A practical solution to the silica problem in straw pulping.

Abstract

In this study, the soda-oxygen, soda-anthraquinone and soda processes were evaluated for the pulping of wheat straw with respect to silica content, and chemical, physical and optical properties of the unbleached pulps. Soda-oxygen pulping gave the highest retention of silica by the pulp, and thus the least transfer of silica to the spent pulping liquor, with 80.4% of the silica remaining in the pulp. The addition of 1 to 3% oxides, CaO, MgO, and Al 2 O 3 , was also evaluated as a way of enhancing silica precipitation onto pulp. Results showed that 3% Al 2 O 3 added to the soda-oxygen process gave the best results among the methods studied, with 96.5% of the silica remaining with the pulp. Although the oxide-added soda-oxygen processes gave the best retention of silica they showed slightly inferior pulp physical properties. Overall, the oxide-added soda-oxygen process offers a highly practical and efficient solution to the non-wood pulping silica problem compared to the use of conventional desilication methods.