Within the packed tower, the packing provides the location for the gas-liquid two-phase heat and mass transfer process. Therefore, the comprehensive performance of the packed tower is closely related to the characteristics of the packing. The quality of the packing performance is usually evaluated based on the three key factors: flow rate, separation efficiency, and pressure drop, while also considering the type, material, and dimensions of the packing. From the perspective of the geometric parameters of the packing, the performance of the packing is mainly represented by the following aspects.
1. Specific Surface Area
CY700 Stainless Steel Wire Mesh Wavy Packing, where the specific surface area refers to the surface area of the packing per unit volume of the packing bed, usually denoted as 'a', with the unit of m²/m³.
The specific surface area of the packing determines the size of the gas-liquid contact area. The larger the specific surface area, the greater the gas-liquid contact area it can provide. For the same type of packing, the smaller the size, the larger the specific surface area, but the corresponding flow resistance will also increase.
CY700 Stainless Steel Wire Mesh Wavy Structured Packing is a disk-shaped structured packing composed of vertically arranged wavy wire mesh strips. The specific surface area value has a decisive impact on the mass transfer performance. Depending on the specific surface area, the wire mesh wavy packing can be categorized into 250 m2/mi, 350 m2/m3, 500 m2/m3, and 700 m2/m3 types. Due to the fine mesh, the void ratio is high, reducing the packing pressure drop. The unique capillary action of the mesh allows for easy film-like distribution of liquid on the packing surface, with a thin liquid film and low holding capacity, thus exhibiting excellent wettability and high separation efficiency. Its drawbacks include high cost, susceptibility to blockage, and vulnerability to corrosion. Metal wire mesh wavy packing is commonly used in vacuum rectification, atmospheric rectification, and absorption operations; plastic mesh wavy packing is suitable for general absorption processes below 80°C.
The following introduces several representative classic corrugated packing and new high-efficiency corrugated packing.
(1) In 1962, Sulzer AG in Switzerland developed metal wire mesh corrugated packing. This packing is formed into corrugated sheets by molding, then assembled into disc-shaped packing with the corrugated sheets arranged in reverse. The angle between the corrugated sheets and the upright direction is typically 30° or 45°. It boasts high efficiency, low liquid hold-up, low pressure drop, and high gas flow rates. It is widely used for separating clean materials and heat-sensitive substances and was introduced into industrial applications late in the 1960s. However, the packing has high production costs, poor clog resistance, and is difficult to handle and clean, making it unsuitable for separating materials with high viscosity or solids. This limitation has restricted its use in absorption and distillation, but it has also spurred further development of structured packings.
(2) CY700 Stainless Steel Wire Mesh Wavy Packing, Mellapak Packing was originally developed by Sulzer AG of Switzerland in the 1980s and is a representative metal plate wavy packing. It is made from 0.2mm thick metal plates with grooves on the surface, featuring 4mm holes and a high porosity with an open area of 12.6%. It boasts excellent fluid dynamics, overcoming the tendency of wire mesh wavy packing to clog. It is suitable for liquid loads ranging from low to high, pressures from vacuum to distillation, and is commonly used in atmospheric pressure applications such as absorption and desorption systems. It has also replaced plate towers and loose packing in some industrial sectors, with subsequent development of plastic Mellapak packing. However, when used in high-pressure distillation, Mellapak packing experiences significant axial mixing, reducing the efficiency of the packing layer and limiting its application fields. There is still room for improvement and enhancement. The company later introduced the Mellapakplus packing, which has an improved geometric structure compared to Mellapak, significantly reducing pressure drop.
