From Odor Control Systems
The basic components of the scrubber are the vessel; packing material; liquid recirculation system with spray nozzles, recirculation pump, a sump; and a mist eliminator. A fan draws or pushes the odorous air into the scrubber. The air passes through the packing bed where it comes in contact and is absorbed into the liquid solution sprayed from nozzles above the packing bed. The liquid solution, after passing through the packing bed, falls into the sump, where it is recirculated or discarded.
Chemical scrubbers are a common odor control technology. The basic objective of a scrubber is to provide contact between odorous air, water, and chemicals to provide oxidation or entrainment of the odorous compounds. The odorous compounds are absorbed into the scrubber liquid, where they are oxidized and/or removed from the scrubber as an overflow or blowdown stream.
The air exits the packing bed and is routed through the mist eliminator to minimize liquid droplets from exiting the scrubber. Typical chemicals used in the liquid solution to oxidize NH3. An ORP probe and controller maintain the proper chlorine residual by regulating the rate sulfuric acid is added to the solution.
The oxidation reactions are dependent on pH, with the optimum scrubber solution pH being in the 3 – 5 range. In this range, NH3 is absorbed into the recirculation liquid. As pH increases below the optimum range, the NH3 solubility increases and is not effectively absorbed into the scrubber solution. As pH decreases above the optimum range, more chemical is used than necessary, and more carbon dioxide is scrubbed from the air stream. The scrubber chemical concentrations are typically automatically controlled by monitoring the liquid solution pH. A pH probe and controller maintain the proper pH by regulating the rate sulfuric acid is added to the solution. The ammonia reacts with the sulfuric acid to form ammonium sulfate, a soluble, non-volatile salt, which is removed from the scrubber effluent through the overflow.