High Temperature Aqueous Potassium and Sodium Phosphate Solutions: Two-Liquid-Phase Boundaries and Critical Phenomena, 275-400 deg C; Potential Applications for Steam Generators

摘要

Two-liquid-phase boundaries at temperatures between 275 and 400 deg C were determined for potassium phosphate and sodium phosphate aqueous solutions for compositions from 0 to 60 wt % dissolved salt. The stoichiometric mole ratios, K/PO sub 4 or Na/PO sub 4 , were varied from 1.00 to 2.12 and from 1.00 to 2.16 for the potassium and sodium systems, respectively. Liquid-vapor critical temperatures were also determined for most of the dilute liquid phases that formed. The minimum temperatures (below which a single solution existed) of two-liquid-phase formation were 360 sup 0 C for the potassium system and 279 sup 0 C for the sodium system at mole ratios of 2.00 and 2.16, respectively. For the sodium system at mole ratios greater than 2.16, solids crystallized at lower temperatures as expected from earlier studies. In contrast, potassium solutions that were explored at mole ratios from 2.12 to 3.16 and at temperatures below 360 sup 0 C did not produce solid phases nor liquid-liquid immiscibilities. Aside from the generally unusual observations of two immiscible liquids in an aqueous inorganic salt system, the results could possibly be applied to the use of phosphate additives in steam power generators. 16 refs. (ERA citation 11:025639)