The Making of Pulp

Summary

Clearwater Paper Mill in Idaho plays a crucial role in paper production by efficiently recycling local wood residuals such as chips and sawdust. Using the sustainable Kraft process, the mill transforms these materials into pulp by removing lignin with chemicals, generating energy in the process. The mill also prioritizes environmental responsibility, using millions of gallons of water daily, which is filtered and returned to the river. Clearwater’s advanced recycling and water management systems make it one of the cleanest pulp mills in the U.S., ensuring minimal waste and reducing ecological impact.

Takeaways

• 😀 Idaho forests are crucial in paper production, with wood chips, sawdust, and bark being key ingredients at Clearwater Paper in Lewiston, Idaho.
• 😀 Clearwater Paper is the second-largest customer for local sawmills, utilizing sawmill residuals to create valuable paper products.
• 😀 Clearwater Paper's mill in Lewiston accounts for half of all forest product sales in Idaho, receiving over 240 truckloads of wood fiber daily.
• 😀 The mill uses a process where wood chips are emptied from trucks, sorted, and processed for pulp and paper production.
• 😀 Wood chips are screened for size, and unwanted pieces are returned to the hog fuel pile for burning to generate steam and electricity.
• 😀 The cellulose fiber in the wood chips is the primary ingredient for making paper, while lignin (a natural glue) is removed in the digestors.
• 😀 Digestors function as large pressure cookers, using heat and chemicals (white liquor) to break down lignin and separate fibers.
• 😀 The process recycles chemicals through cycles of white liquor, black liquor, and green liquor, making it environmentally sound and cost-effective.
• 😀 The Craft process, which is an integral part of the paper-making process, revolutionized paper production by making it affordable to the masses.
• 😀 Bleaching stations ensure the removal of any remaining lignin, making the pulp progressively whiter, ready for use in products like tissue or paperboard.
• 😀 Clearwater Paper uses millions of gallons of water daily, and employs a complex system to recycle and purify the water before returning it to the river.
• 😀 Clearwater Paper operates with stringent environmental constraints, ensuring minimal waste and maintaining high environmental standards in its operations.

Q & A

What role do Idaho forests play in the paper-making process?

Idaho forests provide raw materials like wood chips, sawdust, bark, and other small pieces, which are essential ingredients in the production of paper and electricity at Clearwater Paper Mill.

How does Clearwater Paper Mill use wood chips in its operations?

Wood chips are first screened for size, with those that are too large or too small returned to the hog fuel pile. The sorted chips are then washed and sent to the digestor, where they are processed to extract cellulose fiber for paper production.

What is the purpose of the digestors in the paper-making process?

The digestors are large pressure cookers where wood chips are cooked with white liquor, which dissolves the lignin (natural glue in wood), allowing the cellulose fiber to be separated and used for making paper.

What is lignin, and why is it removed in the paper-making process?

Lignin is the natural glue that holds wood fibers together. It needs to be removed to separate the cellulose fiber, which is the primary ingredient for making paper.

What happens to the black liquor created in the digestor?

The black liquor, which contains dissolved lignin and water, is evaporated to concentrate the chemicals. It is then burned in a recovery boiler, generating steam and electricity for the mill, while the spent cooking chemicals are turned into green liquor.

How is the recycling of chemicals in the paper-making process achieved?

The process uses a closed-loop system, cycling chemicals between white liquor, black liquor, and green liquor. After the chemicals are burned in the recovery boiler, they are restored to white liquor through the addition of lime, making the process both sustainable and cost-effective.

How does the bleaching process improve the quality of the pulp?

After the cellulose fiber is separated, it undergoes a bleaching process to remove any remaining lignin. This makes the fiber whiter and cleaner, turning the dark brown fiber into bright white pulp ready for paper production.

Why is water so important in paper production at Clearwater Paper Mill?

Water is crucial for cooling, cleaning, moving products, and generating steam inside the mill. Clearwater Paper Mill uses millions of gallons of water daily, and it is continuously recycled throughout the process to minimize waste.

What measures does Clearwater Paper take to ensure environmental sustainability?

Clearwater Paper operates with tight discharge constraints, ensuring that water is cleaned and purified before being returned to the river. The mill also strives to minimize waste and uses state-of-the-art equipment to maintain high environmental standards.

How does Clearwater Paper Mill contribute to the local economy?

Clearwater Paper Mill is a major customer for area sawmills, often the number two customer for many in the region. The mill processes more than 240 truckloads of wood fiber daily, supporting the local forestry industry.