Introduction: Cascade Mini Ring
high-performance random packings provide significant capacity advantages and
lower pressure drop than other random packings. These high-performance random
packings have consistently demonstrated capacity improvements of up to 15% in a
variety of applications without loss of efficiency. Superior mechanical
integrity allows processors to specify deep beds without packing deformation.
Both high performance packings are available in several sizes and virtually any
metallic material. Cascade Mini Ring random packings are the most advanced
random packing designs offered today. Low Aspect Ratio (1/3 to 1/2 of H/D)- Key
to Highest Performance for Mass Transfer. Cascade Mini Ring is the successful
third-generation random packing. Since its introduction, CMR random packing has
been utilized in a wide variety of distillation, absorption and stripping
columns around the world. The superior performance of CMR random packing has
been shown in thousands of successful installations. CMR is the random packing
of choice for the majority of licensed processes. Among the many random packings
available on the market, the PALL-RING has been popular for several decades.
Characteristic of the PALL-RING (and most other cylindrical ring-shaped
packings) is the fact that the ring height is equal to the ring diameter, i.e.,
the height-to-diameter ratio is equal to 1.0. The Cascade Mini Ring random
packing has an aspect ratio of only 1: 3, i.e., its height is typically only 1/3
of its diameter. Seemingly minor, this change in geometry has a profound effect
on the process performance of the packing. Indeed, when dumped in a tower, the
"flat" CMR rings tend to orient themselves preferentially in a "near-horizontal"
position, i.e., with their cylindrical axis predominantly in the direction of
the vapor and liquid flow. This is exactly the opposite of the tendency of
PALL-RING (and other high-aspect-ratio rings) to preferentially orient
themselves on their "side" (cylindrical axis more horizontal than vertical).
Performance of Cascade Mini
Ring:
This preferential
orientation of the Cascade Mini Ring (CMR ring) brings about substantial
improvements in process performance:
1.
Lower pressure drop: Having its largest opening predominantly in the
direction of the vapor flow allows for easy vapor passage, resulting in lower
pressure drop.
2. Higher capacity:
The lower pressure drop moves the operating point farther away from the
critical pressure drop at which flooding occurs (typically 1-2 in. wc/ft or
10-20 mbar/m). This means additional vapor/liquid handling capability.
3. Better fouling resistance: Any solids
entering the packed bed are more easily flushed through the packing matrix by
the liquid.
4. Higher efficiency:
This preferential orientation of the Cascade Mini Ring (CMR
packing) , resulting in most of its surface being positioned vertically in the
tower rather than horizontally, is also advantageous for mass transfer. It is
important that as much of the available surface area as possible be effectively
wetted. The underside of any horizontal surface in the packed bed is shielded
from the liquid trickling down and is therefore not effectively wetted. By
definition, these dry surfaces take no part in the mass transfer process and are
lost.
Substituting PALL-RING with Cascade Mini Ring
(CMR ring) will, therefore, result in clear capacity and pressure drop and/or
efficiency gains, depending on which option the designer chooses. The high
strength-to-weight ratio of the CMR packing allows the use of deep beds while
minimizing the number of support plates and redistributors. CMR packing also
resists compression making removal easy during turnarounds.
