A safe pressurization method and system based on a krypton-xenon-lean liquid storage tank with an evaporator

Abstract

The application discloses a kind of based on poor krypton-xenon liquid storage tank with evaporator's safe pressurization method and system, the method includes: S1 control nitrogen output unit to liquid evaporator and storage tank gas phase space with nitrogen;S2 control the initial opening of liquid evaporator feed valve, so that poor krypton-xenon liquid in poor krypton-xenon liquid storage tank is imported into evaporator, let poor krypton-xenon liquid vaporize in evaporator;S3 adjust the amount of nitrogen and the opening of feed valve, dilute after gas phase, so that the concentration of hydrocarbon is always lower than preset safety threshold;S4 after dilution gas phase is sent into storage tank gas phase space by reflux pipeline;S5 open storage tank filling valve and fill tank car;During the filling process, adjust the liquid phase feed amount of evaporator and the amount of nitrogen, so that the pressure of storage tank is stabilized in preset target filling pressure range.The original self-pressurization process with evaporator is reformed, and the safety factor of pressurized filling is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of filling of lean krypton-xenon liquid storage tanks, and particularly relates to a safety pressurization method and system based on an evaporator自带 by a lean krypton-xenon liquid storage tank. Background Art

[0002] Krypton and xenon belong to rare and precious gases in the air. Due to their unique physical and chemical properties, they are widely used in national strategic emerging industrial fields such as semiconductor etching, aerospace propulsion, medical anesthesia, high-end electric light sources, and deep space exploration, and are known as "air gold". Lean krypton-xenon liquid is the core intermediate material for extracting high-purity krypton and xenon products by large air separation plants. It is usually stored in a cryogenic adiabatic storage tank. In the material transfer and purification feeding processes, the storage tank must be pressurized first, and the lean krypton-xenon liquid is pressed into a tank truck or a purification device through a pressure difference. Therefore, storage tank pressurization is an essential key process in the whole process of lean krypton-xenon liquid storage and transportation.

[0003] The self-pressurization process of the evaporator自带 by the storage tank is the most widely used conventional process in the industry at present. This process uses an internal or external liquid evaporator配套 with the storage tank to draw a small amount of low-temperature lean krypton-xenon liquid from the bottom of the storage tank into the evaporator, and exchanges heat and vaporizes with the low-temperature liquid through ambient air or a water bath. The vaporized krypton-xenon gas phase flows back to the gas phase space at the top of the storage tank, and uses the volume expansion effect after liquid vaporization to increase the internal pressure of the storage tank until the working pressure required for filling is reached, and finally completes liquid filling through a pressure difference. This process has the advantages of simple equipment structure, no need for external gas source matching, and simple operation process, and is the mainstream pressurization design scheme for cryogenic liquid storage tanks at present.

[0004] However, lean krypton-xenon liquid inevitably contains hydrocarbon combustible impurities such as methane and total hydrogen. The saturated vapor pressures of these light components are much higher than those of krypton and xenon heavy components. During the liquid vaporization process, methane and hydrogen will be preferentially released in large quantities and flow back to the gas phase space of the storage tank with the gas phase; and during the self-pressurization process, the pressure of the storage tank continues to rise, which further exacerbates the continuous enrichment of hydrocarbon components in the limited gas phase space, and it is very easy to reach the explosion lower limit (LEL) of methane and hydrogen. In case of ignition sources such as static electricity and frictional sparks, an explosion accident will occur, which is a major safety risk source in the storage and transportation of rare gases in the air separation industry. There have been many explosion and equipment damage accidents caused by hydrocarbon aggregation during the self-pressurization of krypton-xenon storage tanks in China, resulting in serious economic losses and risks of casualties. In addition, the conventional self-pressurization process also has secondary problems such as uncontrollable vaporization process that is prone to cause liquid flashing, pipeline water hammer, thermal stress fatigue damage of the evaporator, and product component fluctuations during the filling process, which seriously affect the service life of the equipment and the product quality. Summary of the Invention

[0005] The purpose of this invention is to provide a safe pressurization method and system based on a krypton-xenon liquid storage tank with an integrated evaporator, which partially solves or alleviates the above-mentioned deficiencies in the prior art. It modifies the original self-pressurization process with an integrated evaporator, thereby significantly improving the safety factor of pressurization and filling.

[0006] To solve the aforementioned technical problems, the present invention specifically adopts the following technical solution: A first aspect of the present invention is to provide a safe pressurization method based on an evaporator integrated into a krypton-xenon liquid storage tank, comprising: S1 closes the feed valve of the liquid evaporator and opens the booster valve; controls the nitrogen output unit to introduce nitrogen into the liquid evaporator and the gas phase space of the storage tank until the oxygen content and hydrocarbon concentration in the gas phase space of the storage tank drop below the preset safety threshold. S2 controls the initial opening of the feed valve of the liquid evaporator, allowing the lean krypton xenon liquid in the lean krypton xenon liquid storage tank to be introduced into the evaporator, so that the lean krypton xenon liquid is vaporized in the evaporator. S3 adjusts the nitrogen flow rate and the opening of the feed valve to dilute the vaporized gas phase, ensuring that the hydrocarbon concentration remains below the preset safety threshold. S4 sends the diluted gas phase into the gas phase space of the storage tank through the reflux pipeline until the gas phase space of the storage tank reaches the preset target filling pressure range. S5 Once the storage tank pressure stabilizes to the preset target filling pressure range, open the storage tank filling valve to fill the tank truck; during the filling process, adjust the liquid phase feed rate and nitrogen flow rate of the evaporator to keep the storage tank pressure stable within the preset target filling pressure range. After S6 is filled, close the filling valve and cut off the liquid phase feed to the evaporator; continuously introduce nitrogen to purge and dilute the evaporator and return pipeline. After purging, close the feed valve and pressure valve and stop introducing nitrogen into the evaporator.

[0007] Furthermore, the initial opening of the feed valve of the liquid evaporator is controlled using the formula:

[0008] Calculate the optimal initial opening of the feed valve; where K init For the optimal initial opening of the feed valve, K rated P is the rated opening of the feed valve. set For the target filling pressure of the storage tank, P tank0 V is the initial gas phase pressure of the storage tank. gas C is the volume of the gas phase space of the storage tank. feed T represents the total hydrocarbon concentration of the original solution. env For ambient temperature, T feed T represents the temperature of the original solution. max is the maximum allowable wall temperature of the evaporator, and a, b, and c are pre-calibrated weighting coefficients.

[0009] Furthermore, the hard constraint condition for the optimal initial opening is: 3%K rated ≤K init ≤12%K rated .

[0010] Furthermore, methods for adjusting the nitrogen flow rate and the opening degree of the feed valve include: The combined concentrations of methane and total hydrogen in the evaporator outlet gas phase are predicted, and the feedforward nitrogen flow rate is calculated based on the predicted hydrocarbon component concentrations. Based on the real-time collected data on the hydrocarbon concentration of the raw liquid, the real-time pressure of the storage tank, and the real-time pressurization rate, the maximum allowable heat exchange temperature difference between the evaporator wall and the lean krypton xenon raw liquid is calculated. Based on the deviation between the real-time heat exchange temperature difference and the maximum allowable heat exchange temperature difference, the upper limit of the constraint on the opening of the evaporator feed valve is calculated. The feedforward flow rate of nitrogen and the upper limit of the evaporator feed valve opening are input into a pre-built cascade control architecture, thereby outputting control parameters for the evaporator feed valve opening and the nitrogen flow rate, and controlling the evaporator feed valve and nitrogen flow according to the control parameters.

[0011] Furthermore, the combined concentrations of methane and total hydrogen in the evaporator outlet gas phase are predicted using a pre-constructed krypton-xenon hydrocarbon evolution model; the krypton-xenon hydrocarbon evolution model is as follows: ; ; in, The real-time evolution rate of methane and total hydrogen is given by , k is the system correction factor, and F... feed P is the liquid phase feed rate of the evaporator. wal l is the saturated vapor pressure at the corresponding temperature of the evaporator wall, P sat,CH Let E be the saturated vapor pressure of the hydrocarbon component at the current temperature, E be the activation energy of the hydrocarbon component's vaporization, R be the gas constant, and T be the saturated vapor pressure of the hydrocarbon component at the current temperature. wall T represents the real-time wall temperature of the evaporator. feed For the temperature of the krypton-depleted xenon stock solution, C CH,pred (t+n) represents the predicted combined hydrocarbon concentration in the evaporator outlet gas phase over the next n seconds, C CH,real (t) represents the measured value of hydrocarbon concentration at the current moment.

[0012] Furthermore, using the formula:

[0013] Calculate the maximum allowable heat transfer temperature difference; where ΔT max ΔT is the maximum allowable heat transfer temperature difference. base Based on the temperature difference, LEL realC represents the real-time lower limit of explosion under the current operating conditions. feed P represents the total hydrocarbon concentration of the krypton-depleted xenon stock solution. set To achieve the target filling pressure, P tank denoted as ρ, where ρ is the real-time pressure of the storage tank, |dP / dt| is the absolute value of the real-time pressure increase rate, and α, β, and γ are pre-calibrated weighting coefficients.

[0014] Furthermore, methods for calculating the upper limit constraint on the evaporator feed valve opening include: When the real-time heat exchange temperature difference ΔT real ≤0.8ΔT max At this time, the upper limit of the feed valve opening is 15% of the rated opening; When 0.8ΔT max <ΔT real ≤0.9ΔT max At this time, the upper limit of the feed valve opening is 8% of the rated opening; When 0.9ΔT max <ΔT real ≤ΔT max At this time, the upper limit of the feed valve opening is 5% of the rated opening; When ΔT real >ΔT max When the time comes, close the feed valve.

[0015] Furthermore, the cascade control architecture is a main-sub-loop cascade control architecture. The main loop takes the target filling pressure of the storage tank and the preset safe pressurization rate as the control targets and outputs the evaporator feed valve opening setting value. The sub-loop takes the hydrocarbon concentration safety threshold as the control target and outputs the nitrogen output unit outlet valve opening setting value.

[0016] Furthermore, the preset target filling pressure range for the storage tank is 0.38~0.42MPa; the preset maximum allowable pressurization rate is ≤0.01MPa / min; the preset hydrocarbon concentration safety threshold is ≤20% for the lower explosive limit (LEL) of methane and total hydrogen, and the oxygen content safety threshold is ≤2%.

[0017] Furthermore, in step S6, after the liquid phase feed is cut off, the purging time of continuously introducing high-purity nitrogen gas is ≥30s.

[0018] This invention also provides a safety pressurization system based on a lean krypton xenon liquid storage tank with an integrated evaporator. The lean krypton xenon liquid storage tank is equipped with a liquid evaporator. The liquid phase inlet of the liquid evaporator is connected to the liquid phase zone of the lean krypton xenon liquid storage tank via a feed pipe, and the gas phase outlet of the liquid evaporator is connected to the gas phase space of the lean krypton xenon liquid storage tank via a return pipe. The feed pipe is equipped with a feed valve, and the return pipe is equipped with a pressurization valve. The system also includes a nitrogen output unit connected to the liquid evaporator, which is equipped with an outlet valve. It also includes a controller, which is configured to: Close the feed valve of the liquid evaporator and open the pressure boosting valve; control the nitrogen output unit to introduce nitrogen into the liquid evaporator and the gas phase space of the storage tank until the oxygen content and hydrocarbon concentration in the gas phase space of the storage tank drop below the preset safety threshold. Control the initial opening of the feed valve of the liquid evaporator so that the lean krypton xenon liquid in the lean krypton xenon liquid storage tank is introduced into the evaporator, and the lean krypton xenon liquid is vaporized in the evaporator. Adjusting the nitrogen flow rate and the opening of the feed valve dilutes the vaporized gas phase, ensuring that the hydrocarbon concentration remains below the preset safety threshold. The diluted gas phase is sent into the gas phase space of the storage tank through the reflux pipeline until the gas phase space of the storage tank reaches the preset target filling pressure range. Once the storage tank pressure stabilizes to the preset target filling pressure range, open the storage tank filling valve to fill the tank truck; during the filling process, adjust the liquid phase feed rate and nitrogen flow rate of the evaporator to keep the storage tank pressure stable within the preset target filling pressure range; continuously monitor the hydrocarbon component concentration at the evaporator outlet and in the gas phase space of the storage tank to ensure that it is always within the safe threshold. After filling is completed, close the filling valve and cut off the liquid phase feed to the evaporator; continuously introduce nitrogen to purge and dilute the evaporator and return pipeline. After purging is completed, close the feed valve and pressure valve and stop introducing nitrogen into the evaporator.

[0019] Beneficial effects: This invention reduces the oxygen content of the system to below the limiting oxygen concentrations of methane and hydrogen by nitrogen replacement before the lean krypton xenon feedstock enters the evaporator, eliminating the oxidizing agent condition, one of the three elements of an explosion. The vaporized carbon-rich hydrogen phase is diluted online before entering the storage tank, and the hydrocarbon concentration is controlled to ≤15% LEL throughout the process, fundamentally preventing the possibility of combustible components accumulating in the storage tank to form an explosive gas mixture.

[0020] This invention suppresses the large-scale precipitation of hydrocarbon components from the feed source by using dynamic heat exchange temperature difference constraint; it predicts concentration changes 30 seconds in advance by using a hydrocarbon precipitation kinetic model, thus solving the industry safety blind spot of 15-30 seconds detection lag in online gas chromatographs; and it achieves precise concentration control through safety-first closed-loop control, with triple protection layer by layer, leaving no dead ends in safety control. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the present invention.

[0023] Summary of attached labeling and identification: 1. Lean krypton xenon liquid storage tank; 2. Liquid evaporator; 3. Nitrogen output unit; 21. Evaporation section; 22. Mixing section; 23. Pressure boosting valve; 24. Feed valve; 31. Outlet valve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] In this document, suffixes such as "module," "part," or "unit" used to denote elements are used only for the purpose of illustrative purposes and have no specific meaning in themselves. Therefore, "module," "part," or "unit" may be used interchangeably.

[0026] In this document, the terms "upper," "lower," "inner," "outer," "front," "rear," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In this document, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0029] In this article, "multiple" means two or more, that is, it includes two, three, four, five, etc.

[0030] Example 1: like Figure 1 As shown, this embodiment provides a safe pressurization method based on a lean krypton xenon liquid storage tank with an integrated evaporator, deployed on the lean krypton xenon liquid storage tank with an integrated evaporator. The lean krypton xenon liquid storage tank 1 is equipped with a liquid evaporator 2. The liquid phase inlet of the liquid evaporator 2 is connected to the liquid phase zone of the lean krypton xenon liquid storage tank 1 through a feed pipe, and the gas phase outlet of the liquid evaporator 2 is connected to the gas phase space of the lean krypton xenon liquid storage tank 1 through a return pipe. The feed pipe is equipped with a feed valve 24, and the return pipe is equipped with a pressurization valve 23. It also includes a nitrogen output unit 3 connected to the liquid evaporator 2, and the nitrogen output unit 3 is equipped with an outlet valve 31.

[0031] More specifically, the liquid evaporator 2 includes an evaporation section 21 and a mixing section 22; wherein the evaporation section 21 is used to evaporate lean krypton xenon from the liquid phase to the gas phase, and the mixing section 22 is used to mix with nitrogen for dilution. Predictably, the nitrogen output unit 3 is connected to the mixing section 22 of the liquid evaporator 2.

[0032] In this embodiment, the specific steps of the safe pressurization method include: S1 closes the feed valve of the liquid evaporator and opens the booster valve; controls the nitrogen output unit to introduce nitrogen into the liquid evaporator and the gas phase space of the storage tank until the oxygen content and hydrocarbon concentration in the gas phase space of the storage tank drop below the preset safety threshold.

[0033] Specifically, in this embodiment, the preset safety threshold for hydrocarbon concentration is ≤20% for the lower explosive limit (LEL) of methane and total hydrogen, and the safety threshold for oxygen content is ≤2%.

[0034] S2 controls the initial opening of the feed valve of the liquid evaporator, allowing the lean krypton xenon liquid in the lean krypton xenon liquid storage tank to be introduced into the evaporator, where the lean krypton xenon liquid is vaporized.

[0035] The purpose of this step is to replace the existing technology's extensive mode of manually opening valves and feeding at a fixed opening by precisely quantifying and controlling the initial opening degree through full-condition adaptive control. This allows the system to enter a mild vaporization state from the beginning of vaporization while also taking into account pressurization efficiency, thereby suppressing the instantaneous large-scale precipitation of hydrocarbon light components such as methane and total hydrogen from the source.

[0036] Specifically, this embodiment utilizes the following formula:

[0037] Calculate the optimal initial opening of the feed valve; where K init For the optimal initial opening of the feed valve, K rated P is the rated opening of the feed valve. set For the target filling pressure of the storage tank, P tank0 V is the initial gas phase pressure of the storage tank. gas C is the volume of the gas phase space of the storage tank. feed T represents the total hydrocarbon concentration of the original solution. env For ambient temperature, T feed T represents the temperature of the original solution. max is the maximum allowable wall temperature of the evaporator, and a, b, and c are pre-calibrated weighting coefficients.

[0038] It is worth noting that regardless of the model's calculation results, the final output initial aperture must strictly adhere to the following hard constraint: 3%K. rated ≤K init ≤12%K rated . The reason for setting a lower limit of 3% of the rated opening is to avoid the valve opening being too small, resulting in a throttling state, which could lead to unstable feed flow, flashing, air blockage, pipeline vibration, and other problems, thus ensuring stable feed. The reason for setting an upper limit of 12% of the rated opening is that even for raw liquids with extremely low hydrocarbon concentrations, exceeding this opening will lead to excessive vaporization, and the hydrocarbon evolution rate will exceed the nitrogen dilution capacity. This algorithmically eliminates the risk of large-flow feed and is a safety limit that cannot be exceeded.

[0039] S3 adjusts the nitrogen flow rate and the opening of the feed valve to dilute the vaporized gas phase, ensuring that the hydrocarbon concentration remains below a preset safety threshold. Specifically, this includes: S31 predicts the combined concentration of methane and total hydrogen in the gas phase at the evaporator outlet, and calculates the feedforward rate of nitrogen based on the predicted hydrocarbon component concentration.

[0040] The 15-30 second detection lag in online gas chromatographs creates a safety management blind spot. Current technology requires waiting for the chromatogram to detect excessive concentrations before adjusting the nitrogen dilution rate. By this time, the carbon-rich hydrogen gas phase has already flowed back into the storage tank's gas phase space, creating a risk window for an explosive gas mixture. This new step predicts the combined methane and total hydrogen concentration in the evaporator outlet gas phase 30 seconds in advance and pre-adjusts the nitrogen flow rate, fundamentally eliminating the safety risks caused by the detection lag.

[0041] Specifically, in this embodiment, the combined concentrations of methane and total hydrogen in the evaporator outlet gas phase are predicted using a pre-constructed krypton-xenon hydrocarbon evolution model; the krypton-xenon hydrocarbon evolution model is as follows: ; ; in, The real-time evolution rate of methane and total hydrogen is given by , k is the system correction factor, and F... feed P is the liquid phase feed rate of the evaporator. wal l is the saturated vapor pressure at the corresponding temperature of the evaporator wall, P sat,CH Let E be the saturated vapor pressure of the hydrocarbon component at the current temperature, E be the activation energy of the hydrocarbon component's vaporization, R be the gas constant, and T be the saturated vapor pressure of the hydrocarbon component at the current temperature. wall T represents the real-time wall temperature of the evaporator. feed For the temperature of the krypton-depleted xenon stock solution, C CH,pred (t+n) represents the predicted combined hydrocarbon concentration in the evaporator outlet gas phase over the next n seconds, C CH,real (t) represents the measured value of hydrocarbon concentration at the current moment. In this embodiment, n is 30 seconds.

[0042] Based on the predicted concentrations above, the required dilution nitrogen flow rate is calculated in advance to ensure that the diluted gaseous hydrocarbon concentration is always controlled within 15% LEL, with a safety margin of 5% LEL and a safety threshold of 20% LEL. The calculation formula is as follows: ; Among them, F N2,ff This refers to the nitrogen feedforward flow rate, i.e., the reference opening value of the dilution nitrogen regulating valve; F gas The real-time flow rate of the vaporized gas phase in the evaporator is calculated in real time from the feed flow rate and the heat exchange temperature difference; C set The hydrocarbon concentration setting is fixed at 15% LEL.

[0043] In this step, real-time data on feed flow rate, evaporator wall temperature, feed liquid temperature, and feed liquid hydrocarbon concentration are collected and input into the model to predict the hydrocarbon concentration at the evaporator outlet 30 seconds in advance. Based on the predicted concentration, the nitrogen feedforward flow rate is calculated, and the opening of the dilution nitrogen electric regulating valve is adjusted in advance, completing the pre-adjustment of the dilution gas flow rate before the hydrocarbon components are analyzed. After the chromatograph outputs the measured concentration, the deviation between the measured value and the predicted value is used to correct the model's correction coefficient k online, achieving self-learning optimization of the model and continuously improving prediction accuracy. If the predicted concentration exceeds 15% LEL, the nitrogen flow rate is immediately forcibly increased without waiting for the chromatographic measurement results, simultaneously triggering the next step to tighten the upper limit of the feed valve opening constraint, achieving dual pre-control.

[0044] Based on real-time data collection of the raw liquid hydrocarbon concentration, storage tank pressure, and pressurization rate, S32 calculates the maximum allowable heat exchange temperature difference between the evaporator wall and the lean krypton xenon raw liquid. Based on the deviation between the real-time heat exchange temperature difference and the maximum allowable heat exchange temperature difference, it calculates the upper limit of the constraint on the opening of the evaporator feed valve.

[0045] The purpose of this step is to dynamically calculate the maximum allowable heat exchange temperature difference under the current operating conditions through a multi-parameter coupled model, replacing the fixed hard constraint. At the same time, based on the temperature difference deviation, the safety upper limit of the feed valve opening is locked in real time, controlling the vaporization intensity from the feed source and suppressing the large-scale precipitation of hydrocarbon components.

[0046] Specifically, this embodiment utilizes the following formula:

[0047] Calculate the maximum allowable heat transfer temperature difference; where ΔT max ΔT is the maximum allowable heat transfer temperature difference. base Based on the temperature difference, LEL real C represents the real-time lower limit of explosion under the current operating conditions. feed P represents the total hydrocarbon concentration of the krypton-depleted xenon stock solution. set To achieve the target filling pressure, P tank denoted as ρ, where ρ is the real-time pressure of the storage tank, |dP / dt| is the absolute value of the real-time pressure increase rate, and α, β, and γ are pre-calibrated weighting coefficients.

[0048] It is worth noting that, regardless of the model's calculation results, the final maximum allowable heat transfer temperature difference must strictly adhere to the following hard constraint: 15℃ ≤ ΔT max ≤35℃ The lower limit of 15°C is set to avoid insufficient vaporization due to a small temperature difference, which would fail to meet the pressure boosting requirements. The upper limit of 35°C is set because even if the hydrocarbon concentration of the raw liquid is extremely low, this temperature difference must never be exceeded to prevent local overheating that could lead to violent vaporization of the raw liquid, hydrocarbon cracking, and thermal stress damage to the equipment.

[0049] Based on the deviation between the real-time heat exchange temperature difference and the maximum allowable temperature difference, the safe upper limit of the feed valve opening is dynamically calculated, specifically including: When the real-time heat exchange temperature difference ΔT real ≤0.8ΔT max At this time, the upper limit of the feed valve opening is 15% of the rated opening, leaving sufficient space for pressure adjustment.

[0050] When 0.8ΔT max <ΔT real ≤0.9ΔT max At this time, the upper limit of the feed valve opening is linearly reduced, gradually decreasing from 15% of the rated opening to 8% of the rated opening, thus tightening the constraint in advance.

[0051] When 0.9ΔT max <ΔT real ≤ΔT max At this time, the upper limit of the feed valve opening is locked at 5% of the rated opening, and it is forbidden to continue to open the valve further. At the same time, the valve is slightly closed to reduce the feed rate. When ΔT real >ΔT max At this time, the feed valve is forcibly closed to stop feeding, and the dilution nitrogen valve is simultaneously fully opened to purge until the temperature difference returns to the safe range.

[0052] S33 inputs the feedforward nitrogen flow rate and the upper limit constraint of the evaporator feed valve opening into the pre-built cascade control architecture, thereby outputting control parameters for the evaporator feed valve opening and the nitrogen flow rate, and controlling the evaporator feed valve and nitrogen flow rate according to the control parameters.

[0053] The purpose of this step is to integrate the feedforward nitrogen quantity obtained in step S31 with the upper limit constraint of the feed valve obtained in step S32, so as to achieve decoupled control of pressure and concentration. At the same time, the parameters are adaptively tuned through fuzzy PID, and finally the valve control parameters are output to complete the closed-loop execution.

[0054] Specifically, the cascade control architecture described in this embodiment is a main-sub-loop cascade control architecture. The main loop takes the target filling pressure of the storage tank and the preset safe pressurization rate as the control targets and outputs the set value of the evaporator feed valve opening. The sub-loop takes the safe threshold of hydrocarbon concentration as the control target and outputs the set value of the nitrogen output unit outlet valve opening.

[0055] The nitrogen feedforward input output from S31 is used as the feedforward reference value of the secondary loop, and the upper limit of the feed valve opening constraint output from S32 is used as the hard constraint boundary of the main loop, which is then input into the cascade control architecture. The main loop control logic uses the deviation between the target pressure and the real-time pressure in the storage tank, and the deviation between the target pressure increase rate and the real-time pressure increase rate as inputs, to calculate the basic set value of the feed valve opening through a fuzzy PID controller. If the calculated opening set value exceeds the upper limit of the constraint in S32, the set value is automatically corrected to the upper limit of the constraint, and the safety boundary is absolutely not allowed to be exceeded. A variable step size adjustment rule is adopted, and the maximum adjustment range of the valve opening in a single operation does not exceed 2% of the rated opening.

[0056] The secondary loop control logic uses the feedforward nitrogen quantity of S31 as the base setpoint and the deviation between the hydrocarbon concentration setpoint and the real-time measured value as the feedback input. The final nitrogen regulating valve opening setpoint is calculated through a fuzzy PID controller. When the real-time hydrocarbon concentration exceeds 18% LEL, a high-priority intervention is immediately triggered, forcing the nitrogen regulating valve to fully open to increase the dilution amount. At the same time, a locking command is sent to the main loop to prevent the feed valve opening from increasing further. When the real-time hydrocarbon concentration exceeds 20% LEL, a valve closing command is immediately sent to the main loop to forcibly close the feed valve.

[0057] The main loop outputs the final feed valve opening control parameters, and the secondary loop outputs the final nitrogen regulating valve opening control parameters. These parameters are simultaneously sent to the corresponding electric actuators to complete one closed-loop control cycle. At the same time, the execution results are fed back to steps S31 and S32 to enter the next calculation cycle.

[0058] S4 sends the diluted gas phase into the gas phase space of the storage tank through the reflux pipeline until the gas phase space of the storage tank reaches the preset target filling pressure range.

[0059] In this embodiment, the preset target filling pressure range for the storage tank is 0.38~0.42MPa.

[0060] S5 Once the storage tank pressure stabilizes to the preset target filling pressure range, open the storage tank filling valve to fill the tank truck; during the filling process, adjust the liquid phase feed rate and nitrogen flow rate of the evaporator so that the storage tank pressure stabilizes within the preset target filling pressure range.

[0061] During the filling process, the pressure in the storage tank is maintained stable within the preset target filling pressure range. The filling port valve of the storage tank is opened to fill the tank truck. During the filling process, the control system monitors the rate of drop in the liquid level in the storage tank, the pressure fluctuation in the storage tank, and the change in the back pressure of the tank truck in real time, and dynamically adjusts the vaporization amount and nitrogen dilution amount to compensate for the pressure loss during the filling process and avoid flash evaporation and water hammer caused by pressure fluctuations.

[0062] Throughout the filling process, the hydrocarbon concentration at the evaporator outlet and in the gas phase space of the storage tank is continuously monitored and kept within safe thresholds.

[0063] After S6 is filled, close the filling valve and cut off the liquid phase feed to the evaporator; continuously introduce nitrogen to purge and dilute the evaporator and return pipeline. After purging, close the feed valve and pressure valve and stop introducing nitrogen into the evaporator.

[0064] When the liquid level in the storage tank drops to the preset lower limit, or the liquid level in the tank truck reaches the full tank threshold, the control system first closes the filling valve, and simultaneously and immediately closes the evaporator liquid phase inlet emergency shut-off valve and the electric regulating valve, stopping the feed and vaporization of the raw liquid. Diluting nitrogen is introduced for 30 seconds to thoroughly purge and dilute the residual hydrocarbon-rich gas phase in the evaporator and return pipeline. All the purged gas phase is returned to the storage tank to ensure no hydrocarbon accumulation in the pipeline. The nitrogen dilution regulating valve and the gas phase return emergency shut-off valve are closed to complete the safe isolation of the evaporator. Simultaneously, the storage tank safety vent valve is opened to slowly depressurize to the normal storage pressure, completing the entire pressurization and filling operation.

[0065] Example 2: This embodiment also provides a safety pressurization system based on a lean krypton xenon liquid storage tank with an integrated evaporator. The system is characterized in that the lean krypton xenon liquid storage tank is equipped with a liquid evaporator; the liquid phase inlet of the liquid evaporator is connected to the liquid phase zone of the lean krypton xenon liquid storage tank via a feed pipe; and the gas phase outlet of the liquid evaporator is connected to the gas phase space of the lean krypton xenon liquid storage tank via a return pipe. The feed pipe is equipped with a feed valve, and the return pipe is equipped with a pressurization valve. The system also includes a nitrogen output unit connected to the liquid evaporator, and the nitrogen output unit is equipped with an outlet valve. It also includes a controller, which is configured to: Close the feed valve of the liquid evaporator and open the pressure boosting valve; control the nitrogen output unit to introduce nitrogen into the liquid evaporator and the gas phase space of the storage tank until the oxygen content and hydrocarbon concentration in the gas phase space of the storage tank drop below the preset safety threshold. Control the initial opening of the feed valve of the liquid evaporator so that the lean krypton xenon liquid in the lean krypton xenon liquid storage tank is introduced into the evaporator, and the lean krypton xenon liquid is vaporized in the evaporator. Adjust the nitrogen flow rate and the opening of the feed valve to dilute the vaporized gas phase, so that the hydrocarbon concentration is lower than the preset safety threshold. The diluted gas phase is sent into the gas phase space of the storage tank through the reflux pipeline until the gas phase space of the storage tank reaches the preset target filling pressure range. Once the storage tank pressure stabilizes to the preset target filling pressure range, open the storage tank filling valve to fill the tank truck; during the filling process, adjust the liquid phase feed rate and nitrogen flow rate of the evaporator to keep the storage tank pressure stable within the preset target filling pressure range. After filling is completed, close the filling valve and cut off the liquid phase feed to the evaporator; continuously introduce nitrogen to purge and dilute the evaporator and return pipeline. After purging is completed, close the feed valve and pressure valve and stop introducing nitrogen into the evaporator.

[0066] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0067] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A safe pressurization method based on a lean krypton xenon liquid storage tank with an integrated evaporator, characterized in that, include: S1 closes the feed valve of the liquid evaporator and opens the booster valve; controls the nitrogen output unit to introduce nitrogen into the liquid evaporator and the gas phase space of the storage tank until the oxygen content and hydrocarbon concentration in the gas phase space of the storage tank drop below the preset safety threshold. S2 controls the initial opening of the feed valve of the liquid evaporator, allowing the lean krypton xenon liquid in the lean krypton xenon liquid storage tank to be introduced into the evaporator, so that the lean krypton xenon liquid is vaporized in the evaporator. S3 adjusts the nitrogen flow rate and the opening of the feed valve to dilute the vaporized gas phase, so that the hydrocarbon concentration is lower than the preset safety threshold. S4 sends the diluted gas phase into the gas phase space of the storage tank through the reflux pipeline until the gas phase space of the storage tank reaches the preset target filling pressure range. S5 Once the storage tank pressure stabilizes to the preset target filling pressure range, open the storage tank filling valve to fill the tank truck; during the filling process, adjust the liquid phase feed rate and nitrogen flow rate of the evaporator to keep the storage tank pressure stable within the preset target filling pressure range. After S6 is filled, close the filling valve and cut off the liquid phase feed to the evaporator; continuously introduce nitrogen to purge and dilute the evaporator and return pipeline. After purging, close the feed valve and pressure valve and stop introducing nitrogen into the evaporator.

2. The safe pressurization method based on the evaporator of a lean krypton xenon liquid storage tank according to claim 1, characterized in that, The initial opening of the feed valve of the liquid evaporator is controlled using the formula: Calculate the optimal initial opening of the feed valve; where K init For the optimal initial opening of the feed valve, K rated P is the rated opening of the feed valve. set For the target filling pressure of the storage tank, P tank0 V is the initial gas phase pressure of the storage tank. gas C is the volume of the gas phase space in the storage tank. feed T represents the total hydrocarbon concentration of the original solution. env For ambient temperature, T feed T represents the temperature of the original solution. max is the maximum allowable wall temperature of the evaporator, and a, b, and c are pre-calibrated weighting coefficients.

3. The safe pressurization method based on the evaporator of a krypton-xenon liquid storage tank according to claim 2, characterized in that, The hard constraint condition for the optimal initial opening is: 3%K rated ≤K init ≤12%K rated .

4. The safe pressurization method based on the evaporator of a lean krypton xenon liquid storage tank according to claim 1, characterized in that, Methods for adjusting the nitrogen flow rate and the opening degree of the feed valve include: The combined concentrations of methane and total hydrogen in the gas phase at the evaporator outlet are predicted, and the feedforward rate of nitrogen is calculated based on the predicted hydrocarbon component concentrations. Based on the real-time collected data on the hydrocarbon concentration of the raw liquid, the real-time pressure of the storage tank, and the real-time pressurization rate, the maximum allowable heat exchange temperature difference between the evaporator wall and the lean krypton xenon raw liquid is calculated. Based on the deviation between the real-time heat exchange temperature difference and the maximum allowable heat exchange temperature difference, the upper limit of the constraint on the opening of the evaporator feed valve is calculated. The feedforward flow rate of nitrogen and the upper limit of the evaporator feed valve opening are input into a pre-built cascade control architecture, thereby outputting control parameters for the evaporator feed valve opening and the nitrogen flow rate, and controlling the evaporator feed valve and nitrogen flow according to the control parameters.

5. A safe pressurization method based on an evaporator integrated into a krypton-xenon liquid storage tank according to claim 4, characterized in that, The combined concentrations of methane and total hydrogen in the evaporator outlet gas phase are predicted using a pre-constructed krypton-xenon hydrocarbon evolution model; the krypton-xenon hydrocarbon evolution model is as follows: ； ； in, The real-time evolution rate of methane and total hydrogen is given by , k is the system correction factor, and F... feed P is the liquid phase feed rate of the evaporator. wal l is the saturated vapor pressure at the corresponding temperature of the evaporator wall, P sat,CH Let E be the saturated vapor pressure of the hydrocarbon component at the current temperature, E be the activation energy of the hydrocarbon component's vaporization, R be the gas constant, and T be the saturated vapor pressure of the hydrocarbon component at the current temperature. wall T represents the real-time wall temperature of the evaporator. feed For the temperature of the krypton-depleted xenon stock solution, C CH,pred (t+n) represents the predicted combined hydrocarbon concentration in the evaporator outlet gas phase over the next n seconds, C CH,real (t) represents the measured value of hydrocarbon concentration at the current moment.

6. A safe pressurization method based on an evaporator integrated into a krypton-xenon liquid storage tank according to claim 4, characterized in that, Using the formula: Calculate the maximum allowable heat transfer temperature difference; where ΔT max ΔT is the maximum allowable heat transfer temperature difference. base Based on the temperature difference, LEL real C represents the real-time lower limit of explosion under the current operating conditions. feed P represents the total hydrocarbon concentration of the krypton-depleted xenon stock solution. set To achieve the target filling pressure, P tank denoted as ρ, where ρ is the real-time pressure of the storage tank, |dP / dt| is the absolute value of the real-time pressure increase rate, and α, β, and γ are pre-calibrated weighting coefficients.

7. A safe pressurization method based on an evaporator integrated into a krypton-xenon liquid storage tank according to claim 4, characterized in that, Methods for calculating the upper limit of the constraint on the opening of the evaporator feed valve include: When the real-time heat exchange temperature difference ΔT real ≤0.8ΔT max At this time, the upper limit of the feed valve opening is 15% of the rated opening; When 0.8ΔT max <ΔT real ≤0.9ΔT max At this time, the upper limit of the feed valve opening is 8% of the rated opening; When 0.9ΔT max <ΔT real ≤ΔT max At this time, the upper limit of the feed valve opening is 5% of the rated opening; When ΔT real >ΔT max When the time comes, close the feed valve.

8. A safe pressurization method based on an evaporator integrated into a krypton-xenon liquid storage tank according to claim 4, characterized in that, The cascade control architecture is a main-sub-loop cascade control architecture. The main loop takes the target filling pressure of the storage tank and the preset safe pressurization rate as the control targets and outputs the set value of the evaporator feed valve opening. The sub-loop takes the safe threshold of hydrocarbon concentration as the control target and outputs the set value of the nitrogen output unit outlet valve opening.

9. A safe pressurization method based on an evaporator integrated into a krypton-xenon liquid storage tank according to claim 1, characterized in that: The preset target filling pressure range for the storage tank is 0.38~0.42MPa; the preset maximum allowable pressurization rate is ≤0.01MPa / min; the preset safety threshold for hydrocarbon concentration is ≤20% for the lower explosive limit (LEL) of methane and total hydrogen, and the safety threshold for oxygen content is ≤2%.

10. A safe pressurization system based on a lean krypton xenon liquid storage tank with an integrated evaporator, characterized in that, The lean krypton xenon liquid storage tank is equipped with a liquid evaporator. The liquid phase inlet of the liquid evaporator is connected to the liquid phase zone of the lean krypton xenon liquid storage tank through a feed pipe, and the gas phase outlet of the liquid evaporator is connected to the gas phase space of the lean krypton xenon liquid storage tank through a return pipe. The feed pipe is equipped with a feed valve, and the return pipe is equipped with a pressure boosting valve. It also includes a nitrogen output unit connected to the liquid evaporator, and the nitrogen output unit is equipped with an outlet valve. It also includes a controller, which is configured to: Close the feed valve of the liquid evaporator and open the pressure boosting valve; control the nitrogen output unit to introduce nitrogen into the liquid evaporator and the gas phase space of the storage tank until the oxygen content and hydrocarbon concentration in the gas phase space of the storage tank drop below the preset safety threshold. Control the initial opening of the feed valve of the liquid evaporator so that the lean krypton xenon liquid in the lean krypton xenon liquid storage tank is introduced into the evaporator, and the lean krypton xenon liquid is vaporized in the evaporator. Adjust the nitrogen flow rate and the opening of the feed valve to dilute the vaporized gas phase, so that the hydrocarbon concentration is lower than the preset safety threshold. The diluted gas phase is sent into the gas phase space of the storage tank through the reflux pipeline until the gas phase space of the storage tank reaches the preset target filling pressure range. Once the storage tank pressure stabilizes to the preset target filling pressure range, open the storage tank filling valve to fill the tank truck; during the filling process, adjust the liquid phase feed rate and nitrogen flow rate of the evaporator to keep the storage tank pressure stable within the preset target filling pressure range. After filling is completed, close the filling valve and cut off the liquid phase feed to the evaporator; continuously introduce nitrogen to purge and dilute the evaporator and return pipeline. After purging is completed, close the feed valve and pressure valve and stop introducing nitrogen into the evaporator.

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