| 1. |
- Brännvall, Elisabet, et al.
(författare)
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Separate bleaching of pulp fractions enriched in earlywood and latewood fibers
- 2007
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Ingår i: Journal of wood chemistry and technology. - : Informa UK Limited. - 0277-3813 .- 1532-2319. ; 27:2, s. 99-112
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Tidskriftsartikel (refereegranskat)abstract
- Unbleached softwood kraft pulp was fractionated in hydrocyclones into a fine fraction, enriched in earlywood fibers, and a coarse fraction, enriched in latewood fibers. The response to individual bleaching chemicals and the bleachability in bleaching sequences of the pulp fractions was studied. The light absorption coefficient, light scattering coeffient, and brightness were higher in the unbleached fine fraction than in the coarse fraction. Hydrogen peroxide managed to reduce the light absorption coefficient of the earlywood enriched fine fraction more efficiently than that of the latewood enriched fraction. In the TCF-sequence the light absorption coefficient of the fine fraction was reduced to the level of the coarse fraction at a given consumption of bleaching chemicals. In the ECF-sequence the difference in light absorption coefficient remained between the fractions. At a given consumption of bleaching chemicals, the fine fraction had higher brightness than the coarse fraction, 2%- and 1%-units on the ISO-scale in the TCF and ECF bleaching sequence, respectively.
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| 2. |
- Bäckström, Marie, et al.
(författare)
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Studies of the influence of deflocculants and flocculants on the refining efficiency on a pilot scale
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 24:3, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present investigation was to study the influence of flocculants and deflocculants on refining efficiency. The refining was performed with the aid of a conical refiner at EuroFEX, and the refining response was evaluated as the change in fibre properties and in the mechanical properties of handsheets. Using the same furnish, an unbleached never-dried softwood pulp, the effect of fibre dimensions on floe strength was excluded as much as possible. The degree of flocculation was changed by addition of APAM, CPAM, guar gum and CMC. The floe strength was characterized using a parallel plate rheometer. The added chemicals, except for APAM, affected the relation between power input and gap clearance. To reach a certain power the fibres treated with guar gum, CMC or CPAM required a narrower gap clearance than the reference pulp or when APAM was added to the fibres. Refining at a narrower gap clearance increased the refining efficiency in terms of WRV and paper property development, as long as fibre length reduction could be avoided.
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