Cascade Mini Ring

A ceramic cascade mini ring, also known as a ceramic stepped ring, is a small ceramic packing element used loose in the beds of chemical towers. Its shape is the key to it. Take a Pall ring, the common windowed cylinder; shorten it so it is only about a third to a half as tall as it is wide, and roll a small flared collar around one open end. That is a cascade ring. The change matters because a short, flared ring cannot nest inside its neighbours the way a tall ring can, so a bed of them sits open and even, with the pieces resting on their collars; liquid spreads and drains well, gas passes freely, and the packing works efficiently at a low pressure drop. This one is made of fired ceramic, which is chosen when the tower is hot or corrosive: the ceramic resists strong acids and alkalis, holds its strength under load, and takes continuous high temperature that would soften or corrode a metal ring. So it combines the efficient cascade shape with the ruggedness of ceramic, for demanding towers.

It is the third step in a line of improving ring shapes. The oldest, the Raschig ring, is a plain hollow cylinder as tall as it is wide; it works, but the tubes tend to line up and nest, leaving parts of the bed blocked and the distribution uneven. The Pall ring improved on it by punching windows in the wall with tongues bent inward, which opened the inside of each ring to the flow and lifted both capacity and efficiency. The cascade, or stepped, ring goes a step further by changing the proportions: making the ring short, about a third to a half of its diameter in height, and adding a flared collar. Being short and collared, the rings cannot stack or nest, so they pack into a more open, more uniform bed with fewer dead spots; the result is a higher capacity, a lower pressure drop, and slightly better efficiency than a Pall ring of the same size. In short: Raschig to Pall added the windows, Pall to cascade fixed the shape. Tell us your tower and duty and we will size it.

Both cascade rings have the same efficient shape; the material decides which to use. A ceramic cascade ring is the choice when the service is hot or chemically aggressive. Fired ceramic shrugs off strong acids and alkalis, takes continuous temperatures to at least 1000 degrees, and resists abrasion, so it suits acid plants, high-temperature process gas and other punishing chemistry; the trade is that ceramic is heavier and brittle, and its thicker walls leave a lower void fraction, here 73 to 78 percent. A metal cascade ring, pressed from thin stainless steel, is far stronger and much more open, with a void well into the nineties, so it carries a higher load and resists mechanical shock, but it costs more and can corrode in the wrong stream. As a rule: ceramic for hot, corrosive, cost-sensitive towers; metal for high capacity, strength and mechanical duty. Tell us the temperature and the chemistry and we will point to the right one.

A ceramic cascade ring is used in the packed towers of industries where the process is hot, corrosive, or both. It fills columns in the chemical industry and in fine chemicals, in metallurgy and in iron and steel works, in acid manufacture and in oxygen production, and in pharmaceutical processing, anywhere gas and liquid must be contacted for absorption, scrubbing, cooling or reaction and the conditions rule out a plastic or metal packing. In every case its job is the same: to give a large, well-distributed contact surface at a low pressure drop, in a ceramic body that the heat and the chemicals cannot harm. Its high-temperature rating, to at least 1000 degrees, and its acid and alkali resistance are exactly what these heavy industries need. Send us the tower, the duty and the operating temperature and we will confirm the size and quantity.