Overview


Challenges
  • Extensive H2S generation
  • Customer unable to continue PPA program due to safety concerns
Results
  • Lowered H2S by 70%
  • Enabled customer to resume production of PPA modified ashphalt
  • Eliminated safety risks
Case study details

Using polyphosphoric acid (PPA) to modify the stiffness of asphalt is an effective method that is growing in popularity among many asphalt terminals in the US. The downside to a treatment is that it can be dangerous to use due to associated regeneration of hydrogen sulfide (H2S).

An asphalt producer in the Western United States had a typical polymer- modified asphalt (PMA) production process that involved transferring 74 to 36 grade asphalt from a bulk storage tank to a reaction vessel, where asphalt reacted with polymer and elemental sulfur at 300 °F (149 °C). The resulting 64 to 28 grade asphalt was then pumped to trucks in individual batches. The final step of the modification, the addition of PPA, was accomplished in- line as asphalt was being pumped into the trucks.

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