Regarding the fractional distillation tower in air separation

Search on Baidu. . You know, it’s actually just knowledge related to the principle of distillation. .

A fractionation tower is essentially a distillation tower; the distillation of air relies on the different volatilities of its various components, with liquid air being subjected to repeated processes of partial evaporation and partial condensation in order to separate these components. When an oxygen-nitrogen mixture at its condensation temperature passes through an oxygen-nitrogen liquid at a lower temperature, heat and mass exchange occur between the gas phase and the liquid phase; part of the gas condenses into liquid, releasing latent heat of condensation, while the liquid evaporates to some extent due to the absorption of this latent heat. In a column, as the gas passes through the tray layers from bottom to top, the concentration of the low-boiling-point component increases continuously; as long as there are enough trays, a high-purity form of this low-boiling-point component can be obtained at the top of the column. At the same time, the liquid flows through the tray layers from top to bottom, and the concentration of the high-boiling-point component increases continuously; as long as there are enough trays, a high-purity form of this high-boiling-point component can be obtained at the bottom of the tower.

Isn’t it also divided into upper tower and lower tower inside? Does anyone know anything about its structure?

In China, tray towers are generally used in the lower section of the tower, while packed towers are used in the upper section; the trays consist of perforated plates, overflow trays, and non-perforated plates； Packed towers are divided into three types of packing: random packing and structured packing, with liquid collectors and redistributors between each layer of packing.

It’s much better now! No result! Could some expert give some advice?

3L explained it in quite detail; that’s good.

When is wealth always a problem? :)

Who has a diagram of the internal structure of a distillation tower? Please share it. Thank you!

The distillation column of air separation consists of a lower column and an upper column, which utilize the different boiling points of nitrogen and oxygen to carry out fractional separation. Part of the air coming from the adsorber enters the low-pressure main cooler and then goes into the lower column; another part is further compressed by a booster pump and then divided into two streams. One stream enters the high-pressure main cooler, expands, and then reaches the bottom of the lower column, while the other stream is pressurized further by the end stage of the booster pump, cooled, and then enters the high-pressure heat exchanger before being throttled and entering the lower column. The rising gas in the lower column sees its nitrogen content increase as it comes into contact with the reflux liquid. The reflux liquid nitrogen required comes from the condensation evaporator at the top of the lower column; within the main cooler, nitrogen is vaporized while oxygen is condensed.

The main tower is divided into an upper tower and a lower tower. The upper and lower towers are separated by a condensation evaporator, also known as the main cooler. The main cooler is connected to the upper tower. The upper tower features packing, with the packing arranged perpendicularly to each other to facilitate heat exchange between vapor and liquid as well as ensure even distribution of the liquid within the packing; therefore, high precision in terms of verticality is not required for the upper tower. The main cooler has a plate-fin structure, available in fully submerged or semi-submerged types, with fully submerged types being commonly used in medium-pressure oxygen generators. The lower tower uses a tray structure, which requires higher levels of vertical precision, typically around 0.5 per thousand, to ensure even distribution of the liquid over the trays; otherwise, issues such as uneven liquid distribution and substandard purity can occur. Both the crude argon tower and the refined argon tower have a packing-based structure. In large-scale air separation units, the crude argon tower is usually installed in two parts to prevent the overall height of the unit from becoming too great. The crude argon tower section 1 does not contain any heat exchange devices such as condensers, while section 2 of the crude argon tower has a condenser at the top, an evaporator at the bottom, and packing in between. The refined argon tower has a structure similar to that of crude argon tower section 2. During operation, the conditions in the main tower determine everything; once the main tower is stable, subsequent operations become much easier.