and start the ammonia unloading pump to transfer the ammonia water to the ammonia water storage tank. S3. During the buffer transfer phase, at least one of the following shall be executed in parallel: Based on the real-time liquid level in the buffer tank and the pressure difference between the tank truck and the buffer tank, the speed of the ammonia unloading pump is dynamically adjusted to keep the liquid level stable in the second preset liquid level range. The gas composition in the gas phase balance pipeline is monitored in real time. If the oxygen concentration exceeds the limit, an alarm or inerting protection action is triggered. S4. Monitor whether the preset stop conditions are met. If they are met, execute the stop procedure. After the stop procedure, perform the residual liquid recovery operation.

[0100] The stopping condition is: the liquid level in the ammonia storage tank reaches a preset high level, or the liquid level in the buffer tank drops to a preset low threshold. The shutdown procedure includes: opening the buffer tank vent valve, closing the electric valve of the inlet pipeline, waiting for the buffer tank liquid level to drop to the preset low threshold, closing the buffer tank outlet valve and the ammonia unloading pump, and finally closing the buffer tank vent valve. The residual liquid recovery operation is as follows: after closing the inlet valve of the buffer tank, reopen the valve to allow the residual ammonia in the connecting pipeline to flow into the buffer tank by gravity, and then close the valve again.

[0101] In this embodiment of the invention, firstly, the metal hose is manually connected to the quick-connect interface at the inlet of the buffer tank, and an ammonia leak detection device is used to verify that there is no leak. Secondly, the top of the tanker truck is opened, and it is connected to the vent valve disc of the ammonia storage tank. The "Automatic Ammonia Unloading" button on the upper part of the control box is clicked. The system first opens the inlet ball valve of the buffer tank and the vent ball valve at the top of the buffer tank. When the liquid level in the buffer tank rises to 20% of the upper level gauge, the vent valve at the top of the buffer tank is closed, the ball valve between the buffer tank and the ammonia unloading pump is opened, and the ammonia unloading pump is started. When the liquid level reaches the upper limit, the control system treats it as a high-high alarm and interlocks to shut down the inlet electric valve of the buffer tank and the ammonia unloading pump.

[0102] (1) When the ammonia water storage tank level gauge reaches 85% of the tank height, first open the vent valve at the top of the buffer tank, then close the inlet ball valve of the buffer tank. When the level gauge of the buffer tank reaches the lower limit, close the ball valve between the buffer tank and the ammonia unloading pump, then close the ammonia unloading pump and close the vent valve at the top of the buffer tank.

[0103] (2) When the level gauge of the buffer tank reaches the lower limit, it means that the tank truck has been emptied and the relevant procedure (1) is executed.

[0104] After the ammonia unloading is completed, (a) open the inlet ball valve of the buffer tank and manually unload the residual ammonia water in the metal hose between the tank truck and the buffer tank into the buffer tank. Then disconnect the metal hose joint and check the residual ammonia water again. If it has been unloaded, close the inlet electric butterfly valve of the buffer tank.

[0105] (b) Disconnect the exhaust system disc of the ammonia storage tank from the top of the tank truck, close the ammonia inlet at the top of the tank truck, and place the exhaust system disc in a special water tank or pool to absorb ammonia vapor and prevent ammonia vapor from overflowing under normal circumstances.

[0106] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium such as a USB flash drive, mobile hard drive, read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk, or other media capable of storing program code. It includes several instructions to cause a computer terminal (which may be a personal computer, server, or a second terminal, network terminal, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0107] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0108] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0109] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0110] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An intelligent ammonia safety unloading system for tank trucks, characterized in that, include: The buffer tank is connected to the tank truck via an inlet pipeline and to the ammonia storage tank via an outlet pipeline and an ammonia unloading pump. A gas phase balance pipeline is connected between the top of the ammonia storage tank and the top of the tank truck to establish and maintain gas phase pressure balance between the ammonia storage tank and the tank truck during the ammonia unloading process. An electronic level gauge is installed on the buffer tank to monitor its internal liquid level; Multiple electric valves are installed at least on the inlet pipe, outlet pipe, and exhaust port pipe of the buffer tank; The intelligent control system is communicatively connected to the electronic level gauge, the ammonia unloading pump, and each electric valve. The intelligent control system is configured as follows: Based on the liquid level information fed back by the electronic level gauge, the buffer tank is controlled to alternately perform liquid inlet buffering operation and transfer discharge operation. The liquid inlet buffering operation includes opening the inlet pipeline electric valve to allow ammonia water to flow from the tank truck into the buffer tank. The transfer discharge operation includes opening the outlet pipeline electric valve and starting the ammonia unloading pump to transport the ammonia water in the buffer tank to the ammonia water storage tank. When the preset ammonia unloading stop condition is met, a stop procedure is executed. The stop procedure includes at least closing the inlet pipeline electric valve to stop liquid inlet. After executing the stop procedure, a residual liquid recovery operation is performed. The residual liquid recovery operation includes reopening the inlet pipeline electric valve to allow the residual ammonia water remaining in the inlet pipeline to flow into the buffer tank.

2. The intelligent ammonia safety unloading system for tank trucks according to claim 1, characterized in that, It also includes a pressure sensing unit for monitoring the pressure difference between the tank truck and the buffer tank; The intelligent control system is communicatively connected to the pressure sensing unit and is further configured as follows: Based on the real-time liquid level data of the electronic liquid level gauge and the differential pressure data of the pressure sensing unit, the speed of the ammonia unloading pump or the opening of the electric valve of the outlet pipeline is dynamically adjusted to stably control the liquid level of the buffer tank within the preset target working range. The intelligent control system pre-stores or learns the differential pressure-flow characteristic relationship of the inlet pipeline system to estimate the inlet flow rate based on the real-time differential pressure; the intelligent control system pre-stores or learns the pump speed-flow characteristic curve of the ammonia unloading pump in the outlet pipeline system to estimate the outlet flow rate based on the speed setpoint or to deduce the speed setpoint based on the target outlet flow rate.

3. The intelligent ammonia safety unloading system for tank trucks according to claim 2, characterized in that, The intelligent control system is specifically configured as follows: Based on the rate of change of liquid level fed back by the electronic level gauge and the differential pressure data of the pressure sensing unit, the time when the liquid level in the buffer tank reaches the preset high limit or low limit is predicted. Based on the predicted time, the speed of the ammonia unloading pump is adjusted in advance through a feedforward-feedback composite control algorithm to suppress overshoot and drastic fluctuations in the buffer tank level. The feedforward-feedback composite control algorithm includes: calculating the flow imbalance estimate based on the inlet flow rate estimated according to the differential pressure-flow characteristic relationship and the outlet flow rate estimated according to the pump speed-flow characteristic curve, generating a feedforward control quantity based on this estimate, and then outputting it after superimposing it with the feedback control quantity based on the liquid level deviation.

4. The intelligent ammonia safety unloading system for tank trucks according to claim 1, characterized in that, It also includes a gas analysis unit, which is installed on the gas phase balance pipeline to monitor the oxygen concentration in the pipeline; The intelligent control system is communicatively connected to the gas analysis unit and is further configured as follows: The oxygen concentration in the gas phase balance pipeline is monitored in real time; when the oxygen concentration exceeds the first safety threshold, a safety alarm is generated. And / or, when the oxygen concentration exceeds a higher second safety threshold, a safety intervention action is triggered; the safety intervention action includes: controlling the opening of an injection valve connected to an inert gas source to inject inert gas into the gas phase balance pipeline.

5. The intelligent ammonia safety unloading system for tank trucks according to claim 1, characterized in that, It also includes an environmental sensing unit for collecting ambient temperature and / or wind speed data at the unloading site; The intelligent control system is communicatively connected to the environmental sensing unit and is further configured as follows: Based on the ambient temperature and / or wind speed data, dynamically adjust the parameters in the preset ammonia unloading stop conditions, or the safety parameters related to the gas phase space.

6. The intelligent ammonia safety unloading system for tank trucks according to claim 1, characterized in that, The gas phase balance pipeline is equipped with a check valve to prevent gas from flowing back from the tank truck into the ammonia storage tank. The buffer tank has an exhaust port connected to an upward-extending exhaust pipe, the outlet height of which is configured to be higher than the ammonia storage tank and the tank truck.

7. The intelligent ammonia safety unloading system for tank trucks according to claim 1, characterized in that, The inlet of the buffer tank is located at the top of the tank body, and the upper detection point of the electronic level gauge is not lower than the lower edge of the inlet, and the lower detection point of the electronic level gauge is not higher than the upper edge of the outlet of the buffer tank; the intelligent control system is preset with a high-level threshold and a low-level threshold based on the electronic level gauge.

8. The intelligent ammonia safety unloading system for tank trucks according to claim 1, characterized in that, The inlet of the buffer tank is connected to the inlet pipe through an inlet pipe that extends into the tank body. The distance from the outlet end of the inlet pipe to the top of the buffer tank is 75%-95% of the total height of the buffer tank.

9. A smart ammonia safety unloading control method for tank trucks based on the system described in any one of claims 3-8, characterized in that, The intelligent control system performs the following steps: S1. Open the electric valve of the inlet pipeline and the exhaust valve of the buffer tank to allow ammonia water to flow into the buffer tank under the action of pressure difference; S2. When the buffer tank level reaches the first preset level, close the exhaust valve, open the outlet pipeline electric valve and start the ammonia unloading pump to transfer the ammonia water to the ammonia water storage tank. S3. During the buffer transfer phase, at least one of the following shall be executed in parallel: Based on the real-time liquid level in the buffer tank and the pressure difference between the tank truck and the buffer tank, the speed of the ammonia unloading pump is dynamically adjusted to keep the liquid level stable in the second preset liquid level range. The gas composition in the gas phase balance pipeline is monitored in real time. If the oxygen concentration exceeds the limit, an alarm or inerting protection action is triggered. S4. Monitor whether the preset stop conditions are met. If they are met, execute the stop procedure. After the stop procedure, perform the residual liquid recovery operation.

10. The intelligent ammonia water safety unloading control method for tank trucks according to claim 9, characterized in that, The stopping condition is: the liquid level in the ammonia storage tank reaches a preset high level, or the liquid level in the buffer tank drops to a preset low threshold. The shutdown procedure includes: opening the buffer tank vent valve, closing the electric valve of the inlet pipeline, waiting for the buffer tank liquid level to drop to the preset low threshold, closing the buffer tank outlet valve and the ammonia unloading pump, and finally closing the buffer tank vent valve. The residual liquid recovery operation is as follows: after closing the inlet valve of the buffer tank, reopen the valve to allow the residual ammonia in the connecting pipeline to flow into the buffer tank by gravity, and then close the valve again.

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