Howard Haselhuhn

The ASISC research center at Michigan Tech is a partnership of academic institutions and industry with interests in mineral processing. Members pool resources to address a diverse spectrum of interdisciplinary research questions. Their primary goal: to develop a new generation of sustainable, economical mineral processing technologies.

PhD student Howard Haselhuhn is an ASISC researcher focused on water chemistry. At an iron-processing facility, he recently studied the technology used to remove impurities from iron ore.

Depending on the time of year, almost all of the water used in an iron concentration plant is recycled. “This is not just important from an environmental standpoint; it is cost effective to conserve the thermal energy in the process water as well as the water quality within the plant,” explains Haselhuhn. “Iron ore concentration facilities depend on surface chemical interactions for many concentration operations; therefore, strict control of water chemistry is necessary. Most tap water is of insufficient quality for direct use within iron ore concentration plants,” he notes.

Iron ore is ground down into very small particles, which are mixed in water. Reagents are added to the mixture to flocculate iron oxide particles. These flocs, which contain more iron, settle quickly, leaving unflocculated particles, containing primarily silica, to remain suspended. However, Haselhuhn discovered, sometimes the raw ore and recycled water contain high levels of magnesium. In turn, that causes silica particles to cluster and settle out with the iron, rendering the separation process ineffective.

“By compensating for the excess magnesium, companies could reduce the loss of iron in their concentration process, something that could provide millions of dollars in potential savings,” he says. “We are fortunate enough to have an abundance of fresh water in the Great Lakes area, which makes iron processing easier. In many other parts of the world, the process water must at least partially come from the ocean, which is very high in magnesium. They can still process; just with different, more expensive methods.”

Once the ore is concentrated, it is in the form of an iron oxide. “Obviously, the oxygen must be removed before it becomes iron,” he adds. “This is typically accomplished by reacting it with a carbon source, typically coal. One direction ASISC has been exploring is replacing coal with a biomass-derived reductant. This decreases dependency upon non-sustainable natural resources.”

The mineral processing industry makes continuous improvements in technology, explains Haselhuhn. “Many of these improvements have been small and locale-specific, but once in a while there is a giant step forward that can bring about a new era in the industry. These dramatic improvements will be necessary to remain a sustainable industry. Unlike many industries, the feedstock (iron ore) is constantly degrading in quality. Eventually, it will not be feasible to process unless new methods are developed.”

“Repurposing waste will be key to reclamation of mining sites once the ore is gone,” he adds. “ASISC is committed to finding ‘zero-waste’ solutions to mineral processing.”