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| Number | Title | Issue Date |
| 4491570 | Removal of arsenic from hydrogen fluoride Arsenic impurities are removed from anhydrous hydrogen fluoride by treating the hydrogen fluoride with elemental chlorine and anhydrous hydrogen chloride or a fluoride salt or both and then separating the purified anhydrous hydrogen fluoride, preferably b... | 01/01/1985 |
| 4479926 | Treatment of residual bottoms from fluorosulfuric acid regeneration A method for treating a waste stream from an alkylation process is disclosed, where the waste stream comprises a fluoride, sulfuric acid, and an acid soluble oil. The method comprises combusting the waste stream, scrubbing the combustion products to remov... | 10/30/1984 |
| 4477425 | Production of anhydrous hydrogen fluoride from low-grade metallic fluorides and sulfuric acid A novel method is provided for the production of anhydrous hydrofluoric acid from low-grade metallic fluorides using an intermediate aluminum fluoride compound. The method involves the reaction of low-grade metallic fluorides such as fluorspar with sulfur... | 10/16/1984 |
| 4444740 | Method for the recovery of fluorides from spent aluminum potlining and the production of an environmentally safe waste residue A method for recovery of fluoride values from spent potlining and fluoride containing insulating materials associated with the potlining is disclosed. Spent potlining and the insulating materials are reduced to a fine particle size and incinerated. The as... | 04/24/1984 |
| 4405575 | Method of defluorinating phosphates 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 ... | 09/20/1983 |
| 4394365 | Method for curtailing phosphorous impurity in the production of hydrogen fluoride In the generation of hydrogen fluoride gas for the production of AlF3 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 phosphoro... | 07/19/1983 |
| 4355017 | Aluminum electrolytic cell cathode waste recovery 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° C. and 1200° C.... | 10/19/1982 |
| 4325935 | Method and an installation for obtaining or recovering hydrofluoric acid 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° C. to 800° C., with an overall p... | 04/20/1982 |
| 4310501 | Process for producing hydrogen fluoride 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 ... | 01/12/1982 |
| 4309389 | Process for the recovery of hydrofluoric acid and depositable residues during treatment of niobium- and/or tantalum-containing raw materials 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 hydrofl... | 01/05/1982 |
| 4298586 | Recovery of hydrofluoric acid from fluosilicic acid 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 an... | 11/03/1981 |
| 4294816 | Process for producing hydrogen fluoride from fluorine containing materials by continuous pyrohydrolysis 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 ... | 10/13/1981 |
| 4255407 | Method for the regeneration of pickling acids 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 va... | 03/10/1981 |
| 4234555 | Removal of uranium from aqueous HF solutions 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, pe... | 11/18/1980 |
| 4233281 | Recovery of hydrogen fluoride from metallic fluoride salts 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 containin... | 11/11/1980 |
| 4213952 | Recovery of hydrofluoric acid from fluosilicic acid with high pH hydrolysis 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, th... | 07/22/1980 |
| 4213951 | Recovery of hydrofluoric acid from fluosilicic acid with high pH hydrolysis 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. Sodi... | 07/22/1980 |
| 4172879 | Ferric iron removal from aluminum fluoride solutions 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-su... | 10/30/1979 |
| 4166098 | Process for treating an acid waste liquid 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... | 08/28/1979 |
| 4160808 | Pyrohydrolysis process for spent aluminum reduction cell linings 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 ... | 07/10/1979 |
| 4160809 | Modified pyrohydrolysis process for spent aluminum reduction cell linings 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... | 07/10/1979 |
| 4158701 | Pyrohydrolysis system for processing fluorine-containing spent and waste materials 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 pyrohyd... | 06/19/1979 |
| 4152405 | Co-current absorber for recovering inorganic compounds from plant effluents 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 en... | 05/01/1979 |
| 4144158 | Process for manufacture of anhydrous hydrogen fluoride and finely divided silica from fluosilicic acid 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 fl... | 03/13/1979 |
| 4132765 | Recovery of fluoride values 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 ... | 01/02/1979 |
| 4113832 | Process for the utilization of waste materials from electrolytic aluminum reduction systems 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 spe... | 09/12/1978 |
| 4083941 | Purification of anhydrous hydrogen fluoride 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 ... | 04/11/1978 |
| 4067957 | Process for producing hydrogen fluoride from an aqueous hydrofluorosilicic acid solution 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 amm... | 01/10/1978 |
| 4065551 | Method of recovering fluorine from carbonaceous waste material 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° C t... | 12/27/1977 |
| 4059680 | Method of preparing fumed SiO2 Fluorosilicic acid solutions, which normally undergo decomposition when distilled, thereby creating unwanted forms of SiO2, are rendered stable during distillation by providing in the fluorosilicic acid solution an amount of HF which is at leas... | 11/22/1977 |
| 4056605 | Method for purification of hydrofluoric acid 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 e... | 11/01/1977 |
| 4033899 | Alkylation fluosulfonic-sulfuric acid catalyst recovery process with silica-alumina removal of fluoride compounds 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 conve... | 07/05/1977 |
| 4032621 | Preparation of hydrogen fluoride with low levels of arsenic, iron and sulfite 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 ... | 06/28/1977 |
| 4010241 | Process for the production of hydrogen fluoride, phosphoric anhydride, calcium polyphosphates and nitric acid 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 hydr... | 03/01/1977 |
| 4006066 | Method of and apparatus for the treatment of exhaust-gases in the electrolytic production of aluminum Hydrogen-fluoride-containing gases from the electrolytic production of aluminum are subjected to electrostatic precipitation to remove dust particles containing substances which are deleterious to aluminum production before the gases are treated in an exp... | 02/01/1977 |
| 3976447 | Removal of hydrogen fluoride from gaseous mixture by absorption on alkaline earth metal fluoride 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 meta... | 08/24/1976 |
| 3976759 | Process for removal of fluoride compounds from spent alkylation catalyst 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... | 08/24/1976 |
| 3969485 | Process for converting silicon-and-fluorine-containing waste gases into silicon dioxide and hydrogen fluoride 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 concent... | 07/13/1976 |
