Packed, dry and wet scrubbers are used to treat or clean the following lists of chemicals from a process exhaust air stream, with ammonia being the most popular:
- Ammonia
- Chlorine
- Hydrochloric Acid
- Chlorinated Silanes
- Sulfur Dioxide
- Hydrogen Sulfide
- Boron Trifluoride
- Amines
Theory of Application
Wet scrubbers are designed to remove pollutants from a gaseous stream with a scrubbing liquid. In a single-stage, vertical packed scrubber, the tower contains randomly dispersed packing to improve contact between the gas and liquid phases. The polluted stream flows upwards through the bottom of the packed tower countercurrently to the flow of a scrubbing liquid. The cleaned gas then passes through a mist eliminator to remove any entrained liquids.
Wet Scrubber Technology & Life Cycle Cost Tradeoff Considerations
One of the many products offered by GCES is a vertically packed bed scrubber. A packed bed scrubber is a wet scrubber that removes soluble chemicals, fumes, and odors. Contaminated gas flows through a specially designed packing media that is wetted with recirculated liquid. The liquid solvent absorbs the gas pollutant by physical or chemical reactions. A liquid blow-down from the tank or sump section of the packed bed scrubber removes contaminant products before they precipitate.
For each application, the scrubber is sized and designed to meet specific customer requirements. The tail gas to be cleaned is carefully analyzed to determine the optimum design parameters and to allow for the best operating solution for each installation. After thorough analysis, GCES offers several options of fume or exhaust scrubber equipment packages based on plant equipment, local air regulations, plant locations, and other factors. Our experience in designing scrubbers for many different chemicals shall provide each customer with the assurance that the plant’s air quality will have a minimal impact on the environment.
Utilizing Wet Scrubbers to Treat Ammonia
One of the most common uses for wet scrubbers are in the treatment of Ammonia. Ammonia (NH3) is a colorless, corrosive, pungent gas used in a variety of industries including pharmaceutical, fertilizer, food, chemical, and semiconductor. It has an explosive range in air from 16-25% by volume and is moderately toxic. It has an Immediately Dangerous to Life and Health (IDLH) concentration of 300 parts per million by volume (ppmv) with OSHA Permissible Exposure Limit (PEL) of 50 ppmv. The odor threshold for Ammonia is 5 ppmv, giving ample olfactory warning of potential danger. Although Ammonia is not a Hazardous Air Pollutant (HAP), it is regulated as a precursor to PM2.5 and PM10 Criteria Air Pollutants. This is because it reacts with acid gas pollutants to form respective Ammonium Salts in the atmosphere (such as Ammonium Sulfate or Ammonium Nitrate).
Aqueous Ammonia solutions have very high vapor pressure, which prevents plain water from being recycled in an wet, dry or packed air scrubber system. The 
water must be discarded after a single pass through the air scrubber. In some instances, this may be acceptable or even desirable if the plant has a use for a solution of dilute Ammonium Hydroxide, i.e., Aqua-Ammonia. Due to the alkalinity of NH3, it is very effectively scrubbed using an acid solution. This allows recycling of the water due to the NH3 reacting to form a non-volatile Ammonium Salt.
The most common acid used in air scrubbers is Sulfuric Acid, due to its availability, low cost, and non-volatility. The product formed when Ammonia is scrubbed with Sulfuric Acid is Ammonium Sulfate, which is a common fertilizer ingredient. Thus, depending on the quantity of NH3 being scrubbed, the Ammonium Sulfate by-product may have market value. Ammonia air scrubbers incorporate a variety of gas-liquid contacting techniques, including packed beds, spray chambers, and water jets. In every application, GCES considers all factors in selecting the optimum design. We offer complete packages for our dry, packed or wet scrubbers systems, including instrumentation and controls, skid-mounting of equipment, acid storage tanks, metering pumps, and installation.
Gulf Coast Environmental Systems offers multiple design solutions to best fit the operational parameters of its customers. In some cases the desire is for a lower capital investment for a higher operating cost for those systems that do not need to run continuously or the need may be for a slightly higher capital investment with a lower operating cost for those systems that do need to run continuously. The designs include single stage solutions as well as multistage solutions. GCES also offers complete integrated solutions with other air purification systems such as thermal oxidizers, carbon adsorption systems, or filtration packages. Gulf Coast Environmental Systems is a single source solution for highly durable and efficient packed bed scrubbers.