Chemical Concentration
Kraft pulping relies on active cooking liquor to break down lignin and liberate cellulose fibres for paper production. Sulfidity describes the ratio of sodium sulfide to the total active alkali within the white liquor circuit. This property influences the selectivity of the pulping reaction and the strength characteristics of the resulting pulp.
High levels promote the removal of lignin while preserving the structural integrity of the cellulose chain. Proper control of this chemical balance dictates the efficiency of delignification across various wood species.
Process Stability
Consistent chemical delivery maintains the causticizing efficiency of the recausticizing plant. Fluctuations in the sodium sulfide concentration shift the rate of lignin dissolution and alter the final pulp quality. Paper mills monitor these levels to avoid excessive reagent consumption or incomplete fibre separation during the digestion phase.
Deviations from the optimal set point frequently lead to uneven bleaching response or reduced tensile strength in the finished sheet. Operators adjust the make up chemicals to compensate for sulphur losses in the recovery boiler and the kiln.
Mill Performance
Secondary impacts of chemical dosing affect the corrosion rate of steel equipment throughout the recovery cycle. Higher sulfide concentrations accelerate the degradation of materials in piping and vessels when temperatures exceed specific thresholds. Engineering teams determine the metallurgical requirements for plant infrastructure based on the expected range of this chemical parameter.
Careful management of the active cooking components remains a fundamental requirement for the long term viability of pulp mill operations.
