Mastering the Chaos

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Courtesy of Sulzer Management Ltd

Random packing consists of single pieces that are poured into separation columns and form a chaotic structure. Now, Sulzer has developed a new generation of high-performance random packing that offers more uniformity of surface distribution within the packing volume. The example of a CO2 absorber shows the benefits.

Columns with random packing are well established for fractionation, absorption, and stripping operations in gas, refinery, and chemical plants. Random packing provides benefits, especially in high-liquid-load and high-pressure applications. Furthermore, ease of replacement and storage make random packing the ideal choice for systems with heavy fouling or corrosion, where packing is frequently replaced.

A widespread application of random packing is the purification of natural gas. By contacting the gas with amine-based solvents, components like carbon dioxide or hydrogen sulfide can be removed. The performance of the packing significantly influences the capacity and the costs of the separation process. Therefore, Sulzer continuously improves the performance of its random packing products.

The design of the rings has evolved over time from the early geometries introduced at the end of the 19th century. The first installations were cylindrical tubes randomly arranged in a column (A). They combined a large surface area for gas-liquid contact but also had a closed structure, which led to high flow resistance for vapor flow and resulted in high-pressure drops in operation. The first innovation to this design was to put holes in the cylindrical tubes (B). This change caused a lower pressure drop without reducing the efficiency of the design. The next breakthrough was to further open the structure of the cylindrical design (C), providing significantly more open area, again, without reducing the surface area. Therefore, the efficiency of the packing was maintained at a much lower pressure drop. Now, Sulzer has achieved a further breakthrough by designing the latest generation of random packing, called NeXRingTM (D).

Development of the NeXRing

The NeXRing provides an extremely large and uniform open area regardless of ring orientation, allowing high surface exposure to liquid and vapor while minimizing dry zones.

Looking at the various stages, or “generations,” of random packing evolution, it became clear that structures with a more uniform surface distribution within the packing volume offer better performance. Sulzer’s NeXRing random packing, designed with this in mind, provides an industry-leading combination of capacity, efficiency, and strength.

NeXRing packings are designed with reinforced ribs that are spaced evenly throughout the packing volume. This uniform mechanical structure ensures uniform fluid flow through the bed. There are other benefits to this design as well. The end flanges combined with strengthened ribs make NeXRing inherently strong. The open structure lowers the pressure drop by 50% compared with conventional packings. 

Concrete benefits

The NeXRing has been tested both in house and at an independent US test center. All results have shown improved hydraulic performance over established random packing types with the same efficiency.

The exemplary case of a CO2 absorber shows how the performance increase translates into cost savings. One of the biggest benefits is the reduced pressure drop. The NeXRing minimizes the hydraulic impact of foam and, therefore, causes a much lower pressure drop than older random packing types. In existing columns, NeXRing can directly replace previous generations of random packing and create significant capacity increases. The capacity of the CO2 absorber described increases by 10% after replacing the I-Ring random packing with Sulzer NeXRing random packing. In newly constructed plants, capital costs can be saved because column diameters can be reduced. For the process described, the column diameter could have been reduced by 6%.

Example of a CO2 absorber column (internal diameter 4900 mm, packing height 2x7.3 m): Compared with the I-RingTM #50, the NeXRing #2 shows a reduced pressure drop. The additional performance translates directly to significant capital savings for a new build and allows substantial capacity increases for existing plants.

Positive feedback

The NeXRing has been patented. Three sizes are currently available, and further sizes are in planning. Sulzer presented the NeXRing at the Achema exhibition in Germany. The feedback was very positive—three larger orders have been received already. NeXRing is the first development of Sulzer’s high-performance NeXt packing family. Sulzer will continue to expand its packing portfolio and plans to introduce further products of the next generation.

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