High demand for a high-performance fluting grade, UltraFlute produced at Tugela Mill (South Africa), increased the internal requirements for high-quality neutral sulphite semi-chemical (NSCC) pulp from the semi-chemical cooking process. With the assistance of the Sappi Technology Centre, the mill embarked on multiple projects to improve the washing in the pulp plant and ensure quality pulp transfer to the paper machine. The end result significantly improved pulp quality. Further improvements made in the pulp plant included the reuse of process water and the introduction of closed-loop seal water systems.
The cleaner pulp to the paper machine had a direct impact on the mill’s final effluent chemical oxygen demand (COD), reducing the COD load by 40%. This is important, because the lower the COD, the less oxygen is required to break down the organic substances in the wastewater.
The increase in direct pulp feed to the paper machine also reduced the water demand from the repulpers while additional water reduction projects in the form of control of process water balances, fixing water leaks and passing valves together with inspections and repairs of open water storages, resulted in a further reduction in abstracted water of approximately 30%.