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: In the generation of hydrogen fluoride gas for the production of AlF.sub.3 by the reaction of fluorspar with concentrated sulphuric acid a small amount of aluminium sulphate is introduced into the reactive mix to assist in the retention of phosphorous compounds in the solid residues of the reaction and thus reduce the phosphorous content of the gaseous HF. Aluminium sulphate may be added as alum or may be generated in situ in the sulphuric acid by addition of an alumina hydrate, preferably before the acid is brought into contact with fluorspar. The addition of a small amount of calcium carbonate to the fluorspar also improves retention of phosphorous compounds in the solid residues in some instances.

Abstract: Recovery of fluoride values from carbonaceous waste cathode materials is achieved by reacting the waste materials with oxygen, water, and sulfur dioxide at temperatures between about 600.degree. C. and 1200.degree. C.

Abstract: A method of obtaining or recovering hydrofluoric acid from metal fluorides and solutions containing such, e.g. pickling solutions. In this procedure heavy metal fluorides are brought into contact with water vapor at 200.degree. C. to 800.degree. C., with an overall pressure of about 1 bar keeping the vapor partial pressure in a sufficiently linear relationship with the temperature in this range at a minimum of 0.9 bar at 400.degree. C. and at a minimum of 0.5 bar at 600.degree. C., separating the solid reaction material from the gaseous phase while still hot and obtaining aqueous hydrofluoric acid from the latter by--preferably indirect--cooling.

Abstract: A method of recovering fluorine, e.g. as hydrogen fluoride, from wastes of aluminum electrolysis furnaces, chemisorbents, adsorbents or absorbents, etc. in which the fluorine-containing material is subjected to pyrohydrolysis in an expanded fluid bed and the HF-containing gas is subjected to condensation or scrubbing for the removal of the HF therefrom. According to the invention, the exhaust gases from the fluidized bed are cooled by direct contact with solids which can be circulated in a separate cycle and are themselves cooled in a cooler, e.g. by contact with gas which is to be fed to the expanded fluidized bed. The circulated solids thus allow recovery of the sensible heat of the gas without diluting it.

Abstract: Raw materials containing tantalum or niobium are treated to obtain aqueous solutions containing fluoroacid complexes of niobium or tantalum. These solutions are decomposed by pyrolysis and calcined to obtain pure oxides of niobium or tantalum. The hydrofluoric acid separated during pyrohydrolysis is recovered and reused. A niobium or tantalum-free raffinate solution obtained, on extraction, with the above aqueous solutions contains dissolved metalloids which are recovered as oxides which are deposable waste products.

Abstract: Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium sulfate to form sodium fluosilicate. The sodium fluosilicate is reacted with a sodium-containing compound to form an alkaline aqueous slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the alkaline aqueous slurry leaving an aqueous solution of sodium fluoride. Sodium fluoride is recovered from the aqueous solution and reacted with sulfuric acid to produce hydrogen fluoride.

Abstract: A process for extracting hydrogen fluoride from fluorine containing materials includes countercurrently contacting the materials with steam having a plane of rotation relatively perpendicular to the direction of flow of the material. An apparatus for the extraction of hydrogen fluoride from fluorine containing materials includes a rotary kiln having a first zone wherein a steam-air mixture countercurrently contacts the materials in an oxidation step, a second zone wherein an oxygen containing gas is tangentially injected into the kiln to provide complete combustion of carbon containing materials, a third zone wherein a steam stream countercurrently contacts the materials in a reducing step and means for providing a plane of rotation to the steam which is relatively perpendicular to the direction of flow of the material.

Abstract: A method for the regeneration of spent pickling acids. Said acid is mixed with such a minor quantity of a stronger acid that the losses of said stronger acid are compensated. The mixture obtained is stripped, whereby the weaker acids are vaporized. The vapor phase containing the weaker acids is passed to a condenser. The condensate obtained forms the regenerated pickling acid. The spent pickling acid can also be passed directly to an evaporator in which a solution containing a stronger acid is circulated. The vapor from the evaporator is passed to an absorption column and thereafter to a condenser, the regenerated acid being formed of the condensate from said condenser.

Abstract: This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separting the solution from the settled particulates. The CaF.sub.2 is selected to have a nitrogen surface area in a selected range and is employed in an amount providing a calcium fluoride/uranium weight ratio in a selected range. As applied to dilute HF solutions containing 120 ppm uranium, the method removes at least 92% of the uranium, without introducing contaminants to the product solution.

Abstract: Anhydrous hydrogen fluoride of high purity can be recovered from metallic fluoride salts containing phosphate values by digesting the metallic salts in an aqueous solution in a humid atmosphere at a sufficiently high temperature to release a gas containing hydrogen fluoride and negligible amount of P.sub.2 O.sub.5. The released gas is rectified in a rectification operation which includes a rectification zone in which the rectification occurs in the presence of sulfuric acid.

Abstract: Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium hydroxide to form a first slurry having a pH of from about 11 to about 14, the first slurry containing sodium metasilicate and precipitated sodium fluoride. Sodium fluoride is recovered from the first slurry leaving a first solution which is reacted with sodium fluosilicate or fluosilicic acid or both to form a second slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the second slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the second slurry leaving a second solution of sodium fluoride. Sodium fluoride is recovered from the second solution. Recovered sodium fluoride is reacted with sulfuric acid to produce hydrogen fluoride.

Abstract: Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium sulfate to form sodium fluosilicate. The sodium fluosilicate is reacted with sodium hydroxide to form a first slurry having a pH of from about 11 to about 14, the first slurry containing sodium metasilicate and precipitated sodium fluoride. Sodium fluoride is recovered from the first slurry leaving a first solution which is reacted with sodium fluosilicate or fluosilicic acid or both to form a second slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the second slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the second slurry leaving a second solution of sodium fluoride. Sodium fluoride is recovered from the second solution. Recovered sodium fluoride is reacted with sulfuric acid to produce hydrogen fluoride.

Abstract: A process for the selective separation of ferric iron from an aluminum fluoride aqueous solution containing ferric iron is effected by contacting said solution with an organic extractant phase consisting essentially of a mixture of a mono (higher alkyl-substituted phenyl) phosphoric acid and a di(higher alkyl-substituted phenyl) phosphoric acid dissolved in an inert diluent to thereby transfer the ferric iron to said organic extractant phase. The efficiency of the process is further improved by adjusting the aluminum fluoride aqueous feed solution to a temperature in the range of about 140.degree. F. to about 175.degree. F. prior to contacting it with the organic extractant phase, maintaining the temperature within this range throughout the ferric iron extraction stage or stages, then heating the resulting iron-depleted aqueous raffinate to a temperature higher than 195.degree. F., and then crystallizing aluminum fluoride trihydrate out of the raffinate at this higher temperature.

Abstract: A process for treating an acid waste liquid containing Fe ions which has been used for acid washing of metallic materials or articles, comprising the first stage where an organic solvent (A) is added to the acid waste liquid to extract Fe ions, the second stage where an acid is added to the resulting acid waste liquid to convert chemical species of remaining metal salts and increase the hydrogen ion concentration followed by addition of an organic solvent (B) to recover the mineral acid of concern by extraction, the third stage where an organic solvent (C) is added to the resulting acid waste liquid to extract and recover other required mineral acids, and regenerating each of the organic solvents (A), (B) and (C) in respective stages.

Abstract: An improved process is provided for the recovery of HF in increased yield from spent aluminum reduction cell linings. The spent linings are pyrohydrolyzed in a fluidized bed reactor and the generated Na-containing vapors and gases are then contacted with a relatively finely divided source of Al.sub.2 O.sub.3. Contacting is preferably accomplished in the close vicinity of the fluidized bed to obtain extended reaction between the Al.sub.2 O.sub.3 source and the vapors. This extended reaction allows conversion of the Na-containing compounds, such as NaF and Na.sub.2 O to HF and an Na.sub.2 OxAl.sub.2 O.sub.3 compound.

Abstract: Fluoridic spent and waste materials, such as are generated in electrolytic aluminum reduction systems, are pyrohydrolyzed in a fluidized bed reactor. For fluidization of these materials, as well as for the combustion of carbon present in the materials, an O.sub.2 -containing gas stream, containing at least about 90% by volume O.sub.2, is employed. This results in the generation of an HF-containing offgas of significantly increased HF level, which can be employed for the manufacture of an AlF.sub.3 product of at least about 85% by weight AlF.sub.3 content from hydrated alumina. The offgas having the increased HF content can also be employed for the production of highly concentrated HF acid with significantly lower energy requirement needed for concentration than in conventional systems.

Abstract: A pyrohydrolysis system is provided for the recovery of valuable components from waste and spent materials generated in electrolytic aluminum reduction facilities. The pyrohydrolysis system employs a dense phase fluidized bed reaction zone for the pyrohydrolysis of coarse feed, a dilute phase fluidized reaction zone for pyrohydrolyzing fine feed, this zone being superimposed and interconnected with the dense phase zone. The offgases, after removal of the solids, are contacted in a dilute phase fluidized zone, with a source of Al.sub.2 O.sub.3 to remove residual Na values and to produce Na-free HF. The solids from the first dilute zone, having a desired high Na:Al atom ratio, can be combined with the product clinker from the dense bed zone. The offgas, containing the source of Al.sub.2 O.sub.3, is subjected to solids separation, the solids-free and Na-free HF is utilized, while the solids of low Na:Al mole ratio are recycled to the residual Na conversion step.

Abstract: Co-current absorber for recovering inorganic compounds from plant effluents, particularly useful for recovery of fluorine values as low phosphorus fluosilicic acid from phosphate plant effluents. Improved co-current absorber utilizing multiple cyclonic entrainment separators, co-current flow and renewed droplet surfaces.

Abstract: An improved process is described for converting aqueous fluosilicic acid waste product into anhydrous hydrogen fluoride and finely divided silica in which aqueous fluosilicic acid is pyrolyzed to produce silica and a dilute aqueous solution of hydrogen fluoride and fluosilic acid. The resulting dilute solution is subjected to electrodialysis, thereby obtaining a hydrogen fluoride concentration greater than that which characterizes the boiling point ridge which divides the phase diagram of the system hydrogen fluoride/fluosilicic acid/water, i.e. HF/H.sub.2 SiF.sub.6 /H.sub.2 O, into two regions. Anhydrous hydrogen fluoride is recovered from the resulting composition by distillation.

Abstract: The fluoride values of fluorapatite ores can be recovered by using reactive metal compounds, e.g., the sulfates, phosphates or hydroxides of aluminum, iron, titanium, zirconium, antimony or chromium, to tie up the fluorides during acid attack on the ores and thus minimize the formation of fluosilicic acid. The soluble metal fluoride salts formed can subsequently be separated and treated with acid to recover hydrogen fluoride.

Abstract: A fully integrated process is provided for the recovery of valuable components from waste materials generated in electrolytic aluminum reduction systems. The waste materials, such as spent pot linings, channel and trench cleanings, floor sweepings and spent alumina from offgas purifying dry scrubbers, are combined, then pyrohydrolyzed at elevated temperature. Fluoridic values, such as NaF and HF can be recovered from the offgas generated by pyrohydrolysis, while alumina and Na.sub.2 O values, or if desired, sodium aluminate, is reclaimed from the solid residue of pyrohydrolysis.The fluoridic values from the pyrohydrolysis offgas can be used for the manufacture of both electrolytes for aluminum reduction cells and also for the production of anhydrous HF. The alumina from the pyrohydrolysis residue can be reclaimed by a Bayer process-type leach with a caustic solution and the recovered high purity alumina utilized, for example, as reduction cell feed and/or for scrubbing reduction cell offgases.

Abstract: A process for preparing very high purity anhydrous hydrogen fluoride by contacting anhydrous hydrogen fluoride with at least 2.3% by weight of persulfuric acid based on the anhydrous hydrogen fluoride or at least 0.7% by weight of hydrogen peroxide based on the anhydrous hydrogen fluoride at ambient temperature and either at least 0.6% by weight of methanol based on the anhydrous hydrogen fluoride or at least one mole of sulfuric acid per mole of hydrogen peroxide at a temperature of from 0.degree. to 75.degree. C and distilling the resulting mixture to recover very high purity anhydrous hydrogen fluoride.

Abstract: Potassium fluoride and silica are reacted with an aqueous solution of hydrofluorosilicic acid. The resulting potassium fluorosilicate is recovered. The potassium fluorosilicate may be further reacted with ammonia in water to form an aqueous mixture of ammonium fluoride and potassium fluoride. The ammonium fluoride is then heated in aqueous solution in the presence of excess potassium fluoride to release ammonia and to form potassium bifluoride. The potassium bifluoride is recovered from solution substantially free from ammonia and heated to release hydrogen fluoride. Alternatively, the recovered potassium bifluoride may be reacted with sodium fluoride to produce sodium bifluoride. The sodium bifluoride is then heated to release hydrogen fluoride.

Abstract: Particles of solid carbonaceous waste material which contain fluorine are suspended in a stream of gas consisting of a mixture of steam and air to establish a fluidized bed in a retort. The particles are heated to a temperature of not less than 1000.degree. C to cause pyrohydrolysis and the recovery of fluorine as gaseous hydrogen fluoride at a very efficient rate.

Abstract: Fluorosilicic acid solutions, which normally undergo decomposition when distilled, thereby creating unwanted forms of SiO.sub.2, are rendered stable during distillation by providing in the fluorosilicic acid solution an amount of HF which is at least about 10 parts of HF per 36 parts of H.sub.2 SiF.sub.6 and an amount of H.sub.2 O which is at least about 54 parts of H.sub.2 O per 36 parts of H.sub.2 SiF.sub.6. The mixture is distilled to remove any excess H.sub.2 O and excess HF that is present, without encountering formation of SiO.sub.2, until an azeotropic solution containing about 36% H.sub.2 SiF.sub.6, about 10% HF and about 54% H.sub.2 O is reached. The ternary azeotrope, being of constant quality and concentration, is more suitable for use in various processes, such as processes for making fumed SiO.sub.2, than H.sub.2 SiF.sub.6 solutions which are not of constant quality or concentration.

Abstract: A method for purification of hydrofluoric acid from silicofluoric acid and/or sulphuric acid which comprises contacting a mixture of said acids with an anion-exchange resin in the fluoride form. As a result, a purified hydrofluoric acid is obtained. The exhausted anion-exchange resin is treated with a regenerating solution which comprises an aqueous solution of ammonium fluoride with a concentration within the range of from 2 to 10% by weight and having a pH value ranging from 6 to 9.The method according to the present invention is technologically simple; it enables the use of tightly sealed and safe equipment; requires minimal operation costs and eliminates the formation of production wastes.

Abstract: A process for removal of fluoride compounds from spent alkylation catalyst containing fluorosulfonic acid and sulfuric acid wherein said spent catalyst is hydrolyzed in the presence of water, at subatmospheric pressure in a vacuum digestion zone for conversion of a major portion of fluorosulfonic acid to hydrogen fluoride, wherein said hydrogen fluoride is removed from the vacuum digestion zone as a vapor, and wherein the remaining sulfuric acid rich liquid fraction of the spent catalyst is treated with silica-alumina cracking catalyst for removal of most of the remaining residual fluoride compounds for providing a sulfuric acid effluent substantially free of fluoride compounds. The hydrogen fluoride recovered is reacted with sulfur trioxide to form fresh fluorosulfonic acid which is combined with sulfuric acid to provide fresh alkylation catalyst.

Abstract: A process for preparing pure anhydrous hydrogen fluoride with decreased levels of arsenic, iron and sulfite by treating anhydrous hydrogen fluoride sequentially with an oxidizing agent, and then a heavy metal free reducing agent, distilling the resulting mixture and recovering the pure hydrogen fluoride.

Abstract: A process for the production of hydrogen fluoride, phosphoric anhydride, calcium polyphosphates and nitric acid, is disclosed, characterized in that natural phosphate is heated by a plasma stream of working gas in the presence of water vapors to form hydrogen fluoride which is recovered as a commercial product. Then the thus defluorinated phosphate is further heated by an air plasma stream having a bulk temperature of at least 3,500.degree. K. and containing nitrogen oxides. Under such conditions, the defluorinated phosphate decomposes to form phosphoric anhydride and calcium oxide.The gas stream carrying the phosphoric anhydride, the calcium oxide and the nitrogen oxides is cooled down to yield, as commercial products, either phosphoric anhydride and nitric acid, or calcium polyphosphates containing up to 70% P.sub.2 O.sub.5 and nitric acid, or else all of the three products, depending on the cooling conditions.

Abstract: A process for removal of fluoride compounds from spent alkylation catalyst containing fluorosulfonic acid and sulfuric acid wherein hydrogen fluoride and fluorosulfonic acid, in the presence of water, are removed by vacuum distillation following which the remaining sulfuric acid rich fraction of the spent catalyst is reacted with a silica containing material to convert most of the remaining residual hydrogen fluoride to silicon fluoride which is volatilized from the mixture to thereby provide a sulfuric acid effluent free of substantial amounts of fluoride compounds. The hydrogen fluoride recovered is reacted with sulfur trioxide to form fresh fluorosulfonic acid which is combined with sulfuric acid to provide fresh alkylation catalyst.

Abstract: A gaseous mixture containing up to 20% of hydrogen fluoride and other gases inert to alkaline earth metal fluorides is passed in contact with particulate anhydrous alkaline earth metal fluoride prepared by the fluorination of anhydrous alkaline earth metal chloride in the absence of water. After the anhydrous alkaline earth metal fluoride has taken up the desired amount of hydrogen fluoride, up to its absorption capacity, the hydrogen fluoride is removed therefrom, e.g. by heat regeneration, and the alkaline earth metal fluoride is reused to absorb additional hydrogen fluoride from said gaseous mixtures.

Abstract: A process is provided for converting silicon and fluorine-containing waste gases into silicon dioxide and hydrogen fluoride, absorbing the waste gases in water to form hydrofluosilicic acid, decomposing the hydrofluosilicic acid in the presence of concentrated sulfuric acid to form silicon tetrafluoride and hydrogen fluoride, converting the silicon tetrafluoride in the vapor phase to silica and hydrogen fluoride, and recovering the hydrogen fluoride.