This information was gathered from part of a series produced by MiningWatch Canada about the risks of chromium exposure. Additional fact sheets summarizing risks to the environment, chromite workers and nearby populations are also available online at:
Chromite deposits have been identified in Northern Ontario, Canada. Located 500 km north-east of Thunder Bay in a pristine area dubbed the “Ring of Fire”, they are the largest deposits found in North America. Noront Resources is evaluating a plan for an open pit/underground chromite mine and ore processing facility in the Ring of Fire and a ferrochrome production facility to be located somewhere in Ontario. A number of other companies also have plans for mining chromite and other metals in the area.
As companies rush to submit proposals for hosting a ferrochrome plant, some residents feel as though the negative impacts outweigh the potential economic impacts.
Chromite mining and ferrochrome production
To create ferrochrome, chromite concentrate is combined with a reductant (coke, coal, charcoal or quartzite) in a high temperature submerged arc furnace or direct current arc furnace.
Ferrochrome production creates air pollution, dust, slag (waste produced during ferrochrome separation from other ore elements) and process water. These waste materials have the potential to be contaminated with chromium and other heavy metals and chemicals of concern.
Ferrochrome production emits air pollutants such as nitrogen oxides, carbon oxides and sulfur oxides (NOx, COx, SOx) and particulate dusts that contain heavy metals such as chromium, zinc, lead, nickel and cadmium. During the high temperature smelting of chromite ore, some Cr-III is converted to toxic Cr-VI, contaminating the dust. Prior to smelting, steps employed in some processes, such as milling and agglomeration (i.e. sintering) may also produce Cr-VI. Due to the leaching potential of these contaminants, ferrochrome arc furnace dust is categorized as toxic waste in Canada (waste K091) and must be treated before disposal in order to prevent leaching toxins into the environment. Health risks via inhalation are also a concern.
Smelting also produces Cr-VI contaminated slag, with estimated total chromium contents of 2 to 12%. The discovery that dry pulverizing of slag and ore converts Cr-III to Cr-VI may be very important during steps such as ferrochrome recovery from slag and end-uses of crushed slag. When metal recovery from slag is part of the production process, contaminated water is also produced and may require treatment. There are environmental concerns about contaminant leaching that must be addressed prior to slag sale and use.
According to the original Cliffs chromite project proposal, 6,000-12,000 tonnes of ore and 65,000 tonnes of waste rock will be produced per day. The operation’s predicted tailings output would require an area of 250 hectares to contain it. An estimated 2,100 tonnes of slag would be produced per day by the ferrochrome plant, all of which would be cooled with water that will likely require treatment. The original concern over water pollution was heightened by the originally proposed FeCr plant location near Lake Wanapitei (Moose Mountain), a drinking water source for the City of Sudbury.
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