The Pall ring packing is greatly improved on the Raschig ring. Although the outer diameter of the ring is equal to the height, two rows of windows with inner tabs are opened on the ring wall, and each window has five tongues. This structure improves the gas-liquid distribution and makes full use of the inner surface of the ring. Compared with the Raschig ring, the processing capacity can be more than 50% larger, and the pressure is reduced by half; generally, the performance of the Pall ring is made of metal, plastic or ceramic: 1. The gas velocity is high, the blade is large, and the resistance is small. 2. Large specific surface area can fully solve the gas-liquid exchange. 3. The product has the advantages of large production capacity, low resistance and large operational flexibility. The height-diameter ratio of the step ring is only half of that of the Pall ring, and the tapered flange is added at one end of the ring, thus reducing the passage of gas through the bed. The resistance and the increase of the flux, the strength of the filler is also high, due to its structural characteristics, the filler in the filler layer is more point contact. This not only increases the void ratio, reduces the pressure drop, but also constitutes the collection or dispersion point of the liquid flowing along the surface of the filler, promotes the surface renewal and liquid mixing of the liquid film, makes the gas-liquid distribution uniform, and increases the gas-liquid contact surface. It improves the mass transfer efficiency and is generally made of plastic, ceramics and metal. The material is different and the structure is different. The inner step of the metal step ring is the same as the Pall ring, and the tongue is curved in the shape of a blade. The inner rib structure of the plastic and porcelain step ring is similar to the plastic Pall ring, and also has a square shape and a well shape. Points.