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WorksheetsUAS Pulp Tech1
Total questions: 20
Worksheet time: 10mins
Proses of Wood Chip refining is , Kecuali:
separate fibers from each other in the wood material.
The fibers are separated and worked by the compressive and shearing stress forces in the refiner
Fiber is compacted
Fiber separation and Further refining
The refiner segments are an important factor in refiner operations and the quality of the pulp produced.
True
False
In most refiners, the segments are attached to segment holders, When replacing the segments, they are replaced not including the segment holders.
True
False
The strongest remedy for improving the pulp quality or raising the mill capacity is the refiner segments. They affect, kecuali:
Capacity and pulp quality
Refining energy consumption
Refiner runnability
Refiner error
The first stage of refining wood material is heated and its structure is loosened by compressive forces. Steam is generated, The wood material disintegrates into fiber bundles, separate fibers, and fiber constituents due to the shearing forces (frictional forces) between the refiner segments.
True
False
Refining affects fibers in many ways. Kecuali:
–Removal of primary fiber wall which prohibits fiber swelling because of its rigidity.
–Internal and external fibrillation detach and break the fibrils so that the fiber surface becomes hairy.
–Delamination and swelling of fibers.
Shortening of fibers.
Creation of fines.
Fiber un fibrillated
Refining intensity impact, kecuali
Gap between refining plates
Fibers are collapsed and their bonding surface area is increased.
Depending on the intensity of refining, fibers can be more fibrillated or shortened.
Correct refining intensity gives fibrillated fibers while too severe refining intensity produces more cut fibers.
Process variables affecting chip refining's, kecuali:
Refining consistency
Inlet pressure
Housing pressure
Inlet temperature
Chip preconditioning
Wood species
Raw material Variables affecting chip refining, kecuali:
Wood species
–Variations between each forest will exist
Age of wood
–Should not be more than six weeks old.
Refiner segment pattern
Chip size and quality
–Determined by the condition of the chipper knives and the wood.
Definition of Fiber sheet Brightness, Brightness is a function of a surface's ability to scatter(s) and absorb (k) light!
Benar
Salah
Specific light scattering coefficient, s
The indexed ability for reflection of light. The light scattering is generally increased by increased refining.
More refining = higher scattering
Benar
Salah
Specific light absorption coefficient, k
The indexed ability for absorption of light, Light absorption is mostly affected by the raw material and to some extent also by process conditions.
High bark content = high light absorption
Benar
Salah
Paperboard brightness is measured on a scale of 0 to 100.
Benar
Salah
Depending on the end product, BCTMP can be bleached to a brightness level of below 80% ISO.
Benar
Salah
The only way to increase brightness levels more than 5-10% ISO is to reduce the light absorption coefficient
Benar
Salah
In BCTMP process, the most commonly used bleaching chemical are Peroxide and Chlorine
Benar
Salah
The idea of bleaching BCTMP is to reduce the number of chromophores in the lignin.
Benar
Salah
Lignin gives the pulp its Bright color. Colored chromophore groups give lignin its color.
Benar
Salah
How to Bleach Pulps Containing Lignin? kecuali:
Remove the colored lignin
High yield loss bleaching
Reduce the number of chromophores in the lignin
lignin preserving bleaching - mechanical pulping
Bleaching Chemistry, chemicals used in Bleaching, kecuali:
Stabilizer
DTPA
Chlorine Dioxide
Caustic (Sodium hydroxide)
Hydrogen Peroxide
