Process for the purification of an aqueous stream coming from the fischer-tropsch reaction

A process for purifying an aqueous stream (i) coming from a Fischer-Tropsch reaction containing organic acid(s) comprising:

• adding at least one inorganic base to the aqueous stream (i),
• feeding the aqueous stream (i) after addition of the at least one inorganic base to an evaporator and obtaining a vapor stream (ii) and an aqueous stream (iii):
• wherein the vapor stream (ii) exits a head of the evaporator and comprises alcohols having from 1 to 20 carbon atoms and optionally other volatile compounds and is subsequently condensed thus forming an aqueous stream (iia);
• wherein the aqueous stream (iii) exits a bottom of the evaporator and comprises alcohols having from 1 to 20 carbon atoms, organic acids, and salts of organic acids that are formed upon the addition of the at least one inorganic base to the aqueous stream (i) and is subsequently fed to a distillation column;
• separating aqueous stream (iii) in the distillation column into an aqueous stream (iv) which emerges from a head of the distillation column and an aqueous stream (v) which emerges from a bottom of the distillation column:
• wherein the aqueous stream (iv) exiting from the head of the distillation column comprises alcohols having from 1 to 20 carbon atoms and comprises less than or equal to 2% by weight of organic acids having from 1 to 8 carbon atoms with respect to the total weight of the aqueous stream (iv), and optionally comprises other volatile compound(s), and
• wherein the aqueous stream (v) exiting from the bottom of the distillation column comprises a portion of the salts of organic acids present in said aqueous stream (iii);
• adding to the aqueous stream (iv) exiting from the head of the distillation column at least one organic base having a pKa, measured at 25° C. in water, greater than or equal to 7;
• and combining the aqueous stream (iv), after addition with the at least one organic base, with the aqueous stream (iia) to obtain an aqueous stream (vi);
• routing the aqueous stream (vi) and a process gas to a saturator and producing a gaseous stream (vii) from a head of the saturator;
• and feeding the gaseous stream (vii) from the saturator to a synthesis gas production plant;
• and, optionally, routing a drain stream (viii) from a bottom of the saturator into aqueous stream (i);
• and, optionally, routing the aqueous stream (v) exiting from the bottom of the distillation column to further treatment in order to obtain purified water.