Method of cleaning an apparatus used in the concentration of a mineral acid
AssigneeCovestro Deutschland AG
InventorsBernd Pennemann, Kameh Tajvidi
Life of this patent
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Abstract
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.
Claims15
A method for preparing and using an apparatus comprising an acid-resistant device,
- wherein the acid-resistant device has a coating comprising steel enamel, silicon carbide, glass, tantalum, niobium, a perfluorinated polymer, or a composite of two or more thereof,
- or
- wherein the acid-resistant device is made of one of steel enamel, silicon carbide, glass, tantalum, niobium, a perfluorinated polymer, or a composite of two or more thereof,
- the method comprising:
- (a) flushing the acid-resistant device with an aqueous alkali metal hydroxide solution having a concentration by mass of alkali metal 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;
- and then subsequently
- (b) using the apparatus comprising the acid-resistant device flushed in step (a) in a process of concentrating a mineral acid by evaporation of water, wherein said process comprises contacting the acid-resistant device with the mineral acid during the concentrating of the mineral acid or wherein said process comprises contacting the acid-resistant device with the mineral acid while the mineral acid has a concentration that was increased as a result of said concentrating of the mineral acid.
Dependencies are inferred from the claim text.