Process for the production of coarse K.sub.2 SO.sub.4 in crystallizers and classifiers

A continuous process for producing K.sub.2 SO.sub.4 which comprises:

• (a) introducing K.sub.2 SO.sub.4 or K.sub.2 SO.sub.4 precursor and a solvent therefor into a crystallizer having a slurry outlet means at the bottom portion thereof, an overflow means for supernatant liquid at the top portion thereof and circulating means therein;
• (b) supersaturating the resultant solution of K.sub.2 SO.sub.4 in said crystallizer, and crystallizing K.sub.2 SO.sub.4 out of the resultant supersaturated solution of K.sub.2 SO.sub.4 to form a slurry comprising coarse and fine crystalline K.sub.2 SO.sub.4 and supernatant, said slurry having a slurry density of over 40% and up to about 80% by weight;
• (c) withdrawing slurry from the bottom portion of said crystallizer and introducing said slurry into a separate elutriation classifier comprising an elongated tubular vessel;
• (d) withdrawing supernatant collecting at the overflow means of the crystallizer and introducing supernatant into the lower portion of said elongated tubular vessel;
• (e) maintaining a slurry density of from about 15% to about 25% by weight, and a flow rate sufficient to effect elutriative separation of particles of a size below 0.16 mm from coarser particles, within said elongated tubular vessel;
• (f) withdrawing the supernatant and fine crystalline K.sub.2 SO.sub.4 passing upwardly in the elongated tubular vessel, as overhead from the elongated tubular vessel and recycling same to the crystallizer;
• and,
• (g) withdrawing coarse crystalline K.sub.2 SO.sub.4 of a particle size above 0.16 mm at the lower portion of said elongated tubular vessel.