An experimental and modeling study on incipient hydrate-forming conditions for ternary guests of carbon dioxide, nitrogen and sulfur dioxide

In carbon dioxide capture and sequestration (CCS) processes, captured CO₂ may encounter conditions of hydrate formation due to the presence of water. For stable, long-term operation of CCS processes, hydrate-phase equilibrium data are essential. Captured CO₂ from combustion of fossil fuel may include other impurities such as N₂ and SO₂. Phase equilibria including a single impurity (N₂ or SO₂) have been reported by other researchers, but no experimental observations have been obtained for ternary guest systems. In this work, the incipient hydrate-forming temperatures for a binary guest of CO₂ and N₂ and a ternary guest of CO₂, N₂ and SO₂ were experimentally measured at 2.0–3.5 MPa. An effect of the ratio between guest components and water was observed. The experimental results were compared with calculations using an equation of state based on a hydrogen-bonding nonrandom lattice fluid (NLF-HB) combined with the van der Waals-Platteeuw model. The model predictions were in good agreement with experimental data with an overall average deviation of 2.6%.