Abstract: Phosphate rock and sulfuric acid are reacted to produce phosphoric acid and calcium sulfate by means of the hemihydrate wet process. In this improved process, the calcium sulfate hemihydrate is crystallized from solution in the presence of an organic sulfonic acid or a derivative thereof. The organic sulfonic acid or its derivative improves the growth of the calcium sulfate hemihydrate crystals and thus improves the filtration rate of the slurry produced in this improved process.

Abstract: Phosphate rock and sulfuric acid are reacted under conditions which result in the formation calcium sulfate hemihydrate and phosphoric acid of about 30% to about 55% P.sub.2 O.sub.5. A two vessel reaction system is used in which the reaction slurry undergoes inter- and intra- vessel circulation. This results in excellent dispersion of reactants and minimization of temperature and concentration gradients throughout the slurry.

Abstract: Wet process phosphoric acid may be purified by solvent extraction to produce a product of greater purity and concentration than has hitherto been attainable by employing an acyclic hexanone, preferably methyl isobutyl ketone as the solvent. Preferably the extraction of the acid into the ketone and the release into water are carried out in 2 actual or theoretical counter-current stages. Alternatively the release may be carried out into an aqueous solution of a base.

Abstract: Nitrogen oxides in a combustion flue gas are removed by reduction in a gaseous phase at a low temperature in the absence of any catalyst by adding urea and an oxidizing agent for decomposition of urea, such as ozone, nitric acid, hydrogen peroxide, chlorine, chlorine dioxide, or oxy acids of chlorine or their salts. NO.sub.x removal can be carried out in a very simplified manner with high percent NO.sub.x removal.

Abstract: Diluted sulfuric acid used in the production of wet process phosphoric acid is obtained by the admixing of gypsum-containing waste water with concentrated sulfuric acid and subsequently cooling in a liquid-to-liquid heat exchanger. By maintaining the concentration of the diluted acid at from about 65 to 80% H.sub.2 SO.sub.4, harmful formation of scale in the heat exchanger is prevented. The process permits the recovery of P.sub.2 O.sub.5 values from gypsum-containing waste waters and does not require expensive dilution tanks or flash coolers.

Abstract: In a combustion chamber, auxiliary combustion is effected by using carbon monoxide and/or hydrogen immediately after each charge of the main fuel has been burnt up therein. This method of combustion enables the nitrogen oxides resulting from the combustion of the main fuel to be reduced and brought to extinction by the auxiliary combustion, with the result that the nitrogen oxide content of the exhaust gas from the said combustion chamber is depressed.

Abstract: The invention provides stabilized pulverulent red phosphorus. It comprises a homogeneous blend of red phosphorus particles with a size of at most about 2 mm and a metal compound of the second or third group of the Periodic System as an oxidation stabilizer, wherein the metal compound is the neutral aluminum, magnesium, calcium or zinc salt of orthophosphoric acid, the metal compound being present in the homogeneous blend in a proportion of about 0.5 to 5 weight %.

Abstract: An improved method and apparatus for reducing NO.sub.x emissions to the atmosphere from stationary combustion sources. The improvement is accomplished by providing a plurality of zones and/or stages for injecting a suitable reducing gas and then injecting the reducing gas through one or more of said zones. The particular zone or zones actually used will be determined by temperature of the combustion effluent gas in the immediate vicinity thereof. Similarly, the exact composition of the reducing gas employed will be determined by the same temperature.

Abstract: The invention provides stabilized pulverulent red phosphorus. It comprises a homogeneous blend of red phosphorus particles with a size of at most about 2 mm and a metal compound of the second or third group of the Periodic System as an oxidation stabilizer, wherein the metal compound is the aluminum, magnesium, calcium or zinc salt of an alkyl-, cycloalkyl-, aryl- or aralkylphosphonic acid having 1 to 20 carbon atoms, the metal compound being present in the homogeneous blend in a proportion of about 0.5 to 5 weight %.

Abstract: A method of treating a combustion exhaust gas containing nitrogen oxides comprises:A first step of removing nitrogen oxides by treating a mixture of the exhaust gas, oxygen and ammonia in the absence of hydrogen or in the presence of lower than 10 mole ratio of hydrogen to ammonia at a temperature from 700.degree. C to 1300.degree. C andA second step of adjusting a mole ratio of hydrogen to ammonia in the pretreated exhaust gas to higher than 3 and treating the mixed gas at a temperature from 490.degree. C to 700.degree. C.

Abstract: Treatment of wet process phosphoric acid to inhibit post-precipitation by steps including addition of an aluminum silicate material such as perlite or the like to dilute acid from which a major portion of solids has been removed, concentration of the resulting dilute acid, and removal of resulting precipitate.

Abstract: A reaction mass for use in the preparation of chlorine and ammonia by contact with ammonium chloride, in which the reaction mass contains iron oxide which is capable of chemically combining with chlorine in the reaction with ammonium chloride and an alkali metal chloride, with the ratio of iron oxide and alkali metal chloride being such that the ratio of the chlorine chemically combined with the iron to the chlorine chemically combined with the alkali metal is less than 1.

Abstract: Wet-process phosphoric acid is purified sufficiently to take the place of purified thermal-process acid by a method which comprises (1) contacting an initial aqueous phase of a crude wet-process phosphoric acid with a water-immiscible solvent for phosphoric acid and allowing phosphoric acid and anionic impurities to be extracted or charged into said solvent leaving the cationic impurities in the first aqueous phase; (2) mechanically separating the charged solvent from the initial aqueous phase and contacting the charged solvent with water to allow the phosphoric acid and anionic impurities to be re-extracted into a second aqueous phase; (3) contacting the second aqueous phase with a water-immiscible alkaline liquid medium and allowing the anionic impurities to be transferred to said alkaline medium; and (4) mechanically separating the second aqueous phase containing pure phosphoric acid.

Abstract: Nitrogen oxides are removed from flue gas evolving from stationary sources and containing the nitrogen oxides through reduction of nitrogen oxides to nitrogen by passing the flue gas over a catalyst of metal compounds containing oxysulfur compounds in the presence of an ammonia gas.

Abstract: A process for the wet-treatment of an exhaust gas in which nitrogen oxide and sulfur oxide contained in the exhaust gas are removed by use of an absorbent comprising a lime slurry containing an alkali metal or alkaline earth metal iodide, wherein an oxidizing agent is supplied to at least a part of iodide containing liquid retrieved from the wet-treatment to oxidize the iodide and thereby recover said iodide as iodine.

Abstract: Phosphate ora matrix is treated to recover P.sub.2 O.sub.5 values. The matrix may be the phosphate ore as it is mined, or it may be residue formed upon dewatering benefication slimes. Without being subjected to beneficiation, this matrix is slurried with an organic solvent in a slurry vessel. When the slurry is mixed with a strong mineral acid, a system having a single liquid phase is formed with the organic solvent serving as a vehicle for distribution of the mineral acid which in turn solubilizes P.sub.2 O.sub.5 values for their extraction from the matrix. Thereafter the P.sub.2 O.sub.5 values are separated from the solid phase and then removed from the organic solvent.

Abstract: Substantially fluoride-free phosphoric acid is produced by the acidulation of phosphate rock with sulfuric acid wherein the acidulation reaction is conducted in the presence of added potassium as K.sub.2 O bearing compounds, e.g. KHSO.sub.4, K.sub.2 SO.sub.4, KH.sub.2 PO.sub.4 or KOH, and additional silica, to precipitate fluorides and silica as potassium silicofluoride and then removed on separation of the gypsum formed. Optionally, additional silica may be added to the phosphoric acid solution recovered after precipitation and removal of the gypsum, to precipitate additional fluoride as potassium silicofluoride to further purify the phosphoric acid. In a further embodiment sufficient potassium may be added along with additional silica in the acidulation step to produce potassium dihydrogen phosphate and phosphoric acid as additional products.

Abstract: The present invention relates to a wet process for the manufacture of phosphoric acid, which process essentially comprises a digestion step in which phosphate rock is digested by means of phosphoric acid and sulfuric acid to form a slurry containing highly concentrated phosphoric acid together with calcium sulfate hemihydrate, and a separation step in which the slurry is filtered for separation of calcium sulfate hemihydrate from the highly concentrated phosphoric acid (in which the concentration of P205 in the product acid is higher than 40% by weight, based on the weight of the product acid) and which is characterized by supplying active silica at a ratio of 0.2-5% by weight, based on the weight of phosphate rock, in order that active silica may be present in the above mentioned digestion step.

Abstract: The invention provides stabilized pulverulent red phosphorus. It comprises a homogeneous blend of red phosphorus particles with a size of at most about 2 mm and a metal compound of the second or third group of the Periodic System as an oxidation stabilizer, wherein the metal compound is the aluminum, magnesium, calcium or zinc salt of an acid orthophosphoric acid ester of a long chain aliphatic alcohol, which may be ethoxylated, or phenol, the metal compound being present in the homogeneous blend in a proportion of about 0.25 to 5 weight %.

Abstract: A process for the separation of ammonia from a gaseous mixture containing ammonia and hydrogen cyanide which comprises contacting said gaseous mixture in an absorption stage with an absorbent liquor comprising an acidified ammonium nitrate solution thereby selectively absorbing ammonia from said gaseous mixture and forming a solution of diminished acidity, adding nitric acid to the ammonium nitrate-containing solution of diminished acidity to restore its acidity to its initial level and recycling said restored solution to said absorption stage.