1 Overview

There are four bins in Tongshankou copper ore dressing workshop, and the ore is transported to the bins by conveyor belts in parallel, and the ore in the bins is crushed by the crusher into uniform particle size and then sent out. The discharging speed of the four bins depends on the vibrating speed of the vibrating screen in each bin. Each screen is driven by a frequency converter. At this stage, the discharging speed of the four bins is manually adjusted by the workshop operator on the operating table near the bins using an external potentiometer, which is a less accurate control method. Moreover, due to the long distance between the silo and the ore silo, the operator can not detect the amount of material level in the silo, and can only assess the experience and the instructions of the staff of the distant ore silo to manually adjust. Often cause the material level in the silo is too high or too low: when the material level is too high, the crusher can't finish crushing the ore in the silo in time, which will further cause a pile of material; when the material level is too low, the crusher idles, which affects the productivity of the beneficiation operation. Therefore, the beneficiation feeder is in urgent need of automatic control mode for transformation.

2 Feeder hardware program

According to the needs of users, in order to effectively reduce energy consumption, improve the productivity of mineral processing operations, real-time automatic adjustment of the amount of feed to ensure the normal and safe operation of the production line, the design adopts advanced PLC and touch screen control technology to transform the existing old control mode.

2.1 System hardware structure

Feeding system main control object for the four bins of vibrating screen, conveyor belt and crusher, we design using PLC and inverter as the control core, and supplemented by the field operation box, touch screen for automatic control of the system.

For this automatic batching machine mainly includes the following parts:

PLC: batching system control core. Adopting Siemens S7-200 series PLC, it mainly realizes the speed adjustment of bin discharging of transmission system, speed adjustment of transmission belt, material level detection of ore in the silo, speed adjustment of crusher, manual/automatic switching of the system, local/remote switching, etc. It also carries out closed-loop control of the system transmission belt and bin discharging speed and material level.

Frequency converter: Frequency converter CV1-CV4 control the vibration speed of vibrating screen of 4 bins; Frequency converter CV5 control the running speed of transfer belt; CV6 control the running speed of crusher. Among them: CV1 and CV2 adopt Schneider AVT71 series frequency converter; CV3 and CV4 adopt Dr. CVF-G2/P3 series frequency converter; CV5 and CV6 adopt Schneider AVT71 series frequency converter, which is a new generation of high-performance products of Schneider, with internal PID closed-loop control function and ATEX safety function, and it can realize the internal auto-tuning or external manual adjustment safely. internal auto-tuning or external manually adjusted control mode of fast switching. The six inverters can continuously adjust the discharging speed of the silo, the feeding speed of the conveyor belt and the crushing speed of the crusher in real time.

Touch screen: Provides a man-machine interface for the system. Adopting PRO-FACE4300 series touch screen, it can monitor the production data and equipment status of the system in real time.

Control box: A control box is configured in the electrical room of the screening workshop. Receiving the control signal from PLC in the main control room, the control box is equipped with a simple relay circuit, which can change the relay state through PLC control, thus realizing the switching of remote/local working mode of the frequency converter. And through the control box to the inverter internal control terminals for transition, so as not to change the original inverter cabinet wiring.

2.2 System network structure

As the workshop uses different models and manufacturers of inverters, the communication protocol is inconsistent, in order to realize the automatic control of the screening workshop inverter, we designed to use serial communication combined with hard-wired coexistence to realize the direct communication of the main equipment.

Among them:

(1) Mod-bus serial communication is used between PLC and Schneider ATV71 inverter;

(2) RS485 serial port is used between PLC and Dr. inverter;

(3) Hard-wired communication between PLC and control box;

(4) RS485 communication between PLC and touch screen;

3 Beneficiation conveying automatic feeder software program

Feeding system mainly includes manual and automatic control mode, automatic control mode, can be divided into local/remote control mode. Both control methods can be realized through the PLC internal PID closed-loop control model to automatically adjust the operating state of the frequency converter according to the amount of stone in the silo, and can also be set through the touch screen to adjust the operating state of the frequency converter remotely by manpower, and at the same time, it can also be locally controlled through the control box.

3.1 PLC feeder

3.1.1 System control mode, manual/automatic

(1) Manual mode: can realize the operator manual manually given;

(2) automatic mode: can be then by the PLC according to the material level meter feedback to control the frequency fast and slow.

3.1.2 Manual control mode, local/remote

(1) Local mode: local operation of inverter cabinet can be realized;

(2) Remote mode: touch screen remote operation can be realized;

3.1.3 Automatic control mode, first of all, to detect whether the radar material level meter is normal, if not normal then automatically cut back to manual.

3.1.4 In the automatic control mode, it is necessary to set 3 zones of material level in the silo in advance: low material level zone, middle material level zone and high material level zone, and different control strategies are adopted for different material level zones:

(1) Low material level zone: frequency converter CV1-CV4 control the vibration acceleration of the silo, quickly let the ore in the silo to reach the set material level;

(2) Medium material level zone: maintain the vibration speed of frequency converter CV1-CV4 and keep adding material to make the mineral material in the ore bin close to the high material level;

(3) High material level zone: control inverter CV1-CV4 to decelerate to a fixed speed;

(4) Zoning the bin can avoid frequent adjustment of the frequency converter and achieve the purpose of self-adaptation. And you can manually set the material level percentage of low material level zone, middle material level zone and high material level zone through the touch screen;

3.1.5 Belt motor control: the speed of belt motor frequency converter CV6 can be adjusted in real time according to the requirement of material feeding quantity.

3.1.6 Crusher control: the crusher running speed can be adjusted in real time according to the amount of material level in the ore bin and combined with the speed of the belt conveyor and the speed of material discharging from the bin.

3.1.7 You can manually adjust several of them to the maximum frequency through the touch screen, and then automatically control several of them. Avoid frequent adjustment of all 4 sets of frequency conversion.

3.1.8 The six inverters can either be linked or work separately.

If in the process of operation, the material level meter detects the value up to the maximum, or the minimum, then, it is considered abnormal, immediately stops working automatically, and displays the fault, and alarm.

3.2 Touch screen monitoring system

This feeding system adopts Pro-FaceM4300 series touch screen to monitor the production data of the whole system, and the main functions are as follows:

3.2.1 Main Screen

After the system is running, the main screen is the monitoring screen, which can manually adjust the frequency of a single inverter, and the left side of the screen is the bin feedback animation, which provides real-time feedback on the internal capacity of the bin.

(1) Local/remote: it can realize local operation of the inverter cabinet and remote operation with the touch screen.

(2) Manual / automatic: remote touch screen can be realized manually given, and according to the capacity of the silo automatically adjust the frequency converter.

3.2.2 Parameter setting screen

(1) The lower limit frequency of each frequency converter can be set individually, and both manual/automatic are valid.

(2) The upper/lower limit of material level can be set to realize automatic control. (Automatic valid)

(3) Variable frequency adjustment amount can be set, in automatic control, when the bin feedback into the bin upper limit/lower limit interval, the given value of the frequency conversion is the frequency conversion adjustment amount. (Automatic effective, 4 sets of inverter effective)

4 Conclusion

After the completion of the transformation, the 4 silo vibrating screens, belt conveyor motors and crushers can work well coordinated under the control of this system, feeding the ore from the 4 silos continuously into the silo and crushing them evenly. The staff can also adjust the feeding volume and crusher working frequency in real time on site or in the control room, the system productivity has been greatly improved and the energy consumption has been reduced.