The authors will discuss the challenges involved in the design and predictive modeling of a proposed 1,200 mile (1,900 kilometer) liquid ethane pipeline. Comparisons between ethane and other common liquid product streams will be presented. The implications of these differences will be shown on how they relate to design consideration. Commercial considerations as well as project timing will also be discussed.
At the standard conditions of 60°F and 14.7 psia, ethane is an odorless colorless hydrocarbon gas. Ethane is an alkane that is a common component of natural gas. Ethane has a relatively high heating value of 1630 BTU. During the processing of natural gas, ethane and heavier hydrocarbons are removed from the rich natural gas stream in order to meet the pipeline quality specifications of a net heating value of 1100 BTU. Ethane is one of the lighter hydrocarbon components of natural gas as depicted in Table 2. One can see that the progression of heavier hydrocarbons from methane adds one carbon atom and 2 hydrogen atoms and a corresponding ~14.03 g/mol molecular weight increase. The removal of heavier hydrocarbons from the rich natural gas stream creates a lean natural gas stream and mixture of hydrocarbons liquids (natural gas liquids). Often this mixture of ethane, propane, butane and heavier hydrocarbons is referred to as a demethanized natural gas liquids (NGL) mixture. A majority of the ethane is transported in this NGL mixture to centralized locations. A small remainder of the ethane stays in the leaner natural gas stream. At these centralized locations, component product streams are created through fractionation of the demethanized NGL mixture, and sold as a commodity. The commoditized components are then delivered to the end user for use. In the United States ethane futures are sold on the NYMEX electronic futures exchange.