OCC – HD Centrifugal Cleaners
OCC plants convert recycled old corrugated containers into pulp that can be used on paper and board machines to make valuable pulp and paper products. After repulping, the OCC pulp contains some contaminants, such as staples, glass debris, and sand, as well as fiber flakes and bundles that were not separated into individual fibers during repulping. To remove these undesirable materials, the pulp slurry goes through one or more screening processes to remove the contaminants that are larger than fibers, followed by one or more cleaning processes to remove smaller contaminants that have lower or higher densities than pulp fibers. This course describes the high density cleaners which remove large, dense contaminants from the repulped OCC before it reaches other screening and cleaning equipment.
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Learning Objectives
• Describe the purpose of high density cleaners at OCC plants
• Describe typical high density cleaner installations
• Describe how high density cleaners differ from other forward centrifugal cleaners
• Identify and describe the main components of a high density cleaner
• Describe a typical junk trap dump cycle
• Describe the process flows for HD centrifugal cleaners
• Identify important operating variables for high density cleaners
• List safety hazards and guidelines associated with high density cleaners
Specs
| Course Level | Intermediate |
| Languages | English |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
What is the primary purpose of high density cleaners?
The purpose of high density cleaners is to remove large, dense contaminants from repulped OCC before it reaches other cleaning and screening equipment.
What are some physical differences between high density cleaners and other forward centrifugal cleaners?
Compared to other forward centrifugal cleaners, high density cleaners tend to be taller and larger in diameter and they discharge rejects intermittently instead of continuously.
What is a junk trap?
A junk trap is a relatively small chamber at the bottom of a HD centrifugal cleaner which continuously collects high density contaminants. Periodically it is isolated from the cleaner to discharge collected reject material.
How does feed consistency affect high density cleaners?
HD cleaner efficiency improves as the feed consistency decreases. Unfortunately, decreasing consistency reduces overall throughput.
What is elutriation water?
Elutriation water is small stream of flushing water which enters the cleaner through the junk trap. Its purpose is to prevent fiber from accumulating and plugging the trap.
Sample Video Transcript
Pressure drop refers to the difference between the feed pressure, and the accepts pressure. And it directly relates to how fast the slurry rotates inside the cleaner. The higher the pressure drop, the faster the slurry rotates, and the more centrifugal force is applied to the heavy contaminants. If the pressure drop is too low, the slurry will rotate too slowly, and contaminant removal will suffer. If the pressure drop is too high, the slurry will pass too quickly through the cleaner, and cleaning efficiency will suffer. A high flow rate also increases wear in a cleaner. This is why it is important to maintain the pressure drop through a cleaner at or near its design level.
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