Fuel combustion emissions are primarily nitrogen oxides (NOx), sulfur dioxide(SO2), carbon monoxide(CO) and minor amounts of particulate matter and volatile organic compounds (VOCs), as well as carbon dioxide. These emissions come from the top of tall heater and boiler stacks (150 to 250 feet tall), at high temperatures (300 to 700 °F), and high velocities (15 to 30 feet per second), rising hundreds of feet into the air where they begin to disperse.
Fugitive emissions come from vapor leaks from tank seals, valves, flanges, pump and compressor seals and from moving, loading and storing petroleum coke. Most of the leaks from the processing equipment are VOCs while the petroleum coke fugitive emissions are primarily particulate matter. These emissions are generally at ambient temperature and occur close to the ground.
Process emissions come from just 7 of the regulated stacks in the refinery: the Fluid Catalytic Cracking Unit (FCCU), the 3 sulfur recovery plants, two reformers and the flare system.
The 1st bar chart entitled "Historic emissions - releases to air" shows that over the past decade, total air emissions of criteria pollutants from the refinery have decreased by 70%. Since 1997, FHR has done the following to reduce emissions:
