Key words: SCWO (supercritical water oxidation), hydrothermal solutions, salt plugs, salts of type 1 and type 2, suppression of salt precipitation
A flow hydrothermal setup with a tubular reactor, HPLC pump and back-pressure regulators was used to study salt precipitation phenomena in the ternary systems K2SO4—KCl — H2O, K2SO4—K2CO3—H2O and Na2SO4—NaCl—H20 for flow rates 2.5 and 5.0 ml/min in temperatures and pressures ranges 400 — 600 °C and 270—340 kg/cm2. The main purpose of this work was to elucidate the conditions of plugging a flow in aqueous solutions containing salt of type 2 (K2SO4 or Na2SO4) and a possibility to suppress it by using the hydrothermal solvents represented by high-temperature aqueous solutions of type 1 salt (such as KCl,K2CO3 and NaCl). As a result of experimental studies the concentrations of hydrothermal solvent were determined when a plugging of aqueous solutions containing 0.26 — 0.27 % mol. of K2SO4 or Na2SO4 was suppressed. The effects of flow rate and chemical composition of type 1 salts was studied. The obtained experimental data show that salt precipitation, which plugs the flow of solution and hampers a practical application of supercritical water oxidation (SCWO) technology for some water-salt systems, can be prevented by adding type 1 electrolytes into the initial aqueous solutions of type 2 salts.
doi:10.1134/S1990793111070062