je9b00513_si_001.pdf (411.84 kB)
Solubility of Water in Hydrogen at High Pressures: A Molecular Simulation Study
journal contribution
posted on 2019-08-23, 21:29 authored by Ahmadreza Rahbari, Jeroen Brenkman, Remco Hens, Mahinder Ramdin, Leo J. P. van den Broeke, Rogier Schoon, Ruud Henkes, Othonas A. Moultos, Thijs J. H. VlugtHydrogen
is one of the most popular alternatives for energy storage.
Because of its low volumetric energy density, hydrogen should be compressed
for practical storage and transportation purposes. Recently, electrochemical
hydrogen compressors (EHCs) have been developed that are capable of
compressing hydrogen up to P = 1000 bar, and have
the potential of reducing compression costs to 3 kWh/kg. As EHC compressed
hydrogen is saturated with water, the maximum water content in gaseous
hydrogen should meet the fuel requirements issued by the International
Organization for Standardization (ISO) when refuelling fuel cell electric
vehicles. The ISO 14687–2:2012 standard has limited the water
concentration in hydrogen gas to 5 μmol water per mol hydrogen
fuel mixture. Knowledge on the vapor liquid equilibrium of H2O–H2 mixtures is crucial for designing a method
to remove H2O from compressed H2. To the best
of our knowledge, the only experimental high pressure data (P > 300 bar) for the H2O–H2 phase coexistence is from 1927 [J. Am. Chem. Soc., 1927, 49, 65–78]. In this
paper, we have used molecular simulation and thermodynamic modeling
to study the phase coexistence of the H2O–H2 system for temperatures between T = 283
K and T = 423 K and pressures between P = 10 bar and P = 1000 bar. It is shown that the
Peng-Robinson equation of state and the Soave Redlich-Kwong equation
of state with van der Waals mixing rules fail to accurately predict
the equilibrium coexistence compositions of the liquid and gas phase,
with or without fitted binary interaction parameters. We have shown
that the solubility of water in compressed hydrogen is adequately
predicted using force-field-based molecular simulations. The modeling
of phase coexistence of H2O–H2 mixtures
will be improved by using polarizable models for water. In the Supporting
Information, we present a detailed overview of available experimental
vapor–liquid equilibrium and solubility data for the H2O–H2 system at high pressures.
