Innovations MANTLES, THIOSALTS AND MILLS

CAE has built a prototype mantle and tested it at BHP-Utah’s Island Copper mine in Port Hardy, B.C. During the 4-month test (from November, 1988, to February, 1989), about 60% more tons were crushed by the gyratory crusher. The unit receives run-of-mine ore in chunks as large as 2x2x3 ft and reduces t hem to 8x8x8 inches.

The test was successful and answered any basic questions about the practicality and workability of the concept, LePage says.

Typically, conventional mantles are constructed of 1- or 2-piece manganese steel castings (with a hardness of 200 BHN). To attain maximum abrasion resistance from such a mantle material, the crusher must be choke- fed (continually flooded with ore). The heavy impact of crushing the ore work hardens the manganese steel (to 500+ BHN), thus keeping the surface hard.

Since few mining operations can maintain a continuous flow of ore to sustain this condition, more rapid wear and more often replacement of conventional mantles typically results. By increasing the period between such major repairs to coincide with other mine and mill maintenance cycles, the availablility of the primary crusher can be increased significantly. This has been achieved by the CAE liner segment concept. The liners are made of heat-treated steel which do not have to be work-hardened to achieve optimum wear life.

The contour of the liner segments can be modified to suit the application and material being crushed, LePage says.

Productivity improvements were so significant at Island Copper that another unrelated mining operation has ordered a trial set and a major U.S. mining company is very interested in the concept, LePage adds.

Cae has obtained a patent. Circle reply card No. * Brunswick Clean-up

Brunswick Mining & Smelting is Btaking seriously its responsiBbility to the environment. The company is committed to reducing (to 5,000 L per minute from 12,500 L per minute) the amount of fresh water it takes from the Nepisquit River in northern New Brunswick, and it also wants to reduce the amount of thiosalts discharged into that river. The company’s long-term strategy is to recycle, back into the mill, more of the water which now goes into a huge tailings area north of the 10,000-tonne- per-day concentrator.

Thiosalts are unstable, partially oxidized compounds of sulphur generated in the mill’s grinding process at a rate of about 35 tonnes per day. By the time the tailings are pumped to the tailings area, they contain about 1,000 parts per million thiosalts, according to Concentrator Superintendent John Martin. These compounds pose a problem because they cannot be removed from the water by conventional lime treatment. Once the thiosalts enter the Nepisquit River, they oxidize, creating acids that can damage the habitat. Brunswick has constructed a new 425,000-cu-m pond at the end of its tailings area. Called a bio-oxidation pond, it retains the run-off water for a longer period of time, allowing natural biological activity in the pond to oxidize the thiosalts. The discharge water from this pond is treated with hydrated lime.

The bio-pond process gets rid of about half the thiosalts, Martin says. But the process is not very reliable. Activity stops in the winter, for example.

Other technology is available for destroying thiosalts (using any strong oxidant such as chlorine or sulphur dioxide and copper), but is considered too expensive. The company’s objective is to contain the thiosalts at the minesite. “We are getting a group together to review the situation,” Martin says.

A research chemist from the Noranda Research Centre in Pointe Claire, Que., is working to determine the best way to selectively reclaim the tailings water. Milling Notes

Another Swedish manufacturer of mill equipment has set up shop in North Amer ica. Morgardshammar, which has been manufacturing rod, ball, pebble, semi-autogenous and autogenous mills, as well as gyratory crushers and laboratory equipment for more than 100 years, has established a mining division in Denver, Colo.

Two rod and two ball mills have been delivered to a gold mine in Nevada early this summer.

The mills are designed to meet exact ore reduction needs. Features include: computer design (of optimum tumbling action and ultimate size reduction), short trunnion bearings for both spherical roller bearings (for reliability, long life and reduced space requirements) and hydrostatic shoe bearings (in extremely large applications), as well as symmetrical ring gears for mounting on either the feed or discharge head end.

The company builds mills up to 6.5 m in diameter and with installed motor ratings of up to 5,000 kw. Circle reply card No. *

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