Special Report No. 90-08: An Investigation of the Effect of Increased Hypochlorite Stage Temperature and pH on Choroform Generation at a Bleach Plant

A field trial was conducted at a CEHDED bleach plant to investigate if chloroform generation in the hypochlorite stage could be reduced, as predicted from laboratory experiments, by increasing the pH and temperature from 145°F and pH 10.1 to 180°F and pH 11.7. During the trial, the chloroform concentration of the hypochlorite stage filtrate was reduced 89 percent and the total chloroform generated in the hypochlorite stage (including vent emissions) was reduced 82 percent. Hypochlorite stage pulp brightness was reduced somewhat during the trial, but mill personnel indicated that it remained within the normal operating range and final pulp brightness was not affected.