Distillation is a major operation in most refinery processes; the internal components of distillation columns must maintain high efficiency and reliability during the entire run length period of four to six years.
A major challenge in refining columns is fouling resistance. Refinery streams have multiple fouling materials, such as salts, phosphorous products, catalyst fines, clay and coke that reduce column efficiency and capacity. The net consequences of fouling are reduction in refinery run lengths and processing capacity, higher energy consumption and/or additional stream processing.
Trays in fouling applications have distinctive features based upon the type of foulant encountered. A key factor for a successful design is understanding the foulant and the fouling process. There is not a single column internal design that can successfully work under various fouling conditions. Trays can have a variety of antifouling features like fixed valves, special weirs and downcomers. A common feature is fixed valves, rather than moving valves, which have the potential to stick in one position, so they are typically avoided in fouling applications.
In the 1960s, Sulzer, then Nutter Engineering, invented the trapezoidal fixed valve tray V-GridTM series, which became the standard for fouling applications like the hydrofluoric acid alkylation process. Fifty years later, Sulzer introduced the XVG™, a large, fixed V-Grid valve for extreme fouling applications. XVG trays have been successfully used in crude column top sections with salt deposition problems, delayed coker main fractionator wash sections and bitumen stripping.
Almost 40 years later, Sulzer introduced the UFM™, a trapezoidal floating valve that combined high efficiency and capacity. The shape of the UFM valve forces vapor to move downward toward the tray deck, creating better gas dispersion in the liquid. This improves the mass transfer between vapor and liquid (high efficiency), producing less liquid carryover with vapor (high capacity).
Sulzer combined the fouling resistant features of the V-Grid valves with the shape of the UFM to develop a new fixed valve UFM AF™. The valve has anti-fouling features — high lift, lateral vapor release and trapezoidal slot with high efficiency features — valve umbrella shape and trapezoidal valve.
The valves were tested, and results showed higher efficient capacity than Sulzer’s existing high performance mini MVG™ valves. The mechanical design of the UFM AF valve was rigorously tested during development, and commercial experience validates its strength and mechanical stability. The valves must remain in position during operation so that tray efficiency can be maintained throughout various operating conditions. Some other valves on the market have historically had problems with fixed valves popping out during operation, causing degradation in column performance.
The first trays equipped with UFM AF valves were successfully installed in the stripping section of a crude column more than five years ago. Today, there are more than 60 columns equipped with UFM AF trays in different refinery applications. All are operating well, meeting all expectations of high performance and fouling resistance.
For more information, visit sulzer.com or call (281) 540-2555.
