... Cascade Ring (PP, PE, PVC, CPVC,etc.) 1.high free volume 2.low pressure drop 3.low mass-transfer unit ... and polyvinylidene fluoride (PVDF).It has features such as high free volume, low pressure drop, low mass-transfer unit height, ... 150. For these reasons it is widely used in the packing towers in petroleum industry, chemical industry, alkali-Chloride industry, coal gas industry and environmental ...