Hydrate Dissociation Condition Measurement of CO 2 ‑Rich Mixed Gas in the Presence of Methanol/Ethylene Glycol and Mixed Methanol/Ethylene Glycol + Electrolyte Aqueous Solution Qazi Nasir, † K. K. Lau,* ,† Bhajan Lal, † and Khalik M. Sabil ‡ † Department of Chemical Engineering, Universiti Teknologi PETRONAS Bandar Seri Iskandar, 31750, Perak Malaysia ‡ Institute of Petroleum Engineering, Heriot-Watt University Malaysia, No 1 Jalan Venna P5/2, Precinct 5, 62200 Putrajaya, 7 Federal Territory of Putrajaya, Malaysia ABSTRACT: In this work, the hydrate dissociation condition for carbon dioxide rich gas mixture in the presence of methanol, methanol + sodium chloride or calcium chloride, and ethylene glycol, ethylene glycol + sodium chloride or calcium chloride aqueous solution, were measured and reported. The measurements are carried out at temperature and pressure range of (263.85 to 284.75) K and (2.76 to 12.08) MPa. All data were measured using the isochoric pressure search method. In order to exhibit the inhibition effect of above-mentioned aqueous solution, a comparison was made between experimental data of carbon dioxide rich gas mixture in the presence of pure water and aqueous solutions consist of inhibitor and electrolytes. Furthermore, a thermodynamic model was used to correlate the experimental values. 1. INTRODUCTION Natural gas serves as an important and growing part of global energy stream. However, for the past half of century, the growth in global demand of natural gas along with its limited resource has gained market share. The rapid build-up in natural gas prices and perception of long-term shortage creates incen- tives for the development of infrastructure to produce natural gas from carbon dioxide (CO 2 ) rich gas reservoir. These types of reservoirs are located across the globe. 1-6 The gas produced from such reservoir are economically unviable and not suitable to use as a feedstock for LNG plant and hence need to be treated in inside multistage separation processes which runs at low temperature and high pressure. One of the main concerns for the natural gas production from CO 2 -rich gas is its increasing susceptibility to form gas hydrate. Gas hydrate is a major flow assurance problem in gas production, especially for deep water gas reservoirs where hydrate formation cause pipe blockage and rise safety con- cerns. 1-3 Since CO 2 is more favorable to form gas hydrate as compared to methane, so it is quite imperative that gas mixture with rich CO 2 contents are more prone to form gas hydrate. One of the common preventive measures to avoid gas hydrate formation is to ensure the working condition either in the pipe- line or top facility is set above the hydrate formation condition. This is usually done by insulating the pipeline or active heating. Other methods include the dehydration of the natural gas and more commonly used option is the injection of thermodynamic inhibitors. The water-soluble solvents reduce the activity of water effectively shifts the hydrate equilibrium condition to high pressure and low temperature. Produce gas contains a significant amount of formation water mixed with various type of salt of different quantities, which reduces the ability of gas hydrate formation. Cases where saline water inhibition is insufficient, aqueous solution consists of methanol, and ethylene glycol are injected into the pipeline create a system contains both inhibitors and salts. 7 In this regard, accurate knowledge for gas hydrate dissociation condi- tion in the presence of salt and methanol/ethylene glycol is vital to avoid formation of gas hydrate. This could benefit safe and economical plant design, production, processing facilities, and pipeline operations. The study is the extension of our previous work 8 and is carried out further to consider the potential importance and limited availability of experimental data for carbon dioxide (CO 2 ) rich gas system in the presence of aqueous solution of methanol/ ethylene glycol and salt. Numerous experimental data of hydrate dissociation condition are reported, 7,9-17 previously for single methane (CH 4 ) and carbon dioxide (CO 2 ) in the presence of alcohol or salt aqueous solution; however ,experimental data for the mixed system containing both alcohol and electrolyte in aqueous solution are limited. 12-15,18-21 Also limited reported data of hydrate dissociation condition are available for binary (CH 4 -CO 2 ) and natural gas system in the presence of aqueous solution of alcohol and electrolyte. 22 To the best of our knowledge, no such work has been reported for CO 2 -rich gas mixture in the presence of aqueous solution salt and organic inhibitors. Received: September 9, 2014 Accepted: October 9, 2014 Published: October 22, 2014 Article pubs.acs.org/jced © 2014 American Chemical Society 3920 dx.doi.org/10.1021/je5008313 | J. Chem. Eng. Data 2014, 59, 3920-3926