Application of Distributed Control System Based on Field Instrument Communication in Sintering Automatic Batching
Sintering ingredients, as the basic process of steel production, have become increasingly prominent. Although most sinter plants pay attention to it, they also invest in automatic ingredients, and some even have been modified more than once, costing a lot of money.
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Editor's note: Sintering ingredients are the basic process for steel production, and their automation is increasingly prominent. Although most sinter plants pay attention to it, they also invest in automatic ingredients, and some even have been modified more than once, costing a lot of money. But in the end, it can run reliably, and the performance investment ratio is very low. Laiwu Steel Plant adopts the distributed control system based on field instrument communication for the process of factory batching process. After more than one year of practice, it achieves the goal of reliable operation and high performance investment ratio. It has accumulated the design of the automatic adjustment system of the batching of the sintering plant. experience.
Keywords: field communication distributed control sintering batching HART artificial intelligence regulator
1. Laigang 1# sintering machine batching process equipment overview Sintering and batching process is the mixing of iron ore powder, fuel (coke powder), solvent (limestone, dolomite, quicklime) and cold and hot returning minerals required for the production of sintered ore. According to the smelting requirements of blast furnace and the chemical composition of various materials, the batching calculation is carried out to determine the proportion of ingredients of various materials, and the ingredients are realized by weight detection and control of the feeding equipment. There are a total of 17 silos used in the batching room of Laigang Sintering Machine. The details are as follows: Warehouse number 1#-5# 6# 7# 8# 10# 11# 12# 13# 14# 15# 16# 17# 18# Material name Mixing mineral powder Coke powder Coke powder Pulverized coal limestone dolomite quicklime Cold return mine Hot return mine Feeding method disc disc Dragging disc disc disc spiral Dragging disc control method The inverter changes the feed amount
2. Characteristics of the design scheme In view of the problems existing in the traditional automatic control system of sintering batching, in-depth analysis of the on-site process and management status, combined with the latest advanced technology of measurement and control, the design features are as follows:
2.1 The system adopts the distributed control method based on field instrument communication. The design integrates the belt scale, the punching flowmeter, the radar level gauge, the artificial intelligence regulator, etc. through the communication and connection of the U-power intelligent instrument with the on-site communication function. Distributed control system for on-site communication.
The field instrument communication uses a HART communication protocol based on the principle of master-slave protocol. Its characteristic is that the communication only has two instructions for reading and writing. The software of the upper computer is easy to write, and the PC can be used as the upper computer. The software resources are rich and the advantages of rapid development are developed. Compared with analog transmission, it has the advantages of easy commissioning and maintenance and higher precision.
The system has the following advantages:
(1) High reliability.
The photoelectric isolation technology is used to isolate the communication interface from other parts of the instrument. When the communication interface or line fails, the belt scale and regulator can still work normally. Due to the low level digital signal and zero continuous phase average, the anti-interference ability is strong. Simple wiring, easy maintenance and accurate data transmission. The failure between the single-machine detection and control devices does not spread, the failure between the upper and lower machines does not spread, and the impact of the failure on the entire system is minimized, which greatly improves the reliability of the system. Hand and automatic conversion methods are flexible and diverse. It can be converted on the upper computer or the basic regulator, and also on the inverter and the operation box, solving the problem of slow response when the fault occurs.
(2) The upper computer has strong data processing capability and the monitoring program is more abundant.
Since the data is collected by communication, and part of the statistical data of the single machine is completed by the lower computer, the upper computer mainly processes the system data, which can free up more applications with more time and memory processing functions.
(3) Investment province.
The upper computer does not need analog input and output modules and corresponding cabinets, and the hot standby host computer is also eliminated. At the same time, there is no need to add public hardware when adding a single unit, saving system expansion costs. In addition, save signal cables and installation and commissioning fees. It also requires low quality of use and maintenance personnel and saves training costs.
2.2 The hardware equipment is advanced and practical, and the maintenance workload is small. (1) For the general belt scale maintenance workload and poor anti-interference ability, the scale frame is maintenance-free, the weighing of the millivolt signal is digitized on site and the signal becomes 4-20 mA. Belt scales.
(2) Selection of advanced and practical punching scales to detect white ash and hot return flow The continuous detection of white ash and hot return flow is a major problem in sintering ingredients. In the past, white ash was generally detected by a spiral scale, and two belt scales or nuclear scales were used to detect a hot returning point, which were unstable in operation, large in maintenance workload, low in precision, and high in investment. This design uses advanced and practical punching scale testing. The differential amplifier is replaced by a high-precision load cell, which improves stability and detection accuracy, and reduces maintenance workload and technical requirements. At the same time, the use of ceramic wear-resistant punching plate solves the problem of short life of steel punching plates. In addition, the flow signal is processed by the belt scale weighing module, which solves the problem of matching with the host computer.
(3) The basic controller uses advanced artificial intelligence regulator. Whether it can achieve high-precision automatic adjustment, the correct choice of regulator is the key. This design selects Xiamen Yudian AI-808 type artificial intelligence regulator with field communication function and fuzzy regulation for PID adjustment. Compared with the general regulator, it can reduce the overshoot while improving the response speed. When the error is large, the fuzzy algorithm is used to adjust to completely eliminate the PID saturation integral phenomenon; when the error is small, the improved PID algorithm is used for adjustment. It has the functions of automatic learning system characteristics and processing of changes in given values ​​and measured values. There are a variety of setting methods, which can be manually set directly on the panel buttons, and the analog settings can be made on the externally given terminals. In order to prevent abnormal overshoot, it also has a control amount upper and lower limit preset function. At the same time, the debugging is simple and has little impact on normal production. The structure type is hot plug-in type, and the replacement is convenient and quick.
(4) The use of advanced radar level gauge to detect white ash, hot return mine bins, white ash, hot return mine bins, traditional detection methods are weighing, heavy hammer, manual probe, both maintenance difficulties and maintenance workload Large and unreliable. We use an accurate, reliable, maintenance-free radar level gauge for inspection.
2.3 The application function is novel, practical and rich. The application program is written in VB6.0 with good visual performance. Compared with the general ingredient monitoring program, the system monitoring program is new, practical, rich, and has strong human-machine dialogue ability. The outstanding performance is as follows:
(1) The alarm mode adopts the over-range inverse time-limited voice alarm. The traditional alarm is mostly an instantaneous or long-term continuous cumulative amount of sound and light alarm. Due to the limitation of feeding mode (unloading unevenness), the instantaneous amount alarm is often false alarm (recovery when there is no time to process); or the over-difference does not alarm (large deviation) and misses the alarm. Continuous cumulant alarms are also false positives and false negatives because the accumulation time is too short or too long. At the same time, the alarm object should also be matched with the display screen. We use outdated inverse time alarms. That is, a certain cumulative amount (absolute error) and a time interval (shortest processing time) are alarm conditions, and the instantaneous amount error is continuously accumulated and transmitted to the upper computer by communication. The larger the cumulative amount is in the unit time, the shorter the alarm time limit is. On the contrary, the longer the alarm time limit. At the same time, when the instantaneous amount deviation is too large, it will directly alarm. This is neither false nor false. In addition, the voice broadcast system is used to automatically report the alarm object directly and prompt the cause and action. It not only shortens the alarm confirmation and processing time, but also does not require the operator to stare at the screen, reducing the degree of fatigue.
(2) Solved the problem of batch control
The traditional analog centralized control system needs to realize the batch control of the variable material, and the analog quantity setting between the upper computer and the regulator is complicated, and the hardware structure is complicated. We use the preset value of the upper machine to change the set value of the regulator in the field communication mode, and automatically send it according to the principle of the alignment of the material tail, the variable material time is short, and the longest time is only 90 seconds (only by mixing The speed of the belt conveyor and the spacing of the silo are determined. The regulator is not over-adjusted, which reduces the malignant material and unstable production caused by the variation of the material. There is no need to interlock with the electrical during the slow stop.
(3) Yudian AI-808 truly realizes hand and automatic undisturbed fast switching Traditional hand and automatic undisturbed fast switching means that the instantaneous hand and automatic instantaneous output values ​​are equal. In the automatic adjustment of the ingredients, the manual and automatic undisturbed fast switching requires that the control amount before or after the switching is equal to the average value of the controlled quantity. This must first calculate the control amount before the switching or the average value of the controlled quantity, and then switch. The impact on the process is minimized, and the hand and automatic bumpless switching is realized. Obviously, the instantaneous hand and automatic bumpless fast switching in the traditional sense is not applicable to this. Therefore, we use the field communication to manually switch to the automatic switching, first calculate the average value of the controlled amount per minute at the time of the host computer; this value is used as the initial value at the initial time; The upper computer tracks and calculates the average value of the control amount per minute at that time, and uses this value as the control value at the time of manual initial. Then set them to the artificial intelligence regulator, and finally the average hand, the automatic bumpless fast switching. A successful conversion has been achieved, which solves the problem of having to modify the control amount or set value many times during manual and automatic switching, and it is still difficult to achieve the switching request value, causing production fluctuations and prolonging the stabilization time.
2.3.4 Automatically correct the original set value of the corresponding adjuster after zero calibration and calibration, and automatically calculate the new set value corresponding to the original set value according to the zero change and the accuracy change before and after the calibration. To ensure that the new set value is equal to the original set value, avoiding the additional error caused by zero calibration and calibration, and maintaining the continuity of production. The general batching system does not have this function.
2.3.5 Realized the automatic record of over-difference, change of position, break, change, and slow material, and query by time, which solved the problem of real-time supervision of process discipline of the batching process.
When the above alarm occurs, the display automatically pops up a dialog box with the contents of the alarm object, the cause of the alarm, the processing method, the duty person, etc., and the attendant confirms item by item. Clearly clarified the responsibility, strengthened the self-discipline awareness of the operators, laid the foundation for the correct analysis of the causes of fluctuations, and was conducive to the steady improvement of the technological level.
2.3.6 Historical trend chart The ordinate is divided into two scale segments, which ensures that the size and flow rate clearly distinguish the instantaneous quantity change trend on the same screen.
2.3.7 View and modify the parameters of each scale in the upper computer display, and the calibration scale is convenient.
2.3.8 The material level of the silo is virtual indicating that the initial material quantity is reduced by the material amount, and the material level can be accurately indicated without the material level meter.
2.3.9 In the data packaging method, the ingredient information can be transmitted without error, and the query can be made in different places, and the ingredient information sharing is realized, and the process management level is improved.
2.3.10 The setting of the ratio is flexible and diverse. The formula can be calculated according to the process ingredients. After inputting the relevant components and total amount, the set amount can be calculated automatically, or the set value can be input one by one after being manually calculated; it can be uniformly pre-set according to the batch batch control requirements on the host computer, or Set separately on each basic regulator.
2.3.11 The historical statistics of the stand-alone unit are stored in their corresponding modules, saving the time and memory of the host computer and increasing the room for system expansion.
2.3.12 Units of measurement can be click-swapped between t/h and kg/m for on-site verification.
2.3.13 The display screen has a help menu for easy operation and maintenance.
3. Effect After two years of operation and practice, the system works stably and reliably, which reduces the labor intensity of operation and maintenance personnel. Due to the automatic detection and adjustment, the manual running plate weighing is greatly reduced, and more time can be vacated, and hidden dangers can be discovered in time, thereby reducing sudden accidents and processing workload. At the same time, the alarm is accurate and timely, and the workload of interference and handling of faults is also reduced. In particular, the variable material and the hand and automatic conversion are in place at the same time, which not only enhances the control real-time, improves the control precision, but also reduces the labor intensity of repeated weighing. The man-machine interface is intuitive, the function is simple to operate, and there is also a help menu, which is easy to learn. The monitoring program has strong man-machine dialogue capability, facilitates process management, improves the operator's sense of responsibility, reduces abnormal fluctuations, and promotes the improvement of production indicators.
The system realizes continuous control of the stability of the control and the accuracy of the cumulative control per minute is ±1.5% in the disc feeding mode. It satisfies the process requirements of changing, slowing, hand, automatic switching, smooth transition before and after calibration, and accurate and timely transfer of ingredient information. The application function integrates measurement, control and management, achieving the goal of high performance investment ratio.
4, existing problems and improvement measures 4.1 communication speed is slow. Further improve the function of the lower computer, so that the data taken by the upper computer is counted as much as possible in the lower computer and stored in the designated storage unit. At the same time, the use of data compression technology to reduce the amount of data transmission shortens the communication time. In addition, increase the communication baud rate.
4.2 Unloading of feeding equipment is uneven. Further change the feeding mode and change the disc feeding to a wide belt.
4.3 Physical verification is difficult. Add a mobile hopper scale at the blanking point of the belt conveyor, and check the scale at any time.
4.4 Instrument control and electronic control separation. The instrument control and electronic control are combined, and the AI-301M type switch input/output module is adopted to realize the system automatic and ingredient information into the production management information network. Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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