Wheel Manufacturer Slashes Paint-Line Fuel Consumption

The aluminum division of Central Motor Wheel of America, Inc. (CMWA), Paris, KY, recently approached the Environmental and Energy Systems group of Dürr Systems Inc., Plymouth, MI, as part of its green-factory efforts to reduce fuel consumption along its paint lines. CMWA, a joint venture of Central Motor Wheel of Japan, Ltd. and Toyota Tsusho of America, manufactures steel and aluminum wheels for the automotive industry.

Dürr targeted two paint lines at the plant and their respective emission-control devices for evaluation. Each paint line consists of primer and topcoat booths that recirculate a significant amount of air back to the spray booth, while a portion of the air is exhausted to a thermal oxidizer emission-control system. The air exhausted to abatement is replaced via a fresh-air source to the spray booths. Each line also includes primer and topcoat ovens that exhaust to the oxidizers.

One paint line included a 15,000-ft.3/min. Durr high-efficiency regenerative thermal oxidizer (RTO) with a thermal-energy recovery rating of 95 percent and an average temperature rise across the unit of 100 F. The other line treated its emissions with a 13,000-ft.3/min. recuperative thermal oxidizer with a thermal-energy recovery rating of 55 percent and a temperature rise across the unit of 580 F. Since both oxidizers treated relatively the same air volume and emission concentration—11,675 ft.3/min. and 21 lb/hr. on average—the recuperative oxidizer became an area of distinct energy-saving opportunity.

“The recuperative oxidizer probably offered a lower capital cost and improved the bottom line of the initial paint-line package investment,” says Durr’s Karl Walby. “However, the inefficiency of the recuperative oxidizer resulted in long-term fuel consumption approaching $500,000/yr. based upon today’s natural gas prices.”

After completing a cost-benefit analysis comparing new replacement equipment and secondary heat recovery, Durr discovered that an alternative solution existed at the end of a paint line residing at the firm’s steel division, some 200 yards from the aluminum division. The steel division was equipped with a Durr 40,000-ft.3/min. Ecopure RL40 RTO. Since capacity utilization of the steel-line RTO was only about 35 percent, requiring only 14,000 ft.3/min., the plant opted to relocate the Ecopure RL40 from the steel line to treat the combined emissions from both aluminum paint lines. It then removed the inefficient recuperative oxidizer from service and moved the Ecopure RL15 from the aluminum division to the steel paint line.

The project, completed in six weeks, achieved an 80-percent reduction in fuel consumption and a natural-gas reduction of 7.25 million Btu/hr., with a projected annual savings of $427,000 based on current fuel costs and production hours of operation.

Durr Systems Inc.: 734/459-6800; www.durr.com

See also: Ecoclean, Inc.

Technologies: Finishing

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