Mass Balance
Pulp de-inking plants generate post-consumer fiber sludge loss during the removal of non-fibrous contaminants and short fraction fillers from recycled furnish. De-watering screws and clarifiers capture coarse rejects, yet fine cellulosic fragments escape through filtrate loops into the primary effluent. Suspended solids concentration in the clarifier overflow dictates the actual mass deficit recorded at the weigh scales.
Mill operators adjust polymer dosages in the dissolved air flotation units to flocculate suspended matter before the water reaches biological treatment stages. Chemical oxygen demand loads rise when higher proportions of coated graphic paper enter the repulping hydrapulper, which overwhelms the settling capacity of older clarifier basins. Regulatory bodies enforce strict limits on total suspended solids discharged from the mill boundary, converting fugitive fiber streams into costly landfill disposal liabilities.
Drainage Resistance
Sheet formation on the fourdrinier wire depends on retaining the remaining long fibers while rejecting ash and mineral pigments. When post-consumer fiber sludge loss strips the furnish of fine particles, the Canadian Standard Freeness value climbs rapidly and causes vacuum boxes to draw excess energy. Corrugated medium producers monitor wet end retention closely because erratic drainage behavior alters the caliper of the finished linerboard.
Converting plants reject rolls that show directional porosity variations caused by uneven fiber distribution during the initial de-watering phase on the paper machine.
Yield Calculation
Mass accounting procedures track raw material inputs against finished reels to determine true process efficiency across the entire recycling cycle. Mill accountants subtract dry weight outputs from the total incoming baled paper weight to quantify post-consumer fiber sludge loss over a monthly production period. Accurate moisture meters installed immediately after the press section prevent erroneous dry weight estimations caused by trapped ambient humidity within the paper web.
Laboratory technicians dry random core samples in convection ovens to establish exact ash content percentages before finalizing mill yield reports for corporate management. Stock preparation supervisors compare these laboratory figures against inline flow meter data to detect hidden leaks within the white water recovery circuits. Final production costs reflect the total volume of usable cellulose diverted into the de-watering press cake rather than converted into saleable packaging grades.
