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Making clean products out of dirty raw materials
FHR processes a type of crude oil known as "heavy, sour" crude oil - heavy, because it contains more asphalt than most crudes, and sour because it contains a lot of sulfur. In order to meet state and federal standards for clean burning transportation fuels, FHR must treat the oil to remove sulfur and other contaminants.
The treating process starts with the desalters. Crude oil contains a small percentage of salt water (which is present in the rock formations from which it is pumped) and a small amount of solids, which must be removed so that they do not plug up or corrode the processing equipment. The water and solids do not form separate layers, but are mixed in with the oil in an emulsion. To break the emulsion, chemicals are added to the crude oil, and the oil passes through an electrically charged grid, which separates the oil from the water and solids. The oil is washed with additional water to be sure all the salt and solids are removed, and the water, salts and solids are sent to the wastewater treatment plant where oil and solids are recovered. The oil and solids are returned to the process to make more products.
Once the crude oil has been separated into its various fractions, it must be treated to remove the sulfur. FHR uses hydrogen and a molybdenum-cobalt catalyst to remove sulfur from gasoline, jet fuel and diesel fuel, and to pre-treat the gasoil before it is cracked. The sulfur combines with the hydrogen to form hydrogen sulfide, a very smelly, toxic chemical. FHR uses an amine scrubber to remove the hydrogen sulfide from the hydrogen and fuel gas, and recovers it as elemental sulfur in three sulfur recovery units. Sulfur is sold as a by-product or converted to sulfuric acid, which FHR uses as a catalyst in other processes.
Some streams, like LPG and some light gasoline streams, are treated with caustic soda to remove the sulfur, and then washed with water to neutralize the oil and remove the caustic soda and sulfur.
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