Abstract: Process of acid attack with sulphuric acid of a phosphate source comprising calcium or not comprising calcium for a predetermined time period ranging from 20 to 180 minutes in the conditions wherein the molar ratio of sulphate from the sulphuric acid and possibly from the phosphate source to the calcium present in the phosphate source ranges from 0.6 to 0.8, and the content in P2O5 in the attack tank is of less than 6%.

Abstract: The invention relates to a process for the production of high purity phosphoric acid which has a very low content in antimony, and is suitable for food, pharmaceutical, or electronic industry.

Abstract: The invention relates to a process for the production of high purity phosphoric acid which has a very low content in antimony, and is suitable for food, pharmaceutical, or electronic industry.

Abstract: The invention concerns a method for producing phosphoric acid, which consists in: at least an attack of phosphate ore with an attacking liquid containing soluble phosphate ions, forming of an attacking product, separating in the attacking product between an insoluble solid phase containing impurities and a liquid phase having soluble phosphate ions and calcium ions, introducing in the separated liquid phase an acid stronger than phosphoric acid and which forms, with said calcium ions, a soluble calcium salt, and isolating a solution of said calcium salt, not contaminated by the impurities, thereby obtaining a phosphoric acid solution.

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%.

Abstract: The invention concerns a method for producing phosphoric acid, which consists in: at least an attack of phosphate ore with an attacking liquid containing soluble phosphate ions, forming of an attacking product, separating in the attacking product between an insoluble solid phase containing impurities and a liquid phase having soluble phosphate ions and calcium ions, introducing in the separated liquid phase an acid stronger than phosphoric acid and which forms, with said calcium ions, a soluble calcium salt, and isolating a solution of said calcium salt, not contaminated by the impurities, thereby obtaining a phosphoric acid solution.

Abstract: Phosphoric acid, essentially free from impurities, is prepared by reacting aqueous hydrofluoric acid with phosphate in particles of calcium bearing phosphate rock to form a calcium fluoride pseudomorph solid from which filter-grade phosphoric acid is separated. By reacting the pseudomorph solid with sulfuric acid and thermally treating the reaction product, the HF can be liberated and recycled back to the reaction step of the process. All of the impurities from the phosphate rock are contained in the resulting CaSO4.

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: Fluosilicic acid is reacted with phosphate rock in order to produce wet process phosphoric acid and calcium fluoride which is later reacted with sulfuric acid to produce hydrogen fluoride and calcium sulfate. The hydrogen fluoride is then stripped from the phosphoric acid and recovered as either anhydrous hydrogen fluoride or concentrated hydrofluoric acid or reacted with aluminum trihydrate to produce aluminum fluoride; with sodium carbonate to produce sodium fluoride/bifluoride; or with ammonia to produce ammonium fluoride/bifluoride.

Abstract: Fluosilicic acid is reacted with phosphate rock in order to produce wet process phosphoric acid and calcium fluoride which is later reacted with sulfuric acid to produce hydrogen fluoride and calcium sulfate. The hydrogen fluoride is then stripped from the phosphoric acid and recovered as either anhydrous hydrogen fluoride or concentrated hydrofluoric acid or reacted with aluminum trihydrate to produce aluminum fluoride; with sodium carbonate to produce sodium fluoride/bifluoride; or with ammonia to produce ammonium fluoride/bifluoride.

Abstract: A method and an installation for producing granulated triple superphosphate wherein a premixer for phosphate and a phosphoric acid solution includes unclogging means comprising in combination a flexible axial sleeve of non-vulcanized elastomer for injecting phosphate together with at least one sprayer for spraying the phosphoric acid solution and acting level with the free bottom end of the sleeve. The invention is applicable to the chemical industry.

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 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: Fluosilicic acid is reacted with phosphate rock in order to produce wet process phosphoric acid and calcium fluoride which is later reacted with sulfuric acid to produce hydrogen fluoride and calcium sulfate. The hydrogen fluoride is then stripped from the phosphoric acid and recovered as either anhydrous hydrogen fluoride or concentrated hydrofluoric acid or reacted aluminum trihydrate to produce aluminum fluoride; with sodium carbonate to produce sodium fluoride/bifluoride; or with ammonia to produce ammonium fluoride/bifluoride.

Abstract: Alkali metal phosphate solutions having a fluorine content of less than 20 ppm, based on P.sub.2 O.sub.5, are prepared by first digesting crude phosphate using sulfuric acid, and separating the calcium sulfate from the crude phosphoric acid. An alkali metal compound is then added to the crude phosphoric acid, and the precipitated solid is filtered off. The prepurified crude phosphoric acid is neutralized to a pH of at least 7, and the solid produced during this operation is separated off. The resultant alkali metal phosphate solutions having a P.sub.2 O.sub.5 content of from 10 to 30% by weight are adjusted to a pH of between 4.8 and 6.0 using phosphoric acid. The solutions are heated to from 60.degree. to 120.degree. C., and from 1 to 6% by weight, based on the weight of the solution, of an alkaline earth metal oxygen compound are added to the alkali metal phosphate solutions with stirring.

Abstract: A process for producing high-analysis dicalcium phosphate containing phosphatic fertilizers and by-product calcium nitrate. It comprises reacting phosphate rock with nitric acid, followed by pyrolysis of the resulting acidulate to effect liberation of approximately one-half of the initially consumed nitric acid. Recycling of this liberated nitric acid allows production of available phosphate with approximately one-half the acid equivalents normally consumed during sulfuric acid processing. The calcium nitrate in the resulting pyrolyzate is separated from the phosphatic constituent by dissolution in water followed by filtration. Depending upon the initial HNO.sub.3 :CaO acidulation ratio, the available phosphate content of the resulting solid phosphatic fertilizers is high enough (48% P.sub.2 O.sub.5) to allow their use either for bulk blending with nitrogen and potash salts to produce complete grade fertilizers or for direct application as a phosphate nutrient.

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: The present process stabilizes merchant acid from bottoms solutions against post-precipitation by heating the acid to a temperature of at least about 180.degree. F. for about 12 to about 48 hours. The stabilized acid product exhibits less than about 1 wt % solids precipitation after even 14 days of standing at about 70.degree. F.

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: 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: 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: The present invention is depicting a chemical separation of phorphorus ore. Phosphorus ore, especially calcareous and clacareous-sillicious phosphorus ore can be effectively converted into several products through chemical separation, which consists of two stages, namely ore pulp reaction and solution regeneration. In the first stage, phosphorus ore is disolved by mixed ammonium salts solvent, but the valence minerals, such as fluoride apatite and quartz don't take part in the reaction and retain their solid state. Thus phosphorus concentrate can be obtained through the separation, the by-products such as the filtrate and gases can be utilized in the solution regeneration. After ammoniation, sulfurization, carbonization and alkalization of the filtrate, the Ca.sup.2+, Mg.sup.2+, Fe.sup.3+, Al.sup.2+, M.sup.2+ ions in it will gradually come out and turn into products, the regenerated solution obtained can be used again and again, thus forming a complete enclosed circulation process.

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: 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: 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: 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: 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: Phosphatic clay dispersions are modified by dispersing the phosphate matrix containing the clay in a dilute solution of selected acids prior to screening, sizing and other beneficiation operations.

Abstract: Phosphate rock, containing appreciable quantities of organic impurities, is thermally treated under controlled conditions to fully utilize the fuel values of the organic matter contained therein. This process is beneficial for treating deposits of unaltered Idaho rock containing both higher grade phosphate rock and lower grade phosphatic shales and recovering therefrom substantially all the phosphate values as a rock product rendered more acceptable for acidulation to wet-process phosphoric acid.

Abstract: A process for removing impurities from phosphoric acid, especially concentrated wet process phosphoric acid, comprises filtering phosphoric acid through a filter cake (e.g., diatomite) on a porous member at a temperature in the range of about 57.degree. C. to about 77.degree. C. The filter cake retains some phosphate values. A major portion of the phosphate values retained by the filter cake can be introduced into the phosphoric acid manufacturing process, as by slurrying the filter cake in water, separating the aqueous phase from the solid phase, and introducing the aqueous phase to a wet process phosphoric acid process (e.g., as a "gypsum" filter wash).

Abstract: The present invention provides a continuous method for preparing phosphoric acid and calcium sulphate by reacting calcium phosphate with a mixture of sulphuric acid and phosphoric acid. Our method uses at least three successive crystallization steps: a first step of reacting the phosphate with the mixture of phosphoric and sulphuric acids and forming a-hemihydrate calcium sulphate, a second step of recrystallizing the a-hemihydrate into dihydrate and a third step of transforming the dehydrated calcium sulfate into a hemihydrate or anhydrite II or a mixture of the two. Where desired recycling of the products from the above steps can be used for increasing the efficiency of the above method.

Abstract: There is disclosed a method of producing water-based phosphate matrix slurries wherein the as-mined phosphate matrix is dried prior to the formation of the slurry. Drying the matrix decreases the viscosity of the slurry and improves the clay consolidation characteristics of the by-product slimes produced during the phosphate slurry beneficiation process steps.

Abstract: Phosphoric acid is produced, with concomitant recovery of solids comprising compounds of fluorine and silica, by (i) acidulating a first amount of phosphate ore with a strong acid to produce a first phosphoric acid slurry, (ii) filtering said first slurry to separate the liquid phosphoric acid content therefrom, (iii) concentrating a fraction of the phosphoric acid thus separated, (iv) recovering same, and (v) condensing the evolved vapors of concentration with a liquid absorbent to produce a solution of fluosilicic acid, (vi) acidulating a second amount of phosphate ore with said solution of fluosilicic acid together with a fraction of said first slurry, or together with a fraction of the phosphoric acid separated in the step (ii), to produce a second phosphoric acid slurry, (vii) filtering said second slurry to separate both the liquid phosphoric acid content and a solids fraction therefrom, said solids fraction comprising fluorine and silica compounds, (viiia) recycling the phosphoric acid thus separated f

Abstract: There is disclosed an improved process of beneficiating phosphate-containing ores. The process comprises stabilizing a hydrocarbon oil, normally used in a conditioning step to improve separation of the ore from the solid contaminants in a flotation step, upstream of the conditioning step. The oil is stabilized by conducting it to a pre-stabilization step wherein it is mixed with at least one fatty acid or saponified fatty acid and water to form a stable, homogeneous emulsion. The emulsion is then transferred to the conditioning step wherein it is mixed with the phosphate-containing ore.

Abstract: A continuous process for the production of a granulated fertilizer wherein comminuted phosphate rock, phosphoric acid and water are introduced into a pre-reactor where they are heated. The mixture is continuously withdrawn and transferred to a digester where heating is continued resulting in formation of a slurry. The slurry is continuously withdrawn and is split into two streams, one of which is recycled to either the pre-reactor or to the digester while the other stream is delivered to a granulator where it is mixed with other fertilizer ingredients and dried to form the granulated fertilizer.

Abstract: A process for the recovery of phosphate values from a phosphate ore, wherein the ore is leached with a mixture comprising water, sulphur dioxide and an organic carbonyl compound; the leach liquor containing dissolved phosphate values and calcium hydroxysulphonate is separated from any gangue and other insoluble material; and the leach liquor is treated to recover therefrom a phosphate-rich product and at least part of the sulphur dioxide and the carbonyl compound; characterized in that the leaching is carried out under conditions such that substantially no calcium hydroxysulphonate is precipitated at the leaching stage.

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 rail road 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 present invention relates to a method for beneficiation of phosphate rock by a thermal treatment, wherein an appreciable increase in P.sub.2 O.sub.5 and decrease in cadmium contents in the calcined product are achieved. According to the invention, the phosphate rock is contacted with hot gases possessing a temperature in the range of between 700.degree. C. to 1600.degree. C. for a period of below 60 seconds and subsequently the fines are removed by a conventional classification method thus obtaining an up-graded phosphate product with a relatively low cadmium content. The up-graded phosphate product is also characterized by a relatively low sulfide content as well as low organic matter, which are very advantageous in the phosphoric acid manufacture therefrom. One of the advantages of the method is the almost complete recovery of the P.sub.2 O.sub.5 present in the phosphate rock since no slaking for calcium oxide removal is utilized.

Abstract: The invention relates to the chemical removal of phosphorus compounds from waste water, this waste water being treated with one or more metal compounds, without any problems presenting themselves as regards the separation of the metal phosphate compounds. To achieve this, the waste water is treated with the metal compound in a fluidized bed of metal phosphate particles.The invention also relates to a process for the purification of waste water in which the effluent from a biological purification is subjected to the above-mentioned method for the removal of phosphorus.

Abstract: Substantially calcium-free fluoroaluminum phosphate precipitate (which also contains iron) can be produced 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 about 195.degree. C.) to produce HF and aluminum phosphate.

Abstract: A method and system for conducting wet grinding of mined phosphate rock before utilizing the same for the production of phosphoric acid by the wet process method, the method comprising the steps of: (1) wet grinding the phosphate rock in a medium of fresh water at a first stage so as to form a fresh water slurry comprising ground rock and fresh water, (2) sending the fresh water slurry from the first stage to a second stage, (3) dewatering the fresh water slurry at the second stage so as to recover most of the fresh water from the slurry and leave substantially only wet ground rock, (4) recycling the fresh water recovered at the second stage back to the first stage for use in further wet grinding, (5) sending the ground rock from the second stage to a third stage, (6) refluidizing the ground rock at the third stage with acidic pond water so as to form a pond water slurry comprising ground rock and pond water, and (7) thereafter passing the pond water slurry on to a reactor for standard processing so as to pro

Abstract: Phosphoric acid is produced by the wet process from phosphate rock containing fluochlorapatite. The rock is ground in a crusher (10) to a size such that from about 50% to about 90% by weight will be passed by a -200 mesh U.S.S. sieve before being passed into a digestor (14) where it is mixed with sulfuric acid and recycled phosphoric acid to form a slurry. A suitable reductant such as sulphur dioxide is added to the slurry to maintain the oxidation-reduction potential in the range from about +150 mv to about +750 mv. The gypsum by-products are then removed from the slurry at filter (16) and a portion of the acid is recycled to digestor (14). The remaining acid is either concentrated and further processed to make fertilizers or is further processed via path (20) to remove aluminum and/or iron impurities. Select amounts of fluoride and sodium containing compounds are added to the acid in a stirred reactor (30) to cause precipitation of aluminum, principally as Na.sub.2 AlF.sub.5.

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: A rapid, low temperature process for solubilizing phosphate rocks having high content of foreign matter or a low phosphorus content to obtain: (a) a slow release fertilizer of the NP type; (b) phosphoric acid of high concentration plus MAP; and (c) DAP.

Abstract: A process for producing fertilizer-grade phosphoric acid is disclosed. In the process, a rock slurry is produced from a predetermined quantity of phosphate rock and a predetermined quantity of pond water neutralized with ammonia. A predetermined rate of sulfuric acid is added to the rock slurry to produce a reaction mixture. The improvement comprises maintaining an excess of sulfate ion in the reaction mixture.

Abstract: Solidification of colloidal argillaceous matter in essentially non-settling, aqueous slime media into a solid stable matrix is accomplished by mixing such slime with a hydratable calcium sulfate and hydrating to form an interlocking strength bearing matrix. The method is particularly useful for coalescing phosphatic clay slimes with hydratable calcium sulfate prepared from the co-produced waste phosphogypsum.

Abstract: Process and Apparatus for preparing O--X--O and O--X--X (i.e., zero nitrogen) suspension fertilizers wherein phosphate rock is acidulated with merchant-grade wet-process orthophosphoric acid. The instant invention requires only a minimal amount of relatively inexpensive equipment. The process comprises a first-charging step wherein a reactor vessel is partially filled with water of formulation, phosphoric acid, and phosphate rock. The resulting mixture is subjected to a digestion step for a predetermined period of time to effect reaction of the acid and phosphate rock added thereto. Said digestion step is subsequently followed by a second-charging step wherein predetermined amounts of potassium chloride and/or suspending agent are added to said reactor vessel.