Internal Treatment of Process Waters in Paper Production by Dissolved Air Flotation with New Developed Chemicals. Part 1: Laboratory Tests

New chemicals, based on the synergistic effect between inorganic polyaluminium salts and organic cationic polyelectrolytes, have been tested for the chemical optimization of a dissolved air flotation (DAF) unit, used as internal treatment of process waters in a paper mill based on 100% recovered paper. Laboratory tests have demonstrated that polyamine modifications of the aluminium salts are the most efficient in the removal of contaminants, being the combination of a polyaluminium nitrate sulphate salt and a polyamine the most efficient. This chemical has been studied under different conditions, such as different dosages or in combination with a flocculant, for the treatment of waters from different paper grade production, and the results have demonstrated a good performance at lab scale. Therefore, a field trial is recommended for assessing its potential benefits at mill scale, which is described in Part II of this work.