Hydrofluoric Acid (HF) Treatment Systems

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Overview

Hydrofluoric acid (HF) wastewater is generated in various industrial and semiconductor processes. Typical HF concentrations in wastewater can range from 50 ppm to several thousand ppm, while discharge limits are generally between 10–20 ppm, and can be reduced to as low as 2 ppm with additional treatment steps.

Burt Process HF treatment systems are designed to safely neutralize, precipitate, and remove fluoride ions from wastewater streams, ensuring compliance with environmental discharge standards. These systems typically combine chemical reaction processes, automated pH control, precipitation and settling, and polishing filtration for complete fluoride removal. In both batch and flow-through designs, Burt Process engineers work with our clients to ensure proper system design and integration, while incorporating safety as a primary design concern.

Treatment Process Overview

  1. pH Adjustment
    The pH of the diluted HF stream is raised to approximately 9.0–9.5 using a caustic solution (such as sodium hydroxide). This creates the ideal conditions for fluoride precipitation.
  2. Fluoride Precipitation
    Calcium chloride is introduced to react with fluoride ions, forming calcium fluoride (CaF₂), an insoluble compound that can be separated from the water:
    Ca²⁺ + 2F⁻ → CaF₂ (solid)
  3. Coagulation and Flocculation
    Polymers may be added to promote floc formation, which helps bind fine particulates into larger aggregates for improved settling performance.
  1. Settling and Decanting
    The treated solution passes through a settling tank/clarifier where solids separate by gravity. Clear supernatant liquid is decanted from the top, and sludge is collected at the bottom for removal.
  2. Solids Handling
    The calcium fluoride sludge is transferred to a waste holding drum or collection vessel for proper disposal. This can be tied to a filter press or other device to form a cake which can be taken off site.
  3. Final Polishing
    A cartridge filtration stage and dual resin beds (primary and polishing) are used to remove any residual fluoride, ensuring that effluent levels meet strict discharge regulations.

Components and Features

  • Treatment tanks and Equalization tank options: constructed from chemical-resistant materials (e.g., polypropylene, fire-retardant polypropylene, PVDF) with double walled options available with leak detection.
  • HF-rated pH and HF sensors for accurate process monitoring.
  • Reagent assemblies, with either onboard or owner supplied reagent tanks, with precision volumetric metering pumps and peristaltic pumps for reagent injection.
  • Polymer blending systems and polymer injection systems.
  • Complete effluent monitoring for complete discharge compliance.
  • Different solids options available such as clarifiers or filter presses.
  • Additional treatment options for low level HF discharge such as resin treatment and additional treatment

Optional Enhancements

  • Resin bed regeneration systems.
  • Remote monitoring and data logging.
  • Clarifiers and filter press for solids handling.
  • Double wall plumbing and system double containment.
  • Fire retardant materials available.
  • Spray and splash protection and cabinet-based HF and reagent chemical systems.
  • Automated sludge dewatering equipment.
  • Temperature control systems for reaction management
  • Custom material selections for compatibility with site-specific chemical conditions

Control System Integration

  • HF system panels include complete integration with all system instrumentation such as pH, fluoride, leak detection as well as level & flow instrumentation, and all modular components.
  • Options for Allen-Bradley or Siemens PLC controlled systems are available, ensuring smooth deployment into existing facility controls environments.
  • Options to add BAS communication modules are available.
  • For systems that require high voltage components, voltage transformers can be integrated to segregate high voltage components & allow for the use of low voltage components for process variable transmitters & manual controls.
  • System control panels are pre-mounted & pre-wired to the system skid & skid components.
  • Electrical conduit such as PVC rigid & flexible PolyTuff is utilized for system wiring.

System Advantages

  • Safe handling of aggressive HF waste streams with minimal operator exposure.
  • Automated pH control and dosing reduce manual intervention.
  • High fluoride removal efficiency through staged precipitation and polishing.
  • Built-in safeguards to protect equipment and personnel.
  • Modular and adaptable design for varying flow rates, batch sizes, or future process expansions.

Implementation

Factory Acceptance Testing (FAT): Systems are rigorously tested at BPE’s facility to ensure compliance with client specifications and operational standards. Clients have the option to visit factory to witness FAT testing.

Startup and Training (SAT):
  • On-site support includes:
    • System startup and operational verification.
    • Training for client personnel on system operation, maintenance, and troubleshooting.
  • Field Services: Installation is guided by detailed engineering documentation provided by Burt Process. Field service installations can also be performed by Burt Process technicians upon request.

Documentation & Support

Complete engineering package with:

  • P&IDs.
  • Ladder diagrams.
  • BOM cross references.
  • CAD system layout.
  • 3D modeling.