Design principles for the hole arrangement of the tray-type liquid distributor in packed towers

Here is some design guidance: 1. Determine the total number of openings in the pipe array, with a range of 60–200 openings per m2. 2. Set the average exit flow velocity of the openings at 1–3 m/s. 3. Calculate the average opening diameter based on the total flow rate, the total number of openings, and the flow velocity per opening. 4. Calculate the number of openings required for each branch pipe according to the percentage of area it is responsible for supplying flow to. 5. The diameter of each branch pipe should be determined such that the cross-sectional flow velocity does not exceed 0.3 m/s, based on the total flow rate distributed by those openings. 6. Unless the tower diameter is very large, i.e., over 3 meters, or the flow velocity there exceeds 0.3 m/s, there is no need to change the diameter of the openings.

Research and design of tubular liquid distributors in packed towers: http://bbs.hcbbs.com/thread-140829-1-1.html Last edited by www557 on 2009-2-17 09:29]

Thank you all. The tower I am designing now has a very large diameter of 4.8 meters, so I need to consider uneven hole distribution; I’m not sure how to create those holes I already know the calculation method for evenly distributing holes; thank you!

Large towers rarely use tube-type distributors; trough-type ones are more common. I’m not sure if the original poster is aware of this

I agree with the opinion above – why isn’t a trough-type distributor used for such a large tower? There must be some special reasons for that. The original poster might as well provide more details so that everyone can learn from it; generally speaking, tubular distributors don’t provide very good distribution quality.

I agree with the views expressed on floors 5 and 6; pipe-type distributors are indeed not suitable for very large towers. The key issue in my question is not whether this type of distributor is appropriate or not, but rather how such holes should be created in a distributor located in a large tower, in order to reduce the liquid level gradient How are design parameters such as flow rate and velocity determined? If intermediate feeding is assumed, then regardless of the type of distributor used, it will inevitably result in a higher liquid level in the middle and lower levels on both sides, which affects the distribution of the liquid. The more large the tower is, the more pronounced this issue becomes. I’ve searched through many resources but couldn’t find any information on how to calculate these values; is there any material on this topic?

There’s nothing special about it; it’s just a multi-stage distributor. Tubular distributors are indeed not very suitable for large towers

Is the original poster overthinking things? Is what you’re saying based on your imagination or proven by experiments?

Back upstairs: There is indeed a real situation in the company, and the towers on site can prove it

There is a post on the forum regarding the design and application of liquid distributors in packed towers: http://bbs.hcbbs.com/thread-93396-1-1.html. You can download it and study it at your own pace. I hope it will be helpful to you.

No matter what type of distributor we use, issues such as the design of the pipe diameters and other related details are all handled by the filler manufacturers. Hehe~~ The ones we usually come across are trough-type liquid distributors, which offer better performance than tube-type ones; they are easy to install and result in lower pressure drops

My knowledge is too limited; I hadn’t noticed such a design before, nor had I seen anyone discuss this issue. I’ll pay attention to it in my future work.

I’ve seen that for the openings in liquid-liquid extraction distribution tubes, there is software available for performing calculations. In towers with large diameters, in order to ensure uniform discharge, several different pore sizes can be specified for the same tube. It’s not necessarily the case that the openings further away have larger diameters; those farther from the inlet may actually have smaller diameters, as this depends on the viscosity of the medium and the flow velocity inside the tube. Such calculations require software – it’s not possible to do them manually. For gas-liquid contact distribution tubes, it’s probably not necessary to have unevenly distributed pores either. When the diameter is large, it’s possible to use multiple feed pipes, that is, the main feed pipe can be divided into 2 or 4 feed branches, with each branch connected to a discharge pipe. The design of these pipes should be symmetrical, meaning that the number of branches and discharge pipes should be even. Another approach is to increase the diameter of the discharge pipes slightly, which helps improve the uniformity of liquid distribution. But making them too large results in waste.

"The Practical Special Topic Design Manual for Chemical Engineering (Volume 1), Chapter 1: Mass Transfer and Separation Processes and Their Design, Section 3: Liquid Distributors in Extraction Units – it contains detailed explanations as well as diagrams of the calculation procedures used by software; go and take a look.

It is recommended to use a trough-type distributor. The issue you mentioned of a high liquid level in the middle and lower levels on both sides during feeding can be improved by installing baffles and buffer plates. Additionally, a two-stage distribution system should be employed: the first stage for pre-distribution (where the liquid feed enters), and the second stage for overflow distribution (where the liquid flows from the first stage into the second troughs and then from there to the packing layer).

Tubular distributors have their advantages, such as taking up less space, being simple to manufacture, and having a low cost