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An asphalt terminal in the United States was experiencing issues with hydrogen sulfide (H2S) regeneration when a polyphosphoric acid (PPA) modifier was added to their asphalt product. Though the terminal had a scavenger program in place for H2S abatement, it was not controlling the H2S regeneration problem. This triggered an increase in personal H2S monitor alarms at the loading area, and violated the terminal’s internal safety regulations. The terminal was faced with the choice of either discontinuing their use of the PPA asphalt modifier or finding an alternate chemical H2S scavenging program that could effectively mitigate PPA-based H2S regeneration and help keep their plant personnel safe. They chose to find an alternate chemical scavenger treatment and reached out to Baker Hughes, a GE company (BHGE), for help.

BHGE recommended a SULFIX™ PPA-resistant H2S scavenger program as an effective single-treatment solution for this application. The scavenger was applied to the asphalt after the addition of elemental sulfur by using the terminal’s existing on-site injection system. This allowed for a quick transition and eliminated the need for additional equipment expenditures.

Initial testing indicated the H2S concentration dropped to 0 ppm quickly after implementing the SULFIX PPA-resistant scavenger. The PPA modifier was then added to the asphalt to complete the modification process. Three concentrations of the SULFIX scavenger were tested; each dosage achieved the desired effect of reducing the PPA-based H2S regeneration by 50%, 80%, and 100% relative to the existing scavenger application. See Figure 1.

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Challenges & Results


  • Experienced H2S regeneration after adding PPA to asphalt
  • Increased hazardous exposure to H2S and safety code violations
  • Continued desire to use PPA modifiers


  • Mitigated H2S to 0 ppm after initial application to asphalt
  • Reduced H2S regeneration beyond target rates after PPA was added to asphalt
  • Avoided additional HSE risks and safety violations