Which is more costly, the internals of a distillation tower or the tower shell?
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For a distillation tower, it can be either packing or trays; the cost of these internal components versus the production cost of the tower shell – which one is higher? To rule out the use of special materials for fillers, or very expensive fillers such as DX, it is specified that ordinary stainless steels such as 304 or 316 should be used. The same applies to the tower shell, which is designed to operate at 7 bar; the material used is carbon steel or ordinary stainless steel.
If a plate tower is used and the tower diameter is relatively large, i.e., greater than 2000 mm, the cost of the internal components is relatively low
The internals include not only trays and packing; generally speaking, the cost of internals for large-diameter towers (material and processing costs) is higher than that of the tower shell itself.
The tower shell is easier to process, resulting in lower labor costs, while the internal components are more difficult to manufacture due to strict dimensional requirements, which leads to higher labor costs
In the case of ordinary plate towers or packed towers, it is the shell that is expensive; however, if high standards are required for the internal components such as distributors and liquid collection devices, then the shell is cheaper than these internal components and packing.
The tower structure is simply a layer of outer shell, which isn’t very expensive; but if the operating pressure is high, then the costs associated with wall thickness, sealing, welding, and so on increase. Typically, tray plates are much cheaper than packing; taking a tower diameter of two meters as an example, one can calculate the cost based on its weight and the unit price of the material, and the cost of tray plates is not even two to three thousand yuan. If a filler is still used for a tower with a diameter of two meters, 3.14 cubic meters of filler will be required for a height of one meter. The price of filler made from ordinary materials is around 10,000 yuan per cubic meter, and the mass transfer efficiency achieved by one meter of filler is at most equivalent to that of 4 tower plates. 4 trays cost around 10,000 yuan, while packing with a height of 1 meter costs over 30,000 yuan. In addition, collectors and distributors need to be added to the packed tower every 5 or 6 meters, which represents another expense. Therefore, unless the tower diameter is very small and plate towers cannot be used, or in the case of atmospheric and vacuum distillation towers where a very low pressure drop is required, it is best not to use packing.
Reply to 7# zjb9999: Then please ask this **person to provide an example calculation~
Learn a bit about it; I’m not familiar with these aspects
The cost of the tower shell is significantly lower than that of the internals and packing. When comparing various aspects such as materials, quality, construction, manufacturing process, and functionality, the cost of the internal components and fillers is higher than that of the tower body.
Reply to 8# springflower: Buddy, if you need the diameter, thickness, material, number of tray layers, skirt, manhole, pipe flanges, as well as the distributor, no one will be able to give an accurate estimate. Stainless steel flanges aren’t cheap either.