Metal Tower Internals Two Stage Trough Type Liquid Distributor
The trough type liquid distributor is a gravity type liquid distributor.
The two-stage trough type liquid distributor consists of a main trough (primary trough) and a sub trough (secondary trough), and the main trough is placed above the sub
trough. The reflux liquid or the feeding liquid enter the main tank
through the feeding pipe above the main trough, and then the main
trough distributes it to the sub trough in proportion. The
structural dimensions of the main trough and the sub trough are
determined by the liquid flow rate, the tower diameter and the
requirements for the distribution quality. The structure of the
two-stage trough liquid distributor is simple, and it is easy to
enter the tower from the manhole for assembly. This kind of
structure is commonly used in the tower where people can enter for
installation, and the tower diameter is more than 800mm.
The main trough is an open structure with rectangular section, its length depends
on the tower diameter and the size of the trough, and its height
depends on the operating flexibility, usually 200-300 mm. Its
function is to distribute the liquid stably and evenly to the sub
troughs below. Therefore, the bottom or side wall of the main
trough shall be equipped with a liquid distribution device, the
main trough shall receive the liquid from the feed pipe, shall be
equipped with a flow stabilizing device, and the trough body shall
be equipped with a positioning and fixing device. The velocity of
liquid in the main trough shall not exceed 0.4m/s, otherwise it
will cause a large liquid level drop and reduce the liquid
distribution quality.
The function of the sub trough is to evenly distribute the liquid from the main trough to the
surface of the packing, so the sub trough is very important to the
liquid distribution. Its length is determined by the tower diameter
and arrangement. Its width is slightly different due to the liquid
flow rate and the required residence time, generally 30-60mm. Its
height is related to the operating flexibility, generally
250-300mm.
Performance comparison of various liquid distributors
| Item | Ladder type | Spray nozzle type | Pan with bottom hole | Trough with bottom hole | Pan with overflow | Trough with overflow |
| Power | pressure | gravity | pressure | gravity | gravity | gravity | gravity |
| Distribution quality | Middle | High | Low to middle | High | High | Low to middle | Low to middle |
capacity m3/(m2·h) | 0.25-2.5 | 0.25-10 | Wide range | Wide range | Wide range | Wide range | Wide range |
| Tower dia. /m | >0.45 | Any | Any | Any, often<1.2 | Any, often>0.6 | Any, often<1.2 | Any, often>0.6 |
| Plugging degree | High | High | Middle to high | Middle | Middle | Low | Low |
| Air resistance | Low | Low | Low | High | Low | High | Low to high |
| Levelness requirements | None | Low | None | High at low load | High at low load | High | high |
| Effect of corrosion | High | Middle | High | High | High | Low | Low |
| Influence of liquid level fluctuation | None | Small | None | Middle | Middle | Big | Big |
| Entrainment | High | Low | High | Low | Low | Low | Low |
| Weight | Low | Low | Low | High | Middle | High | middle |
Liquid distributor position in packed tower:
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