Process Simulation and Equipment Sizing of a Modular Skid-Mounted CNG Compression Plant for Stranded Gas Utilization

This study presents the process simulation and equipment sizing of a modular skid-mounted compressed natural

gas (CNG) compression plant designed for stranded gas utilization in the Western Niger Delta. Using Aspen HYSYS V14

with the Peng-Robinson equation of state, a steady-state model was developed to process flare gas from seven flow stations

within OML 30 and OML 34, with a combined average flaring rate of 22.98 MMscfd. The simulation achieved full

convergence with near-perfect mass and energy balance closure (relative error < 1x10-10). The three-stage main compression

train, complemented by an inlet compressor and gas purification unit, delivers 18.08 MMscfd of vehicular-grade CNG

meeting ISO 15403 specifications (99.9 mol% methane, 205 barg, -40℃). The compression train, comprising K-101, K-102,

K-103, achieves an overall pressure ratio of 20.8 with a total shaft power requirement of 3,002 kW. Equipment sizing was

performed using standard engineering equations and industry criteria, yielding specifications for separators (DN600x2.0

m), heat exchangers (thermal duties ranging from 869 kW to 1,702kW), and compressors (driver ratings from 350kW to

1,600kW). The results demonstrate that modular skid-mounted CNG compression offers a technicaly feasible solution for

monetizing stranded gas, with potential for NGL recovery to enhance project economies.