The facility is designed to process 200 million cubic feet (mmcf) of sour gas per day, which provides the source for three commercialized products: gas to fuel homes and industry, natural gas liquids and sulfur.
The original source of sour gas is from the Shell/Marubeni Fairway Field, which is four miles south of Dauphin Island, Alabama, and about 17 miles southeast of the Yellowhammer Plant. Fairway currently produces from multiple jacket wells, which send bulk production via in-field flowlines to a central production facility (CPF).
At the CPF, the sour gas and any associated liquids are separated. The sour gas is then either fed into the platform’s field gas compressor or directly into a 16” gas gathering pipeline. The liquids are fed into an 8” pipeline. Both the sour gas and liquid pipelines run to the Yellowhammer Plant for further processing.
The plant also has processing agreements to gather and treat raw gas produced from certain offshore fields operated by Chevron in Viosca Knoll. Chevron production is received at the Fairway platform and then transported to the Yellowhammer Plant via a 12” pipeline.
Before Shell markets gas from its wells, it is processed to remove H2S and other contaminants, including carbon dioxide and water. Once this initial processing step is completed, this "sweet" gas is dehydrated and, if necessary, refrigerated to allow for condensation and removal of heavy hydrocarbon components and is then ready for market.
The removed H2S and CO2 are together known as "acid gas" and are fed to the Claus Sulfur Recovery Unit, which produces liquid sulfur from the H2S.
To improve the efficiency of sulfur recovery, the recovery unit is equipped with a Shell Claus Offgas Treating (SCOT) tail gas cleanup unit to reduce sulfur dioxide emissions. This process is designed to recover 99.7% of the sulfur.
Any heavy hydrocarbon components, or Natural Gas Liquids (NGLs), that are removed from the gas by refrigeration are then transported to customers via tanker trucks and later separated into marketable components including ethane, propane and butane.
Shell operates the Yellowhammer Plant, as well as the Fairway offshore field, with 30 Shell employees and various contractors. It recently marked its 15th anniversary with a celebratory event for employees, contractors and stakeholders.
Shell supports a number of agencies and community groups in the area, such as the Alabama Coastal Foundation, the Dauphin Island Sea Lab and the Mobile Child Advocacy Center.
