Abstract: An improved process for treating spent alkylation acid to recover a sulfuric acid product suitable for use in wet process phosphoric plants particularly those which recover uranium as a byproduct. The process utilizes heat and agitation to polymerize the liquid, soluble organic impurities normally contained in spent alkylation acid to insoluble, carbonaceous solids. The carbonaceous solids formed are relatively inert in acidic environments, easy to handle and have valuable cation exchange and impurity scavenging properties.

Abstract: A process for recovering elemental sulfur from volcanic and non-volcanic ores is disclosed. Ore is processed by crushing the ore to a coarse particle size autoclaving to separate the sulfur from the ore, mild grinding to selectively reduce the size of the liberated sulfur particles, flotation and sulfur separation/filtration steps to produce a sulfur of at least 99% purity. The process recovers at least 90% of the elemental sulfur contained in the ore. The particular crushing of the ore and selective grinding techniques for reducing sulfur particles for reducing sulfur particles size are important factors in the efficiency of the process since the grinding techniques inhibit the formation of fine gangue which is difficult to separate from the liberated sulfur.

Abstract: A process for producing high grade silica and fluorine-containing coproducts from fluosilicic acid is described. To produce silica, the fluosilicic acid is reacted with aqueous ammonia to produce a solid silica product and a solution of ammonium fluoride. The solid silica is washed under controlled conditions and further processed to produce a high grade product. The ammonium fluoride solution is concentrated and sold as a concentrated ammonium fluoride solution product or reacted with metal hydoxides or oxides to produce metal fluorides.

Abstract: Wet process phosphoric acid, stabilized with respect to the precipitation of solids upon aging, and containing significantly reduced levels of magnesium and aluminum, is prepared by the controlled addition of fluosilicic acid to wet process filter grade phosphoric acid followed by a series of evaporation, crystallization and centrifugation steps. Sufficient fluosilicic acid is added to provide a fluorine to magnesium ratio of about 2.5:1 to 10.1:1, preferably 5:1. The final product, which has a P.sub.2 O.sub.5 content of at least 56 percent, contains low amounts of magnesium and aluminum, and exhibits low solids precipitation characteristics during shipment, storage and eventual processing into end products such a fertilizers.

Abstract: The present invention relates to the processing of phosphoric acid by crystallization starting with phosphoric acid and adding relatively large amounts of fine, relatively pure seed crystals to acid which has been cooled to supersaturated conditions. Crystallization thereafter proceeds under conditions which substantially favor growth on the seeds which are added and disfavor secondary nucleation. The present invention particularly describes a seed crystal generator for use in the foregoing process in which relatively high purity phosphoric acid, containing 60% to 66% P.sub.2 O.sub.5 is cooled to a temperature of at least 5.degree. to 10.degree. C. below zero and thereafter nucleated under agitation for less than ten minutes in a small crystallizing vessel.

Abstract: The present invention relates to the processing of phosphoric acid by crystallization. Wet-process phosphoric acid is purified by cooling it to supersaturated conditions and adding relatively large amounts of fine, relatively pure seed crystal. Crystallization thereafter proceeds under conditions which substantially favor crystal growth on the seeds which are added and disfavor secondary nucleation. To prevent the crystallizing magma from reaching a viscosity which would render further processing difficult, the present invention provides for recycling raffinate in an amount sufficient to maintain the solids content of the crystallizing magma below about 40%.

Abstract: The present invention discloses a new method for obtaining a crystallized phosphoric acid of relatively high purity starting with conventional phosphoric acid. The new method is based on crystallization of orthophosphoric acid hemihydrate from the phosphoric acid. Massive nucleation which would lead to the formation of unprocessable masses is avoided in the new method by providing unusually large amounts of fine relatively pure seed crystals of orthophosphoric acid hemihydrate and operating the crystallization process under conditions which favor crystal growth on the seed crystals and disfavor the occurrence of secondary nucleation. To prevent the crystallizing magma from reaching a viscosity which would render further processing difficult the present invention provides for recycling raffinate in an amount sufficient to maintain the solids content of the crystallizing magma below about 40%.

Abstract: Phosphate rock contained in an acidic slurry is ground by equipment wherein the acidic slurry contacts the metallic surfaces of the equipment. A method for monitoring and controlling grinding ball consumption is provided in which acid-neutralizing particulate iron contained in the acidic slurry is measured and correlated to control curves, which relate particulate iron concentration to slurry pH and slurry pH to the rate grinding ball consumption. If the measured particulate iron concentration equates to an unacceptable ball corrosion rate, the equilibrium of the slurry pH and particulate iron concentration can be varied to maintain a predictable ball consumption. When making the slurry, waste water from other steps of the wet process manufacture of phosphoric acid can be used as part of an acidic diluting medium.

Abstract: An improved method for producing wet process phosphoric acid with low post-precipitation characteristics from an unclarified dilute wet process phosphoric feed acid is described. The feed acid is processed through crystallization, centrifugation and concentration steps under controlled conditions to produce the desired products. The method also allows for the simultaneous production of merchant grade phosphoric acid and clarified merchant phosphoric acid.