The geometric characteristic data of fillers mainly include specific surface area, porosity, filler factor, etc., which are the basic parameters for evaluating filler performance.
(1) Specific surface area The surface area of the filler per unit volume of the filler is called the specific surface area, expressed as a, and its unit is m2/m3. The larger the specific surface area of the packing, the larger the gas-liquid mass transfer area provided. Therefore, the specific surface area is an important index to evaluate the performance of the filler.
(2) Porosity The void volume per unit volume of the filler is called porosity, expressed in e, and its unit is m3/m3, or expressed in %. The greater the porosity of the filler, the greater the gas passing capacity and the lower the pressure. Therefore, porosity is another important indicator for evaluating the performance of fillers.
(3) Filler factor The ratio of the specific surface area of the filler to the cubic porosity, namely a/e 3, is called the filler factor, expressed as f, and its unit is 1/m. It represents the hydrodynamic properties of the filler, the smaller the f value, the smaller the flow resistance.
The performance of the filler mainly depends on:
Larger specific surface area (m2/m3 packing layer)
The liquid has good uniform distribution on the surface of the filler
Air flow can be evenly distributed in the packing layer
The filler 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 surface wettability, the higher the mass transfer efficiency; the greater the porosity of the filler, the more open the structure, the greater the flux The greater the pressure drop, the lower. Using fuzzy mathematics method to evaluate the performance of nine commonly used fillers, the comprehensive performance of the wire mesh corrugated packing is the best, and the Raschig ring is the worst.
The choice of packing includes determining the type, specification and material of the packing. The selected filler must not only meet the requirements of the production process, but also minimize the equipment investment and operating costs.