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The shale gas revolution in the US has resulted in an abundance of NGL in the marketplace. The increase in output has also produced an excess of ethane, leading to a decrease in price for the chemical. In response to this dynamic, midstream processors have been exploring ways to increase NGL production while limiting the amount of ethane content.
A number of ways exist to recover NGL from gas streams. They range from simple Joule-Thompson ( J-T) units and mechanical refrigeration to more complex NGL recovery designs, such as cryogenic turboexpander plants. One of the most commonly used technologies throughout the industry over the past 30 years has been the Gas Subcooled Process.a
Gas-subcooled (GS) plants can be operated in both ethane- recovery and ethane-rejection mode. This type of facility is often referred to as a dual-mode process design, and it provides owner-operators with the flexibility to adjust plant operations to meet market demand.
Ethane is a valuable hydrocarbon component that can be recovered as a liquid from natural gas streams. Typically, when the price of ethane is high, processors recover ethane as part of the NGL stream, where it is then fractionated and sold as a feedstock to the petrochemical industry to make ethylene. When the price of ethane is low, it is more profitable for processing facilities to reject it to the sales gas stream.
Over the last several years, large increases in available US NGL volumes have been met with insufficient increases in industrial ethane demand. This scenario, coupled with regional transportation bottlenecks, has caused ethane prices to be severely depressed and made it economical for NGL recovery plants to reject as much ethane as possible.
For standard GS plants operating in ethane-rejection mode, this means unavoidably rejecting some of the still-valuable propane and butane to sales gas, which negatively impacts plant profitability. As a result, significant economic value can be generated by implementing flexible processing solutions that enable GS plants to operate in high-ethane-recovery or full-ethane-rejection mode, without sacrificing propane and butane recovery.
Here, a technical evaluation of solutions for improving propane recovery and enhancing ethane rejection at GS facilities is provided.
Overview of standard GS technology. Compared to newer- generation dual-mode process technologies, GS technology is economically limited. It...