Rigorous Modeling and Constrained Optimization of a Monoethylene Glycol (MEG) Dehydration Process: A Kokori Field Case Study

Abstract

Abstract Glycol dehydration is a widely used process for water removal in the oil and gas industry. The presence of excess water in natural gas can lead to corrosion and hydrate formation along the gas pipelines. Tri-Ethylene Glycol (TEG) is the commonly used solvent for glycol dehydration due to its high water absorption capacity. However, despite its operational benefits, the main environmental concern associated with TEG is the emission of benzene, toluene, ethylbenzene and xylene (BTEX) compounds to the atmosphere, primarily during glycol regeneration. Mono-ethylene glycol (MEG) has attracted attention in recent literature as a dehydration solvent which lowers BTEX volatility under controlled operating conditions. This study develops an integrated simulation and optimization framework for MEG-based natural gas dehydration. The framework combines steady-state modeling in Aspen Plus® with constrained optimization in MATLAB® to minimize BTEX emissions while meeting gas dew point and energy constraints. A rigorous dehydration model was developed using Kokori field natural gas compositions and the Peng–Robinson equation of state. Key operating parameters such as absorber pressure and temperature, glycol circulation rate and regeneration temperature were analyzed to assess their impact on water removal efficiency, BTEX emissions and reboiler energy demand. The optimal MEG circulation rate was determined using MATLAB's fmincon solver, resulting in a significant reduction in BTEX emissions while keeping treated gas water content below 7 lb H2O/MMscf and maintaining reboiler energy within the acceptable limits. The framework provides an optimized, low-emission strategy for natural gas dehydration.