Shell doubles capacity at U.K. gas plant

Following redevelopment of North Sea Brent field and development of new central North Sea fields, Shell U.K. Exploration & Production has expanded gas processing capacity at St. Fergus terminal near Aberdeen. Upgrading work carried out during field shutdowns in 1996 and 1997 expanded the plant's capacity to 1.5 bcfd of gas from 700 MMcfd. The upgrade included replacement of two turboexpanders in the plant's demethanizer unit with new Rotoflow units from Atlas Copco Inc., New York. One

April 20, 1998

2 min read

Upgrading work carried out during field shutdowns in 1996 and 1997 expanded the plant's capacity to 1.5 bcfd of gas from 700 MMcfd. The upgrade included replacement of two turboexpanders in the plant's demethanizer unit with new Rotoflow units from Atlas Copco Inc., New York. One of the new units is shown in the photograph.

At St. Fergus Shell Expro receives gas from its central North Sea and Brent fields via the Flags and Fulmar gas export lines. There the gas is dried, with natural gas delivered to Transco for distribution in the national grid, and natural gas liquids sent by pipeline to the Mossmorran fractionation plant near Edinburgh.

The turboexpanders receive gas at rates as high as 420 metric tons/hr and reduce the pressure to 18 bar from 56 bar. This almost liquefies the gas and improves separation in the St. Fergus fractionation tower.

Atlas Copco claims the turboexpanders helped Shell improve productivity in two ways: their higher capacity improved ethane recovery by reducing pressure at the column, and increasing inlet pressure on the export compressors increased gas export capacity.

Frank Oliver, senior sales engineer at Atlas Copco, said: "Shell examined the design process of our machine and competitive products. The most important criterion was the package size, since the machines had to fit into the space occupied by the lower-capacity units they were replacing."