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| Number | Title | Issue Date |
| 7179438 | Methods and apparatus for recovering gypsum and magnesium hydroxide The present invention provides methods and apparatus for treating flue gas containing sulfur dioxide using a scrubber, and more particularly relates to recovering gypsum and magnesium hydroxide products from the scrubber blowdown. The gypsum and magnesium hydroxide ... | 02/20/2007 |
| 7118718 | Gypsum decontamination process A process for reducing a level of radionuclei in a phosphogypsum material having a radioactive contaminant is provided, wherein the process includes the steps of: (a) mixing the phosphogypsum material with an acid decontamination solution to form a mixture; (b) sepa... | 10/10/2006 |
| 7057010 | Process for the continuous drying of polymers containing N or amino, ammonium or spirobicyclic ammonium groups Process for the drying of polymers containing N or amino, ammonium or spirobicyclic ammonium groups, comprising cationic N-containing groups, and suitable counterions, in which the gelled and washed polymers obtained by polymerization, crosslinkage and optionally al... | 06/06/2006 |
| 6827914 | Method, apparatus and use of chelating agents for the purification of calcium sulphate A chemical process for the purification of CaSO4 utilizes the ability of an aqueous solution of a chelating agent to selectively dissolve CaSO4 in that the initial extraction can be carried out at certain pH and CaSO4 can be recovere... | 12/07/2004 |
| 6790430 | Hydrogen production from carbonaceous material Hydrogen is produced from solid or liquid carbon-containing fuels in a two-step process. The fuel is gasified with hydrogen in a hydrogenation reaction to produce a methane-rich gaseous reaction product, which is then reacted with water and calcium oxide in a hydrog... | 09/14/2004 |
| 6517790 | Converting fluorgyp to calcium sulfate Fluorgyp is converted to calcium sulfate by reacting sulfuric acid in the fluorgyp with calcium carbonate having a small particle size. The resulting product is useful as a set retarding agent for cement.... | 02/11/2003 |
| 6235257 | Process waters in phosphate manufacturing 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 undergoe... | 05/22/2001 |
| 6083465 | Method and apparatus for continuously calcining gypsum An apparatus for continuously calcining gypsum includes a flash calcining impact mill, a feed bin adjacent the impact mill for holding gypsum, and a gypsum feed control mechanism for supplying gypsum from the feed bin to the impact mill at a substantially... | 07/04/2000 |
| 5500197 | Process of purifying gypsum The process for purifying gypsum suspensions, particularly those formed in a flue gas desulfurizing plant, includes feeding the gypsum suspension (9) to a first hydrocyclone (1), which is operated to produce an underflow (11) with a comparatively high und... | 03/19/1996 |
| 5399323 | Method for improving reducing potential of natural gas feed A means to increase the reducing potential of natural gas used in the reduction of sulfates such as gypsum. A reducing mixture of natural gas and air (or oxygen) is heated prior to reduction of the sulfate. For gypsum reduction, heating the reducing mixtu... | 03/21/1995 |
| 5362471 | Process for producing gypsum flake from flue gas desulfurization This invention relates to an improved process for producing gypsum calcium sulfate dihydrate flakes from powdered gypsum calcium sulfate dihydrate obtained from the desulfurization of flue gas by the wet limestone process. The flakes have sufficient size ... | 11/08/1994 |
| 5324501 | Method for the preparation of low-chloride plaster products from calcium-containing residues of flue-gas purification plants Disclosed herein is a method for producing plasters that contain chloride contents of less than 0.5% by weight from calcium-containing impure products or residues having a high chloride content (e.g., about 10% or higher based on the total product or resi... | 06/28/1994 |
| 5312604 | Work-up of waste materials from barium or strontium sulfide leaching A process for working-up waste materials from barium sulfide or strontium sulfide leaching in which the amount of waste material to be disposed of is substantially decreased.... | 05/17/1994 |
| 5281242 | Method for recovering magnesium sulfate products from mixtures of epsomite and halite A simple, efficient and inexpensive method of purifying magnesium sulfate from mixtures of epsomite and halite. The method allows for the preparation of substantially pure magnesium sulfate products. The method generally involves heating a mixture of epso... | 01/25/1994 |
| 5200117 | Sulfate scale dissolution Alkaline earth metal scales, especially barium sulfate scale deposits are removed from oilfield pipe and other tubular goods with a scale-removing composition comprising an aqueous alkaline solution having a pH of about 8 to about 14, preferably about 11 ... | 04/06/1993 |
| 5173284 | Process for preparation of purified calcium sulfate in an aqueous medium A process for the preparation in an aqueous medium of purified calcium sulfate, with high whiteness, characterized in that it comprises: a) the formation of an aqueous solution by dissolution of impure hemihydrated calcium sulfate, at a concentration at most o... | 12/22/1992 |
| 5169444 | Process for preparing calcium sulfate anhydrite The process for preparing calcium sulfate anhydrite II by heating a flowable powder of flue gas gypsum moistened with less than 20% by weight, and preferably with from 7 to 17% by weight, of diluted sulfuric acid, wherein the sulfuric acid content is from... | 12/08/1992 |
| 5106600 | Process for producing tabular acicular gypsum crystals A process for economically producing tabular acicular gypsum crystals in a continuously stirred reactor is disclosed. The process involves establishing a steady state atmospheric pressure reaction zone of about 20% to about 25% by weight solids of gypsum ... | 04/21/1992 |
| 5015450 | Process for making calcium sulfate alpha-hemihydrate from calcium sulfate dihydrate The process makes calcium sulfate alpha-hemihydrate from finely divided calcium sulfate dihydrate by transforming the calcium sulfate dihydrate in the presence of saturated steam. A molded body is formed from the calcium sulfate dihydrate which has a plur... | 05/14/1991 |
| 5015449 | Process for making construction grade calcium sulfate alpha-hemihydrate from moist finely divided gypsum obtained from a power plant flue gas desulfurization The process makes calcium sulfate alpha-hemihydrate or essentially plaster of paris from finely divided gypsum made by desulfurizing flue gas obtain from a power plant fired by brown coal by transforming the calcium sulfate dihydrate in the presence of sa... | 05/14/1991 |
| 5011668 | Calcination apparatus In a method and apparatus for calcining calcium sulphate dihydrate or like heat sensitive material, in which a bed of the material is heated in a vessel (41) by the direct introduction of a hot gas through a tube (21) extending downwardly into the bed, th... | 04/30/1991 |
| 4804461 | Process for recovering barite from drilling muds At present the usual method of recycling of drilling muds by the exclusive application of classifying processes during drilling rig operation leads to the disposal of fine grained barite containing waste materials. In this invention, a simple one-stage fl... | 02/14/1989 |
| 4666688 | Method for recovery and conversion of strontium sulfate to strontium carbonate from low and medium grade celestite ores Essentially pure strontium carbonate is recovered from low to medium grade strontium sulfate containing ores by first treating the ore with a hydrochloric acid solution to remove extraneous materials including calcium, magnesium, barium, and iron. The rem... | 05/19/1987 |
| 4612173 | Method of purifying by-product gypsum Disclosed is a method of purifying by-product gypsum by making it into a sludge and washing the sludge in a single, multi-stage filtering washer. The washing liquid is recovered from the filtrate from the first stage of the washer and subject to neutraliz... | 09/16/1986 |
| 4520002 | Method for preparing elemental sulfur as a diffusion-resistant gas and methods for its use in making lime, sulfur dioxide and sulfuric acid from waste gypsum The present invention relates to the discovery of a method by which elemental sulfur may be delivered to a reaction zone, for gas-solids reaction, in the form of a concentrated, coherent, diffusion-resistant gas thereby permitting gas-solid reactions of g... | 05/28/1985 |
| 4423016 | Process for the production of dry flue gas gypsum A process for producing dry flue gas gypsum substantially free of hemihydrate and anhydrous calcium sulfate comprises drying wet flue gas gypsum, typically having a free water content of about 4-12% by weight, in direct contact with a partial stream withd... | 12/27/1983 |
| 4421731 | Process for purifying phosphogypsum A process for reducing radioactive contamination of phosphogypsum. Phosphogypsum containing radioactive material is calcined to form hemihydrate crystals carrying the radioactive contaminants, and a portion of the crystals is converted to substantially ra... | 12/20/1983 |
| 4402922 | Process for rapid conversion of fluoroanhydrite to gypsum A process for making an industrially usable gypsum from fluoroanhydrite in which fluoroanhydrite is contacted with a fluid reaction medium slurry containing soluble sulfate ions and a substantial proportion of small gypsum seed crystals to rapidly hydrate... | 09/06/1983 |
| 4399110 | Process for reducing the radioactivity of calcium sulfate prepared from phosphate rock The level of radioactivity in gypsum produced from phosphate rock can be reduced by adding to the slurry of acid and phosphate rock in the conventional process for producing phosphoric acid a combination of concentrated nitric acid or hydrochloric acid an... | 08/16/1983 |
| 4388292 | Process for reducing radioactive contamination in phosphogypsum A process of two crystallization stages for reducing radioactive contamination of phosphogypsum is disclosed. In the process anhydrite crystals are obtained through dehydration of the radiation containing phosphogypsum in strong sulfuric acid; a portion o... | 06/14/1983 |
| 4387083 | Process for the preparation of calcium sulphate anhydrite and calcium sulphate anhydrite obtained by this process A process for preparing calcium sulphate anhydrite from calcium sulphate dihydrate so that the calcium sulphate anhydrite crystals will have a predetermined average particle size. The process is conducted by recrystallizing the calcium sulphate dihydrate ... | 06/07/1983 |
| 4344925 | Ozone whitening of synthetic gypsum A process for the whitening of phosphogypsum comprising treating a phosphogypsum in aqueous suspension with an amount of ozone equal to at least 150 parts by weight per million parts by weight of phosphogypsum calculated as Ca SO4.2H.sub.2 O, t... | 08/17/1982 |
| 4298379 | Production of high purity and high surface area magnesium oxide Disclosed is a process for refining a magnesium and nickel containing ore, comprising the steps of grinding the ore; preparing a slurry of the ground ore in sulfuric acid containing less than ten percent of water; adding water to the acid-ore slurry in an... | 11/03/1981 |
| 4246019 | Method of producing a complex mineral fertilizer A method of producing a complex mineral fertilizer is disclosed, comprising the steps of decomposing polyhalite at a temperature not exceeding 110° C. in the presence of dilute nitric acid, neutralizing the obtained suspension with a substance selected f... | 01/20/1981 |
| 4146568 | Process for reducing radioactive contamination in waste product gypsum A process for reducing the radioactive contamination in waste product gypsum in which waste product gypsum is reacted with a dilute sulfuric acid containing barium sulfate to form an acid slurry at an elevated temperature, the slurry is preferably cooled,... | 03/27/1979 |
| 4132759 | Method of purifying brine used in electrolysis by the amalgam process In the process for the production of chlorine and alkali metal hydroxide by electrolysis according to the amalgam process using calcium- and/or sulphate containing crude salt, the calcium and/or sulphate contents introduced into the brine circuit by the c... | 01/02/1979 |
| 4120737 | Manufacture of calcium sulphate alpha hemihydrate A process for the manufacture of calcium sulphate alpha-hemihydrate which comprises the step of interacting an aqueous solution of calcium chloride and a source of sulphate or bisulphate ions in an aqueous system at a temperature above the calcium sulphat... | 10/17/1978 |
| 4120694 | Process for purifying a titanium-bearing material and upgrading ilmenite to synthetic rutile with sulfur trioxide A process for removing impurities from an oxide of titanium-bearing material such as a titania slag by treating the material with SO3 gas and subsequently leaching with a liquid. In particular a process for upgrading an ilmenite ore by preparin... | 10/17/1978 |
| 4119700 | Production of pharmaceutical barium sulphate A new simplified process is described for producing pharmaceutical barium sulphate in which the barium sulphate does not require dissolution for purification. The new process comprises grinding a naturally occurring barite ore containing individual crysta... | 10/10/1978 |
| 4113835 | Process for preparing pure synthetic calcium sulfate semihydrate A process for the purification of phosphate containing impure gypsum to obtain therefrom calcium sulfate semihydrate in a purified form by digesting the phosphate containing gypsum with nitric acid at a temperature between 22° and 100° C, the temperatur... | 09/12/1978 |
