Bethlehem Develops
Wastewater Process
Bethlehem Steel Corporation
For Immediate Release
BETHLEHEM, Pa., January 31, 2000 - Environmental engineers at Bethlehem Steel Corporation have developed a unique method for separating metallic waste from mill wastewaters. The patented process utilizes common split-ring metal washers, which are charged magnetically, to attract and hold the oil-coated mill scale while a high-pressure water and air spray separates the scale from the ring washers.
In the rolling of steel products, huge amounts of water are used to cool the mill rolls as they shape the hot metal. The water is collected and recirculated throughout the rolling process, but becomes contaminated with oil-coated mill scale - particles of metal that separate from the hot steel during the rolling process.
If these particles are allowed to stay in the recirculating water, they can eventually damage the surface of the mill rolls or the steel product that is being rolled. Previous filtering methods for removing the mill scale were not adequate because the accumulation of oil on the scale would often clog the filters, severely reducing their efficiency.
The Bethlehem system overcomes these shortfalls by using the somewhat unconventional matrix of metal washers and magnetics inside a filtering apparatus through which the mill water is circulated. As the water enters the apparatus, it passes through the magnetized washers which attract the metal scale. A high-pressure stream of air and water is then injected into the apparatus, separating the oily metal. After treatment, the de-oiled scale can be either filter-pressed for appropriate disposal or re-used as sinter plant feed.
While the Bethlehem process was designed specifically to treat recirculated cooling water from a hot strip rolling mill, the filter apparatus can be adapted to a variety of processing or manufacturing operations where it is necessary to separate metal waste particles from wastewater.
Named as co-inventors of the process are Stewart Herman, Director Environmental Technical Programs in Bethlehem's Safety, Health and Environmental Department, Bethlehem. Pa., and Robert Greenawalt of Ottsville, Pa., and Richard W. Faupel of Sebring, Fla.