Exxaro’s Grootegeluk coal mine plays a vital role in the South African economy by supplying upgraded coal to Eskom’s Matimba power station, which contributes nearly 4000 MW to a struggling national grid. With the creation of the Medupi power station, the mine has had to virtually double its coal supply to accommodate this new 4800 MW facility. When Medupi is complete, Grootegeluk will be responsible for supplying two power stations that together will meet more than 20% of the country’s electricity needs.
Scope of the project
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 Grootegeluk Medupi Expansion Project (GMEP) 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. Thereafter, cold commissioning, in parallel with the operational facility as well as the systematic hot commissioning and cut-over to full production, took place.
GMEP’s overall goal was to become a comprehensive coal beneficiation facility that, through the monitoring and control of crushers, screening, cyclones, larcodems (large coal dense medium separators) and filters, as well as a complete stock yard management system, would deliver quality coal into Eskom’s Medupi silos.
Exxaro has standardised on Wonderware technology for its coal plants, so it was decided to continue building on this platform since scalability and functionality are two of its hallmarks that met the requirements of this project. Exxaro chose system integrator Control Systems Integration (CSI) for the implementation because of the company’s ten-year successful partnership, during which quality solutions have been implemented into all eleven of Exxaro’s coal facilities, as well as at its headquarters.
Implementation
This was a new site featuring completely automatic and integrated plant operation and control. The system has automatic start/stop procedures and PID loops are used instead of labour-intensive manual operator controllers. Automatic control allows faster start-up times, better plant availability, reduced downtime and improved reporting.
A virtual environment was created on Wonderware’s System Platform to host InTouch (HMI/scada), Historian and MES Performance for nine Application Object Servers (AOSs), 16 InTouch touch panels, 12 InTouch operator stations and four engineering stations though a 200k/100k galaxy repository. At the front end were 20 PLCs servicing over 155 000 combined I/Os. Flow software was 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 250 Mb of data from 50 000 tags daily.
CSI implemented a master controller system which deals with the higher-level logic functions of the plant in respect of sequences, parameters and KPIs. “This effectively provides the plant with double-tier control,” says CSI director Tinus Botes. “Another aspect of the control system is the management of a special brake control procedure for the conveyor that conveys tons of waste back into the pit. This was rather complicated as extensive testing was required to make sure everything worked as it should. An interesting feature was the use of a regenerative VSD drive to generate power from the braking of the inclined conveyor.”
The monitoring of equipment downtime and utilisation in the plant is the responsibility of Wonderware MES (Performance). The detailed downtime reporting available to management helps them optimise operations.
“Apart from its sheer size and complexity, we had a number of memorable challenges during the implementation of this project,” says Botes. “One was interfacing to several different third-party suppliers and the integration of their solutions into the system. Another was the systematic hot-commissioning cutover to full production, per section, while production was in full operation on previously-commissioned sections – this required some very careful scheduling.
“Then 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.”
Customer benefits
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, all of which added up to an uncommon level of implementation excellence.
For more information contact Andre Brits, CSI, +27 (0)12 653 7901, [email protected], www.controlsi.co.za
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