Minimizing Effluent Through Water Management, 1996 Minimum Effluent Mills Symposium Proceedings

Paul H. Wilson

Dean Oliver

The quantity of effluent discharged from a mill, as well as the quantity of suspended solids and BOD can effectively be reduced by managing the water cycles in the mill. This approach addresses the process systems within the mill and investigates the unit operations associated with the systems to optimize them. A byproduct of any water reduction program is a reduction in the steam use of the mill. Frequently, this results in an imbalance in the steam distribution, which can require rebalancing the turbogenerators. Process simulation is used to execute the heat and mass balances required at all stages of the analysis. The result is a rapid analysis that pinpoints deficient unit operations and offers a capital spending plan that outlines the necessary process changes. The usual result is a better process with less waste and pollution, improved yields, increased capacity, lower operating costs and reduced energy demands. A case study is presented: a 1990 study that significantly decreased water usage and allowed additional pulp production while reducing total steam generation and increasing power production.