Please tell me about the advantages and disadvantages of composite tower and packed tower.
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Packed towers are widely used in small and medium-scale distillations, especially in separation applications with higher theoretical levels, and their advantages are undisputed. However, packed towers also have inherent shortcomings, such as wall flow and bias flow problems. In addition, the investment in packed towers, especially wire mesh corrugated packed towers, is particularly large. With the expansion of production scale, the diameter of the packed tower is enlarged to 5m or even higher. Are there any engineering problems? I checked some information and found that the application range of composite towers is gradually expanding. I would like to ask, what are the advantages and disadvantages of composite towers compared to wire mesh corrugated packing towers? What kind of structure is suitable for a distillation tower with a theoretical level of more than 600 and a diameter of more than 5m?
I have never encountered a tower with so many theoretical levels and such a large diameter. It is worth discussing. The fear of clogging of fillers, especially wire mesh corrugations, is also a big disadvantage.
The enlargement of chemical equipment is inevitable, and there are also application examples where the theoretical board needs to reach 600. For example, the separation of dimethyldichlorosilane has a boiling point difference of only 2.8°C, but the purity needs to reach 99.95%, and domestic construction has begun to reach a scale of 200,000 tons/year. Maybe within 3 years, there will be demand for theoretical boards with a diameter of 5m and more than 600.
The two most widely used wire mesh fillers are BX and CY models. Among them, the amplification effect of BX is not obvious. As far as I know, its application tower diameter has reached more than 6mm. ； However, the amplification effect of CY is very obvious, so be especially careful when applying it to a large tower diameter. .
Wire mesh corrugated packing is indeed widely used, but large investment is inevitable. Does anyone know about composite towers? In comparison, what are the advantages and disadvantages of composite towers?
"Modern Column Technology" has a relevant introduction to composite trays. I think the advantages are not very obvious, and at the same time, we have to endure the disadvantages of complicated structure and installation. The following is an introduction to some information "Zhejiang * * A tower internals structure developed by the college, which combines trays and an additional layer of structured packing under each tray to form a mass transfer unit. The tray uses a cross-flow sieve plate without a downcomer. The gas and liquid are bubbled and contacted on the tray. The gas rises through the sieve holes and the liquid also falls through the sieve holes and enters the next tray. However, before the liquid leaks from one flow plate into the next, it must pass through a regular packing layer of about 100 to 200 mm. Similarly, the gas first passes through this packing layer before entering the tray, so the gas and liquid can achieve secondary mass transfer, which is similar to increasing the actual number of trays, thus improving the separation efficiency of the trays. This tray has been used in the 10,000 t/year two-tower process of a factory in Zhejiang. The tower diameters are Ф800 and Ф1000 respectively. After modifying the F1 float valve tray, the tower height can be reduced by about 7m. The disadvantage of this tower internal structure is that: The operation of the flow tray itself is not easy to stabilize ； The liquid flowing down the screen hole is not uniform, which makes it difficult to achieve uniform gas-liquid contact in the regular packing layer under the tray, and the plate efficiency is difficult to be as expected. ； It is also obvious that the structure is complex, and the difficulty of realizing a large-diameter tower is conceivable. It should be pointed out that there are other designs for adding a packing layer between the plates in a plate column to improve the separation effect. for example: There is a packing layer slightly above the two-layer plates to reduce the impact of mist entrainment on the upper tray. At this time, the tray has a downcomer type. ； Placing a packing layer directly on the tray can improve the gas-liquid contact condition on the tray and suppress the height of the bubble layer. ” The reason why there is little research is because the advantages are not very big, mainly because the current packing technology and plate tower technology are too mature. My personal opinion, please ask experts to correct me if I am wrong.
Thank you for your statement upstairs. This kind of structure of the composite tower is what I am paying more attention to now. According to the other party's information, compared with the wire mesh corrugated filler, the investment can be reduced by about 30%. However, seeing the shortcomings of this tower, I think it is better to be cautious. For packed towers, the cost of the tower itself is not high, but the packing is relatively expensive, and the larger the diameter of the tower and the greater the height of the equal plates, the greater the investment. This is also an aspect that restricts the application of packed towers.