The shaft structure (7) of the uptake shaft (2) and/or the reaction shaft (1) is carried by buckstay beams (10).

In the gas absorption vessel (1), for example, a raw material gas containing NO is reacted with an absorption solution containing liquefied N2O4 to cause the absorption of NO into the absorption solution.

The concentration vessel (6) can accept the gas supplied from the gas absorption vessel (1) to alter the temperature and/or the pressure of the gas.

Disclosed is an apparatus for purification of a nitrogen oxide comprising a gas absorption vessel (1) and a concentration vessel (6).