Oxygen injection control system based on dynamic environment variable compensation

Abstract

The utility model provides an oxygen injection control system based on dynamic environment variable compensation, and aims to solve the non-linear problem of oxygen content control under environment variable disturbance. Comprising a main oxygen spraying pipeline, an oxygen supplementing pipeline connected with the main oxygen spraying pipeline in parallel, a PLC (Programmable Logic Controller) and a PID (Proportion Integration Differentiation) controller which are respectively connected with the main oxygen spraying pipeline and the oxygen supplementing pipeline and are used for controlling the main oxygen spraying pipeline and the oxygen supplementing pipeline, and an oxygen content measuring pipeline which is in communication connection with the PID controller, the oxygen control system selectively controls the main oxygen spraying pipeline and / or the oxygen supplementing pipeline to be opened or closed.

Description

Technical Field

[0001] This utility model relates to the field of industrial gas control technology, and in particular to an oxygen injection control system based on dynamic environmental variable compensation, which is suitable for complex working conditions where precise control of oxygen content in closed-loop fluid equipment is required. Background Technology

[0002] In existing technologies, oxygen injection control systems typically use the oxygen content (ppm value) within the equipment as the direct feedback quantity, achieving closed-loop control by adjusting valve opening or the switching time of flow valves. However, this approach has significant drawbacks:

[0003] 1. Severe interference from environmental variables: The dynamic changes in temperature and pressure inside the equipment cause a wide range of fluctuations in the actual number of oxygen molecules corresponding to a unit ppm value (the difference can be more than ten times). Traditional single feedback control cannot adapt to this nonlinear relationship.

[0004] 2. Poor control stability: The control logic that directly correlates the ppm difference with the valve action is prone to overshoot or undershoot, and conventional PID parameter tuning is difficult to cover all operating conditions;

[0005] 3. High debugging costs: When relying on multiple sets of PID parameters for segmented control, the robustness boundary of the system is limited, the debugging cycle is long, and the risk of runaway cannot be completely avoided. Utility Model Content

[0006] The purpose of this invention is to provide an oxygen injection control system based on dynamic environmental variable compensation, which aims to solve the nonlinear problem of oxygen content control under environmental variable disturbances.

[0007] The embodiments of this utility model are implemented as follows:

[0008] An oxygen injection control system based on dynamic environmental variable compensation includes a main oxygen injection pipeline, an oxygen supplementation pipeline connected in parallel with the main oxygen injection pipeline, a PLC controller and a PID controller connected to and controlling the main oxygen injection pipeline and the oxygen supplementation pipeline respectively, and an oxygen content measurement pipeline communicatively connected to the PID controller. The two ends of the main oxygen injection pipeline and the oxygen supplementation pipeline are respectively connected to a gas source pretreatment pipeline and an oxygen injection rake. The oxygen control system selectively controls the opening or closing of the main oxygen injection pipeline and / or the oxygen supplementation pipeline.

[0009] In a preferred embodiment of the present invention, the main oxygen injection pipeline includes a first pressure and temperature sensor, a first pneumatic regulating valve, a first flow meter, a first pneumatic valve, and a second pressure and temperature sensor connected in sequence, and the input end of the first pressure and temperature sensor is connected to the gas source pretreatment pipeline.

[0010] In a preferred embodiment of this utility model, the above-mentioned oxygen replenishment pipeline includes three parallel oxygen replenishment pipelines: a large oxygen replenishment pipeline, a medium oxygen replenishment pipeline, and a small oxygen replenishment pipeline. The large oxygen replenishment pipeline includes a second pneumatic regulating valve, a second flow meter, and a second pneumatic valve connected in sequence. The medium oxygen replenishment pipeline includes a third pneumatic valve and a first gas mass flow controller connected in sequence. The small oxygen replenishment pipeline includes a fourth pneumatic valve and a second gas mass flow controller connected in sequence. Each of the three oxygen replenishment pipelines is equipped with a check valve at its output end, and a safety valve is installed on the converging pipeline of the three oxygen replenishment pipelines.

[0011] In a preferred embodiment of this utility model, the above-mentioned gas source pretreatment pipeline includes an air input end, an oxygen input end, a first filter, a second filter, a first automatic pressure controller, a second automatic pressure controller, and a second safety valve; the output end of the air input end is sequentially connected to the first filter, the first automatic pressure controller, and the second safety valve; the output end of the oxygen input end is sequentially connected to the second filter, the second automatic pressure controller, and the second safety valve, and the output end of the second safety valve is connected to the input end of the main oxygen injection pipeline or the oxygen supplementation pipeline.

[0012] In a preferred embodiment of the present invention, the above-mentioned gas source pretreatment pipeline further includes a fifth pneumatic valve, a gas preprocessor and a dew point meter connected in sequence, wherein the fifth pneumatic valve is connected to the pipeline between the first filter and the first automatic pressure controller.

[0013] In a preferred embodiment of this utility model, a pressure sensor and a temperature sensor are further provided on the pipelines of the first automatic pressure controller and the second automatic pressure controller.

[0014] The beneficial effects of this utility model embodiment are:

[0015] 1. The design includes a main oxygen injection pipeline and an oxygen replenishment pipeline. Air and pure oxygen are separated into two lines. The main oxygen injection pipeline is a high-flow gas path, and the oxygen replenishment pipeline is a low-flow gas path. The low-flow gas path is further divided into three paths: large, medium, and small. Then, based on the analysis data from the pressure detection port and the oxygen analysis port, the appropriate flow rate is supplied in real time. Various valves automatically adjust the flow rate according to the supply demand, and high-precision injection requirements are achieved through multiple oxygen injection pipelines.

[0016] 2. By using dynamic environmental compensation, the ppm deviation is converted into an absolute oxygen molecule number control quantity, eliminating temperature and pressure interference, and reducing the control error to within ±3%.

[0017] 3. The composite control strategy reduces overshoot to less than 5% and shortens response time by 40%.

[0018] 4. It can adapt to a wide range of operating conditions where the number of oxygen molecules fluctuates by more than 10 times, reducing commissioning costs by more than 60%. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the pipeline connections of the oxygen injection control system according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the actual pipeline connection of the oxygen injection control system according to an embodiment of the present utility model;

[0022] Icons: Main oxygen injection line 110; First pressure and temperature sensor 111; First pneumatic regulating valve 112; First flow meter 113; First pneumatic valve 114; Second pressure and temperature sensor 115; Oxygen supply line 120; Second pneumatic regulating valve 121; Second flow meter 122; Second pneumatic valve 123; Third pneumatic valve 124; First gas mass flow controller 125; Fourth pneumatic valve 126; Second gas mass flow controller 127; Check valve 128; Safety valve 129; Oxygen content measurement line 130; Gas source pretreatment line 140; Air input terminal 141; Oxygen input terminal 142; First filter 143; Second filter 144; First automatic pressure controller 145; Second automatic pressure controller 146; Fifth pneumatic valve 147; Gas preprocessor 148; Dew point meter 149. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0029] First Embodiment

[0030] Please see Figure 1 and Figure 2 This embodiment provides an oxygen injection control system based on dynamic environmental variable compensation, including a main oxygen injection pipeline 110, an oxygen supplementation pipeline 120 connected in parallel with the main oxygen injection pipeline 110, a PLC controller and a PID controller that are respectively connected to and control the main oxygen injection pipeline 110 and the oxygen supplementation pipeline 120, and an oxygen content measurement pipeline 130 that is communicatively connected to the PID controller.

[0031] The main oxygen injection line 110 handles 85%–95% of the injection tasks and is controlled by a PLC controller. It is used for rapid response and accompaniment to liquid nitrogen injection, avoiding overshoot, minimizing or eliminating overshoot, and eliminating interference from random liquid nitrogen injection. The supplemental oxygen line 120 uses real-time oxygen content data from the closed-loop fluid equipment, such as by acquiring the oxygen content difference in PPM, converting it into an oxygen molecule quantity difference, and then into an oxygen mass difference. A PID controller uses this oxygen molecule quantity difference or oxygen mass difference to construct control measures, thereby controlling the valves in the supplemental oxygen line 120.

[0032] The main oxygen injection line 110 and the supplementary oxygen line 120 are connected at both ends to the gas source pretreatment line 140 and the oxygen injection rake, respectively. The injected gas source needs to undergo pretreatment and pass dew point detection before it can be injected into the closed-loop fluid equipment through the oxygen injection rake. The oxygen control system selectively controls the opening or closing of the main oxygen injection line 110 and / or the supplementary oxygen line 120. It can choose to inject oxygen-containing flow through the main oxygen injection line 110, or only through the supplementary oxygen line 120, or both. The system adopts a robust enhancement mechanism, introduces a gain scheduling strategy, switches control parameters according to operating condition intervals, and sets parameter boundaries through the Lyapunov stability criterion to ensure global convergence of the system.

[0033] Specifically, the main oxygen injection pipeline 110 serves as a feedforward channel, calculating the theoretical oxygen demand based on real-time temperature and pressure to drive valve pre-adjustment. It includes a first pressure and temperature sensor 111, a first pneumatic regulating valve 112, a first flow meter 113, a first pneumatic valve 114, and a second pressure and temperature sensor 115 connected in sequence. The input end of the first pressure and temperature sensor 111 is connected to the gas source pretreatment pipeline 140. The dry gas delivery pipeline and valve assembly are configured for a maximum flow rate of 1400 Nm³. 3 / h design, with an additional 20% safety margin (i.e., design flow rate ≥ 1680 Nm³). 3 / h), to ensure gas supply capacity under extreme operating conditions.

[0034] The oxygen supply pipeline 120 is further refined to improve the accuracy of oxygen content control. It includes three parallel oxygen supply pipelines 120: a large, a medium, and a small oxygen supply pipeline. The large oxygen supply pipeline 120 includes a second pneumatic regulating valve 121, a second flow meter 122, and a second pneumatic valve 123 connected in sequence. The medium oxygen supply pipeline 120 includes a third pneumatic valve 124 and a first gas mass flow controller 125 connected in sequence. The small oxygen supply pipeline 120 includes a fourth pneumatic valve 126 and a second gas mass flow controller 127 connected in sequence. Each of the three oxygen supply pipelines 120 is equipped with a check valve 128 at its output end, and a safety valve 129 is installed on the converging pipeline of the three oxygen supply pipelines 120. A multi-sensor network is configured to collect real-time data on temperature, pressure, and oxygen content within the equipment.

[0035] In this embodiment, the oxygen supply line 120 serves as a feedback channel. With the compensated oxygen molecule number deviation as input, the fuzzy PID algorithm is used to dynamically adjust the parameters (proportional coefficient Kp, integral time Ti, and derivative time Td) to suppress overshoot and hysteresis.

[0036] Before entering the equipment, the gas source needs to undergo purification treatment. Its gas source pretreatment pipeline 140 includes an air inlet 141, an oxygen inlet 142, a first filter 143, a second filter 144, a first automatic pressure controller 145, a second automatic pressure controller 146, and a second safety valve. The output of the air inlet 141 is sequentially connected to the first filter 143, the first automatic pressure controller 145, and the second safety valve. The output of the oxygen inlet 142 is sequentially connected to the second filter 144, the second automatic pressure controller 146, and the second safety valve. The output of the second safety valve is connected to the input of the main oxygen injection pipeline 110 or the supplementary oxygen pipeline 120. Pressure sensors and temperature sensors are also installed on the first automatic pressure controller 145 and the second automatic pressure controller 146 pipelines.

[0037] Before entering the equipment, the gas source also needs to be tested for dew point. The gas source pretreatment pipeline 140 also includes a fifth pneumatic valve 147, a gas preprocessor 148 and a dew point meter 149 connected in sequence. The fifth pneumatic valve 147 is connected to the pipeline between the first filter 143 and the first automatic pressure controller 145.

[0038] In this embodiment, the maximum flow rate of the dry gas available for the oxygen injection system is approximately 1400 Nm3 / h. The piping and valve assembly in this scheme will be designed with a certain safety margin to cover the flow rate design requirement of 1400 Nm3 / h.

[0039] The final controlled variable in the oxygen injection process is the oxygen content in ppm (parts per second), i.e., the ratio of oxygen molecules to nitrogen. However, since the temperature and pressure of the equipment are highly variable, the total amount of nitrogen molecules stored in the entire equipment varies over a wide range under different temperature and pressure conditions. Therefore, the number of oxygen molecules corresponding to 1 ppm is also a wide-range variable, differing by up to ten times under different experimental conditions. The interference of temperature and pressure as process variables on control is particularly critical. If a single ppm difference is directly used to correspond to the opening degree of an electric valve in a gas pipeline, or the opening and closing time of a pneumatic valve controlled by a flow valve, as long as a single ppm difference corresponds to only one oxygen injection quantity, the control system's control result for the oxygen content in the equipment will either be overshoot or undershoot, with insufficient response. Only in very rare cases will it accidentally correspond to a reasonable oxygen injection quantity. Even with PID feedback control and batch air injection, a single PID controller with three parameters can only maintain system output stability against disturbances within a certain range. However, since the number of oxygen molecules corresponding to 1 ppm can vary by more than tenfold under different operating conditions, overshoot and underresponse are highly probable. Later debugging will be extremely difficult, potentially wasting a significant amount of time, and finding suitable PID parameters may still be challenging. Even using multiple sets of PID parameters to correspond to segmented ppm differences, a control system still has its robust gain and phase boundaries. Multiple sets of PID parameters may not effectively cover all operating conditions, resulting in varying response times and potential system crashes under certain conditions. More importantly, finding multiple sets of PID parameters further increases debugging time and difficulty, leading to high debugging costs. In short, directly using ppm differences for feedback control will make achieving the specified control accuracy extremely difficult.

[0040] To address the aforementioned issues, the main control logic proposed in this embodiment is to first calculate the required number of oxygen molecules based on the ppm difference according to different total temperature, total pressure, and test conditions, and then convert it into the required air mass. Air mass is an absolute value, and a one-to-one correspondence can be established between the injected air mass and the opening degree and duration of the electric valve or the opening and closing duration of a pneumatic valve controlled by a flow valve. The control system can then eliminate the interference of environmental variables to the greatest extent and inject a relatively accurate number of oxygen molecules, so that the ppm can reach the target value as much as possible under different test conditions. In this embodiment, oxygen molecules will be injected according to a proportion of the calculated value, such as 95% (to avoid overshoot). This is the first step, which is mainly accomplished through the main oxygen injection pipeline 110110.

[0041] Secondly, since feedforward control uses the ideal gas equation (PV = nRT) to estimate the oxygen injection rate, this equation is a calculated value under assumed conditions. Furthermore, the equipment volume V calculated using the ideal gas equation may also have errors, inevitably leading to a difference between the calculated oxygen injection requirement and the actual value. While this difference can be corrected using other equations, such as the van der Waals gas equation, or by adding its parameter terms, simulation values ​​can also be used in the feedforward control later. In addition to using environmental variables to calculate the oxygen demand (regardless of which ideal gas equation or simulation calculation is used) to achieve the feedforward control effect, this embodiment will also use PID control for the final closed-loop control to correct this calculation difference. Because feedforward control largely eliminates the interference of environmental variables, the subsequent calibration and PID parameter tuning of this control system are relatively easy. Since the device is a unidirectional, single-variable system, it currently only allows the injection of oxygen molecules in this embodiment. To avoid overshoot, this embodiment considers using a PID parameter group with overdamped or critically damped characteristics for closed-loop control to correct the error. This step is mainly accomplished through the oxygen supply line 120120.

[0042] Third, to address the issue of intermittent and irregular liquid nitrogen injection by a certain device to control total temperature, this embodiment also incorporates an automatic accompanying injection control to eliminate the interference of this factor on stable ppm. When the temperature control system of the device starts operating, the accompanying injection mode (monitoring mode to maintain stable ppm) of the oxygen content control system will also be activated. This accompanying injection control first acquires data from the liquid nitrogen controller in real time, such as reading the liquid nitrogen injection flow rate and valve opening / closing duration data, and also reads continuous data from the oxygen analyzer. The average ppm reading of the oxygen analyzer in the 5 seconds before liquid nitrogen injection is used as the control target. Then, based on the liquid nitrogen injection flow rate, the required oxygen flow rate to stabilize ppm (the oxygen flow rate to offset the liquid nitrogen) can be calculated. From the oxygen flow rate, the required air flow rate at a certain gas pressure in the pipeline can be calculated. The accompanying injection mode is always on, with the PLC controller controlling the pneumatic diaphragm regulating valve to control the gas flow rate in the pipeline, or controlling the pneumatic switching valve based on the mass flow meter reading, delivering the corresponding oxygen according to the required air flow rate and duration to ensure a stable ppm value.

[0043] In summary, this embodiment uses preliminary calculations to complete the large-flow quantitative oxygen injection and employs PLC feedforward control. Regardless of any interference, since the total volume of the equipment is a constant, and pressure and temperature are measured values, an ideal gas estimate can be obtained for the number of moles of gas in the equipment. During high-flow injection, an oxygen injection volume is calculated based on this theoretical value, and 80% to 90% of this theoretical injection volume is injected (this can be increased to 95% or even higher later to improve system response speed). After the system is basically stable, the final precise replenishment is completed using PID control through a small-flow pipeline, based on the ppm reading of the oxygen analyzer.

[0044] This specification describes examples of embodiments of the present invention, but does not imply that these embodiments illustrate and describe all possible forms of the present invention. It should be understood that the embodiments in the specification can be implemented in various alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or reduced to show details of specific components. The specific structural and functional details disclosed should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to implement the present invention in various forms. Those skilled in the art will understand that multiple features illustrated and described with reference to any of the drawings can be combined with features illustrated in one or more other drawings to form embodiments not explicitly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and variations of features consistent with the teachings of the present invention may be used as needed for specific applications or implementations.

[0045] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An oxygen injection control system based on dynamic environmental variable compensation, characterized in that, The system includes a main oxygen injection pipeline, an oxygen supplementation pipeline connected in parallel with the main oxygen injection pipeline, a PLC controller and a PID controller that are respectively connected to and control the main oxygen injection pipeline and the oxygen supplementation pipeline, and an oxygen content measurement pipeline that is communicatively connected to the PID controller. The two ends of the main oxygen injection pipeline and the oxygen supplementation pipeline are respectively connected to a gas source pretreatment pipeline and an oxygen injection rake. The oxygen control system selectively controls the opening or closing of the main oxygen injection pipeline and / or the oxygen supplementation pipeline.

2. The oxygen injection control system based on dynamic environmental variable compensation according to claim 1, characterized in that, The main oxygen injection pipeline includes a first pressure and temperature sensor, a first pneumatic regulating valve, a first flow meter, a first pneumatic valve, and a second pressure and temperature sensor connected in sequence. The input end of the first pressure and temperature sensor is connected to the gas source pretreatment pipeline.

3. The oxygen injection control system based on dynamic environmental variable compensation according to claim 1, characterized in that, The oxygen supply pipeline includes three parallel oxygen supply pipelines: a large, a medium, and a small oxygen supply pipeline. The large oxygen supply pipeline includes a second pneumatic regulating valve, a second flow meter, and a second pneumatic valve connected in sequence. The medium oxygen supply pipeline includes a third pneumatic valve and a first gas mass flow controller connected in sequence. The small oxygen supply pipeline includes a fourth pneumatic valve and a second gas mass flow controller connected in sequence. Each of the three oxygen supply pipelines is equipped with a check valve at its output end, and a safety valve is installed on the converging pipeline of the three oxygen supply pipelines.

4. The oxygen injection control system based on dynamic environmental variable compensation according to claim 1, characterized in that, The gas source pretreatment pipeline includes an air input terminal, an oxygen input terminal, a first filter, a second filter, a first automatic pressure controller, a second automatic pressure controller, and a second safety valve; the output terminal of the air input terminal is sequentially connected to the first filter, the first automatic pressure controller, and the second safety valve; the output terminal of the oxygen input terminal is sequentially connected to the second filter, the second automatic pressure controller, and the second safety valve, and the output terminal of the second safety valve is connected to the input terminal of the main oxygen injection pipeline or the supplementary oxygen pipeline.

5. The oxygen injection control system based on dynamic environmental variable compensation according to claim 4, characterized in that, The gas source pretreatment pipeline also includes a fifth pneumatic valve, a gas preprocessor, and a dew point meter connected in sequence. The fifth pneumatic valve is connected to the pipeline between the first filter and the first automatic pressure controller.

6. The oxygen injection control system based on dynamic environmental variable compensation according to claim 5, characterized in that, Pressure sensors and temperature sensors are also installed on the pipelines of the first and second automatic pressure controllers.

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