THE CARIBOU MILL

Several features should make this a low-cost milling operation Most important is the low work index of the ore “The early indications are that we will not need to use balls in the grinding mill,” Williams said This, combined with the absence of a crusher, should contribute to low consumption of energy and other consumable items The ore will be ground down to a very fine 80% passing 30 microns

Other consumable items include lead reagents (Aerfloat 241, lime and mibc) and zinc reagents (copper sulphate, lime and sodium isopropal zanthate) East West has cut capital costs, too, by building its own column flotation cells Agitair flotation cells are used for the lead rougher stage, zinc rougher and zinc cleaner stages, but the custom-built column cells will be used to clean the lead “It’s still a relatively new technology, so we put them where we knew they’d work,” Williams said The columns are 10 m high and 1 2 m in diameter Water sprays at the top serve to wash unwanted minerals from the deep column of froth This way, only minerals which are chemically attracted to the bubbles go into the launder The result should be an improved grade

A Courier 30 Outokumpu on- stream analyser has been installed to monitor the flotation process, a Bailey System 90 controls the process and ComputerAide of Fredericton, N B , has been contracted to do custom computer programming which will mesh metallurgical results with marketing and financial information Alan Bradley programmable logic controllers are used to control the Lasta pressure filter, a Japanese unit which is one of only 10 in Canada The filter has a capacity of 3 1/2 tonnes of concentrate every 11 minutes Lead and zinc concentrates are combined before going into the pressure filter (A moisture content of 7% is East West’s objective ) Despite the level of automatic control, 30 people will be required to keep the mill running 24 hours a day

Concentrates will be trucked 82 km to the port of Belledune, N B , to be loaded on to ocean- going ships

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