Search for a command to run...
Abstract Effective dehydration of CO2 streams is critical to mitigate corrosion and hydrate risks during pipeline transport, particularly for impurity-rich CO2 carbon capture and storage (CCS) systems, where unmanaged water content poses significant risks of pipeline corrosion and hydrate blockages. This study aims to define dehydration thresholds for CO2 pipelines and validates thermodynamic predictions for glycol–CO2 interactions to support reliable pipeline design and operation. The dehydration method will be evaluated from technical and economic feasibility perspective for adsorption (molecular sieves), adsorption (silica gel) and absorption (Tri-ethylene Glycol (TEG)), and compare CAPEX/OPEX at various pipeline operating conditions. The study employs pipeline transient multiphase flow simulation software OLGA and thermodynamic modelling software PVTsim to analyse pipeline operating scenarios. Dehydration thresholds and hydrate formation risks are quantified for impure (CH4, N2, H2, CO, Ar, and O2) CO2 streams. Case studies ("Low CO2 85 mol%" vs. "High CO2 98 mol%" compositions) validate dehydration thresholds, while sensitivity analyses assess impacts of pipeline overall heat transfer coefficient (OHTC) and impurity concentrations. A published dataset on TEG solubility in CO2 was benchmarked using SRK-HV, PR-HV, SRK-CPA, and PR-CPA models. A case study is performed for typical CCS pipeline operating conditions. Dehydration methods are compared via energy consumption, capital/operational costs (CAPEX/OPEX), and performance (e.g., dew points). Key findings reveal that transient depressurization can enter hydrate regions even when steady state operation is hydrate free. The dehydration requirements for varying impurity profiles and operational conditions are quantified. The PR-CPA equation of state most accurately reproduced CO2–glycol phase behavior, while cubic EoS with Huron–Vidal mixing under predicted glycol solubility in dense CO2. Thermodynamic analysis shows that even trace levels of dissolved TEG substantially shift the water dewpoint boundary, significantly reducing the operating envelope; once glycol saturation is exceeded, downstream water/TEG condensation can occur, creating an unacceptable corrosion risk. Although adsorption dehydration using molecular sieves entails higher energy and capital costs, it provides the only technically robust solution that preserves phase stability under transient CCS pipeline conditions. In contrast, absorption methods, including TEG and silica gel, may satisfy nominal outlet water specifications but do not ensure sufficient integrity margins for CCS transport.