| 1. |
- Ala-Kaila, K., et al.
(författare)
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Chemical character of the response of softwood kraft pulp towards industrial two-stage oxygen-alkali delignification
- 2004
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Ingår i: Paperi ja puu. - 0031-1243. ; 86:5, s. 353-358
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Forskningsöversikt (refereegranskat)abstract
- The transient behavior of residual material affecting the kappa number of softwood kraft pulp (termed residual lignin), was tested experimentally step-wise in an industrial two-stage oxygen-alkali delignification process. The behavior was characterized by leaching the pulps and dividing the residual lignin into four different fractions to represent the wash loss fraction, the easily leachable fraction, the slowly leachable fraction and the stagnant fraction of the lignin in pulp. Further characterization was made regarding the chemical character of these fractions, i.e. residual lignin, extractives, hexenuronic acid, and other chemical structures that contribute to the kappa number of the pulps. The componential delignification response in the two oxygen-alkali reactors and the effects of the leaching operation were comprehensively assessed regarding the behavior of these different pulp components. The results were compared with results obtained earlier for birch kraft pulp originating from the same industrial process and treated using identical experimental procedures. Application: This study gives a new perspective with which to evaluate apparent and actual responses in industrial oxygen-alkali delignification of kraft pulps.
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| 2. |
- Björk, Anders, et al.
(författare)
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Applied Real-Time Acoustic Chemometrics for Measurements of Canadian Standard Freeness
- 2005
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Ingår i: Paperi ja puu. - 0031-1243. ; 87:7, s. 452-457
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a method for measuring Canadian Standard Freeness (CSF) on-line in real-time using acoustic measurements. The method can be used to present a new CSF value every second. The higher measurement rate and the reduced time-delay compared to conventional pulp sensors make it a suitable tool for improved refiner control. The method was developed during full-scale trials on two separate Sunds Defibrator double disc refiners at SCA Ortviken, Sweden. Acoustic measurements were performed using an accelerometer affixed to the refiner blow line. Trial conditions have been varied over a wide range of pulp quality and disturbances in the vibration signal. CSF was for example varied in the range 62-453 ml and refiner-housing pressure was varied from 0,35 to 0,39 MPa. The vibration signals collected during I second were treated to yield power spectra that were used for all further work. A median spectrum was calculated for each experimental point and these spectra were combined with reference values for freeness to make up the calibration matrices. The spectra were pre-treated using Orthogonal Signal Correction (OSC) and Subsequently Partial Least Squares Regression (PLSR) was used to build models between spectra and freeness. For model validation leave-one-out cross validation has been used. Over the range 90-250 ml we can predict CSF from median power spectra with a Root Mean Square Error of Prediction (RMSEP) of 23 ml. Over the larger CSF range of 62-453 mt the RMSEP deteriorates to 39 mt. Data from two separate trials on different refiners and from different seasons were included in these models.
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| 3. |
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| 4. |
- Gustafsson, Roland, et al.
(författare)
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Influence of the alkalinity in polysulphide pretreatment on results of cooking with normal liquor-to-wood ratios
- 2004
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Ingår i: Paperi ja puu. - 0031-1243. ; 86:3, s. 169-173
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Tidskriftsartikel (refereegranskat)abstract
- The effect of alkalinity in a polysulphide pretreatment on the delignification rate, pulp yield and the pulp viscosity in the following kraft cook was investigated. The results were compared to those with reference pretreatments with a corresponding concentrations of hydroxide and hydrogen sulphide ions. The experiments were carried out at liquor-to-wood ratio of 4:1, and the alkalinity in the pretreatments was varied from 0 to 2.5 mole hydroxide/litre. It was found that when the polysulphide preteatment is performed at very high initial hydroxide concentrations, > 1.5 mole/litre, the delignification rate in the cook is increased. The pulp viscosity was higher than that achieved with the sulphide reference when the pulping was extended to low kappa numbers and when the initial hydroxide ion concentration in the pretreatment was high.
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| 5. |
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| 6. |
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| 7. |
- Lilja, Kari, et al.
(författare)
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The case of the forest-based sector technology platform
- 2008
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Ingår i: Paperi ja puu. - 0031-1243. ; 90:2, s. 29-33
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The forest sector has taken significant steps at the European level to improve its engagement in large-scale European-wide research programmes. As part of the preparation of the 7th Framework Program, the forest sector made use of a new research policy tool, called Technology Platform (TP). This tool was launched by the European Union (EU) to get companies, industries, and sectors to become more involved in the funding and implementing of research programmes in cooperation with universities and research institutes.
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| 8. |
- Logenius, Louise, et al.
(författare)
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A study of the formation and elimination of chromophores in wood under mechanical pulping conditions using spectroscopy
- 2010
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Ingår i: Paperi ja puu - Paper and timber. - 0031-1243. ; 92:5, s. 35-39
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Tidskriftsartikel (refereegranskat)abstract
- Thin sections of wood, i.e., shavings, were used in spectroscopic measurements studying the formation and elimination of chromophores under mechanical pulping conditions. Light absorption coefficients, light scattering coefficients, and brightness were monitored.The method was applied to study how temperature in the absence of mechanical energy affects wood brightness. An increase in absorption coefficient at 420 nm indicates formation of ortho-quinone structures. By applying mechanical pulp processing conditions, the light absorption coefficient increased in the 400-500-nm wavelength region, probably due to the formation of chromophores in the lignin. Comparison of heat treated wood shavings with mechanical pulps indicated that additional chromophores were created during the mechanical pulping processes.The method was also used in studying how high-temperature hydrogen peroxide bleaching of the wood shavings affects the light absorption coefficients. The light absorption spectra reveal information about chromophore elimination in wood chemical components during hydrogen peroxide bleaching at slightly pressurized conditions. This is relevant to processes, such as the alkaline peroxide mechanical pulp process, in which the wood chips are impregnated with bleaching chemicals before refining. The easy penetration of chemicals into the wood shavings ensures rapid and even distribution of the treatment chemicals. A change in light absorption coefficient at shorter wavelengths (400-500 nm) was observed.
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| 9. |
- Nilsson, David, et al.
(författare)
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Prediction of thermo mechanical pulp brightness using NIR spectroscopy on wood raw material
- 2005
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Ingår i: Paperi ja puu. - Helsinki : Suomen Paperi- ja Puutavaralehti Oy. - 0031-1243. ; 87:2, s. 102-109
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Tidskriftsartikel (refereegranskat)abstract
- Partial Least Squares regression to latent structures was used to find a correlation between near-infrared reflectance spectra of samples of milled Norway Spruce (Picea abies) and ISO brightness of bleached thermo mechanical pulp. Logs of spruce were stored in climate chambers with different conditions for 14 weeks. A factorial design based on five variables was constructed to control the storage and to provide different brightness properties of the stored spruce logs. Wood samples were collected during the storage and they were analysed with near-infrared reflectance spectroscopy and later refined to thermo mechanical pulp. The pulp was bleached with both hydrogen peroxide and sodium dithionite. The ISO brightness of the bleached pulp was correlated to the near-infrared spectra of the untreated samples using Partial Least Squares regression to latent structures. The modelling showed that it is possible to predict the ISO brightness of bleached thermo mechanical pulp from near-infrared spectra of original wood raw material.
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| 10. |
- Nohlgren, I., et al.
(författare)
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Conversion of sulfur during pressurized pyrolysis and gasification of black liquor with direct causticization using titanates
- 2005
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Ingår i: Paperi ja puu. - 0031-1243. ; 87:4, s. 259-263
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Tidskriftsartikel (refereegranskat)abstract
- The release of sulfur during gasification and pyrolysis of black liquor in the presence of sodium titanates was investigated using a pressurized, entrained-flow reactor. The reaction conditions were temperatures of 900°C, 950°C and 1000°C, at pressures of 0.5 MPa and 1 MPa and in atmospheres of pure N2 or N2 with 2% CO2. Conversion of up to 35% of the sulfur in black liquor to gases was obtained within 5 seconds at these conditions. More of the sulfur in black liquor was converted to gases when CO2 was present than when not. More of both H2S and COS were produced in the presence of CO2 than in pure N2. Very little CS2 was produced in either case. The fraction of the sulfur in black liquor that was volatilized did not vary significantly with gasification pressure.
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