Air separation rectifying tower low-temperature rectification optimization control strategy based on sensitivity analysis

Abstract

The invention provides an air separation rectifying tower low-temperature rectification optimization control strategy based on sensitivity analysis, and relates to the technical field of computer processing, the method comprises the following steps: S01, temperature and tower pressure data of a rectifying tower sensitive area in an air separation device are detected in real time through a DCS system, and the sensitive area is a filler section with the maximum concentration gradient change in the rectifying tower; s02, acquiring real-time temperature and tower pressure data of the sensitive area of the rectifying tower, and dynamically calculating gas-phase and liquid-phase component concentrations of the sensitive area of the rectifying tower in combination with a preset gas-liquid balance function relational expression; and S03, comparing the calculated concentrations of the gas-phase and liquid-phase components with a design value. According to the method, a function model between a gas-liquid balance parameter of a sensitive temperature interval and an argon raw material extraction opening component is established, and a temperature-concentration curve and sensitivity analysis data of process simulation software are combined, so that the nitrogen and oxygen impurity concentration in an argon raw material is calculated in real time.

Description

Technical Field

[0001] The present invention relates to the field of computer processing technology, and in particular to a low-temperature distillation optimization control strategy for an air fractionation distillation tower based on sensitivity analysis. Background Art

[0002] In an air separation unit, the main distillation tower is the core equipment for separating gas components such as oxygen, nitrogen, and argon. Its operational stability directly determines product purity and output. The reflux ratio of each packing section of the distillation tower (i.e., the flow ratio ratio of downstream liquid to ascending vapor) is a key parameter for maintaining gas-liquid equilibrium and separation efficiency. If the reflux ratio fluctuates, the temperature distribution in the tower will change, disrupting the gas-liquid equilibrium state, thereby affecting the component concentration distribution and ultimately reducing product purity. However, traditional control methods rely on purity analysis data of the end product (such as oxygen and nitrogen purity) to adjust process parameters, which has significant technical defects:

[0003] 1. Detection and transmission delay: Product purity needs to be sampled and tested by an analyzer outside the cold box. There is a time delay in the process of transferring the sample from the process pipeline to the analyzer;

[0004] 2. Process pure lag: The product extraction point is located in the concentration section of the distillation tower, and its state adjustment needs to go through a multi-stage distillation process in the tower, resulting in a control response lag.

[0005] 3. The combined effect of detection transmission lag and process pure lag makes it difficult for traditional control to respond to changes in working conditions in a timely manner, especially when there are load fluctuations or external disturbances, which can easily cause unstable product quality.

[0006] 3. The argon feedstock is collected from the stripping section of a low-pressure distillation tower, where the concentration gradient is small. The functional relationship between the vapor-liquid equilibrium temperature and component concentration cannot accurately reflect changes in nitrogen and oxygen impurity levels in the argon feedstock. Traditional methods rely on physical analyzers to monitor argon feedstock composition, but due to the characteristics of the stripping section, real-time monitoring using temperature-concentration soft sensing technology is difficult.

[0007] To address this issue, existing technologies attempt to indirectly control the distillation tower by linking temperature-sensitive points within the tower with component concentrations. For example, in packing sections with large concentration gradients (such as the lower packing section where the liquid-air vapor from the crude argon condenser enters the upper tower), oxygen and nitrogen concentrations are estimated using vapor-liquid equilibrium temperature and pressure data. This allows for the construction of a soft-sensing model to shorten control response time. However, this approach cannot be directly applied to monitoring the argon feedstock stripping section due to its insensitive temperature-concentration relationship. Consequently, quality control of the argon distillation feedstock still relies on offline analysis, which is inefficient. Summary of the Invention

[0008] In response to the above technical problems, the technical solution adopted by the present invention is a low-temperature distillation optimization control strategy for an air fractionation distillation tower based on sensitivity analysis. The method comprises the following steps:

[0009] S01. Real-time detection of temperature and tower pressure data of a sensitive area of ​​a distillation tower in an air separation unit through a DCS system. The sensitive area is a packing section with the largest concentration gradient change in the distillation tower.

[0010] S02. Dynamically calculate the concentrations of gas and liquid components in the sensitive areas of the distillation tower using the acquired real-time temperature and tower pressure data of the sensitive areas of the distillation tower in combination with a preset gas-liquid equilibrium function relationship;

[0011] S03. Comparing the calculated concentrations of the gas phase and liquid phase components with the designed values, and controlling the concentrations of the gas phase and liquid phase components within a set threshold range by adjusting the reflux ratio or feed rate of the distillation column;

[0012] S04. Real-time monitoring of the oxygen content in the crude argon product at the top of the crude argon column. When the oxygen content is ≤1 ppm, maximizing the crude argon production to prevent the argon component from flowing back into the stripping section of the low-pressure column.

[0013] S05. Dynamically adjust the temperature setting values ​​of the sensitive areas of the medium-pressure tower, low-pressure tower and crude argon tower according to the load changes, so that the distillation tower operating conditions automatically track the load changes to always maintain the optimal state.

[0014] Preferably, the method for dividing the sensitive area of ​​the middle distillation tower in step S03 includes:

[0015] The sensitive area of ​​the low-pressure tower is located in the gas-liquid distributor area above the packing section corresponding to the oxygen-enriched air feed inlet from the crude argon condenser. The temperature gradient change rate of the corresponding packing section is ≥5℃ / m, and the temperature setting value is -188℃±0.3℃;

[0016] The sensitive area of ​​the medium-pressure tower is located in the oxygen-rich liquid air pipeline at the bottom of the tower, and the detection temperature is -176℃±1℃;

[0017] The sensitive area of ​​the crude argon tower is located in the middle packing section, and the temperature setting value is -183.6℃±0.5℃.

[0018] Preferably, in the sensitive area of ​​the distillation section of the low-pressure tower, when the concentration of the gaseous argon component is ≤2%, it is simplified to an oxygen and nitrogen binary distillation model, and the calculation of the argon component is ignored. At this time, xar=0, yar=0, xo2+xn2=1, yo2+yn2=1.

[0019] Preferably, the oxygen concentration design threshold in step S03 is:

[0020] The design value of gas-phase oxygen concentration in the sensitive area of ​​the low-pressure tower is 30%±1%;

[0021] The design value of liquid oxygen concentration at the bottom of the medium-pressure tower is 41%±2%.

[0022] Preferably, the gas-liquid equilibrium function relationship in step S02 includes the following formula:

[0023] Oxygen component balance formula:

[0024] Nitrogen component balance formula:

[0025] Argon composition equilibrium formula:

[0026] Among them, T is the thermodynamic temperature, t is the detection temperature, P is the distillation tower pressure, and the liquid and gas phase concentrations satisfy:

[0027] .

[0028] Preferably, the dynamic adjustment in step S05 specifically includes:

[0029] When the load of the air separation unit increases, the temperature setting value of the sensitive area of ​​the low-pressure tower is reduced by 0.1-0.5℃ from the design value of -188℃, and the tower pressure is set to 1.13atm±0.02atm;

[0030] When the load of the air separation unit decreases, the temperature setting value of the sensitive area of ​​the low-pressure tower is increased by 0.1-0.5°C from the design value of -188°C, and the tower pressure is adjusted to 1.13atm±0.02atm simultaneously.

[0031] Preferably, the method for calculating the tower pressure data in step S01 includes:

[0032] S11, collect the top pressure P of the distillation tower in real time through the DCS system 顶 and the bottom pressure P 底 , calculate the arithmetic mean of the two as the distillation tower pressure P, then the formula is as follows: P= (P 顶 +P 底 ) / 2;

[0033] S12. The pressure difference between the top and bottom of the tower must meet the following requirements: If the pressure difference exceeds the limit, the DCS system will trigger an alarm and automatically adjust the distillation tower operating parameters to restore the pressure difference to the allowable range.

[0034] Preferably, the control of the oxygen content in the crude argon product at the top of the crude argon column in step S04 is achieved by a PID algorithm, and the linear relationship between its set value and the load of the air separation unit is: Q 采出 =k·L+b, where Q 采出is the crude argon production flow rate, L is the load percentage of the air separation unit, k is the load-flow ratio coefficient, and b is the basic flow constant.

[0035] The present invention has at least the following beneficial effects:

[0036] 1. Soft-sensing technology replaces traditional analyzers. Based on the DCS, the system monitors temperature and pressure parameters in sensitive areas of the distillation column in real time. Dynamic calculation of component concentrations based on the vapor-liquid equilibrium function eliminates sampling lag, enabling instant feedback and closed-loop control of distillation conditions. Furthermore, in sensitive areas with large concentration gradients (such as the low-pressure column distillation section), the strong correlation between temperature and component concentration ensures control accuracy, effectively maintaining oxygen, nitrogen, and argon components within design thresholds.

[0037] 2. Dynamically adjust parameters such as the reflux ratio and feed rate through the DCS's internal cascade control loop to ensure the distillation tower's concentration gradient closely matches the design range, increasing oxygen and nitrogen product extraction rates by 5%-10% and reducing unit energy consumption. In load fluctuation scenarios (such as non-ferrous metal smelting), the system automatically tracks and adjusts temperature setpoints in sensitive areas to maintain gas-liquid equilibrium and avoid efficiency losses due to fluctuating operating conditions.

[0038] 3. In the sensitive areas of the low-pressure tower, medium-pressure tower, and crude argon tower, soft measurement technology is used to replace liquid air analyzers, fraction analyzers, and other equipment, thereby simplifying the system architecture and greatly reducing construction and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 A flow chart of a low-temperature distillation optimization control strategy for an air separation distillation tower based on sensitivity analysis is provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0043] Example 1

[0044] This embodiment provides an optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis, and the method includes the following steps: Figure 1 As shown:

[0045] S01. Use the DCS system to monitor the temperature and pressure data of the sensitive area of ​​the distillation tower in the air separation unit in real time. The sensitive area is the packing section with the largest concentration gradient change in the distillation tower.

[0046] Specifically, the calculation method of the above-mentioned middle tower pressure data includes:

[0047] S11, collect the top pressure P of the distillation tower in real time through the DCS system 顶 and the bottom pressure P 底 , calculate the arithmetic mean of the two as the distillation tower pressure P, then the formula is as follows: P= (P 顶 +P 底 ) / 2;

[0048] S12. The pressure difference between the top and bottom of the tower must meet the following requirements: If the pressure difference exceeds the limit, the DCS system will trigger an alarm and automatically adjust the distillation tower operating parameters to restore the pressure difference to the allowable range.

[0049] In practical applications:

[0050] Set up a pressure acquisition module in the DCS system to obtain real-time data from the tower top and tower bottom pressure sensors;

[0051] Automatically calculate the average value and substitute it into the gas-liquid equilibrium formula to calculate the component concentration;

[0052] When the pressure difference exceeds the limit, the local resistance is reduced by adjusting the gas-liquid flow or reflux ratio in the tower to restore the pressure difference.

[0053] For example, in a low-pressure tower, the measured top pressure is 1.12 atm, the bottom pressure is 1.14 atm, and the pressure differential is 0.02 atm (≤ 0.05 atm). The calculated tower pressure is: P = (1.12 + 1.14) / 2 = 1.13 atm. This value is then directly substituted into the gas-liquid equilibrium formula to calculate the oxygen, nitrogen, and argon concentrations, ensuring they are consistent with the design values ​​(e.g., gas-phase oxygen concentration of 30%). If the pressure differential exceeds the limit (e.g., 0.06 atm), the DCS will automatically adjust the feed valve opening or reflux ratio until the pressure differential returns to the allowable range.

[0054] In the above technology, through the calculation program set within the DCS and the distillation tower sensitivity analysis design points designed based on ASPEN software during the process design process, the temperature index required by the soft measurement technology is implemented in the area where the concentration gradient of the distillation tower is the largest (that is, the gradient of the distillation gas-liquid equilibrium operating temperature). Due to the use of structured packing technology, the resistance of the distillation tower is significantly lower than that of the traditional plate tower, and the difference between the top and bottom pressures of the distillation tower is negligible. Therefore, when the distillation tower pressure data is used for calculation, the arithmetic average of the top and bottom pressures of the distillation tower is selected as the tower pressure data, which is fully capable of meeting the control accuracy requirements.

[0055] S02. The obtained real-time temperature and tower pressure data of the sensitive area of ​​the distillation tower are combined with a preset gas-liquid equilibrium function relationship to dynamically calculate the gas phase and liquid phase component concentrations in the sensitive area of ​​the distillation tower.

[0056] The above gas-liquid equilibrium function relationship includes the following formula:

[0057] Oxygen component balance formula:

[0058]

[0059] Nitrogen component balance formula:

[0060]

[0061] Argon composition equilibrium formula:

[0062]

[0063] The concentrations of liquid and gas phases satisfy:

[0064] .

[0065] Among them, Psn: nitrogen component saturated vapor pressure presents a single-valued function relationship with distillation temperature, unit: atm;

[0066] Pso: The saturated vapor pressure of oxygen component presents a single-valued function relationship with the distillation temperature, unit: atm;

[0067] Par: The saturated vapor pressure of argon component presents a single-valued function relationship with the distillation temperature, unit: atm;

[0068] 1atm=101.33KPAt: Distillation gas-liquid equilibrium temperature unit: °C;

[0069] P: distillation tower pressure, unit atm;

[0070] t: The working temperature of the distillation tower during the distillation process ℃;

[0071] T: corresponds to the thermodynamic temperature K;

[0072] Yo2: oxygen content in the gas phase of the packing section corresponding to the distillation temperature of the distillation tower;

[0073] Yn2: Nitrogen content in the gas phase of the packing section corresponding to the distillation temperature of the distillation tower;

[0074] Yar: Argon content in the gas phase of the packing section corresponding to the distillation temperature of the distillation tower;

[0075] xo2: oxygen content in the liquid phase of the packing section corresponding to the distillation temperature of the distillation tower;

[0076] xn2: nitrogen content in the liquid phase of the packing section corresponding to the distillation temperature of the distillation tower;

[0077] xar: argon content in the liquid phase of the packing section corresponding to the distillation temperature of the distillation column;

[0078] t: is the actual detected temperature of the sampling packing section of the distillation tower.

[0079] In the sensitive packing section of the low-pressure tower distillation section, since the argon component in the gas phase is about 2%, and in the actual operation of the air separation unit, as long as the oxygen component concentration in the sensitive packing section of the low-pressure tower distillation section is effectively controlled, the argon component and nitrogen component balance composition in the stripping section can be effectively controlled, thereby ensuring that the nitrogen component in the raw materials required for the argon system distillation process is controlled within the allowable value. Therefore, when we control the distillation of the sensitive packing section of the low-pressure tower distillation section, we use the binary distillation processing method for data processing. The correspondence between the gas-liquid equilibrium temperature and the gas-liquid equilibrium components of the above distillation tower only considers the oxygen and nitrogen component concentrations. As long as the corresponding gas-liquid equilibrium temperature is controlled, the distillation conditions of each packing section of the low-pressure tower can be effectively controlled to be in the optimal state.

[0080] Through the above functional correlation formulas, the distillation tower sensitive point temperature and distillation tower pressure detected by DCS, the concentration of the corresponding intermediate components in the distillation tower can be calculated through the above functional relationship, thereby avoiding the use of online analyzers to directly sample and analyze components. Since the distillation tower sensitivity temperature is the temperature detection set for the gas-liquid equilibrium distillation inside the distillation tower during process design, it can timely reflect the gas-liquid equilibrium composition under steady-state working conditions when the distillation tower is working, thereby effectively controlling the distillation conditions of the stripping section and the distillation section of the distillation tower, ensuring that the product quality is in a reliable state.

[0081] For the low-pressure tower, the area with the largest concentration difference based on gas-liquid equilibrium composition is around -188°C. The tower pressure of the distillation tower is generally in a relatively stable state. The working pressure of the low-pressure tower is around 1.13atm. Substituting the above two data into the above formula in turn, the design component concentration of the sensitive area with the largest concentration gradient of the low-pressure tower can be calculated: gas phase yo2=30%, liquid phase xo2=63%.

[0082] Since this area of ​​the low-pressure tower lies below the oxygen-rich liquid air feed section and above the argon feed outlet, the argon content is negligible during industrial process analysis and testing. Therefore, effectively controlling the oxygen concentration around this design point prevents the nitrogen content in the argon feed gas from exceeding the design value, thereby impacting the subsequent argon distillation tower operation. By effectively controlling the gas-liquid distillation equilibrium in the sensitive packing section of the low-pressure tower and maintaining a stable temperature of around -188°C, the corresponding oxygen composition can be effectively controlled. Since the distillation tower's sensitive temperature range is relatively small, even a 0.3°C fluctuation above the setpoint of -188°C will result in a change of at least 1% in oxygen concentration. Therefore, by using the internal relationship between distillation tower temperature and gas-liquid equilibrium composition within the DCS, the DCS detects the temperature at the sensitive point in the distillation tower packing section and then converts it into an oxygen concentration composition through calculation. This allows for faster reflection of changes in the tower's operating conditions, improving control accuracy and enabling timely and effective control.

[0083] S03. Compare the calculated gas phase and liquid phase component concentrations with the design values, and control the gas phase and liquid phase component concentrations within the set threshold range by adjusting the reflux ratio or feed rate of the distillation column;

[0084] Specifically, the method for dividing the sensitive areas of the above-mentioned middle distillation tower includes:

[0085] The sensitive area of ​​the low-pressure tower is located in the gas-liquid distributor area above the packing section corresponding to the oxygen-enriched air feed inlet from the crude argon condenser. The temperature gradient change rate of the corresponding packing section is ≥5℃ / m, and the temperature setting value is -188℃±0.3℃;

[0086] The sensitive area of ​​the medium-pressure tower is located in the oxygen-rich liquid air pipeline at the bottom of the tower, and the detection temperature is -176℃±1℃;

[0087] The sensitive area of ​​the crude argon tower is located in the middle packing section, and the temperature setting value is -183.6℃±0.5℃.

[0088] Furthermore, in the sensitive area of ​​the distillation section of the low-pressure tower, when the concentration of the gaseous argon component is ≤2%, it is simplified to an oxygen and nitrogen binary distillation model, and the calculation of the argon component is ignored. At this time, xar=0, yar=0, xo2+xn2=1, yo2+yn2=1.

[0089] Secondly, the above-mentioned design threshold of medium oxygen concentration is:

[0090] The design value of gas-phase oxygen concentration in the sensitive area of ​​the low-pressure tower is 30%±1%;

[0091] The design value of liquid oxygen concentration at the bottom of the medium-pressure tower is 41%±2%.

[0092] In the above technology, the medium-pressure column, after the feed air is purified through a preliminary distillation tower, produces pure nitrogen at the top and oxygen-enriched liquid air at the bottom. The oxygen-enriched liquid air is then fed to the low-pressure tower for further distillation, resulting in pure oxygen at the bottom and atmospheric-pressure nitrogen at the top. Both the medium-pressure and low-pressure towers have regions with significant concentration gradients. These regions of maximum concentration gradient also correspond to the regions of maximum temperature gradient in the distillation tower, and these regions are in a corresponding relationship. The low-pressure tower is a relatively complex equipment in the main distillation tower. It is divided into the distillation section (the area above the oxygen-rich liquid air feed inlet) and the stripping section (the area below the oxygen-rich liquid air feed inlet) based on the feed point from the medium-pressure tower to the low-pressure tower. The concentration gradient in the stripping section of the low-pressure tower changes slightly, and the operating temperature change range of the distillation tower is not enough to reflect the obvious change in concentration during the distillation process. However, there is an area with a large concentration gradient change in the distillation section of the low-pressure tower, that is, with a unit change in the height of the packing section of the distillation tower, its concentration composition and temperature change rate are greater. We call this area the sensitive working area of ​​the distillation tower. By setting temperature detection in the corresponding packing section of the distillation tower, a slight change in the temperature can clearly reflect the obvious change in the distillation working condition, that is, the area where the concentration changes greatly.

[0093] Analyzing the process flow using ASPEN software revealed a sensitive temperature distribution range for the low-pressure tower. If the temperatures at these sensitive points in the rectifying and stripping sections of the low-pressure tower can be kept near the design values, the low-pressure tower's distillation operation will be optimized. This design value is between -187.5 and -188.5°C, with a typical setpoint of around -188°C. Based on the principle of vapor-liquid equilibrium, the following relationship allows us to optimize the distillation operation of the distillation tower.

[0094] S04. Real-time monitoring of the oxygen content in the crude argon product at the top of the crude argon column. When the oxygen content is ≤1 ppm, maximizing the crude argon production to prevent the argon component from flowing back into the stripping section of the low-pressure column.

[0095] Specifically, the control of the oxygen content in the crude argon product at the top of the crude argon tower is achieved through the PID algorithm. Through cascade control and external given calculation, the linear relationship between its set value and the load of the air separation unit is: Q 采出 =k·L+b, where Q 采出 is the crude argon production flow rate, L is the total process air flow rate corresponding to the load of the air separation unit, k is the load-flow ratio coefficient, and b is the corrected flow constant.

[0096] In the above technology, when the load changes, Q 采出 It is adjusted linearly with L, and the influence of temperature and pressure fluctuations on oxygen content is dynamically compensated by PID. For example:

[0097] Air separation unit load , calculate Q 采出 =0.00666×300000+200=2198Nm³ / h;

[0098] If the actual detection At the same time, when the distillation temperature of the sensitive area of ​​the crude argon tower remains unchanged, the PID output maintains the current production volume;

[0099] like Or when the distillation temperature in the sensitive area of ​​the crude argon tower increases, the PID output of the cascade control loop is corrected to reduce the extraction rate and quickly reduce the oxygen content to below 1 ppm.

[0100] S05. Dynamically adjust the temperature setting values ​​of the sensitive areas of the medium-pressure tower, low-pressure tower and crude argon tower according to the load changes, so that the distillation tower operating conditions automatically track the load changes to always maintain the optimal state.

[0101] Specifically, the dynamic adjustments referred to above include:

[0102] When the load of the air separation unit increases, the temperature setting value of the sensitive area of ​​the low-pressure tower is reduced by 0.1-0.5℃ from the design value of -188℃, and the tower pressure is set to 1.13atm±0.02atm;

[0103] When the load of the air separation unit decreases, the temperature setting value of the sensitive area of ​​the low-pressure tower is increased by 0.1-0.5°C from the design value of -188°C, and the tower pressure is adjusted to 1.13atm±0.02atm simultaneously.

[0104] In the above technology, the low-pressure tower gas-phase oxygen concentration threshold (30%±1%): the gas-phase oxygen concentration design value in the sensitive area of ​​the low-pressure tower is 30% calculated through gas-liquid equilibrium, and a temperature fluctuation of ±0.3°C will cause the oxygen concentration to change by ≥1%. When the gas-phase oxygen concentration calculated by the DCS system deviates from 30% (such as the detected value is 31% or 29%), the reflux ratio or feed rate is automatically adjusted to return the oxygen concentration to the threshold range.

[0105] Liquid oxygen concentration threshold at the bottom of the medium-pressure tower (41% ± 2%): The calculated liquid oxygen concentration of the oxygen-enriched liquid air at the bottom of the medium-pressure tower is 41%, which directly affects the feed composition of the low-pressure tower. A ±2% fluctuation range is allowed to account for the cumulative error in the medium-pressure tower operating pressure (460 kPa) and temperature measurement (-176°C ± 1°C). The liquid oxygen concentration is verified by real-time insertion into the vapor-liquid equilibrium equation using the medium-pressure tower bottom temperature measurement (-176°C ± 1°C) and tower pressure calculation (4.54 atm). If the liquid oxygen concentration exceeds 41% ± 2%, adjust medium-pressure tower operating parameters (such as the dirty liquid nitrogen extraction rate or the liquid nitrogen extraction rate).

[0106] Example 2

[0107] An embodiment of the present invention provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores at least one instruction or at least one program, and the at least one instruction or at least one program is loaded and executed by a processor to implement the steps:

[0108] The DCS system is used to monitor the temperature and pressure data of the sensitive area of ​​the distillation tower in the air separation unit in real time. The sensitive area is the packing section with the largest concentration gradient change in the distillation tower.

[0109] The real-time temperature and tower pressure data of the sensitive area of ​​the distillation tower are obtained, and combined with the preset gas-liquid equilibrium function relationship, the concentration of gas and liquid components in the sensitive area of ​​the distillation tower is dynamically calculated;

[0110] Compare the calculated gas and liquid component concentrations with the design values, and control the gas and liquid component concentrations within the set threshold range by adjusting the reflux ratio or feed rate of the distillation tower;

[0111] Real-time monitoring of the oxygen content in the crude argon product at the top of the crude argon tower. When the oxygen content is ≤1ppm, the crude argon production rate is maximized to prevent the argon component from flowing back into the stripping section of the low-pressure tower.

[0112] The temperature setting values ​​of the sensitive areas of the medium-pressure tower, low-pressure tower and crude argon tower are dynamically adjusted according to load changes, so that the working conditions of the distillation tower can automatically track the load changes to always maintain the optimal state.

[0113] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing the relevant hardware using a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the above-described method embodiments. Any reference to memory, storage, database, or other media used in the various embodiments provided herein may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct RAMbus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM).

[0114] Those skilled in the art will clearly understand that for the sake of convenience and brevity in description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0115] Example 3

[0116] An embodiment of the present invention provides an electronic device, including a processor and a memory, wherein the memory stores at least one instruction or at least one program, and the at least one instruction or at least one program is loaded and executed by the processor to implement the following steps:

[0117] The DCS system is used to monitor the temperature and pressure data of the sensitive area of ​​the distillation tower in the air separation unit in real time. The sensitive area is the packing section with the largest concentration gradient change in the distillation tower.

[0118] The real-time temperature and tower pressure data of the sensitive area of ​​the distillation tower are obtained, and combined with the preset gas-liquid equilibrium function relationship, the concentration of gas and liquid components in the sensitive area of ​​the distillation tower is dynamically calculated;

[0119] Compare the calculated gas and liquid component concentrations with the design values, and control the gas and liquid component concentrations within the set threshold range by adjusting the reflux ratio or feed rate of the distillation tower;

[0120] Real-time monitoring of the oxygen content in the crude argon product at the top of the crude argon tower. When the oxygen content is ≤1ppm, the crude argon production rate is maximized to prevent the argon component from flowing back into the stripping section of the low-pressure tower.

[0121] The temperature setting values ​​of the sensitive areas of the medium-pressure tower, low-pressure tower and crude argon tower are dynamically adjusted according to load changes, so that the working conditions of the distillation tower can automatically track the load changes to always maintain the optimal state.

[0122] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A low-temperature distillation optimization control strategy for an air fractionation distillation tower based on sensitivity analysis, characterized in that: The method comprises the following steps: S01. Real-time detection of temperature and tower pressure data of a sensitive area of ​​a distillation tower in an air separation unit through a DCS system. The sensitive area is a packing section with the largest concentration gradient change in the distillation tower. S02. Dynamically calculate the concentrations of gas and liquid components in the sensitive areas of the distillation tower using the acquired real-time temperature and tower pressure data of the sensitive areas of the distillation tower in combination with a preset gas-liquid equilibrium function relationship; S03. Comparing the calculated concentrations of the gas phase and liquid phase components with the designed values, and controlling the concentrations of the gas phase and liquid phase components within a set threshold range by adjusting the reflux ratio or feed rate of the distillation column; S04. Real-time monitoring of the oxygen content in the crude argon product at the top of the crude argon column. When the oxygen content is ≤1 ppm, maximizing the crude argon production to prevent the argon component from flowing back into the stripping section of the low-pressure column. S05. Dynamically adjust the temperature setting values ​​of the sensitive areas of the medium-pressure tower, low-pressure tower and crude argon tower according to the load changes, so that the distillation tower operating conditions automatically track the load changes to always maintain the optimal state.

2. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 1, characterized in that: The method for dividing the sensitive area of ​​the middle distillation tower in step S03 includes: The sensitive area of ​​the low-pressure tower is located in the gas-liquid distributor area above the packing section corresponding to the oxygen-enriched air feed inlet from the crude argon condenser. The temperature gradient change rate of the corresponding packing section is ≥5℃ / m, and the temperature setting value is -188℃±0.3℃; The sensitive area of ​​the medium-pressure tower is located in the oxygen-rich liquid air pipeline at the bottom of the tower, and the detection temperature is -176℃±1℃; The sensitive area of ​​the crude argon tower is located in the middle packing section, and the temperature setting value is -183.6℃±0.5℃.

3. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 2, characterized in that: In the sensitive area of ​​the distillation section of the low-pressure tower, when the concentration of the gaseous argon component is ≤2%, it is simplified to an oxygen and nitrogen binary distillation model, and the calculation of the argon component is ignored. At this time, xar=0, yar=0, xo2+xn2=1, yo2+yn2=1.

4. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 1, characterized in that: The oxygen concentration design threshold in step S03 is: The design value of gas-phase oxygen concentration in the sensitive area of ​​the low-pressure tower is 30%±1%; The design value of liquid oxygen concentration at the bottom of the medium-pressure tower is 41%±2%.

5. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 1, characterized in that: The gas-liquid equilibrium function relationship in step S02 includes the following formula: Oxygen component balance formula: ； Nitrogen component balance formula: ； Argon composition equilibrium formula: ； Among them, T is the thermodynamic temperature, t is the detection temperature, P is the distillation tower pressure, and the liquid and gas phase concentrations satisfy: 。 6. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 1, characterized in that: The dynamic adjustment in step S05 specifically includes: When the load of the air separation unit increases, the temperature setting value of the sensitive area of ​​the low-pressure tower is reduced by 0.1-0.5℃ from the design value of -188℃, and the tower pressure is set to 1.13atm±0.02atm; When the load of the air separation unit decreases, the temperature setting value of the sensitive area of ​​the low-pressure tower is increased by 0.1-0.5°C from the design value of -188°C, and the tower pressure is adjusted to 1.13atm±0.02atm simultaneously.

7. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 1, characterized in that: The method for calculating the tower pressure data in step S01 includes: S11, collect the top pressure P of the distillation tower in real time through the DCS system 顶 and the bottom pressure P 底 , calculate the arithmetic mean of the two as the distillation tower pressure P, then the formula is as follows: P= (P 顶 +P 底 ) / 2; S12. The pressure difference between the top and bottom of the tower must meet the following requirements: If the pressure difference exceeds the limit, the DCS system will trigger an alarm and automatically adjust the distillation tower operating parameters to restore the pressure difference to the allowable range.

8. The optimization control strategy for low-temperature distillation of an air fractionation distillation tower based on sensitivity analysis according to claim 1, characterized in that: The control of the oxygen content in the crude argon product at the top of the crude argon column in step S04 is achieved by a PID algorithm, and the linear relationship between its set value and the load of the air separation unit is: Q 采出 =k·L+b, where Q 采出 is the crude argon production flow rate, L is the load percentage of the air separation unit, k is the load-flow ratio coefficient, and b is the basic flow constant.

9. A non-transitory computer-readable storage medium, wherein at least one instruction or at least one program is stored in the non-transitory computer-readable storage medium, characterized in that: The at least one instruction or the at least one program segment is loaded and executed by the processor to implement the steps of optimizing the control strategy of the low-temperature distillation of the air fractionation distillation tower based on sensitivity analysis as described in any one of claims 1 to 8.

10. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores at least one instruction or at least one program, and the at least one instruction or the at least one program is loaded and executed by the processor to implement the steps of the low-temperature distillation optimization control strategy of the air fractionation distillation tower based on sensitivity analysis as described in any one of claims 1 to 8.

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