More sieve plate towers are used for the lower tower from 15000 to 50000 grades. The diameter tower with circulating tray below 15000 grades has advantages (the liquid flow is longer than convection, but the manufacturing is complex). The convection tower below 30000 grades is used more, the large tower with four overflow streams above 30000 grades has advantages, and the packed tower has low energy consumption.

The adsorbers used in the purification system include vertical axial flow, horizontal double bed and vertical radial flow. Vertical axial flow is mainly used for supporting air separation equipment below 10000 grade (with a diameter of 4.6m). The bed thickness is 1550 ∽ 2300mm. It can be arranged in double layers and single layers. The vertical axial flow adsorber has the best air distribution.