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Continuous digester rapid thinning, TAPPI Journal June 2024
ABSTRACT: Carbon steel continuous digesters built after the early 1980s are fully stress relieved, so stress corrosion cracking has been less of a concern. However, these newer digesters were designed to run modified cooking processes that have turned out to be much more corrosive than those running with conventional cooking. This corrosion is mainly associated with softwood digesters and appears to be flow related. Average corrosion rates of 40 mil/year are possible on the exposed shell between the wash and extraction screens. The corrosion patterns are visually distinct from surfaces in the upper digester and below the wash screens. This paper goes into practical detail on where it occurs, the causes, visual identification, inspection planning and results evaluation, and finally, how to mitigate this damage, which consists of applying a corrosion resistant barrier. Some discussion on dealing with general corrosion throughout the digester is included.
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.
Journal articles
Magazine articles
Displacement washing of softwood pulp cooked to various levels of residual lignin content, TAPPI Journal September 2021
ABSTRACT: This study investigates the influence of the degree of delignification of kraft spruce pulp cooked at seven different kappa numbers, ranging from 18.1 to 50.1, on the efficiency of displacement washing under laboratory conditions. Although the pulp bed is a polydispersive and heterogeneous system, the correlation dependence of the wash yield and bed efficiency on the Péclet number and the kappa number of the pulp showed that washing efficiency increased not only with an increasing Péclet number, but also with an increasing kappa number. The linear dependence between the mean residence time of the solute lignin in the bed and the space time, which reflects the residence time of the wash liquid in the pulp bed, was found for all levels of the kappa number. Washing also reduced the kappa number and the residual lignin content in the pulp fibers.
Journal articles
Magazine articles
Kingsport Celebrates Its Centennial, Paper360º November/Dec
Kingsport Celebrates Its Centennial, Paper360º November/December 2016
Magazine articles
Where, oh where, have the engineers gone?, Solutions!, October 2004, Vol. 87(10) (176KB)
Where, oh where, have the engineers gone?, Solutions!, October 2004, Vol. 87(10) (176KB)
Magazine articles
Improving Fiber Yield with Borate Autocausticizing, Solutions!, April 2005, Vol. 88(4) (88KB)
Improving Fiber Yield with Borate Autocausticizing, Solutions!, April 2005, Vol. 88(4) (88KB)
Magazine articles
If Itâ??s "Broke," Fix it With Coagulants, Solutions!, August 2005, Vol. 88(8) (196KB)
If It’s "Broke," Fix it With Coagulants, Solutions!, August 2005, Vol. 88(8) (196KB)
Magazine articles
What You Need to Know About Starch in Papermaking, Solutions!, August 2005, Vol. 88(8) (160KB)
What You Need to Know About Starch in Papermaking, Solutions!, August 2005, Vol. 88(8) (160KB)
Magazine articles
Were they making rack suits at tuxedo park?, Solutions!, November 2003, Vol. 86(11) (81KB)
Were they making rack suits at tuxedo park?, Solutions!, November 2003, Vol. 86(11) (81KB)
Magazine articles
The modern paper machine, part 1: bigger, better board machines, Solutions!, November 2003, Vol. 86(11) (604KB)
The modern paper machine, part 1: bigger, better board machines, Solutions!, November 2003, Vol. 86(11) (604KB)