The modified alkali absorption method NOX in the nitric acid waste gas is absorbed by the absorption tower by the Na2CO3 solution to form a neutralization liquid containing sodium nitrite and sodium nitrate.The neutralized liquid is evaporated, crystallized and separated to obtain a sodium nitrite product. The separated mother liquor of sodium nitrite is converted with dilute nitric acid and oxidized to sodium nitrate. The sodium nitrite product is obtained by evaporation, crystallization and separation.
Selective catalytic-reduction method. The method is a selective reduction reaction of ammonia with nitrogen oxides in the exhaust gas under the action of a copper-chromium catalyst to remove nitrogen oxides in the exhaust gas.
