Hydrogen solubility

[Seymensch]

Hi

I am working on the solubility of hydrogen in brine with some minerals and it is certain that hydrogen solubility in brines with minerals is expected to increase with increasing pressures

But that is not the case when i performed the simulations with the software?

What could be the issue?


This is at 500 atm

Code: [Select]

REACTION_TEMPERATURE 1
    90  95  100  105  110  115  120
REACTION_PRESSURE 1
   500
GAS_PHASE 1
    -fixed_pressure
    -pressure 500
    -volume 1
    -temperature 90
    H2(g)     0
EQUILIBRIUM_PHASES 1
    CH4(g)    0 10
    Calcite   0 0.1
    Illite    0 0.4
    K-feldspar 0 0.4
    K-mica    0 0.4
    Kaolinite 0 0.5
    Quartz    0 8.1
    Siderite  0 0.1
    H2(g)     0 100
SOLUTION 1
    temp      110
    pH        8
    pe        4
    redox     pe
    units     ppm
    density   1
    Alkalinity 280.94 as HCO3
    Ca        115.37
    Cl        1383.81
    K         8.32
    Mg        23.32
    Na        686.27
    S(6)      95.94
    -water    1 # kg
END

This is at 294 atm

Code: [Select]

REACTION_TEMPERATURE 1
    90  95  100  105  110  115  120
REACTION_PRESSURE 1
   294
GAS_PHASE 1
    -fixed_pressure
    -pressure 294
    -volume 1
    -temperature 90
    H2(g)     0
EQUILIBRIUM_PHASES 1
    CH4(g)    0 10
    Calcite   0 0.1
    Illite    0 0.4
    K-feldspar 0 0.4
    K-mica    0 0.4
    Kaolinite 0 0.5
    Quartz    0 8.1
    Siderite  0 0.1
    H2(g)     0 100
SOLUTION 1
    temp      110
    pH        8
    pe        4
    redox     pe
    units     ppm
    density   1
    Alkalinity 280.94 as HCO3
    Ca        115.37
    Cl        1383.81
    K         8.32
    Mg        23.32
    Na        686.27
    S(6)      95.94
    -water    1 # kg
END

What is the reason for this occurrence and where am i getting it wrong please? Moles lost @ 294 atm is supposed to be less than Moles lost @ 500 atm which is not the case here.

[dlparkhurst]

Nope, solubility of H2 decreases with pressure for a constant partial pressure of H2(g).

Note, you won't have a fixed pressure gas phase unless the sum of the partial pressures of the gas components exceeds the system pressure. By fixing partial pressure of H2(g) at 1 atm, you will not have a gas phase, so you can eliminate that from your calculation.

Code: [Select]

SOLUTION 1
    temp      90
REACTION_PRESSURE 1
   0 500 in 51 steps
EQUILIBRIUM_PHASES 1
    H2(g)     0 100
USER_GRAPH 1
    -axis_titles            "Pressure, atm" "Molality of H2(aq)" ""
    -chart_title            "90 C"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 GRAPH_X PRESSURE
20 GRAPH_Y MOL("H2")
  -end
    -active                 true
END