Abstract: High quality phosphoric acid is produced from phosphate rock and high alumina pebble which is a byproduct of phosphate rock mining operations. The rock or pebble with or without comminution is digested in phosphoric and sulfuric acid and the resultant phosphoric acid contains the metallic ions normally present in the treated rock and pebble. The metallic ions are then extracted from the acid by ion exchange with a water-immiscible organic sulphonic acid compound (preferably in the presence of an organophosphate or phosphonate). After phase separation the organic phase containing the extracted metallic ions can be regenerated. The process is especially useful when the digestion is done at a P.sub.2 O.sub.5 concentration and temperature which produces calcium sulfate hemihydrate.

Abstract: Phosphoric acid is prepared from phosphate rock and sulfuric acid by using a reaction train comprising a dissolving slurry and a crystallization slurry maintained at different sulfate levels. Both inter and intra vessel circulation are used at high rates to minimize reagent concentration gradients and temperature gradients and provide a suitable crystallization environment. Preferably, the intra vessel circulation is substantially in plug flow, as through a draft tube.

Abstract: The invention comprises a multi-vessel reaction apparatus useful for reacting phosphate rock and sulfuric acid in which the reaction slurry undergoes intra- and inter- vessel circulation (preferably through a draft tube). The solution portion of the slurry in a first vessel or set of vessels (the "dissolver") is preferably maintained at at lower sulfate ion concentration and the solution portion of the slurry in the second vessel or system of vessels (the "crystallizer") is preferably maintained at a positive sulfate ion concentration. Also preferred are means for maintaining the second vessel or set of vessels at a reduced pressure. Most preferred is that means be included in at least one said vessel for incorporating a crystal modifier (e.g. a sulfonic acid, a sulfonic acid salt, tall oil fatty acids or alkoxylated or esterified tall oil fatty acids) in the crystallizer. The system can be used in the anhydrite, hemihydrate or gypsum types of processes.

Abstract: When sulfate ions and a solution of monocalcium phosphate are reacted under conditions which result in the formation of a slurry comprising calcium sulfate hemihydrate and phosphoric acid of about 35% to about 55% P.sub.2 O.sub.5, filtration is improved when a sulfonic acid, a sulfonic acid salt, tall oil fatty acid or alkoxylated or esterified tall oil fatty acid and mixtures thereof is present in the slurry (preferably at 1-1000 ppm). Preferably a two vessel reaction system is used in which the reaction slurry undergoes intra- and inter- vessel circulation (preferably through a draft tube). The solution portion of the slurry in the first vessel (the "dissolver") is preferably maintained at a negative sulfate concentration (i.e. excess Ca.sup.+2) and the solution in the second vessel (the "crystallizer") is preferably maintained at a positive sulfate ion concentration, most preferably at a reduced pressure, (e.g. to provide evaporative cooling).

Abstract: Phosphate rock and sulfuric acid are reacted to produce phosphoric acid and calcium sulfate by means of the hemihydrate wet process. In this improved process, the calcium sulfate hemihydrate is crystallized from solution in the presence of an organic sulfonic acid or a derivative thereof. The organic sulfonic acid or its derivative improves the growth of the calcium sulfate hemihydrate crystals and thus improves the filtration rate of the slurry produced in this improved process.

Abstract: Phosphate rock and sulfuric acid are reacted under conditions which result in the formation calcium sulfate hemihydrate and phosphoric acid of about 30% to about 55% P.sub.2 O.sub.5. A two vessel reaction system is used in which the reaction slurry undergoes inter- and intra- vessel circulation. This results in excellent dispersion of reactants and minimization of temperature and concentration gradients throughout the slurry.

Abstract: A process for the extraction of metallic impurities from an unpurified aqueous phosphoric acid phase by solvent extraction employing an organic extractant phase containing an organic sulfonic acid in its H.sup.+ form. After the extraction step and separation of the organic extractant phase from the aqueous phosphoric acid phase, residual P.sub.2 O.sub.5 values are recovered from the organic extractant phase by washing the organic extractant phase with a wash phase consisting of water or dilute phosphoric acid. The sulfonic acid in the organic extractant phase can be regenerated to its H.sup.+ form with a mineral acid and recycled.

Abstract: Water immiscible organic acid phosphates used in conjunction with water immiscible organic sulfonic acids results in an improved process for the purification of phosphoric acid. An increase in the extraction of ionic metallic impurities and a decrease in the extraction of P.sub.2 O.sub.5 values from the aqueous phosphoric acid phase is observed in the improved solvent extraction process.

Abstract: Apparatus for melting sulphur, including an upstanding tube, or tubes, each being adapted to receive solid sulphur in its top open end and each having a heating jacket therearound. The sulphur along the tube wall is melted and caused to flow along the wall surface and out of the lower end of the tube. A heated plate is spaced from the lower end of the tube whereby flow of the melted sulphur from the tube is permitted, additional sulphur being melted by the plate, and flow of solid sulphur is stopped. The plate is sloped to permit the flow of the liquid sulphur into a trough for flow for storage or use elsewhere.A method of melting sulphur by which solid sulphur is fed into the upper end of a vertical tube. The tube is heated to melt the sulphur against the tube wall. A film of melted sulphur is caused to flow down the wall and out of the tube bottom onto a sloping, heated plate and into a trough for removal or use. The flow of solid sulphur is stopped by the plate.

Abstract: Solid sulfur pellets are prepared from molten sulfur using a gun and pelletizing chamber. Sulfur is ejected from a gun in a form of a thin sheet and dispersed and solidified into solid pellets with a water jet. The pellets and water are separated.

Abstract: A water immiscible amine-solvent system, preferably a solution of a water immiscible amine in mineral spirit solvent, is used to extract phosphate values from crude aqueous phosphoric acid solutions leaving behind impurities, e.g., calcium, magnesium, iron and aluminum. Phosphoric acid of water white quality may then be produced and removed from the amine-solvent organic phase by contacting the amine-solvent containing the extracted phosphate values with sulfur dioxide and water substantially in the absence of oxygen, the amount of water employed determining the concentration of phosphoric acid produced, thermally stripping the sulfur dioxide from the amine-solvent system substantially in the absence of oxygen in order to recycle both the amine-solvent system and sulfur dioxide.