Liquid Distributors
The single most important factor determining the performance of a packed column is the liquid distribution i.e.
A packing is only as good as the liquid distributor.
At DtEC we design all liquid distributors with meticulous attention to detail, taking into account the relevant factors:
- Number of distribution points (point density)
- Hole or notch size
- Fouling tendency
- Turndown (operating range) required
- Operating (design) liquid head
- Minimum (turndown) liquid head
- Levelness sensitivity
With over 50 types of liquid distributors to choose from, DtEC clients are assured that the most appropriate type will be selected for their specific service and duty.
Plate - Orifice Type Distributors
For general applications plate - orifice type distributors c/w risers are used. For small columns (< 800mm Ø), a pan construction can used where the distributor is fixed to lugs welded to the column. Alternatively a plate construction is used where the distributor is clamped to a full support ring. The distributors are made in one or two pieces for installation through column body flanges.
For larger columns (> 8000mm Ø) the distributor is made in sections for installation through column man-holes. The distributor is clamped to a full support ring welded to the column shell. Consequently the distributor levelness is dependent upon the levelness of the support ring.
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Model nos. 200 & 210 have holes in the deck and are used for non fouling services. For fouling services Model nos. 201 & 211 are used which have drip tubes welded to the deck plates. The normal operating range is 2 to 1. However, the latter type can be designed for an operating range of 5 to 1 or greater by using double or triple level holes in the sides of the drip tubes.
Risers are normally circular for small diameter columns and rectangular for large diameter columns. The risers can be equipped with hats (covers) at the top to make the distributor into a re-distributor. Risers can also have anti-migration bars or mesh welded at the bottom thus eliminating the need for separate hold down grids (bed limiters).
Trough-Type Distributors
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Trough type distributors are normally used in column diameters greater than 1200mm.
Model nos. 220 & 230 have holes in the deck and are used for non fouling services. For fouling services the holes are put in the sides of the troughs. Normal operating range is 2 to 1.
Using double or triple holes in the sides of the trough the distributor can be designed for operating ranges of 5 to 1 or more. For the high turndown designs an alternative is to use drip tubes welded to the deck (Model nos. 222 & 232) with the distribution holes in the sides of the tubes.
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For services with very low liquid loads (0.1 m3/m2h or less) drip tubes c/w spider fingers are used. The spider fingers operating by capillary action spread the liquid onto the packed bed thus increasing the number of distribution points.
For structured packing beds narrow troughs are used to significantly increase the open area and number of distribution points.
The space between the secondary troughs can be covered with anti-migration bars or mesh, thus eliminating the need for separate hold down grids.
With all trough type distributors it is possible to use levelling screws to level the distributor.
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Pipe Ladder Distributors
This type of distributor is usually designed for a head loss of 1.5m. The header pipe and laterals run full of liquid and hence the distributor is insensitive to levelness.
Pipe ladder distributors are particularly suited for systems with high liquid to vapour ratios.