Selection of structured packing

The selection of structured packing is mainly to select the specific surface area per unit volume (such as 125, 250, 350, 500, etc.), and the corrugation inclination angle (30 degrees and 45 degrees). Structured packing is basically evolved from Sulzer’s Mellapak 250Y, you can check it out.

Great initiative, I’m also very interested in this! Everyone can come up and express their opinions and exchange ideas!

Selected based on specific surface area~~~~

　Structured packing is packing that is arranged in a certain geometric configuration and stacked neatly. There are many types of structured packing, which can be divided into grid packing, corrugated packing, pulse packing, etc. according to their geometric structure. 　　(1) Grid filler Grid filler is composed of strip-shaped units combined according to certain rules and has a variety of structural forms. The earliest grating filler used in industry is wooden grating filler. Currently, Grich grid packing, mesh grid packing, honeycomb grid packing, etc. are commonly used, among which Grich grid packing is the most representative. 　　The specific surface area of ​​the grid packing is low, and it is mainly used in situations requiring small pressure drop, large load and anti-blocking. 　　(2) Corrugated packing Most of the structured packing currently used in industry is corrugated packing, which is a disc-shaped packing composed of many corrugated thin plates. The inclination angles of the corrugations and the tower axis are 30° and 45°. During assembly, two adjacent corrugated plates are stacked in opposite directions. Each disk of packing is installed vertically in the tower, and the adjacent two disks of packing are arranged staggered at 90°. 　　Corrugated packing can be divided into two categories according to its structure: mesh corrugated packing and plate corrugated packing. Its materials include metal, plastic and ceramics. 　　Wire mesh corrugated packing is the main form of mesh corrugated packing, which is made of wire mesh. The metal mesh corrugated packing has a low pressure drop and high separation efficiency. It is especially suitable for precision distillation and vacuum distillation equipment, and provides an effective means for the distillation of difficult-to-separate and heat-sensitive substances. Although its cost is high, it is still widely used because of its excellent performance. 　　Metal sheet corrugated packing is a major form of sheet corrugated packing. The corrugated plate of this filler is punched with many small holes of about f5mm, which can roughly distribute the liquid on the plate and enhance lateral mixing. Fine grooves are rolled on the corrugated plate, which can finely distribute the liquid on the plate and enhance the surface wetting performance. Metal orifice plate corrugated packing has high strength and strong corrosion resistance, and is especially suitable for large-diameter towers and situations with large gas-liquid loads. 　　Metal rolled orifice plate corrugated packing is another representative corrugated plate packing. The main difference between it and metal orifice plate corrugated filler is that the surface of the plate is not punched holes, but punctured. The rolling method is used to roll out very dense small punctures with a diameter of 0.4~0.5mm on the plate. Its separation ability is similar to mesh corrugated packing, but its blocking resistance is stronger than mesh corrugated packing, and it is cheaper and widely used. 　　The advantages of corrugated packing are compact structure, low resistance, high mass transfer efficiency, large processing capacity, and large specific surface area (commonly used ones are 125, 150, 250, 350, 500, 700, etc.). The disadvantage of corrugated packing is that it is not suitable for handling materials with high viscosity, easy polymerization or suspended solids, and it is difficult to load, unload and clean, and the cost is high. 　　(3) Pulse filler Pulse filler is a structured filler made of hollow prismatic individuals with neckings assembled in a certain way. After the pulse packing is assembled, a porous prismatic channel with necking will be formed. Its longitudinal flow channel alternately shrinks and expands, and strong turbulence is generated when the gas and liquid phases pass through. In the constriction section, the gas velocity is the highest and the turbulence is intense, thereby enhancing mass transfer. In the expansion section, the gas velocity is reduced to a minimum and the separation of the two phases is achieved. The alternate repetition of contraction and expansion of the flow channel realizes the "pulse" mass transfer process. 　　Pulse packing is characterized by large processing capacity and small pressure drop, making it an ideal packing for vacuum distillation. Its excellent liquid distribution performance reduces the amplification effect, so it is especially suitable for situations with large tower diameters. You can choose structured packing according to the material system you are separating. As for the specific surface area, you can make an optimized choice based on equipment investment.

First consider the working conditions of the material operation and what materials and forms to choose.； Next, calculate the flux and height.

Selection of structured packing specifications. There are many ways to express the models and specifications of structured packings commonly used in industry. Domestic* The conventional specific surface area is expressed in several specifications such as 125, 150, 250, 350, 500, 700, etc. For the same type of structured packing, the larger the specific surface area, the higher the mass transfer efficiency, but the resistance increases, the flux decreases, and the packing cost also increases significantly. When selecting, comprehensive consideration should be given to separation requirements, flux requirements, site conditions, material properties, equipment investment, operating costs, etc., so that the selected filler can not only meet the technical requirements, but also be economically rational. It should be pointed out that a packed tower can use the same type and specification of packing, or the same type of packing with different specifications. ； You can use the same type of fillers or different types of fillers ； Some tower sections can use structured packing, while some tower sections can use bulk packing. The design should be flexible and the specifications of the filler should be selected based on the principle of technical and economic unity. The filler materials are divided into three categories: ceramics, metals and plastics. (1) Ceramic filler Ceramic filler has good corrosion resistance and heat resistance. Ceramic filler is cheap and has good surface wetting properties. Its biggest shortcomings are brittleness and brittleness. It is widely used in gas absorption, gas scrubbing, liquid extraction and other processes. (2) Metal fillers Metal fillers can be made of a variety of materials, and corrosion issues are mainly considered when selecting. Carbon steel fillers are low cost and have good surface wetting properties. They should be given priority for non-corrosive or low-corrosive systems. ； Stainless steel packing has strong corrosion resistance and is generally resistant to corrosion by common substances except Cl–. However, its cost is high and its surface wetting performance is poor. In some special occasions (such as the vacuum distillation process under extremely low spray density), its surface needs to be treated to achieve good results. ； Fillers made of titanium, special alloy steel and other materials are very expensive and are generally only used in certain highly corrosive systems. Generally speaking, metal fillers can be made into thin-walled structures, which have large flux, small gas resistance, and high impact resistance. They can be used under high temperature, high pressure, and high impact strength, and have the widest range of applications. (3) Plastic filler The materials of plastic filler mainly include polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), etc. Polypropylene is generally used in China. Plastic fillers have good corrosion resistance and can withstand corrosion from general inorganic acids, alkalis and organic solvents. It has good temperature resistance and can be used below 100°C for a long time. Plastic fillers are lightweight, cheap, have good toughness, are impact-resistant and not brittle, and can be made into thin-walled structures. It has large flux and low pressure, and is mostly used in absorption, desorption, extraction, dust removal and other devices. The disadvantage of plastic fillers is poor surface wetting properties, but their surface wetting properties can be improved through appropriate surface treatment.

Thank you all for your participation1# metre

This is a broad subject.

The explanation on the 5th and 7th floors is very detailed, thank you.

Some tower sections can use structured packing, while some tower sections can use bulk packing. The design should be flexible and the specifications of the filler should be selected according to the principle of technical and economic unity.