US 12,441,614 B2
Method of cleaning an apparatus used in the concentration of a mineral acid
Bernd Pennemann, Bergisch Gladbach (DE); and Kameh Tajvidi, Neuss (DE)
Assigned to Covestro Deutschland AG, Leverkusen (DE)
Appl. No. 17/783,375
Filed by Covestro Intellectual Property GmbH & Co. KG, Leverkusen (DE)
PCT Filed Dec. 16, 2020, PCT No. PCT/EP2020/086459
§ 371(c)(1), (2) Date Jun. 8, 2022,
PCT Pub. No. WO2021/122773, PCT Pub. Date Jun. 24, 2021.
Claims priority of application No. 19217596 (EP), filed on Dec. 18, 2019.
Prior Publication US 2023/0016848 A1, Jan. 19, 2023
Int. Cl. B08B 3/08 (2006.01); B01B 1/00 (2006.01); B01D 3/14 (2006.01); B01D 53/26 (2006.01); B01D 53/28 (2006.01); C01B 17/88 (2006.01); C01B 21/44 (2006.01); C07C 201/08 (2006.01); F28G 9/00 (2006.01)
CPC C01B 17/88 (2013.01) [B01B 1/005 (2013.01); B01D 3/148 (2013.01); B01D 53/263 (2013.01); B01D 53/28 (2013.01); C01B 21/44 (2013.01); C07C 201/08 (2013.01); F28G 9/00 (2013.01)] 15 Claims
OG exemplary drawing
 
1. 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.