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How Do They Do That? Wringing Sulfuric Acid out of Sulfur Dioxide Emissions

Copper Applications in Mining & Extraction

November 1997

By BHP

One of the bi-products of the smelting process is the gas sulfur dioxide (S0₂). Most industrial facilities make a significant effort to reduce the emission of this gas into the air for environmental reasons. For example, at the BHP Copper Metals smelter at San Manuel, Arizona - the largest copper smelter in North America - a sophisticated capture system captures as much as 99 percent of the sulfur dioxide produced in the process.

What is more, the sulfur dioxide that is retained is put through a rigorous process to make a useful product: sulfuric acid, the largest volume chemical used in the world today.

Sulfur dioxide - largest volume chemical used in the world today

The extremely hot (670 degrees Fahrenheit) and dry dirty gas from the flash furnace and converters, which is 10 percent sulfur dioxide, gets sprayed with water, cooled, cleaned, dried, run through a catalytic converter four times, is converted to sulfur trioxide (SO₃), and finally combined with water (H₂0) to make sulfuric acid (H₂SO₄).

As little as 1% of the S0₂is emitted,

The BHP smelter at San Manuel produces 450,000 gallons of sulfuric acid a day, or enough to fill 12,500 rail cars or 52,000 trucks every year.

Mining Operations BHP Copper uses 18 percent of the sulfuric acid it makes for leaching its own oxide ore. Another 40 percent of its sulfuric acid production is sold to other mining companies for their leaching operations.

The remainder of the sulfuric acid production is sold to other industrial users, to make fertilizer, for the paper-making process, for car batteries and hundreds of other uses. San Manuel's sulfuric acid is of such a high purity, it has been certified by the National Sanitation Foundation for use in water treatment facilities. Such a high quality of product mean that San Manuel's acid can be used in a much wider array of markets than a lesser quality product. The acid plant staff accomplishes this difficult task by maintaining an exacting consistency throughout the process. Making a Silk Purse Out of a Sow's Ear.

On CU is the quarterly publication of
BHP Copper, a business group of
The Broken Hill Proprietary Corp., Ltd.
© 1997 BHP Copper


	BHP Copper 550 California Street San Francisco, California 94104

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