Application of propeller fans at Wisconsin Industrial Sand

Fairmount Mineral's Maiden Rock underground sand mine historically delivered air to ventilate diesel-powered equipment at its working faces through high-resistance,381-mm-(15-in.-) diameter PVC distribution lines. In support of plans for expanded production, three new, low-resistance ventilation design alternatives were analyzed. The study determined that adequate ventilation for expanded production was possible with various commercially available, high-volume/ low-pressure fans combined with a systematic layout of control structures. The recommended redesign was implemented in 2001, resulting in a significant increase in flow volumes and a noticeable improvement in the mine environment.

Background

The Maiden Rock Mine is located adjacent to the Mississippi River at Maiden Rock. WI, near the north end of Lake Pepin (Fig. 1). The mine extracts sandstone underground using drill-and-blast mining methods. Mining operations employed a more or less regular room-and-pillar mining pattern. In the 1950s, rooms were approximately 6.1 m (20 ft) wide by 4.5 m ( 15 ft) high,but the rooms mined since 1991 are approximately 9.2 m (30 ft) wide and range from 6.1 to 9.2 m (20 to 30 ft) high,and the rooms are driven on varying centerlines.

The roof in several areas, particularly in the currently active mining area, is mined with the intent of leaving an arched roof. But this resulted in peel-outs extending upward 0.3 to 1.8 m (1 to 6 ft) through the sandstonedolomite transition. These peel-outs presented a more complex perimeter profile, thus increasing the complexity of construction of the ventilation control structures.

Blasted sand is mucked from the faces by rubber-tired loaders and delivered to a grizzly located in close proximity to the active mining faces. The scalped sand was conveyed to a surge tank and subsequently slurried for transportation to a wash plant located near the current mine main access portal. Sand from the wash plant was passed through cyclones to separate the desired product, with the cyclone underflow placed on the mine floor to allow draining of the contained water. Drained sand was loaded by a rubber-tired loader into 27-t (30-st) trucks for transportation to the surface plant.

To meet U.S. Mine Safety and Health Administration (MSHA) ventilating requirements, it was necessary to base the quantities of air required on the size of the underground equipment fleets, the types of equipment and the sizes of the diesel engines used. From a ventilation perspective, the Maiden Rock Mine most closely resembles underground limestone mines in that the …