Planned outages commonly occur every two to five years, thus a refinery turnaround is a prime opportunity to replace column and separator internals with the newest available technology.
Planning for an outage with a "replacement-in-kind" strategy will address lost performance from refinery equipment due to normal wear and tear. Most column internals can be upgraded for higher capacity, more flexibility or greater efficiency at close to the same cost as in-kind equipment replacement.
Upgrade performance of existing packing or trays Sulzer MVG™ and UFM™ trays can achieve up to a 15-percent capacity increase in entrainment-limited applications. MVG and UFM trays fit within existing column weld-ins and ring supports for a similar cost to replace in-kind moveable valve trays. If increased liquid handling is required, the use of Z-bars can adapt the existing weld-ins for larger downcomers without the need for costly welding to the vessel wall. Standard structured packing can easily be replaced with high performance packings - MellapakPlus™ and Mellagrid™ - providing capacity increases up to 40 percent at a cost that is comparable to the existing equipment without requiring other column modifications.
Optimize stripping tray open area Column bottom, side column or hydrotreater product stripping trays are often a single design to simplify equipment layout and production. In operation, the bottom tray has a far lower vapor rate than the top tray, due to the stripping effect. Since the design will have to accommodate the highest loads, the bottom trays' performance will likely suffer, due to weeping. Because of this, stripping trays can often have an efficiency of 25 percent or less. By making a simple design change - reducing the open area on the lower trays appropriate to the predicted vapor rate - the refiner can see a large impact on stripping efficiency or can take advantage of the improved stripping by reducing energy/steam usage.
Upgrade separator internals Separators, accumulators, receivers and knockouts are often the forgotten vessels that can consume downstream capacity when operating with poor performance. Entrainment generation is typically exponential, so a small shortfall in separator capacity can result in a very large increase in liquid losses. Upgrading an existing standard mesh or demister pad with a higher capacity Sulzer KnitMesh™ Mist Eliminator or Mellachevron™ can reduce carryover of liquid or free water to downstream processes from existing separators that are forced to operate with a higher superficial velocity.
Improve tray fouling resistance Adding anti-fouling features to a replacement tray can be a simple fix to increase run-length between cleanings or turnarounds in heavy fouling services. Adjusting downcomer design and incorporating push valves on the active decks can improve the washing effect of the tray liquid traffic to prevent fouling buildup. These features can be incorporated into the trays without the need to weld on the column wall. Tower and vessel upgrades, rather than in-kind replacements, takes extra planning and strategy - but the payout is often high. Start early so you have time to evaluate, not only the tower internals, but also the feeds, draws, nozzles and auxiliary equipment. Sulzer Chemtech's process applications team can help evaluate all your possible options.
For more information, visit www.sulzer.com or call (281) 540-2555.
