PP Pall Ring

PP Pall Ring

PP Pall ring is a random tower packing moulded from polypropylene. It is a short cylinder with two rows of windows cut into the wall and the freed tongues bent inward, which opens the ring up so liquid spreads through it instead of only running down the outside. Tipped at random into a packed column, the rings build a loose, high-void bed that brings gas and liquid into close contact while letting them pass with little resistance. The plastic body shrugs off acids, alkalis and salts that eat metal, and it is light and cheap to load. We make it in the standard 25 to 76 mm sizes.

Polypropylene, for corrosive acid, alkali and salt service to about 100°C.
Windowed wall with inward tongues — better liquid spread and film renewal than a plain Raschig ring.
High void fraction, around 90%, for large throughput and low pressure drop.
Standard sizes 25, 38, 50 and 76 mm, dumped at random into the column.
Light, low-cost and easy to load, clean and replace.

Technial Parameters

Size (mm)	Specific surface area (m²/m³)	Void fraction	Pieces per m³ (approx.)
25	≈225	≈90%	≈52,000
38	≈140	≈90%	≈13,600
50	≈105	≈90%	≈6,500
76	≈90	≈92%	≈1,930

Property	Value
Product Type	Plastic random packing (Pall ring)
Material	Polypropylene (PP)
Standard Sizes	25, 38, 50, 76 mm (also 16 mm, 100 mm)
Structure	Cylinder with two rows of windows and inward-bent tongues
Void Fraction	About 90%
Colour	White / off-white (natural PP)
Max Service Temperature	About 100 °C (PP)
Chemical Resistance	Acids, alkalis, salts and many solvents
Main Function	High mass transfer, low pressure drop, large throughput
Applications	Absorption, stripping, scrubbing, cooling towers, biofilters
Trademark	RONGJIAN
Origin	Jiangxi, China
HS Code	3926909090
Transport Package	Woven PP bags / bulk cartons

FAQs

What is a PP Pall ring used for?

PP Pall ring is the packing you dump into an absorption, stripping or scrubbing column so gas and liquid can meet. It is common in acid and chlorine scrubbers, flue gas desulphurisation, solvent recovery, degassing and the air stripping of water, cooling towers, and biological trickling filters where the open bed holds a biofilm. Being polypropylene, it fits duties where the stream is corrosive and metal packing would rust or a ceramic bed would be heavy and brittle. Wherever a packed tower runs a wet, corrosive, moderate-temperature service, PP Pall ring is a standard, low-cost fill.

How is a Pall ring different from a Raschig ring?

A Raschig ring is just a plain hollow cylinder, so liquid mostly runs down its outside and the inner wall does little work. A Pall ring takes that cylinder and cuts two rows of windows in the wall, folding the little tongues inward. Those openings let liquid pass into the ring and wet the inner surface, and they break the flow so it keeps renewing. The result, at the same pressure drop, is roughly half again as much gas-and-liquid capacity as a Raschig ring, and at the same load about half the pressure drop. For nearly every new column the Pall ring is the better pick, and the older Raschig ring now survives mainly where its thicker wall is wanted.

How do I choose the ring size and plastic material?

Size follows the column and material follows the chemistry. As a rule the ring should be no more than about one eighth of the tower diameter, so a narrow column takes 25 mm rings and a wide one takes 50 or 76 mm. Smaller rings give more surface area and sharper separation but more pressure drop; larger rings give more throughput and less drop. For the plastic, PP suits most acid, alkali and salt duty to about 100 degrees, PVC is cheaper but only for cooler streams, and PVDF is the choice for hot or strongly oxidising service. Tell us the tower diameter, the medium and the temperature and we will fix the size and grade.

What temperatures and chemicals can PP Pall rings handle?

Polypropylene Pall rings run continuously to about 100 degrees, and they turn brittle if the stream ever drops near freezing, so very cold duty needs a different plastic. On chemistry, PP stands up well to most dilute and concentrated inorganic acids such as hydrochloric, sulphuric, phosphoric and nitric at moderate strength, and to alkalis like caustic soda and potash. It is weaker against strong oxidisers and some hot organic solvents, where PVDF or PTFE is safer. Send us the exact medium, its concentration and the working temperature and we will confirm that PP is right or point to the grade that is.

The Pall ring began as a fix for the Raschig ring, the oldest packing of all. A Raschig ring is a plain hollow cylinder; tipped in at random it works, but liquid clings to the outside and the solid wall blocks much of the cross-flow. The Pall ring keeps the same cylinder but stamps two rows of windows into the wall and folds the freed tongues inward toward the axis. Those tongues sit in the gas and liquid path, break the flow into fresh films and droplets, and open the inside of the ring for work. For the same wall material the ring then carries far more traffic at the same resistance.

	Raschig ring	Pall ring
Wall	Solid, no openings	Two rows of windows, inward tongues
Capacity at equal pressure drop	Baseline	About 50% higher
Pressure drop at equal load	Baseline	About half
Liquid distribution	Poor, runs on the outside	Even, wets inside and out

In a plastic Pall ring the tongues and wall are moulded in one piece from polypropylene, so the ring is light, cheap and free of the rust and scaling that trouble metal. The rings are simply tipped into the column and settle into a random bed with a void fraction near 90%, which is what gives the low pressure drop and the large throughput. Size is matched to the column: keep the ring at or below about an eighth of the tower diameter, using 25 mm rings in narrow columns for surface area, and 50 or 76 mm rings in wide columns where throughput and low resistance matter more.

Typical duties are acid and chlorine scrubbing, flue gas desulphurisation, solvent recovery, degassing and deaeration, VOC air stripping, cooling towers, and trickling filters where the open bed carries a biofilm. Polypropylene covers these to about 100 degrees; for hotter or strongly oxidising streams the same ring is moulded in PVDF, and for cooler, milder duty in PVC. Where the process is clean and very hot, metal or ceramic packing takes over, but for wet, corrosive, moderate-temperature service the PP Pall ring is the practical, low-cost standard.