Air separation oxygen periodic liquefaction and reallocation system under peak valley electricity condition

Abstract

The invention discloses an air separation oxygen periodic liquefaction and reallocation system under a peak valley electricity condition, and relates to the technical field of gas separation, and the air separation oxygen periodic liquefaction and reallocation system comprises a nitrogen compression subsystem used for providing pressurized nitrogen in a valley electricity period; the liquid oxygen vaporization subsystem is used for vaporizing the stored liquid oxygen by using the cold energy of the pressurized nitrogen and outputting the vaporized liquid oxygen in the valley electricity period; the oxygen liquefaction subsystem is used for liquefying and storing oxygen by using the cold energy of liquid nitrogen in the peak electricity period; and the control module subsystem is used for controlling the nitrogen compression subsystem, the liquid oxygen vaporization subsystem and the oxygen liquefaction subsystem according to historical operation data and prediction requirements. According to the method, in the peak electricity period, oxygen which is emptied due to air separation load limitation is recycled; and in the off-peak electricity period, vaporized and recycled liquid oxygen is supplemented for air supply, the cooperative capacity of the air separation device and the downstream air utilization device is improved, air separation performance waste caused when the downstream air utilization device greatly changes is reduced, and efficient utilization of energy and stable operation of the system are achieved.

Description

Technical Field

[0001] This invention relates to the field of gas separation technology, and in particular to an air separation oxygen cyclic liquefaction and redistribution system under peak and off-peak electricity conditions. Background Technology

[0002] Under the backdrop of widespread implementation of peak-valley electricity pricing policies in energy management, the operational economy and stability of air separation units face significant challenges. Traditional air separation units, due to their technological characteristics, have complex and time-consuming start-up and shutdown processes, and struggle to achieve significant load adjustments within a short period, resulting in severely insufficient operational flexibility. Specifically, during peak electricity periods with higher prices, downstream gas-consuming units often reduce their load or even shut down. If the air separation unit continues to operate during this time, the produced oxygen cannot be effectively utilized and must be vented, resulting not only in a direct waste of valuable gas resources but also a significant decrease in the overall energy efficiency of the unit. Conversely, during off-peak electricity periods with lower prices, downstream gas demand typically peaks. However, even if the air separation unit operates continuously at its maximum design load, its gas production capacity is insufficient to meet the surge in demand, thus restricting the stability and continuity of downstream production. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention provides a periodic liquefaction and redistribution system for air-separated oxygen under peak and off-peak electricity conditions, comprising: A nitrogen compression subsystem is used to provide pressurized nitrogen during off-peak electricity periods; A liquid oxygen vaporization subsystem is used to vaporize and output stored liquid oxygen using the cooling capacity of the pressurized nitrogen during off-peak electricity periods. An oxygen liquefaction subsystem is used to liquefy and store oxygen using the cooling capacity of liquid nitrogen during peak power periods. The control module subsystem is used to control the nitrogen compression subsystem, the liquid oxygen vaporization subsystem, and the oxygen liquefaction subsystem, and to optimize the start-up and shutdown sequence and operating load of the liquid oxygen vaporization subsystem and the oxygen liquefaction subsystem based on historical operating data and predicted demand.

[0004] Preferably, the nitrogen compression subsystem includes a nitrogen compressor; The liquid oxygen vaporization subsystem includes a vaporization heat exchanger, a liquid oxygen pump, a liquid nitrogen throttle valve, and a liquid nitrogen vacuum tank connected in sequence by pipelines. The oxygen liquefaction subsystem includes a liquefaction heat exchanger, a liquid nitrogen pump, a nitrogen expander, a liquid oxygen throttle valve, and a liquid oxygen vacuum tank, which are connected in sequence by pipelines. The liquid nitrogen vacuum tank provides a cold source medium for the oxygen liquefaction subsystem and stores cold energy for the liquid oxygen vaporization subsystem.

[0005] Preferably, the control module subsystem includes: The data acquisition module is used to collect and store historical electricity price data, unit time load data of downstream gas-consuming devices, ambient temperature and humidity data, and real-time liquid level, temperature and pressure data of the liquid oxygen vacuum tank and liquid nitrogen vacuum tank in real time. The analysis and prediction module is used to train and learn the historical data based on a recurrent neural network model, predict the dynamic gas load curve within a specified scheduling period in the future, and automatically divide the cost optimization range of energy input by coupling electricity price policy information. The scheduling execution module is used to generate and issue an optimized scheduling command sequence to control the speed of the liquid nitrogen pump, the speed of the liquid oxygen pump, the opening degree of the nitrogen expander inlet guide vane, and the opening degree of the corresponding throttle valve based on the predicted gas load curve and cost optimization range, combined with real-time data from the storage tank.

[0006] Preferably, the optimized scheduling instruction refers to the start-up timing and running time of the oxygen liquefaction subsystem, the target liquefaction load adjusted based on real-time oxygen venting rate feedback, the start-up liquid level threshold and stop liquid level threshold of the liquid oxygen vaporization subsystem, and the target vaporization load adjusted based on pipeline pressure fluctuation feedback. The start-up timing is determined by combining the predicted inflection point of gas load decline and the peak start point of electricity price, and the process preparation time required for system start-up is reserved. The target liquefaction load setting must ensure that the predicted oxygen surplus is effectively stored before the end of the peak electricity price period, while not exceeding the safe filling limit of the liquid oxygen vacuum tank.

[0007] Preferably, the analysis and prediction module, within each scheduling step, uses the current system state as the initial condition and the minimum total cost over a future prediction period as the objective function to re-solve the problem. The total cost includes: The total system power consumption cost calculated based on time-of-use electricity pricing, the resource loss cost due to oxygen venting, the equipment fatigue life conversion cost due to drastic fluctuations in equipment load, and the production loss penalty cost due to failure to meet downstream demand; Furthermore, the capacity and working pressure of the liquid oxygen and liquid nitrogen vacuum tanks are limited, the flow rate and head working range determined by the characteristic curves of the liquid oxygen pump and liquid nitrogen pump are limited, the isentropic efficiency of the nitrogen expander is limited, and the minimum pipeline pressure and oxygen supply stability indicators are set to ensure continuous downstream production.

[0008] Preferably, the outlet of the nitrogen compressor is connected to the high-pressure side inlet of the vaporization heat exchanger. The high-pressure side outlet of the vaporization heat exchanger is connected to the inlet of the liquid nitrogen throttling valve. The liquid nitrogen throttling valve has a first outlet and a second outlet. The first outlet is connected to the shell-side low-pressure side of the vaporization heat exchanger to form a reflux nitrogen circuit to recover cold energy. The second outlet is connected to the inlet of the liquid nitrogen vacuum tank for storing liquefied liquid nitrogen.

[0009] Preferably, the outlet of the liquid nitrogen vacuum tank is connected to the shell-side inlet of the liquefaction heat exchanger via the liquid nitrogen pump, and the liquid nitrogen pump is driven by a variable frequency motor, the speed of which is directly controlled by the optimized scheduling command; The shell-side outlet of the liquefaction heat exchanger is connected to the inlet of the nitrogen expander; The outlet of the nitrogen expander is connected to the low-pressure side of the tube side of the liquefaction heat exchanger to form a refrigeration cycle; The high-pressure side inlet of the liquefaction heat exchanger is connected to the medium-pressure oxygen output pipeline of the air separation unit and is equipped with an oxygen flow regulating valve. The high-pressure side outlet of the liquefaction heat exchanger is connected to the inlet of the liquid oxygen throttling valve. The outlet of the liquid oxygen throttle valve is connected to the inlet of the liquid oxygen vacuum tank, which is equipped with a high-precision level gauge, a pressure sensor, and a safety relief device.

[0010] Preferably, the outlet of the liquid oxygen vacuum tank is connected to the shell-side high-pressure inlet of the vaporization heat exchanger via the liquid oxygen pump, and the liquid oxygen pump is driven by a variable frequency motor. The shell-side high-pressure outlet of the vaporization heat exchanger is connected to the oxygen supply network, and an oxygen heater, a pressure regulating valve and a flow meter are sequentially installed on the connecting pipeline to completely vaporize, reheat and adjust the subcooled liquid oxygen to the pressure and temperature required by the network before outputting it.

[0011] The present invention has at least the following beneficial effects: 1. During off-peak electricity hours with low electricity prices, the system uses the cooling capacity provided by nitrogen compression to vaporize and output stored liquid oxygen to supplement the gas supply from the pipeline network. During peak electricity hours with high electricity prices, the liquefaction process is activated to convert surplus oxygen from the air separation unit into liquid oxygen for storage, avoiding venting and waste. This not only makes full use of the peak-valley electricity price difference and significantly reduces the system's operating electricity costs, but also transforms previously wasted oxygen resources into a dispatchable strategic reserve.

[0012] 2. By setting up liquid oxygen and liquid nitrogen vacuum tanks as large buffer units and combining them with an intelligent control module subsystem, peak shaving and valley filling of gas supply capacity are achieved. The scheduling and execution module can dynamically adjust the liquefaction or vaporization load based on the predicted gas load curve and real-time pipeline pressure. During off-peak electricity or downstream gas consumption peaks, the system can quickly start the liquid oxygen vaporization process to stabilize the pipeline pressure; during peak electricity or off-peak gas consumption, it efficiently recovers excess oxygen. This composite control strategy based on predictive feedforward and real-time feedback ensures that gas supply pressure fluctuations are controlled within an extremely narrow range, effectively solving the core contradiction of insufficient gas supply during off-peak electricity periods and oxygen venting during peak electricity periods, thus guaranteeing the continuity and stability of downstream users' production. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 A flowchart of an air separation oxygen cycle liquefaction and redistribution system under peak and valley electricity conditions provided in Embodiment 1 of the present invention; Figure 2 This is a module diagram of the control module subsystem provided in Embodiment 2 of the present invention. Detailed Implementation

[0015] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; 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 explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0017] Example 1

[0018] This embodiment provides a periodic liquefaction and redistribution system for air-separated oxygen under peak and off-peak electricity conditions, such as... Figure 1 As shown, it specifically includes: A nitrogen compression subsystem is used to provide pressurized nitrogen during off-peak electricity periods; The liquid oxygen vaporization subsystem is used to vaporize stored liquid oxygen and output it during off-peak electricity periods by utilizing the cooling capacity of pressurized nitrogen. An oxygen liquefaction subsystem is used to liquefy and store oxygen using the cooling capacity of liquid nitrogen during peak power periods. The control module subsystem is used to control the nitrogen compression subsystem, liquid oxygen vaporization subsystem, and oxygen liquefaction subsystem. It is used to optimize the start-up and shutdown sequence and operating load of the liquid oxygen vaporization subsystem and the oxygen liquefaction subsystem based on historical operating data and predicted demand.

[0019] Furthermore, the aforementioned nitrogen compression subsystem includes a nitrogen compressor; The liquid oxygen vaporization subsystem includes a vaporization heat exchanger, a liquid oxygen pump, a liquid nitrogen throttle valve, and a liquid nitrogen vacuum tank, which are connected in sequence by pipelines. The oxygen liquefaction subsystem includes a liquefaction heat exchanger, a liquid nitrogen pump, a nitrogen expander, a liquid oxygen throttle valve, and a liquid oxygen vacuum tank, which are connected in sequence by pipelines. The liquid nitrogen vacuum tank provides a cold source medium for the oxygen liquefaction subsystem and stores cold energy for the liquid oxygen vaporization subsystem.

[0020] Specifically, the system comprises four main functional modules: a nitrogen compression subsystem, a liquid oxygen vaporization subsystem, an oxygen liquefaction subsystem, and a control module subsystem. In detail: During off-peak electricity hours when electricity prices are low, the nitrogen compression subsystem is activated. Utilizing the cooling energy provided by compressed nitrogen during vaporization heat exchange, pre-stored liquid oxygen is vaporized into gaseous oxygen and transported to the downstream gas supply network. During peak electricity hours when electricity prices are high, the oxygen liquefaction subsystem is activated. Utilizing the cooling energy from liquid nitrogen, excess oxygen from the air separation unit due to insufficient downstream demand is liquefied and stored in a liquid oxygen vacuum tank, achieving energy time-shifting and oxygen recovery. Crucially, the system incorporates a control module subsystem. This module intelligently schedules the start-up and shutdown sequence and operating load of the liquid oxygen vaporization and oxygen liquefaction processes based on historical operating data and future demand forecasts, thereby optimizing the system's economy, safety, and stability.

[0021] The core equipment of the nitrogen compression subsystem is the nitrogen compressor, which is used to pressurize atmospheric nitrogen from the pipeline network to the required process pressure during off-peak electricity periods. The liquid oxygen vaporization subsystem mainly consists of a vaporization heat exchanger, a liquid oxygen pump, a liquid nitrogen throttling valve, and a liquid nitrogen vacuum tank connected in sequence. Its functional path is as follows: liquid oxygen stored in the liquid oxygen vacuum tank is pressurized by the liquid oxygen pump and enters the vaporization heat exchanger to exchange heat with high-pressure nitrogen from the nitrogen compressor. The liquid oxygen absorbs heat and vaporizes for output; the cooled and liquefied nitrogen is throttled by the liquid nitrogen throttling valve, with part of it vaporizing and flowing back to recover the cooling energy, and part becoming liquid nitrogen and entering the liquid nitrogen vacuum tank for storage. The oxygen liquefaction subsystem mainly consists of a liquefaction heat exchanger, a liquid nitrogen pump, a nitrogen expander, a liquid oxygen throttling valve, and a liquid oxygen vacuum tank connected in sequence. Its functional pathway is as follows: Liquid nitrogen from the liquid nitrogen vacuum tank is pressurized by a liquid nitrogen pump and enters the liquefaction heat exchanger to exchange heat with oxygen from the air separation unit. The liquid nitrogen absorbs heat and vaporizes, while the oxygen is cooled and liquefied. The vaporized nitrogen then enters the nitrogen expander for further expansion and cooling, generating an even lower temperature, and flows back to the liquefaction heat exchanger to provide additional cooling. The liquefied oxygen is then throttled by a liquid oxygen throttling valve and stored in the liquid oxygen vacuum tank. The liquid nitrogen vacuum tank plays a dual role in this system: on the one hand, it provides the cold source medium (liquid nitrogen) required for liquefaction in the oxygen liquefaction subsystem; on the other hand, as a cold energy carrier, the liquid nitrogen stored inside is consumed during liquid oxygen vaporization to provide the cooling required for the vaporization process, realizing the transfer and allocation of cold energy between different subsystems. It is the core storage and transportation unit for the system to achieve energy and material transfer during peak and off-peak periods.

[0022] Secondly, the outlet of the nitrogen compressor is connected to the high-pressure side inlet of the tube side of the vaporization heat exchanger; The high-pressure side outlet of the vaporization heat exchanger is connected to the inlet of the liquid nitrogen throttling valve; The liquid nitrogen throttling valve has a first outlet and a second outlet. The first outlet is connected to the shell-side low-pressure side of the vaporization heat exchanger to form a reflux nitrogen circuit to recover the cooling capacity. The second outlet is connected to the inlet of the liquid nitrogen vacuum tank to store the liquefied liquid nitrogen.

[0023] Specifically, during off-peak electricity hours, atmospheric nitrogen from the pipeline first enters the nitrogen compressor and is pressurized to the required process pressure (e.g., medium to high pressure). The resulting high-temperature, high-pressure nitrogen is then directly delivered from its outlet pipeline to the high-pressure inlet of the tube side of the vaporization heat exchanger. Inside the vaporization heat exchanger, this high-pressure nitrogen flows through the tube side, indirectly exchanging heat with cryogenic liquid oxygen from the liquid oxygen pump in the shell side. The nitrogen is gradually cooled and eventually liquefied as it releases sensible and latent heat, while the liquid oxygen absorbs heat and completely vaporizes. The cooled and liquefied high-pressure liquid nitrogen flows out from the high-pressure outlet of the tube side of the vaporization heat exchanger and then enters the inlet of the liquid nitrogen throttling valve. This throttling valve has one inlet and two outlets, forming a key node for flow distribution and energy recovery: after throttling and depressurization, a portion of the liquid nitrogen instantly vaporizes to form cryogenic gaseous nitrogen, which is then returned to the low-pressure shell side of the vaporization heat exchanger through the first outlet. The refluxed cryogenic nitrogen undergoes further heat exchange with the forward-flowing materials (high-pressure nitrogen and liquid oxygen) in the shell side, fully recovering its residual cold energy. It is then ultimately output as low-pressure nitrogen or returned to the pipeline network, significantly improving the system's cooling efficiency. Simultaneously, the remaining unvaporized liquid nitrogen after throttling is transported through the second outlet to the inlet of the liquid nitrogen vacuum tank, where it is stored as a liquid refrigerant, thus providing the necessary cold source for the oxygen liquefaction subsystem during peak power periods.

[0024] Furthermore, the outlet of the liquid nitrogen vacuum tank is connected to the shell-side inlet of the liquefaction heat exchanger via a liquid nitrogen pump. The liquid nitrogen pump is driven by a variable frequency motor, and its speed is directly controlled by an optimized scheduling command. The shell-side outlet of the liquefied heat exchanger is connected to the inlet of the nitrogen expander; The outlet of the nitrogen expander is connected to the low-pressure side of the tube side of the liquefaction heat exchanger to form a refrigeration cycle; The high-pressure side inlet of the liquefied heat exchanger is connected to the medium-pressure oxygen output pipeline of the air separation unit and is equipped with an oxygen flow regulating valve. The high-pressure side outlet of the liquefied heat exchanger is connected to the inlet of the liquid oxygen throttling valve; The outlet of the liquid oxygen throttle valve is connected to the inlet of the liquid oxygen vacuum tank, which is equipped with a high-precision level gauge, pressure sensor and safety relief device.

[0025] Specifically, firstly, cryogenic liquid nitrogen stored in a liquid nitrogen vacuum tank serves as the cooling medium. It is drawn from the tank's outlet, pressurized by a liquid nitrogen pump, and then delivered to the shell-side inlet of the liquefaction heat exchanger. Here, the liquid nitrogen pump is driven by a variable frequency motor, its speed directly controlled by optimized scheduling commands generated by the control module subsystem. This allows for precise adjustment of the liquid nitrogen flow rate and pressure entering the liquefaction heat exchanger to match dynamically changing liquefaction load demands. The pressurized liquid nitrogen enters the shell side of the liquefaction heat exchanger, exchanging heat with the oxygen flowing in the tube side. After absorbing heat, the liquid nitrogen completely vaporizes and flows out from the shell-side outlet of the liquefaction heat exchanger, immediately entering the inlet of the nitrogen expander. Inside the expander, the nitrogen undergoes isentropic expansion, performing work and generating a cooling effect, significantly lowering its own temperature. This cryogenic nitrogen gas is then introduced into the low-pressure side of the tube side of the liquefied heat exchanger, where it undergoes countercurrent heat exchange with the liquid nitrogen on the shell side and the oxygen on the high-pressure side of the tube side. This further enhances the cooling effect of the entire heat exchanger, forming a highly efficient closed-loop refrigeration cycle that maximizes the recovery and utilization of the cooling energy generated by expansion work. The reheated nitrogen gas is finally transported to the atmospheric pressure nitrogen pipeline network.

[0026] On the oxygen liquefaction side, medium-pressure oxygen from the air separation unit is transported via a dedicated pipeline, and an oxygen flow regulating valve is installed before it enters the high-pressure side inlet of the liquefaction heat exchanger tube side. This valve, according to instructions from the control module, adjusts the flow rate of oxygen participating in liquefaction to ensure it matches the downstream venting rate and storage capacity. Within the liquefaction heat exchanger tube side, the oxygen is cooled step-by-step by liquid nitrogen in the shell side and cryogenic nitrogen flowing back into the tube side until it is liquefied. The liquefied liquid oxygen flows out from the high-pressure side outlet of the liquefaction heat exchanger tube side, and after being throttled and depressurized by a liquid oxygen throttling valve, it is stably injected into the liquid oxygen vacuum tank for storage. The liquid oxygen vacuum tank, as the core energy storage unit of the system, is equipped with a high-precision level gauge and pressure sensor to monitor the tank's inventory and internal pressure in real time, feeding the data back to the control module as key parameters for load regulation and safety interlocking. Simultaneously, a safety relief device installed on the tank automatically opens when the pressure abnormally increases, ensuring the safety and reliability of the storage process.

[0027] Furthermore, the outlet of the liquid oxygen vacuum tank is connected to the shell-side high-pressure inlet of the vaporization heat exchanger via a liquid oxygen pump, which is driven by a variable frequency motor. The shell-side high-pressure outlet of the vaporization heat exchanger is connected to the oxygen supply network, and an oxygen heater, a pressure regulating valve and a flow meter are installed in sequence on the connecting pipeline to completely vaporize, reheat and adjust the subcooled liquid oxygen to the pressure and temperature required by the network before output.

[0028] Specifically, liquid oxygen is stored in a liquid oxygen vacuum tank (OT), the tank outlet of which is connected to the inlet of a liquid oxygen pump (OP) via a pipeline. This pump is driven by a variable frequency motor, allowing its speed to be precisely and continuously adjusted according to optimized scheduling commands issued by the control module subsystem, thus achieving flexible control of the liquid oxygen delivery flow rate. After pressurizing the liquid oxygen, the pump delivers it to the shell-side high-pressure inlet of the vaporization heat exchanger (EVAEH). Inside the vaporization heat exchanger, the high-pressure liquid oxygen flows in the shell side, undergoing countercurrent heat exchange with the high-pressure nitrogen from the nitrogen compressor in the tube side. The liquid oxygen absorbs the cooling energy of the nitrogen (actually, the nitrogen is cooled and liquefied by the liquid oxygen, while the liquid oxygen itself gains latent heat of vaporization) and completely vaporizes. The vaporized cryogenic oxygen flows out from the shell-side high-pressure outlet of the vaporization heat exchanger and then enters the output pipeline connected to the oxygen supply network. To ensure that the output oxygen fully meets the process requirements of the downstream network, an oxygen heater, a pressure regulating valve, and a flow meter are sequentially installed on this pipeline. The function of the oxygen heater is to further reheat the gaseous oxygen, which may still be in a low-temperature state after passing through the heat exchanger, to the ambient temperature or the temperature specified by the pipeline network, so as to prevent the low-temperature gas from affecting the downstream pipeline; the pressure regulating valve is used to precisely control the pressure of the output oxygen and stabilize it within the pressure range required by the pipeline network; the flow meter is used to monitor and measure the output oxygen flow in real time, providing data support for system control and energy accounting.

[0029] Example 2

[0030] Based on the above embodiment one, this embodiment aims to provide a control module subsystem, such as Figure 2 As shown, it includes: The data acquisition module is used to collect and store historical electricity price data, unit time load data of downstream gas-consuming devices, ambient temperature and humidity data, and real-time liquid level, temperature and pressure data of liquid oxygen vacuum tank and liquid nitrogen vacuum tank in real time. The analysis and prediction module is used to train and learn from historical data based on a recurrent neural network model, predict the dynamic gas load curve within a specified scheduling period in the future, and automatically divide the cost optimization range of energy input by coupling with electricity price policy information. The scheduling execution module is used to generate and issue an optimized scheduling command sequence that controls the speed of the liquid nitrogen pump, the speed of the liquid oxygen pump, the opening degree of the nitrogen expander inlet guide vane, and the opening degree of the corresponding throttle valve based on the predicted gas load curve and cost optimization range, combined with real-time data from the storage tank.

[0031] Specifically, historical and real-time data on the grid's time-of-use electricity pricing, time-series load data for downstream gas-consuming devices, environmental temperature and humidity data affecting heat exchange efficiency, and multi-dimensional status data such as real-time liquid level, temperature, and pressure in liquid oxygen and liquid nitrogen vacuum tanks form the data foundation for system optimization decisions. The analysis and prediction module, as the decision-making layer, is the system's "intelligent brain." It incorporates a prediction model based on a recurrent neural network (RNN). This model, through continuous training and learning on historically collected time-series data on gas load and environment, can predict the dynamic gas load curve of downstream systems within a specified scheduling cycle (e.g., the next 24 hours). Simultaneously, this module couples the predicted curve with known electricity pricing policies (e.g., peak, flat, and valley periods and prices) to automatically delineate the energy input cost optimization range with the lowest operating costs (i.e., the valley period most suitable for starting high-energy-consuming liquefaction processes and the peak period most suitable for consuming stored energy). The scheduling and execution module, as the control layer, is the system's "execution arm." It receives load curves and cost optimization range information from the analysis and prediction module, and combines them with real-time data from the storage tank (such as remaining storage capacity). Using its built-in optimization algorithm, it calculates and ultimately generates and sends a specific sequence of optimized scheduling instructions to the field equipment. These instructions directly control key moving parts and regulating valves, including adjusting the inverter speeds of the liquid nitrogen and liquid oxygen pumps to change flow rates, adjusting the inlet guide vane opening of the nitrogen expander to control cooling capacity, and adjusting the opening of the liquid oxygen / liquid nitrogen throttle valves to optimize process pressure and temperature distribution, thereby translating optimization strategies into precise equipment actions.

[0032] Furthermore, the optimized scheduling instructions refer to the start-up timing and runtime of the oxygen liquefaction subsystem, the target liquefaction load adjusted based on real-time oxygen venting rate feedback, the start-up and stop-up liquid level thresholds of the liquid oxygen vaporization subsystem, and the target vaporization load adjusted based on pipeline pressure fluctuation feedback. The timing of the start-up is determined by combining the predicted inflection point of gas load decline and the peak start of electricity price, and the process preparation time required for system start-up is reserved. The target liquefaction load setting must ensure that the predicted oxygen surplus is effectively stored before the end of the peak electricity price period, while not exceeding the safe filling limit of the liquid oxygen vacuum tank.

[0033] Specifically, optimized scheduling instructions are a set of control strategies containing specific parameters and triggering conditions, mainly including: 1) Start-up timing and runtime of the oxygen liquefaction subsystem: The timing is not fixed, but is determined by the module as a whole. The system analyzes and predicts the inflection point of the gas load decline (indicating that oxygen will begin to be in surplus) and the start of the electricity price peak, and selects a reserved time point after the load inflection point and before the start of the electricity price peak to issue the start-up command. This reserved time is used for system equipment startup, process establishment and other process preparations.

[0034] 2) Target liquefaction load adjusted based on real-time oxygen venting rate feedback: During liquefaction operation, the system monitors the original oxygen venting rate of the air separation unit in real time and uses it as a feedback signal. The target liquefaction load will be dynamically adjusted to ensure that the predicted oxygen surplus plus the real-time monitored venting volume can be liquefied and stored before the end of the peak electricity price period. At the same time, the set value of this load must strictly adhere to the safe filling limit of the liquid oxygen vacuum tank to prevent overload.

[0035] 3) Start-up and Stop-up Liquid Level Thresholds of the Liquid Oxygen Vaporization Subsystem: The system sets two key liquid level points for the liquid oxygen vacuum tank. When the liquid level in the tank is higher than the set start-up liquid level threshold, it indicates that the storage is sufficient and vaporization can be started during off-peak electricity or peak gas consumption. When the liquid level drops to the stop-up liquid level threshold, in order to ensure the safety of subsequent gas supply and the system's buffer capacity, the command will stop the vaporization operation.

[0036] 4) Target vaporization load based on pipeline pressure fluctuation feedback adjustment: During the vaporization gas supply process, the system monitors the pressure of the downstream oxygen pipeline in real time. If the pressure is lower than the set value, it indicates that the demand is greater than the current gas supply, and the system will instruct to increase the target vaporization load (e.g., increase the speed of the liquid oxygen pump); conversely, the load will be reduced, thereby achieving dynamic matching between gas supply and demand and maintaining stable pipeline pressure.

[0037] Furthermore, in the above embodiments, the analysis and prediction module, within each scheduling step, uses the current system state as the initial condition and the minimum total cost within a future prediction period as the objective function to re-solve the problem. The total cost includes: The total system power consumption cost calculated based on time-of-use electricity pricing, the resource loss cost due to oxygen venting, the equipment fatigue life conversion cost due to drastic fluctuations in equipment load, and the production loss penalty cost due to failure to meet downstream demand; Furthermore, the capacity and working pressure of the liquid oxygen and liquid nitrogen vacuum tanks are limited, the flow rate and head working range determined by the characteristic curves of the liquid oxygen pump and liquid nitrogen pump are limited, the isentropic efficiency of the nitrogen expander is limited, and the minimum pipeline pressure and oxygen supply stability indicators are set to ensure continuous downstream production.

[0038] Specifically, the current system status acquired by the real-time data acquisition system serves as the initial condition for optimization calculations. This status data includes the real-time liquid level, temperature, and pressure of the liquid oxygen and liquid nitrogen vacuum tanks, the pressure and oxygen flow rate of the downstream pipeline network, and the current operating conditions of key equipment (such as liquid nitrogen pumps, liquid oxygen pumps, and nitrogen expanders). Simultaneously, the module invokes built-in prediction models (such as recurrent neural networks trained on historical data) to perform rolling predictions of the dynamic gas load curve and time-of-use electricity price for a future prediction cycle (e.g., the next 24 hours).

[0039] Building upon this, the module constructs and solves a constrained optimization problem with the objective function of minimizing the total cost over the future forecast period. Total cost is a comprehensive economic indicator, specifically including: 1) Total system power consumption cost: Based on the time-of-use electricity pricing policy, accurately calculate the power consumption cost of the nitrogen compressor, various pumps and auxiliary equipment during the planned operating period; 2) The resource loss cost caused by oxygen venting, and the value of oxygen that was forced to be vented due to failure to liquefy and store it in time; 3) Equipment fatigue life conversion cost: Through mathematical models, the additional mechanical stress caused by frequent or drastic changes in load commands to rotating equipment such as pumps and expanders is converted into economic costs to encourage stable operation and extend equipment life. 4) Production loss penalty costs incurred due to failure to meet downstream demand are used to ensure gas supply reliability. Once a gas shortage is predicted, this cost item will increase significantly, driving the optimization scheme to prioritize supply.

[0040] The capacity and operating pressure of the liquid oxygen and liquid nitrogen vacuum tanks are limited to ensure storage safety; the liquid oxygen and liquid nitrogen pumps operate within the flow rate and head operating range determined by their characteristic curves, and the frequency converter speed control command must be matched accordingly; the operating point of the nitrogen expander must take into account its isentropic efficiency limit to ensure refrigeration efficiency; and the minimum pipeline pressure and oxygen supply stability indicators are set to ensure the continuity of downstream production, ensuring that the output oxygen pressure, temperature and flow rate meet the process requirements.

[0041] Finally, at each scheduling step, the analysis and prediction module generates a set of optimized scheduling instructions by solving the aforementioned constrained optimization problem. This instruction sequence specifies the start-up and shutdown timings of the oxygen liquefaction subsystem and the liquid oxygen vaporization subsystem within the next certain time window, the target speeds of each variable frequency pump, the expander guide vane opening, and the openings of relevant throttle valves. This rolling optimization mechanism enables the system to dynamically respond to load and electricity price changes, minimizing the total cost of operation throughout the entire lifecycle while satisfying all safety and process constraints, thereby achieving the core invention objective of economical, stable, and efficient system operation.

[0042] Example 3

[0043] This invention provides a non-transitory computer-readable storage medium storing at least one instruction or at least one program segment, which is loaded and executed by a processor to implement the following steps: A time-series database containing multi-dimensional historical operating parameters is constructed through the data acquisition module of the control module subsystem. The control module subsystem analyzes and predicts the module, and uses the trained prediction model to continuously output the gas demand prediction curve and time-of-use electricity price information for future cycles. The real-time collected system status data, along with the prediction curves of the control module subsystem and electricity price information, are input into the rolling optimization model of the control module subsystem to solve for the optimal equipment scheduling sequence from the current time to the future prediction time domain, including the planned start and stop times and load setpoints of each major device. During peak power periods or when oxygen venting is detected, the instructions for the oxygen liquefaction system in the optimal equipment scheduling sequence of the control module subsystem are executed. By adjusting the speed of the liquid nitrogen pump, the opening of the nitrogen expander, and the liquid oxygen throttle valve of the control module subsystem, excess oxygen is recovered with dynamically changing liquefaction load. During off-peak electricity hours or when the pipeline pressure is detected to be lower than the set threshold, the instructions for the liquid oxygen vaporization system in the optimal equipment scheduling sequence of the control module subsystem are executed. By adjusting the speed of the liquid oxygen pump, the opening of the liquid nitrogen throttle valve, and the power of the oxygen heater in the control module subsystem, the stored liquid oxygen is released to match the vaporization load with demand, thereby stabilizing the pipeline supply.

[0044] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. 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 embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can 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), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0045] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to 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.

[0046] Example 4

[0047] This invention provides an electronic device, including a processor and a memory, wherein the memory stores at least one instruction or at least one program segment, and the at least one instruction or the at least one program segment is loaded and executed by the processor to implement the following steps: A time-series database containing multi-dimensional historical operating parameters is constructed through the data acquisition module of the control module subsystem. The control module subsystem analyzes and predicts the module, and uses the trained prediction model to continuously output the gas demand prediction curve and time-of-use electricity price information for future cycles. The real-time collected system status data, along with the prediction curves of the control module subsystem and electricity price information, are input into the rolling optimization model of the control module subsystem to solve for the optimal equipment scheduling sequence from the current time to the future prediction time domain, including the planned start and stop times and load setpoints of each major device. During peak power periods or when oxygen venting is detected, the instructions for the oxygen liquefaction system in the optimal equipment scheduling sequence of the control module subsystem are executed. By adjusting the speed of the liquid nitrogen pump, the opening of the nitrogen expander, and the liquid oxygen throttle valve of the control module subsystem, excess oxygen is recovered with dynamically changing liquefaction load. During off-peak electricity hours or when the pipeline pressure is detected to be lower than the set threshold, the instructions for the liquid oxygen vaporization system in the optimal equipment scheduling sequence of the control module subsystem are executed. By adjusting the speed of the liquid oxygen pump, the opening of the liquid nitrogen throttle valve, and the power of the oxygen heater in the control module subsystem, the stored liquid oxygen is released to match the vaporization load with demand, thereby stabilizing the pipeline supply.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A periodic liquefaction and redistribution system for air-separated oxygen under peak and off-peak electricity conditions, characterized in that, include: A nitrogen compression subsystem is used to provide pressurized nitrogen during off-peak electricity periods; A liquid oxygen vaporization subsystem is used to vaporize and output stored liquid oxygen using the cooling capacity of the pressurized nitrogen during off-peak electricity periods. An oxygen liquefaction subsystem is used to liquefy and store oxygen using the cooling capacity of liquid nitrogen during peak power periods. The control module subsystem is used to control the nitrogen compression subsystem, the liquid oxygen vaporization subsystem, and the oxygen liquefaction subsystem, and to optimize the start-up and shutdown sequence and operating load of the liquid oxygen vaporization subsystem and the oxygen liquefaction subsystem based on historical operating data and predicted demand.

2. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 1, characterized in that, The nitrogen compression subsystem includes a nitrogen compressor; The liquid oxygen vaporization subsystem includes a vaporization heat exchanger, a liquid oxygen pump, a liquid nitrogen throttle valve, and a liquid nitrogen vacuum tank connected in sequence by pipelines. The oxygen liquefaction subsystem includes a liquefaction heat exchanger, a liquid nitrogen pump, a nitrogen expander, a liquid oxygen throttle valve, and a liquid oxygen vacuum tank, which are connected in sequence by pipelines. The liquid nitrogen vacuum tank provides a cold source medium for the oxygen liquefaction subsystem and stores cold energy for the liquid oxygen vaporization subsystem.

3. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 2, characterized in that, The control module subsystem includes: The data acquisition module is used to collect and store historical electricity price data, unit time load data of downstream gas-consuming devices, ambient temperature and humidity data, and real-time liquid level, temperature and pressure data of the liquid oxygen vacuum tank and liquid nitrogen vacuum tank in real time. The analysis and prediction module is used to train and learn the historical data based on a recurrent neural network model, predict the dynamic gas load curve within a specified scheduling period in the future, and automatically divide the cost optimization range of energy input by coupling electricity price policy information. The scheduling execution module is used to generate and issue an optimized scheduling command sequence to control the speed of the liquid nitrogen pump, the speed of the liquid oxygen pump, the opening degree of the nitrogen expander inlet guide vane, and the opening degree of the corresponding throttle valve based on the predicted gas load curve and cost optimization range, combined with real-time data from the storage tank.

4. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 3, characterized in that, The optimized scheduling instructions refer to the start-up timing and runtime of the oxygen liquefaction subsystem, the target liquefaction load adjusted based on real-time oxygen venting rate feedback, the start-up liquid level threshold and stop liquid level threshold of the liquid oxygen vaporization subsystem, and the target vaporization load adjusted based on pipeline pressure fluctuation feedback. The start-up timing is determined by combining the predicted inflection point of gas load decline and the peak start point of electricity price, and the process preparation time required for system start-up is reserved. The target liquefaction load setting must ensure that the predicted oxygen surplus is effectively stored before the end of the peak electricity price period, while not exceeding the safe filling limit of the liquid oxygen vacuum tank.

5. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 4, characterized in that, Within each scheduling step, the analysis and prediction module uses the current system state as the initial condition and the goal of minimizing the total cost over the next prediction period as the objective function to re-solve the problem. The total cost includes: The total system power consumption cost calculated based on time-of-use electricity pricing, the resource loss cost due to oxygen venting, the equipment fatigue life conversion cost due to drastic fluctuations in equipment load, and the production loss penalty cost due to failure to meet downstream demand; Furthermore, the capacity and working pressure of the liquid oxygen and liquid nitrogen vacuum tanks are limited, the flow rate and head working range determined by the characteristic curves of the liquid oxygen pump and liquid nitrogen pump are limited, the isentropic efficiency of the nitrogen expander is limited, and the minimum pipeline pressure and oxygen supply stability indicators are set to ensure continuous downstream production.

6. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 2, characterized in that, The outlet of the nitrogen compressor is connected to the high-pressure side inlet of the vaporization heat exchanger. The high-pressure side outlet of the vaporization heat exchanger is connected to the inlet of the liquid nitrogen throttling valve. The liquid nitrogen throttling valve has a first outlet and a second outlet. The first outlet is connected to the shell-side low-pressure side of the vaporization heat exchanger to form a reflux nitrogen circuit to recover cold energy. The second outlet is connected to the inlet of the liquid nitrogen vacuum tank for storing liquefied liquid nitrogen.

7. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 6, characterized in that, The outlet of the liquid nitrogen vacuum tank is connected to the shell-side inlet of the liquefaction heat exchanger via the liquid nitrogen pump. The liquid nitrogen pump is driven by a variable frequency motor, and its speed is directly controlled by the optimized scheduling command. The shell-side outlet of the liquefaction heat exchanger is connected to the inlet of the nitrogen expander; The outlet of the nitrogen expander is connected to the low-pressure side of the tube side of the liquefaction heat exchanger to form a refrigeration cycle; The high-pressure side inlet of the liquefaction heat exchanger is connected to the medium-pressure oxygen output pipeline of the air separation unit and is equipped with an oxygen flow regulating valve. The high-pressure side outlet of the liquefaction heat exchanger is connected to the inlet of the liquid oxygen throttling valve. The outlet of the liquid oxygen throttle valve is connected to the inlet of the liquid oxygen vacuum tank, which is equipped with a high-precision level gauge, a pressure sensor, and a safety relief device.

8. The air separation oxygen periodic liquefaction and redistribution system under peak and off-peak electricity conditions according to claim 7, characterized in that, The outlet of the liquid oxygen vacuum tank is connected to the shell-side high-pressure inlet of the vaporization heat exchanger via the liquid oxygen pump, and the liquid oxygen pump is driven by a variable frequency motor. The shell-side high-pressure outlet of the vaporization heat exchanger is connected to the oxygen supply network, and an oxygen heater, a pressure regulating valve and a flow meter are sequentially installed on the connecting pipeline to completely vaporize, reheat and adjust the subcooled liquid oxygen to the pressure and temperature required by the network before outputting it.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the air separation oxygen cyclic liquefaction and redistribution system under peak-valley electricity conditions as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the air-separated oxygen periodic liquefaction and redistribution system under peak-valley electricity conditions as described in any one of claims 1 to 8.

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