Thermodynamic (non)co-operation between Phase Equilibria and Ionic Dissociation of Organic acids in Water/Condensate/Gas systems

Amrit Kalra, Raymond French, Sheila Dubey, Ashok Dewan

We studied Phase Equilibria and ionic properties of four organic acids (formic, acetic, propionic, and butyric) under varying conditions of pH, temperature, pressure, and fluid compositions. Organic acids are comparatively weak acids (relative to HCl and H2SO4) and show a very interesting competition between phase behavior and ionic dissociation, especially in the acidic pH range below six. It is well known that at higher pH, organic acids are primarily present in the ionic form and undissociated molecular form is almost absent. Because of this ionic dissociation, Henry’s Law may appear to fail for organic acids at higher pHs. We propose a methodology to consistently capture the relation between phase behavior and ionic dissociation for organic acids, under all pH conditions. In addition to Phase Equilibria and Ionic dissociation in water, organic acids also tend to dimerize in the gas phase. We reviewed literature data on Vapor-Liquid equilibrium (Henry’s law coefficient KH), Liquid-liquid equilibrium (oil/water partitioning coefficient Ko/w), Ionic dissociation (dissociation constant Kd) and Dimerization (dimerization constant Km-d). Based on our review, we developed reasonable estimates of these constants for four organic acids (C1-C4) as a function of temperature. Pressure effects on these parameters are small (hence neglected) in a reasonable range of operating conditions (0 – 10 MPa).

Amrit Kalra, Shell Global Solutions (US) Inc.

Amrit Kalra is a Process Engineer in the Fluid Flow department of Shell Global Solutions (US) Inc. He received a PhD degree from Rensselaer Polytechnic Institute in 2003 and B. Tech degree from Indian Institutes of Technology Delhi in 1998, both in Chemical Engineering. He is currently responsible for conducting R&D activities and assist in troubleshooting upstream physical chemistry issues in scaling, souring, fouling etc. in upstream facilities

Raymond French, Shell Global Solutions (US) Inc.

Raymond French is team leader for the engineering data and physical properties team in the Fluid Flow Business Group of Shell Global Solutions (US) Inc. He has 26 years of experience in applied thermodynamics and phase equilibria, particularly for process simulation. He has a BS in chemistry from Rensselaer Polytechnic Institute and a PhD in physical chemistry from the Univ. of Miami, Coral Gables, FL.

Sheila Dubey, Shell Global Solutions (US) Inc.

Sheila Dubey is a senior staff research engineer in Shell Global Solutions (US) Inc. at the Westhollow Technology Center in Houston, with a PhD in Chemistry (University of Calgary) and MS in Chemical Engineering (University of Tulsa). She is currently the US team lead for SERF (Scale Emulsions Rheology Foam) in Flow Assurance. She brings varied experience to these areas of flow assurance because of her excellent background in physical organic chemistry, analytical chemistry, chemical engineering and strong practical laboratory skills in the areas of E&P, Chemicals and Refining for 28 years in Shell. She is a routine practitioner of OLI software for scale prediction in E&P applications.

Ashok Dewan, Shell Global Solutions (US) Inc.

Ashok Dewan is Team Leader for PETSIM (Process Engineering Tools, Simulators & Ionic Models) and Principal Engineer, in Shell Global Solutions (US) Inc.’s Upstream Fluid Flow Group. He is responsible for the rollout, license management, support, vendor liaison, & “in-house” training, for a portfolio of Process Engrg. Tools / Simulators, in the “americas”, for Shell companies. Ashok joined Shell in 1982 after completing his Doctor of Science (Chemical Engineering) from Washington University, St. Louis, Missouri. He obtained his Bachelor’s degree in Chemical Engineering from IIT-Bombay. He is very active in several joint-industry consortia such as DIPPR/AIChE, TRC/NIST and OLI’s ESP, CSP and AMINES focus groups. He currently serves as DIPPR Technical Director.

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