Buildup of Dissolved Solids in a Paperboard Mill With Water Closure

摘要

This study investigates the buildup of dissolved solids in the mill water system with increased effluent recycling at Solvay Paperboard(SPB),a paperboard mill located in Solvay,New York.SPB underwent a water reduction program through effluent recycling in three separate phases with the intention of reducing its fresh water consumption.A paper machine,with its associated components,is considered as a process block with various critical species entering the block with the input streams and leaving it with the output streams.For Phase 1(two paper machines operating in a parallel mode)and Phase 2(two paper machines operating in parallel connected to a third paper machine in series)operations of SPB,mass balances for critical inorganic substances are formulated in order to deduce their buildup in the mill water system and in the paperboard as the degree of water recycle is progressively increased.The modeling takes into account the partitioning or retention of a critical species to different extents in the output streams of a process block.In order to calibrate and partially validate the models,the theoretical development is complemented with flowrate and composition data of the input(furnish,chemicals,freshwater,and recycled effluent)and output(rejects,paperboard and effluent)streams of a block.As the extent of effluent recycle rises,the theoretical buildup curves suggest sharp increases of sulfate,chloride and sodium in the mill water system whereas low buildups are predicted for calcium,magnesium and silica.