Factors influencing flocculation of dissolved and colloidal substances in a thermomechanical pulp water

To achieve a cleaner system in integrated paper mills using thermomechanical pulp (TMP), it is important to flocculate the dissolved and colloidal substances (DCS) and trap them in the forming web. Since most of the flocculation experiments are performed in the presence of fibres, the flocculation of DCS in the TMP water was investigated in the absence of fibres. Two cationic polyacrylamides (C-PAM) and two electrolytes were used in the experiments. Two different techniques were used.for evaluation of floc size vs polymer addition. The results indicated that a decrease in thefloc size occurred at low addition levels of C-PAM. At higher C-PAM amounts, an increase in the flocculation intensits, was observed. Theflocculation intensity was increased until a maximum was obtained. Further addition of C-PAM caused a decrease in the degree of flocculation. The flocculation intensity was increased when electrolytes were added to the samples.