Method for reducing nitrogen oxide in tail gas in nitrate production

The invention discloses a method for reducing nitrogen oxides in tail gas in nitrate production, which comprises the following steps of: washing heated sodium nitrite mother liquor in a conversion washing cooling tower; and the washed sodium nitrite mother liquor and nitric acid react at the lower part of the conversion washing cooling tower to generate converted gas. The converted gas is washed by sodium nitrite mother liquor, cooled by cooling water and physically separated and then enters the bottom of a converted gas isothermal oxidation tower from the top of a conversion washing cooling tower to be mixed with secondary air, so that NOx gas is further oxidized; nOx gas comes out from the top of the converted gas isothermal oxidation tower and enters a plurality of alkali absorption tower groups through a converted gas regulating valve to enter an alkali absorption process, and alkali-absorbed NOx tail gas finally enters a tail gas treatment process. According to the method, the nitrogen oxide recovery rat