| 1. |
- Engberg, Birgitta, et al.
(författare)
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Mechanical properties of sulphonated wood in relation to wing refiner properties
- 2014
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Ingår i: International Mechanical Pulping Conference, IMPC 2014. - Espoo : Paper Engineers' Association (PI).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To reach maximum effect of different pretreatments we need to know how wood properties can be changed and how this can be related to both refining conditions and pulp characteristics. To understand how the material properties were affected, sulphonated wood samples were tested using several new testing techniques. The data was correlated to pulp properties of batch refined chips to learn more how the initial defibration mechanisms and pulp properties were affected by the pretreatments.
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| 2. |
- Fjellström, Helena, et al.
(författare)
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Predicting CTMP bleachability using wood shavings
- 2011
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Ingår i: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC. ; , s. 613-616
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Konferensbidrag (refereegranskat)abstract
- To predict the brightness reduction in a chemithermomechanical process as well as the bleachability of pulps produced from different species of wood raw materials there are, at present, no shortcuts available. Pulps have to be manufactured in pilot or mill scale and bleached; evaluating and predicting the bleachability has consequently been very resource consuming and thus expensive - until now! Due to this, we have used a laboratory method based on 60 × 60 mm wood shavings making it possible to predict the bleachability of primarily chemithermomechanical pulps but also other mechanical pulps. Our experiments showed that retention time and impregnation temperature appears to have no impact on the final brightness of birch shavings. When being subjected to a simulated chemithermomechanical pulp process, eucalyptus exhibited an increase in chromophore content before the bleaching stage. In addition, eucalyptus suffered from severe alkaline darkening. After the bleaching stage, the alkaline darkening diminished. A higher retention temperature resulted in lower brightness of the eucalyptus shavings compared to when using a lower retention temperature. Birch reached the highest final brightness levels and had a higher overall yield too.
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| 3. |
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| 4. |
- 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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| 5. |
- Logenius, Louise, et al.
(författare)
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A sustainable analysis of sulphonic acid content in CTMP pulps
- 2014
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Ingår i: International Mechanical Pulping Conference, IMPC 2014, part of PulPaper 2014 Conference. - Espoo : Paper Engineers' Association (PI).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sulphonic acid analyses were performed on wing refiner chemithermomechanical pulps, low sulphite charge pulps, thermomechanical pulps and on wood samples using a new method referred to as the niacin method. This method gives sulphonic acid content comparable to those estimated with the quinoline method or the Schoniger method. The method gives low interference with carboxylic acids and dissolved substances in the pulp if the pH is kept sufficiently low and the pulp is well washed.
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| 6. |
- Logenius, Louise, et al.
(författare)
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High temperature bleaching of mechanical pulps from spruce
- 2005
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Ingår i: Proceedings, International Mechanical Pulping Conference, 7-9 June, 2005, Oslo, Norway. ; , s. 80-84
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A laboratory method was developed, which facilitates to investigate how the temperature profile during a TMP-process including a bleaching stage influences pulp brightness. Thin shavings are prepared by slicing a fresh and frozen block of wood with a microtome. The shavings are rapidly dried in an air-stream at room temperature and the optical properties are measured in an Elrepho instrument. After that the shavings are placed in a stainless steel container that can be pressurized with steam, where the temperature profile in a TMP-process or a bleach plant can be simulated. Addition of bleaching chemicals can be done during the simulation. The optical properties are measured and can be compared to those of the same shaving before treatments. The temperature profile in a TMP-process has a large impact on the optical properties of the pulp. Many studies have been done to show how brightness is affected, when temperature/pressure in TMP processes are varied. However, pilot-scale or full scale-trials can often be performed only under certain limitations. With this new method it is easy to simulate different processing conditions and measure the kinetics of the brightness change on a shaving sample before and after treatments. To get as high final brightness as possible it is necessary to limit the brightness reduction as much as possible in manufacturing of the unbleached pulp.
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| 7. |
- Logenius, Louise, et al.
(författare)
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High-Temperature Bleaching of Mechanical Pulps from Spruce
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- High-temperature (HT)-peroxide bleaching of a thermomechanical pulp made of Norwegian spruce was investigated; to that end, one-stage reference bleaching at 70°C and one- and two-stage bleaching at 105°C at different total alkali charges (TAs) using a wing defibrator as a mixer were performed. Two-stage HT peroxide bleaching produces a brighter pulp than one-stage HT peroxide bleaching does. The TA should be kept low (10�15 kg/t) and the total alkali/peroxide ratio should be low in the first stage to minimize the COD load and obtain higher residual peroxide. Increased TA does not improve brightness. The bleaching time in HT bleaching at 105°C can be short, since the maximum brightness is reached after only 2.5 min.Preimpregnation of the pulp with hydrogen peroxide before a two-stage alkali addition can produce a pulp with a brightness and residual peroxide comparable to those obtained in conventional one-stage peroxide bleaching at the same hydrogen peroxide charge and at a low TA. The COD load was, however, higher than in conventional bleaching
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| 8. |
- Logenius, Louise, et al.
(författare)
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High-Temperature Bleaching of Mechanical Pulps from Spruce
- 2007
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Ingår i: Proceedings. Internationl mechanical pulping conference 6-9 May, 2007, Minneapolis, MN, USA. - : TAPPI Press. - 9781605602936 ; , s. 580-587
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Konferensbidrag (refereegranskat)abstract
- High-temperature (HT)-peroxide bleaching of a thermomechanical pulp made of Norwegian spruce was investigated; to that end, one-stage reference bleaching at 70°C and one- and two-stage bleaching at 105°C at different total alkali charges (TAs) using a wing defibrator as a mixer were performed. Two-stage HT peroxide bleaching produces a brighter pulp than one-stage HT peroxide bleaching does. The TA should be kept low (10�15 kg/t) and the total alkali/peroxide ratio should be low in the first stage to minimize the COD load and obtain higher residual peroxide. Increased TA does not improve brightness. The bleaching time in HT bleaching at 105°C can be short, since the maximum brightness is reached after only 2.5 min. Preimpregnation of the pulp with hydrogen peroxide before a two-stage alkali addition can produce a pulp with a brightness and residual peroxide comparable to those obtained in conventional one-stage peroxide bleaching at the same hydrogen peroxide charge and at a low TA. The COD load was, however, higher than in conventional bleaching.
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