1976 Volume 30 Issue 3 Pages 142-153
Oka, one of the above-mentioned authors reported in his previous paper on the graphical calculations for isothermal evaporation of four kinds of ionic brines by using Jdnecke type triangular coordinated diagrams of 5-component system Na+, K+, Mg2+, Ca2+ Cl--H2O saturated with NaCl at 110°C, 70°C, 45°C. As the most practical result, it was found that the best NaCl yield of ionic brine could be obtained by doing the evaporation just upto the saturation point of KCl. The hot mother liquor separated from such concentrated slurry was saturated at the same time with NaCl and KCl. When it was cooled, therefore, salt crystals must have been depositted.
In the present paper, the authors again made graphical calculations as to how much water be evaporated by evaporation at 110°C under the best conditions, how much NaCl be obtained, and what kinds of salts come out by cooling the separated hot mother liquors to 25°C and how much of them be obtained. The phase diagrams of D'Ans type of 5-component system saturated with NaCl were used for these calculations, because the concentrations of the components could be read directly.
Only a part of the diagrams for the 5-component system which was requisite for the calculations was drawn on the common axes; namely, lines for the bivariant systems, NaCl-KCl-Carnallite-H2O (SX), NaCl-Carnallite-Bischofite-H2O (RY), and a monovariant system NaCl-KCl-H2O (E) as shown in Tables 1 and 2, and Fig.-1.
By evaporation of ionic brine at 110°C, the mother liquor saturated with KCl must be on the triangle E1S1X1. By cooling the mother liquor, the kind of salts to deposit can be determined by the position of point on the part of 25°Cdiagram. Such computations were done in Fig.-1, and the triangle E1S1X1 was devided into three fields; namely, II, V and III, by two straight lines gh and ij. The mother liquor in field II deposited NaCl and KCl by being cooled to 25°C, and it lay on the triangle E2S2X2. The hot mother liquor in field V deposited NaCl, and carnallite simultaneously by being cooled to 25°C, and the cold mother liquor lay on the line S2X2. And, the hot mother liquor in field III deposited NaCl and carnallite simultaneously, and the cold mother liquor lay on the quadrangle S2X2Y2R2.
When four ionic brines A, B, D and E (Table-5) were evaporated at 110°C to the saturation point of KCl, the mother liquors for A and B lay in field II, and those for D and E lay in field V. The graphical calculation for mother liquor A was shown in Fig.-2, and for D in Fig.-3.
For such calculations, the final concentrations of KCl, MgCl2 and CaCl2 could be read directly from the diagrams. But the concentration, of NaCl could not be read directly, and so it was interpolated with Fig.-4 on the assumption that the concentration of NaCl on a straight line changed linearly.
The results of these calculations were verified: The results of evaporations were compared with those in the previous paper, and the crystal depositions by cooling were verified with semi-quantitative experiments. The authors believe from these verifications that the method of calculations is a reliable one.
