Georgia-Pacific Reaps Benefits by Insulating its Steam Lines
Built in 1979, the Georgia-Pacific plant at Madison, Ga., uses Loblolly pine to manufacture plywood. The tree is abundant in the area. Most of the trees harvested are within a 180- mile radius of the mill. About 20 percent of the trees are grown on land owned by Georgia-Pacific and about 80 percent come from other privately owned lands. The plant runs 24 hours, 7 days a week, and employs approximately 400 people.
The process of making the veneer layers in a plywood panel begins when logs arrive at the mill in sections. They are immediately debarked and soaked in water at 180°F for six hours. This softens the logs and enables them to peel better. The softening process also allows the logs to pass through the lathe much easier and delivers the veneer layers at the right temperature to the dryer where they are dried at temperatures of 405°F.
From the dryers, the veneer layers go to the glue line where layers are sandwiched with glue and then pressed into a panel. From there the panels go to the saw line for trimming before banding and shipping.
Because the steam lines to the dryer were uninsulated, heat was radiating out and millions of Btu were being lost. The heat loss resulted in a loss of pressure and a reduction in temperature as the plywood moved down the line. The increased drying time needed caused the process to slow down significantly.
While Georgia-Pacific wanted to insulate the steam lines for energy conservation, improved process efficiency and personnel protection, the company also wanted the insulation for a more pragmatic reason—to eliminate dependence on purchased fuel. The plant normally uses wood bark and wood byproducts for fuel. However, at certain times of the year the bark is too thin for use as adequate fuel so additional fuel had to be purchased from an outside source.
Determining the Thickness of Insulation
Once the decision was made to insulate the steam lines, a computer program called 3E Plus created by the North American Insulation Manufacturers Association (NAIMA) was used to determine the insulation thickness required to insulate the 1,500 feet of saturated steam lines with temperatures operating at 437°F.
Computer projections estimated that insulation would significantly reduce the heat (Btu) loss along the steam lines leading to the dryers. This reduction in heat loss alone could increase the operating temperature by 15° and maintain the process temperature along the length of the lines. The combination of a higher temperature in the dryer lines and a more consistent process line temperature would result in a faster and more efficient veneer plywood process.
The Madison plant installed two-inch-thick fiber glass pipe insulation. Two inches is the thickness needed to reduce heat loss, maintain process temperature and bring the outside surface temperatures of the pipes down for personnel protection. Insulation footage was as follows: 120 feet of insulation on the twelve-inch process line; 200 feet on the eight-inch process line; 220 feet on the six-inch process line; 80 feet on the four-inch process line; and 350 feet on the 1-1/2-inch process line.
A major advantage of using mineral fiber insulation to insulate the steam lines was that no downtime was required. Several areas that could not be insulated while the line was running were insulated on schedule down days. Says Jackson, “We do dryer maintenance once a week so the dryer is shut down during that time. That’s when the insulation was installed on those areas that couldn’t be accessed while the dryer was running.”
The personnel at the Georgia-Pacific plant were pleased with the results of the insulation project.
Improved Process Efficiency.
The lines to the mill’s four dryers have all been insulated, and according to Darryl Jackson, boiler superintendent at the Madison plant, “Gauging the increase in throughput has proven to be a bit more complex than we first thought. A more accurate gauge of the effectiveness of the insulation is the steam usage. The insulation has allowed us to cut our steam usage by approximately 6,000 lbs./hour. This is equivalent to saving about 18 tons of fuel per day. I can track these numbers with a totalizer so I know exactly what the dryers are pulling at any given time.”
Dependence on Outside Fuel Eliminated.
By insulating the piping, Georgia-Pacific has been able to eliminate the purchase of fuel. “Currently we are selling some of our excess fuel to a paper company,” says Jackson.
Reduction in Pollutants.
By reducing fuel consumption, the Madison plant has been able to reduce the amount of ash being generated and estimates that the energy saved through insulation has reduced the amount of C02 emissions by 5 to 6 percent.
Increased Personnel Protection
Prior to installing the insulation, the piping in the Madison plant had a surface temperature of approximately 400°F. With insulation, the surface temperature has been reduced to approximately 85°F—a safer level for personnel protection.
In addition to insulating the steam lines, Georgia-Pacific also replaced 70 steam traps. According to Jackson, “We’ve probably gained 10 percent condensate return from replacing the thermal dynamic traps. By increasing the condensate by 10 percent, our savings will be approximately $86,000 per year based on an $8 per ton fuel cost.
Georgia-Pacific estimates that the amount of energy saved by insulating the steam lines to the dryers and installing new steam traps is approximately 7,212,000 Btu per hour.
Payback on Initial Investment
Calculating how long it takes to pay back an initial insulation investment is an integral part of Georgia-Pacific’s energy management program. Based on the results realized, the payback period at Madison was approximately six months.