Determination of the solubility, diffusion coefficient and hydrate stability of hydrogen sulfide in water and brine

The dissolution and diffusion process of hydrogen sulfide (H2S) in aqueous solutions are critical in the formation of many metal deposits and the stability of H2S hydrate also play an important role in natural gas exploitation and transportation due to the tendency of H2S to form hydrate at low temperature and high pressure, which can lead to pipeline blockage. In this study, the solubility and diffusion coefficient of H2S in water and brine as well as the stable conditions of H2S hydrates have been determined using fused silica capillary cell, high pressure optical cell, high pressure reactor, and Raman spectrometers.The details are as follows: (1) H2S solubility data in water were obtained at temperatures up to 573 K and pressures up to 100 MPa. These new data extend the predictable range of previous models. (2) The diffusion coefficients of H2S in water at 0.1–2 MPa and 273.1–373.1 K and in four brine solutions (0.62, 1, 2, and 3 mol•kg−1 NaCl) at 1 MPa and 273.1–373.1 K were determined. The results showed that the diffusion coefficient increased with the temperature and was inhibited by salinity. (3) The stability of H2S hydrate in water and brine including NaCl, KCl, MgCl2, NH4Cl, Na2SO4 and K2SO4 at the temperature range from 273.4 to 298.8 K, pressure ranging from 1.13 to 21.90 bar, and salinity from 3.4-20.0 wt.% were investigated. The results showed that the inhibitory effect of six electrolytes on H2S hydrate formation is in the order of MgCl2 > NH4Cl > NaCl > KCl > Na2SO4 = K2SO4.