Wet air scrubbers: pH monitoring

Wet air scrubbers find numerous applications in industrial processes to take away dangerous and polluting gas emissions. These gases are caused by combustion in utility and industrial process plants. Nevertheless, the process of air treatment by wet scrubbers demonstrates high efficiency in the removal of by-products and waste gases such as hydrochloric acid (HCl), hydrogen sulfide (H2S), chlorine (Cl2), and sulfur dioxide (SO2).

To be more precise, the operating principle of wet air scrubbers is based on “spraying the incoming gas stream with a scrubbing solution containing a neutralizing chemical, which destroys the harmful gas.” Herewith, the efficiency of the scrubbing solution is dependent on the concentration of chemicals that are used throughout the air treatment process. Therefore, it is necessary to maintain chemical concentration in scrubbers to provide effectiveness.

It should be noted that it is possible to ensure monitoring of the scrubbing solution strength by either of the following techniques:

  1.  Continuous wet air scrubbing that includes continuous replenishment and blowdown where the control of scrubber solution, the scrubbing chemical, and gases influence the composition.
  2. Batch wet scrubbing is based on “an initially high concentration of scrubbing chemical that is enabled to achieve near depletion, followed by blowdown and replenishment by fresh, full-strength wet air scrubber solution.”

Also, it should pay careful attention to the choice of whether to monitor wet scrubber solution strength with pH or conductivity because it stands upon the solution composition and how it varies during the wet air scrubber operation. Modern scrubber systems use special sensors for pH monitoring.

For instance, pH sensors in wet scrubbers are installed at a high flow area (in-line > 3 ft/sec velocity is suggested), while conductivity sensors are applied for scrubber system control because they offer such benefit as high resistance to fouling and need for minimal maintenance, unlike conventional contacting sensors. Moreover, such sensors for air treatment devices provide the high conductance of many of these scrubbing solutions and by-products.

Finally, it is required to collect the full information about the wet air scrubber application before choosing sensors:

  • Gas or gases being scrubbed (chemical name and formula);
  • Scrubbing chemical and desired concentration range;
  • Scrubbing method employed:
  • Maintaining scrubbing chemical concentration by continuous blowdown and replenishment (continuous wet air scrubbing)
  • Enabling scrubbing chemicals to deplete down to a certain concentration range (batch wet scrubbing).

Optromix is a fast-growing vendor of wet air scrubbers. The multi-vortex scrubber can remove gas emissions, dust, vapors, and other pollutants from a gas stream.  It is an innovative technology created to save water that makes it more cost-efficient and differs from other types of scrubbers.  If you have any questions or would like to purchase a multi-vortex wet air scrubber, please contact us at info@optromix.com

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