CHARACTERIZATION OF THE PFI MILL BY THE C-FACTOR

Many mills use a laboratory PFI mill to estimate pulp performance in m ill refiners. An estimate has been made of the number and intensity of impacts imposed on fibres in a PFI mill to permit quantitative compar ison with disc and conical refiners. The PFI mill imposes a far greate r number of impacts compared with other refiners. During 5000 revoluti ons, the PFI mill imposes between 40 and 400 times the number of impac ts of a conical or disc refiner operating at standard specific edge lo ad, The intensity of the impacts is only 1.5-15% of that imposed in a disc or conical refiner at a specific edge load of 30 Ws/m. The energy expenditure of the PFI mill measured for 5000 revolutions is two to f our times larger than that of a typical disc refiner.