Method of recovering pulping chemicals from dissolved ash having a high carbonate content

A method of recovering wood pulping chemicals from black liquor produced in a wood pulping process and a pulp mill comprising:

• burning the black liquor in a recovery boiler and forming ash containing carbonate, sodium, potassium and chloride;
• dissolving at least a portion of the ash to form a dissolved ash solution;
• directing the dissolved ash solution to one or more evaporators and evaporating the dissolved ash solution to form a concentrated dissolved ash solution and precipitating sodium sulfate and sodium carbonate from the dissolved ash solution;
• separating the precipitated sodium sulfate and sodium carbonate from the concentrated dissolved ash solution;
• directing the concentrated dissolved ash solution to a crystallizer and adiabatically cooling the concentrated dissolved ash solution to produce a glaserite slurry and a purge stream containing chloride;
• reducing the tendency of sodium carbonate to crystallize in the crystallizer and encouraging pure glaserite to crystalize in the crystallizer by adding a sulfate source to the concentrated dissolved ash solution prior to the concentrated dissolved ash solution reaching the crystallizer;
• directing the glaserite slurry to a solids-liquid separator and separating glaserite crystals from the glaserite slurry;
• wherein the solids-liquid separator produces a liquid recycle stream and wherein the liquid recycle stream is recycled to the crystallizer that produces the glaserite slurry;
• separating sodium sulfate from the glaserite crystals by leaching the sodium sulfate from the glaserite crystals;
• and
• recycling a portion of the purge stream containing the chloride to the one or more evaporators that concentrates the dissolved ash solution.