Project Synopsis

Perform a technical and economic process alternatives evaluation for an improved sulfuric acid dilution system as part of an existing industrial waste water treatment facility at a specialty metals production plant.

Project Summary


The client, a specialty metals manufacturing company, contracted Process Engineering Associates, LLC (PROCESS) to complete an alternatives evaluation for an existing dilute sulfuric acid system utilized in the facility’s Waste Water Treatment Plant (WWTP).    Ultimately, the goal of the project was to identify the most cost effective solution for replacement or modification of the sulfuric acid dilution system.

Specific tasks for this project included:

  • Generating a draft design basis that included project goals, constraints, and requirements in addition to any regulatory design constraints that would affect the technical and economic evaluations.
  • Preparation of a process flow diagram (PFD) for the WWTP to include volumetric flow rates and acid addition rates.  The maximum waste flow rates and pH ranges were established by reviewing the WWTP’s operating data.  PROCESS utilized its licensed commercial computer process simulation software to help determine the acid addition rates required to neutralize the basic waste with both dilute sulfuric acid (30 wt%) and concentrated sulfuric acid (93 wt%). 
  • Preparation of piping and instrumentation diagrams (P&IDs) for the WWTP so that any design changes to the acid dilution system could be better defined.  No P&IDs existed at the start of this project for the WWTP.
  • Preparation of a functional description for the facility’s WWTP to specifically define valve sequencing and alarms/interlocks during operation.
  • Facilitation and participation in a Process Hazards Analysis (PHA) for the entire WWTP.  A final report with recommendations was issued to the client. 
  • Performing a technical evaluation to determine viable options for replacement of the WWTP acid dilution system.  Four (4) options were identified and evaluated for technical feasibility. The options were screened based on potential to integrate the alternative into the existing processes, proven performance of the system, and technical difficulties and uncertainties associated with the system.  Safety, health, and environmental (SH&E) issues were also considered. A summary of this evaluation was issued to the client for review and comment.  All four options were considered technically feasible and carried through for further economic evaluation.
  • Performing an economic evaluation of the four options.  The evaluation included generating block flow diagrams for each option, obtaining budget costs for major pieces of equipment (e.g., pumps, tanks), using installation factors to calculate and installed capital cost, and calculating related operating costs.
  • Generation of a final summary report with recommendations.

Installation of a new tank and the purchase of dilute sulfuric acid was selected as a short-term option by the client due to specific pricing available at the time.  The long term option chosen was to install a new small day tank for concentrated sulfuric acid at the WWTP and use an in-line mixing system to dilute the acid prior to injection into the pH adjustment tanks. 


Industry Type

  • Specialty Metals Manufacturing
  • Industrial Waste Water Treatment

Utilized Skills

  • pH adjustment systems design
  • Technical and economic process alternatives evaluation

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