Abstract: A method for removing As, or As and Sb and/or Bi wherein acidic solution of sulfuric acid such as a copper electrolyte of having a free sulfuric acid concentration of less than 700g./l. and containing at least arsenic among arsenic, antimony and bismuth as impurities is warmed to be above 50.degree. C. or preferably above 60.degree. C. with the addition of H.sub.3 AsO.sub.4 in advance as required, one or a mixture of both of Sb.sub.2 O.sub.3 and Bi.sub.2 O.sub.3 preferably kneaded with water or the added solution is added to and mixed with the solution and the produced precipitate is separated to discharge the impurities out of the solution.

Abstract: A corrosive liquid such as sulphuric acid is concentrated using two spaced concentric tubes. A film of the acid flows down the inside of the inner tube and hot flue gases contact the outside of the outer tube. Advantageously, the inner tube transmits radiant energy, e.g. is made of quartz, so the outer tube heats the inner tube by radiation. This absence of mechanical stress on the inner tube increases its life. The water vapor is taken off at the top of the inner tube and concentrated solution at the bottom. If desired, the tubes could be reversed with the flue gases going through the inner tube and the outer tube being of quartz with the liquid flowing on its outside.

Abstract: A process for the recovery of sulfuric acid from waste sulfuric acid containing iron sulfate and from solid iron sulfate of high water content of crystallization which consists essentially of:A. concentrating waste sulfuric acid to an acid concentration of 25-55 weight percent, based upon the suspension, by removing water therefrom;B. mixing the concentrated acid of Step A with recycled concentrated sulfuric acid obtained from Step E to form a resultant acid mixture of acid concentration of 30-65 weight percent, based upon the suspension;C. adding said solid iron sulfate of high water content of crystallization to the acid mixture of Step B thereby obtaining iron sulfate of low water content of crystallization;D. separating the iron sulfate of low water content from the resultant sulfuric acid solution of Step C;E. concentrating the separated sulfuric acid solution of Step D to an acid concentration of 45-70 weight percent, based on salt-free acid, and recycling at least a portion thereof to Step B; andF.

Abstract: The invention provides a process for the regeneration of dilute sulfuric acid containing organic impurities and possibly also inorganic salt in several steps. In the first step, the dilute acid is concentrated by indirect heat exchange with the vapors of the second step, and in the second step it is concentrated by direct heat exchange with a countercurrent mixture of steam and acid vapors coming from a third step. In this third step, the acid discharged from the second step is mixed in direct heat exchange with superheated steam. The regenerated sulfuric acid is separated from this mixture and the remaining steam/vapor mixture is forwarded to the second step. In the case where the dilute acid contains organic substances, an oxidant is added in at least one of these process steps.

Abstract: Mixtures of nitric acid and sulfuric acid containing in excess of 70% sulfuric acid are denitrated by the addition of sufficient sulfur dioxide to such mixtures to convert the nitric acid to gaseous nitrogen oxides and vaporizing them from the solution in which they are formed. The process is particularly valuable for the treatment of spent nitration acids.

Abstract: Process for the recovery of H.sub.2 SO.sub.4 from dilute sulfuric acid solutions containing combined acid sulfates by heating these solutions in the presence of excess ammonium sulfate to a temperature from between about 100.degree. and 160.degree. C. until a concentration of free H.sub.2 SO.sub.4 between 50 and 59% by weight is obtained to precipitate the combined acid sulfates.

Abstract: Spent sulphuric acid, either alongside or mixed with contaminated metal salts such as iron sulphate heptahydrate, is regenerated to fresh acid by countercurrent contact with gases from cleavage of the sulphate salts, such gases containing SO.sub.3 which effects build up of the acid concentration. The built up acid is evaporated in another stage to obtain pure acid. The metal sulphate solids are subjected to high temperature cleavage, generating SO.sub.3 which effects the previous concentration. Cleavage also produces some SO.sub.2 which is converted to SO.sub.3 by wet catalysis.

Abstract: The foam formation arising when aqueous waste sulfuric acid is concentrated can be suppressed by adding aromatic nitro compounds such as nitrobenzene to the acid.

Abstract: The invention comprises a method of wet-cleaning gases containing sulfur dioxide, halogens together with arsenic and/or arsenic compounds obtained in a pyrometallurgical treatment of sulfidic materials. The gases are washed in a diluted sulfuric acid circulating in a closed circuit, from which arsenic is recovered. The gases are then cooled to water condensation whereby the halogens are substantially completely taken up in said condensate and separated. The separated condensate is then discharged to a recipient after precipitation of residual arsenic and neutralization.

Abstract: A multi-stage apparatus suited for concentrating sulphuric acid comprising at least one high temperature stage and one low temperature stage, the high temperature stage including a surrounding wall defining a flue gas channel, means for delivering hot flue gas to said channel, and means for withdrawing from said channel cooled flue gas, the flue gas heating said surrounding wall which in turn imparts heat to material to be heated thereby, the low temperature stage including a heat exchanger with a first flow path for a heating agent and a second flow path for a material to be heated thereby, means for supplying the said second flow path material to be heated, means for withdrawing from said second flow path material after having been heated therein, and means for withdrawing from said first flow path spent heating agent, the means for withdrawing cooled flue gas from said flue channel of said high temperature stage forwarding heat from said cooled flue gas to said first flow path of said low temperature stage

Abstract: The method of preparing sulphuric acid comprises distilling sulphur trioxide with subsequent sublimation condensation by cooling with a coolant having a temperature of from -5.degree. to -15.degree. C. The obtained sulphur trioxide is then treated with sulphuric acid having a concentration in the range of 95 to 96 per cent. The thus prepared sulphuric acid contains impurities in the range of 10.sup.-7 - 10.sup.-8 per cent by weight of cations, and 5.times.10.sup.-5 per cent by weight of anions, SO.sub.3 " in particular.

Abstract: A method of separating sulfuric acid from spent chlorine dioxide generator liquor. The method comprises simultaneously adding to the spent liquor, a water-soluble organic compound selected from the group consisting of alcohols and ketones, and water. The resulting solid is separated to leave an aqueous solution of sulfuric acid. The method is of particular application in acid and salt cake recovery from the effluent of a chlorine dioxide generator operating at an acid normality of between 6 and 11.

Abstract: Production of titanium dioxide which is characterized by recovery of reusable H.sub.2 SO.sub.4, highly pure Fe oxide and hydroxide and fractional recovery of Mn, V and Cr, etc., from FeSO.sub.4. nH.sub.2 O and waste acid of 20 - 40% H.sub.2 SO.sub.4 containing abundant heavy metallic ions, which are by-produced in the production of TiO.sub.2 by dissolution of Ti raw materials such as ilmenite, steel production slag, such as electric furnace slag, convertor slag with H.sub.2 SO.sub.4.

Abstract: An aqueous solution of a mineral acid is freed of dissolved or colloidally dispersed organic matter by admixing to the solution an aldehyde or an aldehyde oligomer and a compound copolymerizable with an aldehyde, allowing a polymerization reaction to occur and separating the resulting polymer. The polymer that forms removes selectively from the solution the said organic matter and any suspended organic matter is also removed. The aldehyde and the compound copolymerizable therewith may be added in the form of a pre-condensate.

Abstract: A method of manufacturing sulfuric acid free of impurities such as mercury by the contact process, which comprises the steps: scrubbing the roasting gas coming out of a mist Cottrell with sulfuric acid having a concentration of 30 to 99% and a temperature of more than 20.degree. C within one or two mercury absorption towers (the drying tower per se may suffice) or further within an additional mercury absorption tower disposed on the outlet side of the main blower; and adding a reagent such as a sulfide, a hydrosulfide compound of alkali metal or alkaline earth metal, hydrogen sulfide, selenium compound, sulfur, etc.

Abstract: Improvement in the method for recovering sulfur values in the form of sulfur dioxide from spent sulfuric acid by decomposing the spent sulfuric acid at elevated temperature in the presence of elemental sulfur to generate a sulfur dioxide-containing gas stream, which involves: (a) introducing the spent sulfuric acid into a pool of molten sulfur maintained at temperature of at least about 250.degree. C. to thereby generate a gaseous stream comprising sulfur dioxide, vaporous elemental sulfur, and water; (b) cooling said gaseous stream to temperature above the melting point of the sulfur but below about 160.degree. C. to condense elemental sulfur therefrom, separating the condensed elemental sulfur and returning it to the pool of molten sulfur; followed by (c) further cooling the gaseous stream from which elemental sulfur has been condensed to condense water therefrom, and separating the condensed water from the gaseous stream.

Abstract: Dilute sulfuric acid contaminated with acetic acid and hydrogen chloride is purified with the resultant formation of concentrated sulfuric acid and acetic acid. To this end, the contaminated sulfuric acid is heated in a first step to at most 60.degree. C under 25-30 mm Hg so as to expel all of the hydrogen chloride together with minor proportions of acetic acid and water. In a second step, the sulfuric acid is heated to at most 165.degree. C under 20-25 mm Hg so as to distil off the bulk of acetic acid together with water. In a third step, the sulfuric acid is cooled down to 60.degree.-90.degree. C, diluted with 10-30 wieght % of water with agitation and while cooling is continued. Following this, the sulfuric acid is heated to 160.degree.-165.degree. C under 20-25 mm Hg and thereby freed from the water and residual acetic acid.

Abstract: Process for transforming water-soluble metal sulfate residue obtained from spent sulfuric acid containing inorganic impurities, such as pickle liquors or acid wastes from hydrometallurgical processes, into substantially water-insoluble form suitable for disposal which comprises introducing the residue into a pool of molten sulfur maintained at temperature of at least about 250.degree. C. to thereby generate a gaseous stream comprising sulfur dioxide and to transform the metal sulfate residue into corresponding reduction products, and recovering sulfur dioxide and reduction products associated with sulfur in solid form suitable for disposal.

Abstract: 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 conversion of a major portion of fluorosulfonic acid to hydrogen fluoride, wherein said hydrogen fluoride is removed from the vacuum digestion zone as a vapor, and wherein the remaining sulfuric acid rich liquid fraction of the spent catalyst is treated with silica-alumina cracking catalyst for removal of most of the remaining residual fluoride compounds for providing a sulfuric acid effluent substantially free of fluoride compounds. The hydrogen fluoride recovered is reacted with sulfur trioxide to form fresh fluorosulfonic acid which is combined with sulfuric acid to provide fresh alkylation catalyst.

Abstract: When distilling or boiling concentrated sulfuric acid in a vessel of gray cast iron the corrosion resistance of the apparatus is improved by using an alloy containing from0.2 to 1.6 % of silicon0 to 0.2 % of phosphorus0.6 to 2.5 % of copper0 to 3.5 % of nickelBesides the usual elements for gray cast iron and a graphite portion in a finely divided form in a pearlitic skeleton.

Abstract: Sulfuric acid is produced from sulfur trioxide-containing humid gases by a process wherein the sulfur trioxide-containing humid gases are directly cooled with aqueous sulfuric acid, sulfuric acid is condensed and the gas is cooled below dew point of the sulfuric acid, and the water not required to form sulfuric acid is discharged as water vapor with the end gases.

Abstract: A method of reducing the sulfate ion and sulfuric acid contamination of waste water in lead-acid battery manufacturing operations and recovery of the lead in salvageable form is provided which comprises neutralizing aqueous sulfuric acid wastes by treatment with waste battery paste containing lead oxide under controlled pH conditions.

Abstract: Finely divided sulfur and an oxygen containing gas are combined and burnt. Finely divided sulfuric acid is introduced into the hot flame gases. The resulting gas containing SO.sub.2, water and oxygen can be processed to pure SO.sub.2.

Abstract: Contaminated sulfuric acid which may contain water, organic compounds and inorganic salts is converted to almost pure concentrated sulfuric acid by passing the acid through a Pauling plant and distilling the concentrated contaminated acid.Addition of nitric acid improves the decomposition of organic compounds and ammonium salts of the contaminated acid.

Abstract: A process for thermally-degrading the thermally-degradable organic matter contained in spent sulfuric acid by condensing steam in the spent acid for a time sufficient to degrade the thermally-degradable organic matter, the steam being at a pressure exceeding the vapor pressure of said spent acid. Treated sulfuric acid is useful in the production of wet process phosphoric acid by a novel process. Spent sulfuric acid containing non-degradable organic matter can be used in a mixture with the treated sulfuric acid.

Abstract: A two step process for concentrating and desalting dilute sulfuric acid including, first indirectly countercurrently contacting and heating the dilute acid with steam from a second step, removing overhead water vapor and withdrawing concentrated acid, and second further concentrating the acid by directly countercurrently contacting and heating the acid with superheated steam, removing overhead steam and additional water vapor, which is used in the first heating step. Acid of a higher concentration is withdrawn and cooled to crystallize and remove salts and the more highly concentrated sulphuric acid recovered.

Abstract: Process for the production of an aliphatic alcohol comprising reacting an olefin having from 2 to 4 carbon atoms with sulfuric acid to form an ester reaction product, diluting said product with water and steam stripping to remove a lower aliphatic alcohol overhead leaving a dilute sulfuric acid solution, concentrating said dilute sulfuric acid solution in a first stage indirect evaporator, recycling the steam generated in this first stage evaporator to the steam stripping step, further concentrating the sulfuric acid solution in a second stage direct heat evaporator to form a concentrated sulfuric acid solution and recycling said concentrated sulfuric acid solution for reaction with fresh olefin feed.

Abstract: 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 remaining sulfuric acid rich fraction of the spent catalyst is reacted with a silica containing material to convert most of the remaining residual hydrogen fluoride to silicon fluoride which is volatilized from the mixture to thereby provide a sulfuric acid effluent free of substantial amounts of fluoride compounds. The hydrogen fluoride recovered is reacted with sulfur trioxide to form fresh fluorosulfonic acid which is combined with sulfuric acid to provide fresh alkylation catalyst.

Abstract: Two-step-process for regenerating dilute sulfuric acid which may contain organic and inorganic impurities such as heavy metal salts. In the first step the impure acid is distilled in vacuo and in the second step concentrated in a Pauling apparatus.

Abstract: Dilute solutions of corrosive products, such as sulphuric or phosphoric acid, are concentrated by pre-concentrating the dilute solution and then introducing the pre-concentrated solution into a tunnel in which it flows in a thin layer over successive cascades while being heated, preferably by indirect radiant heating. An installation for carrying out the process is also described.

Abstract: Process of reducing the bromine content of spent sulfuric acid bromination liquor containing organic impurities by blowing an oxygen containing gas through said sulfuric acid liquor at an elevated temperature at least until substantially all of the organic material in said liquor is oxidized.

Abstract: A method of manufacturing sulfuric acid free of impurities such as mercury by the contact process, which comprises the steps: scrubbing the roasting gas coming out of a mist Cottrell with sulfuric acid having a concentration of 30 to 99% and a temperature of more than 20.degree.C within one or two mercury absorption towers (the drying tower per se may suffice) or further within an additional mercury absorption tower disposed on the outlet side of the main blower; and adding a reagent such as a sulfide, a hydrosulfide compound of alkali metal or alkaline earth metal, hydrogen sulfide, selenium compound, sulfur, etc.

Abstract: Mercury is removed from sulfuric acid by adding finely divided aluminum to the acid, cooling the mixture to a temperature not exceeding about 15.degree.C. and filtering the mixture in from about 1 to about 6 hours.

Abstract: In the processing of a corrosive liquid mixture, such as 50 to 80% aqueous sulfuric acid, by its passage over one surface of a wall of inert heat resistant material, and heating the other surface of said wall, thereby to evaporate from said corrosive liquid mixture the more volatile component thereof, the improvement which comprises heating said wall by contact with an inert liquid material, and heating said inert liquid material indirectly through heat exchange with a normally solid molten material. Desirably the wall of inert material is a pipe surrounded by a molten metal in a first annular jacket and a molten salt in a second annular jacket.