Defibering and specific energy consumption in bale pulpers

In this paper, the defibering and the specific energy consumption (SEC) for bale pulping of old corrugated containers and supercalendered paper are studied. Experimental variables were pulper dimensions, rotor shape, process temperature, and pulp consistency. The extent of defibering was monitored by measuring Somerville shives, and SEC was determined for a range of pulping conditions. It was found that SEC is reduced by at least 50% when process temperature is increased from 20{degrees}C to 60{degrees}C and by about 30% when pulp consistency is increased from 3.5% to 7%. The results also showed that defibering is increased by rotors that generate shear forces both radially and tangentially. The more swiftly the mass bale and the flakes are wetted, the lower will be the SEC. The rheology of low-consistency water-fiber suspensions is also discussed, with emphasis on how shear affects defibering during the pulping process.