Automatic Control Method of Four Butterfly Valves in Gas Mixing System

Abstract

The present invention discloses a method for automatic control of four butterfly valves in a gas mixing system, which is characterized in that the four butterfly valves, namely, the coke oven gas pressure valve, the coke oven gas flow valve, the blast furnace gas pressure valve and the blast furnace gas flow valve, which flow through the gas mixing process, are automatically controlled; the automatic control mode is: the set value of the ratio of the blast furnace gas flow rate to the coke oven gas flow rate is known, and the coke oven gas flow rate is used as the calorific value control reference to realize automatic control of the four butterfly valves, thereby ensuring the stability of the blast furnace / coke gas flow rate ratio or calorific value. The control rules of the four butterfly valves are simple, and the parameter setting is convenient. The coupling effect between the pressure regulation and the calorific value regulation or the flow regulation in the system is considered, and the stable control of the mixed gas pressure and calorific value can be realized at the same time, the ability to suppress disturbance is strong, and the actual operating condition of the system is more stable.

Description

Technical Field

[0001] The invention relates to a coal gas mixing and pressurizing technology for a metallurgical enterprise, and in particular to an automatic control method for a coal gas mixing process. Background Art

[0002] The mixed gas pressurization process is to mix two or more monomer gases in a certain proportion, boost the pressure to the specified pressure through a pressurizing unit, and then send it to the subsequent heating furnace or other gas users.

[0003] The current conventional mixed gas pressure station structure is as follows: Figure 1 As shown in the figure, blast furnace gas enters the mixing pipeline through butterfly blast furnace gas pressure valve and butterfly flow valve; coke oven gas enters the mixing pipeline through butterfly coke oven gas pressure valve and butterfly flow valve; after passing through the mixing point, the mixed gas pressure is tested, and then the pressure is increased to the specified pressure by the pressurizing unit, and then it is transported to the subsequent heating furnace or other gas users through the fan outlet main pipe. A flap valve is set in front of each pressurizing unit to adjust the main pipe pressure.

[0004] As can be seen from the above structure diagram, two butterfly valves are installed on the blast furnace pipeline and coke oven pipeline for gas, and then the ratio of the coke oven gas flow rate to the blast furnace gas flow rate is adjusted manually by adjusting the four butterfly valves to achieve the purpose of stabilizing the calorific value of the mixed gas. However, the discontinuous production process and the large pressure changes in the two gas source pipelines of high coal and coke are the practical problems faced by blast furnace gas and coke oven gas. The load fluctuation of the mixed gas is also relatively large. At the same time, there are problems such as strong electromagnetic interference and butterfly valve failure at the gas booster station. The existence of these factors makes the manual adjustment of the gas ratio on site, although it has a certain guarantee effect on the calorific value stability of the mixed gas, the calorific value of the mixed gas still fluctuates greatly in general, and the adjustment speed is also relatively slow, which cannot meet the production process goals of the gas user for the calorific value and pressure stability of the mixed gas, and also causes the waste of blast furnace gas, thereby causing the underutilization of energy and economic losses. In addition, if the gas ratio is adjusted manually, it will greatly increase the labor intensity and work pressure of the workers.

[0005] At the same time, the mixed gas pressure is also susceptible to the subsequent operation of the compressor unit and the opening of the butterfly valves in front of each compressor. The mixed gas pressure and the fan main pipe pressure, the opening of the front butterfly valve, the rear butterfly valve and the front flap of the machine will all affect the load of the fan in the running unit, thereby affecting the fan current.

[0006] Therefore, the mixed gas pressurization process presents dynamic changes, and has complex characteristics such as nonlinearity, multivariable coupling, large lag and many uncertain parameters. It is not easy to measure the pressure and calorific value of the mixed gas after pressurization online in a timely manner, and it is difficult to establish an accurate online measurement mechanism model, which directly leads to the mixed gas pressurization system being difficult to adapt to external disturbances such as long gas change transition process and rapid changes in heating furnace load. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide an automatic control method for four butterfly valves in a gas mixing system to ensure the stability of the high / coke gas flow ratio or calorific value, and to ensure that the mixed gas pressure meets the complex requirements of external disturbances under the condition of sufficient high-coke input gas.

[0008] At the same time, the control rules of the four butterfly valves are simple and the parameter settings are convenient. The coupling effect between pressure regulation and calorific value regulation (flow regulation) in the system is taken into account. The regulation accuracy is not high, the ability to suppress disturbances is strong, and the operating conditions of the system during operation are more stable.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A method for automatically controlling four butterfly valves in a gas mixing system is characterized in that the four butterfly valves, namely, a coke oven gas pressure valve, a coke oven gas flow valve, a blast furnace gas pressure valve, and a blast furnace gas flow valve, through which the gas flows during the gas mixing process are automatically controlled; the specific steps for automatically controlling the four butterfly valves at the coking coal inlet are as follows:

[0011] Step S1: firstly, setting a set value of the ratio of blast furnace gas flow rate to coke oven gas flow rate, setting a high coal calorific value set value and a coking coal calorific value set value;

[0012] Step S2: then detecting and obtaining the actual flow rate of high coal and the actual flow rate of coking coal;

[0013] Step S3: Calculate the calorific value based on the detection results. The mixed gas calorific value calculation model is set as:

[0014] Theoretical calorific value of mixed coal gas = (actual flow of high-pressure coal * given value of high-pressure coal calorific value + actual flow of coking coal * given value of coking coal calorific value) / (actual flow of high-pressure coal + actual flow of coking coal);

[0015] Actual ratio of high coke flow rate = actual high coal flow rate / actual coking coal flow rate;

[0016] Step S4: perform relevant variable detection, and enter automatic control mode when relevant variable detection conditions are met;

[0017] The relevant variable detection conditions are: the actual ratio of high coke flow is within the set range, and the measurements of the high coal flow meter and the coke flow meter are normal;

[0018] The automatic control mode is: given a set value of the ratio of blast furnace gas flow rate to coke oven gas flow rate, the coke oven gas flow rate is used as a calorific value control reference to achieve automatic control of the four butterfly valves.

[0019] In the above technical solution, the setting range of the actual ratio of the high-focus flow in step S4 needs to meet 60:40 to 50:50.

[0020] In the above technical solution, the openings of the four butterfly valves are controlled in the order of the coke oven gas flow valve, the coke oven gas pressure valve, the blast furnace gas flow valve and the blast furnace gas pressure valve.

[0021] In the above technical solution, the opening of the coke oven gas flow valve is controlled according to the outlet main pipe pressure of the compressor fan and the opening of the front flap valve of the compressor.

[0022] In the above technical solution, the opening automatic control process of the coke oven gas flow valve is:

[0023] When the average value of the outlet main pressure setting time measurement is less than 1.2 times the lower limit of the outlet main pressure setting, and the average opening value of the front flap opening valve of the current working unit is greater than the set high average value, the coking coal flow valve opening increases by 2% within the control cycle, and the coking coal flow valve opening is automatically controlled not to exceed its own opening upper limit value;

[0024] When the average value of the outlet main pipe pressure setting time measurement is greater than 90% of the outlet main pipe pressure setting upper limit, and the average value of the opening of the front flap valve of the current working unit is less than the set low-level average value, the coking coal flow valve opening is reduced by 2% within the control cycle, and the coking coal flow valve opening is automatically controlled not to exceed its own opening lower limit.

[0025] In the above technical solution, the preferred setting time is 3-5 minutes, and 5 minutes is optimal; the preferred setting high average value is 85%, and the preferred setting low average value is 55%. The setting high average value and the setting low average value can also be changed and adjusted according to the pressure demand to be controlled.

[0026] In the above technical solution, the process of automatic control of the opening of the coke oven gas pressure valve is as follows:

[0027] Preset the target value of the pressure after the coking coal pressure valve and the upper and lower limits of the coking coal pressure;

[0028] When the average test time of the pressure setting after the coke oven gas pressure valve is greater than 90% of the upper limit of the coke coal pressure, the opening of the coke oven gas pressure valve is greater than the first setting value of the coke coal pressure, and the opening of the coke oven gas pressure valve is reduced by 3%; when the average test time of the pressure setting after the coke oven gas pressure valve is less than 1.2 times the lower limit of the coke coal pressure, the opening of the coke oven gas pressure valve is less than the first setting value of the coke coal pressure, and the opening of the coke oven gas pressure valve is increased by 3%;

[0029] When the test time average of the valve back pressure setting of the coke oven gas pressure valve is greater than the valve back pressure target value of the coking coal pressure valve + 0.5Kpa, and less than 90% of the upper limit of the coking coal pressure, the coke oven gas pressure valve opening is greater than the second setting value of the coking coal pressure, and the coke oven gas pressure valve opening is reduced by 2% within the control period;

[0030] When the average value of the test time of the valve back pressure setting of the coke oven gas pressure valve is less than the valve back pressure target value of the coking coal pressure valve -0.5Kpa, and greater than 1.2 times the lower limit of the coking coal pressure, the coke oven gas pressure valve opening is less than the third setting value of the coking coal pressure, and the coke oven gas pressure valve opening increases by 2% within the control period;

[0031] The first set value of coking coal pressure, the second set value of coking coal pressure, and the third set value of coking coal pressure are all within the upper and lower limits of coking coal pressure.

[0032] Preferably, the first setting value of the coking coal pressure is 63, the second setting value of the coking coal pressure is 62, and the third setting value of the coking coal pressure is 90; the specific setting value can be adjusted according to the control conditions; the set test time is also preferably 3-5 minutes, and the control period can be adjusted.

[0033] In the above technical solution, the process of automatic control of the blast furnace gas flow valve opening is:

[0034] Firstly, the high coal flow set value is calculated, and the high coal flow set value is taken as the control target. The deviation of the actual high coal and coking coal flow ratio within the deviation range is used as the basis for setting the control target. The deviation between the actual high coal flow and the high coal flow set value is used as feedback to realize the PID control of the high coal flow regulating valve. When the deviation is exceeded, an alarm is issued to give a high coal flow over-limit prompt. When the deviation exceeds the deviation setting amplitude, the automatic control is released after the delay setting time.

[0035] In the above technical solution, the high coal flow rate setting value = the actual coking coal flow rate * (the setting value of the ratio of blast furnace gas flow rate to coke oven gas flow rate).

[0036] In the above technical solution, based on the actual flow rate of high coal, the actual flow rate of coking coal, and the set value of the ratio of blast furnace gas flow rate to coke oven gas flow rate, the deviation of the flow rate ratio of high coal and coking coal is calculated as follows:

[0037] The deviation of the flow ratio of high coal and coking coal = (actual flow ratio of high coke - the set value of the ratio of blast furnace gas flow and coke oven gas flow) * 100% = ((actual flow of high coal / actual flow of coking coal) - the set value of the ratio of blast furnace gas flow and coke oven gas flow) * 100%.

[0038] In the above technical solution, the deviation range of the high coal and coking coal flow ratio deviation is within ±3%.

[0039] In the above technical solution, if the deviation exceeds ±8%, the automatic control mode will be released after a delay of 30 seconds.

[0040] When the high coal flow valve opening is greater than the set value, the blast furnace gas pressure valve opening is less than the upper limit setting value, the blast furnace gas pressure valve opening increases by 2% within the control cycle, and the blast furnace gas pressure valve opening does not exceed the upper limit setting value;

[0041] When the high coal flow valve is less than the lower limit setting value, the blast furnace gas pressure valve is greater than the lower limit setting value, the blast furnace gas pressure valve opening decreases by 2% within the control cycle, and the blast furnace gas pressure valve opening is not less than the lower limit setting value.

[0042] Therefore, the present invention decomposes the positions and characteristics of the four butterfly valves in the gas mixing process and realizes classified control based on flow and pressure: through the personalized control rules of the four butterfly valves at the high coal and coking coal inlets, automatic control of each flow valve and each pressure valve in the four butterfly valves is realized through PLC control.

[0043] Based on the requirements of mixed pressure control, the opening control strategy of coking coal pressure valve and coking coal flow valve is given; based on the requirements of proportion control, the opening control strategy of high coal pressure valve and high coal flow valve is given.

[0044] In the actual programming process, those skilled in the art can combine and simplify the control rules of each butterfly valve according to the actual regulation process.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] The present invention overcomes the problems that the mixed gas pressurization process presents dynamic changes, has complex characteristics such as nonlinearity, multivariable coupling, large hysteresis and numerous uncertain parameters, is not easy to timely measure the pressure and calorific value of the mixed gas after pressurization online, and is difficult to establish an accurate online measurement mechanism model, which directly leads to the mixed gas pressurization system being difficult to adapt to defects such as long gas change transition process and fast heating furnace load change. Through the personalized control rules of the four butterfly valves at the high coal and coking coal inlets, automatic control of each flow valve and pressure valve in the four butterfly valves is realized through PLC control, thereby ensuring the stability of the high / coking coal gas flow ratio or calorific value, and ensuring that the pressure of the mixed gas meets the requirements under the condition of sufficient high-coke input gas.

[0047] Based on the requirements of mixed pressure control, the opening control strategy of coking coal pressure valve and coking coal flow valve is given; based on the requirements of proportion control, the opening control strategy of high coal pressure valve and high coal flow valve is given.

[0048] The present invention adopts the setting value of the ratio of blast furnace gas flow rate to coke oven gas flow rate as a known condition, takes the coke oven gas flow rate as the calorific value control reference, realizes automatic control of four butterfly valves, thereby ensuring the stability of the blast furnace gas / coke gas flow rate ratio or calorific value. Through the intelligent control rule of pressure and flow matching, the stability of the blast furnace gas / coke gas flow rate ratio or calorific value is ensured, and the influence of external disturbance on the mixed gas pressure is reduced under the condition of sufficient blast furnace gas input.

[0049] Finally, the control rules of the four butterfly valves of the present invention are simple, the parameter setting is convenient, and the coupling effect between pressure regulation and calorific value regulation (flow regulation) in the system is taken into consideration. The stable control of the mixed gas pressure and calorific value can be achieved at the same time, the ability to suppress disturbances is strong, and the actual operating conditions of the system are more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0051] Figure 1 It is a schematic diagram of the structure of the mixed gas pressure station on which the control method of the present invention is based. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0053] Embodiment 1: The automatic control method of four butterfly valves in the gas mixing system implemented according to the present invention includes automatically controlling the four butterfly valves, namely, the coke oven gas pressure valve, the coke oven gas flow valve, the blast furnace gas pressure valve and the blast furnace gas flow valve, through which the gas mixing process passes.

[0054] The control equipment is four butterfly valves; Figure 1 Medium and blast furnace gas pressure valve, blast furnace gas flow valve, coke oven gas pressure valve, blast furnace gas flow valve.

[0055] The control parameters are the opening of the four butterfly valves, the set value of the high coal gas flow / coking coal gas flow ratio (i.e., high coke flow ratio), the high coal calorific value set value, and the coking coal calorific value set value.

[0056] The actual values ​​of high coal flow and coking coal flow are obtained through detection; the calorific value is calculated based on the detection results.

[0057] For calorific value calculation, it is necessary to input the set value of high coal / coking coal gas flow ratio, high coal calorific value given, and coking coal calorific value given in the operation interface.

[0058] The mixed gas calorific value calculation model is set as:

[0059] Theoretical calorific value of mixed coal gas = (actual value of high coal flow rate * given value of high coal calorific value + actual value of coking coal flow rate * given value of coking coal calorific value) / (actual value of high coal flow rate + actual value of coking coal flow rate);

[0060] Actual ratio of high coke flow rate = actual value of high coal flow rate / actual value of coking coal flow rate;

[0061] The four butterfly valves can be set to either manual or automatic control mode. If the regulating valve is set to manual mode, the opening of the regulating valve is set through the operation interface.

[0062] Before setting the high coal flow regulating valve to automatic control mode, relevant variable detection must be carried out:

[0063] Whether the ratio of high coal flow rate to coking coal flow rate is within a reasonable range (such as 60:40~50:50); whether the measurement of high coal and coking coal flow meters is normal.

[0064] If the automatic control conditions are met, the automatic control mode is set, and the control program is completed by the four butterfly valve control module in the PLC. If it is abnormal, the host computer will give a prompt, indicating that the automatic control conditions are not met.

[0065] The basic idea of ​​automatic control of four butterfly valves is: given the set value of the high coal gas flow / coking coal gas flow ratio, the coke oven pressure valve is used as the mixed pressure setting benchmark, and the coke oven flow valve is used as the calorific value setting benchmark to achieve automatic control of the four butterfly valves.

[0066] (1) Coke oven gas flow valve automatic control

[0067] The opening of the coking coal flow valve is controlled according to the outlet main pipe pressure and the opening of the front flap valve of the machine;

[0068] When the 5-minute measured average value of the outlet main pressure is less than 1.2 times the lower limit of the outlet main pressure setting, and the average opening of the front flap opening valve of the current working unit is greater than 85, the coking coal flow valve opening increases by 2 degrees, and the coking coal flow valve opening is automatically controlled not to exceed the upper limit of 90;

[0069] When the 5-minute measured average value of the outlet main pipe pressure is greater than 90% of the set upper limit of the outlet main pipe pressure, and the average opening of the front flap valve of the current working unit is less than 55, the opening of the coking coal flow valve is reduced by 2 degrees within the control cycle, and the opening of the coking coal flow valve is automatically controlled not to exceed its own opening lower limit of 60.

[0070] (2) Automatic control of coke oven gas pressure valve

[0071] Set the target value and upper and lower limits of coking coal pressure on the operation interface;

[0072] When the 5-minute average pressure behind the coke oven gas pressure valve is greater than 90% of the upper limit of the coking coal pressure, the coke oven gas pressure valve opening is greater than 63, and the coke oven gas pressure valve opening is reduced by 3; when the 5-minute average pressure behind the coke oven gas pressure valve is less than 1.2 times the lower limit of the coking coal pressure, the coke oven gas pressure valve opening is less than 90, and the coke oven gas pressure valve opening is increased by 3;

[0073] When the 5-minute average of the pressure behind the coke oven gas pressure valve is greater than the target pressure behind the coke coal pressure valve + 0.5Kpa, and less than 90% of the upper limit of the coke coal pressure, the opening of the coke oven gas pressure valve is greater than 62, and the opening of the coke oven gas pressure valve is reduced by 2 within the control period;

[0074] When the 5-minute average pressure behind the coke oven gas pressure valve is less than the target value of the pressure behind the coking coal pressure valve -0.5Kpa, and greater than 1.2 times the lower limit of the coking coal pressure, the opening of the coke oven gas pressure valve is less than 90, and the opening of the coke oven gas pressure valve increases by 2 degrees within the control cycle.

[0075] (3) Automatic control of blast furnace gas flow valve

[0076] The high coal flow valve adopts PID control. The adjustment of the high coal flow valve needs to ensure that the actual flow ratio deviation of high coal and coking coal is within ±3%. The control is based on the actual flow of coking coal or the actual flow value of the coke oven flow valve as the control target setting benchmark.

[0077] Calculate the high coal flow setpoint:

[0078] High coal flow setting value = actual value of coking coal flow * (setting value of the ratio of blast furnace gas flow to coke oven gas flow);

[0079] The deviation of the flow ratio of high coal and coking coal = (actual flow ratio of high coke - (the set value of the ratio of blast furnace gas flow and coke oven gas flow))*100% = ((actual flow of high coal / actual flow of coking coal) - (the set value of the ratio of blast furnace gas flow and coke oven gas flow))*100%.

[0080] The high coal flow setting value is used as the control target, and the deviation between the high coal actual flow and the high coal flow setting value is used as feedback to realize the PID control of the high coal flow regulating valve opening. In this process, ensure that the deviation of the high coal coking coal actual flow ratio is within ±3%. If the deviation exceeds the allowable range, an alarm will be issued, and a high coal flow limit overlimit prompt will be given. When the deviation exceeds ±8%, the automatic control mode will be released after a delay of 30 seconds.

[0081] (4) Automatic control of blast furnace gas pressure valve opening

[0082] When the high coal flow valve opening is greater than 75, the blast furnace gas pressure valve opening is less than 65, the blast furnace gas pressure valve opening increases by 2 degrees within the control cycle, and the blast furnace gas pressure valve opening does not exceed 75;

[0083] When the high coal flow valve is less than 15 and the blast furnace gas pressure valve is greater than 25, the blast furnace gas pressure valve opening decreases by 2 degrees within the control cycle, and the blast furnace gas pressure valve opening is not less than 15.

[0084] Through the automatic control of the above four butterfly valves, the safe and stable operation of the gas mixing system can be guaranteed, and the less-manned and intelligent control of the gas mixing and pressurizing system can be realized. At present, most gas mixing and pressurizing stations use manual control or control the four butterfly valves based on complex decoupling calculations.

[0085] Compared with this gas mixing control method, the above-mentioned four butterfly valve controllers of the present invention are simple in design and convenient in parameter setting. They not only take into account the variable coupling effect brought about by the variable matching between the regulated quantity and the regulating quantity, but also take into account the coupling effect between the pressure regulation and calorific value regulation (flow regulation) in the system. It can simultaneously achieve stable control of the mixed gas pressure and calorific value, has a strong ability to suppress disturbances, and the actual operating conditions of the system are more stable.

[0086] The booster unit after the gas mixing node includes several boosters, and the components of each booster include at least: ventilator, front electric valve, flap regulating valve, high-voltage motor, lubricating oil system, and rear electric valve. As an auxiliary control method, an automatic control method for main pipe pressure is set: according to the current, opening and fan main pipe outlet pressure detection data of the booster unit, the opening of the front flap valve of the booster unit is intelligently controlled, and the main pipe pressure is adjusted by the flap valve opening to stabilize near the main pipe pressure setting value to ensure the stability of the fan outlet main pipe pressure.

[0087] The main pipe pressure automatic control step is to adjust the flap opening according to different flap opening adjustment modes under single unit operation mode, dual unit operation mode and multi-unit operation mode;

[0088] Under the single unit operation mode, according to the deviation E(%) between the actual value of the main pipe pressure and the set value of the main pipe pressure, the actual value of the flap opening Φ, and the motor current I, the flap valve opening change is automatically controlled based on the fuzzy control rules;

[0089] Under the dual-unit operation mode, according to the deviation E(%) between the actual value of the main pipe pressure and the set value, the motor current deviation IA-IB between the two units, the motor current IA of unit A, the actual flap opening value ΦA of unit A, the motor current IB of unit B, and the actual flap opening value ΦB of unit B, the automatic control of the flap valve opening change is realized based on the fuzzy control rules.

[0090] In multi-unit operation mode, the two units with the highest and lowest currents are selected, and then controlled according to the control rules of the two units.

[0091] In the above-mentioned main pipe pressure automatic control mode, under the single unit operation mode, the upper and lower limit percentages of the flap valve opening are set to 90 and 50 respectively, and the motor current is given priority to not exceeding the specified upper and lower limits when adjusting the valve opening; the increase or decrease in the opening within the control cycle does not exceed 5%; the deviation E percentage between the actual value of the main pipe pressure and the set value of the main pipe pressure varies between -0.2 and 0.2 and at both ends, the actual value Φ of the flap opening varies between 50 and 90 and at both ends, and the motor current I varies between 32 and 60 and at both ends.

[0092] In the above-mentioned main pipe pressure automatic control mode, under the dual unit operation mode, the upper and lower limit percentages of the flap valve opening of the two units are set to 90 and 50, and the motor current is adjusted to not exceed the specified upper and lower limits; the currents of the two units are balanced as much as possible while meeting the pressure and current requirements; the increase or decrease of the flap valve opening within the control cycle does not exceed 5%; the deviation E of the actual value of the main pipe pressure from the set value of the main pipe pressure is between -0.2 and 0.2 and varies at both ends; the unit motor current deviation IA-IB varies between -2 and 2 and varies at both ends; the motor currents IA and IB are both between 32 and 60 and vary at both ends; the actual flap opening Φ varies between 50 and 90 and varies at both ends.

[0093] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for automatically controlling four butterfly valves in a gas mixing system, characterized in that The four butterfly valves, namely, the coke oven gas pressure valve, the coke oven gas flow valve, the blast furnace gas pressure valve and the blast furnace gas flow valve, through which the gas flows during the gas mixing process are automatically controlled; the specific steps for automatically controlling the four butterfly valves are as follows: Step S1: firstly, setting a set value of the ratio of blast furnace gas flow rate to coke oven gas flow rate, a high coal calorific value given value and a coking coal calorific value given value; Step S2: then detecting and obtaining the actual flow rate of high coal and the actual flow rate of coking coal; Step S3: Calculate the calorific value based on the detection results. The mixed gas calorific value calculation model is set as: Theoretical calorific value of mixed coal gas = (actual flow rate of high-pressure coal × given value of high-pressure coal calorific value + actual flow rate of coking coal × given value of coking coal calorific value) / (actual flow rate of high-pressure coal + actual flow rate of coking coal); Actual ratio of high coke flow = actual high coal flow / actual coking coal flow; Step S4: Perform relevant variable detection, and enter automatic control mode when relevant variable detection conditions are met; The relevant variable detection conditions are: the actual ratio of high coke flow is within the set range, and the measurements of the high coal flow meter and the coke flow meter are normal; The automatic control mode is: given a set value of the ratio of blast furnace gas flow rate to coke oven gas flow rate, the coke oven gas flow rate is used as the calorific value control benchmark to achieve automatic control of the four butterfly valves; the openings of the four butterfly valves are controlled in the order of the coke oven gas flow valve, the coke oven gas pressure valve, the blast furnace gas flow valve, and the blast furnace gas pressure valve; the opening of the coke oven gas flow valve is controlled according to the pressure of the outlet main pipe of the compressor fan and the opening of the front flap valve of the compressor; The process of automatic control of the opening of the coke oven gas pressure valve is as follows: Pre-set the target pressure value after the coking coal pressure valve, and the upper and lower limits of the coking coal pressure; When the average pressure behind the coke oven gas pressure valve within the set test time is greater than 90% of the upper limit of the coke coal pressure, the coke oven gas pressure valve opening is greater than the first set value of the coke coal pressure, and the coke oven gas pressure valve opening is reduced by 3%; when the average pressure behind the coke oven gas pressure valve within the set test time is less than 1.2 times the lower limit of the coke coal pressure, the coke oven gas pressure valve opening is less than the first set value of the coke coal pressure, and the coke oven gas pressure valve opening is increased by 3%; When the average pressure behind the coke oven gas pressure valve within the set test time is greater than the target pressure behind the coke coal pressure valve + 0.5Kpa, and less than 90% of the upper limit of the coke coal pressure, the opening of the coke oven gas pressure valve is greater than the second set value of the coke coal pressure, and the opening of the coke oven gas pressure valve is reduced by 2% within the control period; When the average pressure behind the coke oven gas pressure valve within the set test time is less than the target value of the coke coal pressure valve pressure -0.5Kpa, and greater than 1.2 times the lower limit of the coke coal pressure, the coke oven gas pressure valve opening is less than the third set value of the coke coal pressure, and the coke oven gas pressure valve opening increases by 2% within the control period; The first set value of coking coal pressure, the second set value of coking coal pressure and the third set value of coking coal pressure are all within the upper and lower limits of coking coal pressure; The process of automatic control of the opening of the blast furnace gas pressure valve is as follows: When the high coal flow valve opening is greater than the set value, the blast furnace gas pressure valve opening is less than the upper limit setting value, the blast furnace gas pressure valve opening increases by 2% within the control cycle, and the blast furnace gas pressure valve opening does not exceed the upper limit setting value; When the high coal flow valve is less than the lower limit setting value, the blast furnace gas pressure valve is greater than the lower limit setting value, the blast furnace gas pressure valve opening decreases by 2% within the control cycle, and the blast furnace gas pressure valve opening is not less than the lower limit setting value.

2. The automatic control method of four butterfly valves in a gas mixing system according to claim 1, characterized in that The setting range of the actual ratio of the high focal flow in step S4 needs to meet 60:40 to 50:

50.

3. The automatic control method of four butterfly valves in a gas mixing system according to claim 1 or 2, characterized in that The opening automatic control process of the coke oven gas flow valve is: When the average value of the outlet main pipe pressure measured within the set time is less than 1.2 times the lower limit of the outlet main pipe pressure setting, and the average opening value of the front flap opening valve of the current working unit is greater than the set high-level average value, the coking coal flow valve opening increases by 2% within the control cycle, and the coking coal flow valve opening is automatically controlled not to exceed its own opening upper limit value; When the average value of the outlet main pipe pressure measured within the set time is greater than 90% of the set upper limit of the outlet main pipe pressure, and the average value of the opening of the front flap valve of the current working unit is less than the set low-level average value, the opening of the coking coal flow valve decreases by 2% within the control cycle, and the opening of the coking coal flow valve is automatically controlled not to exceed its own lower limit of opening.

4. The automatic control method of four butterfly valves in a gas mixing system according to claim 1 or 2, characterized in that The process of automatic control of blast furnace gas flow valve opening is: Firstly, the high coal flow set value is calculated; then, the high coal flow set value is used as the control target, the actual high coal and coking coal flow ratio deviation within the deviation range is used as the basis for setting the control target, and the deviation between the actual high coal flow and the high coal flow set value is used as feedback to realize the PID control of the high coal flow regulating valve; when the deviation is exceeded, an alarm is issued and a high coal flow over-limit prompt is given; when the deviation exceeds the deviation setting amplitude, the automatic control is released after the delay setting time.

5. The automatic control method of four butterfly valves in a gas mixing system according to claim 1 or 2, characterized in that High coal flow set value = actual coking coal flow × set value of the ratio of blast furnace gas flow to coke oven gas flow.

6. The automatic control method of four butterfly valves in a gas mixing system according to claim 1 or 2, characterized in that The high-temperature coal and coking coal flow ratio deviation = ((actual high-temperature coal flow / actual coking coal flow) - the set value of the blast furnace gas flow rate to coke oven gas flow rate ratio) × 100%.

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