Project Synopsis

Evaluate and develop improvements for an existing caustic scrubber to increase removal efficiency of nitric acid and hydrochloric acid.

Project Summary


Process Engineering Associates, LLC (PROCESS) was tasked by the client, a specialty metals and materials manufacturer, to evaluate and redesign a caustic (NaOH) scrubber system used for acids removal from an air stream.  The primary objective was to increase the removal efficiency of nitric (HNO3) and hydrochloric (HCl) acids to greater than 99%, with a secondary objective of reusing as much of the original scrubber system as possible.  The results of this analysis were to be used for re-permitting the system.

Project tasks included:

  • Reviewed recent test reports and determining base process conditions for the scrubber design.
  • Evaluated all existing equipment in the scrubber system and determining current expected performance.  The analysis determined that 99% acids removal was not possible with the current configuration using the design process conditions.
  • Identified the causes of below-expected removal efficiency in the existing system.  In this case, it was discovered that the mist eliminator would not remove fine mists (0.1-15 um) as would be expected to occur in a dilute acid air stream, and that some difficulty with nozzles plugging was occurring in the tower sprays.
  • Identified new, high-efficiency packing and an improved inline mist eliminator to improve the system performance.
  • Made recommendations for improving efficiency through process and procedural changes.
  • Suggesting improved instrumentation and controls for monitoring and adjusting the process.

Based on the process evaluation, it was discovered that the spray tower, caustic pump, and other major pieces of equipment could continue to be used without replacement.  A staged installation plan was recommended to confirm the desired operation with the new packing and mist eliminator.

Industry Type

  • Metals and Materials Manufacturing

Utilized Skills

  • Emissions controls evaluation and improvement

Contact Us