A comparison of antichlors used in scrubbing chlorine and chlorine dioxide from bleach plant vent gases

A project was conducted to determine the relative effectiveness of several antichlors in regards to their Cl₂ and ClO₂ gaseous "scrubbing" capacity. Both a pilot study as well as full scale trials were completed. Work was done on a bleach plant-packed tower scrubber system at a kraft pulp and paper mill. The pilot study was performed at pH's of 10.0 to 12.0 and therefore may have masked the scrubbing potential of two, lower pH, antichlors. Results from the full-scale trials showed that 45% Sodium Hydrosulfide (NaHS) solution, was the most efficient when compared to 42% Sodium Bisulfite (NaHSO₃) solution and CoProduct solution. A cost analysis was completed and revealed that CoProduct solution was the most cost effective of the three compounds. Other non-economic factors such as scrubber plugging tendencies, the potential for toxic gas formation, and handling difficulties should be examined before a final choice of antichlors is made.