Project Synopsis

Provide an independent 3rd party due diligence technical review of an HCl purification and recovery system, as well as provide insight and recommendations on incorporating the system into existing facility operations.

Project Summary

A specialty engineering company based in Australia contracted Process Engineering International, LLC (PROCESS) to provide process engineering services and a due diligence technical review for a vendor supplied HCl purification system, as well as provide insight and recommendations on incorporating the system into existing facility operations.  The client was considering use of a commercial recovery system to purify hydrochloric acid (HCl) that has been used to regenerate an ion exchange system.  The system is to be applied to an Australian minerals mine site that was undergoing infrastructure upgrades.  The scope of the evaluation by PROCESS included a review of the chemistry and thermodynamics of the process, review of the heat and material balance, an evaluation of the proposed process equipment and materials of construction, and providing a professional opinion of the process design.

The incoming aqueous HCl solution is a waste acid stream that will contain various metals including antimony, bismuth, and arsenic.  The system is being designed to recover as much of the metals as possible in a separate stream while recovering a 20-weight percent aqueous HCl solution.  A distillate stream of slightly acidic water will also be produced.  The waste acid stream is produced during regeneration of the resin in an ion-exchange system (proposed, supplied by others).  The composition of the waste acid stream is primarily H2O with HCl, with smaller amounts of chlorinated metals, of which Bismuth Chloride (BiCl3) is the greatest contributor.

The recovery process is a bulk separation process based on forced-circulation flash separation (high volume, high pressure flash).  Flash overheads are routed to a multi-trayed distillation unit that produces a slightly acidic aqueous distillate and an aqueous twenty weight percent HCl stream.  Acid purity is constrained by the azeotrope corresponding to the process conditions.  Flash bottoms are forced-circulated back through the flash system along with the fresh feed.  A metals-rich purge stream is removed to control solids buildup.

PROCESS performed due diligence on the process and provided the client with a list of recommendations for future work. PROCESS also developed a Risk Assessment that profiled the inherent process, and environmental and operational risks associated with pursuing the project. The client is now considering the next steps to take.

Industry Type

Mining and Minerals Processing


Utilized Skills

  • Independent technical design evaluation
  • Process improvements identification
  • Process risk assessment.

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