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Based on: Industry Standards and Best Practices

Languages: English

Sample Transcript

Several characteristics of stock and water flows to and around a tissue machine are often monitored and are controlled for multiple reasons, including: to ensure a consistent flow of stock to the tissue machine, to optimize runability of the machine and prevent process upsets including sheet breaks, to optimize the efficiency of chemical additives and the results of various processes including refining, to produce a consistent high quality tissue sheet with the desired sheet characteristics. The following characteristics are often monitored: pH, consistency, temperature, fiber size distribution, freeness, and charge demand.

Tissue Making Process Testing

Training Time: 29 minutes

Several characteristics of stock and water flows to and around a tissue machine are often monitored and/or controlled for multiple reasons. This module will cover pH, consistency, temperature, freeness, and charge demand.

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Freeness can be measured by the Canadian Standard Freeness (CSF) or Schopper Riegler tests.

Freeness can be measured by the Canadian Standard Freeness (CSF) or Schopper Riegler tests.

First pass retention is an indication of how well fines are retained in the sheet.

First pass retention is an indication of how well fines are retained in the sheet.

Consistency control loops utilize consistency and flow transmitters, controllers, and dilution water control valves to manage and control stock consistencies at multiple points in stock systems.

Consistency control loops utilize consistency and flow transmitters, controllers, and dilution water control valves to manage and control stock consistencies at multiple points in stock systems.

Learning Objectives

  • Explain why stock and white water flows to and around tissue machines are often monitored for pH, consistency, temperature, fiber size distribution, freeness, and charge demand
  • Explain what these process tests measure
  • Define first pass retention and identify problems that can result from low retention values
  • Explain how the results of these tests can be used to optimize or ensure machine runnability or sheet quality
  • List safety hazards and safety guidelines associated with stock and white water systems
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Tissue Making Process Testing FAQs

What is consistency?
Consistency is the weight percentage of dry fiber in a mixture of fiber and water.

Why is temperature important?
Water viscosity decreases as temperature increases, which makes the water drain from the sheet more easily. Higher temperatures also improve refining results and can affect chemical additive efficiencies and biological growth.

What is freeness?
Freeness measures the drainage rate of water from a dilute pulp suspension. The faster the water drains, the higher the freeness.

Why is charge demand important?
Anionic trash or cationic demand is important to measure because undesirable dissolved materials in the white water reduce the effectiveness of additives and can cause runability problems.

Why is pH control important?
pH affects chemical additive efficiency and retention, refining, retention, drainage, and formation.

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