Phase equilibria and heterogenization of supercritical fluids in the K2SO4-K2CO3-H2O system

This experimental study of phase equilibria in the K 2 SO 4 -K 2 CO 3 -H 2 O system at 385–500°C and pressures up to 100 MPa is directed to determine the sequence of phase transformations that generate heterogeneous supercritical fluids from the homogeneous one; the homogeneous supercritical region spreads into the ternary system from the K 2 SO 4 -H 2 O subsystem. We found that heterogenization of supercritical fluid upon addition of K 2 CO 3 starts with l 1 =l 2 critical phenomena in solid saturated solutions and is attended by amalgamation of the stable immiscibility region that spreads from the K 2 CO 3 -H 2 O system with the metastable immiscibility region that originates from the K 2 SO 4 -H 2 O system. Our experimental results and the topological analysis of phase equilibria at temperatures above the critical point of water gave us the full scenario of the phase behavior of the title ternary system in the regions of fluid equilibria, g=l and l 1 =l 2 critical phenomena, and liquid-liquid phase separation in two-, three-, and four-phase equilibria.