ACIPCO’S 65-Megawatt Contiarc Furnace
All New, Uniquely Efficient Melting Technology
Inducted in 2002
Three decades ago, ACIPCO (the American Cast Iron Pipe Company, Birmingham plant) accepted the state’s first Governor’s Clean Air Award, recognizing its development of a state-of-the-art cupola furnace. Used to melt metal and other charge materials for manufacturing ductile iron pipe, the cupola had set a new standard of cleanliness. And yet, it remained a very conventional furnace: the same type used at ACIPCO since the firm’s founding in 1905.
Five years ago, however, ACIPCO took steps to break through convention. The creative engineering behind its all-new, electric Contiarc furnace may well become this company’s greatest innovation yet, saving energy, reducing pollution, and accommodating raw materials other than increasingly scarce coke and clean scrap (required ingredients for standard production of ductile iron pipe). The 65-MW Contiarc furnace was constructed as a test facility in Birmingham in 1997. It is the brainchild of ACIPCO foundry experts, assisted by Alabama Power Company engineers and the German design/engineering firm SMS Demag. The $70 million furnace is the only one of its kind in the world for melting iron. Its source of electricity is its own substation, located across the street from the ACIPCO plant. Strong enough to power all of the homes in Tuscaloosa, the Contiarc’s power supply is the largest of its kind in the world.
The Contiarc furnace evolved from electric-arc furnace technology, which uses a fixed annular shaft with a central electrode, a corresponding bottom electrode, and a stationary shell. It is 30 feet in diameter and is continuously operated. Using the Contiarc, iron can be tapped continuously or intermittently. The Contiarc design allows raw materials to be fed into the top of the furnace uninterrupted, using a radially arranged conveyor to distribute the scrap throughout the ring shaft area. The maintenance of a full stack of charge material allows this material to be continuously pre-heated by the energy in the furnace offgases. The pre-heating significantly reduces the energy needs of the furnace and is one advantage of the Contiarc design.
Another of its energy-saving advantages is the marked lessening of heat loss at the walls and roof of the furnace. The Contiarc’s walls are shielded by charge materials, and the usual practice of opening the roof to charge the furnace is eliminated. The Contiarc also produces iron that contains less sulfur, an element detrimental to ductile iron production. Furthermore, with the Contiarc, ACIPCO acquires a wider choice of raw materials to use in its ductile iron. Among the low-cost ferrous (detrimental element free) charge materials that the Contiarc accommodates are direct-reduced iron and hot-briquetted iron. These two raw materials produce an iron with lower residual quantities of manganese, chromium, and copper, three elements that can also impair the quality of ductile iron.
Finally, the Contiarc furnace greatly reduces air pollution, its crowning glory in an age of tightening clean-air laws and expensive prospective clean-up for standard cupolas. The Contiarc easily meets or exceeds all regulatory requirements. The scrap column acts as a preliminary dust filter, so that offgases contain some 40 percent less dust than in other furnaces. Gases rising from the lower furnace are collected by a ring header and fed to the emission control system. The longtime problem of emissions discharging into the furnace building is totally eradicated in the Contiarc.
The Contiarc’s anti-pollution accoutrements at ACIPCO include a 50-foot bridge supporting a spray-cooling unit measuring 12 feet across. The spray cooler lowers the temperature of emissions from the furnace, making it possible to treat any pollutants. Pollution control also includes a lime spray dryer-adsorber for sulfur removal, and a bag house, or filter building.
ACIPCO is one of the United States’ leading producers of pipe and fittings for water and wastewater systems. The Birmingham plant is the world’s largest individual iron-pipe-casting facility. With 2,300 employees in Birmingham and 3,000 in all, ACIPCO is one of Alabama’s most significant manufacturers. It is also one of the state’s oldest — yet most up-to-date — manufacturers, with a history of innovations ranging from new products to nontraditional employee relations. ACIPCO’s 1972 cupola furnace was previously inducted into the State of Alabama Engineering Hall of Fame in 1991.