Abstract: Techniques for smart whitelisting for Domain Name System (DNS) security are provided. In some embodiments, a system/process/computer program product for smart whitelisting for DNS security in accordance with some embodiments includes receiving a set of network related event data, wherein the set of network related event data includes Domain Name System (DNS) related event data; receiving a set of network related threat data, wherein the set of network related threat data includes DNS related threat data; and generating a whitelist using the set of network related event data and the set of network related threat data, wherein the whitelist includes a subset of network domains included in the DNS related event data based on a data driven model of the DNS related event data and the DNS related threat data.

Abstract: Provided is a method for producing phosphoric acid and at the same time obtaining alpha-hemihydrate gypsum including: adding a phosphate rock powder and a part of dilute sulfuric acid into an extraction tank, carrying out an extraction reaction on same, separating a clear liquid from the obtained mixed slurry, sending the clear liquid, as a finished product phosphoric acid, into an acid storeroom, and transferring a separated solid, together with the rest mixed slurry, into a crystal transformation tank; and adding sulfuric acid and a crystal transformation agent into the crystal transformation tank, carrying out a crystal transformation reaction for 1.5-7.5 h at 60° C.-130° C., and solid-liquid separating the obtained mixed acid slurry, wherein the solid can be dried into a gypsum powder, or may be not subjected to a drying step and made into gypsum products such as gypsum boards, gypsum building blocks and gypsum members by directly adding water.

Abstract: Processes for enhancing filtration rate and/or clarification of phosphoric acid produced by the wet process and containing suspended insoluble particulates by adding to one or more stage of the wet process phosphoric acid production stream an effective amount of a reagent including polymeric microparticles characterized as being anionic or amphoteric and having a weight average molecular weight of greater than 60 Million daltons are provided herein.

Abstract: Processes for inhibiting scale produced during wet process phosphoric acid production by adding a scale-inhibiting amount of a reagent having a primary amine-containing polymer, or salt thereof, to one or more stages of a wet process phosphoric acid production stream are provided herein, wherein the primary amine-containing polymer includes an A mer according to Formula (I): where R is H, C1-C6 alkyl, C2-C6 alkenyl, halide, or carboxyl; R1 is H, C1-C6 alkyl, or C2-C6 alkenyl; R2 is H or an A mer according to Formula (I) as herein defined; R3 is chosen from a direct bond or a C1-C12 alkyl, C2-C12 alkenyl, or a C6-C12 aryl group; and n is an integer chosen to provide a weight average molecular weight of the primary amine-containing polymer of at least 300 Daltons, and wherein the percentage of primary amines in the polymer is from 30 mole % to 100 mole % based on the total percentage of mer units in the polymer.

Abstract: A method for producing phosphoric acid, comprising attack in an aqueous medium of phosphated rock with sulfuric acid, with formation of a first dihydrate slurry suspended in an aqueous phase having a free P2O5 content between 38 and 50% and a free SO3 content of less than 0.5%, conversion of this first slurry by heating with recrystallization of the solubilized calcium sulfate giving rise to a second hemihydrate slurry, and separation in the second slurry between a production phosphoric acid and a hemihydrate cake, characterized in that it comprises during the attack, addition of a fluorine source in the first slurry in a content from 1% to 5% by weight of F relatively to the P2O5 contained in the phosphated rock.

Abstract: Methods for preventing or reducing the formation of scale in a wet-process phosphoric acid production process by intermixing a scale inhibiting reagent at one or more step of the phosphoric acid production process in an amount sufficient to prevent or reduce scale are provided.

Abstract: A process and system for producing phosphoric acid. Phosphate rock is dissolved in phosphoric acid in a reaction vessel to form a slurry. The slurry is then reacted in a first stage of crystallization with sulfuric acid to produce calcium sulfate hemihydrate and phosphoric acid. The product acid is separated from the hemihydrates via filtration, and the filter cake is then reacted, in a second crystallization step, with additional sulfuric acid to produce dihydrate calcium sulfate (gypsum) and recovery solution. The gypsum is separated from the recovery solution via filtration and removed as a by-product. The recovery solution is recycled back to the transformation tank and to the hemihydrate filtration step. A feed acid tank combines wash solution, recovery solution and product acid. Once adjusted to a target P2O5 concentration, it is fed to the initial reactor vessel to dissolve the phosphate ore.

Abstract: The invention relates to a method for producing phosphoric acid, including: attacking phosphate rock by means of sulfuric acid between 70° and 90° C. with formation of a first calcium sulfate dihydrate crystal slurry, the aqueous acid phase of said slurry having free P2O5 content between 38 and 50 wt % and free SO3 content that is less than 0.5 wt % and greater than 0.05 wt %; converting said first slurry by means of heating at a temperature greater than 90° C., thus giving rise to a second slurry formed of calcium sulfate hemihydrate crystals; and, within the second slurry, separating a produced phosphoric acid, having a free SO3 content that is less than 2%, and a calcium sulfate hemihydrate filter cake.

Abstract: Disclosed is a process for any productions that involve reacting or mixing two or more substances to form one or more new substances under low supersaturation. However, the specific process used to exemplify the present invention is the “wet process” phosphoric acid production, in which this process is achieved through dissolving the phosphate ore and dispersing the sulfuric acid separately and simultaneously with the gypsum slurry that has roughly stoichiometrically balanced calcium and sulfate ions in the solution and is also at considerably low supersaturation. The slurry carried out digesting the phosphate ore and the slurry accomplished dispersing the sulfuric acid then mix together to form the said gypsum slurry that has roughly stoichiometrically balanced calcium and sulfate ions in the solution and is also at considerably low supersaturation.

Abstract: The present disclosure is directed to a filter support having a surface with a plurality of perforations therein. At least one spray bar may be substantially fixed adjacent to the surface of the filter support. A spray bar may include a plurality of nozzles for directing a pressured fluid toward the filter support. The filter support may further include a motor for causing the filter support to move in a cyclical manner while the spray bar directs pressurized fluid toward the filter support.

Abstract: A process and system for recovering waste heat from a kiln used for lime or cement production. The system unifies the kiln, a waste heat recovery and power generation circuit and a dry scrubber for scrubbing the pollutants from the kiln offgas. Essentially, the system employs the boiler component of the waste heat recovery and power generation circuit as a heat exchanger to recover the waste heat from the kiln, which is used to drive the steam turbines. The heat absorption from the latter stage lowers the temperature of the kiln offgas sufficiently for optimum performance from the scrubber. The presence of lime particles in the offgas effectively protects the boiler tube surfaces from corrosion which would occur at optimum scrubber temperatures, and subsequently provides the lime required as a scrubbing medium for the dry scrubber. Further, the efficient scrubbing allows for the use of any fuel for firing the kiln inclusive of high sulphur content compounds.

Abstract: The present invention relates to a method of preparing wet process phosphoric acid, which comprises: dividing raw materials which contain phosphate rock slurry and sulfuric acid into two parts, and then feeding these two parts into two reactors separately. In the first reactor, feeding 70–90 wt. % of the total amount of the slurry and sulfuric acid, in which the ratio of phosphate rock slurry to sulfuric acid to recycled phosphoric acid is set to be 1:0.6˜0.8:1.0˜2.5. 10˜30% of the reaction solution directly flows into conversion cell, participating in the conversion reaction of dihydrate gypsum. Thus resulted phosphoric acid concentration is 33˜39 wt. %. The recovery efficiency of P2O5 is 99% or more. When putting coke powders in the conversion solution as filter aid, the filtration efficiency can be improved by 10˜30%, and in so produced hemihydrate gypsum, P2O5 is 0.05˜0.2%, water of hydration is 4˜8%. The product can be used for producing sulfuric acid and cement without baking dry.

Abstract: A defoaming composition useful in high strength acid media includes an ester condensate of a C12-C20 fatty acid and a at least one alcohol derivative selected from the group consisting of C1-C4 alcohol ethoxylates having at least three ethoxylate residues per molecule, C1-C4 alcohol propoxylates having at least three propoxylate residues per molecule and C1-C4 alcohol mixed ethoxylate-propoxylates having at least three total ethoxylate and propoxylate residues per molecule. The condensate is preferably liquid at room temperature and miscible with water.

Abstract: A method for preparing phosphoric acid from calcium phosphate ores, particularly ores highly contaminated with organic compounds, by decomposing the ore with sulphuric acid, wherein according to the invention the process of decomposition of calcium phosphate ores with sulphuric acid and circulating phosphoric acid is carried out in oxidizing conditions provided by a constant supply of ozone to the reaction slurry, preferably to the zone of commencing decomposition of the phosphate ores.

Abstract: A process for purification by multistage countercurrent extraction of wet-process phosphoric acid includes the steps of (a) preparing an aqueous phosphoric acid by decomposition of crude phosphates with sulfuric acid and prepurification thereof; (b) providing an organic solvent mixture consisting of one of (A) a water immiscible solvent and a fully water-miscible solvent or (B) a partially water-miscible solvent and a fully water-miscible solvent; (c) extracting water from the acid by contacting with the solvent mixture in a volumetric ratio of acid to solvent mixture of 1:1 to 1:10 at a temperature of 5 to 90° C.; (d) recovering the fully water-miscible solvent by distillation and washing; (e) recycling the fully water-miscible solvent to step (b) to provide a recycled solvent mixture; and (f) repeating steps (c), (d) and (e) with the recycled solvent mixture to provide a phosphoric acid having a preselected degree of purity.

Abstract: Modification of phosphoric acid manufacturing provides improved process waters: decontaminated water pH-adjusted to be only slightly acidic, scrubber process water, gypsum stack water, and a composite of the latter two waters. The composite water undergoes two-stage neutralization with clarification, eliminating precipitatable contaminants, in forming the pH-adjusted water, which in turn is useful in forming scrubber process water or gypsum stack water, as needed, Resulting gypsum stacks and rainfall surge ponds, having been made relatively fluoride-free through such processing modification, and preferably also having been lined, supersede previous gypsum stacks and acid gypsum ponds—whether lined or not.

Abstract: The present invention provides a basic method for producing high purity silica and ammonium fluoride from silicon tetrafluoride-containing gas, particularly the gas generated by acidulation. The basic method comprises recovering silicon tetrafluoride-containing gas from the acidulation of a fluorine-containing phosphorus source, separating liquid entrainment from the gas, converting the gas recovered to an ammonium fluosilicate solution, and ammoniating said ammonium fluosilicate solution to produce high purity silica and ammonium fluoride.

Abstract: Maximum throughput of a wet process phosphoric acid plant at a fixed recovery can be obtained by controlling the filter feed to give a desired specific gravity of the filtrate from the last washing of the gypsum cake. The filtrate from the last washing of the gypsum cake also is called the first pass filtrate. The specific gravity of this first pass filtrate provides an indication of the overall filter efficiency and the loss of water-soluble phosphoric acid to the gypsum waste stream. The specific gravity of the first pass filtrate is controlled by adjusting the rate at which product slurry from the attack tank is fed to the filter. This product slurry feed rate is affected by the mechanical performance of the filter and the filterability of the gypsum crystals, which, in turn, is affected by operating conditions in the attack tank. Therefore, the feed rates of phosphate rock, sulfuric acid, and water, are controlled to produce the desired attack tank operating conditions and to maintain attack tank level.

Abstract: Converting wet-process phosphoric acid operations, to minimize and nearly eliminate discharge of contaminants to the environment, by generation, use, and treatment of new and unique process waters. Fluorides and other contaminants soluble under acidic conditions are insolubilized, and substantially all phosphoric acid is recovered. Acid pond water from conventional wet-process phosphoric acid manufacturing is replaced by neutralized gypsum stack water having a pH closely matching that of the surroundings. Both air and ground water contamination are reduced to essentially negligible levels.

Abstract: A method for clarifying phosphoric acid by flocculation or coagulation of solids wherein an effective amount of a carboxylic-type polymer having a portion of sulfonic functionality is used as the clarification aid. Preferred polymers are high molecular weight acrylic acid/acrylamido methylpropyl sulfonic acid-type polymers.

Abstract: Generation, use, and treatment of new and unique process waters in or for wet-process phosphoric acid manufacturing to substantially eliminate discharge of contaminants to the environment. Acid pond water from conventional wet-process phosphoric acid manufacturing, contaminated with compositions containing fluorine, heavy metals, and radioactive elements such as radium-226, plus residual P.sub.2 O.sub.5, is superseded. Substantially all contaminants from the wet-process are insolubilized and removed, whereas P.sub.2 O.sub.5 normally lost is recovered. Decontaminated gypsum stack water with a mildly acidic pH results from stepwise raising of wastewater pH, with clarification, and subsequent re-acidification, to provide a decontaminated process water with slightly acidic pH adapted to match the pH of environmental ground water. The process is made more economical, while enhancing protection of surrounding air, soil, and water from contaminants.

Abstract: This invention provides a method for removing aluminum contamination from phosphoric acid during the acidulation of phosphate rock with sulfuric acid in the presence of recycled phosphoric acid. The method of this invention involves the addition of acid soluble silica to the acidulation slurry and calls for maintaining the molar ratio of non-fluosilicate fluoride (i.e. fluoride not complexed with silica) to aluminum in the liquid phase of the acidulation slurry between 2.5 and 5.0. These conditions favor the precipitation of aluminum as calcium tetrafluoaluminate dihydrate and enable the co-removal of this compound by filtration with by-product gypsum. This invention is particularily suitable for the processing of phosphate rocks with high iron and aluminum contents, such as the nonsedimentary phosphate rocks occurring in Sri Lanka.

Abstract: The invention aims at a process for preparing phosphated or nitrophosphated fertilizers through reaction of phosphate rock in aqueous pulp, with sulfuric and/or phosphoric acids, with addition, or not, of ammonia, so as to produce fertilizers of the types simple, double or triple superphosphates, nitrogen-bearing (or not) phosphated partially acidulated, and superphosphated ammoniated, the product being adequate for use as a fertilizer, either powdered or slurried.The invention allows for a more complete reaction due to the better contact between the liquid and solid reagents besides the complete utilization of the heat produced in the reaction as well as in the acid dilution in the aqueous medium, for the vaporization of the water present in the process.

Abstract: A method for improving gypsum slurry filtration in the production of wet process phosphoric acid wherein an effective amount of carboxylic-type polymer having a portion of sulfonic functionality is used as the filtration aid. Preferred polymers are high molecular weight polymers of acrylic acid and acrylamido methylpropyl sulfonic acid.

Abstract: A method for controlling the phosphoric acid product concentration in a continuous phosphoric acid recovery process comprising supplying a constant feed stream of phosphate ore to an attack tank wherein the phosphate ore is subjected to attack by sulfuric and phosphoric acids to produce a slurry comprising an aqueous phosphoric acid solution and calcium sulfate, filtering the slurry to form aqueous phosphoric acid and calcium sulfate filter cake, rinsing said filter cake with water, and adding said rinse water to the attack tank, calculating a first amount of water required to maintain a desired concentration of phosphoric acid in the slurry, said desired concentration calculated based on the concentration of phosphate ore in the feed stream and the filterability of the filter cake, determining the total actual amount of water added to the attack tank, and adjusting the amount of rinse water so that the amount of water added to the attack tank is sufficient to maintain the desired concentration of phosphoric

Abstract: A digested slurry from a wet process phosphoric acid production process is dewatered by gravity-assisted vacuum filtration using as a filtration aid an aqueous solution of a polymeric filtraton aid that has been subjected to high shear mixing to enhance the performance of the filtration aid and enhance the filtration.

Abstract: A method for clarifying phosphoric acid by flocculation or coagulation of solids wherein an effective amount of a polymer having a predominantly sulfonic functionality is used as the clarification aid. Preferred polymers are high molecular weight acrylamide/acrylamido methylpropyl sulfonic acid-type (AM/AMPSA) polymers which are predominantly AMPSA.

Abstract: High molecular weight copolymers of acrylamide which contain between 5-100 mole % of acrylic acid and have a molecular weight of at least 1,000,000 prevent scale adhering to surfaces in contact with digested phosphate rock and/or phosphoric acid produced from digestion.

Abstract: Disclosed is a process for treating a waste stream containing calcium sulfate by depositing said waste stream on a gypstack, collecting the leachate from the gypstack, and recovering the P.sub.2 O.sub.5 values therefrom. Also disclosed is apparatus comprising means for depositing a waste stream containing calcium sulfate on a gypstack, means for collecting the leachate from the gypstack, and means for recovering the P.sub.2 O.sub.5 values therefrom. Preferably, at least about 25% of the calcium sulfate is calcium sulfate hemihydrate.

Abstract: A wet process production of phosphoric acid in which phosphate rock is digested, whereby phosphoric acid is released and calcium sulfate crystals are formed, employs a polymeric crystal modifier in the digestion stage of the process to improve the separation of the raw phosphoric acid product from the calcium sulfate crystals and to increase the concentration of phosphoric acid in the raw phosphoric acid product.

Abstract: A method for defluorinating wet process phosphoric acid. Phosphatic waste clay from phosphate rock beneficiation is mixed with the wet process phosphoric acid. The mixture is heated for a time sufficient to remove fluorine from the acid as gaseous silicon tetrafluoride. Phosphate is liberated from the phosphatic waste clay and thus is recovered in the defluorinated wet process phosphoric acid.

Abstract: Disclosed is an improved process for purifying phosphoric acid where a calcium sulfate hemihydrate slurry is first filtered to produce a first filtrate and a filter cake which comprises calcium sulfate hemihydrate, the calcium sulfate hemihydrate filter cake is slurried to produce a slurry containing less than 2% by weight free sulfate ion, which is hydrated in a hydration tank to produce a calcium sulfate dihydrate slurry, and the calcium sulfate dihydrate slurry is filtered on a second filter to produce a second filtrate and a gypsum filter cake. The improvement comprises recycling the second filtrate to the second filter in an amount (1) sufficient to reduce the flow rate of the calcium dihydrate slurry from the hydration tank to the second filter so that the residence time of the slurry in the hydration tank is at least two hours and (2) at least sufficient to maintain liquid on the second filter. Also disclosed is an apparatus for performing this process.

Abstract: P.sub.2 O.sub.5 values occluded in the crystals which are precipitated during the hemihydrate process for manufacturing phosphoric acid are recovered by dissolving and recrystallizing the hemihydrate crystals as dihydrate crystals in an acidic environment having a P.sub.2 O.sub.5 concentration of from about 0.1% to about 10% and a free sulfate concentration in the range of about 0.1% to about 10%. Water is used to wash the dihydrate filter cake, and the filtrate from this wash is used to redissolve the hemihydrate crystals. The free sulfate values are preferably supplied to the dihydrate crystallizer as sulfuric acid.

Abstract: A process providing solubilization of phosphate rock by contacting the rock with sulfurous acid in the presence of an oxidizing agent selected from the group consisting of hydrogen peroxide and ozone. Use of sulfurous acid in combination with a substoichiometric amount of hydrogen peroxide significantly enhances the solubilization of phosphate rock.

Abstract: A process and apparatus for producing phosphoric acid by the recovery of P.sub.2 O.sub.5 from a phosphate ore is disclosed. A slurry of a phosphate ore in an aqueous phosphoric acid solution is formed in each of a plurality of reaction zones connected in series. Phosphate ore is introduced into the first reaction zone and phosphoric acid into the last reaction zone whereby the reaction of the phosphoric acid with the ore forms a slurry of coarse solids, fine solids and monocalcium phosphate in the phosphoric acid solution. A first process stream comprising coarse solids is removed from the first reaction zone and each of the other reaction zones and is transferred to the adjacent, successive reaction zone.

Abstract: A process for the removal of heavy metals from an acid phosphate containing, liquid medium in which process a precipitate containing heavy metals is formed and is subsequently separated and wherein at least one of the two additives (a) sulphate ions and (b) calcium ions is added to the phosphate-containing, liquid medium under such conditions that a calcium sulphate anhydride-containing precipitate is formed.

Abstract: Separation of gypsum from phosphoric acid liquor produced during the production of phosphoric acid from finely ground phosphate rock. These aids are characterized as containing sulfonate and acrylamide.

Abstract: A process for the production of highly concentrated phosphoric acid, comprises improvements in digesting phosphate rock with a mixed acid consisting essentially of sulfuric acid and phosphoric acid to obtain a slurry comprising phosphoric acid and hemihydrate (CaSO.sub.4.1/2H.sub.2 O), then filtering the slurry, taking out highly concentrated phosphoric acid as product acid and subsequently hydrating the hemihydrate to obtain gypsum (dihydrate: CaSO.sub.4.2H.sub.2 O).

Abstract: Crude phosphoric acid is made by subjecting crude phosphate ore containing sulfide to processing treatment with a mineral acid in a closed system comprised of a processing reactor, a filtering zone and an off-gas scrubbing zone. To this end, a soluble compound of a metal forming difficultly soluble sulfides in the respective acid medium is added either(A) during the processing operation the phosphate ore is subjected to or(B) during the scrubbing operation the off-gas is subjected toand the resulting sulfide precipitate is filtered off in case (A) together with further matter precipitated during the processing operation and, in case (B) separated from the scrubbing liquid.

Abstract: There is described a process which comprises adjusting on the one hand the flow rates of a circulating mixture relative to a base flow rate according to very specific specifications, and on the other hand so adjusting the reaction conditions in succeeding reaction zones as to obtain a production phosphoric acid with a P.sub.2 O.sub.5 concentration between 33 and 52%, and a H.sub.2 SO.sub.4 concentration between 0.25 and 2.5%, and calcium sulphate in the form of dihydrate, hemihydrate, anhydrite or a mixture of at least two said crystalline forms.

Abstract: A method is disclosed for increasing the fluosilicic acid (FSA) recovered from a wet process phosphoric acid manufacturing process. The filtrate obtained by washing a filter cake is pumped to a stripper and reacted with H.sub.2 SO.sub.4 to converting the dissolved FSA to gaseous SiF.sub.4. A defoamer is added to the acid-filtrate mixture to reduce the foam produced by the reaction and increase the amount of gaseous SiF.sub.4 recovered from the reaction. The gaseous SiF.sub.4 is recovered from the acid-filtrate reaction mixture and converted to FSA for commercial use.

Abstract: An improved process for extending the capabilities of an existing, conventional wet-process phosphoric acid production plant to more effectively utilize phosphate values contained in low purity phosphate rock which process comprises (1) adjustment of the maximum soluble sulfate level in phosphoric acid taken from, for example, the conventional wet-process acid facility prior to reacting same with such low purity phosphate rock, in combination therewith, and (2) control of the parameters of (a) ratio of attack acid to feed rock, (b) reaction temperature, and (c) reaction time. Said improved process effects selective dissolution of calcium and phosphate values from such rock without incurring unwanted and undesired high codissolution of congeneric aluminum and iron impurities therein.

Abstract: This disclosure involves a process for treating wet phospho-gypsum, a by-product from wet phosphoric acid manufacture, to remove fluorine values so as to make the sulfur values in the phospho-gypsum usable in making sulfuric acid in a contact sulfuric acid plant. The process involves drying the phospho-gypsum at 400.degree.-600.degree. C. to vaporize the fluorine values, the P.sub.2 O.sub.5 values and water and reacting the hot vapors with lime or limestone to remove the fluorine values as fluorspar. The P.sub.2 O.sub.5 values are subsequently condensed and used in a phosphoric acid plant. The dry phospho-gypsum is heated to 1200.degree.-1250.degree. C. under reducing conditions to produce SO.sub.2 gas and siliceous lime. The SO.sub.2 is then passed through a lime or limestone scrubber to eliminate any remaining fluorine values, dried and utilized in a contact sulfuric acid plant.

Abstract: Phosphoric acid is produced from dry phosphate ore, matrix by acidulation with sulfur trioxide in the presence of sulfuric acid catalyst to form polyphosphoric acid, treatment with sufficient water to convert the polyphosphoric acid to orthophosphoric acid and extraction with water or organic solvent such as a lower alcohol, particularly methanol or ethanol.

Abstract: The invention is a process for recovering phosphorus value from magnesium pyrophosphate containing filter media in the wet superphosphoric acid purification process. The invention comprises treating the filter cake with a salt to remove the adhering phosphoric acid without solubilizing magnesium acid pyrophosphate. The filter cake, after phosphoric acid removal, can be utilized as commercial or technical grade magnesium acid pyrophosphate.

Abstract: Wet-process phosphoric acid is made by subjecting a phosphate ore to processing treatment with a mineral acid resulting in the formation of a processed suspension. The formation of silicofluorides is obviated by adding, either to the phosphate ore or the processed suspension, a quantity of an aluminum compound soluble in phosphoric acid sufficent for the processed suspension to present an aluminum concentration of 0.3 to 1.0 wgt %, based on P.sub.2 O.sub.5.

Abstract: A process for the recovery of the uranium present in phosphoric acid produced by a wet process in (A) by means of a suitable solvent (L.sub.9), which is carried out after separation of the gypsum in (B) formed in the attack operation, and elimination of the solid materials which are still in suspension, characterized in that, in order to avoid the formation of dross in the course of the operation of extracting the uranium which is previously reduced in (D), the step of eliminating the solid materials which are still in suspension is effected by a final solid-liquid separation operation in (C) and/or in (E), prior to extraction of the uranium in (F), in the presence of an added fraction of gypsum (S.sub.22) and/or (S.sub.23) resulting from the production of H.sub.3 PO.sub.4.

Abstract: A method for removing organic materials from a wet process phosphoric acid obtained by treating an uncalcined phosphate rock with sulfuric acid. The wet process phosphoric acid is contacted with a reducing material having a standard single electrode potential of at most 1.42 V and then further contacted with active carbon.

Abstract: Alkali metal phosphates and HF can be produced from a substantially calcium-free fluoroaluminum phosphate precipitate (which also contains iron) made by the aging of wet process phosphoric acid containing iron, fluorine and aluminum, preferably phosphoric acid analyzing in the range of about 15%-45 weight percent P.sub.2 O.sub.5, 2-4% Al.sub.2 O.sub.3 and 1-2% fluorine. One process involves digestion of phosphate ore matrix in recycled phosphoric acid, filtration to remove the insoluble residue, precipitation and filtration to remove gypsum, and aging of the product acid to precipitate the aluminum impurity as a fluoroaluminum phosphate compound. The fluoroaluminum phosphate can be decomposed (as by heating at above 195.degree. C.) to produce HF and aluminum phosphate. The aluminum phosphate can be contacted with alkali metal hydroxide under conditions which produce an alkali metal phosphate.

Abstract: An improved process for stabilizing wet process phosphoric acid is described in which the acid is treated with pressurized carbon dioxide and then is aged so as to enhance the rate of post-precipitation.