Professional Assessment of Natural Gas Liquids Recovery Enhancement Through Turboexpander Technology at the Obiafu Gas Processing Facility, Rivers State

Natural gas liquids recovery is a key commercial driver for gas processing plants in Nigeria, and turboexpander technology offers the highest recovery efficiency for ethane, propane, and butane extraction compared to conventional refrigeration or lean oil absorption processes. This study professionally assesses the engineering and economic case for implementing turboexpander-based NGL recovery enhancement at the Obiafu Gas Processing Facility, Rivers State, South South Nigeria. Current facility throughput, feed gas composition, and existing cryogenic refrigeration train configuration are reviewed to establish the baseline NGL recovery rate of 48 percent for ethane and 71 percent for propane across the processed streams. A turboexpander plant design is developed for integration with the existing facility, incorporating expander-compressor trains, a demethaniser column, and a heat exchanger network optimised for maximum cold recovery. Process simulation was performed using Aspen HYSYS to predict NGL recovery rates under the turboexpander scheme. Results indicate that ethane recovery improves to 78 percent and propane recovery to 94 percent under the turboexpander configuration, representing a combined NGL production increase of 3,200 barrels per day at design throughput. An economic evaluation using a ten-year cash flow model confirms a project IRR of 26 percent at LPG prices of 450 USD per tonne, with payback period of 3.8 years. Detailed engineering scope and integration challenges are discussed. Keywords: NGL recovery, turboexpander, gas processing, Obiafu, Rivers State.