That’s how many metres of piping are being used for the new highdensity polyethylene (HDPE) effluent pipeline at Tugela Mill which is replacing the existing steel pipeline at a cost of ZAR55 million. The advantage of HDPE is that the potential for corrosion, unlike a steel pipeline, is eliminated. The replacement of the pipeline and the subsequent lower risks of efﬂuent leaks aligns with our focus on treading more lightly on the Planet.
Reducing COD demand and water abstraction
High demand for a high-performance fluting grade, UltraFlute produced at Tugela Mill, 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 results lead to modification to the washing stages and filtrate system which significantly improved pulp quality. Further improvements made in the pulp plant included the re-use of process water and the introduction of closed loop seal water systems. These initiatives not only reduced water consumption, but also yielded some energy savings.
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%. The increase in direct pulp feed to the paper machine also reduced the water demand from the repulpers. Additional water reduction projects in the mill included the control of process water balances, fixing water leaks together with inspections and repairs of open water storages, all of which resulted in further reduction in abstracted water of approximately 30%.
All the water improvements described above were made while the mill increased its pulp production by more than 23% and paper production 5% over the same period.