Exergy comparison of single-shaft and multiple-paralleled compressor schemes in offshore processing of CO2-Rich natural gas

Exergy comparison of single-shaft and multiple-paralleled compressor schemes in offshore processing of CO2-Rich natural gas

CO emissions

Exergy analysis

Anti-surge recycle

Centrifugal compressors

CO-Rich natural gas

Offshore gas processing

Deepwater oil and associated gas productions resort to floating rigs operating at continuously decreasing gas-loads during the last three quarters of the field campaign. As centrifugal compressors are sized at maximum loads, anti-surge recycles are used making operation inefficient in terms of power consumption and emissions per oil barrel produced. Smaller paralleled compressors and variable-speed drivers are investigated at peak and partial gas-loads and compared to traditional anti-surge recycle designs in terms of exergy efficiency, investment, footprint and emissions. Oversized compressors with anti-surge recycles result in almost constant power consumption along process lifespan, regardless the gas-load, increasing fuel and CO2 intensities as gas-load decreases and attaining exergy efficiencies of 49% and 83% at 25% and 100% gas-loads, respectively. On the other hand, with variable-speed drivers and smaller paralleled compressors, power consumption becomes proportional to gas-load with exergy efficiencies always between 80% and 88%, and attaining 11% and 39% less power consumptions at 100% and 25% gas-loads. Moreover, CO2 intensity and investment are, respectively 34% and 3% less than in traditional layouts with oversized compressors. These savings resulted from eliminating a gas turbine thanks to lower power demand when no anti-surge recycles are used.

Journal of Natural Gas Science and Engineering

2020-09-01

Cruz, Matheus de Andrade

Araújo, Ofélia de Queiroz F.

de Medeiros, José Luiz

journalArticle

FY3VP86Z

1875-5100

10.1016/j.jngse.2020.103390