3.medium strength beating
China has conducted extensive research on medium-strength pulping and has applied it in production, achieving good results.
The characteristics of medium and low concentration pulping are quite different.
The characteristics of medium and high consistency slurry are introduced as follows.
(1) Concentrated pulping of undyed coniferous wood (Pinus massoniana) in sulfate pulp
Pinus massoniana is a fast-growing coniferous timber widely grown in the Yangtze River Basin of China and its southern regions. It is a commonly used papermaking material in paper mills across southern provinces and cities.
However, from a fiber morphology perspective, its use as a papermaking raw material presents certain limitations: The high resin content in Pinus massoniana resin often causes resin blockage during pulping. Additionally, the thick fiber walls and pronounced microfiber angles in this material complicate pulping processes, as they hinder the removal of thick primary and secondary cell walls. The pronounced microfiber angles also impede longitudinal fiber tearing, further fibrillation, and broom-like fibrillation. Consequently, when using traditional twin-disc mills for low-concentration pulping, achieving the desired pulping quality requires multiple disc mills and consumes significant energy. Despite these efforts, the resulting paper often exhibits issues like uneven consistency and low strength, posing challenges for subsequent dehydration and forming processes on polyester forming fabrics.
For the pulp of Pinus massoniana without bleaching, the pulp density, the burst resistance and the ring pressure index of the finished paperboard are all improved obviously when the pulp beating degree is reduced by using medium concentration beating pulp instead of low concentration beating pulp.
This phenomenon occurs during medium-to-high pulp concentration pulping, where the high rotational speed of the mill plates and elevated pulp concentration induce intense turbulent flow of fibers within the mill zone. The resulting substantial internal friction causes the primary cell walls of Pinus massoniana pulp fibers to be crushed and fragmented, leading to longitudinal tearing and fibrillation. This process releases abundant hydroxyl groups while simultaneously increasing fiber flexibility. These conditions create optimal conditions for uniform fiber interweaving and efficient dehydration on polyester forming fabric, resulting in superior fiber cohesion and optimized fiber network formation during web formation. Consequently, the resulting paper exhibits significantly enhanced tightness, uniformity, tear resistance, and ring pressure index.
Moreover, medium-strength pulping demonstrates significantly lower energy consumption than low-strength pulping. The fibers processed through this method exhibit optimized morphology, better meeting the operational requirements of modern high-speed paper machines for polyester forming fabrics. This process reduces fiber loss and enhances the paper's two-sided properties.
In conclusion, the medium-concentration pulping technology not only enhances the pulping efficiency and paper quality of Pinus massoniana pulp, but also establishes a solid foundation for subsequent high-efficiency, high-quality papermaking on polyester forming fabric. As a pivotal component, it significantly improves the technical and economic performance of the entire production line.
