Kraft smelt solidification in a fluidized bed reactor

A continuous process for treatment of molten kraft smelt in a kraft recovery process, said process comprising

• (1) continuous feeding molten kraft smelt from a black liquor recovery system to a fluidized bed reactor containing particulate solids fluidized with a non-oxidizing fluidizing gas, wherein the fluidized bed reactor is operated at a temperature of about 600.degree. to 900.degree. F.;
• (2) solidifying the molten kraft smelt within the fluidized bed reactor to form solid kraft smelt particles;
• (3) removing the solid kraft smelt particles from the lower portion of the fluidized bed reactor;
• and
• (4) feeding the solid kraft smelt particles removed from the fluidized bed reactor to a dissolving tank containing an aqueous solution whereby a kraft green liquor is formed, wherein the solid smelt particles are introduced sufficiently below the surface of the aqueous solution so that essentially all gaseous sulfur-containing compounds liberated upon introduction of the solid smelt particles are absorbed in the aqueous solution;
• wherein the relative rates of molten kraft smelt fed into the fluidized reactor and solid kraft smelt particles removed from the fluidized bed reactor are adjusted to achieve an essentially steady state operation.

An integrated process for the recovery of pulping chemicals from black liquor from a kraft pulping mill, said process comprising

• (1) burning black liquor from a kraft pulping mill in a boiler to produce high pressure steam;
• (2) collecting molten kraft smelt from the bottom of the boiler;
• (3) feeding the molten kraft smelt into a fluidized bed reactor containing a particulate substrate fluidized with a non-oxidizing fluidizing gas and operated at a temperature at least 100.degree. F. below the melting point of the molten kraft smelt, whereby the molten kraft smelt cools and solidifies upon contact with the fluidized particulate substrate to form solid kraft smelt particles;
• (4) removing the solid kraft smelt particles from the fluidized bed reactor;
• (5) feeding the solid kraft smelt particles to a dissolving tank containing an aqueous solution at about 180.degree. to 205.degree. F. to form a kraft green liquor, wherein the solid kraft smelt particles are fed at a sufficient depth below the surface of the aqueous solution so that steam and volatile sulfur-containing compounds are recondensed and reabsorbed in the aqueous solution;
• (6) clarifying the kraft green liquor by removing dregs;
• and
• (7) treating the clarified kraft green liquor with lime to form a kraft white liquor containing the pulping chemicals.