Abstract: A method of recovering a metal, such as copper or nickel or zinc or cobalt, from a metal-containing material, such as a metal-containing material that has been categorized by a mine operator as being “non-economic” from the perspective of recovering the metal from the material. Mixing (i) the metal-containing material and (ii) pyrite and forming agglomerates. Leaching agglomerates with a leach liquor, with pyrite generating acid and heat that facilitate recovering the metal from the metal-containing material, and forming a pregnant leach liquor containing metal. Recovering the metal from the pregnant leach liquor.

Abstract: Disclosed is a process for the concurrent production of hydrogen and sulphur from a H2S-containing gas stream, with reduced, and preferably zero, emissions. The method comprises the catalytic oxidative cracking of H2S so as to form H2 and S2. Preferably, the oxidation is conducted using oxygen-enriched air, preferably pure oxygen. The process is conducted in a reaction chamber comprising a bifunctional catalyst material, so as to favor both the partial oxidation of H2S and the dissociation thereof.

Abstract: Disclosed is a catalyst suitable for the catalytic oxidative cracking of a H2S-containing gas stream, particularly in the event that the stream also contains methane and/or ammonia. The catalyst comprises iron and molybdenum supported by a carrier comprising aluminum. The carrier preferably is alumina. The iron and molybdenum preferably are in the form of sulphides. Also disclosed is a method for the production of hydrogen from a H2S-containing gas stream, comprising subjecting the gas stream to catalytic oxidative cracking so as to form H2 and S2, using a catalyst in accordance with any one of the preceding claims.

Abstract: Disclosed is a catalyst suitable for the catalytic oxidative cracking of a H2S-containing gas stream, particularly in the event that the stream also contains methane and/or ammonia. The catalyst comprises iron and molybdenum supported by a carrier comprising aluminum. The carrier preferably is alumina. The iron and molybdenum preferably are in the form of sulphides. Also disclosed is a method for the production of hydrogen from a H2S-containing gas stream, comprising subjecting the gas stream to catalytic oxidative cracking so as to form H2 and S2, using a catalyst in accordance with any one of the preceding claims.

Abstract: A process for advantageously efficiently treating a sulfureous combustible effluent stream by recovering the sulfur in elemental form comprises a step of combustion of the sulfureous combustible effluent stream with an oxidant gas in excess, and then a step of post-combustion of the effluents from the combustion step with an acidic gas. The stream of the post-combustion effluents, free of chemical compounds that are harmful to the efficacy of the Claus catalysts, is treated in a Claus unit, which performs the recovery of the sulfur in elemental form.

Abstract: Electrochemical processes to convert alkali sulfates into useful chemical products, such as syngas, alkali hydroxide, and sulfur are disclosed. An alkali sulfate is reacted with carbon to form carbon monoxide and alkali sulfide. In one embodiment, the alkali sulfide is dissolved in water and subjected to electrochemical reaction to form alkali hydroxide, hydrogen, and sulfur. In another embodiment, the alkali sulfide is reacted with iodine to form alkali iodide sulfur in a non-aqueous solvent, such as methyl alcohol. The alkali iodide is electrochemically reacted to form alkali hydroxide, hydrogen, and iodine. The iodine may be recycled to react with additional alkali sulfide. The hydrogen and carbon monoxide from both embodiments may be combined to form syngas. The alkali hydroxide from both embodiments may be recovered as a useful industrial chemical.

Abstract: A process is provided for stabilizing a sulfate and/or sulfide-rich waste material, comprising metal sulfide minerals, and sequestering CO2 comprises exposing the material to a CO2-enriched gas mixture, reacting the CO2-enriched gas mixture with the metal sulfide minerals and forming a CO2-depleted gas mixture and a carbon-containing compound and at least one product selected from the group consisting of a purified metal or a metal-rich compound suitable for smelting or refining, sulfuric acid, sulfur and sulfurous acid, and system and apparatus therefor.

Abstract: A system may include a sulfur recovery unit. The sulfur recovery unit may include an acid gas supply, which may supply acid gas, an oxygen supply, which may supply oxygen, a fuel supply, which may supply fuel. The fuel may have a higher heating value than the acid gas. Also, the sulfur recovery unit may include a thermal reaction zone, which may thermally recover sulfur from the acid gas by combustion of the fuel and the acid gas with the oxygen and through reaction of the acid gas with combustion products arising from the combustion.

Abstract: The present invention describes a reactor (1) for continuously preparing hydrogen sulfide H2S from hydrogen and sulfur, comprising a distributor device (15) for distributing gaseous hydrogen in a sulfur melt (9) present at least in a lower part of the reactor. The distributor device (15) is arranged in the sulfur melt (9) and comprises a distributor plate (16) which is arranged in the reactor (1) and has an edge (17) extending downward and, if appropriate, has passage orifices (19). The hydrogen from a hydrogen bubble which forms below the distributor plate (16) is (for example through the passage orifices (19)) distributed in the sulfur melt (9) via the distributor plate (16).

Abstract: A process for making molecular hydrogen, elemental sulfur and sulfur dioxide from hydrogen sulfide. The process involves contacting a gas stream of hydrogen sulfide within a contacting zone with a contacting composition comprising metal sulfide in a lower sulfided state and yielding from the contacting zone a product gas stream comprising hydrogen and a recovered contacting composition comprising metal sulfide in a higher sulfided state. The higher metal sulfide is regenerated with oxygen to yield elemental sulfur and sulfur dioxide.

Abstract: The invention relates to a fission reactor (1) for a Claus plant, comprising a fireproof lined boiler (9), which contains a combustion chamber (2) with an influx opening for a mixture of fuel gas, air and acid gas containing H2S, a catalyst chamber (10) with a catalyst bed and a chamber on the outflow side (11) comprising a gas outlet for a hot process gas that contains elemental sulphur. According to the invention, the boiler is configured as a horizontal cylindrical boiler, in which the combustion chamber (2), the catalyst chamber and the chamber on the outflow side (11) are located next to one another. The catalyst chamber is delimited on both sides in the flow direction by gas-permeable chequer bricks (14) and has a fill opening (15) on the shell side for introducing the catalyst bed.

Abstract: Sulfur sought to be removed from deposits formed at a subterranean gas producing well is dissolved in a high boiling point relatively pure and low cost non-aqueous solvent. The dissolved sulfur is then removed from the solvent by lowering the temperature of the solution to precipitate the sulfur which is then separated and recovered as a relatively pure product. After additional processing the regenerated solvent is injected back down the well hole to dissolve additional sulfur and reutilized in successive cycles of the process. An amine or solubilizing agent may be added to the non-aqueous solvent, and an oxidizing agent may be provided during the process to oxidize polysulfides to sulfur.

Abstract: A process and system for recovering waste heat from a kiln used for lime or cement production. The system unifies the kiln, a waste heat recovery and power generation circuit and a dry scrubber for scrubbing the pollutants from the kiln offgas. Essentially, the system employs the boiler component of the waste heat recovery and power generation circuit as a heat exchanger to recover the waste heat from the kiln, which is used to drive the steam turbines. The heat absorption from the latter stage lowers the temperature of the kiln offgas sufficiently for optimum performance from the scrubber. The presence of lime particles in the offgas effectively protects the boiler tube surfaces from corrosion which would occur at optimum scrubber temperatures, and subsequently provides the lime required as a scrubbing medium for the dry scrubber. Further, the efficient scrubbing allows for the use of any fuel for firing the kiln inclusive of high sulphur content compounds.

Abstract: Embodiments of a sulfur extraction process comprise treating mined sulfur ore with a disulfide oil to dissolve the sulfur in the ore. The process occurs at a temperature less than a temperature sufficient to melt sulfur. The sulfur crystals may be isolated by cooling the dissolved sulfur to a temperature sufficient to crystallize the sulfur. An apparatus for extracting sulfur from sulfur ore comprises a first receptacle for contacting a disulfide oil with mined sulfur ore at an elevated temperature sufficient to dissolve sulfur, a second receptacle coupled to the first receptacle for cooling dissolved sulfur such that sulfur crystals form, and a filtration apparatus coupled to the second receptacle for isolating the sulfur crystals. Solvents used in the apparatus may be recycled.

Abstract: The present invention relates to a process for the recovery of elemental sulphur from residues produced in hydrometallurgical processes based on leaching with a solution of sodium sulphide in which the sulphur contained in the residues is selectively leached as sodium polysulphide. The sulphur leaching solution is conveniently regenerated and recycled to the process.

Abstract: Embodiments of a sulfur extraction process comprise treating mined sulfur ore with a disulfide oil to dissolve the sulfur in the ore. The process occurs at a temperature less than a temperature sufficient to melt sulfur. The sulfur crystals may be isolated by cooling the dissolved sulfur to a temperature sufficient to crystallize the sulfur. An apparatus for extracting sulfur from sulfur ore comprises a first receptacle for contacting a disulfide oil with mined sulfur ore at an elevated temperature sufficient to dissolve sulfur, a second receptacle coupled to the first receptacle for cooling dissolved sulfur such that sulfur crystals form, and a filtration apparatus coupled to the second receptacle for isolating the sulfur crystals. Solvents used in the apparatus may be recycled.

Abstract: A new process of regenerating thiosulphate from a spent thiosulphate solution comprises the steps of:

Abstract: A method for treating compounds which contain reactive sulfur is disclosed, wherein the treatment produces compounds which contain sulfur in a non reactive form. The method is based on the use of an oxidizing compound selected from the group consisting of water soluble inorganic persulfates, water soluble inorganic and organic adducts of hydrogen peroxide and mixtures thereof. The method is particularly useful in preventing stress corrosion cracking of stainless steel and in preventing auto-ignition of pyrophoric iron sulfide.

Abstract: High quality hydrophilic sulfur is recovered from a biologial conversion zone in which a sulfur containing compound such as a sulfide is converted to elemental sulfur. The sulfur is rendered hydrophilic due to the fine particle size and attachment of biomass to the particles. The sulfur is recovered as an undamaged agglomerate powder after being processed in at least two stages of purification.

Abstract: Hydrogen sulfide is removed from gas streams by reaction with sulfur dioxide in an autogeneously-formed aqueous acid medium according to the equation: SO.sub.2 +2H.sub.2 S.fwdarw.2H.sub.2 O+3S the sulfur being removed from the aqueous phase. Carbonyl sulfide and/or carbon disulfide is removed from gas streams by hydrolysis to hydrogen sulfide in the presence of a weak organic base catalyst, such as quinoline, with the hydrogen sulfide reacting with sulfur dioxide to form sulfur.

Abstract: Pyritic ores are heated with microwave energy in a fluidized bed to a temperature in the range of approximately 573 degrees Kelvin to 823 degrees Kelvin with a controlled amount of oxygen to promote the oxidation of the pyritic ores according to the reaction: 2FeS.sub.2 +3/2 O.sub.2 .fwdarw.Fe.sub.2 O.sub.3 +4S, thereby preventing the production of sulphur dioxide.

Abstract: A process and system for removing hydrogen sulfide from a gaseous stream such as one of natural gas. A sour gas stream containing H.sub.2 S is contacted with a nonaqueous, water-insoluble sorbing liquor which comprises an organic solvent for elemental sulfur, dissolved elemental sulfur, an organic base to promote the reactions, and an organic solubilizing agent an agent suitable for maintaining the solubility of polysulfide intermediates which may otherwise separate when they are formed during operation of the process. Hydrogen sulfide (H.sub.2 S) gas is sorbed into this liquor and then reacts with the dissolved sulfur in the presence of the base to form polysulfide molecules. The solution is then sent to a reactor where sufficient residence time is provided to allow the polysulfide forming reactions to reach the desired degree of completion. From the reactor, the solution flows to a regenerator where the solution is oxidized (e.g., by contact with air), forming dissolved elemental sulfur and water.

Abstract: The invention provides methods for purifying hydrogen sulfide gas having impurities therein. In one exemplary method, the hydrogen sulfide gas is purified by passing the gas through a filter media, with at least some of the impurities being trapped within the filter media. A catalyst may also be provided to break down some of the impurities to hydrogen sulfide and sulfur, so that the sulfur may be trapped and collected within the filter media.

Abstract: A wet process of regenerative type for removing SO.sub.2 contained in combustion gases in which SO.sub.2 is caused to be absorbed by a diluted aqueous solution of BaS, with a mixed precipitate of elemental S, BaSO.sub.3 and BaSO.sub.4 being formed by the consequent reactions. Sulfur is extracted from the precipitate--recovered by filtration--by using a solution of (NH.sub.4).sub.2 S; the resulting polysulfide is distilled, with pure elemental S and the solution of (NH.sub.4).sub.2 S to be recycled, being obtained. The residual mixture of BaSO.sub.3 and BaSO.sub.4 remaining after sulfur extraction is reduced with coal in a high temperature furnace, in order to obtain BaS to be recycled, as an aqueous solution, to the SO.sub.2 absorption step.

Abstract: There is provided a process for the catalytic production of hydrogen from the reaction of hydrogen sulfide and carbon monoxide with the elimination of the carbonyl sulfide and/or sulfur dioxide by-products. The carbonyl sulfide and the sulfur dioxide are combusted or reacted in one or more reaction steps with each other, oxygen and/or hydrogen sulfide to produce carbon dioxide, water, sulfur or sulfuric acid or a combination of these.

Abstract: A method for site remediation for mitigating contamination from metals or metal compounds, particularly resulting from the situation of mine tailing waste on or near water sources, including the reprocessing and redeposit of separated sands and slimes in-site in a manner to encourage rather than inhibit leaching of residuals by chelating agents or biological agents with recovery of leachate and removal of metals or metal compounds.

Abstract: A continuous process for the microbiological conversion and removal of malodorous sulphur-containing organic and inorganic compounds from a gaseous stream, comprising the steps of providing a column filled with packing material. Passing a biologically active liquid stream containing nutrients and a consortia of bacteria including microorganisms of the Thiobacillaceae family through the column whereby the bacteria are immobilized onto all available surface area of the packing material. Maintaining the temperature conditions within the column between about 5.degree. C. to about 47.degree. C. and the pH conditions between about 5 to about 9. Concurrently passing a gaseous stream containing the malodorous sulphur-containing organic and inorganic compounds through the column at a liquid gas ratio of about 3:7 for a sufficient period of time to allow the bacteria to convert greater than about 97% of the sulphur compounds within the gaseous stream into a useful form of elemental sulphur.

Abstract: A process for abating the emission of hydrogen sulfide and nitrogen oxide from a condensate of steam, derived from a sulfide- and nitrite-containing geothermal brine, comprising introducing an oxidizing agent into the condensate in an amount less than that which would be required to directly oxidize all the sulfide and nitrite to sulfate and nitrate. The process optionally provides for periodically introducing a biocide into the condensate to control the growth of organism therein.

Abstract: A method of carrying out a chemical reaction in a fluidized bed reactor is provided wherein the reactants include at least one finely sub-divided reactant having a particle size substantially smaller than that of the particles constituting the fluidized bed. The reactor includes a downcomer compartment and a riser compartment operated such that the fluidized bed particles circulate by moving down the downcomer compartment and up the riser compartment. The finely divided solid reactant is introduced, either as such, or in an agglomerated form, into the central or upper region of the fluidized bed in the downcomer compartment such that it becomes entrained in the downwardly moving fluidized bed in the downcomer compartment and moves countercurrent to the fluidizing gas towards the lower end of the riser compartment. The reaction products which may be, or include, fine divided solids are carried out of the top of the reactor from the riser compartment.

Abstract: In accordance with the invention, gases containing sulfur dioxide are passed through a solution rich in ferric iron and containing barium chloride or calcium chloride. Sulfur dioxide is oxidized by the ferric ion to sulfur trioxide when then forms sulfuric acid in the water. The sulfuric acid reacts with the barium ion to form barium sulfate, while the ferric ion is reduced to the ferrous state. The barium sulfate is separated from the mother liquor by filtration and is then reduced to barium sulfide with a carbonaceous material or any reducing gas. Then, the barium sulfide is reacted with another portion of solution rich in ferric iron to form elemental sulfur, while the barium ion or calcium ion combines with the chloride ion to regenerate barium chloride or calcium chloride as the case may be. The resulting solution, after the sulfur has been removed, is now rich in ferrous iron.

Abstract: This invention provides a catalyst and method for removing sulphur compounds from a fluid stream and decomposing such compounds to produce sulphur. Sour natural gas can be sweetened effectively by this invention, and sulfur can be prepared thereby. The invention employs a catalyst containing an alkali metal sulfide and sulfides(s) or selenide(s) of metal(s) showing polyvalent and/or amphoteric character, e.g. Zn, etc. The catalyst is generally impregnated on a microporous type support (e.g., alumina) and is capable of providing reactive oxygen. Its activity is sustained by exposure to small amounts of oxygen either while decomposing the sulphur compound, or thereafter.

Abstract: A thermochemical cycle for the recovery of hydrogen and sulfur by splitting hydrogen sulfide, based upon initial reactions between the hydrogen sulfide and carbon dioxide or carbon monoxide. The cycle exists in three versions, two utilizing the initial reaction of hydrogen sulfide and carbon dioixide. One of these versions utilizes high temperature for the initial step for production of carbon monoxide for use in the shift reaction to produce hydrogen. The other conducts the initial step of moderate temperature in the presence of a desiccant to increase the yields of carbonyl sulfide and carbon disulfide, which are subsequently subjected to high temperature reactions to produce the carbon monoxide for the shift reaction.

Abstract: The invention relates to a method for cleaning exhaust gases weak in sulphur dioxide, or sulphur dioxide and hydrogen sulphide. In order to remove the sulphur content of an exhaust gas, the exhaust gas is absorbed into a solution containing sulphide. Thereafter into the solution is added an agent which causes any unstable compounds of sulphur and oxygen, such as thiosulphate and polythionates, which are formed in the scrubbing solution, to decompose into elemental sulphur and sulphate in the autoclave whereinto the scrubbing solution is fed. The pH of the solution emerging from the autoclave is adjusted to stay within the range 2.0-2.9.

Abstract: An SO.sub.2 -containing gas, in particular, pre-stage gas for the Claus reaction to recover sulfur can effectively be purified by removing NH.sub.3 contained therein using a TiO.sub.2 catalyst.

Abstract: A continuous process for removing hydrogen sulfide from a gas stream by contacting the gas stream with a solution of ammonium hydroxide to produce an effluent liquid stream comprising ammonium sulfide which is fed to a heating zone maintained at least at the boiling temperature of said solution and supplied with an oxygen containing gas sparge wherein ammonia and hydrogen sulfide are removed from said zone as vapor and sulfur is removed from said zone as an aqueous dispersion, the sulfur being separated in a filtration zone from the residual aqueous liquid which is recycled back to a contact zone together with said ammonia and said hydrogen sulfide vapor.

Abstract: Organic sulphides are extremely malodorous compounds that are found in gaseous or aqueous effluents from many industries such as paper and pulp manufacture, hydrocarbon refinering, tanneries, and in the synthesis of organic sulphur compounds. Their removal is necessary before such effluents can be discharged into the environment.In the present invention their removal is effected using hydrogen peroxide at a pH controlled to pH 8.5 to 11.5 and in the presence of a catalytic amount of a soluble tungstate. Such a process is especially applicable to the removal of dialkyl disulphides, which are regarded as being especially difficult to remove oxidatively. In especially preferred conditions, the pH is about pH 11 and about 3-4 moles H.sub.2 O.sub.2 is used per mole equivalent of sulphur, in the presence of at least 20 ppm sodium tungstate (as W).

Abstract: Waste containing sulfur and nickel sulfide is heated to volatilize sulfur and reacted with hydrogen chloride to form nickel chloride.

Abstract: A process for the recovery of sulfur from sulfur-bearing ores employing an aqueous leaching solution containing calcium monosulfide, calcium hydrosulfide or mixtures of such calcium sulfide species. The sulfur ore is contacted in an extraction zone with the aqueous leaching solution under conditions to solubilize sulfur from the ore in the form of calcium polysulfide. Preferably, the extraction step is carried out at an elevated temperature. The loaded leaching solution is recovered from the extraction zone and applied to a sulfur-production zone. Here the loaded solution is contacted with hydrogen sulfide under conditions to react the hydrogen sulfide with the calcium polysulfide to produce calcium hydrosulfide and elemental sulfur. The calcium hydrosulfide solution is recycled for use as leaching solution in the sulfur extraction zone.

Abstract: An apparatus is provided for the elimination of the gaseous pollutants sulfur dioxide and nitric oxide from the emissions of furnaces and smelters, and for the production of two commercial products, liquid sulfur and nitric acid. Two precipitators are operated in series, each containing an annular reaction chamber and a cylindrical separation chamber surrounded by the reaction chamber. The first precipitator combines the furnace or smelter emissions with methane in its reaction chamber in order to reduce the sulfur dioxide in the emissions to sulfur. The emissions are then passed through a tangential duct to the first precipitator's separation chamber where the fine sulfur praticles are converted to liquid sulfur by sending the mixed gases through an involuted spiral baffle and allowing the sulfur particles to coalesce on a trip wire grid. The sulfur particles then melt and fall by gravity to the bottom of the separation chamber, from which point the liquid sulfur is withdrawn.

Abstract: For the removal of sulfur compounds, especially H.sub.2 S, from gaseous mixtures, said mixtures are scrubbed with a physical solvent which is later regenerated and reused. To the solvent are added (a) an oxidizing agent for converting the sulfur compounds into elemental sulfur, and (b) additive means for increasing the settling rate of the thus-formed sulfur.

Abstract: An improved method for the recovery of elemental sulfur(S) from a coal-gas containing hydrogen sulfide (H.sub.2 S) wherein hot lime (CaO) is used and then regenerated according to the following chemistry:CaO+H.sub.2 S=CaS+H.sub.2 OCaS+3/2 O.sub.2 =CaO+SO.sub.2SO.sub.2 +C=S+CO.sub.2These chemical reactions are conducted in-situ while the supply of carbon (C) for the formation of the elemental sulfur(S) is derived from a component of the coal-gas itself to increase the overall efficiency of desulfurization, increase the uniformity of the carbon deposit into the hot lime (CaO), and eliminate the extra and cumbersome steps of physically moving the spent lime (CaO) for regeneration and returning it after regeneration, and the step of adding coal to react with the sulfur dioxide (SO.sub.2) formed as an off-gas during regeneration.

Abstract: A process for the removal of HCN from gaseous streams is described, the process being characterized by reaction of the HCN in the gaseous stream with an ammonium polysulfide solution and formation of ammonium thiocyanate in solution, precipitation and removal of sulfur from the ammonium thiocyanate-containing solution, and hydrolysis of the ammonium thiocyanate. Provision is made for recycle of hydrolysis products.

Abstract: A process for the removal of HCN from gaseous streams is described, the process being characterized by reaction of the HCN in the gaseous stream with an ammonium polysulfide solution, formation of ammonium thiocyanate in solution, decomposition of ammonium polysulfide and precipitation of sulfur from the ammonium thiocyanate solution in a stripping zone, and hydrolysis of the ammonium thiocyanate. Recycle or recovery of sulfur and hydrolysis products are contemplated.

Abstract: A process for the removal of HCN from gaseous streams is described, the process being characterized by reaction of the HCN in the gaseous stream with an ammonium polysulfide solution, formation of ammonium thiocyanate, and hydrolysis of the ammonium thiocyanate. Recycle of hydrolysis products is contemplated.

Abstract: A method is provided for reconditioning a hydrogen sulfide removal system, such as a Stretford process system in which elemental sulfur is formed, after the system has become contaminated with sulfur-feeding bacteria to an extent that operation thereof is substantially impaired. The method includes adding a bactericide to the washing solution employed in the system to destroy the bacteria and adding a surfactant to the solution to remove dead bacteria from the surfaces of particulate sulfur formed in the system so that the particles can agglomerate in the intended manner to enable sulfur removal from the solution.

Abstract: Hydrogen is produced from hydrogen sulfide by coupling, in a single reaction zone, the partial oxidation of hydrogen sulfide to water and sulfur with the thermal decomposition of hydrogen sulfide to hydrogen and sulfur. When one mole of hydrogen sulfide is burned with a stoichiometric deficiency of oxygen, enough thermal energy is generated by the exothermic partial oxidation to effect the thermal dissociation of about two moles of hydrogen sulfide. The gas mixture exiting from the reaction zone is substantially instantaneously cooled by quenching with cooler gas of substantially the same composition to prevent significant recombination of hydrogen and sulfur. The thermal energy in the gas following the quench step is used to preheat the H.sub.2 S and to cause some dissociation before entry into the reaction zone.

Abstract: A cyclic process for the removal of hydrogen sulfide, and carbon dioxide, from a variety of gas streams is disclosed. The gas stream containing the sour gas(es) is contacted with an aqueous solution of a specific reactant ligand or chelate, or mixtures thereof, optionally in an absorbent, containing specific stabilizers for improvement of chelate life. The hydrogen sulfide is converted to sulfur, CO.sub.2 may be absorbed to produce a purified gas stream, and the reactant chelate is reduced. The process includes sulfur removal and regeneration of the reactant chelate.

Abstract: A method of growing crystalline semiconductors such as GaAs is disclosed. The method involves epitaxial deposition from the vapor phase and provides dopant material such as sulphur in the form of a molecular beam. The molecular beam is developed by effusion from a knudsen cell. The difficulties previously encountered using sulphur as such a cell are counteracted by use of an electrochemical cell as the sulphur source. The technique allows complicated doping profiles to be produced.

Abstract: A process for removing SO.sub.2 and NO.sub.x from waste gas and recovering sulfur comprising scrubbing the waste gases with a water slurry of FeS in the presence of FeSO.sub.4 and Na.sub.2 SO.sub.4. SO.sub.2 is captured by the formation of FeS.sub.2 and FeSO.sub.4 in the scrubber. By thermal regeneration in a reducing atmosphere the FeS.sub.2 is converted to FeS and Na.sub.2 SO.sub.4 to Na.sub.2 S. The FeS is recycled to the scrubber. The Na.sub.2 S is returned to the system reacting with FeSO.sub.4 to form Na.sub.2 SO.sub.4 and FeS. The last reaction reduces the amount of FeSO.sub.4 entering the regenerator where by an undesirable side reaction, it may be partially converted to SO.sub.2 and Fe.sub.3 O.sub.4.

Abstract: A hydrogen sulfide removal and conversion method in which a hydrogen sulfide-containing gas stream is contacted with a regenerable washing solution having a pH between about 5 and about 10 and containing solubilized vanadium, thiocyanate ions, a carboxylate complexing agent, one or more water-soluble quinones and one or more water-soluble nonquinone aromatic compounds capable of solubilizing tetravalent vanadium. The absorbed hydrogen sulfide is converted to elemental sulfur which, after oxidative regeneration of the washing solution, is separated from the regenerated solution.