Precipitation of sodium sulfate and sodium carbonate during supercritical water oxidation/gasification of ethanol

Reactor plugging induced by salt precipitation in supercritical water (SCW) is a major problem during the hydrothermal treatment of hypersaline waste. Considering that current investigations have focused strictly on pure water systems, a continuous tube reactor was designed herein to study the precipitation of Na2SO4 and Na2CO3 in a complex SCW environment, which was generated using C2H5OH and H2O2 in order to reproduce real SCW conditions. Results indicate that salt precipitation was accelerated in the presence of C2H5OH and H2O2. The passage rate was only 87% for Na2SO4 and 43% for Na2CO3 in an aqueous solution of 0.1 wt% C2H5OH and 0.5 times of H2O2, compared to the solubility of these salts in pure water at 385 °C and 25 MPa. Organics and gases reduce the fluid density and further aggravate salt precipitation. Salt precipitation occurred mainly in the area around gas inlet and mixer in a real SCW process.