In several countries, geothermal resources have great potential for an economic production of energy. Mineral salts and/or desalted water can be valuable by-products in several cases.
The knowledge of the thermodynamic behaviour of geothermal fluids, characterised by the presence in solution of salts and gases at high pressure and temperature, can be useful for optimal design , control and optimal ranning of large scale industrial plants.
However, because of substantial deviations from ideal behaviour of these two phase multicomponent mixtures, particular problems are encountered in modelling their thermodynamic properties with the required degree of accuracy and generality. Furthermore, since hot geothermal fluids are available at high pressure, we have to account for the influence of the pressure on both the liquid and the vapour phase.
We have developed a general analytical procedure based on the SRK equation of state by which it is possible to correlate and predict the thermodynamic behaviour of any kind of natural geothermal fluids under high pressure. Available experimental information for the pure components of natural geothermal fluids as well as for the sub-binaries are used for the parametrization of the model.
The comparison between experimental and calculated results for the system water-carbon dioxide-sodium chloride shows that the model has satisfactory correlation and predictive capabilities.