The main tower is divided into upper tower and lower tower. The upper tower and the lower tower are divided into two parts by the condensing evaporator, namely, the main cooling, which is connected with the upper tower. The upper column is filled with packing, and the direction of packing is perpendicular to each other, which is conducive to the heat exchange between steam and liquid and the uniform distribution of liquid in the packing. Therefore, the verticality of the upper tower is not very high. The plate fin structure is mainly used for cooling, which can be divided into full immersion type and semi immersion type.

The ordinary medium pressure oxygen generator is full immersion type, and the lower tower structure is plate tower, which has strict requirements for perpendicularity, which is generally about 0.5 per thousand, to ensure that liquid and liquid are evenly distributed on the tray, otherwise, the air separation unit is easy to be too high. The crude argon tower and refined argon tower are of mixed structure. The coarse argon tower of large-scale air separation is generally separately installed to avoid high air separation unit and no condenser in crude argon tower In the unit, the upper part of crude argon II is the condenser, the lower part is the evaporator, and the middle part is the packing. The structure of the refined argon tower is the same as that of the crude argon II. During operation, the working condition of the main tower determines everything. The main tower is stable and the follow-up work is simple.