TABLE OF CONTENTS Most natural gas is processed to remove the heavier hydrocarbon liquids from the natural gas stream. These heavier hydrocarbon liquids, commonly referred to as natural gas liquids (NGLs), include ethane, propane, butanes, and natural gasoline (condensate). Recovery of NGL components in gas not only may be required for hydrocarbon dew point control in a natural gas stream (to avoid the unsafe formation of a liquid phase during transport), but also yields a source of revenue, as NGLs normally have significantly greater value as separate marketable products than as part of the natural gas stream. Lighter NGL fractions, such as ethane, propane, and butanes, can be sold as fuel or feedstock to refineries and petrochemical plants, while the heavier portion can be used as gasoline-blending stock. The price difference between selling NGL as a liquid and as fuel, commonly referred to as the "shrinkage value," often dictates the recovery level desired by the gas processors. Regardless of the economic incentive, however, gas usually must be processed to meet the specification for safe delivery and combustion. Hence, NGL recovery profitability is not the only factor in determining the degree of NGL extraction. The removal of natural gas liquids usually takes place in a relatively centralized processing plant, where the recovered NGLs are then treated to meet commercial specifications before moving into the NGL transportation infrastructure.
This chapter briefly presents the basic processes used to separate natural gas liquids from the gas, fractionating them into their various components, and describes different...
