Abstract: An emobodiment of a process for filtration of a slurry containing fine particles is a process comprising:(a) filtering phosphoric acid containing sludge-forming particulate impurities through a fabric filter whereby particulate impurities are separated from the phosphoric acid and retained on the surface of the fabric filter to form a filter cake comprising particulate impurities and entrained phosphoric acid;(b) contacting the filter cake with a wash fluid (e.g., water) to remove a major portion of the entrained phosphoric acid from the filter cake, thereby forming a washed filter cake; and,(c) removing the washed filter cake to expose a fresh surface of the fabric filter, for contacting with additional phosphoric acid containing particulate impurities.Preferably, the washed filter cake is removed by the introduction of pressurized air to the side of the fabric filter opposite the washed filter cake.

Abstract: Monocalcium phosphate, phosphoric acid and/or potassium phosphate, calcium fluoride and gypsum are produced in a process involving acidulation of phosphate rock with phosphoric acid, and wherein monocalcium phosphate dissolved in phosphoric acid is formed during acidulation. In important features, insolubles and impurities are removed and a portion of the monocalcium phosphate may be separated and recovered. Alkali metal ion is added to the solution to form alkali metal fluosilicate, such as K.sub.2 SiF.sub.6, is separated and hydrolyzed with calcium ion to form CaF.sub.2 and the solution is recycled as RH.sub.2 PO.sub.4 /H.sub.3 PO.sub.4 for further reaction with fluorides, where R is alkali metal. A portion of the MCP/H.sub.3 PO.sub.4 solution and/or crystallized monocalcium phosphate can then be reacted with potassium sulfate, potassium bisulfate, or mixtures thereof, to form KH.sub.2 PO.sub.4 or KH.sub.2 PO.sub.4 /H.sub.3 PO.sub.4 solutions, and gypsum or with H.sub.2 SO.sub.4 to produce phosphoric acid.

Abstract: The concentration of impurities in wet-process phosphoric acid limits the usefulness of the acid for the production of fertilizers, feedgrade phosphate and detergents. The aluminum, magnesium, and fluoride impurities are removed with the calcium sulfate hemihydrate filter cake by hydrolyzing and recycling the off-gas scrubber solutions in the presence of a ferric iron catalyst. The aluminum and magnesium are reduced to less than 0.1 percent in the acid product by the precipitation of (Ca,Mg)Al.sub.2 F.sub.8 .multidot.2H.sub.2 O, which is acid insoluble and suitable for storage with the byproduct calcium sulfate. Ferric iron also serves as a catalyst for the simultaneous precipitation of (Na,K).sub.2 SiF.sub.6. Subsequent additions of potassium as, for example, in the teachings of Gilbert (U.S. Pat. No. 3,338,675), can then be applied to obtain a purified phosphoric acid product suitable for most commercial applications.

Abstract: A wet process for producing phosphoric acid and phosphohemihydrate by acidulation of phosphate rock. A strong phosphoric acid is obtained with concomitant production of an improved calcium sulfate that is extremely low in radioactivity by operation in Region II for shorter time so as to produce small sized hemihydrate particles, then hydration of a substantial proportion but less than all of the hemihydrate to coarse gypsum substantially free of radioactivity in a dilute acidic aqueous slurry at a temperature and P.sub.2 O.sub.5 concentration selected so as to be within Region I of FIG. 1 and having a substantial weight proportion of coarser gypsum particles that are substantially free of radioactivity.

Abstract: In a process for producing a defluorinated product containing calcium, sodium and phosphorus, by calcination of a mixture of phosphate rock, with caustic soda, phosphoric acid and water, an improvement comprises maintaining the amount of phosphoric acid in the mixture such that the ratio of phosphorus in percentage by weight on a dry basis in said mixture-to-the phosphorus desired in percentage by weight in the calcined product is substantially equivalent to the ratio of the calcium in percentage by weight on a dry basis in the mixture-to-the calcium in percentage by weight in the calcined product. The process is especially useful where the phosphate rock has a bone phosphate of lime analysis of about 73% or less (e.g., about 71.5%), and also where the caustic soda is added to a mixture of phosphate rock and phosphoric acid prior to the addition of water.

Abstract: This invention comprises a method for removing fluorine from natural phosphates, superphosphate materials and wet process phosphoric acids starting materials comprising(a) admixing rock phosphate having a fluorine content above that desired with an acid mixture within the range of rock:acid mixture of about 0.8 to 1 and 1:1.4 by weight;(b) said acid mixture being substantially concentrated phosphoric acid and concentrated sulfuric acid in a range of phosphoric:sulfuric of about 1:1 to 5:1 by weight;(c) said admixing being at a temperature in the range of 215.degree. to 265.degree. F. while adding water in an amount of up to about 12% by weight of the total mixture and then subjecting the above charge;(d) in a first heating stage adding (1) recycle in an amount substantially of recycle to charge of 1:1 to 10:1 by weight (2) and water while heating to a temperature in the range of 300.degree. F. to 400.degree. F.

Abstract: A phosphate rock slurry, which may be used in the production of wet process phosphoric acid, is provided by wet grinding the rock with partially neutralized, acid water.In one aspect, wet process phosphoric acid is made by advantageously recycling mineral acid waste water effluent of the process. All or a portion of the effluent can be at least partially neutralized with neutralizing agent, e.g., by contact with the base-forming constituents of phosphate rock or extraneous neutralizing agent, e.g., preferably ammonia, to provide a mixture which is wet ground to produce a processable slurry. In one particularly preferred aspect, all of the acid water is at least partially neutralized with phosphate rock and a portion of this acid water is advantageously further neutralized with an extraneous neutralizing agent. The slurry is provided by such neutralization at a pH compatible with the milling, e.g., grinding, media utilized.

Abstract: A process for solubilizing uranium and other values in an ore containing the same together with aluminum and phosphorus and effecting regeneration of a mineral acid employed to solubilize the ore. The regeneration is effected by heating the spent acid solution resulting from solubilization of the ore in a reaction zone to a temperature above 100.degree. C. while maintaining at least the autogenic pressure of the heated solution within the reaction zone. The treatment causes aluminum phosphate to precipitate from the solution while simultaneously causing regeneration of at least a portion of the mineral acid in the solution that was consumed to originally solubilize the ore. The dissolved uranium and other elements of value can be recovered from the solution, either before or after acid regeneration, by any known technique. The regenerated mineral acid then can be used to solubilize fresh ore.

Abstract: The level of radioactivity in gypsum produced from phosphate rock can be reduced by adding to the slurry of acid and phosphate rock in the conventional process for producing phosphoric acid a combination of concentrated nitric acid or hydrochloric acid and an ammonium salt, especially ammonium nitrate or ammonium phosphate, before the precipitation of the calcium sulfate.

Abstract: Phosphate is upgraded to remove slimes therefrom by a process which comprises the steps of:(a) contacting the phosphate ore with a phosphoric acid solution having a concentration of about 1 to 20 weight percent in a desliming unit for a sufficient time to form a suspension containing the slimes and the calcium and phosphate components;(b) passing said suspension through a solids separator to separate deslimed phosphate ore from the slime suspension and recovering the deslimed phosphate ore;(c) removing the slime suspension to a separator to separate the slime solids from the filtrate liquids; and(d) recycling the filtrate liquids to the desliming unit to provide at least a portion of the phosphoric acid solution.

Abstract: Phosphate rock, including low grade phosphate ore, is treated to recover phosphoric acid and other valuable products by a series of steps including contacting phosphate ore with a weak phosphoric acid to form a suspension of at least a portion of the slimes contained in the ore so that the slimes can be separated from the ore, and separating the slimes to provide a deslimed phosphate ore. Deslimed phosphate rock is solubilized with phosphoric acid to convert at least a portion of the calcium contained in the rock and form a solution of monocalcium phosphate and phosphoric acid. After removal of solids, this solution can be treated with sulfuric acid in a gypsum crystallizer to form gypsum and the phosphoric acid product wherein filterable gypsum crystals are obtained by maintaining a total SO.sub.3 content of 1.5-4 wt. % in a first crystallizer and neutralizing the SO.sub.3 in a second crystallizer.

Abstract: Foam generated during the digestion of phosphate rock is removed from the slurry either by overflow, mechanical sweeps, or by vacuum from strategically located nozzles connected to vacuum lines. The foam, after liquefaction, is returned to the filter where it results in improved filtration and return of soluble P.sub.2 O.sub.5.

Abstract: A process for the manufacture of phosphoric acid from phosphate rock is provided. The phosphate rock is digested or acidulated with an acid solution containing oxalic acid to produce phosphoric acid and calcium oxalate. Useful by-products are also formed and include calcium carbonate and ammonium oxalate. More specifically, the process provides for the production of phosphoric acid, ammonium phosphate and useful by-products utilizing synthesis gas and air to produce oxalic acid and ammonia. The synthesized oxalic acid is utilized for phosphate rock digestion to produce phosphoric acid, which can be reacted with ammonia to produce ammonium phosphate. Calcium oxalate from phosphate rock digestion is utilized to produce calcium carbonate, ammonium oxalate and oxamide.

Abstract: A multiple-stage thermal beneficiation process for phosphate ores which comprises calcining a phosphate ore in a first stage at a temperature sufficient to destroy substantial quantities of organic impurities in the phosphate ore but not so high as to cause excessive sulfide formation; followed by the calcining of the product from the first stage in a second stage at a temperature at which an additional amount of organic carbon impurities are destroyed but at a temperature which does not detrimentally reduce the surface area of the phosphate ore.

Abstract: Recovery of yttrium, lanthanides and radium free calcium sulphate in a phosphoric acid process by digesting phosphate rock with an excess of phosphoric acid in the presence of more than about 5 wt.% of SO.sub.4 -ions calculated to the amount of phosphate rock, separating out the insoluble residue and recovering yttrium and lanthanides therefrom, precipitating calcium sulphate from the remaining solution with sulphuric acid and separating this calcium sulphate from the resulting phosphoric acid solution.

Abstract: Phosphoric acids of significantly different content of soluble impurities, especially magnesium compounds, can be blended to produce a phosphoric acid with a decreased tendency for forming detrimental solids when converted to a liquid fertilizer or on storage, or during transportation as when the acid is transported by ocean vessel or railroad tank car. The blending can be effected either before or after a concentration step or steps (e.g., evaporation to "merchant grade" or to superphosphoric acid). For example, wet process phosphoric acid produced by a dihydrate or gypsum process can be blended with a phosphoric acid produced by a hemihydrate process.

Abstract: The viscosity of phosphate rock slurries is reduced by incorporating in the slurry both sodium tripolyphosphate and an alkaline material, particularly sodium hydroxide. The combined amount of these two materials required to achieve a given viscosity reduction is significantly lower than the weighted average of the amounts required for each to produce individually the same viscosity reduction. The defined alkaline materials, other than sodium hydroxide, are sodium carbonate, ammonium hydroxide and potassium hydroxide.

Abstract: A process is described for extracting phosphoric acid and metal values, such as uranium, from phosphate rock using hydrochloric acid and independently extracting the phosphoric acid and metal values from a slurry of the acidulated rock.

Abstract: Disclosed is a method for treating substantially homogeneous monocalcium phosphate (MCP) solutions that contain undesirable amounts of radium which comprises centrifuging these MCP solutions sufficiently to separate at least a portion of the radium from the solution. Such treated MCP solutions may then be reacted with sulfuric acid to simultaneously produce a phosphoric acid solution and a calcium sulfate precipitate such as gypsum having low levels of radium content.

Abstract: Phosphate rock can be heat treated at 380.degree.-600.degree. C. to convert the organics to filterable carbon and the rock converted to wet process phosphoric acid of reduced color and with reduced foaming. Rocks having high acid soluble organics but low total organics, and rocks containing a high content of acid insoluble heat labile iron sulphide are especially suitable.

Abstract: The air cooling of exothermic reaction vessels is improved by providing a cooling air recirculation loop wherein substantial amounts of the cooling air are recycled through the system with but a small fraction thereof being discharged to ambient, and after the condensable/soluble off-gases are depleted therefrom and with addition thereto of but minor amounts of additional feed air. Such technique is well suited for controlling the temperature of the digestion of phosphate rock with sulfuric acid, in the known wet-process for the production of phosphoric acid.

Abstract: A process, for removing solid impurities from impure phosphoric acid containing solids, comprising:(a) passing said acid at an elevated temperature through a filter cake of a phosphoric acid-resistant filter aid supported on a porous medium, thereby to cause at least a portion of said solid impurities of said acid to be filtered therefrom and to be retained by said filter cake;(b) contacting at least a portion of said filter cake with a displacing liquid, maintained at a temperature and in an amount sufficient to cause at least a portion of the acid which remains in said filter cake to pass through said filter cake without fracturing said filter cake;(c) collecting said filtered acid which passes through said filter cake; and(d) removing an impurity-containing portion of said filter cake after contact with said acid and displacing liquid, thereby to present a fresh surface for subsequent filtration.

Abstract: The invention relates to a method for the preparation of phosphoric acids by the wet process by reaction of at least one natural phosphate on at least one strong acid, such as, preferably, sulphuric acid, characterized in that said reaction is effected in the presence of 50 to 500 g/t of phosphate consumed, of at least one non-ionic surface-active agent obtained by condensation of 2 to 30 molecules of ethylene oxide per molecule of at least one branched fatty alcohol.

Abstract: The invention describes the extraction of values, especially metal values such as copper and uranium, from minerals by passing the mineral in admixture with a leaching agent for the values through a contactor and extracting the values with an extractant stream immiscible with the mixture and of lesser density so that the values are captured by the extractant and can be withdrawn with the extractant and, if desired, isolated by any suitable means.

Abstract: An improved method for producing hydrogen fluoride from fluoride bearing ores, such as fluorospar and fluorapatite, by reaction of the ore as a slurry in fluorosulfonic acid. The slurry is heated by the exothermic heat of the reaction to vaporize volatile phosphorous compounds and substantial quantities of hydrogen fluoride. The calcium fluoride is substantially reacted to form hydrogen fluoride. High silica fluorospar ores can be used since silicon tetrafluoride is not formed with fluorosulfonic acid. Another feature provides for addition of calcium fluoride to the slurry to react with the by-product sulfuric acid in the residual solids to eliminate the sulfuric acid recovery step in the process. Hydrogen fluoride produced is recovered, together with the hydrogen fluoride produced from the hydrolysis or pyrolysis of the intermediate fluorophosphorous compounds. Additionally, at least a portion of the hydrogen fluoride can be reacted with sulfur trioxide to form fluorosulfonic acid for makeup in the process.

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: A process as described for extracting at least two desired constituents from a mineral using a liquid reagent which produces the constituents, or compounds thereof, in separable form and independently extracting those constituents, or compounds thereof. The process if especially valuable for the extraction of phosphoric acid and metal values, such as uranium from phosphate rock.

Abstract: Disclosed is a process for producing a calcium sulfate product containing low amounts of radium comprising the steps of:(a) adding at least one sequestering agent to a substantially homogeneous radium-containing monocalcium phosphate (MCP) solution, the amount of the sequestering agent added being at least the stoichiometric amount necessary to complex with the radium in the MCP solution;(b) reacting the treated MCP solution with H.sub.2 SO.sub.4 to form a monocalcium phosphate/phosphoric acid solution, to precipitate a first calcium sulfate product, and to precipitate at least a portion of the radium, the amount of said H.sub.2 SO.sub.4 being up to about 50% of the stoichiometric amount necessary to react with the total CA.sup.++ present in the MCP solution;(c) separating the monocalcium phosphate/phosphoric acid solution from the radium-containing calcium sulfate precipitate;(d) then reacting the monocalcium phosphate/phosphoric acid solution with H.sub.2 SO.sub.

Abstract: A process is disclosed for improving the dispersability of siliceous (preferably diatomite) filter aid particles in hot (i.e., 140.degree. F. or higher) aqueous acid systems used in the "wet process" formation of orthophosphoric acid from phosphate rock. In this process the filter aid particles are prewetted with water to cause the adsorption of 15 to 75 weight percent of water on the filter aid prior to dispersing the prewetted filter aid in the acid system.

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: In a multi-stage, multi-vessel phosphoric acid production system where a first reaction vessel contains a first slurry comprising calcium sulfate hemihydrate, monocalcium phosphate and phosphoric acid and a second reaction vessel contains a second slurry comprising calcium sulfate hemihydrate, sulfuric acid and phosphoric acid, in which the reaction slurry undergoes intra- and inter-vessel circulation, preferably through a draft tube, an improved start-up procedure involves filling the system with heated phosphoric acid having a P.sub.2 O.sub.5 analysis in the range of about 28 to about 38% (e.g. 31%), then feeding phosphate rock to the system, preferably in a separate reaction vessel, while phosphoric acid is recycled from a fourth, filter feed vessel, until the solids content in said slurry is in the range of 25-35% (e.g. about 30%) while the sulfate content in the first vessel is maintained at a negative level (e.g. excess calcium ion) and at a positive level in the second, crystallizer vessel.

Abstract: Metal ion impurities are removed from phosphoric acid by adding to the acid a precipitant comprising ions of calcium and fluorine to cause precipitation of a magnesium-containing precipitate. A preferred precipitant is one containing calcium flouride, such as the sludge obtained by treating pond water from a phosphoric acid plant with a calcium-containing compound. Preferably, the soluble sulfate content of the phosphoric acid is maintained at at least about 2% by weight. An animal feed can be prepared from the precipitate by combining the precipitate with phosphate rock, water, and a sodium-containing compound, and then calcining the combination.

Abstract: A method for removing impurities from wet process produced phosphoric acid and recovering phosphate values retained by the impurities is disclosed. The wet process produced phosphoric acid is filtered through a diatomite filter cake in a porous medium at a temperature from about 57.degree. C. to about 77.degree. C. During filtering an impurity-containing upper portion of the filter cake is removed exposing a fresh surface of the filter cake. An aqueous slurry is formed with the removed portion of filter cake. The slurry is filtered to recover a filtrate containing a major portion of the phosphate values retained by the removed portion of the filter cake.

Abstract: A method is disclosed for the acidulation of phosphate rock and the production of substantially pure alkali metal phosphates, calcium phosphates, and phosphoric acid which are essentially free of fluorides and recovery of the fluorine values from the starting phosphate rock in useful form. The steps of the method comprise initial acidulation of phosphate rock with a phosphoric acid solution containing sufficient alkali metal values to provide R.sub.2 O in the system, where R is alkali metal, to solubilize the phosphates and form an insoluble precipitate comprising a mixture of impurities, sand (SiO.sub.2) and the fluorides, from which the fluorides can be recovered in usable form. In preferred embodiments, after removal of the precipitate containing the fluorides, a portion of the solution of phosphoric acid and calcium phosphate is reacted with sulfuric acid and RHSO.sub.4 or R.sub.2 SO.sub.4 where R is alkali metal, to form a solution of RH.sub.2 PO.sub.

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: A method for pretreating phosphoric acid to prevent the formation of a mass of suspended solids (i.e., "crud") during solvent extraction of the acid is described. Prior to solvent extraction, the acid is contacted with a liquid hydrocarbon such as kerosene which collects the crud-forming agents. The mixture of liquid hydrocarbon and collected crud-forming agents is separated from the acid and the liquid hydrocarbon is regenerated for reuse in the first step of the method.

Abstract: An improved method for treating calcium phosphate sources such as bone phosphate and phosphate rock with fluorosulfonic acid in the presence of a limited amount of moisture whereby over 98.00% of the phosphorous is converted to volatile compounds that can be subsequently hydrolyzed. A substantial excess of fluorosulfonic acid is utilized to contact the phosphate ore as a slurry. The phosphorous products are primarily phosphorous pentafluoride and phosphorous oxyfluoride, and to a limited extent difluorophosphoric acid. A trace of water apparently catalyzes the reaction. The production of phosphorous pentafluoride is favored by up to one part of water to eight parts of ore by weight in the presence of excesses of fluorosulfonic acid. The method includes the hydrolysis of the volatile compounds to phosphoric acid and hydrogen fluoride. Hydrogen fluoride is then recycled to react with the required sulfur trioxide to make the requirement of fluorosulfonic acid for the process.

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: Phosphoric acid with a high fertilizer-nutrient content is produced by decomposing phosphate rock with nitric acid followed by precipitation of calcium ions with sulfate. The steps of the process are as follows:A. Decomposing phosphate rock with (7-2x) to (17-2x) mol nitric acid and x mols sulfuric acid per mol phosphorous pentoxideA.sub.1 whereby x may take on any values between 0 and a maximum value X, which is limitedA.sub.2 by the condition that the mol ratio H.sub.2 SO.sub.4 :HNO.sub.3 may never exceed the value 8:1 andA.sub.3 by the condition that in the decomposition solution, into which, if need be, also ammonium sulfate is introduced, the content of sulfate ions after precipitation of the semihydrate gypsum is between 10 to 150 g/l solution;B. Adding--if no or not enough sulfuric acid has been used for precipitating calcium sulfate--ammonium sulfate in amounts corresponding to condition A.sub.

Abstract: Addition of sodium naphthaleneformaldehyde sulfonate to phosphate rock slurry in manufacture of phosphoric acid by the wet process permits reduction of the viscosity and/or water content of the slurry so that increased pumpability of the slurry is obtained.

Abstract: Monocalcium phosphate, phosphoric acid and/or potassium phosphate containing fertilizers are produced in a process involving acidulation of phosphate rock with phophoric acid in the presence of added silicon dioxide and potassium ion whereby fluorides contained in the rock are converted to K.sub.2 SiF.sub.6, wherein monocalcium phosphate dissolved in phosphoric acid is formed during acidulation. In an important feature, the K.sub.2 SiF.sub.6 is separated and hydrolyzed to regenerate the K.sub.2 O from K.sub.2 SiF.sub.6 as recycled KH.sub.2 PO.sub.4 /H.sub.3 PO.sub.4 solution for further reaction with fluoride from fresh phosphate rock feed. A portion of the MCP/H.sub.3 PO.sub.4 solution and/or crystallized monocalcium phosphate can then be reacted with potassium sulfate, potassium bisulfate, or mixtures thereof, to form KH.sub.2 PO.sub.4, or KH.sub.2 PO.sub.4 /H.sub.3 PO.sub.4 solutions, and gypsum. In a closely related embodiment, the remaining MCP/H.sub.3 PO.sub.

Abstract: Magnesium-bearing phosphate rock in small grain size is converted into phosphoric acid so that no by-products, which are difficult to dispose of are produced. The crushed rock is mixed with water and subsequently acidified with nitric acid, the reaction product being filtered and washed before the neutralization point is reached. The wet and filtered rock is treated with nitric acid to form phosphoric acid and a slurry of calcium nitrate tetrahydrate. The previously formed filtrate is mixed with the calcium nitrate tetrahydrate slurry and this mixture is reacted with ammonia and carbonic acid to form ammonium nitrate, magnesium carbonate and calcium carbonate, which are then separated into an ammonium nitrate solution and a mixture of magnesium and calcium carbonates.

Abstract: The filtration rate and/or washability of crystals of gypsum produced during the wet process for the production of phosphoric acid are improved by adjusting the notional Al.sub.2 O.sub.3 :P.sub.2 O.sub.5 and reactive SiO.sub.2 :F ratios of the phosphate rock to within certain ranges. The adjustment may be achieved by addition of sources of aluminium and silica to the phosphoric acid process.

Abstract: A method is disclosed for the manufacture of phosphoric acid directly from phosphate rock wherein the crushed phosphate rock is mixed with dilute phosphoric acid to form a slurry and the slurry is then heated to produce calcium monophosphate. Thereafter, oxalic acid is added to the slurry to precipitate the calcium therein as calcium oxalate which is separated. The liquid resulting therefrom which contains the phosphoric acid from the rock is then treated conventionally to recover the phosphoric acid therein.

Abstract: Phosphate ora matrix is treated to recover P.sub.2 O.sub.5 values. The matrix may be the phosphate ore as it is mined, or it may be residue formed upon dewatering benefication slimes. Without being subjected to beneficiation, this matrix is slurried with an organic solvent in a slurry vessel. When the slurry is mixed with a strong mineral acid, a system having a single liquid phase is formed with the organic solvent serving as a vehicle for distribution of the mineral acid which in turn solubilizes P.sub.2 O.sub.5 values for their extraction from the matrix. Thereafter the P.sub.2 O.sub.5 values are separated from the solid phase and then removed from the organic solvent.

Abstract: A method of making phosphoric acid and gypsum through a precipitated phosphate intermediary which comprises mixing a precipitated dicalcium phosphate with a highly dispersed reaction admixture of sulfuric acid and phosphoric acid, at a temperature between about 25.degree. and 80.degree. C; and withdrawing and separating phosphoric acid containing up to about 45% or more P.sub.2 O.sub.5 and gypsum containing generally less than 0.25% P.sub.2 O.sub.5. The resultant gypsum is highly filterable and very low in occluded phosphate value. Preferably, the process involves first obtaining a weak phosphoric acid solution from and by leaching as-mined phosphate mineral containing material to obtain the precipitated dicalcium phosphate; and then converting the precipitated phosphate by the process to the strong phosphoric acid solution.

Abstract: A method is disclosed for the acidulation of phosphate rock and the production of substantially pure alkali metal phosphates, calcium phosphates, and phosphoric acid which are essentially free of fluorides and recovery of the fluorine values from the starting phosphate rock in useful form. The steps of the method comprise initial acidulation of phosphate rock with a phosphoric acid solution containing sufficient alkali metal values to provide R.sub.2 O in the system, where R is alkali metal, to solubilize the phosphates and form an insoluble precipitate comprising a mixture of impurities, sand (SiO.sub.2) and the fluorides, from which the fluorides can be recovered in usable form. In preferred embodiments, after removal of the precipitate containing the fluorides, a portion of the solution of phosphoric acid and calcium phosphate is reacted with sulfuric acid and RHSO.sub.4 or R.sub.2 SO.sub.4 where R is alkali metal, to form a solution of RH.sub.2 PO.sub.

Abstract: A process for reducing formation of calcium sulphate scale during the washing of calcium sulphate hemihydrate crystals by washing the crystals with a liquor containing certain surface-active agents in sufficient amount to give a concentration of from 0.0002 to 1% by weight of surface-active agent in the wash liquors.

Abstract: The invention relates to a process for the production of phosphoric acid containing calcium phosphates, i.e. Ca-containing phosphoric acid, by evaporating Ca-containing mother liquor from Odda process, whereby practically all the remaining nitrate and fluorine are removed in the form of HNO.sub.3, HF and SiF.sub.4, in which process the Ca-containing mother liquor is given a Ca/P weight ratio which is lower than 0.45 and is evaporated while recycling Ca-containing phosphoric acid, the recirculation being so controlled that the liquor has a phosphorus concentration during evaporation which is always adequate to prevent the liquor from forming a paste-like mass. Thus, it was discovered that the undesirable paste-like consistency experienced when calcium is present during evaporation can be avoided by controlling the phosphorus content.

Abstract: This invention relates to a froth flotation process for recovering scheelite from scheelite ores. This invention comprises adding a sulphonate collector or a mixture of a sulphonate collector and a fatty acid collector to a pulp containing the ores, selectively floating the scheelite from the ores and recovering the flotation concentrate thus obtained.