Basic Drainage Properties of Chinese Wheat Straw Pulp, 1994 Pulping Conference Proceedings

Z. Cheng, J. Leminen, K. Ala-Kaila, H. Paulapuro

The pulp and paper industry in China uses a wide range of raw material of both wood and non-wood origin. One of the most influential problems with non-wood fibers in pulping and papermaking is the slow drainage in different processes. This causes problems such as low production efficiency, poor pulp quality in pulping washing, and slow dewatering on the wire and press sections of the paper machine.

This experimental study examines the basic drainage properties of one of the Chinese non-wood fibers, wheat straw pulp and compares this to some Chinese wood pulps. The fiber material was mill produced pulp collected at various mills in China. Unbleached larch, southern pine, wheat straw and bleached wheat straw pulps were tested. The basic drainage properties such as compressibility, specific surface, specific volume, and Schopper-Riegler were measured. Drainage during washing was also studied.

Wheat straw pulp was more difficult to be compressed than expected beforehand. The compressibility of wheat straw pulp seemed to be affected by inner hydraulic pressure inside of the pulp mat during compression. Wheat straw pulp fiber had quite the same specific volumes as wood pulp. Wheat straw pulp had a clearly higher specific surface than wood pulp. This was due to the high amount of fines fraction in non-wood pulp. High specific surface was the most evident cause for poor drainability. The removal of the fines fraction from the wheat straw pulp improved the drainability significantly.