Page 10 - MetalForming September 2009

TechUpdate Wheel Manufacturer Slashes Paint-Line Fuel Consumption
The aluminum division of Central Motor Wheel of America, Inc. (CMWA), Paris, KY, recently approached the Envi- ronmental 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 Amer- ica, manufactures steel and aluminum wheels for the automotive industry.
Dürr targeted two paint lines at the plant and their respective emission-con- trol 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 oxi- dizer 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 top- coat ovens that exhaust to the oxidizers.
One paint line included a 15,000- ft.3/min. Durr high-efficiency regenera- tive thermal oxidizer (RTO) with a ther- mal-energy recovery rating of 95 percent and an average temperature rise across the unit of 100 F. The other line treat- ed 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 treat- ed relatively the same air volume and emission concentration—11,675 ft.3/min. and 21 lb/hr. on average—the recuper- ative 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 recu- perative oxidizer resulted in long-term fuel consumption approaching $500,000/yr.
based upon today’s natural gas prices.” After completing a cost-benefit analy- sis comparing new replacement equip- ment and secondary heat recovery, Durr discovered that an alternative solution existed at the end of a paint line resid- ing 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, requir- ing 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 recu- perative 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
8 METALFORMING / SEPTEMBER 2009
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