Project Synopsis

Investigate reasons for air pollution control (APC) system anomalies causing severe corrosion of components, instrumentation and other problems. Recommend, design and assist in implementing effective solutions.

Project Summary


The client owns and operates a batch/continuous chemical production facility that produces several chlorinated compound products.  Process Engineering Associates, LLC (PROCESS) was contracted by the company corporate engineering group to conduct a preliminary process evaluation of the facility incineration system.  More specifically, PROCESS was asked to investigate reasons for air pollution control (APC) system control anomalies that were resulting in multiple operating problems, chief among them being severe HCl corrosion of components and instrumentation downstream of the APC system.  The project included these tasks:

  • Request for, and review of incineration system engineering and operations information
  • A site visit to the facility for the purposes of observing incineration system and associated controls operation, interviewing incineration system engineering and operations personnel, and obtaining additional engineering and operations information as required
  • Development of conclusions relative to the operating problems being experienced as well as recommendations for mitigating the operating problems

During the site trip, review of control parameters historical trending revealed that significant swings in the APC system three-stage venturi scrubber liquor pH was the cause of the system corrosion.  Controller tuning eliminated probably 70% of the corrosion-causing operation time, during steady-state operation, but additional process / control system changes were required to eliminate the pH swings during transitional periods (periods when incinerator feed rate or feed composition was being changed).  To this end, PROCESS developed the following recommendations:

  • Relocate the scrubber reagents (25% caustic and makeup water) feed tie-in points to eliminate a significant transportation lag that was resulting in poor-quality scrubber liquor being fed to the scrubber nozzles for extended periods of time
  • Modify the process control scheme to combine three independent control loops into one ratio control and one independent loop to eliminate additional control system lags and improve overall control stability

The results of the evaluation were compiled by PROCESS into a project report that included a process control diagram (PCD) showing the modified scrubber and control system.

It was estimated that the modifications set forth above will result in an additional 20-25% reduction in corrosion-causing operation time.  It is also noted that this project (including the implementation of these recommendations) was done on a fast-track basis in preparation for a trial burn that was to commence less than five weeks after the commissioning of this project.

Subsequent to the implementation of the changes noted above, PROCESS was called to the plant to tune the control system and start up the modified process.  Startup and steady-state operation were successfully achieved. 

Industry Type

  • Batch Specialty Chemical

Utilized Skills

  • Plant process troubleshooting
  • Pollution control equipment expertise
  • On-site startup assistance

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