B4SH-9-C by flangemounted pump LP B V Dip lubricat Bevel-helical gear unit B4

Flender/Flender Gear Units/Bevel-helical gear unit B4

sodium silicate during flotation deinking of secondary fibre pulps. 3. Results For the model compounds selected by way of literature search, the activation of hydrogen peroxide by soda lye and, at reduced pHs, by sodium hydrogen carbonate was analysed by IR spectroscopy. It was found that, in the case of NaOH substitution, identical reaction products were formed in the faintly alkaline pH range. This phenomenon is attributable to hydrogen peroxide, since in its absence only the original compounds could be characterized. When NaOH and sodium silicate were replaced by sodium hydrogen carbonate, H2 was activated, too. However, in the presence of NaHCO,, the reaction rate was slowed down so that extend- ed reaction times and temperature increase were required for activation. Additional tests were conducted with mechanical pulps. For groundwood bleaching, pHs can be reduced by substituting sodium hydrogen carbonate for NaOH and sodium silicate since the original brightness levels are higher. An ion exchanger might be used as well, provided the bleaching conditions are suitably matched. Initial pHs should in any case be in excess of 9. reduced initial pH will slow down the reaction time when NaOH is replaced by sodium hydrogen carbonate. Accordingly, results equivalent to those of conventional bleaching can only be achieved if the bleaching period is extended. . 3 Particular importance attaches to the use of sodium silicate: there seems to be no way of doing without it even in the absence of heavy metal ions. As far as TMP is concerned which is difficult to bleach, NaOH may only be replaced if less demands are made on the brightness of the bleached pulp. for Superior bleachin results, peroxide activation alone is insufficient. However, higher brightness levels go hanc?in hand with degradation reactions which increase the COD loading of circuit waters and effluents whilst reducing the strength levels of the bleached pulps. Depending on the mech