Due to health, safety and environmental concerns about dioxins and furans, the once prevalent use of elemental chlorine as a pulp bleach agent has given way to alternate technologies. Today, Elemental Chlorine Free (ECF) technologies are used for about 95% of bleached pulp production. A generator produces CLO2 that is mixed with water for bleaching.
Gaseous chlorine dioxide is conveyed to an absorber tower where it is dissolved in chilled water to yield the aqueous chlorine dioxide bleach solution. Maintaining continuous level in the generator is critical because the chemical material balance in and out of the generator is essential. Malfunctioning controls can create a "White Out" where bleach production ceases and a shutdown ensues.