With an increasing focus on refinery employee safety and community stewardship, high H2S levels in asphalt are a concern to refiners and terminal operators. Challenges such as high temperatures have limited the chemistry selection for effective chemical scavenging. The Nalco Champion patented use of organometallic scavengers has allowed our partners to successfully manage H2S levels in asphalt applications over the past two decades.
Asphalt (bitumen) may contain very high vapor phase concentrations of hydrogen sulfide (H2S). H2S concentrations can easily exceed 20,000 ppm in the headspace of asphalt storage tanks; these concentrations present an immediate danger to personnel exposed through transport or handling of this product. This high concentration is due to the concentration of sulfur compounds in asphalt feedstock, such as vacuum tower bottoms, elevated storage temperatures, and the propensity of H2S to leave the liquid phase of asphalt in favor of the vapor phase. Moreover, unlike finished fuels such as gasoline and diesel, asphalt does not go through any sweetening processes during production.
High production and storage temperatures limit the choices for effective H2S scavengers for asphalt. Nalco Champion has more than 20 years of experience successfully producing and applying metal-based scavengers for asphalt. These metal-based additives have an increased capacity to scavenge H2S versus conventional scavengers and can be applied at the elevated temperatures typical of asphalt production and storage. The Nalco Champion patented H2S scavengers for asphalt have been shown to have no detrimental impact on finished asphalt performance grade specifications.