Siemens makes slag management breakthrough

Mar 25, 2013 | 07:00 PM | Myra Pinkham

Tags  Siemens AG, electric-arc furnace, slag management, slag, Simelt FSM, Thomas Matschullat,

Managing the foamy slag layer is one of the trickier aspects of electric-arc furnace (EF) steelmaking. Achieving an optimal foaming slag layer--which is a mixture of liquid, solid and gas particles formed by injecting slag with carbon monoxide--is critical to promoting low thermal conductivity, removing undesirable elements from the molten steel, shielding the electric arcs and protecting the furnace’s fireproof lining.

“It is very hard to determine whether you have too much or too little foaming slag, what the quality of the slag is and whether it is distributed uniformly in the (EF),” said Thomas Matschullat, head of metals technologies at Munich-based Siemens AG. A lot of energy can be lost when too much carbon is injected into a slag and the foaming slag layer is too high, he said. On the other hand, if there isn’t enough carbon and the foaming slag layer is too thin, it might not be adequate to protect the furnace wall from the high temperatures of the furnace’s arc.

Siemens has developed a fully automated foaming slag management process based on structure-borne sound to take the guesswork out of maintaining the optimal foaming slag layer in the EF. In commercial use since 2008, Siemens’ Simelt FSM (foaming slag manager) is already being used by two European steelmakers and is going through final testing before being formally implemented by a major U.S. EF steelmaker.

Matschullat said EF steelmakers currently rely on the instincts of a good furnace operator, one who has a good feel of the steelmaking process, to determine whether the foamy slag layer is optimum. These technicians typically use predefined operating diagrams or manually inject carbon fines and oxygen but are not able to directly observe how these manual injections are influencing the height and distribution of the foaming slag. ....

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