Valkeakoski, Finland
Valkeakoski, Finland

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Muhic D.,Metso Paper Refiner Segments | Huhtanen J.-P.,Tampere University of Technology | Sundstrom L.,Holmen Paper AB Braviken Paper Mill | Sandberg C.,Holmen Paper AB Braviken Paper Mill | And 3 more authors.
Nordic Pulp and Paper Research Journal | Year: 2011

The goal with this work was to study the effect of segment design on electrical energy consumption and pulp quality in double disc TMP production. Mill scale trials were performed with refiner segments from Metso, which were designed based on the fluid dynamics theory. The calculated intensity for the different segments was related to the measured pulp quality. Refining with the high intensity segments (Turbine™) produced pulp with similar tensile index and a significantly higher specific light scattering coefficient at certain specific energy consumption when compared with the reference segments. One drawback with the high intensity segments was the limited operating window due to fibre cutting. The trials showed that segment performance can be modelled, which facilitates the development of new segment designs.


Rantamaki J.,Metsa Fibre Oy | Isokangas A.,University of Oulu | Ala-Kaila K.,Metsa Fibre Oy | Honkanen T.,Metso Paper Oy
Nordic Pulp and Paper Research Journal | Year: 2014

Wood raw material needs to be debarked before further processing in pulp and paper mills. However, the debarking process may cause wood raw material loss of up to 5%. The log loading step of the debarking process is essential in this sense to minimize any raw material loss. In a medium-sized pulp mill, the economic potential of debarking wood loss minimization is 700 000 USD/annum for every wood loss percentage point reduced. Seven methods to estimate the goodness of log loading were developed and tested first with simulated data to verify their usefulness. In the second stage, the methods were applied to mill data to find out their capability in a more challenging environment. The methods tested can detect differences between simulated cases as well as between different mills and mill cases. Mill data contains more disturbances and measurement noise than simulated data. Five of the methods can be applied in mill production control. A combination of two to three methods is recommended. When applying methods to mill production data, special attention needs to be paid to tuning the equation parameters. After implementing an appropriate method, the evenness of log loading will be easier to monitor and maintain. © 2014, SPCI. All rights reserved.


Tuovinen O.,Metso Paper Oy | Bjorkqvist T.,Tampere University of Technology | Fardim P.,Åbo Akademi University
O Papel | Year: 2013

Groundwood processes (GW, PGW) are among the major processes for mechanical pulping. Its major advantage over Thermomechanical pulping process (TMP) is lower requirement of electrical energy. Pulp stone (grinding wheel) plays a central role in groundwood process. The pulp stone consists of vitrified ceramic surface made of aluminium oxide grits. Condition of these grits on the pulp stone surface defines largely the pulp quality and energy consumption of groundwood process. Therefore, it is important to be able to quantify this kind of surfaces. This paper gives an introduction to the principle of automatic 3D reconstruction of surfaces from stereoscopic images and evaluates its applicability in reconstruction of surfaces of grinding wheels as well as of single grits. The paper also gives an example of the interrelation between topographic changes in grinding surface and groundwood wood pulp properties. Based on the results, reconstruction of the topography by the application of stereo photogrammetry is considered a suitable method for detailed 3D visualisation and quantification of a pulp stone surface or single grits in them. Topographic changes obtained in a grinding wheel and grit, for instance by dressing or by grinding, can be visualised and quantified in detail by using stereo photogrammetry and high resolution SEM images. Stereo photogrammetry is applicable in the basic research of grinding surfaces and grinding grits. The fact that the preparation of specimens and the production of SEM micrographs require specific instruments and skills appears as a limitation of the applications. The authors intend to apply digital photogrammetry in future basic research of the groundwood processes. The main objective of these studies is to resolve interactions between the grinding grits and wood, including the impact on mechanical pulp quality and energy consumption. © 2013, Assoc. Tecnica Brasileira de Celulose e Papel. All rights reserved.


Taipale T.,Aalto University | Holappa S.,Kemira Oyj | Ahlgren J.,Kemira Oyj | Cecchini J.,Metso Paper Oy | Laine J.,Aalto University
Nordic Pulp and Paper Research Journal | Year: 2010

The adsorption of three high molar mass cationic Polyacrylamides on thermo mechanical pulp was studied. Three polyelectrolytes of different charge densities and three different pulp fractions were used. The adsorption experiments were conducted at long contact times under low shear conditions representing the equilibrium state, as well as at short contact times under high shear turbulence mixing representing industrial papermaking conditions. The time-dependence of the adsorption was studied by altering the sampling time in a standard Dynamic Drainage Analyzer. The amount of adsorption was analyzed by a polyelectrolyte titration method. The aim of this study was to find more fundamental information of the influence of pulp fractionation on adsorption phenomena. The results showed that, at long contact times under low shear conditions, the charge density of polyelectrolyte did not affect its adsorption amount at low dosages, but that the adsorbed amount was defined by the type of the pulp fraction. At higher polyelectrolyte dosages the adsorption was influenced by both the charge density of polyelectrolyte and the type of the pulp fraction. Generally, the different combinations of pulp fractions and polyelectrolytes had unique adsorption kinetics, which is an interesting finding in regard to their practical applicability.


Taipale T.,Aalto University | Holappa S.,Kemira Oyj | Ahlgren J.,Kemira Oyj | Cecchini J.,Metso Paper Oy | Laine J.,Aalto University
Nordic Pulp and Paper Research Journal | Year: 2010

A focused beam reflective measurement device was used to study the flocculation of three different fractions of thermo mechanical pulp. Three high molar mass linear chain cationic Polyacrylamides of different charge densities were used as flocculants. The polyelectrolyte dosage and stirring speed was altered, and the change in the particle size was recorded. It was found that the type of pulp fraction significantly affected the flocculation process. Especially the short fraction had unique flocculation properties in comparison to the long fraction. The shear rate was also an important factor determining the flocculation phenomena. Under low shear conditions floes developed and degraded slower but were more sensitive to overdose than under high shear conditions. By utilizing the fractionation of pulp suspension, and by optimizing the polyelectrolyte type and dosage individually for each fraction, new possibilities for industrial process enhancement can be introduced.

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