By reengineering how aluminum ingots are preheated prior to hot rolling, Alcoa’s Warrick Operations in Indiana cut natural gas consumption by 25%, shaved off US$1.4 million in energy costs, and reduced greenhouse gases and other emissions by about 9,100 metric tons (10,000 tons) between 2000 and 2003—with zero capital dollars spent.

By following the make-to-use principle of the Alcoa Business System, Warrick developed tools and rethought processes to reduce the amount of energy that was literally going up its stack.

Preheating aluminum ingots to around 499° Celsius (930° Fahrenheit) prior to rolling is necessary to impart required metallurgical properties and to make the metal sufficiently pliable for rolling.  Warrick’s 42 preheat furnaces, each of which holds six 18.4-metric-ton (20.5-ton) ingots, were taking 12 to 30 hours to heat the ingots to the required rolling temperature.

The reengineering initiative reduced the preheating cycle time by an average of 25.8%.  This reduced both the amount of natural gas consumed and the metallurgical variability from load to load—improving customer quality.

Warrick also used a furnace prediction model that determined more aluminum ingots were being heated than was required by the customer—Warrick’s cold mill.  This linkage of furnace performance with customer usage lowered the number of furnaces operating at any given time, reduced the costly inventory of hot ready-to-roll ingots, and cut energy usage.

In 2003, Warrick’s preheat furnace work received an Alcoa EHS Achievement Award.



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