The PTFE Rasching ring filler was invented by F. Rashching in 1914 and is a ring of equal outer diameter and height. The gas-liquid distribution of the Raschig ring packing is poor, the mass transfer efficiency is low, the resistance is large, the flux is small, and the industry has been less applied.
The PTFE pall ring packing is an improvement to the Raschig ring. Two rows of rectangular holes are formed in the side wall of the Raschig ring. One side of the cut ring wall is still connected to the wall surface, and the other side is bent inside the ring. Forming an inwardly extending tongue, the sides of the tongues converge at the center of the ring.
Due to the opening of the ring wall, the Pall ring greatly improves the utilization of the inner space of the ring and the inner surface of the ring, and the airflow resistance is small and the liquid distribution is uniform. Compared with the Raschig ring, the gas flux of the Pall ring can be increased by more than 50%, and the mass transfer efficiency is increased by about 30%. The Pall ring is a widely used filler.