Method for recovery and reuse of ammonia in ammonia-base sulfite cooking liquors

A process for the recovery and reuse of ammonia in ammonia-base sulfite cooking liquors comprising the steps of:

• steam stripping spent ammonia-base sulfite cooking liquor to produce a vapor and a liquor residue;
• condensing the vapor formed during the steam stripping to form a dilute aqueous solution comprising ammonia or ammonium hydroxide in water;
• burning the liquor residue produced during steam stripping and non-condensed gases from the condensing step to produce an exhaust gas containing sulfur dioxide;
• passing the dilute aqueous solution produced during the condensing step through a cation exchange column charged with sulphurous acid to thereby form an ammonium sulfite containing solution;
• delivering the exhaust gases produced during the step of burning and the ammonium sulfite containing solution to a fortifying tower;
• and
• fortifying the ammonium sulfite containing solution with sulfur dioxide from the exhaust gases of the burning step to produce an ammonia-based sulfite cooking liquor concentrate.