Project Synopsis

Evaluate and suggest improvements to an existing caustic scrubber designed to remove HCl fumes.

Project Summary

The client, a large chemical manufacturing concern, requested that Process Engineering Associates, LLC (PROCESS) review the current physical installation of its caustic scrubber and provide recommendations for improved HCl acid removal.  The caustic scrubber is a packed tower that uses dilute caustic to remove miscellaneous impurities from both the process and tank farm vents.  The client was experiencing less than optimal scrubber performance when offloading aqueous HCl trucks into the HCl storage tank.

PROCESS evaluated the scrubber by building a CHEMCAD process simulation model to determine if the overall design was adequate for HCl removal at the specified rates.  In addition, the scrubber gas velocity, liquid loading, packing size, and pressure drop were compared to typical design parameters for packed towers utilizing random spherical packing.  A tower packing distribution company was contacted for suggesting an alternate packing style that could provide better performance.  Finally, the caustic spray nozzles, caustic recirculation pump, and mist eliminator (or lack thereof) were evaluated for proper design.

These evaluations revealed that the overall scrubber design was adequate for HCl removal.  However, PROCESS identified three primary recommendations to improve performance.  The first was to install a mist eliminator to address the formation of HCl aerosol in the column.  The second was to change the Bete spray nozzles to a size that was better matched to the caustic recirculation flow rate to prevent any dry zones and/or inadequate spray patterns.  The third was to refill the column with packing to increase vapor-liquid contact and increase scrubber efficiency.  As general improvements, PROCESS suggested installing a strainer on the caustic pump discharge to reduce solids and the potential for plugging and increase caustic strength to improve scrubbing capacity.

The client is currently reaching out to vendors to specify a mist eliminator and spray nozzles for the application as well as determining the timing for implementation of these improvements.

Industry Type

  • Scrubber evaluation and design
  • Process improvement and optimization


Utilized Skills

Chemicals Production

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