Thick Stock System Design
The thick stock system is where the papermaking process begins. In this system, pulp fibers are blended together, refined, diluted, metered, and some additives may be added. This course discusses the principles of the thick stock system as well as the key equipment used, how stock blending is achieved, as well as how high density chests and stock thickeners work.
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Learning Objectives
• List the four principle objectives of the thick stock system • Identify safety hazards and safety guidelines related to thick stock systems • Identify and describe key equipment used in thick stock systems • Identify and describe primary process flows in thick stock systems • Describe stock blending • List common features of stock storage chests • Describe how high density chests work • Describe how stock thickeners work
Specs
| Course Level | Intermediate |
| Languages | English |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
Why is it important to control stock consistency in the thick stock system?
Consistency control is important because it can affect refining, sheet formation, moisture and weight profiles, and vacuum levels on the machine.
Where is consistency typically controlled in a thick stock system?
Consistency is measured and dilution white water is normally added at the suction of stock pumps to help blend the stock and white water together.
Why is pH control important in the thick stock system?
Good pH control is crucial to steady machine operation because pH plays a major role in refining, additive efficiencies, and drainage. Also, it is easier to control machine pH when the incoming stock pH is consistent.
What is the purpose of savealls in thick stock systems?
Savealls (also called thickeners or deckers) are used to recover fiber and filler from white water, thicken stock, or both. Saveall designs include gravity drum, vacuum drum, and vacuum disc.
What is the role of the machine chest in the thick stock system?
The machine chest dampens any remaining fluctuations and supplies a uniform stock slurry to the thin stock system.
Sample Video Transcript
The thick stock system has four principle objectives. One, to blend the most cost effective combination of fibers, fillers, and chemical additives. Two, to control stock consistency and stock pH. Three, to buffer or dampen variations in stock flow rates, consistencies, and pH. And four, to refine the pulp fibers. Each paper or board machine has their own unique requirements of the thick stock system depending on the type of paper or board being produced. All mills have the same end goal, however, that is to ensure that a uniform stock of high quality is supplied to the thin stock system.
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