Slag is comprised primarily of silicates and oxides, as well as elements such as phosphorus and manganese and is a waste product produced when refining steel and pig iron. Refined steel is economical, malleable, strong and easy to shape and form, compared to cast iron, for instance, which is strong but brittle and difficult to shape. Steel has been produced since ancient times, but never in large quantities due to the difficulty of efficient slag removal. More slag = less quality steel.
A significant factor in slag removal is efficient use of reagent within the hot metal in the ladle to encourage more sulfur to float to the surface as slag. Better mixing of reagent with hot metal is the key to efficient reactions and more cost -effective steel purification, but the conundrum is this: how to achieve better mixing using existing mill equipment?
Steel and Iron mills in the Pittsburgh region and the US have to compete globally with mills in countries with cheap labor and thus they have a delicate economic balancing act between paying for capital expenditures and producing the purest iron and steel products by removing slag. Mills are unwilling to invest in technology without a proven cost-benefit that can be immediately felt.
The photo shows a portion of a patented high effective rotary lance drive developed in the Cranberry Township- Butler area by the inventor. While an effective solution to the mixing problem, it requires significant costly upgrades to existing mill equipment to support the rotary components. For a new mill, this is a fantastic solution. For an existing mill however, nobody wants the capital outlay and installation downtime related to replacing equipment.
US Patent No. 10,240,218 B2 issued March 26, 2019 details a coaxial (reagent) material lance with a built in stirring system that uses arrays of gas ports to create patterns of bubble turbulence along the length of the lance. The gas bubbles intercept reagent, breaking up the reagent and forcing it into the hot metal, effectively increasing the surface area of reagent in contact with the hot metal. More sulfur is removed and in less time, and with less reagent.
Even better, the coaxial lance is completely compatible with existing lance drives, requiring only a gas supply that is readily available and easily installed. No major modifications to existing equipment are necessary, downtime is minimal.
Purifying steel or iron creates gas, and the prevailing concern using gas within the ladle has been unwanted surface splashing and loss of metal as the bubbles break at the metal surface. The coaxial lance controls the volume, flow rate, size and array of gas bubbles, negating splashing. The relatively small bubble size effectively mixes reagent into the hot metal. Slag rises to the surface, not giant bubbles, and steel purification is more efficient, using less reagent and less time. The EPPS Coaxial lance is a creative solution to an age old problem in a field where steelmakers believed there were no more invention ideas that could improve efficiency.
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