TY  - JOUR
AU  - Talybov, Misirkhan
AU  - Azizova, Lala
AU  - Abdulagatov, Ilmutdin
PY  - 2019
DA  - 2019/12/24
TI  - Experimental Vapor-Pressures and Derived Thermodynamic Properties of Geothermal Fluids from Baden-Baden Geothermal Field (Southeastern Germany)
JO  - Journal of Energy and Power Technology
SP  - 006
VL  - 01
IS  - 04
AB  - Background: In the present study, vapor-pressures of three geothermal fluids from Baden-Baden geothermal field (Kirchenstollen, Friedrichstollen, and Murquelle, southeastern region of Germany) were measured over the temperature range of 274–413 K. The combined expanded uncertainty of the temperature and vapor-pressure measurements at 95% confidence level with a coverage factor of k = 2 were estimated to be 0.01 K and 1–3 Pa at low and 10–30 Pa at high temperatures, respectively. The measured values of vapor-pressure were used to calculate other crucial derived thermodynamic properties of these geothermal fluid samples, such as enthalpy and entropy of vaporization and the heat capacity.

Methods: The measurements were performed using two different methods and experimental apparatus: (1) absolute and differential static method which was used at low temperatures ranging from 274.15 to 323.15 K; and (2) absolute static method which was used at elevated temperatures ranging from 323.15 to 413.15 K.

Results: The data obtained from the measurements were utilized to formulate Antoine and Wagner-type vapor-pressure equations. The effects of various ion species on the vapor-pressure of the geothermal fluids were studied. In addition, the measured vapor-pressure values were utilized to develop Riedel’s type correlation model for natural geothermal fluids in order to estimate the contributions of the various ion species to the total experimentally-observed values of vapor-pressure. It was observed that the anions were increasing the vapor-pressure, while the cations were decreasing it, with the rates (magnitudes) of these increases and decreases being different and strongly dependent on the chemical nature of the ion species involved. Using the measured vapor-pressure data, the other key thermodynamic properties, such as enthalpy and entropy of vaporization and the heat capacity) of the geothermal fluid samples were calculated.

Conclusions: The measured vapor-pressure values of the geothermal fluids were higher than the pure water values (IAPWS standard data) by 5.5%–25.4% for Kirchenstollen, 3.0%–11.4% for Friedrichstollen, and 5.3%–14.8% for Murquelle, depending on the temperature. The largest deviations (up to 11%–25%) were observed at low temperatures (approximately 277 K), while at high temperatures, the deviations were within the range of 3.0% to 5.5%. This could be attributed to the effects of soluble gas in the geothermal fluids. The soluble gases were observed to be strongly affecting the measured vapor-pressure of the geothermal fluids. The experimentally observed vapor-pressure was the result of the competition between the opposite effects of the anion and cation contributions.
SN  - 2690-1692
UR  - https://doi.org/10.21926/jept.1904006
DO  - 10.21926/jept.1904006
ID  - Talybov2019
ER  -