Return to Home Page
Gary M. Scott, Ph.D.
Faculty of Paper and Bioprocess Engineering
Empire State Paper Research Institute
State University of New York, College of Environmental Science and Forestry
The recycling of paper has become increasingly important over the past decade. The drivers of this change include both environmental and governmental forces. In papermaking, the drying process causes morphological changes in the paper fibers, which prevents rehydration and reduces the subsequent bonding ability of the fibers. Increased refining, while restoring the bonding ability, has a detrimental effect on the freeness and ability of the pulp to drain. The studies and literature reviews described below address these issues in order to increase the use of recovered paper worldwide.
A comprehensive literature review of the characteristics and uses of paper mill sludge was developed. This is an important topic because waste handling is a concern in all pulp and paper mills. It is especially critical in mills where secondary fiber is used. Sludge composition, separation, treatment, and disposal methods need to be addressed. This work explored the composition of sludge resulting from the pulp and papermaking process and compared secondary fiber and virgin fiber operations. The residue from separate operations was characterized, indicating the composition of the various waste streams in the mill. Alternative disposal methods were discussed in reference to these characteristics. The conclusion of the review was that the final sludge use could be based on its characterization, resulting in more efficient use of the residue.
A review of the current technology for fiber fractionation is given. The processing equipment available for fiber fractionation is discussed alongwith the grades of recovered paper that are considered candidates forfractionation. Because the fiber fractions often have distinctly dissimilar properties, they react differently to the various operations such as cleaning or bleaching. The work here also addresses the characterization of the fractions, modelling of fractionation, discusses other recycling operations, and the effect of fractionation on fiber properties. Other work, cited below, discusses the effect of recycling operations on contaminant removal.
Copyright 2001, Gary M. Scott. All rights reserved.