Introduction to the structural principles of packed towers

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A packed tower is a type of column equipment. The tower is filled with packing to an appropriate height in order to increase the contact surface between the two fluids. For example, when used in gas absorption, the liquid enters from the upper part of the tower through a distributor and flows down along the surface of the packing. The gas flows upward from the lower part of the tower through the pores in the packing, where it comes into close contact with the liquid and interacts with it. It has a simple structure, making maintenance easier. It is widely used in operations such as gas absorption, distillation, and extraction. To enhance production and increase the gas flow velocity, it is called an emulsified packing tower or emulsification tower when operated in an emulsified state. 1. Structural principle: A packing tower is a mass transfer device that uses the packing inside the tower as the component for contact between the gas and liquid phases. The tower body of a packed tower is an upright cylinder, with a packing support plate at its bottom; the packing is placed on this support plate either in a random manner or in an organized pattern. A packing plate is installed above the packing to prevent it from being blown by upward airflow. The liquid is sprayed from the top of the tower through a liquid distributor onto the packing, and flows down along the surface of the packing. Gas is fed in from the bottom of the tower; after being distributed by a gas distribution device (which is generally not used in towers with small diameters), it flows counter-currently to the liquid through the gaps in the packing layer. On the surface of the packing, the gas and liquid phases come into close contact for mass transfer to occur. A packed tower is a type of continuous-contact gas-liquid mass transfer device, in which the composition of the two phases changes continuously along the height of the tower. Under normal operating conditions, the gas phase acts as the continuous phase, while the liquid phase is the dispersed phase. As the liquid flows downward through the packing layer, it tends to concentrate toward the tower wall, resulting in an increasing flow rate of liquid near the wall; this phenomenon is known as wall flow. The wall flow effect causes uneven distribution of the gas-liquid phases in the packing layer, thereby reducing the mass transfer efficiency. Therefore, when the packing layer is high, it needs to be segmented, with a redistribution device installed in between. The liquid redistribution device consists of a liquid collector and a liquid redistributor. The liquid that flows down from the upper packing is collected by the liquid collector and then sent to the liquid redistributor, where it is redistributed before being sprayed onto the lower packing. Packed towers have advantages such as high production capacity, high separation efficiency, low pressure drop, low liquid holdup, and great operational flexibility. Packed towers also have some disadvantages, such as the high cost of the packing ； When the liquid load is low, it cannot effectively wet the surface of the filler, resulting in a reduced mass transfer efficiency ； It cannot be used directly with materials containing suspended solids or those that tend to polymerize ； Complex distillations such as counter-current feeding and discharging are not very suitable. 2. Equipment inside the tower: The internal components of the tower, together with the packing and the tower body, constitute a complete packed tower; the internal components are part of the packed tower. The function of the internal components of the tower is to facilitate better contact between gas and liquid within the tower, thereby enabling the filler tower to achieve its maximum production capacity and efficiency. Therefore, the quality of the design of these internal components has a direct impact on the operation of the entire filler tower as well as on the performance of the fillers. Furthermore, the “scaling effect” of a packed tower is greatly influenced by the internal components of the tower, in addition to the inherent factors of the packing itself. 　　The internal components of the tower mainly include the following parts: 1. Liquid distribution device; 2. Packing compression device; 3. Packing support device; 4. Liquid collection, redistribution, and feed/discharge device; 5. Gas feed and distribution device; 6. Foam removal device. 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