NYS Governor's Awards for Pollution Prevention - Alcan Rolled Products
Alcan Rolled Products, Oswego
Under a pollution prevention program initiated in 1986, the company began using an advanced metal cleaning and degassing technology, which reduced its chlorine and hydrogen chloride emissions, both hazardous air pollutants. The new technology also reduced chlorine consumption.
A facility employing roughly 800 people, Alcan Rolled Product produces aluminum ingots that are transformed into packaging, transportation and building products. Melting and casting operations annually produce more than 400,000 tons of aluminum ingot.
Methodologies and Procedures
Chlorine has long been used to purify aluminum metal by removing dissolved hydrogen gas, sodium, lithium and calcium-based impurities and oxide particles. During the purification process in which fluxing gas mixtures containing chlorine are bubbled through molten aluminum, the transitional state of aluminum chloride is produced. Hydrogen chloride emissions are produced by the hydrolysis of aluminum chloride while chlorine emissions result from the incomplete reaction of the chlorine gas. Alcan has State air permits for both the hydrogen chloride and chlorine emissions.
An improved in-line fluxing technology for metal cleaning allows the use of much lower quantities of chlorine gas. The new fluxing technology also improves metal cleanliness levels over older furnace fluxing practices, leading to a higher quality product.
The technology substitutes argon or nitrogen for most of the chlorine gas which was previouslyused. The generation of large quantities of small bubbles of the process gas (argon or nitrogen), which desorbs hydrogen dissolved in the aluminum, is the essence of the new technology. The process gas carries the impure solids to the surface of the melt where they are skimmed off. The use of chlorine in the fluxing gas mixture, though still required for the removal of sodium, lithium and calcium, is greatly reduced. Hydrogen is vented with the spent process gas.
After analyzing date from studies of melting and casting process after the introduction of the new technology, Alcan determined that changes in standard operating procedures could further reduce chlorine usage. Increased emphasis on process control coupled with operator monitoring of chlorine usage have contributed to significant decreases in chlorine consumption.
During a period of seven years, the company reduced its use of chlorine and hydrogen chlorine air emissions by 94 percent.
Product quality was improved due to increased metal cleanliness levels.
Alcan realized a savings of $434,000 annually based on decreased use of raw materials (from 6.34 lbs of chlorine/ton of aluminum in 1986 to 0.35 lbs of chlorine/ton of aluminum in 1993).
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This page was last modified March 8, 1999