TiO2 Production : Monitoring Cl2 in the stack after Cl2 destruction unit
HCl and Cl2 are used or produced in a wide variety of chemical processes. They may also be produced by incineration of chlorine containing materials. Very often they are present at the same time, depending on temperature, humidity and other parameters. When produced as a byproduct of a process or incineration, they are typically disposed of by a wet scrubbing process and released up a stack. While HCl is very water soluble even under relatively low pH conditions, Cl2 typically requires a caustic scrubbing solution. Because of this, scrubber optimization has economic as well as environmental implications.
The environmental concerns related to these compounds are an important factor. Both are toxic and corrosive. However, Cl2 is often considered a more dangerous compound. For this reason, specific monitoring for both compounds is becoming an important issue with local, state and federal agencies. These concerns have pushed desired detection limits to low ppm and in some cases ppb levels.
Making chlorine measurements in scrubber applications presents a number of challenges. The sample stream is typically saturated with water vapor, and often contains large amounts of entrained scrubber liquor.