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Journal articles
Magazine articles
Effects of hydrodynamic shear during formation of paper sheets with the addition of nanofibrillated cellulose, cationic starch, and cationic retention aid, TAPPI Journal September 2024
ABSTRACT: Laboratory tests were conducted to evaluate effects of hydrodynamic shear levels on papermaking process variables and paper handsheet properties. The furnish was from 100% recycled copy paper, to which was added nanofibrillated cellulose (NFC) at the 5% level following its optional pretreatment with cationic starch. A cationic copolymer of acrylamide (cPAM) was used as the retention aid. Different levels of hydrodynamic shear were applied both after mixing the NFC with the cationic starch (pre-shearing) or after all the furnish components had been combined (final shearing). The presence or absence of pre-shearing was found to have little effect on the measured outcomes. By contrast, increasing final shear hurt filler retention and made the resulting paper more uniform. However, the final shear level did not have a significant effect on the tensile strength of the resulting handsheets. Medium-charge density cationic starch, used in pretreating the NFC, consistently gave greater strength in comparison to a high-charge cationic starch. The significance of these findings is that though the relatively high hydrodynamic shear levels associated with modern paper machines can have some beneficial effects, they do not necessarily overcome all challenges associated with wet-end addition of nanocellulose in combination with other additives.
Journal articles
Magazine articles
Flocculation of fiber suspensions studied by Rheo-OCT, TAPPI Journal September 2024
ABSTRACT: When dealing with papermaking fiber suspensions, particle flocculation takes place even before the paper web is formed. The particle flocculation depends on several aspects, including particle mass concentration (consistency), particle collisions, electrochemical interactions promoted by chemical additives, etc. Due to its importance, fiber suspension flocculation has been studied for a long time in papermaking, and several methods have been developed for this purpose. The traditional techniques include, for example, focused beam reflectance microscopy (FBRM) and high-speed video imaging (HSVI). Recently, a new optical method, optical coherence tomography (OCT), has emerged for flocculation analysis. The advantages of OCT are the possibility to study opaque suspensions, its micron-llevel resolution, and its high data acquisition speed. The OCT measurements can be combined with rheological (Rheo) measurements, allowing simultaneous measurement of both the time evolution of the floc size and the suspension viscosity. In this work, we used this approach, Rheo-OCT, to study the flocculation of suspensions of various papermaking furnishes. We analyzed the time evolution of the floc size and the fiber suspension viscosity when the studied papermaking suspensions were treated with highly refined furnish (HRF) — a furnish that contained a significant amount of micofibrillated cellulose (MFC)-type fibrils — and/or chemical additives. Such studies can lead to a better understanding of the impact of flocculation on the produced paper web in terms of qualities like formation, drainage potential, and strength behavior.
Journal articles
Magazine articles
Experiments and visualization of sprays from beer can and turbo liquor nozzles, TAPPI Journal February 2022
ABSTRACT: Industrial scale swirl-type black liquor nozzles were studied using water as the test fluid. Simple water spraying experiments were found to be very beneficial for studying and comparing nozzles for black liquor spraying. These kinds of experiments are important for finding better nozzle designs. Three nozzle designs were investigated to understand the functional differences between these nozzles. The pressure loss of nozzle 1 (“tangential swirl”) and nozzle 3 (“turbo”) were 97% and 38% higher compared to nozzle 2 (“tan-gential swirl”). Spray opening angles were 75°, 60°, and 35° for nozzles 1, 2, and 3, respectively. Video imaging showed that the nozzles produced sprays that were inclined a few degrees from the nozzle centerline. Spray patter-nation showed all the sprays to be asymmetric, while nozzle 2 was the most symmetric. Laser-Doppler measure-ments showed large differences in spray velocities between nozzles. The spray velocity for nozzle 1 increased from 9 m/s to 15 m/s when the flow rate was increased from 1.5 L/s to 2.5 L/s. The resulting velocity increase for nozzle 2 was from 7 m/s to 11 m/s, and for nozzle 3, it was from 8 m/s to 13 m/s. Tangential flow (swirl) directed the spray 6°•12° away from the vertical plane. Liquid sheet breakup mechanisms and lengths were estimated by analyzing high speed video images. The liquid sheet breakup mechanism for nozzle 1 was estimated to be wave formation, and the sheet length was estimated to be about 10 cm. Sheet breakup mechanisms for nozzle 2 were wave formation and sheet perforation, and the sheet length was about 20 cm. Nozzle 3 was not supposed to form a liquid sheet. Nozzle geometry was found to greatly affect spray characteristics.
Magazine articles
Experiences of safety analyses in the pulp and paper industry, TAPPI JOURNAL, May 1993, Vol. 76(5)
Experiences of safety analyses in the pulp and paper industry, TAPPI JOURNAL, May 1993, Vol. 76(5)
Magazine articles
A visit to mount st. helens; meta lake illustrates natural recovery following volcanic eruption, TAPPI JOURNAL, April 1994, Vol. 77(4)
A visit to mount st. helens; meta lake illustrates natural recovery following volcanic eruption, TAPPI JOURNAL, April 1994, Vol. 77(4)
Magazine articles
The epa's process safety management program for preventing accidental chemical releases (40 cfr 68), TAPPI JOURNAL, April 1994, Vol. 77(4)
The epa's process safety management program for preventing accidental chemical releases (40 cfr 68), TAPPI JOURNAL, April 1994, Vol. 77(4)
Magazine articles
Suction roll pilot bearing failure due to inadequate lubrication, TAPPI JOURNAL, December 1994, Vol. 77(12), TAPPI JOURNAL, December 1994, Vol. 77(12)
Suction roll pilot bearing failure due to inadequate lubrication, TAPPI JOURNAL, December 1994, Vol. 77(12), TAPPI JOURNAL, December 1994, Vol. 77(12)
Magazine articles
1994 TAPPI nonwovens conference, TAPPI JOURNAL, July 1994, Vol. 77(7)
1994 TAPPI nonwovens conference, TAPPI JOURNAL, July 1994, Vol. 77(7)
Magazine articles
China paper technical program and exhibit came of age in 1995, TAPPI JOURNAL, March 1996, Vol. 79(3)
China paper technical program and exhibit came of age in 1995, TAPPI JOURNAL, March 1996, Vol. 79(3)
Magazine articles
1995 Finishing and Converting Conference: Taking advantage of changing trends, TAPPI JOURNAL, March 1996, Vol. 79(3)
1995 Finishing and Converting Conference: Taking advantage of changing trends, TAPPI JOURNAL, March 1996, Vol. 79(3)