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 method of treating a spent oxidizing acid is provided comprising the steps of contacting a spent acid containing peroxy acids of sulfur with a quantity of SO.sub.2 in excess of an equilibrium quantity required to convert the peroxy acids to sulfuric acid. The excess SO.sub.2 is catalytically converted to SO.sub.3, and the SO.sub.3 is absorbed into the sulfuric acid stream essentially free of H.sub.2SO.sub.5 and H.sub.2O.sub.2 to make product sulfuric acid.

A method of treating a spent oxidizing acid is provided comprising the steps of contacting a spent acid containing peroxy acids of sulfur with a quantity of SO.sub.2 in excess of an equilibrium quantity required to convert the peroxy acids to sulfuric acid. The excess SO.sub.2 is catalytically converted to SO.sub.3, and the SO.sub.3 is absorbed into the sulfuric acid stream essentially free of H.sub.2SO.sub.5 and H.sub.2O.sub.2 to make product sulfuric acid.

In a converter for the catalytic oxidation of SO.sub.2 to SO.sub.3 in a sulfuric acid plant, which comprises a boiler section for the cooling of process gas between catalytic layers (beds), one or more water tube boilers (inter-bed boilers) having horizontal or slightly sloped tubes are used to cool the process gas between the catalytic layers (beds) in the converter. Each water tube boiler is provided with a process gas side bypass to control the temperature to the downstream catalyst layer.

In a converter for the catalytic oxidation of SO.sub.2 to SO.sub.3 in a sulfuric acid plant, which comprises a boiler section for the cooling of process gas between catalytic layers (beds), one or more water tube boilers (inter-bed boilers) having horizontal or slightly sloped tubes are used to cool the process gas between the catalytic layers (beds) in the converter. Each water tube boiler is provided with a process gas side bypass to control the temperature to the downstream catalyst layer.

A method and system for cooling sulfuric acid aqueous solutions (H.sub.2SO.sub.4) belonging to the field of chemical processes, which is part of a contact process for production of sulfuric acid with or without energy recovery. The method comprises absorption of SO.sub.3, which produces heated concentrated sulfuric acid and indirectly cooling the hot acid. The method uses a sulfuric acid-inert coolant. A cooling step comprises an intermediate indirect acid-fluid cooling and a second fluid-water or fluid indirect cooling stepthird fluid, wherein when the process is of the type with energy recovery. A third step includes energy recovery, steam generation. A system to perform the method, which works next to the SO.sub.3 absorption tower comprises an acid cooling loop consisting of an intermediate acid-fluid heat exchanger; a second fluid-water heat exchanger, and when the process is of the type with energy recovery, said equipment further includes a steam generation boiler.

A method and system for cooling sulfuric acid aqueous solutions (H.sub.2SO.sub.4) belonging to the field of chemical processes, which is part of a contact process for production of sulfuric acid with or without energy recovery. The method comprises absorption of SO.sub.3, which produces heated concentrated sulfuric acid and indirectly cooling the hot acid. The method uses a sulfuric acid-inert coolant. A cooling step comprises an intermediate indirect acid-fluid cooling and a second fluid-water or fluid indirect cooling stepthird fluid, wherein when the process is of the type with energy recovery. A third step includes energy recovery, steam generation. A system to perform the method, which works next to the SO.sub.3 absorption tower comprises an acid cooling loop consisting of an intermediate acid-fluid heat exchanger; a second fluid-water heat exchanger, and when the process is of the type with energy recovery, said equipment further includes a steam generation boiler.

A process for preparing sulfuric acid may involve oxidizing sulfur to sulfur dioxide by way of dried air in a first oxidation stage. The sulfur dioxide may then be oxidized to sulfur trioxide in a second oxidation stage. The sulfur trioxide may be absorbed by sulfuric acid in at least one absorption stage. Further, heated sulfuric acid may be drawn off from the absorption stage and used for generating steam. Process gas from an intermediate absorption stage may be recycled to the second oxidation stage and, in some cases, a final absorption stage after the process gas flows through the second oxidation stage.

A process plant for production of sulfuric acid from a process gas comprising SO2, including a process gas inlet, a first SO2 converter having an inlet and an outlet, a first condenser having a gas inlet, a gas outlet and a liquid outlet, a gas mixing device having a first inlet, a second inlet and an outlet, a process gas heater having an inlet and an outlet, a second SO2 converter having an inlet and an outlet, a second condenser having a gas inlet, a gas outlet and a liquid outlet, one or more means for cooling and storage of sulfuric acid and a purified process gas outlet.

A process plant for production of sulfuric acid from a process gas comprising SO2, including a process gas inlet, a first SO2 converter having an inlet and an outlet, a first condenser having a gas inlet, a gas outlet and a liquid outlet, a gas mixing device having a first inlet, a second inlet and an outlet, a process gas heater having an inlet and an outlet, a second SO2 converter having an inlet and an outlet, a second condenser having a gas inlet, a gas outlet and a liquid outlet, one or more means for cooling and storage of sulfuric acid and a purified process gas outlet.