Intensity Index
Energy transferred per unit surface area of refiner bar pattern intersections defines the mechanical intensity applied to cellulosic fibers during stock preparation. Calculating specific surface load controls the balance between fiber cutting and fiber fibrillation during pulp refining operations. The parameter equals net refining power divided by the product of rotor bar edge length and stator bar edge length passing frequency.
High intensity loading cuts fibers and lowers pulp freeness rapidly, whereas lower intensity loading promotes internal swelling and external fibrillation. Hardwood fibers require lower intensity energy transfer to avoid severe fiber shortening. The calculation stops applying when refiner plates disengage or when non-bar refining technologies such as homogenizers are employed.
Refining Calculation
Bar edge length calculations incorporate bar width, groove width, and bar angle across the active refining surface area. Net power input divided by total bar crossing area per second determines the specific surface load applied during each impact. Narrower bars increase edge length, lowering load intensity at constant motor power.
Fiber Development
Softwood kraft pulps tolerate higher mechanical impact loads because long fibers withstand bar shearing forces without excessive shortening. Applying high specific surface load to recycled fibers accelerates fines creation and causes poor dewatering on the paper machine wire. Papermakers adjust disc rotation speeds and plate clearance to maintain optimal intensity targets for each pulp furnish type.
Proper load control yields maximum tensile strength development at minimum specific energy consumption.
