PSI is developing a process to gasify wet biomass with water contents ≤ 80% under supercritical conditions, the so called hydrothermal gasification process. The biomass slurry was pressurized first, then heated up above the critical point, and afterwards gasified over a catalyst bed to the products methane and CO ₂. When water reaches the critical point, the fluid properties changed dramatically and it behaves like an apolar solvent and the solubility of inorganic salts decreased by several orders of magnitude. To prevent the blocking of the plant by precipitated salts, it is necessary to remove the salts continuously. A high degree of salt separation is important to keep the facility running and to protect the catalyst from poisoning. The influences of the variation of process parameters were investigated over a wide range. The interactions between different salts in a mixture were studied. Optimized conditions for the continuous salt separation were realized. This is an abstract of a paper presented at the 7th European Congress of Chemical Engineering-7 and 19th International Congress of Chemical and Process Engineering CHISA (Prague, Czech Republic 8/28/2010-9/1/2010).