Scrubbers are a reliable means of removing fine particles from the gas stream through absorption. Scrubbers can be classified as dry or wet. Wet chemical scrubber systems filter dust by introducing the polluted air stream with water droplets. There are various wet impingement configurations, such as spray nozzles, misters, cyclonic, venture dispersion, and others, to capture fine particles present in the air. Wet scrubbers are one of the most common odor-control technologies used in the wastewater industry and sewage industry. The wet scrubbing process effectively treats the foul odor of hydrogen sulfide, hydrogen chloride or ammonia (the common creators of odors) by using a caustic solution, which is capable of absorbing large amounts of the target gas.
What are some common challenges?
While the technical concepts of wet scrubbers are well understood by most engineers and operators, scrubber applications in the real world host many operation and maintenance challenges that can impact wet scrubber efficiency, which we will discuss below briefly:
- Controlling pH of the system and thus maintaining the oxidation-reduction potential
- Monitoring the build-up of salt
- Ensuring sufficient gas and liquid contact time
- Analyzing system conditions at frequent intervals to ensure proper operation
What affects the Scrubber’s performance?
Two main parameters define the performance of any scrubber: the efficiency of gas-liquid contact and the adequacy of the chemical to maintain conditions for absorption. Plastic packing material provides a high surface area to volume ratio for increased gas and liquid contact. It also maximizes absorption with minimum flow interference. Oxidation and reduction potential (ORP) and pH controls play a significant role in delivering a proper chemical-limited performance. When designing a column which involves acid/base neutralization in water, one must first determine a pH at which the column will be operated. The most common absorbents used to remove sulfide-based odor are sodium hypochlorite and sodium hydroxide, also known as bleach and caustic soda. In the case of ammonia odor, slightly acidic solutions are used.
What makes up a scrubber system?
Wet scrubbers function with the help of several mechanical and electrical components, making it complex and efficient in odor removal simultaneously. Typical wet scrubber systems consist of
- Absorption vessels and packing
- Fan system
- Spray nozzles
- Mist eliminators
- Chemical solution circulation pumps
- ORP and pH probes
- Chemical storage and feed pumps
- Make up water system
- Controls and instrumentation
Operating problems can arise in a scrubber due to poor mechanical equipment, inadequate ORP and pH system, or inefficient mass transfer in the system. Scaling, which is deposition of calcium compounds on packing material or mist eliminator can significantly affect the performance of the scrubber as well. Therefore, it should be carefully monitored.
Inefficient scrubbers cost facilities enormous amounts of money. Whether the inefficiency is due to poor design or lack of maintenance, it is critical that the issue is addressed as soon as possible. Mach Engineering can help determine the cause of the inefficiency and develop a strategy to fix the problem. By collecting process data, Mach Engineering can perform a detailed process simulation specific to your system. The process simulation data combined with Mach Engineering’s vast experience in troubleshooting under-performing scrubber units will help you maximize your system’s performance. For more information on how Mach Engineering can help you get the most out of your scrubber please visit contact us or give us a call at (281) 550-3232.