Selection of packing for vacuum distillation columns

The specific reason isn’t clear either, but in all of our units it’s the corrugated plate regular packing that’s to blame

With regular packing, there is low pressure drop and high processing capacity. Feel free to learn more about our streamlined ceramic corrugated regular packing.

Our unit uses Pall ring packing, and the results are very good.

Use corrugated plates for clean materials, and Baffle rings for dirty materials as they are easier to remove and clean.

If the oil is not dirty, corrugated plates are a good choice; for very dirty oil, Pall rings should be used. When they become dirty, they need to be cleaned or burned to remove the dirt before being put back into use...

Selection of packing for the vacuum distillation tower: includes determining the type, specifications, and material of the packing. The selected filler must meet the requirements of the production process while minimizing equipment investment and operating costs. 1. Selection of packing type: The choice of packing type depends on the requirements of the separation process. Generally, the following factors are considered: (1) High mass transfer efficiency – Typically, structured packings have a higher mass transfer efficiency than random packings. (2) High flux – While ensuring high mass transfer efficiency, packings with a higher superficial gas velocity or gas kinetic energy factor should be selected. (3) Low pressure drop across the packing layer. (4) Packings that are resistant to fouling and clogging, and are easy to install, remove, and maintain. 2. Selection of packing specifications: Packing specifications refer to the nominal size or specific surface area of the packing. (1) Selection of bulk packing specifications: The commonly used bulk packings in industrial towers include specifications such as DN16, DN25, DN38, DN50, and DN76. For similar packing materials, the smaller the size, the higher the separation efficiency; however, this leads to increased resistance, reduced flux, and a significantly higher cost for the packing. The use of large-sized packing in small-diameter columns leads to poor liquid distribution and severe wall flow, thereby reducing the separation efficiency of the column. Therefore, a specification must be set for the ratio of the tower diameter to the packing size; generally, the ratio D/d of the tower diameter to the nominal diameter of the packing should be greater than 8. (2) Selection of the specifications for structured packing: There are many ways to denote the models and specifications of structured packing used in industry. In China, the specific surface area is commonly used as a parameter; the main specifications include 125, 150, 250, 350, 500, 700, etc. For structured packing of the same type, the higher the specific surface area, the greater the mass transfer efficiency, but the resistance increases, the flow rate decreases, and the cost of the packing also rises significantly. When selecting, a comprehensive consideration should be given to factors such as separation requirements, flux requirements, site conditions, material properties, as well as equipment investment and operating costs, so that the selected packing can meet the technical requirements while also being economically reasonable. It should be noted that a packing tower can use packing of the same type and specification, or it can also use packing of the same type but different specifications ； The same type of filler can be used, or a different type of filler can also be chosen ； Some tower sections can use structured packing, while others can use random packing. Flexibility should be exercised during design, and the specifications of the filler should be selected in accordance with the principle of integrating technology and economics. 3. Selection of filler material: Filler materials are divided into three main categories: ceramics, metals, and plastics. (1) Ceramic fillers: Ceramic fillers possess excellent corrosion and heat resistance. They are inexpensive, and have good surface wetting properties; however, their greatest drawback is that they are brittle and easy to break. It is widely used in processes such as gas absorption, gas washing, and liquid extraction. (2) Metal fillers: Metal fillers can be made from various materials, and corrosion is the main factor to consider when selecting them. Carbon steel packing is inexpensive and has good surface wetting properties; it should be given priority for use in systems that are non-corrosive or have low corrosivity ； Stainless steel packing has strong corrosion resistance and can generally withstand the corrosion of common substances other than Cl–. However, it is more expensive, and its surface wettability is poor; in certain special applications (such as vacuum distillation processes with extremely low spray densities), its surface must be treated to achieve good performance ； Packers made of materials such as titanium and special alloy steels are very expensive, and are generally used only in environments with extremely high corrosivity. Generally, metal fillers can be made into thin-walled structures; they have a high flow rate, low gas resistance, and excellent impact resistance, allowing them to be used under conditions of high temperature, high pressure, and high impact stress, which makes them the most widely used type. (3) Plastic fillers: The materials used for plastic fillers mainly include polypropylene (PP), polyethylene (PE), and polyvinyl chloride (PVC), among others; in China, polypropylene is commonly used. Plastic fillers have good corrosion resistance and can withstand the corrosion of common inorganic acids, bases, and organic solvents. It has good heat resistance and can be used for a long time at temperatures below 100°C. Plastic fillers are lightweight and inexpensive, possess good toughness, are impact-resistant and not easy to break, allowing them to be used in thin-walled structures. It features high throughput and low pressure, and is commonly used in devices for absorption, desorption, extraction, dust removal, etc. The disadvantage of plastic fillers is their poor surface wettability, but this can be improved through appropriate surface treatment.

Consider the operating pressure; if the vacuum level is high, it’s best not to use bulk packing, as the pressure drop will be high. Regular packing results in a relatively lower pressure drop.