Waste Disposal and Reuse of
Waste Water in Taconite Ore
Beneficiation Operations
HENRY P. WHALEY, Assistant Works Manager
Erie Mining Company
Pickands Mather and Company
Hoyt Lakes, Minnesota
Erie Mining Company, operated by Pickands Mather & Co., is owned by
Bethlehem Steel Corporation, Youngstown Sheet and Tube Company, the Steel
Company of Canada and Interlake Iron Corporation. It is one of the largest
taconite mining, beneficiation, and agglomerating operations in the world.
Taconite is defined as a ferruginous chert or slate in a form of compact siliceous rock in which the iron oxide is finely disseminated that all the iron bearing
particles are smaller than 200 mesh.
The mine and plant of Erie Mining Company is located at Hoyt Lakes, Minnesota, 70 miles north of Duluth in the Minnesota Arrowhead country. This is the
northeast portion of the state and is characterized by many lakes and swamps and
void of major terrain features except the Mesabi Range of hills. These hills rise
about 500 ft above the surrounding area and form the Laurentian water divide.
To the north, flowage goes to the Hudson Bay and the south, drainage to the Great
Lakes and the Mississippi River. Being located on the divide the mine is near the
headwaters of the local rivers and, therefore, even in the state of 10, 000 lakes,
the water supply is a critical item.
The climatic conditions which also effect the operation is characterized by
severe winters. During the winter months temperatures of minus 20 and 30 degrees
are common with minimums approaching 50 below. The annual precipitation is
about 25 ins. of water of which there is included an average of 60 ins. of snowfall.
The mean temperature is about 37.
PLANT OPERATION
Erie Mining Company mines 24, 000, 000 long tons a year of taconite which is
hauled to the plant by railroad cars. An additional 13, 000, 000 long tons of waste
rock and surface material is hauled to dumps located off the iron formation.
The taconite ore contains 20-30 per cent iron. The mineral magnetite forms
about 67 per cent of the total iron content of the ore. In the process, the ore is
crushed in four stages to minus one in. Then the material is conveyed to the concentrator where water is added.
The concentrator at the Hoyt Lakes Plant houses the grinding and concentrating sections, pumping equipment, and control centers for power and water distribution system. This huilding is over 1/4 mile long. It is capable of handling
68, 000 long tons per day. There are 27 identical mill lines, each of which include the following equipment:
1. One 11. 5 ft x 14 ft rod mill driven by 800 HP motors.
2. Two roughers, which are three ft wide, double drum, electric magnetic
separators (first stage of concentration).
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