Saving millions by reducing boil-over
In steel manufacture, molten metal can sometimes 'boil over'. Swerea studied the causes of this phenomenon and how to predict and prevent it. The results provide environmental and economic benefits.
Molten metal boil-over sometimes occur during the so-called LD-process, which converts pig iron to steel. Boil-over is costly as it causes both metal wastage and equipment damage. The environment is also impacted as the gas purification system is not always able to manage the particulate emissions from boil-over.
The cause of boil-over
But what causes boil-over and how can it be predicted and prevented?
"Boil-over is caused by dross from metal droplets, slag and gas formed during the process expanding to such an extent that some of the dross is pressed out of the converter [oven]. The best way to avoid this is by using the purest scrap metal possible, and by having good control of all parameters throughout the process," says Mats Brämming, researcher at Swerea.
Mats studied this phenomenon for his doctoral thesis and the knowledge can help steelmakers reduce emissions and costs. For a mid-size European steel plant with a crude steel production of 4.5 million tonnes per year, it is possible to save between SEK 100-500 million by fully eliminating boil-over.