The classification and editing of towers are divided into two categories: plate towers and packed towers according to their structure.

There are a certain number of trays in the plate tower, and gas is transferred to the liquid layer on the trays in the form of bubbles or jets. According to the gas-liquid operation state, it can be divided into bubble trays such as float valves, bubble caps, sieve plates, and jet trays such as mesh and tongue shaped trays. It can also be divided into overflow tray (bubble cap, etc.) and flow-through tray (flow-through grating and flow-through sieve plate, etc.) based on the presence or absence of downcomers.

There is a certain height of packing inside the packed tower, and the liquid flows down along the packing from top to bottom, while the gas contacts the liquid film in reverse flow from bottom to top for material transfer. Commonly used in distillation, water absorption, extraction and other operations. According to the structural characteristics, it can be divided into random packing (granular packing such as step rings and ball rings) and regular packing (mesh corrugated packing and corrugated packing)

The structural characteristics of a packed tower. A packed tower is a mass transfer device that uses the packing inside the tower as a gas-liquid two-phase contact component. The body of the packed tower is a vertical cylinder, with a packing support plate installed at the bottom. The packing is placed on the support plate in a disorderly or integrated manner. Install a packing pressure plate above the packing to prevent it from being blown by the rising airflow. The liquid is sprayed onto the packing from the top of the tower through a liquid distributor and flows down along the surface of the packing. Gas is sent from the bottom of the tower and distributed through a gas distribution device (small diameter towers generally do not have gas distribution devices). It then flows continuously in reverse flow with the liquid through the gaps in the packing layer. On the surface of the packing, the gas-liquid phase is in close contact for mass transfer. The packed tower belongs to continuous contact gas-liquid mass transfer equipment, and the two-phase composition changes continuously along the tower height. Under normal operating conditions, the gas phase is the continuous phase and the liquid phase is the dispersed phase. When the liquid flows downwards along the packing layer, it tends to gradually concentrate towards the tower wall, causing the liquid flow near the tower wall to gradually increase. This phenomenon is called wall flow. The wall flow effect causes uneven distribution of gas-liquid phases in the packing layer, resulting in a decrease in mass transfer efficiency. Therefore, when the filling layer is high, it is necessary to divide it into sections and set up a redistribution device in the middle. The liquid redistribution device consists of two parts: a liquid collector and a liquid redistributor. The liquid flowing down from the upper layer of packing is collected by the liquid collector and sent to the liquid redistributor. After redistribution, it is sprayed onto the lower layer of packing. The packed tower has the advantages of high production capacity, high separation efficiency, low pressure drop, small liquid holding capacity, and high operational flexibility. The packed tower also has some shortcomings, such as high cost of packing materials; When the liquid load is low, it cannot effectively wet the surface of the packing, resulting in a decrease in mass transfer efficiency; Cannot be directly used for materials with suspended solids or prone to aggregation; It is not suitable for complex distillation processes such as feeding and discharging on the opposite side. There are many types of tower equipment, and tower equipment is one of the most important equipment in chemical, petrochemical, and refining production. It can enable close contact between gas-liquid or liquid-liquid phases, achieving the purpose of mass and heat transfer between phases. Common unit operations that can be performed in tower equipment include distillation, absorption, desorption, and extraction.