Backwater

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Backwater in the context of paper or board-making refers to the water that is removed during the forming section of the machine. This water typically contains fine fibers, loading, and other additives. Here’s a detailed explanation:

Key Concepts:

• Paper/Board-Making Process: The process involves creating a sheet of paper or board from a pulp mixture on a forming section of the machine, where water is drained off to form a continuous sheet.
• Forming Section: This is the part of the paper machine where the pulp suspension is spread out and water is drained away to form a wet sheet of paper.

Backwater Details:

1. Composition:
   • Fine Fibers: Small particles of cellulose that do not form part of the paper sheet but are washed away.
   • Loading: Substances like clay or calcium carbonate added to the paper pulp to improve its properties.
   • Additives: Chemicals added to improve the performance or characteristics of the paper.
2. Removal: As the paper pulp travels through the forming section, water (backwater) is removed to help form the paper sheet. This water contains the fine fibers and additives that did not adhere to the sheet.
3. Re-use and Recycling:
   • System Re-use: The backwater is often re-used within the paper-making system to conserve water and reduce waste.
   • Clarification in Saveall: A saveall is a device used to recover suspended matter from the backwater. It clarifies the water by removing fine fibers and other suspended particles, allowing the water to be recycled back into the process.

Applications and Benefits:

• Water Conservation: Re-using backwater helps in conserving water resources, which is critical in the paper-making industry due to the high volumes of water used.
• Material Recovery: Clarifying backwater in a saveall allows the recovery of valuable fibers and additives, reducing waste and improving efficiency.
• Environmental Impact: By recycling backwater, the paper industry can minimize its environmental footprint, reducing the discharge of wastewater and the consumption of fresh water.

Summary:

Backwater in paper and board-making is the water removed during the forming section, containing fine fibers and additives. This water is typically re-used or clarified to recover suspended materials, aiding in water conservation, material recovery, and reducing the environmental impact of the paper-making process.

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