Date of Award

5-2012

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Advisor

David J. Neivandt

Second Committee Member

Douglas W. Bousfield

Third Committee Member

Joseph M. Genco

Abstract

This work examines the utilization of chemical means to enhance the amount of water removed in the papermaking process prior to the application of heat. Through wet end application of a cationic surfactant, a significant increase in the amount of water removed in the forming and pressing sections is observed. This results in a reduction in the energy required to thoroughly dry the paper.

A variety of compounds hypothesized to potentially enhance dewatering were examined. A cationic surfactant, cetyltrimethylammonium bromide (CTAB), produced significant enhanced dewatering via addition to a pulp slurry. Extensive bench top testing characterized the extent of reduction of water retention of a fiber mat in the presence of CTAB after being exposed to drainage and pressing operations. The addition of CTAB favorably altered the pore structure of the fiber mat and promoted dewatering. The laboratory work was successfully translated to the pilot scale. The addition of CTAB resulted in an increase in the rate of production of paper by 18%. Post trial analysis indicated that an additional 12% production increase may have been available that was unrealized during the pilot scale run. While the addition of CTAB had a dramatic affect on dewatering, several potentially negative effects were identified. Specifically, the fiber surface was shown to be charge reversed from negative to positive, the surface tension of the slurry was significantly reduced, the fiber sheet was considerably thicker, and the sheet strength was reduced by the addition of CTAB. Efforts to mitigate the negative effects observed in both the laboratory and pilot scale testing determined that the addition of an anionic clay reversed the bulking, charge, and surface tension effects, however it failed to recover the strength loss.

In conclusion, the work demonstrated that the addition of the cationic surfactant CTAB to a pulp slurry results in significant chemically enhanced water removal. The technology is expected to have direct application in niche markets which do not base product quality on strength or bulking. Additional implementation of the technology may be possible with further evaluation.

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