The choice of packing type: the choice of packing type to consider the requirements of evacuation process, we usually consider the following aspects:

1. The mass transfer efficiency is high, as usual, the mass transfer efficiency of structured packing is higher than bulk packing
2. For high flux, fillers with high flooding point gas velocity or gas phase kinetic energy factor should be selected on the premise of guaranteeing high mass transfer efficiency
3. The pressure drop of the packing layer should be low
4. Strong anti-fouling and plugging performance of the filler, easy disassembly and maintenance

The choice of packing size

Packing size refers to the nominal size or specific size of the packing.

1. Selection of bulk packing size: industrial towers commonly used bulk packing DN16, DN25, DN38, DN50, DN76 and other specifications.Similar packing, the smaller the size, the higher the efficiency of evacuation, but the growth of resistance, flux is too large, packing cost also increased a lot.The large size of the packing used in the small diameter tower, and will produce liquid dispersion poor and tension wall flow, so that the tower's evacuation efficiency is low.Therefore, the ratio of tower diameter to packing size should be defined. As usual, the ratio of tower diameter to packing nominal diameter D/ D should be greater than 8.
2. The choice of structured packing size: structured packing is commonly used in industry type and specification of performance is much more, domestic use structured packing mainly has 125, 150, 250, 350, 500, 700, several kinds of specifications, such as the same example of structured packing, than the product appearance, the greater the mass transfer efficiency is higher, but the resistance increases, the flux is too large, the packing cost also increase obviously.The selection should be based on the comprehensive consideration of evacuation requirements, flux requirements, site conditions, material properties, configuration investment, operating costs and other aspects, so that the chosen filler can meet the technical requirements and economic rationality.

The choice of packing material

Packing material is divided into ceramic, metal and plastic three categories.

1. Ceramic packing: ceramic packing has a good corrosion resistance and heat resistance, ceramic packing has a good appearance wettability, brittle, fragile is its biggest disadvantage.It is widely used in gas extraction, gas washing and liquid extraction.
2. Metal packing: metal fillers can be made of a variety of materials.Carbon steel packing has low cost and good wettability in appearance, and it should be considered and used first to deal with non-decaying or low-decaying materials.The stainless steel filler has strong corrosion resistance and can resist the corrosion of common materials except CL- as usual, but it has high cost and poor wettability of appearance. In some special places (such as the vacuum distillation process under extremely low spray density), appearance should be treated and punished in order to obtain good use results.Fillers made of titanium, special alloy steel and other materials cost a lot and are usually only used in some highly corrosive materials.Metal filler can be made into thin wall layout, it has a large flux, small gas resistance, has a high anti-impact performance, can be used in high temperature, high pressure, high impact strength, the application category is the most common.
3. Plastic packing: the material of plastic packing includes polypropylene PP, polyethylene PE and polyvinyl chloride PVC, etc. Generally, polypropylene is adopted in China.Plastic fillers have good corrosion resistance, and can resist general inorganic acids, alkali and organic solvents.Its good temperature tolerance, can be long-term use under 100 ℃.Plastic packing is light in weight, cheap in price, with good toughness, resistant to attack, not easily broken, can be made into thin wall layout, its flux, pressure reduction, more used for absorption, desorption, extraction, dust removal and other devices.