Source: World Dredging Mining & Construction
The Pitinga Tin Mine, located in the State of Amazonas in Brazil, is operated by the world's largest tin producing company, Paranapanema, using exclusively since 1978 bucketwheel excavator dredges built by Ellicott® International (Baltimore, Maryland).
Since then, international tin prices have suffered periods of decline, which has led to smaller market shares from traditional tin producers such as Malaysia and Thailand, and a greater share for Brazil.
Currently, the Ellicott® dredges at the Pitinga mine are in full operation, extracting material rich in cassiterite. The slurry produced by the dredges is pumped through a pipeline into a floating processing plant, one per dredge, which separates the tin ore.
Because of the heavy clay content in the Pitinga deposit and the high specific gravity of the tin ore, bucketwheel dredges were considered to be the most appropriate equipment for the application, and Ellicott® had the right equipment to offer.
The bucketwheel design is said to be more effective in retaining the heavy, more valuable portions of the material being dredged than the standard basket cutter. The single bucketwheel originally supplied by Ellicott® consisted of eight buckets rotating around a hopper, which was connected to a suction pipe on the side.
In the mid-1980s, Ellicott® developed a new wheel excavator design — the patented Dual Wheel Excavator (DWE). The immediate success of the DWE versus the original bucketwheel prompted Paranapanema to order replacements for the original bucket design supplied with the dredges. As a result, Ellicott® supplied two 150 horsepower, 94-inch diameter and one 250 horsepower, 120-inch diameter DWEs. The original single wheel excavators are still used as temporary tools, when the DWEs undergo maintenance work. One of the advantages of the DWE is the elimination of the bucket flushing system, which was required for the earlier bucketwheel design. The heavy clay in the Pitinga deposit adheres to the bucket walls, blocking further entrance of excavated material to the suction mouth. The water flushing system was used to remove the clay from the buckets.
The DWE utilizes a mechanical system. This method is said to be not only more effective, but it also avoids the energy consumed by the earlier flushing system, thus reducing the overall production costs.
So far, the Ellicott® dredges have accumulated more than 250,000 hours of operation, making the Pitinga mine one of the most experienced dredge mines in the world. The utilization of the DWE-equipped dredges has been a key factor in Paranapanema's success as one of the lowest cost tin producers in the world.
Reprinted from World Dredging Mining & Construction