Innovative Technology Offerings

Mill Scale DeOiling Capabilities

Mill Scale is produced in Hot Rolling operations in the iron and steel industry, in which scale is removed from the surface of hot steel through spray water and contact with the rolls that effect size reduction. The scale thus removed typically discharges with the water used for contact cooling to a scale pit, where the scale settles out, and the water sans scale is recirculated or discharged. Reuse of mill scale was desirable because of the high iron contact. Very large particles could be directly recycled, but smaller particles required agglomeration in some form for recycle to the blast furnace. Typically this was done using a sinter plant in the past, and is today done more frequently through briquetting. However, the finer fractions of mill scale contain too much oil for recycle to a sinter plant, and are known to cause a blue haze in the air discharge from sintering operations when the oil level is excessive.

Only one mill scale recycling project was successfully implemented, to our knowledge. This was at a mill near Chicago, circa 1990. The proprietary process employed involved the use of surface chemistry modification together with heat and mechanical energy input in an aqueous environment to separate the oil from the mill scale. The processed mill scale was then conveyed to the sinter plant, for recovery of iron units. Oil and oily residues were processed to yield only clean mill scale fines and relatively clean oil. Due to contractual issues, the cleaned oil was conveyed to an oil recycler for recycle to plant operations. The plant operated for over three years, and in that time eliminated an accumulation of mill scale from past years as well as the ongoing production. As the volume of mill scale produced decreased substantially in that time frame, operations were no longer economical at the reduced throughput, and the operation was discontinued.

EnCOSS personnel were in responsible charge of the project from mid-way through the lab/development stage through commissioning, and provided ongoing technical support through the life of the contract. EnCOSS can offer this technology for separation of oil from relatively fine metallic solids such as mill scale.

For more information, contact the EnCOSS office nearest you.