Integrated plants and associated processes for producing ammonia and sulfuric acid have been developed comprising air separation and water electrolysis subsystems and which make surprisingly efficient use of the products from these subsystems (i.e. oxygen and nitrogen from the former and hydrogen and oxygen from the latter). The invention is particularly suitable for use as part of an integrated fertilizer production plant.

A method for preparing an electronic grade sulfuric acid from a waste sulfuric acid solution includes the steps of: performing, in sequence, a concentration treatment, a cracking treatment, and a purification treatment; performing a first oxidation treatment on sulfur dioxide; performing a first absorption treatment and a second oxidization treatment; performing an evaporation treatment; performing a first removal treatment on an acid mist containing metal ions and anion impurities; performing a second absorption treatment; and performing a second removal treatment on residual sulfur dioxide.

In a method for cooling of process gas between catalytic layers or beds in a sulfuric acid plant, in which sulfuric acid is produced from feed gases containing sulfurous components like SO.sub.2, H.sub.2S, CS.sub.2 and COS or liquid feeds like molten sulfur or spent sulfuric acid, one or more boilers, especially water tube boilers, are used instead of conventional steam superheaters to cool the process gas between the catalytic beds in the SO.sub.2 converter of the plant. Thereby a less complicated and more cost efficient heat exchanger layout is obtained.

In a method for cooling of process gas between catalytic layers or beds in a sulfuric acid plant, in which sulfuric acid is produced from feed gases containing sulfurous components like SO.sub.2, H.sub.2S, CS.sub.2 and COS or liquid feeds like molten sulfur or spent sulfuric acid, one or more boilers, especially water tube boilers, are used instead of conventional steam superheaters to cool the process gas between the catalytic beds in the SO.sub.2 converter of the plant. Thereby a less complicated and more cost efficient heat exchanger layout is obtained.

A method for preparing an electronic grade sulfuric acid from a waste sulfuric acid solution includes the steps of: performing, in sequence, a concentration treatment, a cracking treatment, and a purification treatment; performing a first oxidation treatment on sulfur dioxide; performing a first absorption treatment and a second oxidization treatment; performing an evaporation treatment; performing a first removal treatment on an acid mist containing metal ions and anion impurities; performing a second absorption treatment; and performing a second removal treatment on residual sulfur dioxide.

A method for treating a spent oxidizing acid which contains at least one of H.sub.2O.sub.2 and one or more peroxy acids of sulfur comprising contacting the spent oxidizing acid with a quantity of SO.sub.2 in excess of an equilibrium quantity required to convert the H.sub.2O.sub.2 and peroxy acids of sulfur to sulfuric acid.

A process for the oxidation of hydrogen sulfide to sulfur trioxide with subsequent sulfur trioxide removal comprises oxidizing hydrogen sulfide to sulfur trioxide in at least one catalyst-containing reactor and feeding the effluent from the last reactor to a candle filter unit for SO.sub.3 removal, where it is mixed with an injected alkaline sorbent slurry or powder to form an alkali sulfate and a hot clean gas. Preferably the oxidation is done in two reactors, the first oxidizing H.sub.2S to SO.sub.2 over a monolith type catalyst and the second oxidizing SO.sub.2 to SO.sub.3 over a VK type catalyst.

A process for the oxidation of hydrogen sulfide to sulfur trioxide with subsequent sulfur trioxide removal comprises oxidizing hydrogen sulfide to sulfur trioxide in at least one catalyst-containing reactor and feeding the effluent from the last reactor to a candle filter unit for SO.sub.3 removal, where it is mixed with an injected alkaline sorbent slurry or powder to form an alkali sulfate and a hot clean gas. Preferably the oxidation is done in two reactors, the first oxidizing H.sub.2S to SO.sub.2 over a monolith type catalyst and the second oxidizing SO.sub.2 to SO.sub.3 over a VK type catalyst.

The present invention relates to a method for the catalytic removal of sulfur dioxide from waste gases in two reactors, wherein the first reactor is charged with an activated carbon catalyst. The method comprises: a. provision of a waste gas with a water content of less than 1 g H.sub.2O/Nm.sup.3 and an SO.sub.2 content of at least 5 ppm, b. introduction of the waste gases into a first reactor, c. catalytic conversion of the SO.sub.2 into gaseous SO.sub.3 in the first reactor by the activated carbon catalyst, wherein catalytic conversion on the activated carbon catalyst proceeds at a temperature of below 100° C., d. introduction of the prepurified waste gases from the first reactor into a second reactor, e. conversion of the SO.sub.3 with water into H.sub.2SO.sub.4 in the second reactor.

The present invention relates to a method for the catalytic removal of sulfur dioxide from waste gases in two reactors, wherein the first reactor is charged with an activated carbon catalyst. The method comprises: a. provision of a waste gas with a water content of less than 1 g H.sub.2O/Nm.sup.3 and an SO.sub.2 content of at least 5 ppm, b. introduction of the waste gases into a first reactor, c. catalytic conversion of the SO.sub.2 into gaseous SO.sub.3 in the first reactor by the activated carbon catalyst, wherein catalytic conversion on the activated carbon catalyst proceeds at a temperature of below 100° C., d. introduction of the prepurified waste gases from the first reactor into a second reactor, e. conversion of the SO.sub.3 with water into H.sub.2SO.sub.4 in the second reactor.