Preparation of granular sodium tripolyphosphate products from screen undersize sodium tripolyphosphate particles

A continuous process for producing a granular sodium tripolyphosphate product having low friability, high absorptivity and a bulk density within the range of from about 0.65 g/cc to about 0.87 g/cc, which comprises continuously compacting screen undersize sodium tripolyphosphate particles, continuously milling the compacted particles, continuously recovering a compacted and milled feed having a particle size distribution of at least 15% by weight +50 mesh, 0 to 50% by weight -50 +100 mesh and 0 to 50% by weight -100 mesh, continuously moisturizing the compacted and milled feed by adding a sufficient amount of water thereon to continuously produce a moisturized material containing between 15 and 35% by weight moisture, continuously agitating the material being moisturized, continuously calcining the moisturized material to a temperature within the range of from about 300.degree. to about 600.degree. C. and continuously recovering said granular sodium tripolyphosphate product.

A continuous process for producing a granular sodium tripolyphosphate product having low friability, high absorptivity, and a bulk density within the range of from about 0.65 g/cc to about 0.87 g/cc, which comprises continuously compacting screen undersize sodium tripolyphosphate particles, continuously milling the compacted particles, continuously recovering a compacted and milled feed having a particle size distribution of at least 15% by weight +50 mesh, 0 to 50% by weight -50 +100 mesh and 0 to 50% by weight -100 mesh, continuously moisturizing the compacted and milled feed and recycled process undersize material by adding a sufficient amount of water thereon to continuously produce a moisturized material containing between 15 and 35% by weight moisture, continuously agitating the material being moisturized, continuously calcining the moisturized material to a temperature within the range of from about 300.degree. C. to about 600.degree. C., continuously recovering said granular sodium tripolyphosphate product, and continuously recycling process undersize material to the moisturization step.

A process for producing a granular sodium tripolyphosphate product having low friability, high absorptivity, and a bulk density within the range of from about 0.65 g/cc to about 0.87 g/cc, which comprises compacting screen undersize sodium tripolyphosphate particles, milling the compacted particles, recovering a compacted and milled feed having a particle size distribution of at least 15% by weight +50 mesh, 0 to 50% by weight -50 +100 mesh and 0 to 50% by weight -100 mesh, moisturizing the compacted and milled feed by adding a sufficient amount of water thereon to produce an agglomerated material containing on the average between 15 and 35% by weight moisture, agitating the material being moisturized by rotation, calcining the agglomerated material to a temperature within the range of from about 300.degree. to about 600.degree. C. and recovering said granular sodium tripolyphosphate product.