Abstract: A wet phosphoric acid production process comprising the attack on phosphate rock by sulfuric acid and phosphoric acid utilizing a vacuum cooling and a recirculation of the reaction slurry. The flow rates of the materials within the system are maintained at a level, relative to the rate of withdrawal of the slurry from the system, of between 300% and 4000% for the cyclic flow, between 2000% and 4000% for the vacuum cooling flow and between 500% and 2200% for the local agitation flow. Control of the flow rates according to factors including the rock analysis allows maximization of the yield of H.sub.3 PO.sub.4.

Abstract: A multi-compartment reaction system for the manufacture of phosphoric acid by the wet process having a recirculation slurry flash cooler. The removal of heat from the reaction system is accomplished by circulating reaction zone slurry through an elevated vacuum flash cooler under the combined effect of differential liquid levels maintained in the system, and the vacuum in the flash cooler. The amount of reaction zone slurry passed to the flash cooler is sufficiently large so that the temperature differential experienced by the slurry is low and crystallization of calcium sulfate from the slurry liquid occurs in a favorable manner. There is also a substantial reduction in the pumping requirements compared with conventional operations in which the slurry is pumped to an elevated flash cooler, even though the large amount of slurry is passed to the flash cooler in accordance with the invention.

Abstract: Wet process phosphoric acid is made by grinding phosphate rock as a slurry in water, and digesting the ground rock slurry with sulfuric acid which has been diluted by spent calcium sulfate wash water before being combined with the ground slurry.