The invention describes a process for producing sulfuric acid by catalytic oxidation of SO.sub.2 to SO.sub.3 and subsequent absorption of the SO.sub.3 in sulfuric acid, wherein the SO.sub.3 is introduced into a first absorption stage (primary absorber) and at least partly absorbed there in concentrated sulfuric acid, wherein the SO.sub.3 not absorbed in the first absorption stage is supplied to a second absorption stage (secondary absorber) for the further absorption in concentrated sulfuric acid, and wherein the sulfuric acid is cooled after passing through the two absorption stages. The cooling of the sulfuric acid is effected in at least two heat exchangers connected in parallel, wherein one of the at least two heat exchangers is operated as partial evaporator and is cooled with boiler feed water/steam and the other one is cooled with cooling water and operated as pure acid cooler.

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.

Commercial production of sulfuric acid is almost entirely accomplished nowadays using the contact process. And the trend is to increase conversion efficiency and reduce emissions of unconverted sulfur dioxide. By using a special combination of contact catalyst beds, a single contact single absorption (SCSA) system can be engineered to achieve the conversion and emission capabilities of conventional double contact double absorption systems. Thus, the complexity and cost of incorporating a second absorption tower and associated heat exchanger in the system can be omitted. In the SCSA system, the initial catalyst bed or beds comprise vanadium oxide catalyst and the last catalyst bed or beds comprise platinum catalyst operating at a much lower temperature than the initial beds.

The invention relates to a continuous process for purifying a gas containing 60-99 percent SO.sub.2 (sulfur dioxide) by volume and 1 to 40 percent steam by volume, followed by synthesis of SO.sub.3 (sulfur trioxide) without first drying the gas, and to an apparatus for carrying out said method.

The invention relates to a continuous process for purifying a gas containing 60-99 percent SO.sub.2 (sulfur dioxide) by volume and 1 to 40 percent steam by volume, followed by synthesis of SO.sub.3 (sulfur trioxide) without first drying the gas, and to an apparatus for carrying out said method.

Methods and systems for producing sulfuric acid and/or sulfur trioxide, which may include contacting a first stream that includes oxygen and a second stream that includes sulfur to produce a third stream that includes sulfur dioxide, and subjecting the third stream to an oxidation reaction to produce a fourth stream that includes sulfur trioxide. The contacting of the first and second streams may include contacting a molar amount of oxygen that exceeds a molar amount of sulfur.

Methods and systems for producing sulfuric acid and/or sulfur trioxide, which may include contacting a first stream that includes oxygen and a second stream that includes sulfur to produce a third stream that includes sulfur dioxide, and subjecting the third stream to an oxidation reaction to produce a fourth stream that includes sulfur trioxide. The contacting of the first and second streams may include contacting a molar amount of oxygen that exceeds a molar amount of sulfur.

This desulfurization device is for desulfurizing a discharge gas which contains sulfur oxides and which was discharged from a device for sulfuric acid production that includes a concentrated-sulfuric-acid production step in which sulfur trioxide gas obtained by oxidizing sulfur dioxide gas is absorbed in an aqueous sulfuric acid solution while supplying water thereto to thereby produce sulfuric acid having a concentration as high as 90 wt % or more but less than 99 wt %, the desulfurization device comprising: a desulfurization tower in which the sulfur oxides are removed from the discharge gas and, simultaneously therewith, dilute sulfuric acid is formed from the sulfur oxides; and a dilute sulfuric acid mixer which, in the concentrated-sulfuric-acid production step, mixes the dilute sulfuric acid with the aqueous sulfuric acid solution.

Methods and systems for producing sulfuric acid and/or sulfur trioxide, which may include contacting a first stream that includes oxygen and a second stream that includes sulfur to produce a third stream that includes sulfur dioxide, and subjecting the third stream to an oxidation reaction to produce a fourth stream that includes sulfur trioxide. The contacting of the first and second streams may include contacting a molar amount of oxygen that exceeds a molar amount of sulfur.

Methods and systems for producing sulfuric acid and/or sulfur trioxide, which may include contacting a first stream that includes oxygen and a second stream that includes sulfur to produce a third stream that includes sulfur dioxide, and subjecting the third stream to an oxidation reaction to produce a fourth stream that includes sulfur trioxide. The contacting of the first and second streams may include contacting a molar amount of oxygen that exceeds a molar amount of sulfur.