Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1990-01-09
1991-11-12
Heller, Gregory A.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
423393, C01B 2100, C01B 2140, C01B 2144, C01B 2146
Patent
active
050646257
ABSTRACT:
In a process for the removal of nitrogen oxides (NO.sub.x) from pretreated flue gases having a nitrogen oxide content which is low by means of a multi-stage washing process employing a nitric acid (HNO.sub.3) solution to which is added hydrogen peroxide (H.sub.2 O.sub.2), the process including a first stage in which the pretreated flue gases are received and contacted with nitric acid (HNO.sub.3) vapor to at least partially oxidize nitrogen monoxide (NO) present in the pretreated flue gases to nitrogen dioxide (NO.sub.2) and result in a first stage flue gas, and a second stage in which the first stage flue gas in received and washed with an aqueous nitric acid (HNO.sub.3) solution to which is added H.sub.2 O.sub.2 to remove nitrogen dioxide (NO.sub.2) and any remaining nitrogen monoxide (NO) from the first stage flue gas and result in a second stage flue gas, wherein the pretreated flue gases have been treated to free the flue gases of contaminants including at least one of sulfur dioxide (SO.sub.2), hydrogen chloride (HCl) and hydrogen fluoride (HF), which contaminants are at least one of H.sub.2 O.sub.2 --decomposing or corrosive, and have been treated to free the flue gases of solid particles, the improvement including: adding to the first stage heat sufficient to prevent H.sub.2 O condensation from the first stage flue gas; decontaminating the diluted nitric acid (HNO.sub.3) generated in the second stage when the nitrogen oxide content of the flue gas is above a defined level by, prior to the second stage, concentrating the nitrogen oxide in an absorption process; and providing a third stage in which the second stage flue gas is received and washed with a diluted, aqueous nitric acid (HNO.sub.3) solution to remove any remaining nitric acid (HNO.sub.3) vapor from the second stage flue gas.
REFERENCES:
patent: 4309396 (1982-01-01), Herbrechtsmeyer
patent: 4341747 (1982-01-01), Downey
patent: 4603036 (1986-07-01), Botton et al.
patent: 4663135 (1987-05-01), Miller
Ullmann, 1964 Edition, vol. 15, "Salpetersaure", pp. 22-25.
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