The equipment in front of the blast furnace generally refers to the mud gun, the opening machine and the uncovering machine. Its basic function is to open and block the iron mouth in time to meet the requirements of ironmaking and tapping of the blast furnace. With the continuous expansion of the blast furnace volume and the improvement of the top pressure, the hydraulic mud gun, the hydraulic tapping machine and the hydraulic uncovering machine have replaced the traditional blast furnace front equipment into the blast furnace front hydraulic supporting equipment in the blast furnace smelting. Because the hydraulic equipment in front of the blast furnace requires different flow rates in different processes, so that the hydraulic equipment is designed, the hydraulic pump and the motor are selected according to the high power required in the working cycle, but the hydraulic equipment is large in actual operation. Part of the time is under load, so the efficiency of the hydraulic equipment is not high. This paper comprehensively considers the energy-saving problem of hydraulic equipment from the perspective of system, and combines the frequency conversion control technology with the hydraulic technology to form a new energy-saving transmission mode, so as to achieve the good power matching of the hydraulic equipment in front of the blast furnace.
1 The inverter is used to control the hydraulic pump motor to realize the function of the variable pump, which can reduce or even eliminate the overflow loss and achieve good energy saving effect; and overcome the complicated shortcomings of the traditional variable automatic electric pump control. In the frequency conversion control system, the PLC with the PID control module automatically controls the inverter to change the output flow of the hydraulic pump according to the system requirements.
2Frequency control system in the hydraulic equipment in front of the blast furnace 21 The hydraulic system of the blast furnace in front of the furnace The hydraulic system of the blast furnace is generally composed of hydraulic mud gun, hydraulic opening machine and hydraulic uncovering machine. The hydraulic mud gun is After the blast furnace is tapped, the mud is pressed out of the equipment that blocks the taphole, and the gun, gun and mud are mainly completed.
The mud gun hydraulic system mainly consists of a main pump 3, a mud hydraulic cylinder 9, a hydraulic cylinder 12 and a rotary hydraulic cylinder 14. Each actuator in the system adopts manual reversing valve control and throttling speed regulation. The pressure of the gun action is controlled by the hydraulic control check valve. In order to avoid hydraulic shock, the system's various operating pressure values ​​are monitored in stages, reducing the operating pressure (the pressure of the gun action and the mud retreating action are reduced by the pressure reducing valve or the relief valve). A balancing valve is provided in the transfer circuit to avoid the hydraulic shock caused by the stoppage of the mud gun during the rotation process. This mud gun hydraulic system is reliable and safe. However, the flow rates of the hydraulic cylinders are quite different, which is difficult to match the rated flow rate of the main pump. If the overflow flow is too large, the system loses a large amount of energy and causes the oil temperature to rise.
22 Frequency conversion control principle of hydraulic equipment in front of the blast furnace The large flow loss is caused by the mismatch between the flow rate required by the actuators of the hydraulic equipment in front of the blast furnace and the output flow of the hydraulic pump. Research on the use of variable frequency drive technology in the front of the blast furnace furnace hydraulic equipment, using the frequency converter to control the hydraulic pump motor can fundamentally overcome the ills of the energy consumption of the hydraulic equipment in front of the blast furnace, while also solving the long-term demand for the system due to the quantitative pump The problem of noise and temperature rise caused by the flow and the temperature rise of the oil caused by the overflow, thereby extending the life of the machine.
The inverter control of the hydraulic system of the hydraulic equipment in front of the blast furnace, including the hydraulic system and the electronic control system of the hydraulic equipment. The hydraulic system is integrated and simplified, a throttle valve is arranged on the oil inlet path of the actuator, and a pressure sensor sampling throttle valve inlet and outlet pressure difference is added to the throttle valve inlet and outlet. The output signal of the pressure sensor is transmitted to the PLC with the PID control module. The PLC controls the output frequency of the inverter by the PID control method, and changes the rotation speed of the hydraulic pump motor so that the output flow of the hydraulic pump is equal to the flow rate adjusted by the throttle valve to realize the hydraulic pressure. The flow rate of the system is matched. At this time, the pressure difference between the front and the back of the throttle valve and the set pressure difference (set according to different process speeds in the working cycle) are equal, thereby automatically controlling the running speed of the actuators in different processes in the working cycle. The application of variable frequency control motor speed to control the output flow of the hydraulic pump can simplify the system speed control loop and cancel the overflow valve overflow circuit. At the same time, the output pressure of the pump is automatically adapted to the pressure required by each actuator, and the reduction of the operating pressure is eliminated. The pressure valve and the relief valve reduce the power loss and oil temperature rise, enabling energy-saving transmission and control.
The frequency conversion control hydraulic system essentially uses the volume throttling speed regulation principle to adjust the speed. The flow adjustment into the throttle valve is used to change the flow rate into the hydraulic cylinder, and the inlet and outlet pressure difference of the throttle valve is monitored to ensure the passage of the throttle valve. The flow rate is set value, and the inlet and outlet pressure difference is used as a feedback signal. The speed of the hydraulic pump motor is controlled by the frequency converter, so that the output flow of the hydraulic pump is automatically adapted to the required flow rate of the hydraulic cylinder. Although there is still a certain throttling loss in this circuit, there is no overflow loss, high efficiency, good speed load characteristics, smooth motion, and wide speed regulation range.
At the same time, the system can also adopt the touch screen technology to realize the mechanical buttonlessness of the control system and the visualization of the equipment state, which makes the hydraulic system control more clear and easy to operate. The touch screen can edit various screens as needed, and display the operation instruction information of the system in real time. The touch button on the man-machine interface can generate the corresponding switch signal, or input the value and character to the PLC for data exchange, thereby generating the corresponding action control device operation.
23PID control algorithm In order to make the throttle pressure difference between the inlet and outlet of the throttle valve equal to the set pressure difference, the system adopts the PID control method. The PID controller is a linear controller which forms a control deviation e(t)=r(t)-c(t) according to a given value r(t) and an actual output value c(t), and the ratio of the deviation, The integral and the differential are controlled by a linear combination to control the controlled object. The control law is: u(t)=Kpe(t)1TI(t0e(t)dtTDde(t)dt where Kp proportional coefficient TI integral time constant TD differential time constant Since the system is controlled by PLC, so the Digital PID controller: u(k)=KPe(k)KI)Kj=0e(j)KD[e(k)-e(k-1)] The control quantity of the kth sampling time of u(k) e(k) error at the kth sampling time e(k-1) error at the k-1th sampling time Kp proportional coefficient KI integral coefficient KD differential coefficient The system uses the differential pressure sensor to sample the inlet and outlet pressure difference of the throttle valve As the input of the PID control module, the output of the inverter is controlled by the PID operation, thereby controlling the rotation speed of the hydraulic pump motor, so that the flow rate outputted by the hydraulic pump is automatically adapted to the flow rate of the hydraulic cylinder.
The working process of 24 frequency conversion control hydraulic system consists of closed loop system consisting of PLC, frequency converter and differential pressure sensor. According to the speed of different processes in the working cycle, the pressure difference between the inlet and outlet of the throttle valve is set as the given value of PID control. The pressure signal output by the differential pressure sensor is scanned as an input signal of the PID control module. After the throttle cross-sectional area AT is set, the flow rate through the throttle valve is constant. When the output flow of the hydraulic pump is greater than the required flow rate of the hydraulic cylinder, the pressure before the throttle valve rises, the pressure difference between the inlet and outlet increases, and the differential pressure sensor transmits to the PLC, and the PLC calculates and outputs a signal to the inverter through the PID control module. The output frequency of the inverter is reduced, the speed of the motor is reduced, and the pump output flow is reduced. Until the pump output flow rate is equal to the required flow rate of the hydraulic cylinder, the pressure difference between the inlet and outlet of the throttle valve returns to the set value, and the adjustment is completed. Conversely, when the output flow of the hydraulic pump is less than the required flow rate of the hydraulic cylinder, the pressure before the throttle valve is lowered, the pressure difference between the inlet and outlet is lowered, the output frequency of the inverter is increased, the rotational speed of the motor is increased, and the pump output flow rate is increased until When the pump output flow rate is equal to the required flow rate of the hydraulic cylinder, the pressure difference returns to the set value and the adjustment is completed. The function of the throttle valve not only keeps the flow into the hydraulic cylinder constant, but also keeps the output flow of the hydraulic pump constant and matches the flow of the hydraulic cylinder.
3 Characteristics of frequency conversion control of hydraulic equipment in front of blast furnace 1) High energy utilization rate of system In this system, the principle of volume throttling speed regulation is adopted, and there is no overflow loss. By reasonably setting the pressure difference between the inlet and outlet of the throttle valve, the throttling loss of the throttle valve in the load range is reduced, and the wear and noise caused by the high speed of the motor and the high-speed operation of the hydraulic pump at a small flow rate are overcome. , thereby increasing the utilization of system energy.
2) The system is simple and reliable. The system uses the frequency converter to control the speed of the hydraulic pump motor to realize the function of the variable pump. It eliminates the complicated variable displacement mechanism of the variable pump in the traditional volumetric speed control circuit and the pressure reducing valve and overflow to reduce the operating pressure. The valve simplifies the speed control loop in the hydraulic system and makes the hydraulic system simple.
3) High control accuracy of the system During the whole control process, the PLC checks the inlet and outlet pressure difference of the throttle valve at any time as the input signal of the PID control module that comes with the PLC. The PID control module controls the output of the inverter according to the deviation value at the sampling time. This forms a closed-loop control system with high control accuracy.
4) The system has small impact on the power grid. The inverter is used instead of the AC contactor to control the hydraulic pump motor, so that the hydraulic pump motor is non-contact control, and the operation is smooth, which can protect the system equipment from impact, thereby reducing the grid voltage fluctuation caused by the system operation. . According to the actual situation, the parameters such as starting, braking time and running speed are adjusted to achieve the good running state.
5) It is easy to realize automatic control. The variable frequency pump that controls the hydraulic pump motor speed to realize the variable itself is easier to realize automatic control than the traditional variable pump. In this control system, the inlet and outlet pressure difference of the throttle valve can be set according to different processes in the working cycle to automatically control the running speed of the actuator during different processes in the working cycle.
4 Conclusion The hydraulic equipment in front of the blast furnace is controlled by frequency conversion, which can improve its energy utilization and automation level, and reduce temperature rise and noise. The control concept of the system can be applied to hydraulic systems with multiple actuators or hydraulic systems with variable loads.
1 The inverter is used to control the hydraulic pump motor to realize the function of the variable pump, which can reduce or even eliminate the overflow loss and achieve good energy saving effect; and overcome the complicated shortcomings of the traditional variable automatic electric pump control. In the frequency conversion control system, the PLC with the PID control module automatically controls the inverter to change the output flow of the hydraulic pump according to the system requirements.
2Frequency control system in the hydraulic equipment in front of the blast furnace 21 The hydraulic system of the blast furnace in front of the furnace The hydraulic system of the blast furnace is generally composed of hydraulic mud gun, hydraulic opening machine and hydraulic uncovering machine. The hydraulic mud gun is After the blast furnace is tapped, the mud is pressed out of the equipment that blocks the taphole, and the gun, gun and mud are mainly completed.
The mud gun hydraulic system mainly consists of a main pump 3, a mud hydraulic cylinder 9, a hydraulic cylinder 12 and a rotary hydraulic cylinder 14. Each actuator in the system adopts manual reversing valve control and throttling speed regulation. The pressure of the gun action is controlled by the hydraulic control check valve. In order to avoid hydraulic shock, the system's various operating pressure values ​​are monitored in stages, reducing the operating pressure (the pressure of the gun action and the mud retreating action are reduced by the pressure reducing valve or the relief valve). A balancing valve is provided in the transfer circuit to avoid the hydraulic shock caused by the stoppage of the mud gun during the rotation process. This mud gun hydraulic system is reliable and safe. However, the flow rates of the hydraulic cylinders are quite different, which is difficult to match the rated flow rate of the main pump. If the overflow flow is too large, the system loses a large amount of energy and causes the oil temperature to rise.
22 Frequency conversion control principle of hydraulic equipment in front of the blast furnace The large flow loss is caused by the mismatch between the flow rate required by the actuators of the hydraulic equipment in front of the blast furnace and the output flow of the hydraulic pump. Research on the use of variable frequency drive technology in the front of the blast furnace furnace hydraulic equipment, using the frequency converter to control the hydraulic pump motor can fundamentally overcome the ills of the energy consumption of the hydraulic equipment in front of the blast furnace, while also solving the long-term demand for the system due to the quantitative pump The problem of noise and temperature rise caused by the flow and the temperature rise of the oil caused by the overflow, thereby extending the life of the machine.
The inverter control of the hydraulic system of the hydraulic equipment in front of the blast furnace, including the hydraulic system and the electronic control system of the hydraulic equipment. The hydraulic system is integrated and simplified, a throttle valve is arranged on the oil inlet path of the actuator, and a pressure sensor sampling throttle valve inlet and outlet pressure difference is added to the throttle valve inlet and outlet. The output signal of the pressure sensor is transmitted to the PLC with the PID control module. The PLC controls the output frequency of the inverter by the PID control method, and changes the rotation speed of the hydraulic pump motor so that the output flow of the hydraulic pump is equal to the flow rate adjusted by the throttle valve to realize the hydraulic pressure. The flow rate of the system is matched. At this time, the pressure difference between the front and the back of the throttle valve and the set pressure difference (set according to different process speeds in the working cycle) are equal, thereby automatically controlling the running speed of the actuators in different processes in the working cycle. The application of variable frequency control motor speed to control the output flow of the hydraulic pump can simplify the system speed control loop and cancel the overflow valve overflow circuit. At the same time, the output pressure of the pump is automatically adapted to the pressure required by each actuator, and the reduction of the operating pressure is eliminated. The pressure valve and the relief valve reduce the power loss and oil temperature rise, enabling energy-saving transmission and control.
The frequency conversion control hydraulic system essentially uses the volume throttling speed regulation principle to adjust the speed. The flow adjustment into the throttle valve is used to change the flow rate into the hydraulic cylinder, and the inlet and outlet pressure difference of the throttle valve is monitored to ensure the passage of the throttle valve. The flow rate is set value, and the inlet and outlet pressure difference is used as a feedback signal. The speed of the hydraulic pump motor is controlled by the frequency converter, so that the output flow of the hydraulic pump is automatically adapted to the required flow rate of the hydraulic cylinder. Although there is still a certain throttling loss in this circuit, there is no overflow loss, high efficiency, good speed load characteristics, smooth motion, and wide speed regulation range.
At the same time, the system can also adopt the touch screen technology to realize the mechanical buttonlessness of the control system and the visualization of the equipment state, which makes the hydraulic system control more clear and easy to operate. The touch screen can edit various screens as needed, and display the operation instruction information of the system in real time. The touch button on the man-machine interface can generate the corresponding switch signal, or input the value and character to the PLC for data exchange, thereby generating the corresponding action control device operation.
23PID control algorithm In order to make the throttle pressure difference between the inlet and outlet of the throttle valve equal to the set pressure difference, the system adopts the PID control method. The PID controller is a linear controller which forms a control deviation e(t)=r(t)-c(t) according to a given value r(t) and an actual output value c(t), and the ratio of the deviation, The integral and the differential are controlled by a linear combination to control the controlled object. The control law is: u(t)=Kpe(t)1TI(t0e(t)dtTDde(t)dt where Kp proportional coefficient TI integral time constant TD differential time constant Since the system is controlled by PLC, so the Digital PID controller: u(k)=KPe(k)KI)Kj=0e(j)KD[e(k)-e(k-1)] The control quantity of the kth sampling time of u(k) e(k) error at the kth sampling time e(k-1) error at the k-1th sampling time Kp proportional coefficient KI integral coefficient KD differential coefficient The system uses the differential pressure sensor to sample the inlet and outlet pressure difference of the throttle valve As the input of the PID control module, the output of the inverter is controlled by the PID operation, thereby controlling the rotation speed of the hydraulic pump motor, so that the flow rate outputted by the hydraulic pump is automatically adapted to the flow rate of the hydraulic cylinder.
The working process of 24 frequency conversion control hydraulic system consists of closed loop system consisting of PLC, frequency converter and differential pressure sensor. According to the speed of different processes in the working cycle, the pressure difference between the inlet and outlet of the throttle valve is set as the given value of PID control. The pressure signal output by the differential pressure sensor is scanned as an input signal of the PID control module. After the throttle cross-sectional area AT is set, the flow rate through the throttle valve is constant. When the output flow of the hydraulic pump is greater than the required flow rate of the hydraulic cylinder, the pressure before the throttle valve rises, the pressure difference between the inlet and outlet increases, and the differential pressure sensor transmits to the PLC, and the PLC calculates and outputs a signal to the inverter through the PID control module. The output frequency of the inverter is reduced, the speed of the motor is reduced, and the pump output flow is reduced. Until the pump output flow rate is equal to the required flow rate of the hydraulic cylinder, the pressure difference between the inlet and outlet of the throttle valve returns to the set value, and the adjustment is completed. Conversely, when the output flow of the hydraulic pump is less than the required flow rate of the hydraulic cylinder, the pressure before the throttle valve is lowered, the pressure difference between the inlet and outlet is lowered, the output frequency of the inverter is increased, the rotational speed of the motor is increased, and the pump output flow rate is increased until When the pump output flow rate is equal to the required flow rate of the hydraulic cylinder, the pressure difference returns to the set value and the adjustment is completed. The function of the throttle valve not only keeps the flow into the hydraulic cylinder constant, but also keeps the output flow of the hydraulic pump constant and matches the flow of the hydraulic cylinder.
3 Characteristics of frequency conversion control of hydraulic equipment in front of blast furnace 1) High energy utilization rate of system In this system, the principle of volume throttling speed regulation is adopted, and there is no overflow loss. By reasonably setting the pressure difference between the inlet and outlet of the throttle valve, the throttling loss of the throttle valve in the load range is reduced, and the wear and noise caused by the high speed of the motor and the high-speed operation of the hydraulic pump at a small flow rate are overcome. , thereby increasing the utilization of system energy.
2) The system is simple and reliable. The system uses the frequency converter to control the speed of the hydraulic pump motor to realize the function of the variable pump. It eliminates the complicated variable displacement mechanism of the variable pump in the traditional volumetric speed control circuit and the pressure reducing valve and overflow to reduce the operating pressure. The valve simplifies the speed control loop in the hydraulic system and makes the hydraulic system simple.
3) High control accuracy of the system During the whole control process, the PLC checks the inlet and outlet pressure difference of the throttle valve at any time as the input signal of the PID control module that comes with the PLC. The PID control module controls the output of the inverter according to the deviation value at the sampling time. This forms a closed-loop control system with high control accuracy.
4) The system has small impact on the power grid. The inverter is used instead of the AC contactor to control the hydraulic pump motor, so that the hydraulic pump motor is non-contact control, and the operation is smooth, which can protect the system equipment from impact, thereby reducing the grid voltage fluctuation caused by the system operation. . According to the actual situation, the parameters such as starting, braking time and running speed are adjusted to achieve the good running state.
5) It is easy to realize automatic control. The variable frequency pump that controls the hydraulic pump motor speed to realize the variable itself is easier to realize automatic control than the traditional variable pump. In this control system, the inlet and outlet pressure difference of the throttle valve can be set according to different processes in the working cycle to automatically control the running speed of the actuator during different processes in the working cycle.
4 Conclusion The hydraulic equipment in front of the blast furnace is controlled by frequency conversion, which can improve its energy utilization and automation level, and reduce temperature rise and noise. The control concept of the system can be applied to hydraulic systems with multiple actuators or hydraulic systems with variable loads.
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