In the production of ironmaking, the size and performance of the air blower capacity of the blower is the key to the high yield of the blast furnace. Swiss Sulzer fans are in an absolute leading position in performance and technology in China's current wind turbine systems. It has the advantages of precise mechanism, high efficiency, good air supply characteristics, stable operation, etc., but the control system is strict and related to it. In the past, the imported Sulzer fan control system was controlled by DCS plus conventional control instruments. The system cost was high and the reliability depends on the adjustment control instrument. The fan control system currently developed in China is still very imperfect. The level of system operation depends mainly on the developer's own understanding of the system and the understanding of the performance of the fan, which often causes some problems due to personnel errors. Therefore, users have strong requirements for perfecting and regulating the control system of blast furnace blowers. This paper discusses the PLC control of the Swiss AV63 12 axial flow blast furnace blower. 1 Fan system configuration can be seen, for the blower system, the air enters the blower after passing through the filter plenum. After the blower works, it is discharged from the exhaust duct, and the exhaust duct is divided into three paths leading to the anti-surge valve, the electric vent valve and the main damper. When the unit is in normal working condition, the anti-surge valve and the electric vent valve are closed, and the air discharged from the fan is led to the blast furnace by the main damper. If the fan operating point enters the anti-surge control, the control system will open the anti-surge valve to release the air to reduce the outlet pressure of the fan, so that the operating point of the fan is far from the surge boundary. The anti-surge valve is divided into a large valve and a small valve, and the size anti-surge valve is a split-range control method. When both anti-surge valves fail and cannot work normally, the operator manually controls the electric vent valve to complete the venting operation. The vane angle actuator of the fan is a servo device that performs the operation of pushing the vane angle. 2 Control system structure design The blast furnace compressor control station hardware selects Siemens S7 400 series high-end PLC. Engineer station (ES) and operator station (OS) select Siemens industrial PC and install Siemens WinCC human-machine interface platform software under Windows2000, The Siemens Industrial Ethernet card CP1613. The switch uses Siemens Industrial Ethernet Switch OSM ITP62. The schematic diagram of the control system is shown. 3 control function realization 3.1 fixed air volume / constant air pressure adjustment system 3. 1. 1 static vane adjustable concept full vane adjustable axial flow compressor blade set consists of multi-stage rotating blades (called moving blades) and several A class of stationary blades (called stationary leaves). The angle between the vane and the moving blade is called the vane angle. The vane angle is that the vane angle can be adjusted by the control system. For example: The vane angle of the AV 63 12 full vane adjustable axial compressor is adjustable between 14 and 79. The smaller the vane angle, the smaller the outlet air volume and wind pressure of the compressor, and the lighter the load of the main motor of the drag compressor. In order to reduce the starting current of the main motor, it is required that the vane angle of the compressor at start-up is 14, so 14 is also referred to as the compressor starting angle. But the angle of the vane Between 14 22, the operation of the compressor is in a pneumatically unstable state, which is very unfavorable for the operation of the unit. Therefore, the angle of the vane should be adjusted to 22 as soon as possible after the compressor unit is started. This process is called The leaves are released. When the compressor unit supplies air to the blast furnace normally, the vane angle is continuously adjustable between 22 and 79 according to the process requirements, so 22 is also referred to as the minimum working angle of the compressor. If there is no stop state after the release of the vane, the vane angle cannot be adjusted to 22 or less, which is set to ensure the safe operation of the unit. 3. 1. 2 Static blade servo system The axial flow compressor adjusts the air volume and wind pressure by adjusting the change of the vane angle of the compressor. The vane angle adjustment loop consists of a cascade loop formed by inner loop control and outer loop control, as shown. The outer ring part is completed by the PID adjustment controller inside the PLC; the inner ring part includes a vane position transmitter, a vane servo controller and a vane servo mechanism. By adjusting the change of the vane angle, the output of the compressor can be increased and decreased according to the requirements of the process state. When the process requires little air volume, the load of the compressor is also reduced, and there is no energy waste caused by the venting operation. Very obvious. Servo controller: In the inner loop control part, the vane servo controller sends a servo command signal to drive the vane servo mechanism by comparing the control signals from the position transmitter and the PLC, and pushes the vane cylinder to move in the specified direction. Stable control of pressure and air volume. PLC internal circuit: In the outer ring control part, the operator can select constant pressure or constant flow control, manual or automatic control, set the target value according to the process requirements, and the PID regulator can automatically adjust the pressure or flow. 3. 2 anti-surge regulation system Surge is the inherent characteristic of turbomachinery. It is the pulsating flow formed by the compressor on the blade under low flow conditions, which is formed between the air volume and the air resistance of the outlet pipe network. Oscillation phenomenon. The surge hazard of axial compressors is far greater than other types of compressors, mainly in the following aspects: 1 Because the gap between the moving and stationary blades is small, when the surge occurs, excessive vibration will damage the components such as the blades. . 2 Airflow pulsation and internal temperature rise can jeopardize the blades and the inner cylinder. 3 Large fluctuations in flow and pressure can cause the compressor to change from positive flow characteristics to negative flow characteristics, making operation unstable and the compressor entering reverse flow conditions. According to the above situation, the axial compressor must be prohibited from entering the surge condition. 3. 2. The meaning of anti-surge control The supply requirements and furnace conditions of the blast furnace during the iron making process will cause changes in the flow and pressure of the auxiliary pipe network and the machine. When the air flow in the machine is under low flow conditions, the fan Will run to the surge zone. At this time, a flow of air is generated on the cascade of the fan to form a pulsating flow, and a self-oscillation phenomenon is formed between the air volume and the air resistance of the attached pipe network. The pressure and flow pulsations of the airflow in the fan and the associated pipe network may develop into an amplitude oscillation, which creates a periodic backflow of airflow and a sharp drop in the pressure of the exhaust gas, and produces a huge squeak and a sharp temperature rise, ie surge. The impact of the airflow during the surge is transmitted to the blades, causing alternating stresses on the shaft, causing the shaft to vibrate. Due to the small gap between the moving and stationary cascades, excessive mechanical vibration caused by this time will damage the blade and other parts. The airflow pulsation and the internal temperature rise will also endanger the blade and the inner cylinder; the large oscillation of flow and pressure will occur. This causes the fan to run from a positive flow characteristic to a negative flow characteristic, allowing the fan to enter a reverse flow condition, so anti-surge control must be set. 3. 2. 2 anti-surge control principle and method of fully static vane adjustable axial compressor Since the root cause of surge is caused by excessive exhaust pressure, the corresponding exhaust pressure when the unit surges is called asthma Vibration pressure, the same type of vane adjustable axial compressor according to manufacturing, installation location, installation accuracy, intake air temperature, atmospheric pressure, etc., the surge pressure will change, and the full static vane adjustable axial compressor The corresponding surge pressures at different vane angles are also different. The key to anti-surge regulation is the setting of anti-surge control curve, which not only affects the safety program of the blower, but also affects the operating range and energy venting of the blower. It is the control and adjustment core in the anti-surge control system. From the measured relationship between the fan throat differential pressure (P) and the exhaust pressure P, the characteristic curve and the surge curve of the fan are obtained, that is, the corresponding asthma is measured at different vane angles (throat differential pressure). Vibration pressure, generally measured at least 5 7 points. The measured points are connected by a broken line to draw a curve in which the abscissa is the differential pressure of the throat and the ordinate is the exhaust pressure parameter, which is called the surge line of the unit. The anti-surge line of the original unit was obtained by moving the ordinate parameter of the surge line down by 5% 10%. A measured surge line and anti-surge line are shown. The anti-surge line is obtained by moving the ordinate coordinate parameter of the surge line down by 5%. 3. 2. 3 PLC implementation method of anti-surge control Because the signal failure judgment measures are taken, the phenomenon of mis-empting and accidental shutdown caused by signal failure is eliminated. In the program, the variable constant PID adjustment algorithm is used to ensure that the operating point is quickly away from the surge region and the pressure fluctuation caused by the venting is minimized in the process of anti-surge adjustment. Temperature and pressure compensation algorithms are used to adapt the anti-surge control to various climatic conditions. The anti-surge adjustment manual/automatic low selection method and corresponding confirmation prompts are used to eliminate the possibility of misoperation. The control method combines the characteristics of the full static vane adjustable axial compressor and the actual requirements of the compressor process, and improves the stability and reliability of the system control under the premise of reliable protection of the compressor. Anti-surge control method for fully static vane adjustable axial compressor. 3. 2. 4 Anti-asthmatic line calculation The measured intake air temperature T = 31, first turn T into 0 1 number, which is T MD, ie T MD = (T + 50) / < 50-(- 50)> = (T + 50)/ 100. Compensation factor p 01 = < 50 - (- 50)> / (273. 15 + T ) = 0. 33; p 02 = < 273. 15 + (- 50)> / ( 273. 15 + T) = 0. 73. The value obtained by temperature compensation T MD p 01 + p 02 is sent to the PLC for control. The measured surge line is the exhaust pressure P and the throat differential pressure measured at different vane angles. The vane angle conversion formula is (the vane angle - 14 ) 100 / ( 79 - 14 ), and the vane angle is converted. The degree of opening (%) is increased by 5% of the exhaust pressure to obtain an anti-asthmatic line. The ST EP7 anti-asthmatic line is obtained by dividing the exhaust pressure P by 0.6 M Pa to obtain a number of 0 1 and dividing the throat differential pressure P by 20 KPa to obtain a number of 0 1 . The P and P values ​​(number of 0 1) are sent to the PLC for control as the ST EP7 anti-asthmatic line. The WinCC coordinates (surge line) are obtained by transforming the measured exhaust pressure and the throat differential pressure. (500-583.33 exhaust pressure) as the WinCC exhaust pressure coordinate, (100 + 25 throat differential pressure) as the WinCC throat differential pressure coordinate. The WinCC coordinates (anti-asthmatic line) are obtained by moving the exhaust pressure coordinate down by 5%. Test results and calculation data are recorded. 3. 3 important logic interlocking control system in addition to setting constant air volume / constant air pressure regulation control and anti-surge regulation control, there are safe operation mode of the unit, start interlock, static blade release (electric tow unit), automatic operation , Countercurrent, continuous countercurrent, excessive shaft vibration, excessive shaft displacement, low power oil pressure, low lubricating oil pressure and other shutdown interlock protection to protect the safety of the compressor unit. Operation safety interlock is the most important key equipment to control the start/stop and running state of the compressor. The main control object is high-voltage electric interlock (electric tow unit), adjustable vane, anti-surge valve quick-opening solenoid valve, reverse Stop the valve. During the operation of the unit, various safety interlock functions are associated with each other at a certain timing to realize the interlock control of the compressor unit to ensure the safety of the unit. In addition, an alarm message prompt is set for each control variable in the PLC control program and the upper man-machine interface, so that the operator can quickly find the fault point and deal with the fault in time. 3. 3. 1 Unit start control setting Start condition The purpose of interlock control is to ensure that the external conditions and internal conditions necessary for the unit before starting are all in compliance with the requirements, to ensure safe and normal start-up of the unit. The main external conditions are: lubricating oil temperature, lubricating oil pressure, power oil pressure, vane position, anti-surge valve position, etc. Internal state conditions refer to the state of various internal memories used for unit safety interlocking. Reset all. When all the conditions are met, the system issues a signal to allow the start, otherwise the boot operation is invalid. 3. 3. 2 Emergency stop control During the operation of the unit, if any of the following accidents is a serious failure of the unit, in order to prevent the accident from further expanding and ensuring the safety of the entire unit, an emergency shutdown is required. The main external conditions for interlocking shutdown are: (1) the lubricating oil pressure is too low (three take two); (2) the power oil pressure is too low (three take two); (3) manual emergency stop (from the electric control panel); (4) Soft key manual emergency stop; (5) Fan shaft displacement is too large; (6) Fan shaft vibration is too large; (7) Unit continues to flow backward; (8) Main motor running signal disappears. The result of the emergency stop procedure is to open the vent valve quickly, the check valve closes quickly, and the vane locks to 14. The interlock locks the automatic locking of the adjustable vane, check valve and anti-surge valve while turning off the unit driving energy. In a safe location, the cause of the downtime is automatically recorded and maintained for later verification. 3. 3. 3 Countercurrent protection Countercurrent is the most dangerous condition for axial compressors. Countercurrent protection is the most important protection for axial compressors. Since the outlet pressure is high and the compressed gas cannot be unobstructed, the rotating mechanical energy converts it into heat to expand the blade, causing the moving blade and the stationary blade to collide and damage the axial compressor. The fundamental measure to prevent backflow is to strengthen anti-surge control, prevent further surges in surge conditions, and prevent backflow of outlet gases. Countercurrent protection is achieved through the close connection between logic control and anti-surge control. The logic system performs comprehensive judgment processing according to the strength of the surge and the duration of the surge, and implements different measures in three stages: (1) Elimination by automatic adjustment of anti-surge control; (2) Passing the safe operation procedure To eliminate the reverse flow conditions; (3) Emergency shutdowns are implemented as a last resort. Under the action of anti-surge regulation, the anti-surge valve is automatically adjusted when the unit is close to surge, which ensures that the unit's working conditions will not reach the surge point. However, considering that in the event of special circumstances (such as anti-surge valve regulation failure), the unit also has the danger of entering the surge zone. It is precisely for this kind of precaution to set up the countercurrent protection interlock. During the operation, it is automatically determined whether the unit has surge and reverse flow, so as to perform safety interlocking in case of surge, to ensure the unit is absolutely safe. 3. 4 Auxiliary Equipment Control Auxiliary equipment refers to a variety of peripheral equipment essential to the operation of the compressor. From the perspective of ensuring the continuous operation of the compressor, these peripheral equipment are not as important as the unit itself. Auxiliary equipment monitoring mainly includes: lubricating oil auxiliary oil pump control, power oil pump control, lubricating oil tank heater control, power tank heater control, turning mechanism control, electric air supply valve control, etc. 4 Conclusion The development and standardization of the Sulzer AV series fan control system has been put into operation in Hangzhou Iron and Steel Group Corporation. After more than one year of operation, the performance of the control system is stable, the detection accuracy is high, the protection function is perfect, and the anti-interference ability is strong. In particular, the on-line display and control of the anti-surge curve has played an important role in the safe and reliable operation of the fan and has achieved the expected results. chenille/towel computerized embroidery machine Chinese Embroidery Machine,Towel Embroidery Machine,Coiling Embroidery Mahcine Haibo Machinery Co., Ltd. , http://www.embroiderymachine-manufacturer.com
Improvement of the design and function of the blower