Abstract: A process for the separation of metal sulphates from dilute sulphuric acid by evaporative concentration of the sulphuric acid to a concentration of from 55 to 75% by weight H.sub.2 SO.sub.4, cooling of the resulting solution or suspension and mechanically separating the solid metal sulphates and/or hydrogen sulphates, wherein an Fe(III) content of at least 0.01% by weight is ensured before the separation.

Abstract: The present invention provides a process for recovering boron trifluoride from an impure gaseous boron trifluoride residue. The process comprises: (a) feeding an impure gaseous boron trifluoride residue containing sulfur dioxide as an impurity into a mixture of boric and sulfuric acids wherein the acid mixture absorbs boron trifluoride from the impure boron trifluoride residue and slightly absorbs or does not absorb sulfur dioxide from the impure gaseous boron trifluoride residue; and (b) removing the unabsorbed sulfur dioxide from the acid mixture.The present invention also provides a boron trifluoride preparation and purification process.

Abstract: The present invention provides a process for generating a reagent of sulfur trioxide in a carrier. A source of sulfur trioxide, a carrier, and oleum are introduced into a reagent generator. The sulfur trioxide, carrier, and oleum are then contacted to provide a reagent of sulfur trioxide in the carrier. Separate oleum and sulfur trioxide in carrier phases are formed, and oleum is removed from the reagent generator. The sulfur trioxide in carrier reagent is then ready to be used, preferably in a process to treat the surfaces of polymeric resin material such as medical devices fabricated from a variety of polymeric resins. The carrier may be either a liquid halocarbon solution or an inert gas.

Abstract: A process for the extensive removal of undesirable metal ions, particularly vanadium ions, in the course of the concentration of dilute iron(II) sulfate-containing sulfuric acid solutions. The sulfuric acid solutions are concentrated by the evaporation of water and the separation of iron(II) sulfate to a content of 60 to 70% by weight H.sub.2 SO.sub.4. According to the invention, the content of trivalent titanium in the solution is adjusted such that the content of trivalent iron does not exceed 0.1 g/l. The trivalent titanium may be added from the outside, if not already present in an adequate amount in the solution, or may be formed in situ from the tetravalent titanium present in the solution by the addition of a reducing agent. Prior to the final concentration, part of the iron may be precipitated and separated as iron(II) sulfate heptahydrate by means of preconcentration and cooling of the preconcentrated sulfuric acid solution.

Abstract: A Pauling boiler for the concentration of sulphuric acid, wherein the external surface of the Pauling boiler is coated with aluminum.A process for the concentration of sulphuric acid in Pauling boilers by underfiring with gas or liquid fuels, wherein the concentration is carried out in a Pauling boiler coated with aluminum.

Abstract: An improved wafer cleaning process wherein a novel oxidant solution comprising ultrapure sulfuric acid, peroxydisulfuric acid, and ultrapure water used in a semiconductor wafer cleaning process is continuously withdrawn after use. The withdrawn oxidant is reprocessed continuously by contacting with alumina to remove fluoride ions. Water is continuously separated or stripped from the oxidant solution by heating the solution and bubbling an inert gas therethrough. The separated oxidant is continuously distilled and condensed to form a purified stream of sulfuric acid. The major portion of this stream is continuously returned to the wafer cleaning process. The remaining minor portion is continuously cooled, subjected to analysis for purity, and diluted with ultrapure water prior to electrochemical treatment in the anode compartment of an electrochemical cell. This converts at least a portion of the dilute sulfuric acid to peroxydisulfuric acid.

Abstract: A continuous process and apparatus for the repurification of ultrapure liquids. An oxidant solution comprising ultrapure sulfuric acid, peroxydisulfuric acid, and ultrapure water is continuously withdrawn from a process after use. The withdrawn oxidant is reprocessed continuously by contacting with alumina to remove fluoride ions. Water is continuously separated or stripped from the oxidant solution by heating the solution and bubbling an inert gas therethrough causing the water to vaporize from the solution. The separated oxidant is continuously distilled and condensed to form a purified stream of sulfuric acid. The major portion of this stream is continuously returned to the process. The remaining minor portion is continuously cooled, subjected to analysis for purity, and diluted with ultrapure water. The diluted sulfuric acid is further cooled prior to electrochemical treatment in the anode compartment of an electrochemical cell.

Abstract: A process for the preparation of sulphur dioxide by the thermal decomposition of metal sulphates in a fluidized bed reactor with sulphur-containing reducing agents and energy suppliers, characterized in that a mixture comprising the metal sulphates, the sulphur-containing reducing agents and 75 to 99% of the energy suppliers is fed into the fluidized bed reactors and the remainder of the energy suppliers is introduced separately into the fluidized layer of the fluidized bed reactor.

Abstract: Sulfuric acid contaminated with boron and fluoride values such as the waste acid of a boron trifluoride process is purified by contacting the contaminated acid with an inert gas to desorb boron trifluoride, and the inert gas is stripped by contacting with an absorbing liquid including concentrated sulfuric acid. Hydrogen fluoride and/or fluorosulfuric acid are added to contaminated sulfuric acid as agents to spring non-volatile boron value. In addition, the water content of the contaminated acid is adjusted within a narrow concentration range, to improve the efficiency of both the stripping and the absorption operations. The absorption of boron trifluoride into the absorbing sulfuric acid is improved when it contains boric acid. Preferably the contaminated sulfuric acid to be purified is one portion of the waste liquid and the absorbing liquid is another portion of the waste liquid of a boron trifluoride manufacturing process.

Abstract: Mineral acids are freed from heavy metals, especially copper, arsenic, antimony and lead by precipitating the metals in sulfide form. To this end, the mineral acid is reacted with hydrogen sulfide or an alkali metal sulfide solution under pressure and with thorough agitation, and formed solid matter is subsequently separated from the mineral acid under the pressure selected. The mineral acid may conveniently by admixed initially with a filter aid and then treated with hydrogen sulfide or the alkali metal sulfide solution.

Abstract: A process for production of chlorine dioxide and chlorine by reacting sodium chlorate with chloride ions and sulfuric acid where the chlorine ions partly are obtained from hydrochloric acid is described. In the process chlorine obtained as a by-product is reacted with sulfur dioxide in a reactor equipped with a condenser. The heat of reaction is removed by keeping the reactor at or above the boiling point of the reaction medium and the vapors are condensed in the condenser and brought back to the reactor. The obtained mixed acid comprising sulfuric acid and hydrochloric acid is returned to the chlorine dioxide reactor.

Abstract: A mixture of sulfuric acid and hydrochloric acid essentially free from dissolved sulfur dioxide to be used in a chlorine dioxide reactor is produced by reacting chlorine and sulfur dioxide in at least two reaction zones. In the bottom of a primary reaction zone the total amount of sulfur dioxide needed for the mixed acid production is introduced in an aqueous mixture of sulfuric and hydrochloric acid containing dissolved chlorine and gaseous chlorine. The sulfur dioxide reacts with chlorine in the aqueous phase to produce sulfuric acid and hydrochloric acid. The mixed acid produced in the primary reaction zone contains dissolved quantities of sulfur dioxide and is forwarded to a secondary reaction zone. Chlorine is introduced into the lower part of the secondary reaction zone. The amount introduced can be the total amount of chlorine to be used in the production of the mixed acid for the chlorine dioxide reactor, or it can be a part of that amount, the balance being introduced in the primary reaction zone.

Abstract: This invention relates to a process for the production of concentrated sulphuric acid from waste sulphuric acid which comprises subjecting said waste acid to microwave energy for a sufficient period of time to effect production of water vapor, whereby said waste acid is concentrated to a desired degree; removing said water vapor; and collecting said concentrated acid.

Abstract: In the desulphurizing of SO.sub.2 - and hydrogen halide-containing flue gases by catalytically oxidizing the sulphur dioxide on moist active carbon at a temperature of from 45.degree. to 70.degree. C. with the formation of 3 to 20% dilute sulphuric acid, the improvement which comprises contacting the dilute sulphuric acid with the hot flue gases to be desulphurized so as to evaporate water resulting sulphuric acid of a concentration of from 60 to 85%, and removing by evaporation the hydrogen chloride and hydrogen fluoride dissolved in the dilute sulphuric acid. Advantageously evaporation is carried out in two scrubbing stages, the hydrogen chloride and hydrogen fluoride being removed, by vacuum evaporation or by stripping with air or flue gas, from a mixture of the dilute sulphuric acid from the second scrubbing stage with the concentrated sulphuric acid from the first scrubbing stage, the mixture having the H.sub.2 SO.sub.4 concentration of from 40 to 70%.

Abstract: A method and apparatus for the recovery of heat from a sulfuric acid process are provided. Sulfur trioxide is absorbed into hot concentrated sulfuric acid, acid having a concentration greater than 98% and less than 101% and a temperature greater than 120.degree. C., in a heat recovery tower and the heat created by the exothermic reaction is recovered in a useful form in a heat exchanger.

Abstract: Metal ions are reduced from a higher to a lower oxidation stage using ferrophosphorus as the reductant.

Abstract: A device for and method of working up etching and pickling liquids consisting of a vertical furnace having one or more vertical reaction spaces through which balls move at a maximum packing density.The furnace has a temperature gradient from the bottom (high) to the top (low). The reaction space and the balls consist of a material which is inert with respect to the liquid to be worked up. The liquid is introduced into the upper side of the furnace so that a film is formed in the heated surface of the balls. The salt dissolved in the liquid decomposes pyrolytically. The metal oxide is deposited on the surface of the balls and is removed therefrom after leaving the reaction space. The acid residue vapours are drained at the top and recovered in a separate absorber to the original pickling or etching acid.

Abstract: A method of recovering concentrated sulfuric acid from the product obtained from the acid hydrolysis of a cellulose-containing material such a biomass. The method involves contacting the product with an extraction solvent comprising one or more of the C.sub.4 -C.sub.7 alcohols as the major component to separate the product into a sulfuric acid enriched phase. The sulfuric acid from this enriched phase is then separated and recovered by a further extraction procedure.

Abstract: Mercury is removed from sulfuric acid-bearing hot and moist smelting-plant or roasting-plant gases by cooling and scrubbing the hot gases by means of a concentrated sulfuric acid mist in order to sulfatize the mercury and to separate it from the gases. The cooling is carried out by vaporizing so much water or dilute sulfuric acid solution from the gases that the temperature of the gas drops to below the dew point, in order to produce a sulfuric acid mist which sulfatizes and washes the mercury, the gases being separated from the mist and directed to the sulfuric acid plant. The process can be carried out by means of nozzles installed in the pipe which feeds hot and moist sulfuric acid-bearing gases into the scrubbing tower of the sulfuric acid plant, water or acid obtained from the scrubbing tower being fed through the nozzles into the feed pipe in the form of a finely-divided mist.

Abstract: A method and apparatus for the recovery of heat from a sulfuric acid process are provided. Sulfuric trioxide is absorbed into hot concentrated sulfuric acid, acid having a concentration greater than 98% and less than 101% and a temperature greater than 120.degree. C., in a heat recovery tower and the heat created by the exothermic reaction is recovered in a useful form in a heat exchanger.

Abstract: A method for purification of a sulfuric acid solution such as, for example, a copper electrolyte which entrains at least one metal ion species selected from the group consisting of antimony ions, bismuth ions, and iron ions and having a sulfuric acid concentration of at least 50 g/liter is disclosed. The method comprises exposing the sulfuric acid solution to a chelating resin possessing aminomethylenephosphonic acid group as a chelate forming group thereby effecting adsorptive separation of the aforementioned at least one metal ion species from the solution. By the method described above, the antimony ions, bismuth ions, and/or iron ions contained as impurities in the copper electrolyte can be easily and efficiently separated out of the system without entailing any ecological problem.

Abstract: Apparatus and process for the manufacture of sulphuric acid by the contact process of the type comprising at least one gas-concentrated sulphuric acid contacting unit and a sulphuric acid heat exchanger characterized in that the contacting unit and/or heat exchanger is formed of high silicon content austenitic steel. The steel is also of use in sulphuric acid concentrators. Reduced corrosion rates are provided.

Abstract: In a process for producing sulphuric acid from roasting gas containing SO.sub.2, H.sub.2 O and Hg, comprising the steps of(a) drying the gas with H.sub.2 SO.sub.4(b) subjecting the gas to a catalytic oxidation treatment so as to produce a SO.sub.3 rich gas, and(c) absorbing the SO.sub.3 in concentrated sulphuric acid, while maintaining the concentration of this acid at its initial value by addition of diluted sulphuric acid, the gas from step (b) is scrubbed with oleum, thereby producing in step(c) H.sub.2 SO.sub.4 with less than 0.1 mg/l of Hg.

Abstract: A process for the purification of by-product sulfuric acid resulting from the synthesis of boron trifluoride, wherein the ratio of fluorine to boron is three or more, which process comprises entraining the by-product acid in an inert gas, the process being characterized in that before entrainment the anhydrous sulfuric acid is diluted with water in a proportion of from about one to about ten percent by weight of water with respect to the acid to be treated, the temperature being maintained above 90.degree. C., the sulfuric acid obtained containing less than 0.003% fluorine and less than 0.005% boron, so that the quality is substantially equivalent to a sulfuric acid directly obtained by the oxidation of sulfur.

Abstract: Process for regenerating spent acid is improved by using oxygen-enriched air for combustion, recycling stack gases, and preheating spent acid and air fed to the furnace.

Abstract: This invention provides a method of removing heat from the process gas in a sulfuric acid plant having interpass and final absorption towers by indirect heat exchange with a liquid without condensing acidic vapors from said process gas. The method comprises installing first and second economizers, the second economizer having first and second sections for liquid flow. The process gas flow through the first economizer before passing through the interpass absorption tower and through the second economizer before passing through the final absorption tower. A liquid flows through the first and second economizers for indirect heat exchange with the process gas, the liquid passing sequentially through the second section of the second economizer, the first economizer, and the first section of the second economizer.

Abstract: The disclosure describes the recovery of sulfuric acid from industrial liquors containing the same. A selective liquid-liquid extraction of said liquors is carried out under conditions producing an organic phase containing the sulfuric acid and an aqueous phase eventually containing impurities. The organic phase is treated with a base, such as gaseous NH.sub.3, in order to separate the sulfuric acid. This process is simple, non-polluting, and requires little energy.

Abstract: This invention relates to an improved process for reducing solute in a vapor stream and, particularly, to the adaption of this process in concentrating solutions in an evaporator wherein the solution is heated to volatilize solvent. The improvement for reducing solute in the vapor stream resides in (a) the utilization of a wire mesh mist eliminator pad having a wire diameter of from 0.001-0.05 inches, an interfacial area from 50-200 ft.sup.2 /ft.sup.3, a void space of about 90-99 percent and a packing thickness of 4-16 inches and (b) spraying a liquid through the mist eliminator pad, the liquid being sprayed uniformly over the surface of the mist eliminator pad at a rate of 0.6-2.5 pounds liquid per pound of vapor to provide a wetting rate of 0.1-0.25 gallons per minute per square foot of mist eliminator surface area. The process has been particularly advantageous in the multistage concentration of corrosive products particularly in the concentration of a 60-70% sulfuric acid solution to about 93 percent.

Abstract: The present invention relates to a process for the separation of boric acid from boric acid-containing sulphuric acid in which the concentration of the sulphuric acid is adjusted such that the boric acid precipitates therefrom.

Abstract: A method of separating acids or bases from vapors which are conveyed along with distillation vapors during concentration of a solution, comprising, passing said distillation vapors containing an acid or base, while being maintained at their existing pressure and temperature, through a salt solution which boils at said temperature and pressure, wherein, if an acid is to be removed from the distillation vapors, the salt solution contains a salt having an anion corresponding to that of the acid while being supplied with a base in an amount required to neutralize the acid, the cation of the base proportion corresponding to that of the salt, while, if a base is to be removed from the distillation vapors, the salt solution contains a salt having a cation corresponding to that of the base while being supplied with an acid in an amount required to neutralize the base in the distillation vapors, the anion of the acid corresponding to that of the salt so that salts are formed during neutralization which correspond to t

Abstract: Disclosed are a process and apparatus useful for reclaiming sulfur-containing waste materials such as waste or spent sulfuric acid and acid tars.The sulfur-containing waste material is burned in a multi-stage combustion furnace having, in sequence, a rotary furnace containing heated coke, an intermediate combustion chamber and a secondary combustion chamber. The temperatures, gas flow rates and amount of added air are carefully controlled.A separation gas is produced having a high sulfur dioxide content which can be used in the sulfuric acid contact process. The separation gas is free of nitrous oxides, hydrocarbons and sulfur trioxide.

Abstract: A gas phase process for the regeneration and concentration of spent sulfuric acid containing oxidizable impurities, which minimizes decomposition of sulfur trioxide to sulfur dioxide comprising: providing one or more reactor vessels containing hot turbulent combustion products; providing a supply of oxygen to the reactor; atomizing into the reactor vessel or vessels the spent sulfuric acid in droplets capable of evaporating in less than several milliseconds whether or not electromagnetic or ultrasonic energy sources are used to augment evaporation, having a particle size smaller than 50 microns, thereby vaporizing the droplets, almost instantaneously, dissociating the spent sulfuric acid into sulfur trioxide and water, and oxidizing the hydrocarbons; maintaining the temperature in the reactor vessel below 1000.degree. C.

Abstract: Nitrous oxide having a high purity is produced by reacting urea, nitric acid and sulfuric acid at a temperature of 40.degree. through 100.degree. C., and isolating the resultant nitrous oxide from the reaction gas mixture, without any danger of, for example, explosion during the reaction and without using expensive catalysts and sulfamic acid.

Abstract: Alkali metal sulfates are produced from an aqueous solution containing alkali metal hydrogen sulfate which comprises contacting the aqueous solution of alkali metal hydrogen sulfate with a hydrophilic solvent, the hydrophilic solvent being effective to extract at least a portion of the sulfuric acid formed as the alkali metal hydrogen sulfate is converted to alkali metal sulfate in the solution, together with at least a portion of the water present; permitting the alkali metal sulfate solid to crystallize; and recovering the solid alkali metal sulfate product. The hydrophilic solvent may then be extracted and separated from the sulfuric acid with a hydrophobic solvent and both solvents can be recovered and recycled.

Abstract: A method for removing mercury from a sulfuric acid solution including the steps of mixing the sulfuric acid solution with a hydrocarbon solution to form a chemical complex containing mercury. The hydrocarbon solution typically contains a lower alcohol and a halogen component. The mercury complex is removed by the addition of activated carbon and subsequent filtration. Alternatively, solvent extraction, volatilization or other suitable separation techniques can be used.

Abstract: A process for the concentration of dilute phosphoric acid in a phosphoric acid process characterized by a plurality of separate phosphoric acid cycles when the phosphoric acid is concentrated in each cycle by a vacuum evaporation is described wherein the phosphoric acid cycles is heated by indirect heat exchange by heat of formation formed in a sulfuric acid contact process.

Abstract: The invention relates to a process for the purification of fluoride-containing 65 to 95% strength waste sulfuric acid which contains water, organic impurities and fluoride. The impure sulfuric acid is introduced onto the top tray of a stripping column, in which this waste acid is heated and pre-concentrated. The heated acid then flows into a heating tank filled with boiling concentrated sulfuric acid. The sulfuric acid vapors escaping from this heating tank are condensed in the stripping column by the waste sulfuric acid flowing in counter-current. According to the invention, at least in the region of one tray of the stripping column, construction components which come into contact with acid vapors or liquid acid consist of acid-resistant plastic, at least on the surface.

Abstract: A highly efficient chlorine dioxide generating process which produces chlorine-free chlorine dioxide and neutral solid phase sodium sulphate from sodium chlorate, sulphuric acid and methanol is described. Solid phase sodium acid sulphate recovered from the high acidity reaction medium is metathesized using controlled quantities of water and controlled quantities of methanol to form the solid phase neutral sodium sulphate. Sulphuric acid recovered from the acid sulphate by the metathesis is recycled to the generator along with a part of the methanol used in the metathesis.

Abstract: A two-stage process for the catalytic decomposition of H.sub.2 SO.sub.4 wherein H.sub.2 SO.sub.4 in vapor form is contacted in a first stage with a platinum group metal catalyst at temperatures between about 700.degree. K. and 970.degree. K. The platinum group metal catalyst is supported on a substrate of titania, barium sulfate, zirconia, silica, zirconium silicate or a mixture thereof, and at least about 40 percent of the H.sub.2 SO.sub.4 is decomposed to SO.sub.2. Vapors from the first stage enter a second stage where they contact a copper oxide and iron oxide catalyst at a temperature above 970.degree. K. The second stage catalyst is supported on a substrate of barium sulfate, zirconium oxide or titanium oxide.

Abstract: The invention provides a process for the separation of a strong mineral acid from other species present in an aqueous solution and the recovery thereof. The process comprises the steps of: (a) bringing an aqueous solution containing the mineral acid to be separated into contact with a substantially immiscible extractant phase, whereupon the mineral acid to be separated selectively and reversibly transfers to the extractant phase; (b) separating the two phases; and (c) backwashing the extractant phase with an aqueous system to recover substantially all the mineral acid contained in the extractant phase. The special extractant phase used comprises a strong organic acid which acid is oil soluble and substantially water immiscible both in free and in salt form, an oil soluble amine which amine is substantially water insoluble both in free and in salt form and a carrier solvent for the organic acid and amine, the molar ratio of the organic acid to amine in the extractant phase being between about 0.5:2 and 2:0.5.

Abstract: A method for the separation of nitric acid from a mixture of nitric acid with one or more of phosphoric, sulphuric or hydrochloric acids, in which the nitric acid is selectively extracted from a first phase comprising the acid mixture into a second phase by an amine nitrate. The method may conveniently be carried into effect by treating an aqueous mixture of acids with kerosene containing tri-n-octylamine nitrate and a modifyier e.g. decanol following which the excess nitric acid is stripped from the kerosene phase by water or dilute nitric acid.

Abstract: A process for the concentration of dilute phosphoric acid in a phosphoric acid process characterized by a plurality of separate phosphoric acid cycles when the phosphoric acid is concentrated in each cycle by a vacuum evaporation is described wherein the phosphoric acid cycles is heated by indirect heat exchange by heat of formation formed in a sulfuric acid contact process.

Abstract: Sulfuric acid contaminated with boron and fluoride values such as the waste acid of a boron trifluoride process is purified by contacting the contaminated acid with an inert gas to desorb boron trifluoride, and the inert gas is stripped by contacting with an absorbing liquid including concentrated sulfuric acid. Fluosulfonic acid is added to contaminated sulfuric acid at levels approximately three times the molar values of boric acid contaminant as an agent to spring non-volatile boron values. The absorption of boron trifluoride into the absorbing sulfuric acid is improved when it contains boric acid. Preferably the contaminated sulfuric acid to be purified is one portion of the waste liquid and the absorbing liquid is another portion of the waste liquid of a boron trifluoride manufacturing process. Boric acid is added to the absorbing liquid, then boron trifluoride is stripped from the inert gas and absorbed into the absorbing liquid.

Abstract: This invention relates to an improvement in a process for the manufacture of a nitroaromatic compound produced by the mixed sulfuric-nitric acid nitration method. The improvement resides in the refining of the aqueous acid mixture and comprises the following sequential steps: (a) contacting the mixed aqueous acid mixture, after nitration, with an oxidizing or a reducing agent under conditions effective for removing contaminant nitrous acid; (b) contacting the aqueous acid mixture in step (a) with feed aromatic compound to remove contaminant organics and residual nitric acid and then, if necessary, (c) contacting the remaining acid mixture with sufficient oxidizing agent under oxidizing conditions to remove residual organic components.

Abstract: In a process for thermally cracking waste sulphuric acid, a combustible material is mixed with such acid and the mixture is supplied to a burner to which a flow of atomizing air is also supplied. A flow of secondary air which is enriched to about 23-40% by volume of oxygen is injected into a flame generated by burning said waste sulphuric acid-combustible material mixture to thereby thermally crack such acid while reducing the production of by-product sulphur trioxide.

Abstract: A method is provided for directly heating a concentrated sulphuric-acid solution by passing alternating electric current between surface-passivated electrodes immersed in the solution and by using electrodes of iron or an iron alloy having a low resistance iron or iron alloy inner core covered by an outer high resistance passivating surface layer which are so surface-passivated that the transition resistance between the electrodes and the concentrated sulphuric-acid solution is at least as great as the resistance exerted by the concentrated sulphuric-acid solution.

Abstract: A method of removal of arsenic from an acidic solution, in which ferrous ions contained in the solution are oxidized in the presence of high pressured oxygen and sulfuric acid to ferric ions, the solution with said ferric ions being mixed with the solution which has not subjected to oxidation, and the mixture of said solutions being controlled of its pH whereby ferric hydroxide is precipitated, which coprecipitates and adsorbs arsenic thereto.

Abstract: The method resides in that silicon tetrafluoride is subjected to water hydrolysis in the presence of sulphuric acid, the reactants being in an aerosol state.Hydrolysis is performed at a volume ratio of silicon tetrafluoride to sulphuric acid equal to 40:1-80:1, concentration of sulphuric acid within the range of 45-73 wt. %, and the rate of silicon tetrafluoride flow in the reaction zone of 0.2-4.0 m/sec. The process is run at room temperature and atmospheric pressure.As a result of hydrolysis, silicon dioxide and fluorine-containing sulphuric acid solution are obtained, hydrogen fluoride being extracted from the solution upon heating.The proposed invention makes possible an effective use of silicon tetrafluoride with maximum conversion of the components thereof into end products, separation of the end products taking place simultaneously with the formation thereof. The yield of the products reaches 92-95 wt. % of their content in the initial raw material.

Abstract: In the regeneration of aqueous waste sulfuric acid by distilling off water often foam is formed which severely interferes with the work-up of the acid. This formation of foam is suppressed by adding alkylsulfonic and/or alkylarylsulfonic acids.

Abstract: The sulfur-containing roasting gases of an ore-roasting plant are cooled in a waste-heat boiler, which produces steam, and then are subjected to particle removal in an electrostatic precipitator or cyclone. The gases are then scrubbed with recirculated aqueous sulfur acid and the gas is then passed through an electrostatic precipitator before being supplied to a plant for the contact process production of sulfur acid. According to the invention, the process is improved by condensing water from the gas in an indirect cooler between the scrubber and the final electrostatic precipitator while water or aqueous sulfur acid is sprayed into the gas upstream of the indirect gas cooler to augment the heat transfer from the gas to the cooled wall thereof.