By: Frank Caprio | On: October 8, 2019
Today’s advanced oil refineries are far more versatile than those built even a decade ago; these high complexity refineries produce more valuable products using lower-cost feedstocks. This gives them a strong advantage in a global market where supply and demand is highly competitive and volatile, and the regulatory environment is ever changing. The drive to reduce feedstock costs has increased refiners’ interest in using bitumen, a heavy crude sourced from oil sands in western Canada. Bitumen is extremely thick — it can be a solid at room temperature — making it difficult to transport efficiently. Let’s look at some of the challenges refiners face in order to utilize bitumen feedstock.
Bitumen must be thinned in order for it to be pumped through a piping system and transported. One way to achieve this is to heat the product. Hot oil or steam may be used to increase the bitumen temperature to more than 300 degrees F., helping it to flow freely. Special heated rail cars or trailers must then be used to transport the bitumen for refining. These high operating temperatures can pose a safety hazard if the hot bitumen contacts any water-based emulsions like asphalt, potentially creating a steam flash. Injuries have occurred where water flashed into steam, causing the hot bitumen to splash through manways or other openings.
Any impurities in the media become more aggressive at high temperatures, so corrosion can be a problem. Bitumen can contain elevated sulfur levels, which can poison the catalysts used during refining operations. Other impurities may also be present, so hose and expansion joint alloys must be able to resist these corrosive conditions and aggressive environments. Using T316 stainless steels may not provide sufficient resistance in these situations.
Another way to transport bitumen is to mix it with other hydrocarbons to reduce its viscosity. Here, the bitumen is mixed with light crude oil or natural gas condensates (which are co-produced when drilling for oil and gas), creating a blend called diluted bitumen or “dilbit”. Synbit is similar to dilbit except the bitumen is synthesized to remove sulfur and other impurities. Depending on the refinery and the processes used, the dilbit may be refined as-is, or the condensates may be removed and reused to make the next batch of dilbit. Again, high-nickel alloys may be required depending on the amount of sulfur present.
There are other concerns when transferring dilbit. First, the presence of suspended solids can cause line plugging and erosion, which can also affect metal corrugated hoses and expansion joints. Solids can impact inside the corrugations of these products, causing them to deflect abnormally. As deflection occurs, excessive stresses are applied to the corrugation valleys, or roots, ultimately shortening the cycle life of the component. Special construction features may be required to prevent this build-up, thus improving service life by spreading out the bending stresses across the entire corrugation profile and reducing metal fatigue. Other concerns include potential erosion corrosion from high solids content and flow-accelerated corrosion from high flow velocities.
Even though dilbit’s composition is very similar to crude oil, it can present challenges. For example, there have been reports that dilbit becomes much more difficult to remediate after a spill, especially if there is a delay before cleanup operations begin. Unlike oil, which is lighter than water and can be skimmed off the surface, bitumen has the tendency to separate from the diluent, increasing its density and causing it to sink, hampering cleanup efforts.
Bitumen and dilbit applications
Hose Master provides many products designed specifically for this exotic form of oil extraction and transport. Much bitumen is extracted in-situ, typically performed by injecting steam through long horizontal pipes into the bed of bitumen underground. This steam heats the bitumen and drives it to the extraction well, where it is pumped to the surface. This Steam Assisted Gravity Drainage, or SAGD, uses expansion joints on the steam and extraction lines, as well as in the steam plant itself. Metal hoses are preferred for their high-temperature and corrosion-resistant characteristics during loading and unloading, and high-nickel alloy hoses and expansion joints handle everything from the diluents to the water treatment chemicals to the impurities removed during refining operations.
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