Domtar Hawesville projects deliver results
Domtar’s wood chip conveyor runs from the Ohio River all the way to the Hawesville mill’s gates. The mile-long conveyor moves 750,000 tons/year of wood chips from barges to the mill, a volume that represents a pile of chips as high as the Empire State Building and as wide as a football field.
Five years after introducing a barge unloading system, Domtar reports that its Hawesville Mill continues to embark on projects to increase reliability and performance in producing pulp and paper. These continuous improvement (CI) projects are saving time, reducing costs, increasing efficiency and lowering our environmental impact.
Conveyor belt reduces traffic, pollution. In 2014, Domtar worked with Ingram Barge Co. to develop a barge unloading system that uses a mile-long conveyor to deliver wood chips from the banks of the Ohio River to the mill. The system eliminates the need for truck transportation, which has drastically reduced traffic congestion and pollution. In its five years of operation, the conveyor has eliminated over 270,000 truck trips from local roads and saved about 550,000 gallons of fuel.
“The Hawesville mill chip conveyor is an agile and unique solution that’s paying dividends for us,” says Bill Edwards, VP of manufacturing for communication papers. “It’s just one example of a number of continuous improvement projects at the mill — and across our entire mill system — that are allowing us to take another step forward in productivity and reliability.”
Data analysis increases efficiency. Another CI project is a plant analysis and visualization tool called PARCview, a system from dataPARC, Vancouver, WA. It monitors up-tothe- minute manufacturing data across Domtar’s network of 13 pulp and paper mills.
Hawesville is testing a state-of-the-art wood chip moisture analyzer to provide operators with real-time data to keep the mill’s chip digesters running smoothly. “Chip moisture can vary based on any number of conditions,” says Hawesville mill manager Grant Forrest. “Differences in wood density due to moisture can cause variability in our digester’s yield.”
Historically, the mill tested chip moisture weekly. Those data weren’t timely, so couldn’t be used to control digester operations. “Realtime data is key,” Forrest says. “With the chip moisture analyzer, we will be able to better manage our chip blends and liquor flow to optimize the digester and reduce variation.”
Better design reduces downtime. Woodchip flow through the digester is another area ripe for improvement. Over the past three years, the mill had lost an average of 3,500 airdried tonnes of production due to uneven chipflow unevenly through the bin, creating plugs. So the team contacted the bin manufacturer to discuss the issue.
“In working with the equipment manufacturer, we discovered they made a design change after installing our bin that improved chip bin flow,” Forrest says. “We incorporated the design change and reoriented the bin during our fall 2018 outage, and the results have been much improved.” Domtar’s Kamloops, BC, mill saw similar improvements after updating its chip bin so that instead of relying on gravity to move the chips, mechanical screw feeders at the bottom of the bin churn the chips to move them through the bin more reliably. As a result, the mill was able to increase its daily pulp production by 8%.