Application of technology reduces engineering, training and support costs in mining

August 29th, 2016, Published in Articles: EE Publishers, Articles: EngineerIT

 

Application of technology is one of the major contributors to mining operations profitability – by introducing major savings in operation, training and supports costs. This concept was recenty illustrated in one of the largest mining growth projects in Southern Africa, with a capital cost of some R10-billion.

Exxaro’s Grootegeluk is the largest coal operation in the world, producing some 33 Mtpa of power station coking and steam coal, powering nearly 9000 MW. On the mining side, the project incorporates cutting edge mining techniques including semi-mobile in-pit crushing systems. On the supervisory side, all the industrial automation and information aspects had to be completed in two years.

The scope of the industrial automation aspect of the mine  included the development of 19 different functional design specifications, assembling 20 PLC panels as well as 192 remote I/O and 80 condition monitoring panels, installing 48 process cameras and associated networks, developing control standards, PLC coding and SCADA configuration, production reporting, full factory acceptance testing, site installation and interfacing to third-party vendor equipment – and cold commissioning in parallel with the operational facility as well as the systematic hot commissioning and cut-over to full production.

Exxaro awarded the system integration contract to Control Systems Integration (CSI) – which had previously standardised on Wonderware technology for its coal plants.  CSI then continued building on this platform since scalability and functionality were two of the hallmarks that met the characteristics of the project.

While the main goal was to increase throughput from 8750 to 14 600 tonnes per hour and supplying the Medupi power station with an average of 14,6 Mtpa, other important requirements were the introduction of a high level of safety and to employ the latest technology. Exxaro’s overall goal was to become a comprehensive coal beneficiation facility that, through the monitoring and control of crushers, screening, cyclones, large coal dense medium separators (larcodems) and filters as well as a complete stock yard management system, would deliver quality coal into Eskom’s Medupi silos.

As this is a new site featuring completely automatic and integrated plant operation, automatic start/stop procedures and PID loops are used instead of labour-intensive manual operator controllers, thereby enabling automatic control for faster start-up times, better plant availability, reduced downtime and improved reporting.

A virtual environment was created on a system platform (based on ArchestrA technology) to host InTouch (HMI/SCADA), Historian and MES Performance for nine application object servers (AOSs), sixteen touch panels, twelve operator stations and four engineering stations though a 200k/100k galaxy repository. At the front end are twenty PLCs servicing over 155 000 combined I/Os. Flow software has been used for the capturing of data and the generation of user-definable reports, while Software Toolbox’s Top Server was used for device communications. Historian captures 250Mb of data from 50 000 tags daily.

According to CSI, the upfront definition of automation standards resulted in uninterrupted delivery of the automation system. The use of Wonderware System Platform’s technology reduced engineering costs but the ultimate main benefit is the lower cost of training and support through the use of common standards and applications.

Figure 1 : The master controller system which deals with the higher-level logic functions of the plant in respect of sequences, parameters and KPIs.

Fig. 1 : The master controller system which deals with the higher-level logic functions of the plant in respect of sequences, parameters and KPIs.

CSI implemented a master controller system which deals with the higher-level logic functions of the plant in respect of sequences, parameters and KPIs (Fig. 1). This effectively provides the plant with double-tier control. Another aspect of the control system is the management of a special brake control procedure (designed by Binder) for the conveyor as it conveys many tons of waste back into the pit . This was rather complicated as extensive testing was required to ensure everything worked as it should – an interesting feature being the use of a regenerative VSD drive to generate power from the braking of the inclined conveyor.

The stockpile management function provided for the exact logging of the location of particular grades of coal in the stockyard as well as what the stackers and reclaimers were doing there before they were commissioned for other tasks. This required an interface between the stockpile management system and the various machines in the yard. The MES system was implemented for monitoring of equipment downtime and utilisation in the plant. The detailed downtime reporting available to management helps to optimise operations.

A project of this size does not happen without some problems and challenges. Apart from its sheer size and complexity, the sytem integrators had a number of challenges during the implementation. One of which was interfacing to several different third-party suppliers and the integration of their solutions into the system. Another was the systematic hot-commissioning cut-over to full production, per section, while production was in full operation on previously-commissioned sections – this required some very careful scheduling. There were the difficulties with new technologies being implemented for the first time such as the control of the regenerative drives on the conveyors, control of the high-power brakes for the inclined conveyors and the new stockyard management system with its interface to the yard machinery. Because this was a lengthy project, it was also necessary to simultaneously incorporate new software upgrades.

This level of automatic control allows for faster start-up times, better plant availability, reduced downtime and improved reporting. Top of the agenda from the start was the definition of standards, thorough system design and detailed factory acceptance testing before moving onto the site. The Grootegeluk project provides and excellent example of how the application of technology can benefit industry.

 

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