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Georgia Pacific’s Big Island plant has installed a piece of equipment that both helps the environment and the plant’s bottom line.
It’s called a recovery boiler and it allows the plant to recycle chemicals needed to turn wood chips into fiber. It also lets them use waste material as fuel.
According to Eldon Brammer, wood chips have to be cooked in a device called a digester. The digester uses a caustic liquid — called cooking liquor that is comprised of soda ash and water — heated with steam, to separate fiber from other components of the wood. Wood pulp comes out of this and is sent to washers. Fiber comes from the washers and goes to the paper machines to make the paper board from which cardboard boxes are constructed.
A waste product, called weak liquor, also comes out. This is 8 percent solid and has a pH of 8.5. This goes to an evaporator which removes much of the water, which is recycled back into cooking liquor. The result is called strong black liquor. It’s 60 percent solids and this is used to fuel the recovery boiler.
The strong black liquor is the primary fuel for the recovery boiler which provides the steam used in a number of the plant’s operations. Some natural gas is also used for fuel, but the primary fuel is the waste product of the pulp-making process.
Along with generating steam, it also recovers soda ash which comes out in a molten stream. This is recycled back into the liquid used to cook wood chips.
“The majority of our soda ash is going around in a circle,” said Brammer.
The boiler saves on fuel and saves on input material.
The boiler, itself, is as tall as a three-story building and work on the project began last fall with demolition work to clear the site for the boiler and the structure that houses it. According to Zoë Miles, the mill’s public relations coordinator, it was finished on time and under budget. It was also done safely.
“Everybody went home safe, that’s the main thing,” said Brammer.
The $50 million project, which involved 26 contractors and 13 vendors is still in the commissioning stage, to get up to full operation.
Along with saving money by recovering soda ash and using a waste product for fuel, the recovery boiler has reduced the plant’s emission of volatile organic compounds (VOC) by 92 percent and a total emissions reduction of 94 percent. Stack gasses run through a preheater to wring out the last possible bit of heat by preheating water coming into the boiler. The gas then passes through a steam scrubber before exiting into the atmosphere. All that can be seen coming out of the boiler, on the outside, is a plume of steam.
The people running the boiler don’t have to stand around it. Its operation is controlled from a darkened room filled with glowing computer monitors that let operators view every stage of the process with constant real-time measures of temperatures and pressures. Video monitors let the operators actually see what’s going on.
“This is their version of Star Trek,” commented Kim Kennedy as she sat at one of the monitoring positions.
The Big Island paper mill has been part of the Big Island community since 1891 and still has one paper machine that dates back to 1915. That machine, of course, has been updated many times since then. They produce approximately 1,200 tones of paper per day and take in recycled paper. The medium machines use between 20 percent and 30 percent recycled paper. Medium is the corrugated center of a cardboard box. This fluted material gives the box its strength. Their liner board, the non-corrugated portion of the box, is 100 percent recycled paper.
The paper mill is Bedford County’s second largest employer and is one of Bedford County’s largest taxpayers.