Georgia-Pacific Corp. was looking for ways to reduce purchased fuel costs at its Madison, GA, plywood manufacturing plant. Although the plant typically uses wood bark and other wood products to fuel its boilers, at certain times throughout the year, not enough bark is available, and additional fuel must be purchased. By increasing process energy efficiency, the plant could reduce its purchases of fuel from outside sources.
To identify opportunities at its plywood manufacturing plant, Georgia-Pacific formed a project team consisting of Darryl Jackson, boiler superintendent at the Madison plant; Stevie Jones, a representative of the North American Insulation Manufacturers Association (NAIMA); and William Brayman, vice president of marketing and technical services, Rock Wood Manufacturing Inc.
Plywood is manufactured by gluing together layers of wood, known as veneer. Logs arrive at the mill in sections and are immediately debarked and soaked in warm, 180°F (82°C) water for 6 hr. This softens the wood and makes it easier for the plant's processing equipment to peel off layers from the log. Once the logs are sufficiently softened, they pass through a lathe that shaves off layers of wood veneer. The veneer then is sent to a dryer, where it is subjected to 405°F (207°C) heat. From the dryers, the veneer is sent to the glue line, where it is layered with glue and pressed into a plywood panel. Once pressed, the panels are trimmed on a saw line and banded for shipment.
Before the plant improvements, steam lines to the mill's four dryers were uninsulated. Heat was lost from the 1,500' of saturated steam lines all day long, wasting energy and reducing dryer temperature. The temperature drop in the dryer increased the veneer's drying time, which in turn slowed down the entire plywood manufacturing process. The uninsulated steam pipes, which operated at 437°F (225°C), also presented a danger to plant personnel.
Insulation Improves ProcessUsing a software program developed by NAIMA, the project team estimated that insulating the steam pipes to the dryers would significantly reduce heat loss. Preventing this heat loss would increase the dryers' operating temperature by 15°F and maintain a consistent process temperature throughout the steam lines.
Based on the software calculations, Madison plant personnel installed 2" mineral fiberglass pipe insulation on all of its steam lines. The 2" dimension was determined to be the most effective insulation thickness, minimizing annual system operating costs while achieving the goals of reducing heat loss, maintaining process temperature and reducing pipe surface temperature. In total, 970' of insulation was added to the plant's process steam lines. In addition, the team replaced 70 steam traps on the dryer lines. The new traps resulted in a 10% increase in condensate return, further increasing energy savings.
Installing insulation is one of the easiest ways for an industrial plant to reduce energy consumption and greenhouse gas emissions. Compared to many other energy efficiency improvement opportunities, insulation is low cost, easy to install and yields a fast payback.