Technical paper
Proper Interpretation Of Freezing And Hydrate Prediction Results From Process Simulation
Michael W. Hlavinka, Ph.D., P.E. Vicente N. Hernandez, Ph.D. Bryan Research & Engineering, LLC Bryan, TX , U.S.A. Dan McCartney Black & Veatch Energy Overland Park, Kansas, U.S.A. This paper focuses on the modeling of solid phase behavior in systems that are frequently encountered in natural gas processing. The ability to perform accurate calculation of freezing or solids formation conditions in processes from dry ice, hydrates, and water ice is quite important. Although the primary focus in this work is on dry ice formation from carbon dioxide, analogies with hydrate formation are presented. A description of the phase equilibria at different conditions of temperature and pressure is included. The paper compares the predicted results from simulation with selected experimental data sets, and illustrates that accurate results are obtained over a wide variety of conditions. However, due to the complicated phase behavior of these systems, improper interpretation of results, or incorrect use of the tools within the simulator is possible due to the multiplicity of incipient formation points. One fact that is not well known is that lowering the temperature may cause a solid that has formed to melt under certain conditions of pressure and composition. While recent work has been done to mitigate the incorrect application of these tools, knowledge of some of the different types of phase behavior is generally desirable to understand and exploit the results. Phase diagrams are presented to aid in understanding the solid formation behavior.
Michael W. Hlavinka, Ph.D., P.E. Vicente N. Hernandez, Ph.D. Bryan Research & Engineering, LLC Bryan, TX , U.S.A. Dan McCartney Black & Veatch Energy Overland Park, Kansas, U.S.A. This paper focuses on the modeling of solid phase behavior in systems that are frequently encountered in natural gas processing. The ability to perform accurate calculation of freezing or solids formation conditions in processes from dry ice, hydrates, and water ice is quite important. Although the primary focus in this work is on dry ice formation from carbon dioxide, analogies with hydrate formation are presented. A description of the phase equilibria at different conditions of temperature and pressure is included. The paper compares the predicted results from simulation with selected experimental data sets, and illustrates that accurate results are obtained over a wide variety of conditions. However, due to the complicated phase behavior of these systems, improper interpretation of results, or incorrect use of the tools within the simulator is possible due to the multiplicity of incipient formation points. One fact that is not well known is that lowering the temperature may cause a solid that has formed to melt under certain conditions of pressure and composition. While recent work has been done to mitigate the incorrect application of these tools, knowledge of some of the different types of phase behavior is generally desirable to understand and exploit the results. Phase diagrams are presented to aid in understanding the solid formation behavior.