Air compressor guide vane control method and device in cryogenic oxygen production industry

Abstract

The invention relates to an air compressor guide vane control method and device in the cryogenic oxygen production industry. The device comprises a current signal, an air compressor motor, a guide vane, a guide vane feedback signal, a manual operation control module, a current PID adjusting module, an exhaust pressure PID adjusting module and an air compressor exhaust pressure transmitter. According to the method, air compressor current and exhaust pressure analog quantity signals are introduced into a guide vane AO output control PID adjusting program, the manual / automatic control strategy of the air compressor guide vane can be achieved, the suggested position of the guide vane is calculated according to the normal value of the running current and the normal value of the exhaust pressure, a guide vane control interval is formed, surge of the air compressor caused by misoperation of personnel is effectively prevented, and the service life of the air compressor is prolonged. And meanwhile, the economic benefit is remarkable, and the economic loss is reduced by more than hundreds of thousands.

Description

Technical Field

[0001] This patent application belongs to the field of intelligent control technology, and more specifically, it relates to a guide vane control method and device for an air compressor in the cryogenic oxygen production industry. Background Art

[0002] At present, cryogenic oxygen production is widely used in manufacturing industries such as steel metallurgy, new energy, and chemical industry. In industrial production, ensuring the safe and stable supply of product media is of paramount importance. Therefore, the stable operation of the air compressor is the key to deep-cold oxygen production in air separation. The most important thing for the air compressor is the guide vane control system. At present, the guide vane control system of the air compressor generally adopts manual fuzzy control by the operator, or adopts a single PID control. On the one hand, such methods are prone to human error and lead to unplanned shutdown accidents of air separation. At the same time, in the single PID automatic control, when the reference signal point fails, etc., it is very easy for the air compressor to have abnormal conditions. Therefore, it is necessary to design a control method to achieve manual / automatic control of the guide vane safety. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a guide vane control method and device for an air compressor in the cryogenic oxygen production industry, which can eliminate manual misoperation by personnel. After adding multiple groups of PID control to the program, the guide vane movement can be controlled more accurately to ensure long-term stable operation of the equipment.

[0004] In order to solve the above problems, the technical solution adopted by the present invention is: A method for controlling guide vanes of an air compressor in a cryogenic oxygen production industry comprises the following steps: S1. According to the current signal and the exhaust pressure signal of the air compressor during target operation, combined with the current error and the rate of change of the error, the guide vane MV target output values ​​under two groups of conditions are calculated respectively, which belongs to the scope of the prior art; S2, determine whether it is in manual control mode or automatic control mode, if it is in manual control mode, execute S3-S4, otherwise execute S5-S6; S3. In manual control mode, according to the actual output values ​​of two groups of guide vane MV calculated by the current signal and the exhaust pressure signal, the lowest data of the two is selected as the reference value, and the guide vane signal output suggestion is made according to the reference value, and the next step is executed; this step is to choose one of the two, and take the lowest data as the reference value, which belongs to the start state; S4. The operator manually inputs the guide vane MV value. When the manually input guide vane MV value is higher than the reference value, the system considers that there is a risk of surge and does not perform the manually given operation, but continues to execute the previously running guide vane MV value to eliminate manual misoperation by the operator. When the manually input guide vane MV value is not higher than the reference value and the absolute value of the change is not greater than the safety adjustment value, the manually input guide vane MV value is executed. This step ensures that although manual adjustment is possible, the adjustment must be within a certain range to avoid large adjustments due to negligence or fatigue and other physical conditions of the operator.

[0005] S5. In the automatic control mode, the two sets of actual output values ​​of the guide vane MV calculated according to the current signal and the discharge pressure signal are selected and output as the guide vane MV value automatically given by the system to control the opening of the guide vane; this step also selects the lowest value as another reference value, which belongs to the normal operating state; S6. When the air compressor motor is ready to load signal, when the guide vane MV value automatically given by the system is higher than the minimum guide vane opening value under the equipment operating state, it is executed according to the system's automatic setting; when the guide vane MV value automatically given by the system is lower than or equal to the minimum guide vane opening value under the equipment operating state, it is executed according to the minimum guide vane opening value under the equipment operating state.

[0006] Furthermore, in S4, the safety adjustment value is 2.5 degrees to 8 degrees to prevent large fluctuations in the load of the air compressor.

[0007] Further, in S6, the minimum guide vane opening value when the equipment is in operation is the minimum value during the equipment surge commissioning period, and is normally set to 20 degrees.

[0008] Furthermore, in the "execution" of S4 and S6, the current signal and exhaust pressure signal of the air compressor operation are adjusted by PID. This step is intended to illustrate that, for example, in the automatic control mode, after setting the target values ​​of the operating current and exhaust pressure, the two sets of guide vane MV output values ​​calculated by the actual operating current and exhaust pressure function are used for low-select output, and the action is controlled by PID (generally using the matching function block PID, P proportional-I integral-D differential) to achieve the stability of the output air flow and avoid large opening and closing.

[0009] A guide vane control device for an air compressor in a cryogenic oxygen production industry is used to implement the above control method. The device includes an air compressor current signal, an air compressor motor, a guide vane, a guide vane feedback signal, a manual operation control module, a current PID adjustment module, an exhaust pressure PID adjustment module, an air compressor exhaust pressure transmitter, and a DCS system, wherein: The air compressor motor is connected to a current transformer, and the air compressor current signal obtained by the current transformer is connected to the current PID regulation module; the air compressor guide vane is connected to the air compressor exhaust pressure transmitter, and the pressure signal of the air compressor exhaust pressure transmitter is connected to the exhaust pressure PID regulation module; The manual operation control module, current PID adjustment module and exhaust pressure PID adjustment module are all connected to the guide vanes through instructions. The guide vane operation generates a guide vane feedback signal, which is connected to the DCS system. The manual operation control module, current PID regulation module and exhaust pressure PID regulation module are configured and edited by the DCS system. The DCS system converts the air compressor exhaust pressure transmitter, air compressor current signal and guide vane feedback signal into digital display and presents them on the computer screen operated by the operator in the main control room for easy observation by the operator. The PID regulation data required for the current PID regulation module and the exhaust pressure PID regulation module are derived from the equipment operation data screening.

[0010] Furthermore, the air compressor current signal, the air compressor exhaust pressure transmitter signal, and the guide vane feedback signal are all 4~20mA signals.

[0011] Due to the adoption of the above technical solution, the beneficial effects achieved by the present invention are: This control method innovatively introduces the air compressor current and exhaust pressure analog signals into the guide vane AO ​​output control PID adjustment program, so as to more accurately control the guide vane movement and realize the manual / automatic control strategy of the air compressor guide vane. Under manual control, the recommended guide vane position can be calculated according to the operating current and the normal exhaust pressure values, and the guide vane control range is formed based on the reference value. When the manually input guide vane MV value is higher than the reference value, the system considers that there is a risk of surge and does not perform the manually given operation. When the manually input guide vane MV value is not higher than the reference value and the absolute value of the change is not greater than the safety adjustment value, the manually input guide vane MV value is executed to eliminate manual misoperation by personnel and reduce losses caused by personnel fatigue, experience, physical condition, etc.

[0012] In automatic control, two sets of guide vane output data calculated by actual operating current and exhaust pressure are low-selected and output as the guide vane MV value automatically given by the system. When the guide vane MV value automatically given by the system is higher than the minimum guide vane opening value under the equipment operating state, it is executed according to the system automatic setting; when the guide vane MV value automatically given by the system is lower than or equal to the minimum guide vane opening value under the equipment operating state, it is executed according to the minimum guide vane opening value under the equipment operating state, so as to ensure long-term stable operation of the equipment.

[0013] In addition, a device for implementing the present invention is provided, which has a simple structure, simple hardware connection, and convenient maintenance, and effectively prevents risks such as air compressor surge and air separation shutdown caused by personnel misoperation, thereby ensuring long-term stable operation of the equipment. In addition, the economic benefits are significant. According to the situation that the guide vane accident shutdown occurs once every two years, the economic loss reduced is more than 600,000. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 It is the lower operation flow chart of DCS system; Figure 3 This is the detailed control program diagram of the DCS for the air compressor guide vane; Figure 4 The upper PIDEX control function block calls the panel through the lower screen bit number Figure 1 .

[0015] Figure 5 The upper PIDEX control function block calls the panel through the lower screen bit number Figure 2 .

[0016] The markings in the figure are as follows: current signal 1, air compressor motor 2, guide vane 3, guide vane feedback signal 4, manual operation control module 5, current PID adjustment module 6, exhaust pressure PID adjustment module 7, air compressor exhaust pressure transmitter 8. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to the embodiments.

[0018] A method for controlling guide vanes of an air compressor in a cryogenic oxygen production industry comprises the following steps: S1. According to the current signal and the exhaust pressure signal of the air compressor during target operation, the guide vane MV target output values ​​under two groups of conditions are calculated respectively in accordance with the prior art in combination with the current error and the rate of change of the error; S2, determine whether it is in manual control mode or automatic control mode, if it is in manual control mode, execute S3-S4, otherwise execute S5-S6; S3. In manual control mode, based on the two sets of guide vane MV actual output values ​​calculated from the current signal and the exhaust pressure signal, select the lowest data of the two as the reference value, and make a guide vane signal output recommendation based on the reference value; this step takes the lowest data from the two sets of guide vane MV actual output values ​​calculated from the current signal and the exhaust pressure signal, that is, choose the minimum number from the two. This situation applies to the start-up state of the air compressor.

[0019] S4. After the reference value is set, the operator manually inputs the guide vane MV value. When the manually input guide vane MV value is higher than the reference value, the system considers that there is a risk of surge and does not perform the manual given operation, but continues to execute the previously running guide vane MV value to eliminate manual misoperation by the operator; when the manually input guide vane MV value is not higher than the reference value and the absolute value of the change is not greater than the safety adjustment value, the manually input guide vane MV value is executed. The safety adjustment value is 2.5 degrees to 8 degrees, and the adjustment range is small to prevent excessive fluctuations in the compressor load.

[0020] For example, when the current signal is between 900 and 1000A, the guide vane MV value is 37; when the exhaust pressure signal is between 0.4 and 0.5MPa, the guide vane MV value is 35, and 35 is taken as the reference value. Taking the safety adjustment value of 2.5 degrees as an example, when the manually input guide vane MV value is 36, since 36> the reference value 35, it is considered to be a manual error operation, and the manual setting operation is not performed, but the previously running guide vane MV value continues to be executed. If the manually input guide vane MV value is 34, since 34 is less than the reference value 35, and |34-35|=1, the change absolute value 1 is less than the safety adjustment value 2.5, then the manual adjustment is effective. After the adjustment is effective, the current signal and exhaust pressure signal of the air compressor are adjusted by PID. If the manually input guide vane MV value is 32, although 32 is less than the reference value 35, |32-35|=3, the change absolute value 3 is not less than the safety adjustment value 2.5, then the manual adjustment is still invalid, and it is still considered to be a manual error operation, and the manual setting operation is not performed.

[0021] The above is the manual control method, and the following will continue to talk about the automatic control method.

[0022] S5. Under the automatic control mode, the actual output values ​​of the two sets of guide vane MV calculated according to the current signal and the exhaust pressure signal are selected as the guide vane MV value automatically given by the system to control the opening of the guide vane; that is, the lowest value is selected from the two options. This situation applies to the normal operating state of the air compressor.

[0023] S6, when the air compressor motor 2 is ready to load signal, it proves that the air compressor motor 2 is operating normally. When the guide vane MV value automatically given by the system is higher than the minimum guide vane opening value under the equipment operation state, it is executed according to the system automatic setting; when the guide vane MV value automatically given by the system is lower than or equal to the minimum guide vane opening value under the equipment operation state, it is executed according to the minimum guide vane opening value under the equipment operation state. Generally, the minimum guide vane opening value under the equipment operation state is selected as the minimum value during the equipment surge commissioning period, which is generally set to 20 degrees. Of course, it should also be selected according to the specific situation.

[0024] For example, in the automatic control mode, the actual output values ​​of the two sets of guide vane MV calculated according to the current signal and the exhaust pressure signal are 28 and 26 respectively, then the low-selected output 26 is used as the guide vane MV value automatically given by the system. Since 26> the minimum guide vane opening value of 20 when the equipment is in operation, it is executed according to the 26 automatically given by the system. If the actual output values ​​of the two sets of guide vane MV calculated according to the current signal and the exhaust pressure signal are 18 and 19 respectively, then the low-selected output 19 is used as the guide vane MV value automatically given by the system. Since 19< the minimum guide vane opening value of 20 when the equipment is in operation, it is executed according to the minimum guide vane opening value of 20 when the equipment is in operation. During execution, the current signal and exhaust pressure signal of the air compressor operation are adjusted through the PID method, and the PID control method is smoother and more peaceful, avoiding the negative impact caused by large opening and closing of the equipment.

[0025] In general, under manual control, the guide vane MV output value is calculated according to the normal value of the operating current and exhaust pressure, and the low-select output is compared with the manually input guide vane MV value. When the manually input guide vane MV value is high, the system considers that there may be a surge risk and continues to execute the previous operating value, eliminating manual misoperation by personnel. When in automatic control mode, after setting the target values ​​of operating current and exhaust pressure, the two sets of guide vane MV output values ​​calculated by the actual operating current and exhaust pressure function are used for low-select output, and the function block PID (P proportional-I integral-D differential) action control is coordinated to achieve stable output air flow.

[0026] In addition, the present invention also discloses a guide vane control device for an air compressor in the cryogenic oxygen production industry, which is used to implement the above control method, such as Figure 1 The device includes an air compressor current signal 1, an air compressor motor 2, a guide vane 3, a guide vane feedback signal 4, a manual operation control module 5, a current PID adjustment module 6, an exhaust pressure PID adjustment module 7, an air compressor exhaust pressure transmitter 8, and a DCS system, wherein: The air compressor motor 2 is connected to a current transformer, and the air compressor current signal 1 obtained by the current transformer is connected to the current PID adjustment module 6; the guide vane 3 of the air compressor is connected to the air compressor exhaust pressure transmitter 8, and the pressure signal of the air compressor exhaust pressure transmitter 8 is connected to the exhaust pressure PID adjustment module 7; The manual operation control module 5, the current PID adjustment module 6, and the exhaust pressure PID adjustment module 7 are all connected to the guide vane 3 through instructions. The operation of the guide vane 3 generates a guide vane feedback signal 4. The guide vane feedback signal 4 is connected to the DCS system. The guide vane feedback signal 4 meets the operator's need to understand the opening status of the guide vane 3 in real time.

[0027] Manual operation control module 5, current PID adjustment module 6 and exhaust pressure PID adjustment module 7 are configured and edited by DCS system. DCS system converts the exhaust pressure transmitter 8, current signal 1 and guide vane feedback signal 4 of air compressor into digital display and presents them on the computer screen of operator in main control room for convenient observation by operator. PID adjustment data is derived from equipment operation data screening.

[0028] During the design, the air compressor current signal 1, the signal of the air compressor exhaust pressure transmitter 8, and the guide vane feedback signal 4 are all 4~20mA signals.

[0029] The following is a detailed description with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the air compressor motor 2 outputs a current signal 1, and at the same time, the guide vane 3 of the air compressor motor 2 exhausts the air to the air cooling tower and outputs the exhaust pressure through the air compressor exhaust pressure transmitter 8. The current signal 1 (1K-KYJ-I) of the air compressor and the air compressor exhaust pressure (1K-PIT3322A) analog signal are introduced into the guide vane output control PID adjustment program. The above program is established with a current PID adjustment module 6, an exhaust pressure PID adjustment module 7, and a manual operation control module 5. The current signal 1 is output to the current PID adjustment module 6, and the exhaust pressure is output to the exhaust pressure PID adjustment module 7. The current PID adjustment module 6, the exhaust pressure PID adjustment module 7, and the manual operation control module 5 control the guide vane 3 through program instructions respectively. The actual action of the guide vane 3 and the guide vane feedback signal 4 can be observed by on-site feedback, so as to more accurately control the action of the guide vane 3. The current PID adjustment module 6, the exhaust pressure PID adjustment module 7, and the manual operation control module 5 are also connected to the DCS system through program instructions.

[0031] Figure 2 This is the flow chart of the 1# air compressor. The upper left corner shows the status of the surge counter, the excitation cabinet, and the operating cabinet. Figure 2 The middle guide vane 3 is in the unlocked manual state, the given MV output value is 71.3, and the feedback signal is 71.5 (blue font), which proves that the opening of the guide vane 3 is normal. The current PID adjustment module 6 Figure 2 IIC1601 MAN, exhaust pressure PID control module 7 Figure 2 The one in the figure is PIC3322A MAN, both of which are in manual state. After the SV value (planned value / target value) of the output current and the SV value (planned value / target value) of the exhaust pressure are set, the module is set to automatic state, and the guide vane 3 is locked to achieve automatic adjustment.

[0032] Figure 3 As shown in the upper program, under manual control, according to the operating current 1K_IIC1601 ( Figure 3Middle) and exhaust pressure 1K_PIC3322A function block PIDEX ( Figure 3 The guide vane MV output value is calculated based on the current error and the error change rate. MAC_ASL_1002 function block ( Figure 3 Upper right) selects the lowest data of the two for output, and then uses the MAC_ASL_1001 low selection function block ( Figure 3 Right side) and the operator through the 1K_HIC3119T function block ( Figure 3 The system compares the manually input MV value (in the middle and lower part) with the MV value. When the manually input MV value is high, the system considers that there may be a surge risk and continues to execute the previous running value to eliminate manual misoperation by personnel. The program sets a lock setting that the manually given guide vane opening does not exceed 2.5 at a time to prevent large fluctuations in the compressor load. Figure 2 As shown, the recommended opening given by the 1K_IIC1601 and exhaust pressure 1K_PIC3322A function blocks PIDEX is 85, and the actual given is 71.3. When the given is greater than 85, the given operation is not performed.

[0033] In the automatic control state, the two sets of guide vane output data calculated by the operating current and exhaust pressure PIDEX are low-selected and output. When the 1K_SO1001BPSTA motor is ready to load signal, the opening must be higher than 20 (this value comes from the lowest value during the equipment surge commissioning). This setting is set in the ASW function block. When the value output by MAC_ASL_1001 is lower than 20, the guide vane is opened at 20 to ensure long-term stable operation of the equipment.

[0034] The PID (Proportional-Integral-Derivative) calculation used in the present invention is simplified to this formula: u(t)=Kp*e(t)+ Ki*∫e(t)dt+ Kd* de(t) / dt.

[0035] u(t) is the output signal of DCS control AO output within the specified time t, Kp is the proportional coefficient (proportional gain), the proportional term Kp*e(t) is adjusted according to the current error size, Ki is the integral coefficient (integral gain), the integral term (Ki*∫e(t)dt) is adjusted according to the error accumulation, Kd is the differential coefficient (differential gain), e(t) is the error between the input signal of the controller and the expected value, de(t) / dt is the derivative of the error, as the rate of change of the error, the differential term (Kd*de(t) / dt) is adjusted according to the rate of change of the error. In the field exploration, P=100, I=20, D=0 meet the use requirements. Figure 4In the automatic state, after the operator inputs the SV value, the guide vane is stably adjusted according to the situation, so that the measured parameter PV value is infinitely close to the set value.

[0036] Figure 4 , Figure 5 It is a control panel of the current PID regulation module 6 and the exhaust pressure PID regulation module 7. Figure 4 The two preference labels in the middle position correspond to the constraint interval setting of the current and exhaust pressure SV values ​​(planned values ​​or target values) and the guide vane action range setting; Figure 5 The two PID option labels in the middle position represent the PID parameters of the PID three-way regulation control unit.

[0037] From the above description, it can be seen that the control method of the present invention introduces the air compressor current and exhaust pressure analog signals into the guide vane AO ​​output control PID adjustment program, and can realize the manual / automatic control strategy of the air compressor guide vane. Under manual control, the guide vane MV output value is calculated according to the current operating current and exhaust pressure error and the rate of change of the error, forming a guide vane control range. When the manually input MV value is high, the system believes that there may be a surge risk and does not perform the operation, thereby eliminating manual misoperation by personnel. The program sets a lock setting of no more than 2.5 for the guide vane opening at a time, effectively preventing risks such as air compressor surge and air separation shutdown caused by misoperation by personnel, and ensuring long-term stable operation of the equipment. According to the situation where the guide vane accident shutdown occurs once every two years, the economic loss reduced is more than 600,000, and the economic benefit is significant.

Claims

1. A method for controlling guide vanes of air compressors in the cryogenic oxygen production industry, characterized in that The steps include: S1. Calculate the guide vane MV target output values ​​under two groups of conditions according to the current signal and the exhaust pressure signal during the target operation of the air compressor; S2, determine whether it is in manual control mode or automatic control mode, if it is in manual control mode, execute S3-S4, otherwise execute S5-S6; S3. Under manual control mode, the actual output values ​​of two groups of guide vane MVs are calculated based on the current signal and the exhaust pressure signal, and the lowest data of the two is selected as the reference value, and the guide vane signal output recommendation is made based on the reference value; S4. The operator manually inputs the guide vane MV value. When the manually input guide vane MV value is higher than the reference value, the system considers that there is a risk of surge and does not perform the manually given operation, but continues to execute the previously run guide vane MV value to eliminate manual misoperation by the operator; when the manually input guide vane MV value is not higher than the reference value and the absolute value of the change is not greater than the safety adjustment value, the manually input guide vane MV value is executed; S5. In the automatic control mode, the actual output values ​​of the two groups of guide vane MVs calculated according to the current signal and the discharge pressure signal are low-selected and output as the guide vane MV values ​​automatically given by the system; S6. When the air compressor motor is ready to load signal, when the guide vane MV value automatically given by the system is higher than the minimum guide vane opening value under the equipment operating state, it is executed according to the system's automatic setting; when the guide vane MV value automatically given by the system is lower than or equal to the minimum guide vane opening value under the equipment operating state, it is executed according to the minimum guide vane opening value under the equipment operating state.

2. The guide vane control method for air compressor in the cryogenic oxygen production industry according to claim 1, characterized in that: In S4, the safety adjustment value is 2.5 degrees to 8 degrees.

3. The guide vane control method for air compressor in the cryogenic oxygen production industry according to claim 1, characterized in that: In S6, the minimum guide vane opening value when the equipment is in operation is the minimum value during equipment surge commissioning.

4. The guide vane control method for air compressor in the cryogenic oxygen production industry according to claim 1, characterized in that: In the "execution" of S4 and S6, the current signal and exhaust pressure signal of the air compressor are adjusted by PID method.

5. A guide vane control device for an air compressor in the cryogenic oxygen production industry, used to implement the above control method, characterized in that: It includes an air compressor current signal (1), an air compressor motor (2), a guide vane (3), a guide vane feedback signal (4), a manual operation control module (5), a current PID adjustment module (6), an exhaust pressure PID adjustment module (7), an air compressor exhaust pressure transmitter (8), and a DCS system, wherein: The air compressor motor (2) is connected to a current transformer, and the air compressor current signal (1) obtained by the current transformer is connected to a current PID regulation module (6); the air compressor guide vane (3) is connected to an air compressor exhaust pressure transmitter (8), and the pressure signal of the air compressor exhaust pressure transmitter (8) is connected to the exhaust pressure PID regulation module (7); The manual operation control module (5), the current PID adjustment module (6), and the exhaust pressure PID adjustment module (7) are all connected to the guide vane (3) through instructions. The guide vane (3) generates a guide vane feedback signal (4) when it is operated. The guide vane feedback signal (4) is connected to the DCS system. The guide vane feedback signal (4) allows an operator to understand the opening state of the guide vane (3) in real time. The manual operation control module (5), the current PID adjustment module (6), and the exhaust pressure PID adjustment module (7) are configured and edited by the DCS system. The DCS system converts the air compressor exhaust pressure transmitter (8), the air compressor current signal (1), and the guide vane feedback signal (4) into digital display and presents them on the computer screen of the operator in the main control room for observation by the operator.

6. The guide vane control device for air compressor in the cryogenic oxygen production industry according to claim 5, characterized in that: The air compressor current signal (1), the signal of the air compressor exhaust pressure transmitter (8), and the guide vane feedback signal (4) are all 4~20mA signals.

Images