Revamps 2023 Issue

Comanche III gas plant retrofit results

Pre-retrofit Retrofit performance Performance Predicted Actual

Ethane recovery mode Ethane recovery, % Propane recovery, % Ethane rejection mode Ethane recovery, % Propane recovery, %

93.0 98.5

99.5

99.9

100.0

45.0 94.0

57.1 99.9

55.0 99.9

Table 2

shutdown. The upgraded plant was started up in late 2018. Table 1 summarises the performance before the retrofit, the predicted retrofit performance, and the actual perfor- mance after the retrofit. The Dover Hennessey Gas Plant retrofit resulted in significantly higher product recoveries, more flexibility to either recover or reject ethane to adjust to ethane market conditions, and decreased power usage per MMSCFD of gas processed. Case study 2 The Comanche III Gas Processing Plant, owned by Brazos Midstream, was commissioned in January 2018. It was designed as a standard skid-mounted plant using GSP with a design capacity of 200 MMSCFD. At start-up, the recov- ery levels were approximately 93% ethane and slightly less than 99% propane. Although this was a relatively new modular NGL recov- ery plant, Brazos Midstream quickly developed a desire to achieve higher propane recoveries, both in ethane recov - ery and ethane rejection modes of operation. Based on the market needs, the goals of the retrofit were identified as follows: • Improve product recoveries, particularly increasing the propane recovery level to essentially 100% in ethane recov- ery mode and greater than 99.5% while rejecting ethane at a 55% recovery level. Ethane recovery of greater than 99% was also desired • Provide an option to increase plant throughput in the future. To provide the desired ultra-high ethane recovery and essentially 100% propane recovery, a process like RSV was clearly required. However, the RSV2 option was cho- sen because of the potential to process additional gas. It was also attractive because of the ability to connect the new equipment with minimal downtime, requiring only six tie-ins. Given the young age of the original GSP plant and the application of the RSV2 feed gas bypass, the retrofit did not require any modifications to the existing equipment. New equipment for the RSV2 retrofit included the following, along with associated piping and controls: • Absorber column • Absorber bottoms pumps • Recycle gas exchanger/reflux condenser. Figure 7 shows the new equipment during construction. The absorber appears on the left, while the new recycle gas

Figure 7 Absorber, left, and new heat exchanger seen during installation

drops and poor thermal performance. It was replaced as part of the retrofit • The expander/compressor was refurbished and fitted with new expander and compressor wheels to handle the retrofit conditions • The demethaniser internals were replaced to improve packing efficiency and handle higher vapour and liquid flows. New equipment for the GSP/Retro-Flex retrofit included the following, along with associated piping and controls: • Absorber column • Absorber bottoms pumps • Reflux condenser/subcooler • Cold refluxing module (CRM) • Demethaniser hot oil reboiler • Air-cooled product cooler (for ethane rejection mode) • Supplemental refrigeration compression. For this project, the CRM was constructed on top of the absorber, eliminating the need for additional pumps typi- cally required for a Retro-Flex retrofit. The new absorber (with the CRM attached on top) can be seen next to the existing column in Figure 6 . The addition of the new equipment required five tie-in points, which were completed during a planned plant

Revamps 2023