A recycling system and method for treating waste sulfuric acid solution containing hydrogen peroxide are provided. The recycling system includes a preheat subsystem, a reaction cycle control subsystem, and a cooling subsystem. The preheat subsystem heats the waste sulfuric acid solution to a target temperature through a cyclic heat exchange method and then further raises the temperature using an acid-resistant heater. The reaction cycle control subsystem monitors the sulfuric acid concentration, hydrogen peroxide content, reaction temperature, and nitrate compound content of the waste sulfuric acid solution to determine the amount and mode of addition of a nitrate-containing promoter. The cooling subsystem includes a first cooling heat exchanger to transfer waste heat to the initial waste sulfuric acid solution and a second cooling heat exchanger to reduce the sulfuric acid to a safe temperature, thereby avoiding overheating.

The invention relates to an apparatus for the continuous concentration of corrosive liquids, the apparatus comprising a fluid system with a regenerative heat exchanger for preheating the dilute liquid and a vapour line to supply solvent vapour, which has been separated from the heated liquid in a main separator, to the hot side of the regenerative heat exchanger as a heat source. The invention further relates to a method for continuously concentrating corrosive liquids, wherein the system pressure is greater than 1 bar.

The invention relates to an apparatus for the continuous concentration of corrosive liquids, the apparatus comprising a fluid system with a regenerative heat exchanger for preheating the dilute liquid and a vapour line to supply solvent vapour, which has been separated from the heated liquid in a main separator, to the hot side of the regenerative heat exchanger as a heat source. The invention further relates to a method for continuously concentrating corrosive liquids, wherein the system pressure is greater than 1 bar.

The present invention relates to a method for preparing an apparatus (or a plant comprising a plurality of apparatuses), for example a heat exchanger, a vaporizer or a distillation column, for use in a process (in particular a continuously operated process) for concentrating a mineral acid by evaporation of water, wherein the apparatus or the plant comprises (at least) a device which is resistant to the mineral acid and the device is flushed with an aqueous alkali metal hydroxide solution having a concentration by mass of alkali metal hydroxide in the range from 1% to 30% at a temperature in the range from 40 C. to 90 C. for a time of from 2 hours to 7 days.

The present invention relates to a method for preparing an apparatus (or a plant comprising a plurality of apparatuses), for example a heat exchanger, a vaporizer or a distillation column, for use in a process (in particular a continuously operated process) for concentrating a mineral acid by evaporation of water, wherein the apparatus or the plant comprises (at least) a device which is resistant to the mineral acid and the device is flushed with an aqueous alkali metal hydroxide solution having a concentration by mass of alkali metal hydroxide in the range from 1% to 30% at a temperature in the range from 40 C. to 90 C. for a time of from 2 hours to 7 days.

A method for fractionating a sulfuric acid process stream having at least 1 wt % sulfuric acid, using a treatment system comprising three filtration assemblies each having membranes that are suitable to pass less than 10% salt in a standard test such that average passage of sulfuric acid from the first and third filtration assemblies is less than 30% and average passage of sulfuric acid from second filtration assembly is more than 70%. The system produces a fraction of the stream with a pH between 4 and 10, and a second fraction that contains at least 20 weight percent of sulfuric acid.

A method for fractionating a sulfuric acid process stream having at least 1 wt % sulfuric acid, using a treatment system comprising three filtration assemblies each having membranes that are suitable to pass less than 10% salt in a standard test such that average passage of sulfuric acid from the first and third filtration assemblies is less than 30% and average passage of sulfuric acid from second filtration assembly is more than 70%. The system produces a fraction of the stream with a pH between 4 and 10, and a second fraction that contains at least 20 weight percent of sulfuric acid.

Process for the removal of particulate matter from an aqueous stream containing a concentrated acid, preferably concentrated sulfuric acid, the process including mechanical filtration by passing the aqueous stream through a filter unit, the filter unit including a metallic, ceramic or polymeric filter, or a filter including a filter aid on a septum. The aqueous stream is the exit stream of a sulfuric acid condenser, optionally the exit stream of a sulfuric acid concentrator arranged downstream the sulfuric acid condenser.

Process for the removal of particulate matter from an aqueous stream containing a concentrated acid, preferably concentrated sulfuric acid, the process including mechanical filtration by passing the aqueous stream through a filter unit, the filter unit including a metallic, ceramic or polymeric filter, or a filter including a filter aid on a septum. The aqueous stream is the exit stream of a sulfuric acid condenser, optionally the exit stream of a sulfuric acid concentrator arranged downstream the sulfuric acid condenser.