Energy consumption in refiner mechanical pulping.

The efficiency of mechanical pulping has long been of interest due to the large energy consumed by the process. Previous estimates of theoretical efficiency have accounted for less than 20 % of the energy employed. In this study, we make new estimates based on fracture mechanics and abrasion as the mechanisms of new surface creation. We postulate that fracture mechanics comminutes wood into fibres and creates pores in fibre walls. This consumes around 100 kWh/t. Abrasion peels surface material from fibres in the form of morphologically different fines particles. Based on abrasion theory, we estimate this specific energy to be around 1,330 kWh/t. Together, fracture mechanics and abrasion, account for about 70 % of the specific energy (2,000 kWh/t) to produce TMP for printing paper grades. We postulate that the remaining energy is consumed as hysteresis losses from viscoelastic strains not linked to creation of new surface. The largest single source of energy consumption, abrasion, alone accounts for about 66 % of the energy of the process. Finally, we discuss how energy may be reduced by refining intensity and other means. [ABSTRACT FROM AUTHOR]