Do towers over 100 meters necessarily have to be designed in two sections?

Towers that are 50 to 60 meters tall are already quite high; when a tower is too tall, the wind load on its top becomes very large. Additionally, a large degree of inclination during tower operation has a significant impact on its efficiency. Therefore, it is recommended to divide the tower into two sections, which can improve its operational efficiency.

Of course, it’s not just a matter of intensity; otherwise, your vapor rise and reflux would pose serious problems. For the separation of ethylbenzene, a three-stage column in series is used.

I’m not familiar with tower design; I’ll have to wait and learn from experts. I can still help with matters related to packing: handshake

Of course, it’s not absolute; as long as the manufacturing process permits it and all practical requirements can be met, it’s possible ； It’s generally best to divide it into two ends or three sections, with a recirculation pump used to connect them; this also facilitates manufacturing. If the wind load is high, many reinforcing ribs and anti-vibration elements are required, which increases costs. It’s better to use segmented design – usually, structures over 70 meters in length need to be segmented. Even for processing, fabrication has to be carried out on-site, haha

If the manufacturing capabilities permit, it is also possible to avoid segmentation; the propylene tower in a recent coal-to-olefins project did not have any segmentation sections, and I will find pictures and post them.

A 100-meter tower is quite excessive; it might not even be possible to build it in two sections. Moreover, due to its great length, the pressure drop across the tower should be significant, and there will likely be a large difference in the gas and liquid flow rates at the top and bottom, so it may be necessary to use a tapered design. However, the rationality of designing such a tall tower is itself questionable.

　　The propylene distillation column C40406 for the Fujian refining and chemical integration project, designed by Sinopec Engineering Corporation and manufactured by Cohenma Special Process Equipment (Changshu) Co., Ltd., has an inner diameter of Ф6400×107300 and a weight of 1,200 tons. The propylene distillation column for CS Shell Petrochemical’s 800,000 tons per year ethylene cracking unit was imported from Japan; it has a diameter of 6.9 meters, a length of 94 meters, and a weight of 1,240 tons. The propylene distillation column for the 600,000 tons per year ethylene unit in the Sino-German joint venture project “Yangba Integration” has a height of 95 meters, a maximum diameter of 8.5 meters, and a weight of 845.8 tons. The second propylene distillation tower of Tianjin’s 1 million tons per year ethylene plant and its associated facilities is 107.85 meters tall and 7.8 meters in diameter, with a weight of 1,316 tons. The second propylene distillation tower of Zhenhai Refining & Chemical’s 1 million tons per year ethylene plant is identical to that in Tianjin Petrochemical. Last edited by Haituo on 2008-12-14 at 11:04

For pressure-driven distillation columns, pressure drop is not a major issue, and from a process perspective, there is no need for segmentation. Moreover, segmentation does not reduce the overall pressure drop; in addition, it requires an additional liquid transfer pump between stage one and stage two. Whether to use segmentation or not depends on the level of manufacturing and transportation capabilities, as well as other economic factors. In the past, due to limitations in manufacturing, transportation, and installation capabilities, segmentation was necessary, but now that these capabilities have improved, segmentation is no longer required – the remaining factor is economic considerations. Additionally, as plants become larger, the diameter of the columns increases significantly, which enhances their wind resistance and also facilitates the elimination of segmentation. Therefore, when designing new plants, it is essential to compare multiple options rather than following others blindly.

After segmentation, it is necessary to use pumps to transport the liquid in between, which increases equipment costs and energy consumption. In facilities like ethylene plants, distillation can be carried out entirely using the upstream pressure without segmentation. For large-scale projects, there cannot be just one tower, and given their large diameter, these towers can be constructed as frame-type platforms to withstand wind loads. In short, a detailed comparison of different approaches to segmentation is required; one should not follow conventions blindly.