Recycling or disposing of Mill scale

A. Dear Ali,

There are several methods of agglomerating mill scale, ore fines or scrap fines. Briquetting or Pelletizing. Coarser material lends itself well to briquetting and finer, dustier material works well for pelletizing.

Briquetting is done on a briquette press consisting of upper and lower rolls with matching cup shape recesses in them (like a small rolling mill). A hopper is attached to the feed side of the rolls and material to be briquetted is placed in the hopper. A vibrator is attached to the hopper to keep the material flowing. Roll pressure and speed will determine the density of the compressed briquettes. Mill scale that has been sitting around for a while will be a bit spongy and should compress well into briquettes.

Pelletizing is done on a pelletizing wheel consisting of an abrasive coated disc with a 4 to 6 inch rim around the outside edge. The pelletizing wheel has speed and angle adjustments and is usually set at about 45 to 55 degrees. A binder such as dry bentonite clay, dry pre-jelled starch or other inexpensive water activated binders are mixed with the fines at .5% to 2% prior to feeding. The dry fines with binder are vibratory fed onto the angled disc at about 10 o'clock, a fine water spray nozzle is positioned at 2 o'clock, the pelletizing wheel turns clockwise. The angle and speed of the wheel need fine adjustment to get the fines to roll into pellets. Playing with feed rates, speed and angle can control the size of the pellets. As the pellets get larger, they roll off the rim at bottom of the wheel.

Better information on these processes may be found on one of the iron or steel making web-sites.

Best regards,

A. A fungi based biodet has the capability to solubilize about 2 kg of mill scale per litre. It can also be recycled once contaminated.

A. I suggest contacting your government agricultural ministry for assistance. This material could possibly be used as an iron-rich soil supplement. Laboratory analyses for metals such as Cr, Cu, Ni, and Zn would be necessary. However, trace amounts may be beneficial in some leached tropical soils. With government approval, you may also want to investigate whether a more soluble form, as by reaction with spent sulfuric acid pickling solution, would be beneficial.

A. More years ago than I care to remember, I worked in a hot strip mill, the mill scale was sent to the blast furnaces for recycling. If you don't have an iron making blast furnace you may want to briquette the mill scale and feed it back into the steel furnaces. Some binders used on ore and scrap fines were pre-jelled starch or sodium silicate in very small percentages.

Good Luck & Best regards,

A. You can export the mill scale to China as the demand is increasing by the day for sinter plants.

A. I came to know that in China mill scale is being recycled by the following process.

They first grind the mill scale to some specific grain size then pass it to magnetic separator and then mix it in mixture with coal powder and some binder then make briquettes using hydraulic press and then these briquettes being used by foundries casting cast iron components in their coke fired cupola furnace called smelting reduction process.

But I've not seen this process live and that's why I'm searching out China where this is practiced.

Can anybody help me in this matter? Because I also want to recycle mill scale in my foundry line.

Q. I wanted to know if it is possible to convert mill scale to iron ore?

A. Steel Mill Scale is generated by rolling hot steel surface. It can be used as a kind of raw material in steelmaking after being sintered.