As part of a plant-wide energy saving programme at its Strip Products mill in Port Talbot, South Wales, Corus has installed 24 ABB drives, ranging from 140 to 400kW, to control the strip mill cooling water circulation pumps and coke oven dust extraction fans. The total cost of the drives amounted to some £1 million; the whole project, including pumps, cabling and so on, came in at around £2.5 million. It was back in July 2006, when Guy Simms, leader of the energy optimisation team at the Port Talbot site, started looking into possible energy savings that could be made at the plant. The order for the drives was placed in the following December and installation commenced during the second quarter of this year. Mr Simms sets the scene on the project:
“The pump and fan motors were clearly oversized and running longer hours than necessary. Much of the equipment on the site was installed during the sixties, seventies and early eighties. At the time, it was common practice to oversize equipment by as much as 50%, to make sure it was sufficiently robust. In many ways this was a successful policy – after all, it has lasted all these years. But with the ABB drives we are now installing, we can fine-tune the applications to a degree that just wasn’t possible in those days.”
While the applications have varying demand, hitherto, the pumps and fans have been running continuously at full speed. Running to demand will not only reduce energy costs but also save water and improve control, particularly of the cold mill, which could potentially provide a bonus in terms of a better product quality.
Low voltage drives are used as they have a smaller footprint compared with their medium voltage counterparts. To achieve this, a transformer is interposed in one of the MV network feeders, reducing the voltage from 3.3kV to the 690V required by the LV drives. ABB happened to be chosen by the Port Talbot engineering team, as there is already a large amount of ABB equipment installed on site, which has met all performance expectations. Moreover, standardising on equipment from one manufacturer reduces training needs and makes maintenance easier.
The Corus site at Port Talbot in Wales is one of the biggest steel-making plants in the UK with an annual output of five million tonnes. Energy is Corus’ second highest cost after raw materials. The costs and revenues of the business are fairly fixed, so high productivity is crucial to stay competitive.
“Using drives to improve energy performance is not just a matter of payback, it is also a modification with low risk,” says Mr Simms. “We can’t afford production stoppages. If a drive installation doesn’t work out, the worst that can happen is that we have to turn up the speed to 100% again. An alternative approach could be to install a new and smaller pump, but then we would also need new pipes and a new bed-plate. And once built, we would be stuck with this configuration. We prefer just to add drives to existing applications that have proven their reliability over the years.”