Monitoring and control method of air flow rate of large blast furnace blower unit

Abstract

The present invention discloses a method for monitoring and controlling the air flow rate of a large-scale blast furnace blower unit, comprising a blower unit, an air supply duct, a blast furnace, a check valve, a flow monitor and an air supply valve. Two air supply temperature monitoring points A and B, two air supply pressure monitoring points C and D, and two air supply differential pressure monitoring points E and F arranged on the flow monitor are arranged on the air supply duct between the check valve and the flow monitor. The present invention is provided with a dual-loop measurement, wherein the measurement signal of one loop is used for air supply flow rate monitoring and constant air volume automatic control operation of the blower unit, and the measurement signal of the other loop is used for air supply flow rate monitoring and signal comparison with the control system. By setting a comparison difference control range, it is ensured that the instantaneous fluctuation amplitude of the air supply flow rate does not exceed 4% of the actual flow rate, which can effectively avoid the occurrence of large fluctuations in the blast furnace air supply and serious impact on production due to various abnormalities or failures of the air supply flow rate measurement circuit, thereby ensuring the stable operation of the blower unit and safe production of the blast furnace.

Description

Technical Field

[0001] The present invention belongs to the technical field of the metallurgical industry, and specifically relates to a method for monitoring and controlling the air flow rate of a large blast furnace blower unit. Background Art

[0002] The blower unit is the power heart of the blast furnace; large blast furnace blower units usually adopt constant air volume automatic control operation. According to the needs of the blast furnace, the blower unit control unit sets the air flow set value. The air flow monitoring system monitors the air flow related parameter signals in real time and transmits them to the control unit. The control unit calculates the actual value of the air flow and compares it with the set value, and adjusts the blower unit stator blade angle in real time to make the actual value consistent with the set value, thereby achieving stable air supply production in the blast furnace.

[0003] The blower unit air flow monitoring system consists of three measuring elements, namely, air temperature, air pressure and air differential pressure, which are arranged on the air supply duct, as well as a transmitter and a signal transmission line. The three measurement signals are transmitted to the control unit together, and the actual value of the air flow can be obtained through calculation and processing. The air differential pressure is the basic signal of the air flow, and the air temperature and air pressure are the compensation signals of the air flow. The control unit compares the actual value of the air flow with the set value and realizes constant air volume operation control. For the blower unit with constant air volume automatic control operation, the safety and reliability of the air flow monitoring and control system is very critical. Any abnormality or failure in the signal measurement circuit will directly lead to a sudden change in the actual value of the air flow. Once the actual value deviates from the set value, the angle of the static blade of the blower unit will be automatically adjusted (this is a malfunction caused by an abnormality or failure in the measurement circuit). The greater the deviation between the actual value and the set value, The greater the adjustment range of the stator blade angle, the greater the fluctuation of the blast furnace air supply and serious impact on production; if the actual value of the monitored air supply flow suddenly decreases, the stator blade angle will automatically increase, and the blast furnace air volume and pressure will suddenly increase. The greater the decrease in the actual value of the air supply flow, the greater the increase in the blast furnace air volume and pressure, which not only affects the stability of the blast furnace air supply, but also endangers the safe production of the blast furnace; if the actual value of the monitored air supply flow suddenly increases, the stator blade angle will automatically decrease, and the blast furnace air volume and pressure will suddenly drop. The greater the increase in the actual value of the air supply flow, the greater the drop in the blast furnace air volume and pressure, which has a direct impact on the blast furnace air supply. If the stator blade angle is closed too much, it will also cause the blower unit operating point to deviate from the stable operating area, which can easily lead to the opening of the anti-surge valve and the blower unit entering the safe operating condition (i.e. load shedding), causing serious accidents such as blast furnace air interruption and slag filling in the tuyere.

[0004] The existing air flow monitoring and control system uses a single circuit to measure the air temperature, air pressure and air differential pressure. Due to long-term continuous use, it is common for the measurement circuit to have abnormalities or failures, such as condensation accumulation and blockage in the pressure taking pipe, failure of primary measuring elements, transmitters and other instruments, aging and breakage of the insulation of the signal transmission line, loose connections, damage caused by external influences, etc. Since the blower unit is controlled by constant air volume operation, the above abnormalities or failures will directly lead to a sudden change in the actual value of the air flow of the normally operating blower unit, resulting in malfunction of the stator blade angle, thereby affecting the blast furnace production to varying degrees. The safety and reliability of the air flow monitoring and control system is an important link to ensure the stable operation of the blower unit and the safe air supply of the blast furnace. Summary of the Invention

[0005] 1. Technical problem to be solved by the invention

[0006] The purpose of the present invention is to overcome the problem that when an abnormality or failure occurs in the existing air flow monitoring system, the actual value of the air flow of the normally operating blower group will be directly caused to change suddenly, resulting in the misoperation of the stator blade angle, thereby causing different degrees of impact on blast furnace production, and provide a large-scale blast furnace blower group air flow monitoring and control method; the present invention performs dual-loop measurement of the air supply temperature, air supply pressure, and air supply differential pressure on the air supply duct, and the measurement signal of one loop is used for the air supply flow monitoring, operation monitoring and constant air volume automatic control operation of the blower group, and the measurement signal of the other loop is used for signal comparison of the air supply flow monitoring and control system. By setting the comparison difference control range, it is ensured that the instantaneous fluctuation amplitude of the air supply flow does not exceed 4% of the actual flow. When the comparison difference exceeds the control range, the operation control mode of the blower group will be automatically switched, which can effectively avoid the occurrence of large fluctuations in the blast furnace air supply and serious impact on production due to various abnormalities or failures in the air flow measurement circuit, thereby ensuring stable operation of the blower group and safe production of the blast furnace.

[0007] 2. Technical solution

[0008] To achieve the above-mentioned object, the present invention provides a method for monitoring and controlling the air flow rate of a large blast furnace blower unit, comprising a blower unit, an air supply duct, and a blast furnace connected in sequence, wherein a check valve, a flow rate monitor, and an air supply valve are sequentially provided on the air supply duct. The control steps are as follows:

[0009] S1: Two air supply temperature monitoring points A and B, two air supply pressure monitoring points C and D, and two air supply differential pressure monitoring points E and F set on the flow monitor are set on the air supply duct between the check valve and the flow monitor;

[0010] S2: The supply air temperatures detected by supply air temperature monitoring points A and B are T1 and T2, the supply air pressures detected by supply air pressure monitoring points C and D are P1 and P2, and the supply air differential pressures detected by supply air differential pressure monitoring points E and F are ΔP1 and ΔP2;

[0011] S3: Connect the supply air temperature monitoring points A and B, the supply air pressure monitoring points C and D, and the supply air differential pressure monitoring points E and F to the control unit through transmitters and signal transmission lines to form a dual measurement loop. The dual measurement loop signals are divided into two groups, namely T1, P1, ΔP1 and T2, P2, ΔP2. Both groups of signals are transmitted to the control unit in real time. One group of signals (T1, P1, ΔP1) is used for supply air flow monitoring, operation monitoring and constant air volume automatic control operation of the blower unit, and the other group of signals (T2, P2, ΔP2) is used for supply air flow monitoring and signal comparison with the control system;

[0012] S4: Calculate the air flow rate based on the measured T1, P1, and ΔP1 values. The calculation formula is:

[0013]

[0014] Where: Q is the air flow rate, Nm 3 / min; ΔP is the air supply differential pressure, kPa; P is the air supply pressure, MPa; T is the air supply temperature, °C;

[0015] S5: In actual production, the allowable variation values ​​of the three signal parameters of supply air temperature, supply air pressure, and supply air differential pressure are designed based on the fact that the instantaneous decrease or increase of the supply air flow Q does not exceed 4%, and the control range of the comparison difference of the dual-loop measurement signal is set;

[0016] S6: Setting the comparison difference rate calculation formula and set value of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure through the control unit. The comparison difference rate calculation formulas are: |(T1-T2) / Tt|, |(P1-P2) / Pp|, |(ΔP1-ΔP2) / ΔPp|;

[0017] Among them, Tt, Pp and ΔPp are the maximum range values ​​of supply air temperature, supply air pressure and supply air differential pressure respectively;

[0018] The control unit makes real-time comparisons and judgments and issues corresponding instructions. When the difference rate is less than or equal to the set value, the blower unit maintains normal constant air volume automatic control operation. When the comparison difference rate of any dual-loop measurement signal is greater than the set value, the control unit immediately issues an instruction to the blower unit to switch the constant air volume automatic control operation to manual control operation to ensure the stability of the stator blade angle.

[0019] As a further improvement of the present invention, in step 5), the comparative difference control ranges of the supply air temperature, supply air pressure and supply air differential pressure are -30°C≤(T1-T2)≤30°C, -0.03MPa≤(P1-P2)≤0.03MPa, and -0.3kPa≤(ΔP1-ΔP2)≤0.3kPa, respectively.

[0020] As a further improvement of the present invention, in step 6), the setting values ​​of the comparison difference rates of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure are 10%, 5% and 2% respectively.

[0021] As a further improvement of the present invention, the flow monitor is a Venturi tube flow monitor.

[0022] 3. Beneficial effects

[0023] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0024] The method for monitoring and controlling the air flow rate of a large blast furnace blower unit of the present invention has good safety and reliability, and can effectively avoid situations such as large fluctuations in the blast furnace air supply and serious impact on production caused by various abnormalities or failures in the air flow rate measurement circuit, thereby ensuring stable operation of the blower unit and safe production of the blast furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the air supply flow monitoring and control method of a large blast furnace blower unit of the present invention.

[0026] Description of the numbers in the schematic diagram:

[0027] 1. Control unit; 2. Blower unit; 3. Air supply duct; 4. Check valve; 5. First air supply temperature monitoring; 6. Second air supply temperature monitoring; 7. First air supply pressure monitoring; 8. Second air supply pressure monitoring; 9. First air supply differential pressure monitoring; 10. Second air supply differential pressure monitoring; 11. Flow monitor; 12. Air supply valve; 13. Blast furnace. DETAILED DESCRIPTION

[0028] In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments.

[0029] like Figure 1This is a structural schematic diagram of the air supply flow monitoring and control method of a large blast furnace blower unit of the present invention. In this embodiment, a large blast furnace blower unit air supply flow monitoring device is provided, wherein an air supply duct 3 is connected between the blower unit 2 and the blast furnace 13; a check valve 4, a flow monitor 11 and an air supply valve 12 are sequentially connected in series on the air supply duct 3; a first air supply temperature monitor 5, a second air supply temperature monitor 6, a first air supply pressure monitor 7 and a second air supply pressure monitor 8 are provided on the air supply duct 3 between the check valve 4 and the flow monitor 11; a first air supply differential pressure monitor 9 and a second air supply differential pressure monitor 10 are provided on the flow monitor 11; a control unit 1 is respectively connected to the first air supply temperature monitor 5, the second air supply temperature monitor 6, the first air supply pressure monitor 7, the second air supply pressure monitor 8, the first air supply differential pressure monitor 9 and the second air supply differential pressure monitor 10 through a signal transmission line; and the control unit 1 is connected to the blower unit 2 through a signal transmission line.

[0030] The steps for monitoring and controlling the air flow rate of a large blast furnace blower unit are as follows:

[0031] 1) The blast furnace is in normal production and the blower unit is in constant air volume automatic control operation.

[0032] 2) The dual-loop measurement signals of supply air temperature, supply air pressure and supply air differential pressure are transmitted to the control unit in real time. The dual-loop measurement signals are divided into two groups. One group of signals is used for supply air flow monitoring, operation monitoring and constant air volume automatic control operation of the blower unit, and the other group of signals is used for supply air flow monitoring and signal comparison with the control system.

[0033] 3) The control unit calculates the contrast difference rate of the dual-circuit measurement signals in real time and compares it with the set value. When the measurement circuits are in normal state, the difference rate will always be less than the set value, and the blower unit will maintain constant air volume automatic control operation. When any measurement circuit has an abnormality or failure, its difference rate will be greater than the set value. The control unit will immediately send a command to the blower unit to switch the constant air volume automatic control operation to manual control operation, effectively avoiding malfunction of the stator blade angle, ensuring stable operation of the blower unit and safe air supply to the blast furnace.

[0034] 4) When the blower unit is in manual control operation, find the cause of the abnormality or failure in the measurement circuit and solve it, then switch the blower unit from manual control operation to constant air volume automatic control operation.

[0035] 5) If the measurement circuit is abnormal or fails and the machine needs to be shut down for processing, the standby blower unit can be started to supply air to the blast furnace and the faulty blower unit can be shut down.

[0036] The specific implementation process is as follows:

[0037] During normal blast furnace production, the blower unit is in constant air volume automatic control operation. A set of normal air supply parameter monitoring signals are: ΔP = 5.4 kPa, P = 0.4 MPa, T = 200 ° C, and the calculated air supply flow rate Q = 4533 m 3 / min9, in actual production, the instantaneous fluctuation of the air flow of the blower unit is set to no more than 200m 3 / min, that is, the instantaneous decrease or increase of air flow does not exceed 200m 3 / min, which will not affect the blast furnace production, and the fluctuation of air flow shall not exceed 200m 3 / min is the limiting condition. Based on the above set of normal air supply parameter monitoring signals, the allowable variation values ​​of the three signal parameters of supply air temperature, supply air pressure and supply air differential pressure are calculated, as shown in the following table:

[0038]

[0039] From the data in the table above, we can see that when comparing a set of normal air supply parameter monitoring signals, the air supply temperature, air supply pressure, and air supply differential pressure vary within the range of ±30°C, ±0.03MPa, and ±0.3kPa respectively, the fluctuation of the blast furnace air supply flow rate will not exceed 200m 3 / min.

[0040] In practice, for the same air supply differential pressure, air supply pressure or air supply temperature signal, two measurement circuits will almost never have anomalies at the same time; when one measurement circuit has an anomaly or failure, its measurement signal will definitely show a sudden change, while the other circuit is in a normal state and its measurement signal is in a normal state. The measurement signals of the two circuits will inevitably show a significant difference, so the present invention adopts a pairwise comparison method of dual-circuit measurement signals, based on ensuring that the fluctuation amplitude of the blast furnace air supply flow is not greater than 200m 3 / min, determine the comparative difference control range of air supply temperature, air supply pressure and air supply differential pressure are ±30℃, ±0.03MPa and ±0.3kPa respectively. Relative to the measuring range of each signal, the maximum allowable difference rate are: 30℃÷300℃(measuring range)×100%=10%, 0.03MPa÷0.6MPa(measuring range)×100%=5%, 0.3kPa÷15kPa(measuring range)×100%=2%.

[0041] The double-circuit measurement signal comparison difference rate formulas (|(T1-T2) / 300|, |(P1-P2) / 0.6|, |(ΔP1-ΔP2) / 15|) and set values ​​(10%, 5%, 2%) of the supply air temperature, supply air pressure and supply air differential pressure are set in the blower unit control unit. The control unit makes real-time comparison and judgment and issues corresponding instructions. When the difference rate is less than or equal to the set value, the blower unit maintains normal constant air volume automatic control operation. When the comparison difference rate of any double-circuit measurement signal is greater than the set value, the control unit immediately issues an instruction to the blower unit to switch the constant air volume automatic control operation to manual control operation to ensure the stability of the stator blade angle, thereby ensuring safe air supply production in the blast furnace.

[0042] By experimenting with various abnormalities or faults that may occur in the measuring circuits, it was found that for the same signal, no matter which measuring circuit has an abnormality or fault, there will be a comparative difference in the measuring signals of the two circuits, and the difference rate will be much larger than the set value; using the above technical solution, for the blower unit with constant air volume automatic control operation, any of the measuring circuits of supply air temperature, supply air pressure and supply air differential pressure, once an abnormality or fault occurs, the control unit will immediately switch the constant air volume automatic control operation to manual control operation, effectively preventing the stator blade angle from malfunctioning, ensuring the stable operation of the blower unit and the safe air supply to the blast furnace.

[0043] During normal blast furnace production, the normal air supply parameter signal changes with the blast furnace conditions and seasonal changes. This normal change in air supply parameters (air supply differential pressure, air supply pressure and air supply temperature) will not affect the application of the dual-loop measurement signal pairwise comparison and difference rate control method of this embodiment.

[0044] The accuracy level of pressure and temperature instruments in the blower unit air flow monitoring system is usually required to be no less than 0.5, and the accuracy level of differential pressure instruments is usually required to be no less than 0.2, that is, the measurement accuracy error of supply air pressure and supply air temperature is within the range of ±0.5%, and the measurement accuracy error of supply air differential pressure is within the range of ±0.2%. Based on the instrument accuracy level, it can be seen that the absolute value of the relative error of the dual-loop measurement signal is no more than 1% and 0.4% respectively, and the instrument accuracy error is within the allowable range of the dual-loop measurement signal comparison difference rate setting value of the present invention.

[0045] Comparison of failure cases before and after implementation of the air flow monitoring, control and supervision method for a large blast furnace blower unit of the present invention:

[0046] Take Ma'anshan XX Company 2500m 3 and 4000m 3 For example, Ma'anshan XX Company has two 2500m blast furnaces. 3 and two 4000m 3 Large blast furnace, equipped with 3 AV80 and 3 AV100 blower units.

[0047] The existing blower unit air flow monitoring and control system used a single circuit to measure air temperature, air pressure, and air differential pressure. Production statistics over the past decade showed 16 abnormalities or failures in the air flow measurement circuit, impacting blast furnace production to varying degrees. Some of these cases are listed below:

[0048] On May 30, 2006, the AV80-2# blower unit's air supply temperature transmitter failed, and its output signal was zero, causing the blower unit's stator blade angle to drop from 45% to 22.8%, and the blast furnace air volume to drop from 4367m 3 / min instantly dropped to 1256m 3 / min, which had a great impact on the blast furnace condition. The molten iron output was reduced by more than 800 tons, with a direct economic loss of 500,000 yuan. The blast furnace returned to normal production condition after 5 hours.

[0049] On November 29, 2008, the air supply temperature transmitter of AV80-1# blower unit failed, and its output signal was zero. The blower unit shed load, and the air distribution device was put into operation to implement the 2# fan to supply air to 1# blast furnace and 2# blast furnace at the same time. Before the failure, the air supply flow rates of 1# and 2# blast furnaces were 4500m3 / min and 4450m3 / min respectively. The failure caused the air supply flow rates of 1# and 2# blast furnaces to instantly decrease to 1970m3 / min and 2200m3 / min, which had a great impact on the furnace conditions of both blast furnaces. The molten iron output was reduced by more than 1900 tons, with a direct economic loss of 1.1 million yuan. Both blast furnaces returned to normal production conditions after 4 hours.

[0050] On November 1, 2013, water accumulated in the air supply differential pressure sampling duct of the AV80-2# blower unit, causing the stator blade angle to close rapidly. The blower unit operating point entered the anti-surge protection zone, resulting in a load rejection accident. The air distribution device was put into operation and the 1# fan supplied air to the 1# blast furnace and the 2# blast furnace at the same time. Before the failure, the air supply flow rates of the 1# and 2# blast furnaces were 4460m3 / min and 4420m3 / min respectively. When the failure occurred, the air supply flow rates of the 1# and 2# blast furnaces were instantly reduced to 1920m3 / min and 2100m3 / min, which had a significant impact on the conditions of both blast furnaces. The molten iron output was reduced by more than 1,600 tons, with a direct economic loss of 900,000 yuan. The two blast furnaces returned to normal production conditions 4 hours later.

[0051] On November 7, 2022, the transmission lines of the air differential pressure, air pressure and air temperature signals of the air flow measurement circuit of the AV100-1# blower unit were damaged due to construction work, resulting in a sudden change in the angle of the blower unit's static blades, the activation of the backflow protection, and the opening of the anti-surge valve. The blast furnace was shut down for nearly 4 hours, the molten iron output decreased by more than 2,200 tons, and the maintenance costs such as replacement of the tuyere sleeve increased. The direct economic loss was more than 1.5 million yuan, and the blast furnace returned to normal production conditions 10 hours later.

[0052] Starting from January 2023, a dual-loop measurement method was adopted for the monitoring, control and supervision of the air flow of the blast furnace blower unit. The measurement signal of one loop was used for the air flow monitoring, operation monitoring and constant air volume automatic control operation of the blower unit. The measurement signal of the other loop was used for signal comparison between the air flow monitoring and control system. In the more than one year since the implementation of this program, the air flow measurement loop had experienced three abnormal failures. The control system carried out effective monitoring and control, avoiding the three abnormal failures of the measurement loop from affecting blast furnace production. The following are some examples:

[0053] On May 14, 2023, the supply air temperature transmitter of the measurement loop used for the constant air volume automatic control operation of the AV80-2# blower unit failed, and the output signal was zero. The supply air temperature transmitter of the other measurement loop used for comparison was in normal operation, and its output signal was a normal signal. The control system immediately compared the signals of the two measurement loops and switched the blower unit from constant air volume automatic control operation to manual control operation, ensuring the stability of the stator blade angle and blast furnace air volume, avoiding the impact on the blast furnace condition and the economic loss of reduced molten iron production. Taking advantage of the blast furnace outage opportunity, the faulty transmitter was replaced and the system returned to normal.

[0054] On August 26, 2023, water accumulated in the air supply differential pressure sampling duct of the measurement circuit used for the constant air volume automatic control operation of the AV100-1# blower unit, resulting in an abnormal differential pressure signal. The differential pressure sampling duct and differential pressure signal of the other measurement circuit for comparison were normal. The control system immediately compared the signals of the two measurement circuits and switched the blower unit from constant air volume automatic control to manual control operation, ensuring the stability of the stator blade angle and blast furnace air volume, avoiding the impact on the blast furnace condition and the economic loss of reduced molten iron production. Without stopping the blower unit, the system returned to normal after draining the faulty air supply differential pressure sampling duct.

[0055] Through the above case examples, it can be seen that since the adoption of the dual-loop monitoring method of the present invention, the operating stability of the blower unit has been significantly improved. When various abnormalities or failures occur in the air supply flow measurement circuit, the blast furnace can be ensured to have safe and stable air supply, effectively avoiding abnormal fluctuations in blast furnace air volume, furnace condition influence, air interruption accidents, and economic losses such as reduced molten iron production. It has obvious advantages over the single-loop monitoring method in terms of safety and economy.

[0056] During the implementation process, the control ranges of the contrast difference of the supply air temperature, supply air pressure and supply air differential pressure are -30℃≤(T1-T2)≤30℃, -0.03MPa≤(P1-P2)≤0.03MPa, and -0.3kPa≤(ΔP1-ΔP2)≤0.3kPa, respectively. The supply air flow rate calculation formula of a venturi tube flow monitor is used. (Where: Q is the air flow rate, Nm 3 / min; ΔP is the air supply differential pressure, kPa; P is the air supply pressure, MPa; T is the air supply temperature, °C) and a set of normal air supply parameter monitoring signals (ΔP = 5.4 kPa, P = 0.4 MPa, T = 200 °C), the air supply flow rate Q = 4533 m 3 / min. If P and ΔP remain unchanged and T decreases or increases by 30℃, the air flow rate will increase by 150m 3 / min or reduce 137m 3 / min; if T and ΔP remain unchanged, P decreases or increases by 0.03MPa, the air flow rate decreases by 138m 3 / min or increase by 133m 3 / min; if P and T remain unchanged, ΔP decreases or increases by 0.3kPa, the air flow rate will decrease by 128m 3 / min or increase by 124m 3 / min. In summary, the design contrast difference control ranges of the air supply temperature, air supply pressure and air supply differential pressure are -30℃≤(T1-T2)≤30℃, -0.03MPa≤(P1-P2)≤0.03MPa, and -0.3kPa≤(ΔP1-ΔP2)≤0.3kPa, respectively. This can ensure that the fluctuation amplitude of the air supply flow rate does not exceed 4%, thereby ensuring the safe air supply and stable furnace condition of the blast furnace. Exceeding this design range will cause the fluctuation amplitude of the air supply flow rate to exceed 4%, which will affect the stability of the blast furnace condition. The larger the contrast difference control range is designed, the greater the fluctuation amplitude of the air supply flow rate and the greater the impact on the blast furnace.

[0057] In order to avoid the influence of the ratio of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure on the system control, the setting values ​​of the comparison difference rate of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure are set to 10%, 5% and 2% respectively. If the setting value is too large, when any signal measurement circuit of the set of supply air temperature, supply air pressure and supply air differential pressure signals used for the constant air volume automatic control operation of the blower unit is abnormal or fails, the fluctuation of the supply air flow of the blower unit will exceed 4%, which will have a great impact on the stability of the blast furnace condition; if the setting value is too small, due to the combined influence of factors such as the normal error of the instrument accuracy of the measuring elements and transmitters in the signal measurement circuit and the normal attenuation of the transmission line signal, even if the dual measurement circuits are in normal working condition, the comparison difference rate of the dual-loop measurement signals may be greater than the set value, which will cause the blower unit to be unable to achieve normal constant air volume automatic control operation.

[0058] In this embodiment, a venturi tube flow monitor is mainly used, and a bar flow meter and an orifice flow meter can also be used. Compared with the latter two types of flow monitors, the venturi tube flow monitor uses multi-point measurement and parameter averaging, and the accuracy level can reach 0.5, which is higher than the orifice flow meter. Due to the effect of the contraction and diffusion sections of the venturi tube, its pressure loss is small, and it is more energy-efficient than the orifice flow meter. The geometric characteristics of the venturi tube make it have less wear and tear, and the surface is wear-resistant and corrosion-resistant after special treatment. It does not require frequent cleaning, regular inspection and replacement. Compared with other flow meters, it is not only safe and reliable, with a long service life, but also has a small maintenance workload and low operating costs.

[0059] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A method for monitoring and controlling the air flow rate of a large blast furnace blower unit, comprising a blower unit, an air supply duct, and a blast furnace connected in sequence, wherein the air supply duct is provided with a check valve, a flow monitor, and an air supply valve in sequence, and characterized in that: The control steps are as follows: S1: Two air supply temperature monitoring points A and B, two air supply pressure monitoring points C and D, and two air supply differential pressure monitoring points E and F set on the flow monitor are set on the air supply duct between the check valve and the flow monitor; S2: The supply air temperatures detected by supply air temperature monitoring points A and B are T1 and T2, the supply air pressures detected by supply air pressure monitoring points C and D are P1 and P2, and the supply air differential pressures detected by supply air differential pressure monitoring points E and F are ΔP1 and ΔP2; S3: Connect the supply air temperature monitoring points A and B, the supply air pressure monitoring points C and D, and the supply air differential pressure monitoring points E and F to the control unit through transmitters and signal transmission lines to form a dual measurement loop. The dual measurement loop signals are divided into two groups, namely T1, P1, ΔP1 and T2, P2, ΔP2. Both groups of signals are transmitted to the control unit in real time. One group of signals (T1, P1, ΔP1) is used for supply air flow monitoring, operation monitoring and constant air volume automatic control operation of the blower unit, and the other group of signals (T2, P2, ΔP2) is used for supply air flow monitoring and signal comparison with the control system; S4: Calculate the air flow rate based on the measured T1, P1, and ΔP1 values. The calculation formula is: Where: Q is the air flow rate, Nm 3 / min; ΔP is the air supply differential pressure, kPa; P is the air supply pressure, MPa; T is the air supply temperature, °C; S5: In actual production, the allowable variation values ​​of the three signal parameters of supply air temperature, supply air pressure, and supply air differential pressure are designed based on the fact that the instantaneous decrease or increase of the supply air flow Q does not exceed 4%, and the control range of the comparison difference of the dual-loop measurement signal is set; S6: Setting the comparison difference rate calculation formula and set value of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure through the control unit. The comparison difference rate calculation formulas are: |(T1-T2) / Tt|, |(P1-P2) / Pp|, |(ΔP1-ΔP2) / ΔPp|; Among them, Tt, Pp and ΔPp are the maximum range values ​​of supply air temperature, supply air pressure and supply air differential pressure respectively; The control unit makes real-time comparisons and judgments and issues corresponding instructions. When the difference rate is less than or equal to the set value, the blower unit maintains normal constant air volume automatic control operation. When the comparison difference rate of any dual-loop measurement signal is greater than the set value, the control unit immediately issues an instruction to the blower unit to switch the constant air volume automatic control operation to manual control operation to ensure the stability of the stator blade angle.

2. The method for monitoring and controlling the air flow rate of a large blast furnace blower unit according to claim 1, characterized in that: In step 5), the control ranges of the comparison differences of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure are -30°C ≤ (T1-T2) ≤ 30°C, -0.03MPa ≤ (P1-P2) ≤ 0.03MPa, and -0.3kPa ≤ (ΔP1-ΔP2) ≤ 0.3kPa, respectively.

3. The method for monitoring and controlling the air flow rate of a large blast furnace blower unit according to claim 1, characterized in that: In step 6), the setting values ​​of the comparison difference rates of the dual-loop measurement signals of the supply air temperature, supply air pressure and supply air differential pressure are 10%, 5% and 2% respectively.

4. The method for monitoring and controlling the air flow rate of a large blast furnace blower unit according to claim 1, characterized in that: The flow monitor is a venturi tube flow monitor.

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