Distillate fuel oil supply mainly consists of diesel fuel used for transportation and of heating oil burned in furnaces and boilers. Over the last 20 years, the US Environmental Protection Agency (EPA) has regulated the level of sulphur contained in diesel fuel to enable reductions in harmful emissions of nitrogen oxides and particulate matter from diesel engines. Since 2006, the EIA has commented, most distillate fuel has had less than 15 ppm of sulphur, a drastic change from the early 1990s, when high sulphur diesel had an average sulphur content of 3000 ppm. This change has improved air quality by reducing sulphur emissions with only a minor impact on the average energy content of distillate fuel consumed in the US.
Diesel fuel supply is subdivided into the highway, non-road, locomotive and marine categories. Staring in 1993, the EPA required petroleum refiners and marketers to introduce diesel with sulphur content no higher than 500 ppm for highway use. Then in 2006, the limit for highway diesel was further tightened, as the EPA required no more than 15 ppm of sulphur by 2010. The EIA has updated its survey data collections several times in response to increasingly stringent limits on sulphur content, creating new distillate fuel categories to account for the new, lower sulphur diesel fuel types.
Tighter sulfur limits are also being applied to non-highway diesel. In 2007, the EPA required non-road, locomotive, and marine diesel (NRLM) suppliers to begin the transition to low sulphur and ultra low sulphur diesel. By 2014, this process was nearly complete. Diesel fuel prior to 1993 had an average sulphur content of 3000 ppm; the limited for ultra low sulphur diesel is 99.5%.
sulphur is removed from distillate fuel during refining via a reaction with hydrogen. This process is known as catalytic hydrotreating and strips away sulphur as well as nitrogen, oxygen and metals from hydrocarbon compounds. These reactions reduce the weight per gallon and a small portion of the thermal energy obtained from the combustion of a gallon of distillate fuel. The EIA’s calculation of the heat content for distillate fuel supply in the US reflects these changes, going from approximately 138.6 million Btu/gal. in 1994 to an estimated 136.5 million Btu/gal. last year. Heat content is a necessary component when comparing consumption across various physical units of energy, such as gallons of gasoline or cubic feet of natural as.
Edited from press release by Claira Lloyd
Read the article online at: https://www.hydrocarbonengineering.com/refining/25022015/distillate-fuel-sulfur-content/