The Effects of Retention Aid Dosage and Mechanical Energy Dissipation on Fiber Flocculation in a Flow Channel

Dosage;Paper properties;Flocculation;Basis weight.;Flocs;Formation;Image analysis;Optimization;Retention aids;Reynolds number;Suspension

Weseman, Brian D. ; Institute of Paper Science and Technology

University:Georgia Institute of Technology

Department:Institute of Paper Science and Technology

关键词: Dosage;    Paper properties;    Flocculation;    Basis weight.;    Flocs;    Formation;    Image analysis;    Optimization;    Retention aids;    Reynolds number;    Suspension;   

Others  :  https://smartech.gatech.edu/bitstream/1853/7960/1/Weseman%209490%20Thesis.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

Formation plays an important role in the end-use properties of paper products,but before formation can be optimized to achieve superior properties, an understandingabout the causes of formation must be developed. Formation is caused by variations inthe basis weight of paper that are results of fiber floc formation before and during theforming of the sheet. This project is a first step in a larger research program aimed atstudying formation. By observing the effects that mechanical energy dissipation (in theform of turbulence) and retention chemical dosage have on floc formation, we maydevelop a better understanding of how to control formation.In this study, a rectangular cross-section flow channel was constructed to aid inthe acquisition of digital images of a flowing fiber suspension. The furnish consisted of a55:45 spruce:pine bleached market pulp mix from a Western Canadian mill. Turbulencewas varied by changing the flow rate; Reynolds numbers achieved range from 20,000 to40,000. The retention aid used was a cationic polyacrylamide with a medium chargedensity. Dosage of the retention aid was varied from 0 to 2 pounds per ton OD fiber.Digital images of the flowing fiber suspension were acquired with a professional digitalSLR camera with a forensics-quality lens. Three separate image analysis techniques wereused to measure the flocculation state of the fiber suspension: morphological imageoperations, formation number analysis, and fast Fourier transform analysis.Morphological image analysis was capable of measuring floc size increases seen inthe acquired floc images. It was shown how floc diameter could increase simultaneouslywith decreasing total floc area and total floc number. A regression model relatingretention aid dosage and energy dissipation was constructed in an effort to predictflocculation. The regression model was used to predict F2 (formation number squared)results from the study. The interaction effect RE was shown to have a differing effect across the retention aid dosage levels. As a result, this model and technique may prove tobe a beneficial tool in optimizing retention aid applications.