クロロホルム発生量に及ぼす漂白条件の影響

Abstract

To estimate the amount of chloroform generation at kraft pulp bleaching plant, an evaluation method was developed. The effect of bleaching conditions on chloroform generation in the C-E-H -D sequence was investigated experimentally in our laboratory by the method. As for the amount of generation in chlorination, the influence of the pH was large, and it from alkaline pulp extraction, was ten times more than that from acidic pulp extraction. The proportion of chloroform generation at each bleaching stage was about 60% at hypochlorite stage, about 40% at chlorine stage, and trace amount at final chlorine dioxide stage. When several pulps were treated with chlorination and alkali extraction, a good relationship between chemical charge and chloroform generation was observed with some exception. Furthermore, on hypochlorite treatment, a good relationship was observed, too. These results introduced two equations between chemical charge and chloroform generation. Chloroform generation values at several bleach plants were estimated by these relative equations, and compared with measured values at these plants. In result, these were about equal or estimated values were higher with some exception. Thus, we think that the estimation of chloroform generation at bleach plant by these equations is possible. The reduction of carry over and chlorine dioxide substitution were effective on reduction of chloroform generation. We think these methods could be effective to reduce the chloroform production.