| Environmental concerns and pressures have made the pulp and paper industry move towards the recirculation of white water. These measures have led to lower volumes of water discharged by those mills recirculating water, and also to increasing problems in the mills. One of these problems is the loss of effectiveness of the PEO-cofactor retention aid systems, due to the increasing concentration of dissolved solids in the water. The results show that the presence of high surface area compounds such as fines, clay and organic compounds, like abietic acid can indeed affect the efficiency of PEO.;The development of a laboratory scale twin wire sheet former has helped study the retention aid system described above under conditions which resemble those found in a mill. This apparatus has helped study the effect the retention aid system had on water drainage and fines retention. The fines retention improved as the concentration of PEO was increased but the water drainage had decreased. Bentonite was added to the system to study its effect on the fines retention and the drainage. Bentonite combined to a PEO-cofactor retention aid system was found to have a positive impact on both the retention and the drainage. |
