Tata Steel checks oxygen costs at Scunthorpe plant
10 Aug 2011
Scunthorpe, UK – Tata Steel’s Scunthorpe steel plant produces carbon steel by the basic oxygen method. The existing pressurised oxygen plant at Scunthorpe produced high pressure oxygen at 42bar for steel production, whereas the three operating blast furnaces only require an 11bar supply.
As producing oxygen at 42bar and then reducing it to 11bar was not cost-effective, Tata Steel, in partnership with BOC, built a new medium-pressure oxygen plant on the site, together with a 4.5km pipeline to serve the three blast furnaces. Each furnace can take up to 20,000 m3 per hour of oxygen to enrich its air supply at up to 11% by volume.
The three operating blast furnaces, known as Queen Bess, Queen Victoria and Queen Anne, have an individual control system, based on ABB Advant, ABB 800xA and MasterView respectively. These control systems were installed progressively over the lifetime of the furnaces as each was shutdown for maintenance. Queen Bess and Queen Victoria use Master AC450 controllers and Queen Anne has a mixture of AC450 and Masterpiece.
“Each blast furnace already had an ABB AC450 controller,” said Gopal Chopra, ABB project manager. “To allow the furnaces to use the medium pressure oxygen supply, we upgraded/expanded the controllers with new hardware and software and linked them by a Modbus serial link to a PLC, which collects data about the operation of the furnaces and provides information management and reports for all three. We also installed ABB S800 I/O, for the hardwired signals for each furnace.”
The three separate control systems allow the furnaces to work independently on different production cycles. The new medium pressure pipeline feeds the blast furnaces via a three way valve station. Control of the oxygen flow to each furnace is a complex interplay between the needs of the three units, with each furnace needing to react to the condition and oxygen demand of its counterparts. Both pressure line control and flow control are performed by the ABB controllers.
Developing the system threw up a number of challenges. To develop the software, ABB made use of its software specialists in India who have experience of control systems for the metals industries. Chopra says: “We found during testing on site that some of the EEPROMS needed changing as the new controller was not compatible with the existing system hardware. We have a policy of dealing with any such problems straight way and the customer was able to see that we addressed the issue promptly.”
“The result is a very good control system that allows us to make use of a lower cost oxygen supply route. Overall, the project has been a big success.” said Ian Render, project engineer with Tata Steel.
