Avoid problems with calcium chlorite and corrosive gasses with your odor control scrubber.
When planning or designing an odor control system, one should pay close attention to several key variables that can cause havoc on a chemical odor control scrubber when trying to treat hydrogen sulfide or ammonia gases. The need for odor control occurs in many different forms. It is essential to understand the process that is creating the odorous or corrosive gas and the need for odor control & air emissions treatment.
First, begin to identify
all the potential obstacles that may creep up later after the chemical odor or corrosive gas control system goes online, like acid or caustic consumption. For example, chemical odor control systems designed for water treatment for the municipal industry are typically needed and attached to a degasification or decarbonation process, often needed to treat hydrogen sulfide (H2S). However, designers often may not pay close enough attention to the type of water process available for “make-up” water for the chemical scrubber. The addition of caustic can create scaling or fouling. This unknown variable of the makeup water quality can lead to a complete tower shutdown if the chemical scrubber distribution and media bed scales or fouls. The most commonly used chemicals for a hydrogen sulfide (H2S) scrubber are either chlorine in the form of sodium hypochlorite or caustic in the form of caustic soda. Both of these chemicals are common to a water treatment facility and are already in place to adjust and control pH.
The makeup water plays a significant role in the operation of a chemical scrubber.
When water containing high hardness levels is used as the source for the makeup water, your chemical scrubber can become fouled, and scaling can occur in a matter of hours, depending on the alkalinity and salts within the water. Solidification can occur from the scaling when combining sodium hypochlorite and raw feed water at specific pH ranges and these ranges are usually the range needed to achieve peak performance. Calcium chloride will form, and your chemical odor control scrubber will become a solid chunk of calcium chlorite making, making the ability for water or air to pass freely through the media packing next to impossible. No matter what type of media packing is utilized in the odor control or gas scrubber, it can foul and scale if the water chemistry is incorrect. Trust me when I say “been there and done that”! I have seen operators who have allowed a chemical scrubber to become out of balance with pH control and completely solidify the tower column to the degree that neither air nor water passage is possible. The problem can still occur with ammonia scrubbers but are different with different sets of parameters.