Process for the purification of industrial gases or waste gases
AssigneeDegussa AG
InventorsJoachim Fischer, Helmut Knorre
Life of this patent
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Abstract
In purifying gas wash waters containing cyanide with formaldehyde, the exact dosing of formaldehyde presents a problem, especially with strongly fluctuating cyanide contents. By continuous potentiometric measurement in a side stream which is regulated to a pH of 7 to 10, while the pH of the main stream remains unchanged, the formaldehyde can be adjusted safely to any cyanide content.
Claims22
In a process for the purification of industrial gas or waste gases which contain hydrogen cyanide by a circulating wash with water and formaldehyde and a simultaneous oxidative treatment or a subsequent oxidative treatment of the circulating water removed from the circuit the improvement comprising dosing the formaldehyde into the gas wash circuit before the gas washer and controlling the amount of formaldehyde added so that it is stoichiometrically equal to the cyanide content by continuously measuring the redox potential with a pair of electrode consisting essentially of a noble metal and a reference electrode in a measuring side stream branched off after the washer and controlling the pH of the side stream to a pH between 7 and 1 by dosing in alkali or acid in the presence of at least 1 ppb of silver ions.
Dependencies are inferred from the claim text.