Increased steel production with optimized cooling

Through the advanced management of a number of cold ramps in SSAB's broadband plant in Borlänge, Optimation could help the steelworks increase their capacity. At the same time, large amounts of electricity were saved.

Steel production is an energy-intensive activity. You have to both heat and cool, and both parts draw large amounts of electricity. It is all about optimizing all parts of the process, and for Optimation's part, it was about making sure that the showers that cool the steel bands do not use more water than necessary. Pumps are powered by electricity, and previously they used unnecessarily amounts of energy at SSAB. The requirement for the project was to reach a margin of five percent with a short turnaround time.

"The challenge for us at Optimation was to create a control that could quickly get the right flow in the showers," says Johan Simonsson, Project Manager at Optimation. "Today, the amount of cooling water applied to the belt is calculated by the parent control system. With this control we have been able to reduce the circulation of water, thereby reducing energy consumption."

Johan Simonsson admits that it was believed that the assignment was relatively simple, given the experience gained by Optimation after a number of years with many projects in the process industry.

"We set up a simulator and looked theoretically at the task. After a while, we realized that the project was far more complicated than we had imagined before we started. There were long and deep discussions both at Optimation and in collaboration with SSAB."

SSAB had addressed the problem on its own before deciding to hire a third-party consultant with control system expertise. They therefore much to contribute with regard to proposals and the requirements that the process posed.

"SSAB manufactures steel with different recipes, which alternate in the broadband plant and which may require different handling. This requires all systems to be able to change quickly. When the new shower system was in place, SSAB could therefore increase the pace of its production by shortening the distance between different steel substances sent through the broadband plant."

The process control that Optimation brought forward is of the type of physical feedforward. This type of control is fast, but it requires an accurate and reliable model to provide the desired function. In SSAB's project it was important that the control was fast, and the Optimation model proved to work well in terms of speed and optimization of water flow. Since the new controls have been introduced into operation, energy consumption has been reduced by about 60 percent, while the steel producer also has increased production capacity.

"SSAB is very pleased with the results of the project, which was very rewarding to the contributors on both sides," said Johan Simonsson. "SSAB had a lot to add in the discussions and they really brought the project forward. At the same time, Optimation and the simulator we have built up and used throughout the project enabled us to try out different strategies to see what effect they could have."

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