Objective Aiming at the issues of non-running expander, non-optimized main process parameters and difficult operation in large-scale natural gas cryogenic process facility, the approaches of expander commissioning, optimizing main process parameters in natural gas liquid (NGL)recovery unit to improve ethane recovery rate are researched.

Methods Based on process models by Aspen HYSYS simulation software, the effects of expander commissioning and optimizing main process parameters such as low-temperature separator (LTS) temperature, reflux lean gas flow rate, sub-cooled gas flow rate on improving ethane recovery rate and the practical ethane production are compared and investigated respectively.

Results The LTS temperature has been optimized to the range of -68.8 ℃ to -68.0 ℃. The reflux lean gas temperature and flow rate have been adjusted to the range of -101.45 ℃ to -100.05 ℃ and (7.38-7.60)×10⁴ m³/h, respectively. The sub-cooled gas temperature and flow rate have been adjusted to the range of -101.48 ℃ to-100.45 ℃ and (7.45-7.63)×10⁴ m³/h, respectively. After the above applications of these efficient measures in the natural gas cryogenic facility and field test, annual NGL production has already increased 175 600 tons.

Conclusions After the implementation of these measures, the ethane average recovery rate has been increased from 30.0% to more than 90.8%. It can not only obtain huge economic benefits, but also has a good prospect of promotion and application.