Clothing manufacturer adds hot water supply to its process.

M.J. Soffe employs this heat recovery system to improve energy efficiency and increase productivity.
M.J. Soffe Co. uses a constant supply of hot water to dye, set and wash its product. But, as the Fayetteville, NC-based clothing manufacturer's business grew, production increased the need for hot water faster than the 25,000-gal tank could provide. Dye workers often depleted hot water reserves and were forced to halt production while fresh water was heated in the dye with steam. Not only did the lack of hot water lead to decreased productivity, it also affected dye quality.

In 1997, Soffe's manager of maintenance Adrian O'Quinn attended energy efficiency workshops hosted by North Carolina State University's Industrial Extension Service. Eager to enhance both manufacturing efficiency and energy utilization at Soffe, O'Quinn met with NC State University's energy programs director James Parker. Together, they developed solutions that are saving Soffe Co. money and have led to a significant increase in productivity.

Specialist engineers from NC State examined the Soffe Fayetteville plant's systems and noted several areas for improvement. Aside from inefficient air conditioning and lighting systems, the two most obvious energy drains were identified as the process water heating and steam leaks.

NC State helped Soffe personnel develop a wastewater heat recovery system that recovered the heat from used dye water before the company returned the water to the sewer system. Using a system of two 25,000 gal storage tanks, Soffe passes the wastewater and the cool water through a heat exchanger. Heat from the wastewater warms the fresh water to 120°F (49°C), 20°F below the ideal dying temperature for cotton. To resolve the steam leak problem, a steam trap and condensate return system were installed to keep leaking steam and moisture in the system.

Tangible results of the changes included 42% savings in fuel costs for the water boiler over the first seven months, saving the company over $100,000. In addition, Soffe no longer needs to purchase a direct contact water heater to meet production requirements, which saved equipment and energy costs.