Mass Balance Arithmetic and Yield Loss Factors in Fiber Ledgers
Applying uncorrected gross weights or inflated yield factors into mass balance ledgers creates over-allocated credit accounts that trigger customs seizures.
Save-All Filtration
Liquid Recovery
Wet end save-all filtration captures suspended cellulosic fibres and mineral fillers from paper machine white water streams before discharge or reuse. Disc filters and drum filters achieve this separation by passing process water through fine woven polymer cloths or stainless steel meshes. Suspended solids accumulate on the filter medium while clarified filtrate passes through for deployment in pulp dilution or shower headers.
Retained fibres form a delicate mat on the rotating sector faces, which assists subsequent particle retention until a high pressure shower dislodges the concentrated stock. Operating efficiencies depend directly on influent consistency and rotational speed, requiring constant differential pressure monitoring across the filter segments to prevent blinding. Production planners balance drum submergence depth against vacuum levels to maintain target filtrate clarity without stalling the recovery circuit.
Excessive solids loading in the feed flow reduces permeability rapidly and forces premature backwashing cycles.
Slurry Thickening
Secondary save-all filtration upgrades recovered pulp consistency from dilute white water concentrations up to twelve percent total solids for direct return to the machine chest. Screw presses and vacuum disc units compress the reclaimed fibre network to expel interstitial moisture and lower subsequent drying energy requirements in the dryer section. Recovered furnish contains significant quantities of precipitated calcium carbonate and kaolin clay, altering the filler loading ratio of the finished packaging grade when reintroduced to the primary stock preparation loop.
Chemical retention aids are often dosed into the feed zone to agglomerate fine particles before the filtration stage, securing high capture rates for particles smaller than ten microns. Thermal energy demands drop measurably across the paper machine when thickened broke and save-all returns enter the wet end at elevated consistencies.
System Closure
Complete white water loop closure relies on save-all filtration to prevent dissolved and suspended solids accumulation from disrupting sheet formation and pressing dynamics. Closed circuit operations reduce fresh water consumption per metric ton of finished board while increasing the concentration of inorganic salts and sizing chemicals in the circulating liquor. Residual sizing agents and wet strength resins recirculate continuously through the save-all unit, occasionally causing deposition issues on wire cloths and internal piping surfaces.
Microbiological growth accelerates within enclosed white water systems as temperatures rise, demanding biocide addition upstream of the save-all installation to protect filter media integrity. Permeate quality dictates whether the recovered water serves as high pressure shower supply or low pressure dilution fluid within the hydropulper.