The geometrical characteristics of the filler mainly include specific surface area, void ratio, filler factor, etc., which are the basic parameters for evaluating the performance of the filler.
(1) Specific surface area per unit volume The surface area of the filler is referred to as specific surface area and is expressed by a, and its unit is m2/m3. The larger the specific surface area of the filler, the larger the gas-liquid mass transfer area provided. Therefore, the specific surface area is an important indicator for evaluating the performance of the filler.
(2) Void ratio The volume of voids per unit volume of the filler is referred to as void ratio, expressed as e, and its unit is m3/m3, or expressed in %. The larger the void ratio of the filler, the greater the ability of the gas to pass and the pressure to decrease. Therefore, the void ratio is another important indicator for evaluating the performance of the filler.
(3) The ratio of the specific surface area of the filler factor filler to the cubic ratio of the void ratio, i.e., a/e 3 , referred to as the filler factor, expressed as f, and its unit is 1/m. It represents the hydrodynamic performance of the packing, and the smaller the f value, the smaller the flow resistance.
The performance of the filler depends mainly on:
Has a large specific surface area (m2 / m3 filler layer)
The liquid has a good uniform distribution on the surface of the filler.
Airflow can be evenly distributed in the packing layer
The seasoning has a large void ratio (m3/m3 filler layer).
Under the same operating conditions, the larger the specific surface area of the filler, the more uniform the gas-liquid distribution, and the better the wetting performance of the surface, the higher the mass transfer efficiency; the larger the void ratio of the filler, the more open the structure, the flux The larger the pressure, the lower the pressure drop.
The performance of nine common fillers was evaluated by fuzzy mathematics. The mesh corrugated packing has the best comprehensive performance and the Raschig ring is the worst.
The choice of filler includes determining the type, size and material of the filler. The selected packing must meet the requirements of the production process, and the equipment investment and operating costs should be minimized.