2017, №1

сс. 69-79

Solubility and Critical Phenomena in Ternary Aqueous Solutions, Containing the Salt of the Type 2 and Alkali

2017, №1

сс. 69-79

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M.A. Urusova, V.M. Valyashko

Key words: ternary water-salts systems, supercritical phase equilibria, phase diagrams

Supercritical phase equilibria in ternary system K2SO4—KOH—H2O at 420—500 °C
and up to 130 MPa pressure with binary boundary subsystems of different types are
studied. The binary subsystem of type 1 do not have any critical phenomena in saturated
(l = g — s) aqueous solution as well as the immiscibility equilibrium (l1—l2) (КОН—Н2O),
the second binary subsystem of type 2 (K2SO4—H2O) has two critical end-points
p (g = l — sK2SO4) and Q (l1 = l2—sK2SO4)
with saturated aqueous solution and the liquid-liquid
immiscibility equilibria. The ternary system has two three-phase equilibria
(g — l — sK2SO4) and (l1 — l2 — sNa2SO4),
separated by a two-phase supercritical fluid region
(fl—sK2SO4) and two types of monovariant critical curves
(g = l — sK2SO4) and (l1 = l2 — sK2SO4).
The three?phase regions approach each other at temperature increased up to the
point where the two-phase supercritical equilibrium disappeares, and the two mentioned
monovariant critical curves are joined into a double homogeneous critical point
(g = l — s ↔ l1 = l2 — s)
at maximum temperature ∼ 445 °C and 51—52 MPa.

doi:10.1134/S1990793117080139