EFFECTS OF SYSTEM CLOSURE ON RETENTION AND DRAINAGE AID PERFORMANCE IN TMP NEWSPRINT MANUFACTURE. PART II

摘要

As the degree of mill system closure increases, how well will currently available retention and drainage aid systems function in newsprint mills? In a previous report a number of retention aid systems were investigated for their applicability in system closure. Our objective in this work was to expand upon the previous study by investigating the performances of a wider range of retention and drainage aid systems. As in the previous study, the results indicate that at high degrees of closure, the PEO-cofactor retention aid systems are the most efficient. The choice of the correct cofactor was shown to be very important. The results also confirmed that, with increased system closure, the increase in cationic demand tends to result in a poorer performance of cationic polyacrylamide (CPAM) polymers. The best-performing CPAMs were those with high molecular weight and high charge density. In general, coagulants used in conjunction with flocculants tended to have a negative effect on the retention and drainage variables studied. The performance of bentonite retention aid systems deteriorated with increasing system closure.