Alkyl Ketene Dimer Wet End Hydrolysis in Alkaline Hardwood Furnish
Alkyl ketene dimer hydrolysis in alkaline hardwood stock converts active sizing wax into unreactive dialkyl ketone, raising chemical costs and felt deposits.
Sheet Dewatering Efficiency
Drainage Kinetics
Water removal metrics across forming and pressing zones determine the thermal energy required to produce a unit mass of dry paperboard. Gravimetric assessment of wet web solids content at each process interface establishes sheet dewatering efficiency, which directly dictates machine speed limits and steam consumption rates. Forming section drainage removes free water through vacuum foils and couch rolls, raising solids content to roughly 20 percent.
Mechanical press nips subsequently express capillary water, elevating web dryness to between 45 and 50 percent solids before the web enters the dryer section. Thermal evaporation in the dryer section consumes over 80 percent of total paper machine energy, making mechanical dewatering optimization vital for cost control.
Dewatering Mechanism
Mechanical compression drives interstitial water from the fibre matrix into press felts under high nip loads. Viscous drag forces resist water movement through fine capillary channels within dense hardwood webs.
Temperature Influence
Elevating stock temperature reduces water viscosity, accelerating drainage rates through the wire mesh. Steam boxes installed on the vacuum couch or press section heat the wet sheet, increasing press dewatering by up to 2 percent dryness. Lower water viscosity allows faster fluid flow through the compressed web matrix under applied vacuum levels.