Case 7 Natural Gas Straddle Pipeline Application

Loeated at the eastern terminus of the NOVA and Foothills (Alberta) pipeline systems and about one mile west of the Alberta/Saskatehewan border, the BP-Amoeo Empress NGL proeessing plant extraets liquids equivalent to approximately 2% of the (maximum value of) 5.2 Bef of natural gas that passes through the faeility every day. Most of the 

The BP-Amoco Empress plant complex consists of three interconnected facilities located on a one mile square site. It operates 24 hours a day, 365 days a year, employing 70 personnel who work two shifts. If the plant were to shut down for a period of time, suppliers would have to sell their product on the spot market and forego profits. Also, from the customer s perspective, even a plant with reserves would soon run out of products. 

The original plant (Phase 1) was constructed by Fluor in 1971, and can remove 45% of the ethane, 90% of the propane, and 100% of the butanes and condensates from the gas stream. Phase 1 has a capacity of 1.7 Bcfd. The second plant (Phase 2) can remove up to 70% of the ethane, 95% of the propane, and 100% of the butanes and 

The extraction process at BP-Amoco Empress begins with natural gas arriving at the plant at about 15°C and 600 psi pressure. The gas is dehydrated to a -90°C dewpoint by means of molecular sieves. Still at 600 psi, the gas is introduced into heat exchangers and cooled to -70°C, at which point it begins to liquify in a separator. 

Expansion turbines—three in Phase 1 and two in Phase 2—cool the gas to -90°C, at which point more liquid drops out in another separator. In this system, the cold methane gas emerges from the expansion turbines at a reduced pressure of 325 psi and is recirculated to the original heat exchanger to reduce the temperature of the natural gas entering the plant. 

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