Press wetting as an enhanced wetting method for baled OCC material

A procedure to mechanically force water into the bale structures of old corrugated container (OCC) material was studied and evaluated in low-consistency pulping studies. Two mechanical methods were used in the study: (1) roll pressing of sheets and (2) press wetting of bales. Mechanical pressing was first used in simple roll tests to evaluate nip pressure as an enhanced effect on wetting. Repeated press wetting treatments were found to increase water penetration into the sheets and appeared to lower wet strengths. A simple laboratory-scale bale pressing device was constructed and the effect of different parameters in wetting method was studied. We found that when a bale was pressed under water, multiple pressings were needed to get efficient press wetting. Increased temperature was found to increase water penetration inside the porous structure of linerboard. We also discovered that there must be a delay between relaxation and pressing to allow water to travel within a board and to wet all surfaces. The wetting procedure also evaluated the weight of water inside the bale. Results showed that the amount of water could be used as an indicator of the pulping kinetics and energy consumption needed to disintegrate OCC. The enhanced method (i.e., hydraulic pressing) could provide efficient wetting on an industrial scale. With this method, a 30% savings in the energy consumption required in pulping unit operation is possible.