Creative Industrial Recycling

Creative Industrial RecyclingMost—if not all—manufacturing produces waste. Having this waste disposed of is costly both in time and money. The steel industry is no exception. Steel mills produce several byproducts or “waste streams.” These include slags, mill scale, dust, and furnace scraps to name a few. All of these byproducts can be repurposed if time and effort is put into finding the end users. This is where companies like come into action.

Slags have long been used for simple aggregates, and sometimes—if the iron content is high enough—iron removal itself. Several years ago when China entered the world steel market, prices for raw materials skyrocketed making the products difficult to acquire. In order to take advantage of this industry surge, processes were developed to “scalp” the raw iron from the waste streams. Now that the market has dropped considerably, these materials can revert to their standard uses. For instance, many roads in the U.S. and abroad have been made with iron slag as a base layer. With millions of tons produced annually there is an abundance of this economical resource available.

Another steel mill byproduct is mill scale. If you’ve ever watched an educational program about the steel production industry, mill scale is the flaky material that can be seen forming on the red-hot, new steel. Mill scale is basically iron oxide and consists primarily of ferric oxide. The color is bluish-black in appearance. Scale is generally less than one millimeter thick. It is formed on the outer surfaces of plates, sheets or billets (blocks) during production. It is also formed when these new steel products are sold to re-rolling facilities. The rolling of reheated, red-hot iron again forms more mill scale. The cycle is ongoing.

Makers of new steel and rolling mills consider mill scale a nuisance. The steel cannot be painted or coated until the mill scale is removed as the paint will quickly peel off. Removal of mill scale is, therefore, a necessary evil in the production of steel products. There are three main processes used by steel mills to remove mill scale. The first, pickling, is a process in which an acid is applied to the steel to remove the scale. Flame removal is the second technique in which hot flames are applied to the steel product in conjunction with a mechanical scraping device. The third process is abrasive blasting which is similar to standard sandblasting.

Once the mill scale is removed it is collected, heaped, and offered for sale as a byproduct. It is a valuable waste stream and is in demand in other industries. Applications range from pigments for paints, iron units added to cement, counter weights, remelting for new steel and many other industrial uses.

The same market changes affected mill scale when the China steel boom occurred in the early 2000s. Prices increased considerably and mill scale became more difficult to acquire. The market has now stabilized and prices have come down making mill scale a prime material option for other non-steel-making industries.

Other steel mill byproducts such as dust and furnace scraps generally find their way to end users through the ongoing efforts of the steel producers. Overall, the industry’s goal is to keep these materials out of landfills. This in turn helps improve the companies’ bottom lines. The industry’s mindset can be considered not only economically focused, but perhaps in some respects green as well.

Whatever the motivations, it opens up opportunities for smaller businesses like which make an entire subindustry of recycling byproducts. Everything from logistics to laboratory services means added jobs and money spent locally. If more industries practiced waste stream management similar to steel producers, the impact on the American economy as well as the environment would be staggering.

Richard Johnson

Mill Scale and Byproduct Recycling