Measurement and interpretation of spatially registered bar-forces in LC refining
-
Matthias Aigner
,
James Olson
Abstract
A high resolution rotary encoder and a piezo electric force sensor are implemented in a 16-inch laboratory-scale low consistency refiner to explore the effect of plate gaps on bar-force profiles. The sensor replaces a short length of a stator bar and measures normal and shear forces applied during the passage of each rotor bar. The rotary encoder data is used to locate the rotor bars relative to the stator bar in which the sensor is located. Previous work with this type of force sensor focuses primarily on the distribution of the maximum force measured during the passage of each rotor bar over the sensor or bar passing event, BPE. In this work, force profiles for bar passing events are registered to the position of rotor bars relative to the stator bar in which the sensor is located. These registered force profiles are measured for a range of plate gaps and two different pulp furnishes. The angular reference provided by the encoder makes it possible to generate mean force profiles. As force data for individual BPEs is highly variable, these mean force profiles have potential to shed light on the fundamental mechanisms of mechanical refining. For large gaps, there is a late peak in the force profiles that occurs toward the end of the bar passing event. For gaps that are less than the critical gap, below which fiber cutting occurs, there is an early peak in the force profiles that occurs at the start of the bar passing event. It is hypothesized that the early peak represents the corner force and, therefore, that corner force is causal in the onset of fiber cutting. To explore this hypothesis, a model is presented connecting corner force and friction force to the progression geometric variables during the bar passing event such as the bar edge length engaged at any point in the bar passing event and the area covered by the rotor bar on the force sensor at any point in the bar passing event.
Funding statement: This work is funded by a Collaborative Research and Development grant provided by National Sciences and Engineering Research Council of Canada (NSERC) and the following partners, who we thank for their ongoing support: AB Enzymes, Alberta Newsprint Company, Andritz, BC Hydro, Canfor, Catalyst Paper, FPInnovations, Holmen Paper, Meadow Lake Pulp (Paper Excellence), Millar Western, NORPAC, West Fraser, Westcan Engineering, and Winstone Pulp International.
Acknowledgments
The authors gratefully acknowledge the assistance of R. Seifert, M. Miller and G. Soong during the preparation and execution of the refining trials at the Pulp and Paper Center at UBC.
Conflict of interest: The authors declare no conflicts of interest.
Appendix A Timing of data and pulp sample acquisition
Table 2 describes the timing of data collection and pulp sample acquisition during trials.
Timing of data and pulp sample acquisition.
| Time | Action |
| 00:00:00 | Stable refining conditions reached, First data sample collection started |
| 00:00:01 | First data sample is collected Storing of first data sample is started |
| 00:00:03 | First data sample is written to memory, Second data sample is started |
| 00:00:04 | Second data sample is collected Storing of second data sample is started |
| 00:00:06 | Second data sample is written to memory, Third data sample is started |
| 00:00:07 | Third data sample is collected Storing of third data sample is started |
| 00:00:09 | Third data sample is written to memory |
| 00:00:10 | Pulp sample is collected from the collection position |
Appendix B Corner force and shear force models
Total bar force,
Mean peak normal force data for the softwood trials at plate gap 0.2 mm is used to generate separate force profiles for the corner force and the friction force following the relation described in Equation (5). Based on these individual force plots and using the engaged area for friction force and engaged length for corner force, separate stress profiles for the BPE are generated. These stress plots are fitted with trend lines.
It was found that corner force is the product of the engaged length,
Friction force is found to be the product of the engaged area,
Equations (5) to (7) where used to generate the combined force plot in Figure 12 (C). The values of the used constants are displayed in Table 3.
Values of constants used in friction force and corner force models.
| Constant | Value |
| 1.8 | |
| 3.4 | |
| 11.5 |
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Articles in the same Issue
- Frontmatter
- Review
- Evolution of biobased and nanotechnology packaging – a review
- Chemical pulping
- Evaluation of sodium salt scaling in black liquor evaporators using existing process data
- Assessing the value of a diversified by-product portfolio to allow for increased production flexibility in pulp mills
- Bleaching
- Effect of introducing ozone in elemental chlorine free bleaching of pulp on generation of chlorophenolic compounds
- Chlorine dioxide bleaching of nineteen non-wood plant pulps
- A solid-phase extraction method that eliminates matrix effects of complex pulp mill effluents for the analysis of lipophilic wood extractives
- Mechanical pulping
- Development of fibre properties in mill scale high- and low consistency refining of thermomechanical pulp (Part 1)
- Measurement and interpretation of spatially registered bar-forces in LC refining
- Paper technology
- Production of a fine fraction using micro-perforated screens
- The effect of Plantago psyllium seed husk flour on the properties of cellulose sheet
- Comprehensive evaluation of the industrial processing effects on the fiber properties of the pulps from wood residues
- Paper chemistry
- Application of CS-CHO-g-PMMA emulsion in paper reinforcement and protection
- Effects of metal ions and wood pitch on retention and physical properties of TMP
- Coating
- Effect of the glass-transition temperature of latexes on drying-stress development of latex films and inkjet coating layers
- Nanotechnology
- Study of LCNF and CNF from pine and eucalyptus pulps
- Miscellaneous
- The component composition of planted pine wood cultivated in the boreal zone
Articles in the same Issue
- Frontmatter
- Review
- Evolution of biobased and nanotechnology packaging – a review
- Chemical pulping
- Evaluation of sodium salt scaling in black liquor evaporators using existing process data
- Assessing the value of a diversified by-product portfolio to allow for increased production flexibility in pulp mills
- Bleaching
- Effect of introducing ozone in elemental chlorine free bleaching of pulp on generation of chlorophenolic compounds
- Chlorine dioxide bleaching of nineteen non-wood plant pulps
- A solid-phase extraction method that eliminates matrix effects of complex pulp mill effluents for the analysis of lipophilic wood extractives
- Mechanical pulping
- Development of fibre properties in mill scale high- and low consistency refining of thermomechanical pulp (Part 1)
- Measurement and interpretation of spatially registered bar-forces in LC refining
- Paper technology
- Production of a fine fraction using micro-perforated screens
- The effect of Plantago psyllium seed husk flour on the properties of cellulose sheet
- Comprehensive evaluation of the industrial processing effects on the fiber properties of the pulps from wood residues
- Paper chemistry
- Application of CS-CHO-g-PMMA emulsion in paper reinforcement and protection
- Effects of metal ions and wood pitch on retention and physical properties of TMP
- Coating
- Effect of the glass-transition temperature of latexes on drying-stress development of latex films and inkjet coating layers
- Nanotechnology
- Study of LCNF and CNF from pine and eucalyptus pulps
- Miscellaneous
- The component composition of planted pine wood cultivated in the boreal zone
