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Module 6: Air Pollutants and Control Techniques - Halogens - Control Techniques
Absorption
Adsorption
Practice
Problems
Objective
- Describe the main types of control techniques used for hydrogen chloride and hydrogen fluoride.
Hydrogen chloride and hydrogen fluoride can be controlled effectively by two main types of control systems: absorbers and adsorbers.
Due to their extreme solubility in aqueous liquids, both of these compounds
can be controlled efficiently in wet scrubbers. Virtually all types of
wet scrubbers will perform adequately as long as they are properly designed
for the HCl and/or HF concentrations in the gas stream. The most common
type of wet scrubber absorber for HCl and/or HF is the packed tower scrubber
similar to the unit illustrated in Figure 1 . This
type of unit has one or more beds of packing, which is coated with scrubbing
liquid flowing downward over the packing. Alkali is added to the recirculating
scrubbing liquid to maintain the liquid pH in the range where removal
efficiency is highest.
Another type of hydrogen chloride scrubbing system is illustrated in Figure 2. This system has a venturi scrubber upstream from the packed bed scrubber to remove particulate matter before it can cause partial pluggage at the bed inlet. The packed bed scrubber (absorber) is used for hydrogen chloride removal.
Hydrogen chloride and hydrogen fluoride can also be controlled effectively in spray-dryer-type dry scrubbers and/or dry-injection-type dry scrubbers. These scrubbers were described previously in the lesson on Sulfur Oxides in this Module. Usually, the removal efficiency for HCl and/or HF is greater than the removal efficiency for sulfur dioxide in both types of dry scrubbing systems.
Practice Problems
Halogens - Control Techniques
- Instructions:
- Complete the Practice Problems before proceeding to the next lesson. Click on the button below.