Programmable Logic Controller in Mineral

Question: Discucss about the Programmable Logic Controller in Mineral Processing. Answer: Introduction With advent in technology the automation processes have also changed and developed so far. Automation processes are used to control the various systems and related technologies in an industry so as to provide better and efficient mechanism in respect to time and cost. These kinds of automation techniques introduce PLC that is Programmable Logic Controller in to the system. This report deals with a PLC system and its working in mineral processing industry throwing light on its mechanism along with its sensors acting as the inputs while the valves are being used as output of the system. To provide a wider detail and understanding for the topic the report has been sectioned properly. The report has been divided into parts including stages in Mineral processing, PLC in Automation process, PLC Architecture and its working. Automation process There are various control system implemented in automation such as HMI controller, DCS control system, PC control System and PLC control System. The report focuses on the PLC system in mineral processing. Programmable Logic Controller A PLC or Programmable Logic controller can be called a digital computer working for the automation of the electromechanical processes. These are much different from the general computer as they are specifically designed for the various inputs and outputs, having high resistance to the electrical noise, impacts and vibrations (Kiran 2013). Basically, the system reads its input and reverts back by putting the output section on or off. The programs on basis of which the automation process goes on is written and saved up in the backup or non-volatile memory. The process has to present the results based on the inputs in accordance to the time to avoid unintended operation. Thus it can be called an absolute real-time system. It has been considered so important because it is an intelligent piece of software which can take place of the numerous relays at once (Wang and Wu 2016). The PLCs are designed and programmed very smartly to deal with the machines precisely and efficiently without any chances of miscalculations avoiding any high erroneous cost. The PLC is advantageous for complex networking capabilities and motion control. Mineral Processing Mineral processing is the separation process of vital minerals from their ores. These processes go through several stages to achieve the desired output. The steps involve size reduction, size control, enrichment, upgrading and handling (Lessard, de Bakker and McHugh 2014). The several stages namely are comminution, sizing, concentration, gravity concentration, froth floatation, electrostatic separation, magnetic separation and automated ore sorting. The whole process is considered along with its economic feasibility. The flow chart can be depicted as follow for the following processes: Fig 1: Mineral Processing Source: (Created by Author) Comminution: it is the process for reducing the larger solid materials into average to small size particles by crushing or grinding. This is done so as to easily extract the minerals from the ores with clean particles. Generally three types of procedures is used that is impact, compression and attrition. Sizing: it is a general process of separation of particles according to its sizes. This is done by passing the particles from various screens such as wedge wire screens, grizzles, multi-deck screens and many more. Several parameters are considered for using the right sizing method like aperture size, presences of other materials, shape and orientation. Concentration: it can be described as amount of moles of solute in a measured volume of solution. This is used to increase the concentration of any required mineral depending on its physicals and chemical properties. Gravity concentration: It is a separation process to extract the minerals from its mixture on the basis of their specific gravity. This is preceded with the classification of particle size, weight and shape. Froth-floatation: this works with the theory of surface chemistry of particles which differs from particle to particle. The driving theory for this method is change in surface free energy (Paxton 2016). The pulp is introduced with the bubbles which rises up and then collected later from the surface. Electrostatic separation: Two different types of electrostatic separators or electrodynamics separators are used. The charged anode is passed with the stream of particles. The conducting particles are attracted towards the plate pulling away from the streams and get separated this way. Magnetic separation: as the name suggest this process works with help of magnetic field. The particles are passed into magnetic field which experiences the magnetic effect and gets separated accordingly. The process can be run with or without water. The separation takes place in accordance with gradient or the strength of the magnetic field. Automated Ore processing: this process works with help of automated separation method s performed by the sensors (Morkun and Tron 2014). Automated optical sensors exploit particles materialistic properties and perform sorting with respect to that. PLC included in the processing makes the processing more efficient and less time and labor consumption. PLC system Architecture A PLC system has three layered architecture including Environmental model, Software model and hardware model. The software model contains all the application programs. It is constructed as a separate component. Functions or the function blocks are called by the main program saved in the software (Kaluz 2015). The nested functions or function blocks can other blocks too. The calling port has a calling program installed which broadcasts the signals. It checks for the called function by check and trial that is it tries matching the called function with the name of the components connected. Interrupts are also handled by the PLC which is modeled into a separate component. Along with these, timer is also aligned as a separate component. Call port arouses the component with the start of the timer. The layer after this is the abstraction model. Features of a PLC for example interruption handling and the cyclic execution is handled and simulated in this layer (Theorin 2015). For a better functioning of the PLC the third layer comprises of the controlled devices. Sensors are available to collect data from the environment. Interrupt events such as communication interrupt, clock interrupt, alarm interrupt are all modeled like components of the environment. Working of a PLC Three cyclical stages include the working of the PLC. The First stage involves scanning of the signals receiving from the sensors. These signals are stored into the input registers. Through which the instruction are read from the memory and executed (Kufoalor 2014). At last after this, the output registers stores the data for the actuators. PLC acts as the most important component of this process. The whole process is controlled with help of its programmed memory. Ladder logic is used here to control several machineries and outputs involved. It provides the whole process a smooth flow and low accident rate at higher speed and accuracy. The PLC is a form of solid state device which makes it a powerful controller. The PLC works more efficiently with the Supervisory control and data acquisition (SCADA). This SCADA works on the computer which helps in controlling the PLC (Belekar and Desai 2014). The first aspect of this process is HMI that Human Machine Interface software. It acts like a control panel which helps in operating the PLC through computers. It ahs numeric keys and screen displaying the text where an operator can on or off from the interface itself. Inputs The Input module takes up the signals given through sensors. This includes float switch, start/ stop switch, proximity sensors, position sensors, conveyer switches and others. Pushing of the start button or clicking on the run in the interface allows the machines to start on. The relay gets engaged and it further energizes the switch to put the motors of the machineries on. These kinds of machineries are bulky and run on very high voltage. Exposure of any worker to such a high voltage may be very dangerous and prove fatal if working manually with the switches (Belekar 2014). The controller locks the respective gates of the machineries with the electromagnets and does not let any interventions until unless the stop button is pressed which de-energizes the lock. Controller Controller or the central processing unit is a simple processor here which takes the set of program as input and controls the entire process. It solves the program step by step and updates the final output status (Bolton 2015). Programmer Programmer or operator uses this programmer device to update or edit the controller working process. This can be a personal computer, handheld unit or computer programming terminal. This gives access in customizing the process in accordance to the requirements (Biallas 2014). Output Taking the on/off message as the input the processor starts solving the ladder logic program in accordance to the given information. The controller signals are converted into the output signals by this module (Dixit 2015). The output from the PLC controls synchronous motor for the running of the rotator conveyer with the ores or crushed minerals on it in the separation process. Functioning of the PLC The system is manually fed from the computers for the inputs which are passed to the programming port. The system automatically takes in the input with the program already saved in the programming console (Hoaglund and Birkenfeld 2014). Sometimes the input is also provided through hand-held terminals. This terminal takes the data and passes it to the programming port. The processors process the whole input and program. The ladder logic is run at this time and passes electrical instructions to the machineries to start or stop accordingly (Dixit 2015). After the time span for the process is over the machine gets the next step update. The PLC may ask the system to stop the process or it may continue again. The relay output, triac output and transistor that are received are only manipulated as the mechanical output. The internal processing in the PLC also contains internal bus, CPU, and User memory (Bolton 2015). The processed data results into output. The output module contains attached contractors, solenoid and alarms. Fig 2: Block Diagram of PLC Source: (Created by the Author) On the basis of the above block diagram one can design the transfer function of the following considering the input flow into the system and the output flow of the system which can be derived with help of Laplace Transform. This can be solved using simple algebraic variables or manipulation of differential equation. Conclusion Complex embedded System has to be verified through the computer-aided verification. The system has to be faithful to the process. It should run accurately with the right measurements. The loops for feedbacks should be taken under consideration for the later processes. PLC architecture and the working described are universal for every PLC system. The source code consistency with the model is ensured through automatic translation. PLCs have better memory and processor power. Management of this system through SCADA saves more time making oit more efficient and effective. References Belekar, S.B., Desai, A.A., Parit, M.H. and Dakre, A., 2014. PLC SCADA based Distribution Monitoring Control. Biallas, S., Kowalewski, S., Stattelmann, S. and Schlich, B., 2014. Efficient handling of states in abstract interpretation of industrial programmable logic controller code.IFAC Proceedings Volumes,47(2), pp.400-405. Bolton, W., 2015.Programmable logic controllers. Newnes. Dixit, A., Mendiratta, R., Choudhary, T. and Kumari, N., 2015. Review Paper on PLC Its Application In Automation Plants. Gavali, A. B., S. A. Patil, and A. R. Koli. "Technology-Based Learning system in Programmable Logic Controller Education." 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