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: 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: This invention relates to an arrangement for separating for films, droplets and sprays from pipe-borne gas flows wherein a pipe is provided with a cross-sectional constriction adapted to accelerate the gas flow in the pipe and annular stripping slot having an annular baffle surface and communicating with a collecting trap, the annular baffle surface being adapted to receive the liquid-containing gas flow and to cause the flow to pass into the collecting trap.

Abstract: In the removal of water from a gas by contact with sulfuric acid, the improvement which comprises supplying the sulfuric acid in finely divided form having a surface of about 10.sup.4 to 10.sup.7 m.sup.2 /h at a concentration of about 95 to 99% and a temperature of about 35.degree. to 80.degree. C and with a contact time of about 0.2 to 2 seconds, whereby the residual moisture content of the gas is reduced to about 30 to 250 mg of H.sub.2 O/Nm.sup.3. Preferably the sulfuric acid is sprayed through a constriction into a vessel through which the gas is passed. The large sulfuric acid surface area permits high levels of dehydration to be achieved with far less sulfuric acid than heretofore believed possible and with small vessels and minimal contact times. Contact may be effected serially in several stages with the spent acids combined, brought up to initial concentration and recirculated.

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.

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.