The first part of the design of technical documents
I. Overview
In recent years, the iron and steel smelting industry in China has developed rapidly. Sintered ore is the main raw material for ironmaking. The process of furnish is an important part of the quality of sinter. Each weighing equipment can guarantee the quality of ore only if it reaches a certain accuracy.
The traditional sintering process mainly relies on work experience to adjust, there are the following problems:
D can not adjust the ratio in time, production efficiency is low.
D Due to the lack of metering equipment, there are many man-made influencing factors, the material can not be well controlled, the waste is serious, the production cost is greatly increased, the failure rate is high, and a large amount of waste products are caused.
D Due to the serious dust pollution of materials, it seriously affects the health of workers. In recent years, the degree of automation in industrial processes has become higher and higher and people’s awareness of environmental protection has increased. Frequency conversion technology has been widely used at home and abroad for its excellent performance.
Second, the main functions and features of the system
1, the main function of the control system
A monitoring function: to detect and monitor the instantaneous flow rate, daily total, monthly total, annual total, etc. of the belt weighing process;
A screen display: Through the computer display can display the operating parameters of the control parameters in the process of ingredients, and display real-time ingredients curve and table;
A print management: can print the ingredients report at any time, in order to save and query;
A communication function: IPC can carry out two-way data and information exchange between PLC and instrument;
A. Data processing: The system can automatically process the collected signals and output them to the corresponding control volume.
A control function: According to the corresponding set value before operation, automatic control of the normal operation of the equipment, including PID adjustment;
A alarm function: the host computer uses the screen mode and acousto-optic signal mode to alarm various parameters or device status abnormalities.
2, the main features of the system
A adopts a small and medium-sized distributed control system in the system structure to achieve "decentralized control and centralized management" and overcome the "dangerous concentration" problem;
A upper computer and lower computer are relatively independent. It has manual, automatic and semi-automatic switching functions. When online, they exchange information with each other according to a specific protocol. When offline, a single scale can independently realize the process closed-loop process control.
A host computer is far away from the operation site, which improves the stability of the system and improves the working environment of the operator.
A lower position machine chooses the programmable controller, has the very strong anti-jamming ability, the programming is simple and easy to grasp, can in long-term reliable operation in the harsh environment;
A adopts PID adjustment to improve the system's dosing accuracy, and can set the optimal working switch timing according to production requirements, better solve the problem of feed end of material, and automatically modify the material ratio of the dosing system;
Third, the system structure and working principle
1, the overall structure of the control system topology and system schematics
The system consists of a PLC system and a host computer monitoring system. The PLC system consists of an S7-300 master station and 13 instruments as slave stations and dedicated communication cables. The master station and slave station communicate via PROFIBUS-DP. The host computer monitoring system uses the Windows 2000 Professional Server SP2 operating system and installs Siemens STEP 7 programming software. WINCCV6.0 configuration software.
The overall topology of the control system and the system schematic are as follows:
System schematic
B host computer: real-time monitoring of the entire system, screen display and report printing;
B PLC: automatic control of ingredients;
B batching instrument: It is used for the PID adjustment of the ingredients and the display of the instantaneous flow and cumulative flow and other parameters;
B control cabinet: for the system's logic control and power distribution;
B. Field operation box: It is used to start and stop the single equipment in the field.
2. The operating mode of the system: Each batch of ingredients is called manual, semi-automatic, automatic three control methods
When B is manual, switch the on-site control box and meter box to the manual position. The on-off control button, potentiometer, and frequency meter on the field control box are used to control the meter. The weighing meter displays the instantaneous and cumulative quantities of the materials. . Mainly used for network system failure PLC control system failure or other reasons, need to manually repair the emergency operation under test conditions.
When B is semi-automatic, switch the on-site control box and meter box switch to the automatic position. The on-off control button, frequency meter, and weighing indicator on the field control box can realize the control. The recipe can be set by the weighing meter. Automatically adjust the dosage and display the instantaneous and cumulative amounts of material. Mainly used when no upper control is required.
B automatic, the instrument box switch to the linkage position, the upper computer control the start and stop of the belt, dynamic display of the amount of material, belt running status, a variety of alarm instructions, the amount of ingredients by the host computer in accordance with the process requirements Setting, can collect and process the weighing signal and switch status from each batching control circuit, realize the whole system of belt weigher feeding, weighing detection, material quantity adjustment, automatic control of selecting and switching the bunker and other ingredients process . At this point, the on-site manual control system does not work and is completely operated through the central control room.
3, start and stop the automatic operation system
Four ways: sequence start, sequence stop, emergency stop, simultaneous start
B sequence start: used for the system's initial startup or system restart after the sequence is stopped. The sequence start function can control the feeding equipment participating in the batching to start at a certain time interval according to the running direction of the belt to ensure that the material head can be aligned.
B. Stopping in sequence: It is used in occasions where it is desired to stop for a long time. This ensures that the materials on the conveyor belt are transported cleanly, the belt is in the material state, and the tail alignment can be ensured.
B. Emergency stop: For emergency situations where all equipment involved in the batching stops immediately.
B is started at the same time: for restart after an emergency stop, it can make the system run down from the last “breakpoint†as if nothing had happened.
Note: It is not possible to click any of these four buttons in a random order and must be operated as required.
4, the amount of material control
B When a certain amount of material required to determine the ratio, as a set value into the host computer, the network transmitted to the weighing instrument. The material falls on the weighing belt and its weight is detected by the load cell, and the feedback voltage signal (0-30mV) of the material flow (measurement value) is obtained to the weighing control instrument and calculated to become the PV current value, and then output by the PID operation. The ~20mA control signal is sent to the frequency converter to change its U/F output value, thereby changing the belt speed to control the amount of material and achieve automatic batching.
B material ratio control: The system feeding task comes from the upper computer's proportioning input and calculation to control, that is, various raw materials, process parameters input into the computer, the computer directly to each material to set and match the ratio of coordination.
B automatic dumping control: the same material is installed in several silos (such as concentrate powder), only part of silo feeding is used in the production, and it is required to be in a feeding silo (No material, blocking material, mechanical failure, etc.), the control system automatically starts a silo feeding system that satisfies the conditions and does not participate in the batching according to the program setting.
B. Automatic adjustment of the fuel flow value: When the equipment is shut down, since the total amount of concentrate powder decreases one by one with the silo, the program automatically gradually reduces the amount of fuel to be discharged to ensure that the original ratio does not change.
Fourth, system equipment selection
1, network system selection
Ø Upper IPC: Advantech IPC610 P4 17 color display,
C CPU: P42.8G
C memory: 256M
C hard disk: 80G
CCD-ROM: SONY DVD
Ø PLC system: CPU uses Siemens CPU315-2DP. Has the following features:
C has a larger capacity of working memory that can be used for a large number of I/O configurations. Two communication ports can be used for MPI multipoint communication and Profibus-DP distributed communication.
C has a maximum of 187.5 kbit/s data transmission capability, word operation time <1uS, working memory 128K bytes.
C programming software uses STEP7.V5.3, has rich programming instructions and structural modules, and powerful networking capabilities.
C has extended communication capabilities, with up to 32 expansion modules, each expansion unit 8 modules, that is, in addition to the main frame, can be extended 3 racks.
Ø Software settings: The operating system selects Windows2000 Professional SP2, the upper computer runs Siemens WINCCV6.0 configuration software, and the PLC programming software selects Siemens STEP 7 V5.3.
Ø Configuration software function:
Realize the system configuration control and system configuration interface. During the operation, the host computer completes the system man-machine dialogue, monitoring interface display, alarm processing and display, production data processing and report output.
2, ingredients are selected
The batching scale integrates mechanical, electrical, and instrumentation and is the ideal equipment for continuous conveying and metering of bulk materials. According to the on-site requirements, the use of dynamic, automatic, linkage control. It is a necessary equipment in the production process of sintering, coking, raw materials, and cement ingredients. According to the process requirements, choose Jiangsu Libra LB-PP-P series belt weigher.
Ø composition
It consists of a weighing bridge, speed sensor and integrator.
Ø principle
A weighing bridge equipped with a load cell, mounted on a longitudinal beam of the conveyor, weighs the weighed rollers supported by the bridge, detects the weight of the material on the belt, and generates an electrical output signal proportional to the belt load. The speed sensor is directly connected to the driven roller or the large diameter roller and provides a series of pulses. Each pulse represents a belt movement unit. The frequency of the pulse is proportional to the belt speed. The integrator receives the output from the load sensor and speed sensor. The signal, electronically multiplied by the belt movement and the belt load, and further processed the total weight of the material passing through the conveyor, converting it into the selected engineering unit, and at the same time generating an instantaneous flow value through the calculation of the time. Cumulative total and instantaneous flow are displayed on the display.
Ø Structural features
C Weighing Bridge adopts 16# channel steel for integral welding and deformation resistance;
C uses an apron skirt belt to effectively prevent scattering;
C rack tail wheel adopts rubber covered roller;
C uses advanced technology from the United States - rubber shaft support, reliable, maintenance-free;
C has a perfect inside and outside the cleaner to ensure that the belt is clean;
C plus current output interface, can output 4-20 mA current proportional to flow;
C Communication interface optional: standard RS485, Modbus, Profibus interface.
Ø Technical Specifications
C Weighing range: 1～6000t/h
C belt conveyor inclination: ≤18 degrees
C belt speed: 0.1 ~ 4m/s
C belt width: 300～2000mm
3, field instrument
The field instrument receives the weighing sensor and speed sensor signal directly, and then it processes and connects the result with the S7-300 device via the Profibus and I/O interfaces. The instrument can be mounted on the wall, or it can be installed on the spot next to the weighing equipment, which is easy to operate and has strong anti-interference ability.
Ø Features
C die-cast aluminum alloy shell, dust, anti-static, anti-interference ability;
C dual-line Chinese, four-line English backlight LCD display;
C hardware circuit software, reduce solder joints, improve the long-term stability of the instrument;
C five-key operation, easy to learn;
C has intelligent PID adjustment function;
C provides Modbus, Profibus, CAN and other communications;
C. The control method is diversified. It can be used in constant-speed batching, speed-adjusting batching, simultaneous adjustment of batching, and double-speed speeding and batching.
C analog, digital input and output;
C10V sensor for bridge voltage + millivolt input + current input (weight) + switch + control + weight output + flow output.
Ø Technical Specifications
C precision: Class III
C linearity: ± 0.003%
C temperature: -30°C-+55°C
C humidity: <90%
C power supply: AC220V -15%~+10% 50HZ±2%
4, inverter
The frequency converter selects Schneider ATV71 series frequency converter
Ø Excellent performance
C up to 220% over torque.
C asynchronous motors have sensor or sensorless flux vector control.
C online automatic adjustment (FVC).
C speed or torque control.
C output frequency up to 1000 Hz.
C sensorless motor control.
Ø Extensible capabilities
C basic equipment with rich features: application functions, input/output, communication networks,
C These can be further extended by:
C input/output expansion card.
C encoder interface card.
C communication card.
C built-in programmable controller (Controller Inside).