Advanced brine chemistry program. DOE Quarterly report, January 1, 1998--March 31, 1998
I. DISK CRASH: Due to space limitations, the Chemistry Department Computer Center put some of our software routines on an old disk. This disk subsequently crashed. Since the Center had failed to back-up this space, the routines were lost. The Center acknowledges their error and has agreed to reimburse-the grant for the lost time. We are now negotiating the amount of time the lost routines represent. Fortunately, data files, input and output files, models and reports were not affected by this
... t. The present assessment is that several fitting codes for creating TEQUIL models and GEOF'LUIDS models were lost. TEQUIL MODELS, T c 350°C: The previous modifications to the fitting and equilibrium codes required to add many new species to the TEQUIL models were lost in the disk crash. These changes were necessary to add the aluminum species to the calcite model. Some of the lost upgrades have now been regenerated but we still need to reconstruct several important routines. We hope that most of this work will be completed by the end of May. We note that the recent work (see below) on developing 3-D capability for displaying phase diagrams generated by our TEQUIL models was not lost. MODELS at HIGH TEMPERATURE and PRESSURE: A. Molecular Dynamics Simulations In our studies of fluids using the molecular dynamics approach, we first simulated non-polar or weakly polar fluids, such as CH" CO" N" O" and their mixtures. The results of these simulations were very promising and led to much improved models of high T,P behavior in these systems. Then, we proceeded to model more complicated systems: H,O and aqueous electrolyte solutions, such as NaC1-H,O, KC1-H,O and CaC1,-H,O. For pure water, PVT predictions at high temperature were very close to experimental results. Simulations of the NaCl-H,O and KCl-H,O systems gave good results (similar to experimental accuracy) for the vaporization enthalpies, diffusion coefficients and Raman spectra as well as for Na-Cl and K-Cl associations. The simulated PVT properties of CaClz had about 3% error which is a little larger than experiment. These results have been reported previously. Recently, we began attempts to simulate the vapor-liquid surface for water. The results are not in good agreement with experiment. For example, at 600 OK, the simulated saturation pressure is only about 21 bars and the experimental is 121 bars. This discrepancy is not completely unexpected since similar results have been reported for other water-water potentials. Since our water-water potential performed better than others in predicting PVT properties, we had hoped it would also produce accurate vapor-liquid results. However, in spite of these initial disappointing findings, these calculations need to be completed. Presently, there are only two other calculations of water vapor-liquid coexistence. Therefore, continued systematic c -4 - VI. OTHER ACTIVITIES (papers, reports, meetings): A chapter on our TEQUIL modeling technology for geothermal systems has been completed and accepted for publication in Transport in Porous Media.