A gas mixing control system and method for preventing freezing of a gas storage and oxidation shaft

Abstract

The present application belongs to the field of coal mine safety and coal gas utilization, and discloses a gas mixing control system for preventing freezing of a gas heat accumulation and oxidation shaft, which comprises a mixing device, a gas flow regulating valve, a mixed gas concentration measuring sensor and a controller. The mixed gas concentration measuring sensor is provided as at least two, and the control concentration value used by the controller is obtained by taking the arithmetic mean of the measured values of each mixed gas concentration measuring sensor. The control system uses the concentration difference between the upper and lower limits of the mixed gas concentration as a buffer zone, and continuously adjusts the opening of the low-concentration gas flow regulating valve at a certain frequency based on the mixed gas concentration monitoring value within a set time period, so that the mixed gas concentration is smoothly adjusted to the set operating target value. The present application also relates to a gas mixing control method.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety and coal mine gas utilization, and specifically relates to a gas mixing control system and method for gas thermal oxidation wellbore antifreeze. Background Technology

[0002] If large amounts of low-concentration methane from coal mines are directly released into the atmosphere, it will result in both greenhouse gas emissions and a significant waste of energy, which does not meet the development requirements of energy conservation, emission reduction, and carbon peaking / carbon neutrality.

[0003] Existing gas regenerative oxidation technology can oxidize low-concentration methane that cannot be directly combusted, releasing heat that can be used for wellbore antifreeze. There are existing engineering cases using this technology for wellbore antifreeze. However, research and literature review reveal that current gas regenerative oxidation wellbore antifreeze processes require the introduction of air into the low-concentration methane to reduce its concentration to below 1.2% before it enters the regenerative oxidation unit. However, low-concentration methane extraction suffers from frequent and significant variations in flow rate and concentration. Changes in the parameters of the low-concentration methane will lead to changes in the concentration of the mixed methane gas entering the regenerative oxidation unit.

[0004] In existing technologies, the concentration of blended methane is mostly adjusted manually or using PID control. Manual adjustment places high demands on operators and imposes a heavy workload on them. For example, patents CN202310442792.7 (a low-concentration methane and high-concentration methane blending device) and CN202011448775.7 (a high-low concentration methane mixing device and its usage method) mainly concern the structure of the specific blending device or the use of heating to improve the blending effect and efficiency. However, they do not specifically address how to automatically adjust the blended methane concentration to meet the requirements of the methane regenerative oxidation wellbore antifreeze process under frequent and significant fluctuations in low-concentration methane conditions. PID control, on the other hand, is prone to overshoot if the response is too rapid; conversely, a slower response may fail to respond promptly to changes in low-concentration methane, ultimately leading to the blended methane concentration exceeding 1.2%, resulting in unsafe conditions and potentially triggering the interlocking shutdown of the entire system. For example, patent CN202211365589.6, "A Method for Controlling Gas Mixing Concentration Based on Improved Fuzzy Neural Network PID," incorporates the gas concentration difference and the rate of change of the concentration difference into the calculation of control parameters in the PID control model, employing PID control. This method can predict the concentration change trend in advance by observing the rate of change of the concentration difference, and can improve the overshoot phenomenon in the PID adjustment process. However, its adaptability to frequent and large-scale changes in low-concentration gas is limited.

[0005] Therefore, there are few reports on gas mixing control methods in existing gas regenerative oxidation wellbore antifreeze. The main issues are that the gas regenerative oxidation process technology is described simply, but the specific control methods are not clearly explained. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a gas blending control system and method for gas storage and oxidation wellbore antifreeze, which aims to solve the problems existing in the gas blending concentration adjustment in the prior art, so as to realize the automatic adjustment of the blended gas concentration under the condition of irregular, frequent and large-scale changes in the gas extraction working conditions, while ensuring that the blended gas concentration will not exceed the alarm interlock value or fall below the device shutdown concentration during the automatic adjustment process.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a gas blending control system for antifreezing of gas-fired thermal oxidation well shafts, comprising: a blending device for blending low-concentration gas and air / exhaust gas; a gas flow regulating valve installed before the low-concentration gas enters the blending device; a blended gas concentration measuring sensor installed after the blending device; and a controller for electrically connecting to the gas flow regulating valve and the blended gas concentration measuring sensor, respectively. At least two blended gas concentration measuring sensors are used, and the control concentration value used by the controller is obtained by taking the arithmetic mean of the measured values ​​from each blended gas concentration measuring sensor. Using this scheme, the blending of low-concentration gas and air / exhaust gas can be achieved to obtain a blended gas concentration that meets the requirements. Furthermore, by real-time monitoring and control of gas flow and blended gas concentration, the blended gas concentration can be automatically adjusted under frequent changes in low-concentration gas conditions to ensure that it does not exceed the safe range. In addition, the use of multiple blended gas concentration measuring sensors can improve the accuracy and reliability of the measurement. Such a gas mixing control system can improve the efficiency and safety of gas-regenerative oxidation wellbore antifreeze process, which meets the development requirements of energy conservation, emission reduction and carbon peaking / carbon neutrality.

[0009] Optionally, the response time of a single mixed gas concentration measuring sensor is less than 1 second. This allows the system to detect changes in gas concentration more promptly and to adjust and control it more quickly. This improves the system's sensitivity and response speed to meet the requirements of frequent changes in low-concentration gas conditions, ensuring that the mixed gas concentration remains within a safe range.

[0010] The present invention also provides a gas mixing control method, which adopts the above-mentioned gas mixing control system for gas regenerative oxidation wellbore antifreeze, and includes the following steps:

[0011] S1. Set the target value for the concentration of mixed gas, and based on this target value, set a normal range for the concentration of mixed gas to meet the set requirements;

[0012] S2. The average value of multiple sets of mixed gas concentration values ​​from each mixed gas concentration measuring sensor within the actual measurement time is taken as the control concentration value used by the controller; and the controller is used to set the upper limit alarm value, interlock value and lower limit alarm value of the control concentration value.

[0013] S3. If the concentration value used for control continues to exceed the upper limit of the normal range within a certain high-level set time, the controller will automatically reduce the gas flow regulating valve by a large proportion based on the existing opening and maintain it.

[0014] S4. If the concentration value used for control exceeds the upper limit of the normal range multiple times within a certain adjustment cycle, but does not continuously exceed the high-level set time, the controller will automatically reduce the gas flow regulating valve by a small percentage based on the existing opening and maintain it.

[0015] S5. After the gas flow regulating valve is closed, the judgment conditions of S3 and S4 are still executed. If they are triggered again, the gas concentration regulating valve will continue to be closed; if they are not triggered, the subsequent actions will be executed.

[0016] S6. If the concentration value used for control remains below the lower limit of the normal range for a certain low-level set time, the controller will automatically open the gas flow regulating valve at the first low amplitude ratio based on the existing opening degree every first scheduling cycle.

[0017] S7. If the concentration value used for control is lower than the lower limit of the normal range multiple times within a certain adjustment cycle, but does not continuously exceed the low-level set time, the controller will automatically open the gas flow regulating valve continuously at the second low amplitude ratio based on the existing opening degree every second scheduling cycle.

[0018] S8. Always execute the judgments on S3-S7, and automatically execute the corresponding gas flow regulating valve action once triggered;

[0019] S9. If the concentration value used for control exceeds the upper or lower alarm value, an alarm will be issued and the above automatic control will still be executed; if the concentration value used for control exceeds the interlock value, the corresponding interlock protection action will be executed.

[0020] This control method continuously monitors the concentration of mixed gas, sets the target value and normal range for the mixed gas concentration, sets alarm values ​​and interlock values ​​for the controller, and automatically adjusts and controls according to the set parameters to ensure that the concentration of mixed gas is within a safe range.

[0021] Preferably, in S1, if the set operating target value is 1.2%, the operating range is 1.17%-1.26%. In the gas blending control system, the controller compares the measured blended gas concentration with the set operating target value and makes judgments and adjustments based on the set normal range. If the blended gas concentration exceeds the upper limit of the operating range (1.26%), the controller will perform corresponding actions, such as adjusting the gas flow regulating valve to reduce the inflow of low-concentration gas to bring the concentration back to the normal range. Similarly, if the blended gas concentration is lower than the lower limit of the operating range (1.17%), the controller will also take corresponding measures to increase the inflow of low-concentration gas to restore the concentration to the normal range. In this way, by setting the operating target value and operating range, the gas blending control system can achieve automatic adjustment and control of the blended gas concentration to ensure that it operates within the set range. This will help improve the efficiency and safety of the gas regenerative oxidation wellbore antifreeze process.

[0022] Preferably, in S2, the measured time ranges from 5 to 10 seconds; the upper alarm value, lower alarm value, and interlock value for the control concentration are 1.3%, 0.4%, and 1.6%, respectively. In the gas blending control system, the measured time refers to the time averaging of the measured values ​​within that time period to prevent instantaneous fluctuations in the measured values ​​from causing malfunctions in the control system. According to the settings, the measured values ​​within the previous 5-10 seconds are averaged over time as the control concentration value. The upper alarm value for the control concentration is set to 1.3%, meaning that the system will trigger an alarm when the blended gas concentration exceeds 1.3%. The lower alarm value is set to 0.4%, meaning that the system will trigger an alarm when the blended gas concentration is below 0.4%. The interlock value is set to 1.6%, meaning that the system will execute interlock protection actions, such as shutting down gas blending, when the blended gas concentration exceeds 1.6%. By setting alarm and interlock values ​​for the measured time and control concentration, the gas blending control system can monitor the blended gas concentration in real time and implement alarm and protection measures based on the set parameters. This helps ensure that the blended gas concentration is within a safe range and promptly issues warning signals or executes corresponding interlock protection actions.

[0023] Preferably, in S3, the high-level setting time ranges from 2 to 4 seconds, and the large-amplitude ratio ranges from 45% to 70% of the current valve opening. The high-level setting time refers to the set time during which the control concentration value exceeds the upper limit of the normal range. According to the setting, when the control concentration value continuously exceeds the upper limit of the normal range for 2-4 seconds, the system will execute a large-amplitude adjustment. The large-amplitude ratio refers to the adjustment range of the gas flow regulating valve opening. Thus, based on the time the control concentration value exceeds the upper limit of the normal range and the large-amplitude ratio range, the system will reduce the gas inflow by 45%-70% of the current valve opening to adjust the mixed gas concentration back to the normal range, i.e., significantly reduce the low-concentration gas flow rate to quickly reduce the mixed concentration and prevent system shutdown due to the mixed gas concentration exceeding the interlock value. By setting the high-level setting time and the large-amplitude ratio, the gas mixing control system can promptly take a large-amplitude adjustment action to control the concentration when the mixed gas concentration exceeds the upper limit of the normal range. This helps ensure that the concentration of mixed gas is within the set range and maintains the stable operation of the system.

[0024] Preferably, in S4, the adjustment period ranges from 8 to 15 seconds, and the small amplitude ratio ranges from 20% to 45% of the current valve opening. The adjustment period refers to the duration during which the control concentration value repeatedly exceeds the upper limit of the normal range but does not continuously exceed the high-level set time within a certain adjustment period. According to the setting, when the control concentration value repeatedly exceeds the upper limit of the normal range within an 8-15 second adjustment period but does not continuously exceed the high-level set time, the system will perform a small amplitude adjustment. The small amplitude ratio refers to the adjustment range of the gas flow regulating valve opening. Thus, the system will reduce the gas inflow by 20%-45% of the current valve opening based on the number of times the control concentration value exceeds the upper limit of the normal range and the small amplitude ratio range, thereby adjusting the mixed gas concentration back to the normal range. By setting the adjustment period and the small amplitude ratio, the gas mixing control system can gradually adjust the gas inflow when the mixed gas concentration repeatedly exceeds the upper limit of the normal range but does not continuously exceed the high-level set time, so that the mixed gas concentration returns to the normal range. This helps maintain stable system operation and controllable concentration of mixed gas.

[0025] Preferably, in S6, the low-level setting time ranges from 16 to 25 seconds, the first scheduling cycle ranges from 6 to 10 seconds, and the first low-amplitude ratio ranges from 3% to 5% of the current valve opening. The low-level setting time refers to the set time during which the control concentration value remains below the lower limit of the normal range. According to the settings, when the set time during which the control concentration value remains below the lower limit of the normal range is within 16-25 seconds, the system will execute the first low-amplitude ratio adjustment action every first scheduling cycle. The first scheduling cycle refers to the duration of the first low-amplitude ratio adjustment action. According to the settings, the system will execute the first low-amplitude ratio adjustment action every 6-10 seconds. The first low-amplitude ratio refers to the adjustment range of the gas flow regulating valve opening to gradually increase the mixed gas concentration. Thus, based on the set time during which the control concentration value remains below the lower limit of the normal range, the first scheduling cycle, and the value range of the first low-amplitude ratio, the system will gradually increase the gas inflow at a ratio of 3% to 5% of the current valve opening to adjust the mixed gas concentration back to the normal range. By setting a low-level set time, a first scheduling cycle, and a first low-amplitude ratio, the gas blending control system can gradually adjust the gas inflow when the blended gas concentration remains below the lower limit of the normal range, thereby bringing the blended gas concentration back within the normal range. This helps maintain the stable operation of the system and the controllability of the blended gas concentration.

[0026] Preferably, in S7, the adjustment period ranges from 26 to 35 seconds, the second scheduling period ranges from 2 to 5 seconds, and the second low amplitude ratio ranges from 1% to 2% of the current valve opening. The adjustment period refers to the set time during which the control concentration value remains below the lower limit of the normal range. According to the setting, when the set time during which the control concentration value remains below the lower limit of the normal range is within 26-35 seconds, the system will execute the second low amplitude ratio adjustment action every second scheduling period. The second scheduling period refers to the duration of the second low amplitude ratio adjustment action. According to the setting, the system will execute the second low amplitude ratio adjustment action every 2-5 seconds. The second low amplitude ratio refers to the adjustment range of the gas flow regulating valve opening to gradually increase the mixed gas concentration. Thus, the system will gradually increase the gas inflow at a ratio of 1% to 2% of the current valve opening, based on the set time during which the control concentration value remains below the lower limit of the normal range, the second scheduling period, and the value range of the second low amplitude ratio, to adjust the mixed gas concentration back to the normal range. By setting an adjustment cycle, a second scheduling cycle, and a second low amplitude ratio, the gas blending control system can gradually adjust the gas inflow when the blended gas concentration remains below the lower limit of the normal range, thus bringing the blended gas concentration back within the normal range. This helps maintain the stable operation of the system and the controllability of the blended gas concentration.

[0027] The beneficial effects of this invention are: the control system and method can respond promptly to situations where the concentration of mixed gas exceeds the alarm value, and by continuously adjusting the opening of the gas flow regulating valve at a certain frequency, the concentration of mixed gas can be adjusted to the set operating target value, avoiding overshoot or untimely response, and ultimately achieving a mixed gas concentration control effect that meets the requirements of the gas regenerative oxidation wellbore antifreeze process.

[0028] In summary, this control system and method are reliable and effective in regulating the concentration of mixed gas, and can achieve accurate control of the concentration of mixed gas to meet the needs of gas-storage oxidation wellbore antifreeze process.

[0029] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a flow chart of the gas blending control process of the present invention;

[0032] Figure 2 This is a logic diagram of the gas mixing control process of the present invention;

[0033] Explanation of reference numerals in the attached diagram: 1-Low concentration methane; 2-Air / exhaust methane; 3-Methane flow regulating valve; 4-Mixing device; 5-Mixed methane concentration measuring sensor; 6-Mixed methane; 7-Controller. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0035] like Figure 1As shown in this embodiment, a gas blending control system for antifreeze of gas-heated oxidation well shafts mainly consists of a blending device 4, a gas flow regulating valve 3, a blended gas concentration measuring sensor 5, and a controller 7. The blending device 4 is used to blend low-concentration gas 1 and air / exhaust gas 2. The gas flow regulating valve 3 is installed on the pipeline before the low-concentration gas 1 enters the blending device 4. The blended gas concentration measuring sensor 5 is installed on the pipeline after the blended gas 6 exits the blending device 4. The controller 7 is electrically connected to the gas flow regulating valve 3 and the blended gas concentration measuring sensor 5 respectively to achieve automatic electrical control of the components. At least two blended gas concentration measuring sensors 5 are used, and the response time of a single blended gas concentration measuring sensor 5 is less than 1 second. The control concentration value used by the controller 7 is obtained by taking the arithmetic mean of the measured values ​​of each blended gas concentration measuring sensor 5.

[0036] Specifically, low-concentration methane 1 and air / exhaust methane 2 enter the blending device 4 through their respective inlets, while blended methane 6 flows out of the blending device 4. A methane flow regulating valve 3 is installed on the pipeline from which low-concentration methane 1 enters the blending device 4 to regulate the flow rate of low-concentration methane 1. Three blended methane concentration measuring sensors 5 are installed sequentially on the outlet pipeline of the blending device 4. If methane concentration sensors are used, and the measurement response time of the blended methane concentration measuring sensors 5 is less than 1 second, the arithmetic mean of the measured values ​​from each blended methane concentration measuring sensor 5 is taken as the measured blended methane concentration value. That is:

[0037] C test = (C1 test + C2 test + C3 test) / 3

[0038] C-measurement: The actual measured concentration of mixed gas;

[0039] C1 measurement: The measured value of the first mixed gas concentration measuring sensor;

[0040] C2 measurement: The measured value of the second mixed gas concentration measuring sensor;

[0041] C3 measurement: The measured value of the third mixed gas concentration measuring sensor.

[0042] For example Figure 2 As shown, this method for controlling the concentration of blended gas consists of the following steps:

[0043] S1. Set the target operating value for the mixed gas, such as 1.2%, and set a normal range based on the target value. The mixed gas concentration is considered to meet the set requirements if it is within the normal range. In this case, the normal range is set to 1.17%~1.26%. At the same time, set the upper limit alarm value of the mixed gas concentration to 1.3%, the interlock value to 1.6%, and the lower limit alarm value to 0.4%.

[0044] S2. Due to the real-time changes in low-concentration methane conditions (concentration and flow rate), the mixed methane concentration also changes in real time. The average of multiple mixed methane concentration values ​​measured by each sensor within 5 seconds is used as the control concentration value (referred to as the "control concentration value") to eliminate malfunctions caused by instantaneous exceedances of the measured mixed methane concentration.

[0045] C_control = (C_test-4 + C_test-3 + C_test-2 + C_test-1 + C_test-0) / 5

[0046] C control: Current control concentration value;

[0047] C-measurement-4: The concentration of mixed gas in the first 4 seconds;

[0048] C-measurement-3: The concentration of mixed gas in the first 3 seconds;

[0049] C-measurement-2: The concentration of mixed gas in the first 2 seconds;

[0050] C-measurement-1: The concentration of mixed gas in the first 1 second;

[0051] Cmeasurement-0: The current concentration of mixed gas;

[0052] The controller is used to set the upper limit alarm value for the concentration to be controlled at 1.3%, the interlock value at 1.6%, and the lower limit alarm value at 0.4%.

[0053] S3. If the concentration value of the mixed gas exceeds the upper limit of the normal range by 1.26% for a continuous period of 2 seconds within the high-level setting time, the controller will automatically reduce the gas flow regulating valve by 50% from the existing opening and maintain it; if the gas flow regulating valve is currently open at 30%, and automatically closes to 50% after the trigger condition is met, the valve opening will be automatically adjusted to 15%.

[0054] S4. If the concentration value of the mixed gas exceeds the upper limit of the normal range of 1.26% three times within a 10-second adjustment cycle, but each exceedance does not last for the high-level set time of 2 seconds, the controller will automatically further reduce the gas flow regulating valve by a small margin of 40% from the existing opening and maintain it; if the gas flow regulating valve is currently open at 15%, and automatically closes to 40% after the trigger condition is met, the valve opening will be automatically adjusted to 9%.

[0055] S5. After the gas flow regulating valve is closed, the judgment conditions of S3 and S4 are still executed. If they are triggered again, the gas concentration regulating valve will continue to be closed; if they are not triggered, the subsequent actions will be executed.

[0056] S6. If the concentration value of the mixed gas is lower than the lower limit of the normal range of 1.17% within the low setting time of 20s, the controller will automatically open the gas flow regulating valve continuously at the first low amplitude ratio of 3% based on the existing opening degree every 6s first scheduling cycle.

[0057] S7. If the concentration value of the mixed gas used for control is lower than the lower limit of the normal range of 1.17% multiple times within a 30s adjustment cycle, but does not last for more than 20s of low setting time, the controller will automatically open the gas flow regulating valve at a second low amplitude ratio of 1% based on the existing opening degree every 2s second scheduling cycle.

[0058] S8. Always execute the judgments on S3-S7, and automatically execute the corresponding gas flow regulating valve action once triggered;

[0059] S9. If the concentration value for controlling the mixed gas exceeds the upper alarm value of 1.3% or the lower alarm value of 0.4%, an alarm will be issued and the above-mentioned automatic control will still be executed; if the concentration value for controlling the mixed gas exceeds the interlock value of 1.6%, a response interlock protection action will be executed, such as shutting down the gas mixing device, i.e., the interlock protection action has the highest priority.

[0060] In this embodiment, the first scheduling period and the second scheduling period, as well as the first low amplitude ratio and the second low amplitude ratio, can have the same value.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for controlling gas mixing, characterized in that, The method employs a gas blending control system for gas storage and oxidation wellbore antifreeze. The system includes: a blending device (4) for blending low-concentration gas (1) and air / exhaust gas (2); a gas flow regulating valve (3) installed before the low-concentration gas enters the blending device; a blending gas concentration measuring sensor (5) installed after the blending gas (6) is output from the blending device; and a controller (7) for electrically connecting to the gas flow regulating valve and the blending gas concentration measuring sensor respectively. The blending gas concentration measuring sensor is configured with at least two units, and the control concentration value used by the controller is obtained by taking the arithmetic mean of the measured values ​​of each blending gas concentration measuring sensor. The response time of a single blending gas concentration measuring sensor is less than 1 second. The control method includes the following steps: S1. Set the target value for the concentration of mixed gas, and based on this target value, set a normal range for the concentration of mixed gas to meet the set requirements; S2. The average value of multiple sets of mixed gas concentration values ​​of each mixed gas concentration measuring sensor (5) within the actual measurement time is taken as the control concentration value used by the controller (7); and the controller (7) is used to set the upper limit alarm value, interlock value and lower limit alarm value of the control concentration value. S3. If the concentration value used for control continues to exceed the upper limit of the normal range within a certain high-level set time, the controller (7) will automatically open the gas flow regulating valve (3) by a large proportion based on the existing opening degree and maintain it. S4. If the concentration value used for control exceeds the upper limit of the normal range multiple times within a certain adjustment cycle, but does not continuously exceed the high-level set time, the controller (7) will automatically open the gas flow regulating valve (3) by a small margin based on the existing opening degree and maintain it. S5. After the gas flow regulating valve (3) is closed, the judgment conditions of S3 and S4 are still executed. If it continues to be triggered, the gas concentration regulating valve will continue to be closed; if it is not triggered, the subsequent actions will be executed. S6. If the concentration value used for control is continuously lower than the lower limit of the normal range within a certain low setting time, the controller (7) will automatically open the gas flow regulating valve (3) at the first low amplitude ratio on the basis of the existing opening degree every first scheduling cycle. S7. If the concentration value used for control is lower than the lower limit of the normal range multiple times within a certain adjustment cycle, but does not continue to exceed the low setting time, the controller (7) will automatically open the gas flow regulating valve (3) at the second low amplitude ratio based on the existing opening degree every second scheduling cycle. S8. Always execute the judgment of S3-S7, and once triggered, automatically execute the corresponding gas flow regulating valve (3); S9. If the concentration value used for control exceeds the upper or lower alarm value, an alarm will be issued, and the judgment and adjustment process of steps S3-S8 will still be executed; if the concentration value used for control exceeds the interlock value, the corresponding interlock protection action will be executed.

2. The gas mixing control method according to claim 1, characterized in that, In S1, if the set target value is 1.2%, the operating range is 1.17%-1.26%.

3. The gas mixing control method according to claim 1, characterized in that, In S2, the measured time ranges from 5 to 10 seconds; the upper limit alarm value, lower limit alarm value, and interlock value of the control concentration are 1.3%, 0.4%, and 1.6%, respectively.

4. The gas mixing control method according to claim 1, characterized in that, In S3, the high-level setting time ranges from 2 to 4 seconds, and the large-amplitude ratio ranges from 45% to 70% of the current valve opening.

5. The gas mixing control method according to claim 1, characterized in that, In S4, the adjustment cycle range is 8-15s, and the small amplitude ratio range is 20%-45% of the current valve opening.

6. The gas mixing control method according to claim 1, characterized in that, In S6, the low-level setting time ranges from 16 to 25 seconds, the first scheduling cycle ranges from 6 to 10 seconds, and the first low-amplitude ratio ranges from 3% to 5% of the current valve opening.

7. The gas mixing control method according to claim 1, characterized in that, In S7, the adjustment cycle ranges from 26 to 35 seconds, the second scheduling cycle ranges from 2 to 5 seconds, and the second low amplitude ratio ranges from 1% to 2% of the current valve opening.

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