In the wide range of operations surrounding fouling removal, there is a large variation in the fouling tendencies of process fluids and equipment metallurgy.
In applications considered "dirty," the services are often prone to fouling levels that impact the column operations.
Design is crucial for reliability in extreme fouling systems
A tray in operation that appears to be clean after four years in "dirty" service.
Many column internal designs have been used to handle fouling conditions that could not be mitigated with only process changes. Depending on the fouling mechanism, some types of internals can handle conditions better than others.
Fouling due to chemical reactions, such as polymerization and coke formation, is often minimized by using packed beds due to their inherently low residence time. Packing can be used in low to even moderate fouling applications by using larger crimp packing along with fouling resistant distributor designs. However, moderate to severely fouling applications, especially those with solid deposition like corrosion products and catalyst particles, or solid precipitation like carbonates and chloride salts, typically employ trays.
With severe fouling services, large orifice, dual-flow trays are often selected. For extreme conditions, baffle trays or shed decks have been used. However, these more fouling-resistant designs come with a penalty of lower efficiency. Dual-flow trays efficiency is 15% less than a conventional crossflow tray, while baffle trays may have up to 70% loss in efficiency. From a process standpoint, there is a clear need for an extremely fouling-resistant device that performs without a substantial loss in efficiency.
Design is crucial for reliability in extreme fouling systems
Fixed extruded valves size comparison
When it comes to severe fouling scenarios, the XVG valve stands out as the top choice. Its specialized design allows it to effectively handle the most challenging fouling conditions while ensuring optimal performance. On the other hand, Sulzer's latest large opening fixed valve, the UFM-AF, offers a reliable solution for distillation tray applications that experience heavy fouling while still maintaining efficiency and capacity offered by smaller fixed valves. Both valves have their own unique strengths.
Extreme fouling systems often lead to costly losses in column performance and unit downtime; proper design is critical. Appropriately designed fouling resistant features can provide substantial increases in unit reliability even in the most difficult applications.
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