Modeling of Associating Mixtures for applications in the oil & gas and chemical industries
Advancing the chemical engineering fundamentals
Thermodynamics: Applications of Equations of State (T2-1b)
Keywords: equation of state, association, hydrogen bonding, oil&gas, chemicals
Thermodynamic properties and phase equilibria of many associating mixtures cannot often be modelled satisfactorily by conventional models e.g. cubic equations of state.
CPA (Cubic-Plus-Association) is an equation of state (EoS), which combines the SRK EoS with the association term of SAFT. For non-polar (non self-associating) compounds it reduces to SRK. The model was first published in 1996 and since then it has been developed and applied with success to binary systems containing water-alkanes and alcohol/glycol/acid-alkanes (both VLE and LLE) as well as ternary and multicomponent (V)LLE for water-alcohol (glycol)-alkanes and certain acid and amine-containing mixtures. The results for the multicomponent systems are predictions based on a single binary interaction parameter. Recent results include extension of the CPA model to glycol-aromatic hydrocarbons including multiphase multicomponent equilibria and gas hydrate calculations in combination with a van der Waals-Platteauw model.
CPA offers a substantial improvement over conventional models such as SRK in a number of cases, especially:
• liquid-liquid equilibria
• water-containing systems such as water-hydrocarbons (aliphatic, olefinic, aromatic)
• prediction of details of phase equilibria e.g. the azeotrope at low methanol concentrations of methanol-propane systems
• prediction of multicomponent multiphase equilibria from binary data (and parameters) without the need of multicomponent data
This presentation will summarize some previous highlights but will mostly outline new applications of the model with special emphasis to those of relevance to the petroleum and chemical industries:
• mixtures with gas hydrate inhibitors
• systems containing acid gases (CO2, H2S), water, methanol and hydrocarbons over extensive temperature and pressure ranges
• reservoir fluids in presence of water and methanol, glycols
• mixtures with polar and hydrogen bonding chemicals including organic acids.
Some comparisons with conventional thermodynamic models especially those combining cubic EoS with local composition activity coefficient models will also be included.
Presented Monday 17, 15:20 to 15:40, in session Thermodynamics: Applications of Equations of State (T2-1b).
