Roll-Press Briquetters Help Steelmakers End Landfilling and Cut Scrap Costs

Background:

Like other steelmakers, National Recovery Systems (NRS) faced tightening EPA regulations and landfilling restrictions combined with rising scrap costs.

While mill wastes such as dust, slag and scale have long been recovered by sintering, Basic Oxygen Furnace (BOF) sludge presented a difficult challenge to turn into a reusable form.

Challenge:

Steve Milter, President of National Recovery Systems, explained that “BOF sludge is rich in iron, carbon and other recoverable elements, and represents the largest waste stream from a BOF operation. It’s the biggest part of a steelmaker’s landfill problem, but it also gives us the biggest potential for recovery of valuable materials.”

But unfortunately, even after thickening to 85 percent solids by centrifuge dewatering followed by air drying, sludge remains too wet to allow charging into a BOF, which typically left landfill as the only alternative.

Milter knew that briquetting was the key to recycling. “When sludge is dried enough to be charged into a BOF, it becomes a fine, dusty powder that would be blown away by updrafts long before it reached the molten steel.”

Solution:

K.R. KOMAREK Inc. designed and built roll briquetters to fit NRS’ specifications. The machines use two horizontally-opposed, counter-rotating rolls with half-briquette pockets machined on their circumference faces. Both rolls are indexed so the pockets on opposing rolls match as the rolls turn, closing to form whole briquette-shaped cavities as both halves pass through the roll centerline.

Due to the highly abrasive nature of iron oxide wastes, the briquette rolls are also made of a proprietary wear-resistant alloy developed by KOMAREK. The rolls consist of 18 separate segments, which are independently clamped onto the rolls. This design greatly facilitates roll changes when the pockets become worn out. Milter explains that replacing all the pocket segments takes only about eight hours, so lost production time is easily absorbed.

Results:

The use of briquetting for conservation and recovery reduces outlays for scrap and avoids costs associated with landfilling the sludge and other oxides – which can easily costs tens of millions of dollars per year when factoring in costs to solidify and transport to remote locations explained Milter.