REMOVING METHOD AND DEVICE OF NITROGEN OXIDE

摘要

PROBLEM TO BE SOLVED: To improve the NOx removing performance of denitrifying bacteria by removing sodium ion and sulfate ion in an absorption liquid after absorption of nitrogen oxides and before bringing the liquid into contact with denitrifying bacteria. SOLUTION: A make-up water is supplied to an absorption tower 6, and specified amts. of Na2 S2 O3 and Na2 SO3 are supplied to the water to prepare NOx absorption liquid. When a gas to be treated containing NO2 is subjected to gas-liquid contact with the NOx absorption liquid 5a in a packed layer 9 of the absorption tower 6, NO2 gas is dissolved and ionized into NO2 <-> and the liquid is recovered in a liquid reservoir 11. In the NOx absorption liquid 5a in the reservoir 11, Na<+> , S2 O3 <2-> , SO3 <2-> and SO4 <2-> are also dissolved. Then a part of the NOx absorption liquid 5a in the reservoir 11 is discharged to pass through an electrolytic dialysis bath 12 to remove Na<+> by electrolytic dialysis. Then the liquid is made pass through a desulfurizing crystallizing tank 18 to remove SO4 <2-> . The liquid after these treatments is introduced through a reservoir tank 21 into a denitrification tank 24 filled with sulfur-oxidizing and denitrifying bacteria 25, where NO2 <-> is converted into N2 26 by the sulfur- oxidizing and denitrifying bacteria. Then the liquid is discharged.