HIGH-PRESSURE PHASE-BEHAVIOR OF (XCHF(3)-X)H2O) AND (X(1)CHF(3)+X(2)NACL+(1-X(1)-X(2))H2O)((1)

Experimental results of the high-pressure phase behaviour for {xCHF(3) + (1 - x)H2O) and {x(1)CHF(3) + x(2)NaCl + (1 - x(1) - x(2))H2O} are presented. (Gas + gas) equilibria for five compositions with x(CHF3) ( 0.0334 +/- 0.0002)< x < (0.1389 +/- 0.0002) as well as for six composi tions with x(1)(CHF3) (0.0305 +/- 0.0002) < x(1) < (0.1096 +/- 0.0002) , and mole fractions x(2)(NaCl) (0.0046 +/- 0.0002) < x(2) < (0.0100 /- 0.0002) were measured in a high-pressure autoclave equipped with sa pphire windows and magnetic stirring. The phase transitions were deter mined visually. The pressure ranged from 20 MPa to 200 MPa, and the te mperature from T = 470 K to T = 625 K. The (xCHF(3) + (1 - x)H2O} exhi bits a type-III fluid phase behaviour without (gas + gas) immiscibilit y of the first kind. Isopleths for NaCl mass fractions omega = (0.0167 7 and 0.03336) relative to H2O are shifted towards higher temperatures compared with the binary mixture {xCHF(3) + (1 - x)H2O). In this syst em the temperature shift is more pronounced than for isopleths in the system (xCF(4) + (1 - x)H2O} upon NaCl addition. The objective of this study was to investigate the phase behaviour of model-systems encount ered in supercritical water oxidation processes. (C) 1997 Academic Pre ss Limited.