In this study, the causes of tube thinning in the economizer of an ammonia-based spent sulfite liquor (SSL) boiler in a Canadian pulp mill are investigated. The tube thinning was most severe in the upper tube rows of the lowest economizer sections where the tube surface temperature ranges between about 180 degrees C and 210 degrees C. The location, the temperature range, and the results of a tube failure analysis indicate that some form of corrosion-erosion is the main cause for the tube thinning. The process is likely initiated by the formation of potassium bisulfate in tube deposits. We hypothesize that some areas in the economizer, including gaps in tube shields, have allowed for temporary buildup of deposits that were not fully removed by sootblowing. Potassium bisulfate is highly hygroscopic, so it readily absorbs moisture, forming an acidic solution leading to corrosion. The corrosion products are removed by the erosive effects of high velocity gas movement, causing the tube thinning. The high-speed fluid flow may be a result of sootblower action and/or enhanced flue gas velocity due to channeling. The tube thinning eventually leads to perforation and leakage.
One of the less interrogated aspects of corrugated packaging are scoring and scoring profiles, the intentional localized crushing of flutes to accommodate package folding and closure. This study explores the effect of scoring parameters on box compression test strength (BCT) of two balanced corrugated boards. Scoring differences produced BCT that varied by 10% for one board and less for the other board. Parameters from 4-point bending of scored specimens showed some correlation with BCT, while eccentricity and torsion parameters had less correlation. Different scores produced BCT differences that were not strongly predicted by most standard tests in the current study, implying other tests may be needed to examine the actual boundary conditions on a box during compression. In a few cases, aggressive scoring produced cracked score lines, and those containers had lower BCT than containers with uncracked score lines. Application: This study is the first to directly compare the impact of different flap scoring profiles on box compression strength. The impact of score cracking on box performance was clearly seen, with other impacts depending on material and requiring further exploration.
Miscanthus has emerged as a promising nonwoody fiber source for papermaking and fiber molding as the world has sought alternatives to wood-based products. A diverse range of chemistries have been explored at the laboratory scale to turn nonwoody biomass into fibers; however, few have been successful at pilot or commercial scales. An emerging organosolv delignification chemistry that has demonstrated previous technical success is butanol/water, having been shown to produce papers with similar properties to other, more conventional chemistries, but offering the benefit of a built-in sugar and lignin coproduct separation. While a range of fiber lengths were achieved (0.45-0.95 mm), addition of sodium hydroxide (NaOH) to the butanol/water delignification chemistry resulted in fiber lengths comparable to commercially available hardwood pulps (0.7-1.0 mm). Lignin concentration was reduced from 19.1 wt% in the raw miscanthusto under 3.5 wt% for most trials. The lowest lignin concentration (2.5 wt%) was achieved at 180 degrees C for 180 min with 50:50 butanol:water and 2 wt% acetic acid. Yet, the high severity of this condition (and similar ones) resulted in a significant truncation of fiber length, which is detrimental for paper-making applications. The highest quality pulp for papermaking was generated at 180 degrees C for 180 min with 50:50 butanol:water and 10 wt% NaOH. This pulp had one of the longest fiber lengths, the highest brightness, and the highest hemicellulose concentration. Thus, butanol/water delignification, especially with NaOH addition, resulted in the successful production of cellulose-rich pulps that have potential in commercial papermaking and fiber molding applications. Application: This study provides a fundamental investigation of how butanol/water delignification conditions, especially additives, influence the resulting fiber and pulp properties. This information can be used as a benchmark to help assess the potential of butanol/water delignification against more common pulping chemistries.
This study investigates the effects of refiner operating mode and refining intensity adjusted via pulp flow rate, applied power, and refiner speed on the refining characteristics of high-yield southern softwood. We compared Valmet's OptiFiner PRO (conical) and DD6700 (double disk) refiners under matched specific edge load (SEL) conditions. Batch and one-pass modes were evaluated for their impact on energy efficiency and physical paper properties. The results showed that while SEL provides a useful baseline, it does not fully account for differences in refiner geometry, particularly angular parameters. With the chosen plate sets, C-factor analysis revealed that the OptiFiner PRO delivers a lower number of fiber impacts at a higher intensity per impact compared to DD6700 at similar SEL, influencing fiber length, short-span compression test (STFI) index, and tear strength development. These findings offer actionable insights for mills seeking to optimize refining efficiency and cost. In summary, conical refiners may provide advantages in compression strength at mid-range energies, while double disk refiners maintain higher tear strength at elevated energies due to better fiber length preservation. Application: Readers can use the information in this study to gain a fundamental understanding of the similarities and differences between conical and double disk refining technologies, particularly in terms of energy efficiency and strength development for high yield southern softwood used in unbleached linerboard and kraft bag production. This research provides valuable insights for mills looking to update their machinery and improve their refining processes to reduce carbon footprint and enhance fiber strength.
The tissue, nonwovens, pulp, and technical textiles (TNPTT) sector offers products that enhance lifestyle, save lives, and protect the environment. Most TNPTT products are single use and semi-durable, and hence justin- style manufacturing and swift delivery influence pricing and consumption. While, as per some economists, tariffs and nontariff barriers are not enough to bring back commodity manufacturing, given the nature of manufacturing and applications of TNPTT products, this industry is robust. Boosting manufacturing, enabling new applications, enhancing R&D, and training the workforce will go a long way in growing these sectors. Advanced economies are well suited for investments due to technology requirements, research intensity, quality and regulatory requirements, and the consumer base.
