Minntac, the Minnesota iron-ore producer owned by US Steel Corp., has placed a second order with Metso Minerals for a ported kiln system. The system is a retrofit to an existing grate-kiln iron-ore pelletising plant that was supplied by Allis Chambers, now part of Metso Minerals.

The ported-kiln system is a Metso patented design that enables air to be injected into the hot and abrasive environment of the kiln, thereby speeding up the oxidation of the iron pellets in the kiln. The installation of its first ported-kiln system at Minntac in 2001 resulted in lower fuel consumption and higher-quality pellets.