Co-refining of wheat straw pulp and hardwood kraft pulp

Wheat straw has been used as a pulping resource in China for many years. Wheat straw pulp (WSP) was widely used to substitute high quality chemical pulps such as those made from wood in producing writing and printing paper to reduce production cost of the resultant paper products and to improve paper smoothness without sacrificing paper strength. In this study, the process of co-refining of WSP and bleached hardwood kraft pulp (BHKP) was compared with the traditional separate refining and then blending these two pulps. The differences in refining energy consumption, the resultant pulp morphological and drainage properties, as well as the mechanical properties of the paper handsheets made of the resultant pulps were examined to explore the potential advantages of the co-refining process. The results show that the co-refining process has the potential to reduce refining energy consumption by at least 30% without affecting handsheet tensile and tear strength at a slightly lower re-wet tensile strength.